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| Citation |
- Permanent Link:
- https://ufdc.ufl.edu/UFE0019201/00001
Material Information
- Title:
- Investigating Archaeological Sites, Cemeteries, and Soils with Ground-Penetrating Radar in Florida
- Creator:
- CHILTON, CHRISTOPHER
- Copyright Date:
- 2008
Subjects
- Subjects / Keywords:
- Antennas ( jstor )
Archaeological sites ( jstor )
Cemeteries ( jstor )
Excavations ( jstor )
Graves ( jstor )
Radar ( jstor )
Sand ( jstor )
Silts ( jstor )
Soil horizons ( jstor )
Soils ( jstor )
City of Newberry ( local )
Record Information
- Source Institution:
- University of Florida
- Holding Location:
- University of Florida
- Rights Management:
- Copyright Christopher Chilton. Permission granted to University of Florida to digitize and display this item for non-profit research and educational purposes. Any reuse of this item in excess of fair use or other copyright exemptions requires permission of the copyright holder.
- Embargo Date:
- 7/12/2007
- Resource Identifier:
- 660034014 ( OCLC )
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INVESTIGATING ARCHAEOLOGICAL SITES, CEMETERIES AND SOILS, WITH
GROUND-PENETRATING RADAR INT FLORIDA
By
CHRISTOPHER CHILTON
A THESIS PRESENTED TO THE GRADUATE SCHOOL
OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT
OF THE REQUIREMENTS FOR THE DEGREE OF
MASTER OF SCIENCE
UNIVERSITY OF FLORIDA
2007
O 2007 Christopher Chilton
To my family: Jennifer, Richard, Elizabeth, Cynthia, Richard Jr. and Randall, and all my friends
who have helped through the years.
ACKNOWLEDGMENTS
This research could not have been completed without the advice, guidance and support
from numerous individuals. The integration of multiple disciplines required the assistance of
many friends, colleagues and mentors. Chiefly, I would like to express my gratitude for the vital
support, advice and input from my diverse committee. Dr. Mary Collins was essential to my
understanding and interest in soil science. Her passion for teaching helped create a remarkable
environment for learning and critical thinking. She was an inspiration for all of her students and I
will always appreciate the commitment she had in my education. Dr. James Davidson provided
unique insight and knowledge because of his archaeological expertise. His work on African-
American cemeteries allowed for a critical understanding of much of my research. I was most
fortunate to learn from him not only in the classroom, but in the field as well. Dr. John Schultz
provided valuable counseling and support for my research. His technical and practical
understanding of my work was a tremendous help and allowed me to work through difficult
problems. I was most fortunate to have a committee that provided valuable comments and
patience while writing this thesis.
The Department of Soil and Water Science at the University of Florida has fostered a great
environment for cooperative learning. Never have I seen so many professors and students who
are genuinely interested in each others work and who are willing to assist without reservation.
Dr. Willie Harris has been a wonderful mentor and a remarkable scientist who helped me as well
as many other students throughout his great career. My fellow graduate students who not only
shared an office, but much more, assisted me throughout my research. Dr. Larry 'Rex' Ellis,
Thomas Saunders and Kelly Fischler were instrumental in my graduate school development and
eagerly assisted me whenever needed. I would like to recognize those undergraduate students
who assisted me on many occasions: Victoria Gardner, Aja Stoppe and Leanna Woods. I would
also like to recognize Dr. Rocky Cao, Lisa Stanely and Genero Keehn at the Environmental
Pedology and Land Use Laboratory at the University of Florida for their assistance with my soil
analyses.
I would like to express my gratitude to the archaeological community that guided me
through many years of support and inspiration. Dr. Kathleen Deagan and Al Woods took me
from the basement of the Florida Museum of Natural History to the field. Their support guided
me to the wonderful people of Southeastern Archaeological Research Inc. The confidence and
opportunity afforded me by Dr. Anne Stokes and James Pochurek allowed for my archaeological
development for which I will always be grateful. Dr. Robert Austin, Dr. Elizabeth Carlson and
Dr. Deborah Mullins have not only had a great impact on my archaeological maturation but have
offered assistance and support for my research.
TABLE OF CONTENTS
page
ACKNOWLEDGMENTS .............. ...............4.....
LIST OF TABLES ............ ...... .__ ...............9....
LIST OF FIGURES .............. ...............12....
AB S TRAC T ............._. .......... ..............._ 15...
CHAPTER
1 INTRODUCTION ................. ...............17.......... ......
Tool s and Method ol ogy of GP R. ............_...... .............. 18..
GPR Antennas ............. .. ... ._ .............. 18....
Radar Propagation and Parameters ............. .. ... ...............21......
Properties and Materials Affecting Radar Propagation ......____ ........._ ..............22
History of GPR .............. .... ...._ .... .......__.. ...........2
Archaeological and Cemetery Application of GPR. ........___....... .._ .........___......25
History and Use of GPR Mapping in Archaeology and Cemeteries .............. ....................26
Soils of Florida ............. ...... ...............29...
Soil Taxonomy .............. ...............29....
Diagnostic Surface Horizons ........._..... ...._... ...............30....
Histic Epipedon ........._.._.. ...._... ...............3 1...
M ollic Epipedon ................. ...............32........ ......
Umbric Epipedon............... ...............32
Ochric Epipedon ........._..... ...._... ...............32.....
Diagnostic Subsurface Horizons .............. ...............32....
Albic Horizon .............. ...............33....
Argillic Horizon............... ...............33
Cambic Horizon............... ...............33
Spodic Horizon ........._..... ...._... ...............34.....
Soil Orders in Florida ........._.._.. ...._... ...............34...
A lfisol s .............. ...............34....
Entisols .............. ...............34....
Hi stosol s .............. ...............3 5....
Incepti sol s............._ ........ ...............35.....
M ollis ol s..............__....._.. ...............36..
Spodosol s............... ...............3
Ulti sol s .....__ ................. .........._.........3
Obj ectives of the Study ..............__.......... ...............37...
2 FIELD SITES .............. ...............38....
Study Site Selection .....__ ................. ........._._.........3
Newberry Cemetery ................. ...............38.................
Description .............. ...............38....
S oil s ................. ...............3.. 9..............
Cultural History ................. ...............41.......... .....
Oakland Cemetery Site ................. ...............43........... ....
Description .............. ...............43....
S oil s ................. ...............43.......... .....
Cultural History ................. ...............45.......... .....
Historic Archaeological Site ................. ...............46................
Description .............. ...............46....
S oil s ................. ...............46.......... .....
Cultural History ................. ...............48.......... ......
Prehistoric Archaeological Site .............. ...............49....
Description .............. ...............49....
S oil s ................. ...............50.......... .....
Cultural History ................. ...............51.......... .....
3 MATERIALS AND METHODS .............. ...............53....
Site Criteria............... ...............53
Soil Sampling............... ...............54
Soil Analyses .............. ...............55....
Physical Analysis............... ...............56
Chemical Analysis............... ...............56
Statistical Analysis............... ...............57
GPR Data Collection .............. ...............57....
GPR Analysis................ .... ............5
GPR Post-Processing Analysis............... ...............59
Study Sites .............. ...............60...
Newberry Cemetery............... ...............60
Oakland Cemetery ................. ...............61.......... .....
Historic Archaeological Site............... ...............63..
Prehistoric Archaeological Site .............. ...............64....
4 RE SULT S .............. ...............65....
Newberry Cemetery ................. ...............65.......... ......
S oil Phy si cal Analy si s ................. ...............65................
Soil Chemical Analysis ................ ...............67..
GPR-Soil Results for Newberry Cemetery ................. ...............70...............
The 500-MHz antenna............... ...............70
The 900-MHz antenna............... ...............73
Oakland Cemetery .............. ...............77....
S oil Phy si cal Analy si s ............__..... ___ ...............77...
Soil Chemical Analysis ............... .. ...............78..
GPR-Soil Results for Oakland Cemetery ................. ...............81......__ ...
The 500-MHz antenna............... ...............8 1
The 900-1VHz antenna............... ...............83
Prehistoric Archeological Site .............. ...............84....
S oil Phy si cal Analy si s ............_...... ._ ............... 5....
Chemical Analysis.................... .... ...................8
GPR-Soil Results for the Prehistoric Archaeological Site .............. .....................8
The 500-1VHz antenna............... ...............89
The 900-1VHz antenna............... ...............93
Historic Archeological Site............... ...............95..
Soil Physical Analysis ............_...... ._ ...............95...
Soil Chemical Analysis .............. .............. ................9
GPR-Soil Results for the Historic Archaeological Site ......____ ..... ...__ ..............99
The 500-1VHz antenna............... ...............99
The 900-1VHz antenna............... ...............102
Summary ............ ..... .._ ...............105...
5 DI SCUS SSION ............ ..... ..__ ............... 106..
Newberry Cemetery ................. ...............107......... ......
Oakland Cemetery ................. ...............110......... ......
Historic Archaeological Site ................. ...............113................
Prehistoric Archaeological Site ................. ...............117...............
Ground-Penetrating Radar Comparisons ................. ...............120................
GPR-Cemetery .............. ...............120....
GPR-Archaeological Sites............... ...............121.
Sum mary ................. ...............122......... ......
6 CONCLUSIONS .............. ...............128....
APPENDIX
A SOIL DESCRIPTIONS .............. ...............132....
B PARTICLE-SIZE ANALY SI S ............... ...............14
C SOIL CHEMICAL ANALYSES ................. ...............144...............
D GPR PROFILE S ............ ..... .__ ...............149..
E STATISTICS .............. ...............153....
LIST OF REFERENCES ............ ......__ ...............157...
BIOGRAPHICAL SKETCH ............_...... ...............164...
LIST OF TABLES
Table page
1-1 Typical relative dielectric permittivities (RDPs) of common materials. ...........................24
1-2 Diagnostic summary of the four epipedons used to classify soils in Florida. ................... .3 1
1-3 Cation exchange capacities (CEC) of soil materials (Birkeland 1999). ................... .........31
2-1 Graves at the Newberry Cemetery. Preliminary Report, Southeastern Archaeological
Research, Inc. Gainesville, Florida. .............. ...............42....
3-1 Data points for the four corners of the cemetery boundary. The proj section system
used was UTM, NAD 1983, Zone 17 North. ......___. .... ... ._ ...............61
3-2 Data points for the four corners of the cemetery boundary. The proj section system
used was UTM, NAD 1983, Zone 17 North. ......___. .... ... ._ ...............63
3-3 Data points for the four corners of the historic archaeological survey area. The
proj section system used was UTM, NAD 1983, Zone 17 North. .............. ................64
4-1 Selected soil chemical analysis of the Newberry Cemetery natural and anthropogenic
soils along transects 14 and 17. The EC (EC), extractable (Ext.),............... ................6
4-2 Selected values of chemical properties of the Oakland Cemetery natural and
anthropogenic soils along transect 2. The EC (EC), extractable (Ext.), ................... .........81
4-3 Selected values of chemical properties from natural and anthropogenic soils at
prehistoric archaeological site. The EC (EC), extractable (Ext.),............... .................8
5-1 Coordinate positions of the Newberry cemetery of selected transects and location of
graves. ................ ...............110..._ __.......
A-1 Official description of Jonesville soil series in Alachua County, Florida. ................... ...132
A-2 Soil description of Jonesville series at the Newberry gravesite natural soils (NGNS)....133
A-3 Official description of Candler soil series in Orange County, Florida. ........................... 134
A-4 Soil description of Candler series at the Oakland gravesite natural soils (OGNS),
Orange County, Florida. ............. ...............135....
A-5 Official description of Orlando soil series in Lake County, Florida. .............. ..... ........._.136
A-6 Soil description of Orlando series at the prehistoric archaeological natural soils
(PANS)................. ..............13
A-7 Official description of Immokalee soil series in St. Johns County, Florida. ................... 138
A-8 Soil description of Immokalee series at the historic archaeological natural soils
(H AN S). .............. ...............139....
B-1 Soil data from the Newberry Cemetery Anthropogenic Soils (NCAS) and the
Newberry Cemetery Natural Soils (NCNS) ................. ...............140........... ...
B-2 Soil data from the Oakland Cemetery Anthropogenic Soils (OCAS) and the Oakland
Cemetery Natural Soils (OCNS)............... ...............141
B-3 Soil data from the Prehistoric Archaeological Anthropogenic Soils (PAAS) and the
Prehistoric Archaeological Natural Soils (PANS) ................. ................ ......... .142
B-4 Soil data from the Historic Archaeological Anthropogenic Soils (HAAS) and the
Historic Archaeological Natural Soils (HANS) ................. .............. ......... .....143
C-1 Soil data for the Newberry Cemetery Anthropogenic Soils (NCAS) from selected
transects. Extractable (Ext.). NCAS Transect 22 15N/21E ........._._..... ....._.._. .......144
C-2 Soil data for the Newberry Cemetery Anthropogenic Soils (NCAS) from selected
transects. Extractable (Ext.). NCAS Transect 14 5N/13E ................. ......................144
C-3 Soil data for the Newberry Cemetery Anthropogenic Soils (NCAS) from selected
transects. Extractable (Ext.). NCAS Transect 10 8N/9E ................. ........___..........144
C-4 Soil data for the Newberry Cemetery Anthropogenic Soils (NCAS) from selected
transects. Extractable (Ext.). NCAS Transect 14 9N/13E ................. ......................145
C-5 Soil data for the Oakland Cemetery Anthropogenic Soils (OCAS) from selected
transects. Extractable (Ext.). OCAS Transect 9 40N/10E ................. ............ .........145
C-6 Soil data for the Oakland Cemetery Anthropogenic Soils (OCAS) from selected
transects. Extractable (Ext.). OCAS Transect 22 40N/54W ................. .....................145
C-7 Soil data for the Oakland Cemetery Anthropogenic Soils (OCAS) from selected
transects. Extractable (Ext.). OCAS Transect 22 14N/52W ................. .....................146
C-8 Soil data for the Prehistoric Archaeological Anthropogenic Soils (PAAS) from
selected transects. Extractable (Ext.). PAAS Transect 2 2N/1E............... .................14
C-9 Soil data for the Historic Archaeological Anthropogenic Soils (HAAS) from
selected transects. Extractable (Ext.). HAAS Test Unit 17, Transect 1 52N/44E ...........146
C-10 Soil data for the Historic Archaeological Anthropogenic Soils (HAAS) from selected
transects. Extractable (Ext.). HAAS Test Unit 17, Transect 1 50N/44E ................... ......146
C-11 Soil data for the Historic Archaeological Anthropogenic Soils (HAAS) from selected
transects. Extractable (Ext.). HAAS Test Unit 17, Transect 3 52N/46E ................... ......147
C-12 Soil data for the Historic Archaeological Anthropogenic Soils (HAAS) from selected
transects. Extractable (Ext.). HAAS Test Unit 17, Transect 3 51N/46E ................... ......147
C-13 Soil data for the Historic Archaeological Anthropogenic Soils (HAAS) from selected
transects. Extractable (Ext.). HAAS Test Unit 17, Transect 3 50N/46E ................... ......147
C-14 Soil data for the Historic Archaeological Anthropogenic Soils (HAAS) from selected
transects. Extractable (Ext.). HAAS Test Unit 18, Transect 8 50N/40E ................... ......147
C-15 Soil data for the Historic Archaeological Anthropogenic Soils (HAAS) from selected
transects. Extractable (Ext.). HAAS Test Unit 18, Transect 8 52N/40E ................... ......147
C-16 Soil data for the Historic Archaeological Natural Soils (HANS) from selected
transects. Extractable (Ext.). HANS, Transect 12 48N/30E ................. .....................148
C-17 Soil data for the Historic Archaeological Natural Soils (HANS) from selected
transects. Extractable (Ext.). HANS, Transect 14 40N/20E ........._.._.... ......_.._. ......148
E-1 Results of t-tests for Newberry Cemetery natural soils (NCNS) and Newberry
Cemetery .........._ _.......__ ...............153...
E-2 Results of t-tests for Oakland Cemetery natural soils (OCNS) and Oakland Cemetery .154
E-3 Results of t-tests for Prehistoric archaeological natural soils (PANS) and Prehistoric
archaeological anthropogenic soils (PAAS) samples ................. .......... ...............155
E-4 Results of t-tests for Historic archaeological soils (HANS) and Historic
archaeological anthropogenic soil (HAAS) samples. ............. ...............156....
LIST OF FIGURES
Figure page
1-1 Scale of relative depth of penetration to resolution for ground-penetrating radar
antennas............... ...............20
1-2 A schematic of reflected and scattered electromagnetic waves as they are transmitted
through differing soil properties.. ............ ...............21.....
2-1 Location of research sites in Alachua County, Lake County, St. Johns County, and
Orange County, Florida. ............. ...............39.....
2-2 Soil survey map showing soil series and complex at the Newberry cemetery .. ............... .40
2-3 Soil depth to limerock variability of an Alfisol in Alachua County, Florida. ...................41
2-4 Soil survey map showing the Candler-Apopka soil complex at the Oakland cemetery....44
2-5 Photograph of an Entisol profile in Florida. ............. ...............45.....
2-6 Soil survey map showing soil series and complex at the historic archaeological site.......47
2-7 Photograph of an Immokalee soil series profile. ............. ...............48.....
2-8 Photograph of an excavation at the prehistoric archaeological site along the
southwest shore of Lake Apopka, Montverde, Florida ......... ................. ...............50
2-9 Aerial photograph (1999) of the prehistoric archeological site at Monteverde
showing shovel tests and test unit location (Austin 2006)............... ...............51.
3-1 Aerial photograph of Oakland Cemetery from 1947. Site boundary is highlighted in
red. ............. ...............62.....
4-1 Depth distribution of total clay content of natural transectt 17) and anthropogenic
transectt 14) soils at the Newberry cemetery............... ...............66
4-2 Depth distribution of Transect 14 pH values and Transect 17 pH values at the
Newberry cemetery ................. ...............67.......... ......
4-3 Ground-penetrating radar profiles of the Arenic Hapludalf using a 500-MHz antenna
along transect 17 .............. ...............72....
4-4 Ground-penetrating radar profiles of anthropogenic altered Arenic Hapludalf ................73
4-5 Ground-penetrating radar profile of anthropogenic altered Arenic Hapludalf .................74
4-6 Ground-penetrating radar profile of natural Arenic Hapludalf using the 900-MHz
antenna along transect 17............... ...............75...
4-7 Ground-penetrating radar profile of anthropogenic Arenic Hapludalf using a 900-
MHz antenna along transect 14............... ...............76...
4-8 Depth distribution of pH values for Transect 2 at the Oakland cemetery. ......................79
4-9 Ground-penetrating radar profile using the 500-MHz antenna with two suspect
graves from a Lamellic Quartzipsamment. ................ ....................................83
4-10 Ground-penetrating radar profile using the 900-MHz antenna of two suspect graves
in a Lamellic Quartzipsamment ................. ...............85................
4-11 Depth distribution of pH values for transects at the prehistoric archeological site. ..........87
4-12 Ground-penetrating radar profiles of a natural Psammentic Dsystrudepts using the
500-M Hz antenna. ........... ..... .._ ...............91....
4-13 Ground-penetrating radar profiles of an anthropogenic Psammentic Dsystrudepts
using the 500-MHz antenna. ........... ..... .._ ...............92...
4-15 Ground-penetrating radar profiles of an anthropogenic Psammentic Dsystrudepts
using the 900-MHz antenna. .............. ...............94....
4-16 Depth distribution of selected pH values for transects at historic archaeological site.
Historic site data did not exceed 0.50 m. ............. ...............97.....
4-17 Ground penetrating radar profiles of a natural Arenic Alaquodos using the 500 MHz
antenna.. ............ ...........10
4-18 Ground-penetrating radar profiles of an anthropogenic Arenic Alaquods using the
500-M Hz antenna. ........... ..... .._ ...............102...
4-19 Ground-penetrating radar profiles of a PANS using the 900-MHz antenna. A)
Background filter is applied and antenna noise is removed. ............. .....................0
4-20 Ground-penetrating radar profiles of a historic archaeological anthropogenic soil
using the 900-MHz antenna. ........... ..... .._ ...............104..
5-1 Example of a root ball inversion caused by severe weather in Newberry cemetery
area. ........... ..... ._ ...............109...
5-2 GPR profile at Newberry cemetery of transect 22 using 500-MHz antenna. Grave is
outlined demonstrating how a vertical feature produces scattering. .............. ..............110
5-3 Photograph of excavation unit from the historical archaeological site. Wall footer/
trench is located in southwest corner of unit. ................ .......... ............. .....15
5-4 Ground-penetrating radar profile (GPR) of the prehistoric archaeological natural soil
(PANS) using the 900-MHz antenna. ....__ ......_____ ......___ ............1
5-5 Photograph of soil in abandoned excavation unit from the prehistoric archaeological
site.. ............ ..........11
5-6 Ground-penetrating radar profile using 500-MHz antenna from the Newberry
cemetery anthropogenic soils (NCAS). ............. ...............124....
D-1 Ground-penetrating radar (GPR) transect 22 of the Newberry Cemetery
Anthropogenic Soils (NCAS) using 500-MHz antenna .........__ ...... ...__ ............149
D-2 Ground-penetrating radar (GPR) transect 22 of the Newberry Cemetery
Anthropogenic Soils (NCAS) using 500-MHz antenna .........__ ...... ...__ ............149
D-3 Ground-penetrating radar (GPR) transect 4 of the Oakland Cemetery anthropogenic
Soils (OCAS) using 500-MHz antenna. ....__ ......_____ .......__ ...........15
D-4 Ground-penetrating radar (GPR) transect 4 of the Oakland Cemetery Anthropogenic
Soils (OCAS) using 500-MHz antenna. ....__ ......_____ .......__ ...........15
D-5 Ground-penetrating radar (GPR) transect 4 of the Oakland Cemetery Anthropogenic
Soils (OCAS) using 500-MHz antenna. ....__ ......_____ .......__ ...........15
D-6 Ground-penetrating radar (GPR) transect 2 of the Prehistoric Archaeological
Anthropogenic Soils (PAAS) using 500-MHz antenna...................... ...............15
D-7 Ground-penetrating radar (GPR) transect 2 of the Prehistoric Archaeological
Anthropogenic Soils (PAAS) using 500-MHz antenna .....................151
D-8 Ground-penetrating radar (GPR) transect 2 of the Prehistoric
ArchaeologicalAnthropogenic Soils (PAAS). ............. ...............15 1....
D-9 Ground-penetrating radar (GPR) transect 3 of the Historic
ArchaeologicalAnthropogenic Soils (HAAS) using 500-MHz antenna. .......................152
D-10 Ground-penetrating radar (GPR) transect 3 of the Historic Archaeological
Anthropogenic Soils (HAAS) using 500-MHz antenna. ......._____ .... ..__ ............152
D-11 Ground-penetrating radar (GPR) transect 3 of the Historic Archaeological
Anthropogenic Soils (HAAS) using 500-MHz antenna. ............. ....................15
Abstract of Thesis Presented to the Graduate School
of the University of Florida in Partial Fulfillment of the
Requirements for the Degree of Master of Science
INVESTIGATING ARCHAEOLOGICAL SITES, CEMETERIES AND SOILS WITH
GROUND-PENETRATING RADAR INT FLORIDA
By
Christopher Chilton
May 2007
Chair: Mary E. Collins
Major: Soil and Water Science
Ground-penetrating radar (GPR) is an efficient and nondestructive instrument for
collecting information below the ground surface relating to potential archaeological sites and
cemeteries. This research assessed the application of GPR technologies for archaeological
investigations with multiple soil orders of Florida. By differentiating the archaeological anomaly
from natural pedogenic properties, a qualitative interpretation of a site can determined. Four sites
were selected based upon archaeological context and soil properties in Florida. The
anthropogenic sites included two cemeteries; the Newberry cemetery located in Alachua County
and the Old African American Cemetery in Orange County. The one historic archaeological site
is located in St. Johns County and a prehistoric archaeological site is in Lake County. Each site
had a different soil order commonly encountered in Florida (Alfisols, Entisols, Inceptisols and
Spodosols). Natural and anthropogenic soils were surveyed using 900-and 500-MHz antennae.
Soil samples were collected along GPR surveyed transects and analyzed for physical and
chemical properties including texture, pH, and electrical conductivity. Post-processing of the
GPR data was conducted to augment profile interpretation and assess the differences in imagery
of the 900- and 500-MHz antennae.
Results of the GPR and soil analyses revealed that each was dependent upon the
anthropogenic context. Diagnostic horizons had a greater influence than soil order classification
on the successful application of GPR on archaeological sites and cemeteries. Soil physical
properties, specifically texture, had a greater overall impact than soil chemical properties on the
radar propagation in every site. The 500-MHz antenna was preferred over the 900-MHz antenna
for general performance in all four research sites, regardless of soil order. 500-MHz antenna
preference for the GPR was based on depth of radar wave penetration and the general
background noise associated with the higher frequency antenna. Though diagnostic surface
horizons and soil texture influenced GPR interpretation, this study showed that GPR is
applicable in a wide variety of soil and archaeological contexts in Florida.
CHAPTER 1
INTTRODUCTION
Ground-penetrating radar (GPR) has become a comprehensive and reliable remote sensing
tool for gathering and processing geophysical information. GPR is a method that provides rapid
and non-invasive identification of subsurface features and materials. Recent technological
innovations, such as real time video display with post processing software on the control unit,
have improved the effectiveness of data acquisition and processing along with increasing the use
and application of this tool. The technological advances in GPR in the past decades have allowed
its use today to become common and accepted procedures in many disciplines.
Many land-use activities have the potential for the application of GPR. Numerous
scientific and commercial fields such as: geology, mining, engineering, construction, agriculture,
environmental science and archaeology are turning to real-time and nondestructive data
acquisition tool. Also, because of the easy and rapid use of this instrument, there has been an
increase in the utilization for surveying, mapping, mitigating and delineating subsurface features.
Soil scientists and geologists have used GPR to map subsurface horizons, delineate karst
features, detect sinkhole formation, and differentiate bedrock units for industrial minerals
(Doolittle and Collins 1998, Collins 1990, Puckett 1990, and Dekeyser 2005). The military is
able to save lives by detecting buried land mines and unexploded ordinance (Hyde 1997).
Engineers have applied this efficient technology to high-speed rail trackbed investigations
associated with high-speed trains (Doshi and Al-Nuaimy 2006). GPR was used in May 2005 for
a search mission after a mountain accident in the Chilean Andes involving the death of 45
military troops (Casassa 2006). The success of GPR in the past has created strategies for the
future; scientists are planning to conduct geophysical surveys on Mars (Olhoeft 1998).
Tools and Methodology of GPR
GPR is a method that is able to produce large amounts of high resolution, multi-
dimensional information through the transmission of electromagnetic waves. This tool actively
produces multiple pulses of energy derived from a control unit. Fiber-optic cables transmit a
digital signal to and from the antennas; the raw data derived from the generated electrical pulses
are received and displayed in a video or printed format (Conyers and Goodman 1997, Davis and
Annan 1989, and Schultz 2003). The transmission of electromagnetic radar pulses travel through
the earth's surface and any of these pulses which are reflected will be received and recorded.
Energy is transmitted and energy is received through antennas; the frequencies of these antennas
range from a bandwidth of about 10 megahertz (1VHz) to 1500 1VHz.
GPR Antennas
Transmitting and receiving antennas used for GPR are configured in either a monostatic or
bistatic mode. The monostatic mode is where the transmitting and receiving antennas is at a zero-
offset, there is no separation from the point of transmission to the point of reception. This allows
for a self-contained unit with less variability. On the contrary, the bistatic mode has two separate
points for transmission and reception of radar energy. Separation of these independent points can
be manipulated in the field to determine radar wave velocity. The recorded time of transmission
from one antenna to another through a known distance of material can be measured and thereby
calculate the radar wave velocity (Conyers and Goodman 1997). Configuration choices for GPR
antennas may be based on the type of field questions asked.
Different GPR applications demand different antennas. The choice for standard
transmitting antennas is generally straightforward, the dipole or bowtie traveling-wave antenna
have been primarily used for the impulse-based radar system (Daniels 1996). The transmitting
antenna emits an elliptical cone of radar energy with the apex of the cone located in the center of
the antenna (Davis and Annan 1989, Schultz 2003). The elongated shape of the elliptical is
usually parallel to the direction of the antenna movement along the ground (Conyers 2004,
Conyers and Goodman 1997). This shape of transmitted radar energy plays a role in survey
parameters. The size and shape of the transmission cone is primarily dependent upon the
physical properties of the soil, thereby dictating the spatial parameters of collecting data in the
field.
Some antennas have an added feature that allow for a reference mark to be employed
during a survey. This mark is activated when a trigger switch is pushed on the antenna handle by
the operator, allowing for a spatially referenced point along a GPR transect. Marked points on
the radar transect are coordinated with field grid markers that can be located using a global
positioning system (GPS) to create a three-dimensional reference points (Conyers 2004, Conyers
and Goodman 1997, Tischler 2003).
Techniques for GPR vary widely, each according to their application. There are restrictions
to the range of the operating system. Selections of antennas are based on the depth and resolution
for area of study (Davis and Annan 1989). Figure 1-1 illustrates the commercial range of antenna
frequencies and properties. Higher frequency antennas (e.g. 900 MHz) offer a greater ability to
differentiate features of varying size from a surrounding matrix, but are limited in depth of
penetration. Conversely, the lower frequency antennas (e.g. 120 MHz) allow for greater depth at
which a GPR signal will be reflected back to the surface, but provide a lower range of resolution.
Any radar frequency used will be determined upon not only by the depth of study and the
subsurface features of that study, but upon the inherent properties of site area.
Antenna Frequency Properties Blu' = Pcso~lullan
Red = Depin
700 mHz
600 mHz
Figure 1-1. Scale of relative depth of penetration to resolution for ground-penetrating radar
antennas. Resolution capability is inversely proportional to depth of penetration.
(From Tischler, 2003. Integrating Ground-Penetrating Radar, Geographic Information
Systems and Global Positioning Systems for Three- Dimensional Soil Modeling).
The type of antenna frequency used is limited by the properties of the material that is
surveyed. A receiver bandwidth in excess of 500 MHz, and typically 1 GHz, is required to
provide a typical resolution of between 5 and 20 cm, depending on the relative properties of the
soil (Daniels 1996). Antennas used in most archaeological contexts are the 500-MHz and 900-
MHz antennas; while lower frequency antennas are often used to interpret the geomorphology of
many prehistoric sites. Equipment choice can be a compromise between resolution, scope of
signal processing, and the ability to effectively offset the negligible properties of subsurface
material. Frequency selection is dependent upon site parameters and survey obj ectives. Annan
and Cosway (1994) listed a number of factors controlling frequency selection: (i) electrical
properties of the host environment, (ii) depth resolution, (iii) clutter dimension, (iv) depth of
exploration and target size, (v) site access and (vi) any external interference.
Radar Propagation and Parameters
The effectiveness of the radar is dependent upon the ground in which it penetrates;
specifically the properties beneath the surface. GPR has been used to investigate ice, water, rock,
pavement, soil and many other natural and human environments (Olhoeft 1996). The success of
these numerous applications has all been based on the ability of the transmission of
electromagnetic waves.
ORGANIC
MATTER ANTENNA
GROUND SURFACE
!! SAND
:i CLAY
BE DROC K
Figure 1-2. A schematic of reflected and scattered electromagnetic waves as they are transmitted
through differing soil properties. Antenna displayed is a monostatic system with both
a transmitter (Tx) and receiver (Rx). (From Schultz, 2003. Detecting Buried Remains
in Florida Using Ground-Penetrating Radar. Doctoral Thesis in Forensic
Anthropology, University of Florida, p.28, Figure 4).
The physical properties that affect the radar waves as they pass through a medium are electrical
conductivity and magnetic permeability (Annan et al. 1975). Radar pulses generate a wavefront
which propagates downward and is partially reflected by any change in the electrical bulk
properties of the soil (Figure 1-2) (Vaughan 1986), GPR measures the changes in these
properties. Any of the electromagnetic energy that is reflected because of changes in these
properties is amplified and recorded through the receiving antenna.
Use of GPR requires the system operator to accurately understand the constraints of the
study area. Two factors must be determined prior to the operation of the equipment: the dielectric
constant and the range. Accurate configuration of the system will determine the proper depth of
signal penetration and resolution of that signal. Both range and dielectric constant are system
parameters that are set individually, but are dependent upon one another. An accurate range
cannot be set without a general knowledge of the subsurface dielectric constant.
The range is a parameter that has a time value measured in nanoseconds (ns.) A range
value is entered into the GPR control unit in order to determine how long to record received
signals after a radar pulse has been transmitted (Geophysical Survey Systems Inc. 1994). Any
portion of the radar pulse which can penetrate into the subsurface material, reflect from a
boundary or obj ect and return to the antenna is recorded and displayed in real-time. As time is
increased for the range setting, radar waves will penetrate the subsurface further in depth, yet
resolution and reflected data decrease with depth. There are finite restrictions to range settings
and the distance for which radar waves will travel. The time (ns) for a pulse to reach an obj ect or
boundary is dependent upon the material through which it passes. Restrictions to the range are
reliant upon frequency of the antenna and the dielectric constant.
Properties and Materials Affecting Radar Propagation
Electromagnetic pulses that are transmitted from the GPR antenna pass through space. If
this space is in a vacuum, then an electromagnetic pulse will travel at 0.2999 meters per
nanosecond. However, GPR is used over the ground and the materials located beneath the
surface range from soil, rock, ice, water and air to anthropogenic remains. Materials in the earth
have a range of dielectric properties which allow the passage of electromagnetic energy. The
more electrical conductivity a given material has the less dielectric it is; therefore for maximum
radar-energy penetration, a highly dielectric medium with a low electrical conductivity is
required (Conyers and Goodman 1997).
The dielectric constant is a parameter required in the calibration for the maximum effective
depth of the GPR energy waves. This constant, also known as the relative dielectric permittivity
(RDP), is measured against the heterogeneity of an obj ect or earth' s natural subsurface system.
The RDP is the capacity of a material to store, and then allow the passage of electromagnetic
energy (von Hippel 1954). Dielectric characteristics of materials vary greatly. Calculation and
measurement of RDP is based on of the velocity of an electromagnetic pulse in a vacuum. When
a pulse travels in a vacuum at 0.2998 meters per nanosecond then the RDP is 1 (Conyers and
Goodman 1997). Materials with a low dielectric constant, allow the passage of electromagnetic
waves with little or no dissipation, while higher conductivity will create greater dissipation of
radar waves or attenuation.
Soil and consolidated earthen material are both filters and boundaries to radar waves,
depending upon the dielectric properties of the medium. Dielectric constant values range from air
(low), to sea water (high) and vary according to the properties associated with subsurface
materials (Table 1-1), (Davis and Annan 1989, Geophysical Survey Systems Inc. 1994).
Materials composed primarily of air are less electrically conductive and are termed to be less
dielectric. Conversely, the RDP of water is of the order of 80, therefore even small amounts of
moisture will cause a significant increase of the relative permittivity of material (Daniels 1996).
Table 1-1. Typical relative dielectric permittivities (RDPs) of common materials.
Material RDP
Air 1
Dysand 3-5
Limestone 4-8
Clay 5-40
Concrete 6
Dysandy coastal land 10
Average organic-rich surface soil 12
Marsh or forested land 12
Organic-rich agricultural land 15
Saturated sand 20-30
Fresh water 80
Sea water 81-88
Modified from Davis and Annan (1989) and Geophysical Survey Systems, Inc. (1987).
History of GPR
GPR has a history that was a precursor to its own rediscovery. The first practical
application of GPR was in 1929 by W. Stern for determining the depth of an Austrian glacier
(Olhoeft 1996). The United States Air Force developed better radar systems in the late 1950's
when several pilots crashed on icy runways because conventional radar was transmitting through
the ice and reading inaccurate altitudes. In 1960, John Cook made the first proposal for the
detection of subsurface reflections using radar in his article "Proposed monocycle-pulse, VHF
radar for airborne ice and snow measurements." From this work, the development of radar
systems to detect subsurface reflections continued. The subsurface radar system from the late
1920's had not changed all that much when used for the Apollo 17 lunar mission in 1972. The
need for alternative applications by the U.S. military during the Vietnam War created an increase
in GPR development and advancement, hence the redundant use of acronyms. Radar is an
acronym for Radio Detection and Ranging.
Commercial availability for GPR technology was introduced in 1972 by Geophysical
Survey Systems Inc. (GSSI), ushering in a myriad of applications and extensive research to
universities and private companies alike. GPR development increased during the 1970's; Moffatt
and Puskar (1976) improved the target-to-clutter ratio of antennas and thereby increased
subsurface reflection accuracy. With increased antenna capability, new methods were able to
estimate the location of mines, faults and underground tunnels (Cook 1975, Moffatt and Puskar
1976). GPR technology in the early 1980's was used as a pedologic tool (Collins 1992, Doolittle
1982) and to investigate the depth of groundwater (van Overmeeren 1994). GPR has been used
to map bedrock surfaces, detect sinkholes and delineate karst features (Collins et al., 1990,
Doolittle and Collins 1998, Puckett 1990). As advancements in technologies emerged during the
1980's, methods of processing and analyzing GPR data became more widespread and available
to a variety of scientific Helds. This increase in available GPR technology created many diverse
applications.
Archaeological and Cemetery Application of GPR
The Hield of archaeology has long relied upon the use of multiple scientific disciplines,
ranging from geology to zoology. Techniques and tools from these other areas of studies have
worked well in shaping the way archaeologists conduct their research. In the past three decades,
the use of GPR has provided a means for analyzing an archaeological site in a nondestructive
way. GPR is a tool that increases the spatial extent of a study area, while reducing the amount of
time to conduct a preliminary survey. Data is collected in real-time and conveyed to the operator
allowing for rapid reconnaissance.
Archaeologists often destroy the area they study through excavation. GPR nondestructively
records and saves all data that are collected, thereby allowing decisions to be made prior to
disturbing a site. The capability of GPR to estimate depth and shape of buried obj ects make its
use suitable to grave detection (Bevan 1991). Varying site characteristics and context are also
amenable to the use of radar. To determine whether artifacts were present in a site often required
a great deal of exploratory digging, thereby greatly increasing time and expense (Vaughan
1986). Field season at an archaeological site is usually short and successes are often dependent
upon many variables including equipment, personnel and weather. Surveys conducted with GPR
may narrow the scope of interest and reduce the labor-intensive process associated with
excavation.
History and Use of GPR Mapping in Archaeology and Cemeteries
The increased success of GPR in archaeology has been related to the various circumstances
in which the technology is used. Advances in techniques have created greater interpretation of
data. Until recently, GPR was simply used to identify subsurface "anomalies" that may not have
represented archaeological features (Conyers and Cameron 1998). Fast and accurate
archaeological surveying of large areas using GPR has even created new word usage.
Geophysical 'prospection' is now considered a standard method for detecting buried
archaeological features and structures (Leckebusch 2003). No matter the terminology, GPR has
become recognized as an important tool for numerous archaeological applications.
The archaeological applications of GPR range from spatial parameters to temporal context.
Spatially, surveys are able to locate sites and delineate anthropogenic boundaries, while
superposition can be conveyed through stratigraphic sequencing and the mapping of features
(Dalan and Bevan 2002, Conyers 1995, Conyers and Goodman 1997, Sassaman et al. 2003,
Schultz 2003). The absence or presence of soil heterogeneity may also indicate an anthropogenic
site. This is contextual and site specific. A GPR survey of a possible prehistoric mound from the
Effigy Mounds National Monument in Iowa revealed symmetrical curving strata more consistent
with a prehistoric cultural mound than caused by natural phenomena (Whittaker and Storey,
2005). Reinterpretation and nondestructive analyses of the mounds has continued for the past 40
years. Whittaker and Storey (2005) affirm the potential of GPR for archaeological preservation
with ongoing research at Effigy Mounds National Monument. Sufficient knowledge of local
landforms and processes may allow a determination of earthen features (Dalan and Bevan,
2002). When taken in context to surrounding geomorphology, sequencing and uniformity in
radar profiles may suggest possible human augmentation.
GPR use can incorporate surface anomalies with subsurface uniformity. Discontinuities
between cultural features with the natural soil matrix extend spatial parameters for delineating
the lateral extent and thickness of shell middens (Chadwick and Madsen 2000). Near surface
lithological features create discrete anomalous characteristics. Such highlighted features may
expose potential voids beneath such as gravestone chambers (Lorenzo and Arias 2005). GPR in
archaeology not only highlights discontinuities within the soil, but reveals materials and obj ects
anomalous to a known area.
The successful use of GPR for locating historic graves has ranged widely, often with
varying results in the same site area. Intrasite soil conditions and burial practices may vary,
enabling clear and distinct reflections or attenuation. Even with mixed success, GPR is
considered the most reliable geophysical tool for locating graves. A model study by Bevan
(1991) was conducted at nine different sites in the United States that used both GPR. One study
site, the Poor Farm Cemetery in Rockville, Maryland, had no marked graves. Radar reflections at
this site exhibited grave features; however, excavation showed the reflection to be a natural
change in the soil. The study Bevan (1991) conducted at the different sites illustrated the varying
degree of success with GPR on cemetery graves.
Controlled archaeological and forensic tests have been conducted to establish the efficacy
of GPR. Schultz (2003) tested the applicability of GPR to detect buried bodies in two different
Florida soils. Pig cadavers, with varying weights and sizes, were selected as surrogates for
human bodies and buried at two depths. Factors that controlled decomposition were monitored
and assessed with the GPR. Schultz (2003) concluded that depth and time were the most
significant factors in the decomposition of the cadavers.
Another controlled test conducted with GPR was a simulated archaeological site in Illinois.
This study replicated features present in some North American archaeological sites under a
controlled environment (Hildebrand et al. 2002). Features included pig and dog burials in
mounds, isolated pits, hearths, artifact clusters and structures. In addition to the GPR, seismic
reflection imaging (SRI) was used. This allowed the authors to compare geophysical methods
based on reflection imaging in anthropogenic soil conditions. Both methods worked well in the
study with the GPR providing a more accurate depth range to target (Hildebrand et al. 2002).
A combination of pedological insight with the use of GPR allows for comprehensive site
analysis. Distinct change in soil structure or bulk density may enable a GPR operator to
distinguish cultural augmentation from natural occurrences. Surficial features, such as circular
trample zones associated with animal feeding areas, were identified with time-slice depth maps
created by processed radar data (Nishimura and Goodman 2000). A 300-MHz antenna was
chosen for a Roman period site in Wroxeter, England as a consequence of anticipated depth of
stratigraphy. This approach in data acquisition increases opportunity in locating site specific
feature characteristics. Prior knowledge of a site's archaeological component, along with
physical soil properties, such as soil texture, can dictate proper antenna use. Another Roman
period building in the United Kingdom was surveyed using GPR; a 450-1VHz antenna was
chosen over a lower frequency due to the potential signal attenuation in clay-rich soils at great
depths (Linford and Linford 2004). These are two examples of balancing depth of penetration
with the potential of known feature resolution in similar archaeological site parameters.
Soils of Florida
To understand the limitations and efficacy of GPR in Florida, characteristics and properties
of the soil will be discussed. Soil "is a collection of natural bodies on the earth' s surface, which
may be modified or created by human activity, containing living matter and capable of
supporting plants" (Collins 1992). All soils are the product of the environment factors in which
they are associated. The Hyve soil forming factors (time, parent material, topography, climate and
biota) were described first by Dokuchaev (1883) and later by Jenny (1941). Distinct soil forming
factors associated with Florida are reflected in the dynamic and varied soil properties. Resulting
pedogenic processes are the basis for describing and classifying soils.
Soil Taxonomy
Soils in the United States are classified according to Soil Taxonomy (Soil Survey Staff,
1999). Specific information is based on this system of soil classification will be from the Soil
Survey Staff (1999), unless cited otherwise. Soil Taxonomy is based on measurable or
observable properties of soils as described in the field and laboratory. Classification indicators
include diagnostic subsurface and surface (epipedon) horizons based on physical, mineralogical,
morphological, and chemical properties. Soil indicators are referenced and classified to a
maximum depth of two meters, while diagnostic features may be restricted to or exceed this
depth.
Soil Taxonomy is hierarchical with the following categories from the highest to lowest: (i)
Order, (ii) Suborder, (iii) Great Group, (iv) Group, (v) Family and (vi) Series. Soil Orders are the
highest and most inclusive category, while the soil Series is the most comprehensive category.
The state of Florida has seven of the twelve soil Orders: Alfisols, Entisols, Histosols, Inceptisols,
Mollisols, Spodosols and Ultisols (Collins 1997). Soil Order classification is based on the
presence or absence of maj or diagnostic surface or subsurface horizons.
Diagnostic Surface Horizons
All diagnostic surface horizons are termed epipedons, based on the Greek words epi,
meaning over or upon, and pedon, soil. Epipedons that exist in Florida are either organic (histic,
folistic) or mineral (mollic, ochric, and umbric). A summary table of the Hyve epipedons in
Florida is listed in Table 1-2, with the folistic epipedon not included due to the very specific
nature of its classification and limited coverage. Diagnostic surface horizons that have been
altered through anthropogenic influences could be considered anthropic epipedons.
Understanding diagnostic surface horizons is vital in determining successful GPR application.
Epipedon determination may also establish soil Order classification.
Epipedons range in physical, chemical and morphological characteristics. Physical
parameters include mineral and organic soils, while morphological include soil thickness,
structure, and color. Chemical diagnostic properties associated with epipedons include base
saturation (B S) percentage including cation exchange capacity (CEC), listed in Table 1-3.
Particles <0.002 mm in size in Florida have a net negative charge. Positively charged cations are
attracted to these negatively charged surfaces. Most of the cations attracted to the sites are
exchangeable. These soil chemical properties have a tremendous impact on the performance of
the GPR. According to Daniels (2004) soils with a high CEC are more attenuating to GPR than
soils with an equivalent percentage of low CEC. This is similar for soils with elevated levels of
BS, more cation activity in the soil will increase attenuation in the GPR.
Table 1-2. Diagnostic summer of the four eidons used to classic soils in Florida.
Epipedon Base Typical Thickness Organic Horizon General
Saturation Color Content Description
(B.S.) (moist)
Hi stic Low to 10YR 2/1, > 20 cm > 12% Organic Saturated >
high. 0- 2/2 30 days a
100% year
Mollic > 50% 10YR 3/3 > 25 cm > 0.6 to Mineral > 50% B.S.
or less 12%
Ochric 0-100% 10YR 4/4 < 25 cm < 0.6% Mineral Fails to
or more meet
definition of
all other
epipedns
Umbric < 50% 10YR 3/3 > 25 cm > 0.6 to Mineral Similar to
or less 12% Mollic but
less than
50% B.S.
Table 1-3. Cation exchange caacities (CEC) of soil materials (Birkeland 1999).
Soil Material Net Negative Charge (cmol c/k)
Humus (Organic) 100-550
Vermiculite 100-180
Smeetite 80-120
Chlorite 15-40
Gibbsite 4-14
Goethite 4-12
Kaolinite 2-5
Histic Epipedon
The histic epipedon (from Greek histos, meaning tissue) is a horizon 20 cm or more thick
of organic soil material consisting of either muck, peat, hemic or a combination. This organic
soil horizon overlies a mineral subsurface horizon and has a very low bulk density. This
epipedon is saturated with water at some period (30 days or more) of the year and are common in
very poorly drained areas in Florida. Histic epipedons have high electric conductivity, high BS
and very high CEC, (Table 1-2).
Mollic Epipedon
A mollic epipedon is a mineral surface horizon with high accumulated organic matter
content (from .6 to 12 % organic carbon throughout), allowing for a dark brown (10 YR 3/2) to
black moist color (10 YR 2/1). Other diagnostic properties associated with a mollic epipedon are
it must exceed 25 cm in thickness and have a B.S. greater than 50%. Mollic epipedons have a
high electric conductivity and a high CEC.
Umbric Epipedon
Morphologically, the umbric epipedon appears to have the same general characteristics as
a mollic epipedon; the only difference is the B.S. is lower than 50%. Electric conductivity and
CEC are lower than the mollic epipedon.
Ochric Epipedon
The most common mineral epipedon in soils is the ochric (Collins 1992). The
morphological description of an ochric epipedon is a default category by not meeting the
classification of any other epipedons. This surface horizon does not have the diagnostic
properties associated with other epipedons; it is low in organic matter and not dark or thick
enough to be a mollic or umbric epipedon. Electric conductivity and CEC have a wide range of
values in an ochric epipedon and often tend to be lower than most epipedons.
Diagnostic Subsurface Horizons
Diagnostic subsurface horizons provide morphological, mineralogical and chemical
characteristics that enable the soil to be classified. Many of the diagnostic subsurface horizons
are defined by clay mineralogy and chemical components. Only 5 of the more than 18 subsurface
horizons (Soil Survey Staff, 1999) used to classify soils apply to this research and will be
considered. All 5 are located in Florida and pertinent to this study: albic, argillic, cambic, kandic,
and spodic.
Albic Horizon
An albic horizon is defined by a light-colored horizon of eluviation that is low in, organic
matter, clay minerals and iron and aluminum oxides. This horizon is generally associated above
subsurface illuviated horizons in Florida: spodic, argillic, or kandic (Collins 1997). Albic
horizons are predominately made up of white to light gray sand (ex: 10YR 7/1-8/1) particles in
Florida with low electrical conductivity and low CEC.
Argillic Horizon
An argillic horizon is a subsurface illuviation of high-activity silicate clays. The
accumulation of layer-lattice silicate clays in the argillic horizon is due to physical translocation
and chemical transformation soil processes. Concentrations of clay translocated from upper
horizons are called argillans. These interstitial clay skins often coat and form on the surface of
peds and within soil pores between sand and silt particles; it is often the amount of clay that
determines an argillic horizon. An argillic horizon is an illuvial horizon > 15 cm thick in a soil
with 15 to 40% clay. Argillic horizons have medium values of electrical conductivity and a wide
range of CEC.
Cambic Horizon
A subsurface soil horizon that is weakly developed with some color, texture and structure
change is classified as a cambic horizon. The cambic horizon has very little or no significant
accumulation and is characterized by the alteration or minor accumulation of mineral material.
This diagnostic subsurface horizon is weakly to moderately weathered and relates a recent soil
genesis. Cambic horizons have moderate to high electrical conductivities and low to moderate
range of CEC.
Spodic Horizon
An illuvial horizon having an accumulation of colloidal organic matter, Al, and/or Fe
oxides is classified as a spodic horizon. Spodic horizons are highly illuviated subsurface soil
horizons commonly located in Florida' s pine flatwood forests. The black or reddish organic
illuvial horizon is very acidic. Often spodic horizons in Florida underlay highly eluviated
subsurface horizons or mineral and organic epipedons. The amorphous accumulation of organic
matter and oxides in a spodic horizon will increase the bulk density and lower the pH in relation
to surrounding horizons.
Soil Orders in Florida
According to soil taxonomy there are currently 12 soil orders assigned to soils throughout
the world. Soil taxonomy is the classification scheme in use in the United States, and is based
mainly on observable properties (Birkeland 1999). A wide range of soil orders (7) are present
throughout Florida: (i) Alfisols, (ii) Entisols, (iii) Histosols, (iv) Inceptisols, (v) Mollisols, (vi)
Spodosols, (vii) and Ultisols.
Alfisols
Alfisols are classified by the subsurface diagnostic argillic horizon. An argillic horizon
and also a thin gray to brown ochric epipedon are commonly associated with this soil Order.
Alfisols in Florida are characterized by a subsurface accumulation of silicate clays (argillic
horizon) and have a moderate to high level of bases (> 35%). Alfisols are moderately leached
soils that are commonly associated with mixed hardwood forests in well drained to poorly
drained soils.
Entisols
This Order is a very common and morphologically diverse group of soils in Florida.
Entisols are recently developed or show little if any pedogenic development. Parent materials of
this soil Order range from to a marine, aeolian, or alluvium deposition in Florida. Diagnostic
horizons are limited and may include ochric epipedons and albic horizons, yet argillic or spodic
horizons may be present below a depth of 2 m (Collins, 1997, W.G. Harris, personal
communication, 2006, Schultz, 2003). Entisols are primarily quartz sand and may range from
well to poorly drained soils; the CEC and electric conductivity range of these soils are widely
varied as well.
Histosols
Histosols are comprised of organic soil material. Histosols have soil organic material in
half or more of the upper 80 cm, or in two-thirds of a soil overlying shallow rock. Due to the
high organic content, these soils are generally black to dark brown in color and have high water-
holding capacities on a mass basis. Not all wetlands in Florida contain Histosols, however all
Histosols (except Folists) occur in wetland environments. Common names for Histosols are peat
(slightly to moderately decomposed) or muck (highly decomposed). Generally, Histosols have
very high amounts of CEC.
Inceptisols
Inceptisols are the 'inception' of soil development with few diagnostic features. Unlike
Entisols, Inceptisols show more significant soil development in both surface and subsurface
horizons. Umbric and ochric epipedons are very common in this soil Order, yet may have a
mollic or histic surface as well. Subsurface horizons, such as albic or cambic horizons are
represented with the establishment of a structural, textural or color change. Soil properties
associated with Inceptisols range from textures of a sandy loam to fine sand, and moderate to
high CEC in the clay fraction of recently developed illuvial horizons (Collins 1997).
Mollisols
Mollisols are mineral soils which have an accumulation of high organic matter, with a
B.S. greater than 50%. All Mollisols have a dark, humus-rich mollic epipedon 18-25 cm in
thickness (10 cm over bedrock); however a histic epipedon may overlay a mollic. In Florida,
Mollisols have argillic, albic or cambic diagnostic subsurface horizons. A maj ority of Mollisols
are associated with grassland or prairie environments; however, in Florida this soil Order is
primarily poorly to very poorly drained conditions (Collins 1997). High ranges of CEC and low
ranges of electric conductivity occur due to the high organic matter and B.S. inherent to
Mollisols.
Spodosols
Spodosols are mineral soils with a spodic horizon within 2 m of soil surface. Spodic
horizons often underlay very leached eluvial albic horizons, but may have argillic or kandic
horizons as well. Epipedons associated with Spodosols range from ochric to a thin histic. These
soils are often sandy, acidic forest soils with low bases and high amounts of Al. Most Spodosols
occur in poorly drained pine flatwood regions throughout Florida (Collins 1997). Spodosols have
low CEC ranges, while electric conductivity may be quite high down to the spodic horizon.
Ultisols
Ultisols are highly weathered soils with silicate clays and low bases. Intense leaching
from upper horizons allow for the translocation of clay minerals into argillic or kandic
subsurface horizons. Prolonged leaching of Ultisols is characterized by a low amount of bases
(<3 5%), relatively acidic silicate clays, and Fe and Al oxides. Ultisols may have either an ochric
or umbric epipedon. This soil is commonly associated with stable landscapes with mature forest
vegetation. Ultisols are morphologically similar to Alfisols, but are more highly weathered and
acidic. In Florida, Ultisols range from well-drained to poorly drained soils (Collins 1997).
Ultisols have low CEC ranges, with moderate electric conductivity.
Objectives of the Study
The general obj ective of this research was to demonstrate the efficacy of GPR on
anthropogenic sites with selected Florida soils Orders. The suitability of GPR for archaeological
and gravesite detection is not always applicable to pedogenic models. The purpose of this
research is to assist archaeologists and GPR operators to better understand the context of
anthropogenic influences on natural soils.
* Conduct GPR surveys to obtain information about the selected archaeological sites and
cemeteries in Florida
* Establish the extent of archaeological and cemetery soil properties in producing distinctive
anomalous responses.
* Document resolution differences between 900-MHz and 500-MHz GPR antenna usage for
obtaining anthropogenic targets in study areas.
* Determine the suitability of GPR on various Florida soil Orders in an archaeological and
gravesite context by demonstrating the influences of soil physical and chemical properties.
CHAPTER 2
FIELD SITES
Study Site Selection
Four sites were studied to evaluate the application and feasibility for the use of GPR in an
archaeological and cemetery context in the North-Central and Central Florida (Figure 2-1). Field
sites were based on archaeological context and soil variability. Archaeological sites included a
prehistoric habitation site in Lake County on the shore of Lake Apopka and a historic structure
site in St. Johns County, north of St. Augustine. The two historic cemeteries date from the late-
nineteenth century in Orange County to the early and mid twentieth century in Alachua County.
Both the Orange and Alachua County sites are associated with African-American cemeteries.
These study areas were based on four different soil Orders. In Florida soils there are
contrasting subsurface features, i.e. argillic horizons, spodic horizons, layers (organic); lithic
(bedrock) contacts; wetting fronts; and lamellae that are easily exhibited by GPR (Collins 1992).
The properties from a maj ority of Florida soils are conducive to the use of GPR (Collins et al.
1996, Doolittle et al. 2002). The four field study sites selected will elucidate potential concerns
for the use of GPR when applied with soil properties in an anthropogenic context.
Newberry Cemetery
Description
The Newberry cemetery (Davis Cemetery 8AL4992) is located in Section 34 of Township
9, Range 17 East in western Alachua County, Florida. This site lies east of the Brooksville range
on the Wicomico terrace; underlain by alternately thick layers of Plio-Pleistocene material
overlying loamy marine sediments and limestone bedrock (Thomas et al. 1985). Part of the
Alachua Formation, the Newberry Cemetery site area is in the southwestern part of Alachua
County, where it forms low and rolling hills (Thomas et al. 1985). The substrate materials
FI 16~01 12 1240Kilorreten1
represent the residuum of post-Eocene formations (Schmidt 1997). This area has been
extensively mined for rock. This formation varies in depth from 8-12 meters (Thomas et al.
1985). Naturally occurring vegetation in this area includes: live oak (Quercus virginiana), laurel
oaks (Quercus laurifolia) and water oaks (Quercus nigra); longleaf pine (Pinus palustris) and saw
palmetto (Serenoa repens).
Figure 2-1. Location of research sites in Alachua County, Lake County, St. Johns County, and
Orange County, Florida.
Soils
The soils at the Davis cemetery are well-developed Alfisols (Thomas et al. 1985). They
are mapped as Pedro- Jonesville complex, with varying depths of argillic horizon; which are so
intermixed, that they cannot be separated at the scale of mapping (Figure 2-2). Mapped areas of
the complex range from 10 to 50 hectares. Pedro soils are fine-loamy, siliceous,
Trannse:.t 17
Figure 2-2. Soil survey map showing soil series and complex at the Newberry cemetery. The
map was created in ArcGIS 9.1 using data derived from the Alachua County Soil
Survey (Thomas BP, et al. 1985).
hyperthermic, shallow Typic Hapludalfs. The thickness of the solum and the depth to limestone
range from 15-45 cm. The other soil in this complex is the Jonesville series; loamy, siliceous,
hyperthermic Arenic Hapludalfs. Mapped as a complex, the maj or difference between the
Jonesville soil as compared to the Pedro soil is the depth to limestone. Both soils have an argillic
horizon which is from 32-72 cm in depth. Depths to limestone and the argillic horizon greatly
vary within the site. An example of depth to lime rock variability for Alachua County soils is in
Figure 2-3. Overall, this complex has severe limitations for cemetery use.
Figure 2-3. Soil depth to limerock variability of an Alfisol in Alachua County, Florida.
Cultural history
Three headstones were identified in a heavily wooded area north of Newberry, Florida
along transects 14, 17 and 21 in Figure 2-2. In addition to the marked graves, four suspect graves
were located in immediate vicinity; two linear depression and two uninscribed marble footstones.
All three marked graves were inscribed with name, date of birth and date of death. The graves
were identified bearing the names Catherine Alridge, Willies Davis, and W.J. Long. The earliest
recorded date of death was Willie Davis on February 14, 1892. Catherine Alridge was the most
recent grave, dated to June 4, 1918. All marked graves and linear depressions were in an east to
west alignment, denoting a Western Christian burial pattern. Gravestone type and dates of the
four marked graves are in Table 2-1.
Table 2-1. Graves at the Newberry Cemetery. Preliminary Report, Southeastern Archaeological
Research, Inc. Gainesville, Florida.
Name Date of Birth Date of Death Gravestone Material
Type
Catherine 1832 June 4, 1918 Rounded Marble
Alridge Marker
Willie Davis May 14, 1818 February 14, Shouldered Marble
1892 Marker
W.J. Long May 1867 August 14, Rounded Marble
1916 Marker
Historic research conducted by Southeastern Archaeological Research, Inc. (SEARCH) in
the area was inconclusive as to the original name of the cemetery. No known churches or
homesteads with common last names were connected with the Davis Cemetery. No information
could be found on Catherine Alridge or Willie Davis, while only one report of W.J. Long (black
male) places him in the Newberry area during the year of 1916 (SEARCH 2005). Historic deed
research of the Davis Cemetery area indicated that in the first decade of the 20th century the
property was owned, but not developed, by the Florida Land Development Company and was
sold on July 14th 1910 to the Mutual Mining Company of Marion County (SEARCH 2005).
Located in a mixed hardwood hammock, this site area has a high canopy with little under
story growth. North of the graves are three small cedar trees. Cedar trees were typically planted
near the periphery of cemetery boundaries during the late 19th and 20th century in Florida. The
cemetery boundary is identified to be no larger than 32 m east to west and 25 m north to south.
During the time of the research at this site area a 27 m preservation buffer zone was put in place.
No protective fences or markers are located around the heavily wooded area. A town facility is
adj acent to the Davis Cemetery. As of the fall of 2006, this cemetery does not meet the criteria
for eligible inclusion in the National Register of Historic Places (NRHP).
Oakland Cemetery Site
Description
Located in Orange County, Oakland Cemetery (OR9576), also known as the Old African
American Cemetery, is situated in Section 20 of Township 22, Range 27 East. This site lies south
of Lake Apopka in the southern end of the Central Valley. The Lake Apopka area is underlain by
undifferentiated Plio-Pleistocene sediments and sedimentary deposits of the Hawthorn Group
overly the upper Eocene limestone (Doolittle and Schellentrager 1989, Schmidt 1997, White
1970). The geomorphology of the site area is at the interface of the Central Valley and Lake
Wales ridges, part of the Wicomico Terrace (Doolittle and Schellentrager 1989, White 1970).
Topographic variability, associated with the Central Valley and Lake Wales ridge, range from a
5-12 % slope in the site area (Figure 2-3). Natural vegetation is predominately live oak (Quercus
virginiana), bluej ack oak (Quercus incana), turkey oak (Quercus laevis), and sand pine (Pinus
clausa). Surrounding site area has been used for citrus crops during the past century.
Soils
Oakland Cemetery is predominately comprised of Entisols and Ultisols, and is mapped as
Candler-Apopka fine sands with 5-12% slopes and adj acent, depressional Basinger fine sands
(Doolittle and Schellentrager 1989). The Candler-Apopka complex is an excessively drained
soil. This soil complex is associated with uplands and low ridges (Figure 2-4). Candler soils are
classified as hyperthermic, uncoated Lamellic Quartzipsamments; they form in thick deposits of
aeolian or marine sand. Similar in pattern and proportion to the Candler, the Apopka soil series is
a loamy, siliceous, hyperthermic Grossarenic Paleudult. This soil complex is widespread
throughout the site area. The individual soil series cannot be differentiated on a small scale and
are therefore mapped together as a complex.
Figure 2-4. Soil survey map showing the Candler-Apopka soil complex at the Oakland
cemetery. The map was created with ArcGIS 9.1 using data derived from the Orange
County Soil Survey (Doolittle and Schellentrager 1989).
Apopka consists of well drained soils that formed in sandy and loamy marine sediment.
Both the Apopka and Candler soil series are morphologically very similar in the upper meter of
each horizon (see Discussion). The Basinger series is classified as a siliceous, hyperthermic
Spodic Psammaquents; which form in sandy marine sediment. These poorly drained soils are in
shallow depressions and along the rim of larger depressions. An example of a Florida Entisol soil
is in Figure 2-5. The homogenous matrix of the C horizon is evident in the uniform subsurface
radar profiles.
Entisol
~w9r r- r~Yc-f
LYIT-
i.
.~ .. ~ =IFi'
:it
Figure 2-5. Photograph of an Entisol profile in Florida.
Cultural History
The Old African American Cemetery is located north of the State Road 50 and Florida
Turnpike intersection. Along the south border of the cemetery is the remnant of the Tavares and
Gulf Railroad (1891-1971) roadbed. No longer an active cemetery, approximate dates of early
graves are from the early 1890's. The last known graves are from as late as 1952. The cemetery
was not affiliated with any religious organizations and African Americans from the surrounding
communities were also buried in the cemetery (SEARCH 2005). Both the citrus crops and the
railroad line facilitated an influx of migrant workers in the area. Many of the people buried in the
cemetery were citrus farmers and service workers. Also, if any of the migrant workers or
possible transients died while in the area, they were buried in the cemetery as well (Deacon
Moore 2006: personal communication). Census searches revealed most of those buried in the
cemetery are originally from North or South Carolina and Georgia (SEARCH 2005, Florida
Census 1920). African American burial practices associated with this site had a significant
relationship with results of the GPR survey and will be discussed in Chapter 5.
Historic Archaeological Site
Description
This British Period occupation site area is located west of the Tolomato River and north
of Marshall Creek in St. Johns County, Florida. The site (8SJ3 149) lies within the Atlantic
Coastal Lowlands and is less than one-half mile west of the Atlantic Ocean on the Pamlico
terrace. This area was formed as barrier islands and lagoons from the Plio-Pleistocene to recent
times (Davis 1997). Silver Bluffs and Pamlico terraces occur in this intercoastal area. Physical
environment is dominated by pine flatwoods, hardwood hammocks and salt marshes. Hammocks
within the Marshall Creek property are associated with the bottomland hardwood wetlands that
border the coastal salt marshes.
Soils
The soils mapped in the site area are weakly to moderately developed Spodosols with
associated Entisols; and are classified as either Myakka or Immokalee (Spodosols) soils (Readle
1983). The Myakka-Immokalee complex is a nearly level, poorly drained sandy soils located on
flat marine terraces in broad flatwood areas (Figure 2-6). Most of the soils in this complex have
loamy to sandy subsoils that are stained with dark organic accumulations. The Myakka series is
Florida' s state soil and is classified as a sandy, siliceous, hyperthermic Aeric Alaquod.
Immokalee soils are classified as sandy, siliceous, hyperthermic Arenic Alaquods (Figure 2-7).
Figure 2-6. Soil survey map showing soil series and complex at the historic archaeological site.
The map was created with ArcGIS 9.1 using data derived from the St. Johns County
Soil Survey (Readle 1983).
47
Figure 2-7. Photograph of an Immokalee soil series profile.
Cultural History
The Tolomato River and Marshall Creek areas have varied historic and prehistoric
archaeological components. Multiple phases of the St. Johns culture occupied northeast Florida
from around 500 B.C. and lasted until shortly after permanent historical settlements occurred in
1565 A.D. (Milanich 1994). A European power struggle of French and Spanish interests
occurred in the St. Johns River area during the mid-16th century (Contact Period: from 1565
A.D.). In 1565 the Spanish, led by Pedro Menendez de Aviles dispatched the French and
established St. Augustine. Chosen for its strategic location, St. Augustine existed as a military
outpost and a base for missionaries for the area (Deagan 1983). The First Spanish Period (1565-
1763 A.D.) in northeast Florida was a rural mix of Franciscan missions, Indian villages, Spanish
cattle ranches and military fortifications (Bond et al. 1990, SEARCH, 2005). During the British
Period (1763-1784 A.D.), rural construction in northeast Florida increased; plantations, industrial
construction, trading posts, slave cabins and plantation houses developed throughout the region
(Bond et al. 1990, SEARCH, 2005).
Numerous excavations were conducted in the Marshall Creek (8SJ3149) area over the last
decade. Extensive amounts of information have been collected on both prehistoric and historic
archaeological components from the site area. Archaeology on 8SJ3149 was conducted in order
to mitigate development in the vicinity. Multiple scientific disciplines were employed to
facilitate the survey and excavation of this site.
Prehistoric Archaeological Site
Description
This prehistoric archaeological site is known as the Montverde site (8LA243), located in the
town of Montverde in Lake County, Florida. The site is situated in an agricultural area on the
west side of Lake Apopka (Figure 2-8). The site 8LA243 is bordered to the east and north by the
lake, and to the northwest by a freshwater marsh. The geomorphology of the area includes Plio-
Pleistocene sediments overlying Hawthorn deposits and upper Eocene limestone (Doolittle and
Schellentrager 1989, Schmidt 1997, White 1970). Lake Apopka lies in the Central Valley,
associated with the Lake Wales and Winter Haven Ridge along the Wicomico terrace (White
1970). The well-drained soils and proximity to Lake Apopka (Figure 2-9) was conducive to long
term citrus cultivation at the site area. Natural vegetation includes live oak (Quercus virginiana),
turkey oak (Quercus laevis), longleaf pine (Pinus palustris), slash pine (Pinus elliottii), and saw
palmetto (Serenoa repens).
Figure 2-8. Photograph of an excavation at the prehistoric archaeological site along the
southwest shore of Lake Apopka, Montverde, Florida.
Soils
Two soils are mapped with the site area; a well-drained Orlando series and a very well-
drained Entisols classified as the Lake soil series (Furman et al. 1975). Predominately, the site
associated with the Orlando series (Figure 2-6). This series is classified as a sandy siliceous,
hyperthermic Humic Psammentic Dystrudepts. The Orlando series is a nearly level to gently
sloping (0-5%), well-drained sandy soils in association with upland ridges. This Inceptisol
formed in sandy marine sediments and has a thick umbric epipedon. The other soil in the
research site is the Lake series; classified as a hyperthermic, coated Typic Quartzipsamment.
Figure 2-9. Aerial photograph (1999) of the prehistoric archeological site at Monteverde
showing shovel tests and test unit location (Austin 2006). Shovel tests and excavation
units were conducted prior to survey by Southeastern Archaeological Research Inc.
Soil series information derived from Lake County Soil Survey (Furman et al. 1975).
The Orlando and Lake soil soils make up 93 to 99 percent of mapped areas with
marine sediment on upland slopes of 0-5% (Furman et al. 1975).
Cultural History
Previous excavations in the Montverde site area have indicated the presence of two
archaeological components. Upper levels of the excavation units contained St. Johns Check
Stamp pottery, indicating a St. Johns II occupation site; while the lower levels appear to be a St.
Johns I period, dominated by St. Johns Plain ceramics (Austin 2006). The organic midden base is
an early St. Johns I period with related features dating from as early as 1600 B.C.; while dates
within the midden go up to 400 B.C.(R. Austin, personal communication, 2006). Two cultural
features were identified in an excavation unit as circular, basin-shaped pits with fragments of
burned wood in the sandy fill (Austin 2006). The burned wood associated with pit features
allowed for accurate 14 C dating.
CHAPTER 3
MATERIALS AND METHODS
Site Criteria
Each field site area was selected on the key variables of temporal component, spatial
extent, pedological criteria and availability for research. Every site was to be represented by a
soil Order in Central Florida and not to exceed a survey size of 2 hectares. Selected sites were to
reflect field conditions encountered during standard operating archaeological surveys and
excavations. Every field site contained an element of bioturbation and anthropogenic influence
of varying degrees. A common element in all four research areas were the materials used and the
methods employed. Each individual site will include: archaeological field work, GPR survey,
soil sampling and description. Equipment and software used and soil analyses conducted were
identical for all four sites.
Equipment and Software: All four field sites were surveyed with the same GPR system:
SIR-2000 control unit with 500 MHz and 900 MHz ground-coupled monostatic, dipole antennas
with control unit (Geographical Survey Systems, Incorporated, North Salem, New Hampshire).
Both antennas have marker switches located on the handle and manually controlled by the
antenna operator. The control unit is a digital pulse system, with internal hard drive, keypad and
color screen. GPR files may be viewed real-time in the field or data may be downloaded to an
external computer. Each antenna is connected to the control unit by a 60-meter cable. A twelve-
volt battery powers the GPR unit.
Multiple software packages were used in the field and laboratory for GPR, Global
Positioning System (GPS) and Geographic Information System (GIS) data calculation. For all
four sites, GPR files were downloaded from the field to the computer for post-processing
analyses with Data Transfer Utility for Windows 95 and Windows NT, proprietary software of
GSSI (Geophysical Survey Systems Inc.). Post-processing analyses for the manipulation of GPR
data of all sites were conducted using the same computer software package (ReflexW 2.5X,
Sandmeier Scientifie Software, Karlsruhe, Germany). The primary GIS software package used
was ArcGIS 9.1 (Environmental Research Institute, Redlands, CA.). Two different GPS devices
were used in the acquisition of spatially referenced data, TOPCOM 3C total station with
TOPCOM SC data collector. The Garmin etrex VistaThl handheld GPS receiver was also used.
Soil Sampling
Soil samples were collected on site specific criteria. Collection of anthropogenic soils
samples was uniform in depth and quantity within each site area. Physical data acquisition and
soil sampling was done with a bucket auger (8 cm diameter and 17 cm in length). Archaeological
Hield sites incorporated both bucket auger and hand trowel during excavation. Auger samples
were taken with a bucket auger, which was found to pack and hold a greater range of soil
textures encountered from all four site areas. Soils were described and sampled up to a depth of 2
meters for every site. Anthropogenic soils were described on a site specific basis, with no
maximum depth requirement.
Soil samples of approximately 400-500 g each were collected in the Hield and placed in
labeled plastic bags. Soil descriptions were recorded and sample bags were returned to the
University of Florida Environmental Pedology and Land Use Laboratory. In the pedology
laboratory, soil color was determined by visual comparison on moist samples to a Munsell@ Soil
Color Book (GretagMacbeth, 2000). Morphological descriptions from the field and from NRCS
soil survey data were augmented with laboratory data and are listed in Appendix A. Appendices
B and C list the physical and chemical data from each site.
Two types of sampling increments were used for anthropogenic and pedogenic soils:
1. Natural soil samples were taken from each designated genetic horizon revealed in auger
samples for morphological descriptions and lab analyzed in the laboratory.
2. Anthropogenic soils sampled were taken from 20-30 cm interval (depth) samples for
physical and chemical analysis from surface to appropriate depth.
Soil Analyses
Procedural analyses for all soil samples of the four site areas were identical. Processing of
soil samples was done at the same time, using the same equipment and environmental conditions.
Samples were air-dried, screened through a 2-mm sieve, and stored in Analytical Research
Laboratory (ARL) approved soil sample bags. Each of the 232 collected soil samples was
assigned an individual catalogue number for use in laboratory testing and curation. Site specific
identification numbers (e.g., 8LA243: 8 = state of FL, LA = Lake County, 243 = site #), included
the provenience descriptions.
Soil samples were subj ect to physical and chemical analyses. Specific analyses included:
particle size, pH, organic carbon (OC) content, electrical conductivity (EC), extractable
aluminum (Al), extractable iron (Fe), extractable phosphorus (P), extractable magnesium (Mg),
extractable sodium (Na), extractable calcium (Ca) and extractable potassium (K) contents.
Particle-size analysis was used to determine the percentage of sand, silt and clay for textural
classification and subsequent sand fractionation. Soil pH is known as the "master variable"; this
test is done in order to understand the chemical range and parameters within the soil. The amount
of OC was determined to differentiate between a mineral soil (<12%) and an organic soil. The
percentage of O C may also greatly influence the taxonomic classification of a soil, chemical
properties and indicate the presence archaeological middens.
Amounts of extractables P, Ca, Na, Mg, K, Fe, and Al were analyzed to determine the
extent of anthropogenic influences on a pedologic landscape using the GPR Archaeologists have
used soil chemical analyses as both a temporal and spatial indicator of site habitation. Soil
chemical testing of the four bases (Na, Ca, K, and Mg) along with the two acid cations (Al, Fe)
will allow for an increased understanding of natural and anthropogenic site context. Extractables
P and Ca were analyzed to determine if bone diagenesis occurred in the site areas; both P and Ca
are the two most common minerals in bone (Schultz 2003). Distribution of extractable P is a
good indicator of anthropogenic activity, because mean extractable P is notably lower in
naturally occurring soils.
Physical Analysis
All particle-size analysis was conducted at the Environmental Pedology and Land Use
Laboratory, Soil and Water Science Department, at the University of Florida. Particle-size
distribution analysis was conducted using the pipette method (Gee and Bauder, 1986). Soil
samples of 50 g were treated with hydrogen peroxide and heated on hot plates to oxidize organic
material. The samples were then dispersed with sodium hexametaphosphate in de-ionized water.
Dispersed samples were immersed in a 200 C water bath and pipetted to retrieve the clay
fraction. The clay fractions retrieved were dried and weighed. Sand fractions were obtained
from the original sample and removed of remaining silt and clay, then oven-dried and shaken
through nested sieves. Silt content was derived by the subtraction of sand and clay weight from
the total sample weight.
Chemical Analysis
Organic carbon content, pH, EC, extractables P, Fe, and Al were all analyzed at the
Analytical Research Laboratory, Institute of Food and Agricultural Sciences, Soil and Water
Science Department, at the University of Florida. OC content was determined by a modified
Walkley- Black method of dichromate sulfuric acid (Soil Survey Staff, 1996). The calculation of
pH was done by 1:2 water to soil solution by glass electrode of pH meter and deionized water.
EC was determined by 2:1 deionized water to soil solution using a glass electrode. This
procedure was done because EC is directly related to the amount and distribution of ionic
charges in the soil (McNeill, 1980).
The procedure to determine extractables P, Al, and Fe was using a Mehlich 1 extraction
(Mehlich, 1953). This procedure entails 5 grams of soil sample to be added to 20 ml Mehlich 1
solution (0.05 M HCL and 0.0125 M H2SO4). The solution and sample are shaken for 5 minutes
and filtered through Whatman # 42 paper. The extract is then analyzed by an inductively coupled
plasma-atomic emission spectroscopy (ICP-AES) (EPA Method 200.7, Analytical Research
Laboratory 2006). Mehlich 1 was also used for the analyses of extractables Ca, K, Mg, and Na;
the extract is analyzed by atomic adsorption spectroscopy (AAS).
Statistical Analysis
Statistical analyses of the data was based on a standard two-tailed, paired t-Test. Analyses
of the soil data with a t-Test was used to determine whether two soil samples were likely to have
come from the same two populations that have the same mean. The dependent variables are
based on the pedogenic soils from the site. Anthropogenic soil samples are the independent
variable, measured with the dependent pedogenic soil samples. Data from physical and chemical
soil properties sampled from the site associated with GPR transects. The two-tailed t-Test was
performed to determine if soils from a potential anthropogenic site corresponds to the probability
of the known values of the pedogenic site. The statistical program used to perform the standard
two-tailed, paired t-Test was the Microsoft Office Excel 2003, statistical functions.
GPR Data Collection
Each research site was cleared of underbrush prior to GPR survey. Cleared transect paths
allow for an uninterrupted flow of data collection; thereby minimizing post-processing
corrections. Datum points were acquired for every site by a TOPCOM 3C total station and
TOPCOM SC data collector. Reference points were recorded from the datum points located in
the southwest corner of each site. A hand held GPS receiver was used to correlate spatial
coordinates of transects emanating away from the datum points. The GPS handheld receiver was
used along transects in all four field sites. Signal error due to tree canopy obstruction was
minimized by the GPS receiver being placed over known coordinates and physically rectified by
pull tape.
GPR transects for each site were collected in single line grid formation emanating from
datum point coordinates. A 100-meter pull tape laid out each transect in a north-south direction.
Direction and distance were corrected with the use of GPS and hand held SU7UNTOTM Sighted
compass. Pin flags were placed every one to two meters along each transect. Transects were
spaced in one-meter interval grid patterns. A one meter distance between transects was necessary
for complete site coverage with GPR. An antenna was walked along each transect and referenced
with corresponding intermediary trigger-switch marks associated with measured pin flag points.
The antenna was pulled along the same side of the line for consistency. All sites received the
same spatial reference methodology.
Each site contained different and varying soil properties, and thereby required different
range settings and RDP calibrations to determine time-depth conversions. An accurate
conversion of two-way travel time to depth is necessary before the interpretation of data can
commence. Time-depth calculation was determined by auguring to a known depth just off-site.
At one and two meter depths, water was added to the base of the auger hole and immediately
geo-referenced with the GPR with both 900-MHz and 500-MHz antennas. Ranges and dielectric
constants were established and set on each individual site location and date from this information
and referenced with known RDP ranges.
GPR Analysis
Analysis of GPR data often is conducted in a two-step process. The GPR technology used
in this research allowed for real-time data viewing in the field. This enabled the operator to take
corrective measures in equipment calibration and survey technique. In the field, GPR data files
were viewed using a Color Table of 2 and Color Xform of 2. These visual screen settings are
qualitative and subj ect to viewer preference for optimum data interpretation. Field interpretation
of visual GPR data was considered the preliminary step for overall data acquisition. Often times
transects were discounted and field data were reacquired based upon preliminary field
observations. Raw field data contain extraneous background noise or reflections that make
definitive interpretations difficult. Horizontal scale and vertical scales are often not coordinated
effectively in non-processed data.
GPR Post-Processing Analysis
Post-processing is an important step in GPR analysis and interpretation. Qualitative
assessments are greatly enhanced with the manipulation of GPR data; often images and
anomalies are not clear to the operator until the data has been processed. Interpretive strategies
and procedures for the processing of GPR data are numerous. There are fundamental procedures
in the rectification and manipulation of data sets. Spatial adjustment, both vertically and
horizontally, along with background filtering are primary procedures often employed by the
operator. Processing of GPR profiles required a minimum 4 different procedures in order to
interpret the raw data.
Horizontal adjustment was the first procedure for every GPR file. Linear correction is
necessary because the GPR antenna is not pulled across a transect at a constant speed.
Intermediary marks were created at prescribed intervals along each transect during the collection
of data. The known distances between each interval allows the software to the correct distances
between each mark. This step was a trace interpolation/resorting procedure. Vertical correction
was the next step taken for proper depth. GPR antennas are housed in a fiberglass box and
suspended above the ground surface. The actual distance between the antenna and the ground is
seen as an 'antenna ringing' noise that can be corrected. This 'ringing' is seen as a uniform
reflection image and is included in the original data as part of the profile depth. Elimination of
this noise will set the time transmission depth at 0 ns, as 0 meters; this is done through gain
compensation.
After vertical and horizontal adjustments are made, filtering the files of horizontal banding
is done. This process allows for enhanced viewing of anomalies and the removal of unwanted
clutter. Radar attenuation is filtered out, leaving continuous pedogenic horizons, planar and
point-source anomalies. This procedure is a combination of a running and background removal
process.
Study Sites
Newberry Cemetery
The Alfisols at the Newberry Cemetery are not considered highly suitable soil orders in
Florida for GPR application (Collins et al. 1996). Thus, GPR use for this site is not ideal from a
pedogenic context. However, this site was selected for availability, pedogenic diversity from
other selected soil orders and for the community need. The area is heavily wooded and
surrounded by planted pine. Cemeteries are confined to area no greater than 500 sq m; coupled
with a strict temporal range of less than 30 years. There are numerous occurrences of
bioturbation throughout the site that include animal burrows (krotovinas), tree stumps, root ball
inversion and roots. These subsurface anomalies are detected by the GPR and have varying
influences on both the 900-MHz and 500-MHz antennas.
A total of 24 transects were conducted in the cemetery every meter. Each transect was 20
m in length with marker flags placed every two meters for reference points. The general
cemetery area surveyed and staked at 27 m east to west and 21 m north to south by a previously
contracted survey team (Table 3-1). GPR surveys and soil sample collections were conducted
several times over a five-month period (October of 2005 to February of 2006).
Table 3-1. Data points for the four corners of the cemetery boundary. The proj section system used
was UTM, NAD 1983, Zone 17 North.
Northwest Comer: 17R 0344765 W Northeast Corner: 17R 0344786 W
3283016 N 3283015 N
Southwest Comer: 17R 034464 W Southeast Comer: 17R 0344886 W
3282990 N 3282989 N
Oakland Cemetery
The selection of Oakland Cemetery as a research site was a combination of soil
suitability, anthropogenic criteria and the need for mitigation before future development in the
area. The presence of unmarked graves outside the cemetery boundaries was not known by the
town residents or the local, affiliated church. A survey was conducted in order to determine if
any unmarked graves existed outside the historic boundaries of the Oakland Cemetery. This was
achieved through a combination of archived aerial photographs (Figure 3-3), ethnographic
accounts and a GPR survey.
On the eastern shoulder of the site area is a transition from the Lamellic Quartzipsamment
(Candler) down slope to the Grossarenic Paleudult (Apopka). Both of these series are ideal soils
orders in Florida for GPR applications in a pedogenic context (Collins et al. 1996). Typical
vegetation of these soils is sand pine (Pinus clausa), slash pine (Pinus elliottii), chapman oak
(Quercus chapmanii), live oak (Quercus virginiana, and saw palmetto (Serenoa repens). The area
is subj ect to krotovinas. At the base of the slope is a Spodic Psammaquent (Basinger), which is
seasonally flooded for extended periods of time. Naturally occurring vegetation includes
pondcypress (Taxodium ascendens), sweetgum (Liquidambar styraciflua) and scattered pond
pine (Pinus serotina).
red.
A P sre wscndcedaog h isoiclbunais fth aladCmeey
Tranect emnatng utwrd rmkongae er opee nagi pten ahtasc
was ~ ~ seaae ya ee n efrnepitswr lcd vr eer.Telre cl fti
survey as augmnted b a numbr of vlunerwoweeal oplc i-lgso upce
anomaies drin th aacleto.Attlo upce nakdgae eelctdi h
course of three days of surveying. The site was staked with survey markers (Table 3-2) in all four
corners prior to the GPR survey.
Table 3-2. Data points for the four corners of the cemetery boundary. The proj section system used
was UTM, NAD 1983, Zone 17 North.
Northwest Corner: 17R 0437596 W Northeast Corner: 17R 0437696 W
3158418 N 3158417 N
Southwest Corner: 17R 0437596 W Southeast Corner: 17R 0437696 W
3158285 N 3158347 N
Historic Archaeological Site
Research interest in the Marshall Creek site (8SJ3149) was based primarily on the historic
occupation component. The field site in St. Johns County contained Spodosols and peripheral
Entisols, which are two of the best soils orders in Florida for GPR applications in a pedogenic
context (Collins et al. 1996). The area is heavily wooded with numerous occurrences of
bioturbation that throughout the site that include; animal burrows (krotovinas), tree stumps and
roots. Large areas of underbrush were cleared to prepare the site and restrict the unwanted
influences of the GPR survey. Both the 900- MHz and 500-MHz antennas were used and had
varying influences on subsurface detection.
The research site at Marshall Creek was a collaborative effort with SEARCH.
Archaeological excavations were conducted in the area over a six-year period. A small scale
GPR survey was conducted in the August 2005 in a known multi-component site area. GPR data
collection was confined to 100 m2 area adj acent to a block excavation. The excavation units were
placed near previously tested units which contained abundant British period materials (Carlson
2005). The coordinates of site area is shown Table 3-3.
A total of 16 transects were placed in a grid pattern and ran in both north-south and east-
west directions. This was conducted to achieve a greater spatial context of any possible historic
features. Transects were 3 to 5 meters in length with half-meter intervals. Interval distance was
reduced due to the depth of potential targets and smaller elliptical radiation footprint. GPR
surveys and soil sample collections were conducted two times over a period of one month.
Table 3-3. Data points for the four corners of the historic archaeological survey area. The
proj section system used was UTM, NAD 1983, Zone 17 North.
Northwest Corner: 17R 0463935 Northeast Corner: 17R 0463926 W
3322503 3322502 N
Southwest Corner: 17R 0463933 Southeast Corner: 17R 0463925
3322494 3322493
Prehistoric Archaeological Site
Preliminary archaeological work at the Montverde site (8LA243) was conducted in 2004
due to possible future development. Independent to the research work, a contract archaeological
firm (SEARCH) began testing with a subsurface survey of 87 shovel tests throughout the proj ect
area. Prehistoric artifacts were recovered from 50 shovel tests; the center and the southwest
corner of the grove were the only areas void of cultural material (Austin 2005). Excavations units
were then placed in areas of high artifact concentration, along the eastern proj ect area. The units
were situated between the citrus grove edges and the lake shore. The site area extends about 25
hectares across an active orange grove. The site area has a marked slope (>5%) from west at 36
m to the lake shore at 21 m above mean sea level.
The scope of the GPR research site area was confined to potential archaeological
concentrations. A GPR survey was conducted from the block excavation areas between previous
T.U. 1 and T.U. 2. The survey began from an Orlando series (Inceptisol) and continued upslope
in to the Lake series (Entisols). A total of 24 transects were conducted in an east to west
direction in order to determine the transition of the umbric epipedon to an ochric epipedon.
Transects were one meter apart and restricted in grid size due to presence of orange trees, and
were referenced off existing excavation unit datum points and handheld GPS receivers.
CHAPTER 4
RESULTS
Results of interpreting GPR profiles and soil analyses are separated into sections covering
the four research sites. Each section will include: (i) physical and (ii) chemical analyses of
anthropogenic and natural soils, (iii) GPR profiles with the 500-MHz antenna and (iv) 900-MHz
antenna of anthropogenic and natural soils. Comparison of all four sites will be covered in the
discussion chapter. A summary of morphological pedon descriptions and selected physical and
chemical properties are given in Appendices A and C. Additional GPR profiles suing the 500-
MHz and 900-MHz antennas are given in Appendix D.
Newberry Cemetery
Located in western Alachua County, Florida, the Newberry cemetery was selected for this
study based on soil Order (Alfisols) and on anthropogenic context. Research was conducted to
see the effect of the soil on GPR to detect unmarked graves. In order to asses the suitability of
GPR with the soil properties, two different frequency antennas (900-MHz and 500-MHz) were
compared during the survey. The soils from the site area are mapped as well developed Alfisols
(Thomas et al. 1985). These soils are classified as a Pedro- Jonesville complex, with varying
depths of argillic horizon; which are so intermixed, that they cannot be separated at the scale of
mapping (Thomas et al. 1985). The marked graves are from the early twentieth century; several
unmarked graves are located within proximity of only a few meters. This site addressed several
obj ectives of the study: the application of GPR to verify the existence of a clandestine grave
while meeting the criteria of a specific Florida soil Order.
Soil Physical Analysis
Particle-size distribution of native soils at this site indicated soil texture ranging from fine
sand to clay textures. The Newberry cemetery natural soils (NCNS), native Arenic Hapludalfs,
were approximately 91% medium to very fine sand throughout the A and E horizons, with less
than 4% silt or clay. The Ap horizon had a silt content of 3.5 % with a decrease to 2.3% in the E
horizon. The amount of clay increased from < 4% in the Ap and the E horizons to >21% in the
Bt horizon. The silt content increased to < 6% in the Bt horizon for the native soils.
The particle-size distribution of the Newberry cemetery anthropogenic soils (NCAS)
ranged from medium grain sand to a clay fraction. The mixed horizons of the NCAS varied
widely in particle-size distribution. Soils from suspected surveyed graves were ranged
approximately from 86% to 91 % medium to very fine sand in the Ap horizon, with ranges of
4%-6% silt and 3%-6% clay. Soils from the altered El horizon (45-60 cm) had a backfill
scattering that ranged from 11.6% to 42.2% clay. (Figure 4-1).
45
40-
35-
30 o-% Clay
251 (Anthropogenic)
e, 20-
[L15 -m-% Clay
10 V (pedogenic)
0-15 (A) 45-60 (E1) 83-98(E2) 130-142(Bt)
Depth (cm)
Figure 4-1. Depth distribution of total clay content of natural transectt 17) and anthropogenic
transectt 14) soils at the Newberry cemetery.
Medium to very fine sand ranged from 64.2% to 85.1% and the silt content was 5%-6% in the
soil from the anthropogenic altered E horizon. Clay content increased in the associated Bt
horizon in the anthropogenic soil to 41.2%. When the percentage of clay is compared with depth,
clay increased in the NCAS at 45-60 cm along transect 14
Soil Chemical Analysis
The acidity of the NCNS ranged from a pH 5.2 to 8.5 (Appendix C-1). The NCNS along
transect 17 had a pH range of 5.2 to 6.1, with lower pH values located in the E horizon and
higher pH associated with A and Bt horizons. The Bt horizon had 10% regolith, indicating
underlying limestone. Soil acidity was contingent upon depth to limestone. Soil samples
collected near the limestone had pH values higher than any other horizon.
The NCAS had a wide pH range of 5.3 to 8.4 across the site area (Figure 4-2). Cemetery
samples had a discernible pattern of pH change based on sample depth. Soil pH increased along
transect 14, from 7.5 at the Ap horizon (15 cm) to 8.4 at a depth of 115 cm. The pH range for
soils sampled from suspected burials is higher due to the mixing of soil horizons, including
limerock and possible diagenesis of bone.
6 -o pH Anthropogenic
5 -1 soil
4 -( -m- pH Natual soil
15 45 85 115 145
Depth (cm)
Figure 4-2. Depth distribution of Transect 14 pH values and Transect 17 pH values at the
Newberry cemetery
The OC content of NCNS, determined by Walkley-Black digestion, was < 5 g/kgl in all
horizons (Table 4-1). The OC content decreased with depth until the Bt horizon. The NCNS Ap
horizon contained 2.61 % OC. This decreased in the E horizons to approximately 0.35 %
average. The OC content increased in the NCNS Bt to 1.25%. Anthropogenic soil OC content
was similar with the natural soils. The Ap horizon contained 2.8 % OC. A decrease in the E and
Bt horizon occurred to approximately 0.48% and 0.42 % of OC respectively.
The EC (EC) of the NCNS had low values (Table 4-1), ranging from 0.74 to .04 ds/ml
The EC values decreased with depth in the NCNS E horizon, .04 to .06 ds/m- The Bt horizon's
highly conductive clay media had the highest values of .41 ds/m l. The EC of the anthropogenic
soils had a higher range of values. The values for the Ap horizon were .74 ds/m- The EC values
for the E/Bt mixed horizons had a smaller decrease to .35 ds/ml on average.
Table 4-1. Selected soil chemical analysis of the Newberry Cemetery natural and anthropogenic
soils along transects 14 and 17. The EC (EC), extractable (Ext.), Organic carbon
(OC), of the Newberry cemetery natural soils (NCNS), and Newberry cemetery
anthropogenic soils (NCAS).
Soil Depth Horizon EC Ext. P Ext.Ca Ext. Mg OC
(cm) ds m-1 mg/kg mg/kg mg/kg %
NCNS 0-15 Ap 0.28 12.72 188.72 28.06 2.61
Transect 45-60 El 0.06 9.88 60.13 3.94 0.48
17 85-100 E21 0.06 11.96 12.69 3.5 0.23
116-131 E22 0.04 7.1 8.56 1.51 0.23
145-160 Bt 0.41 40.12 1209.4 21.22 1.25
NCAS 0-15 Ap 0.74 32.1 2693.1 53.2 2.8
Transect 45-60 El 0.4 189.8 2141.4 17.2 0.48
14 83-98 E2 0.28 36.6 1167.7 13.1 0.48
115-130 Bt 0.38 80.5 978.6 27.7 0.42
Ext P contents in the NCNS (Table 4-1) ranged from 7.1 to 40.12 mg/kg-l and increased in
depth except between the Ap and El horizons. The Bt horizon had a four-fold increase of Ext P
than from the overlying El and E2 horizon. Overall, the NCAS contained greater values of
extractable P than the NCNS (Table 4-1). Ext P content increased markedly in the El horizon
and reduced to lower values in both the overlying Ap and underlying E2 horizons. The greatest
values of Ext P occurred where the mixing of soil horizons was most pronounced. Ext P content
increased again in the Bt horizon, more than twice as much than the overlying E2 horizon.
Concentrations of Ext Ca in the NCNS ranged from 8.5 to 1209.4 mg/kg with the lowest
value occurring in the E2 horizon and the highest amount in the underlying Bt horizon (Table 4-
1). Proximity of the underlying limerock to the Bt horizon facilitates increased values of Ca in
NCNS. The Ap horizon contained higher values of Ca than that of the underlying El horizon.
Overall values of Ca in the anthropogenic soils were significantly higher in all recorded depths.
Ca content for the NCAS samples were at the high end of the range of all soils in the site area.
Unlike the NCNS, the overall Ca values decreased with depth; both the natural and
anthropogenic soil samples had similar Ca values in the Bt horizon.
Both the natural and anthropogenic soils contained comparable amounts of Mg throughout
(Table 4-1), with the highest values occurring in the Ap horizon and lowest in the El and E2
horizons. The content of Mg in both soils increased in the Bt horizon from overlying El and E2
horizons.
Soils chemical analyses were conducted to determine the differences between natural and
anthropogenic soils. The NCNS have low values of P, and Mg; while increased Ca values are
associated with depth to limestone. The NCAS have increased values of P, Mg, and Ca from
suspected buried remains. The means of these three elements from natural soils were compared
to those of anthropogenic soils by calculating t-tests (Appendix E)
Samples were collected from both natural and anthropogenic soils at the Newberry site
area. The NCNS from the site were used as the control for determination of potential natural
soils. The NCNS from the site area were lower in extractable P concentrations than from the
anthropogenic soils (t = -3.04, p = 0.01019) (Appendix E-1). The mean average for native soils
was 20.5 mg/kg, while the NCAS had a mean average of 68.4 mg/kg. The overall Ca values of
both the NCNS and NCAS were significantly different. Mixing of the anthropogenic soil
horizons fundamentally altered the concentrations of Ca (t = -3.92, p = 0.00153) (Appendix E-1).
Variability of Ca values throughout the soil horizons is reflected in the standard deviation that is
more than double the NCNS. Concentrations of Mg did change between the NCNS and the
NCAS (t = -2.53, p = 0.09874) (Appendix E-1), but not to the extent of the P and Ca
concentrations.
GPR-Soil Results for Newberry Cemetery
The 500-MHz antenna
Data acquisition of both NCNS and the NCAS soils with the GPR using the 500-MHz
antenna created approximate profiles with distinctive reflections caused by contrasting soil
properties. The NCNS has a planar stratification with occasional voids from the karst subsurface
(Figure 4-3). Multiple, continuous contrasting layers in the NCNS soil represent the presence of
an argillic (Bt) horizon. The depth to argillic horizon in Figure 4-3 is approximately 0.9 to 1.1 m.
Soils associated with Typic and Arenic Hapludalfs are often not stratigraphically homogenous.
Bioturbation, such as animal burrows and tree roots, will frequently alter soil horizons.
Processing steps for the horizontal and vertical correlation of the NCNS and NCAS
profiles include marker interpolation for distance (meters) and static correction time cuts for the
removal of antenna ringing and velocity adaptation (Figure 4-3a). The lines superimposed on the
GPR profiles in Figure 4-4 are manual velocity adaptation picks displayed to highlight the
argillic horizon. After the soil surface and horizontal alignment was determined, a background
filter was applied to the transect profile. In order to accentuate and highlight a horizon interface,
spectral whitening was applied to the GPR profiles when necessary (Figure 4-3b).
A discernable difference in interpreting GPR profiles is from the color scale; this is often
the preference of the GPR operator. However by viewing multiple color scales, subtle images
may become enhanced. In the anthropogenic soils, differences in color scale assisted in the
overall interpretation. The profiles viewed in Rainbow 2 color scale from Figure 4-3a is shown in
Grey 1 color scale (Figure 4-3c).
Energy decay was a final processing step chosen for select GPR profiles to augment data
interpretation. The process extracts an energy decay curve of the line and applies the inverse of
this function on the data. By activating this function a gain curve in the time direction (y-axis) is
applied on the complete profile based on the mean amplitude decay curve. This step was
primarily for highlighting the presence or absence of altered, heterogeneous anthropogenic soils
(Figure 4-4). A pick was inserted into selected profiles to highlight subsurface amplitude value
changes. Such changes included the interface of overlying horizons and the argillic horizon
(Figure 4-3a, c).
The GPR profiles of the NCAS produced distinct non-point source anomalies in both the
E2 and Bt horizons. Due to the soil properties associated with the anomaly and stratigraphic
break of the horizons, radar scatter occurred in the GPR profile (Figure 4- 4a). A low-amplitude
reflection with little or no energy returned to the 500-1VHz antenna. This is demonstrated with
the absence of pronounced horizontal banding within the anomaly. Application of specific
processing procedures may either highlight or mask the selected feature. The processing step of
energy decay enables the operator to both highlight the grave and the backfill overburden (Figure
4-4b). With the application of spectral whitening, used for the NCNS profiles, the subtle image
of overburden is less pronounced (Figure 4-4c). GPR profiles with Grey 1 color scale augment
energy decay and spectral whitening processing features while reducing background noise
(Figure 4-5).
DISTANCE [MIETER]
8 9 10 11 12 13 14 15 16 17 15 19
0~ ~~ 131 2 6 6 7 10 11 12 3 14 1 16 1 18 1
20~~~~~~ ** "-t gil c H o
10 1 2 3 1 1 1 3 1 1 6 1 8 1
O 00
ri= 01
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'.''C~-~ ~.ArgCHli2ll Horzo 1c~ ,.
Fiue43 Gz-roudpntaigrdrpoie fteAei aldl sn 0-~ nen
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this~~ prfie bohteatnaniean h oiotlbnin r eoe ihn
loso ntrrttvedt.Veoiyaapainpiki nere ohihih heagli
horizon B) The depth to the a olrgillcE hoEIriznhsbe etfe n smr
prnune whe spcta whtnn is aple wit a bakron fitr Argic14 15 16 17 18 1
hoio is hihihe wit maua pik C) Bakron nos an arili horzoi
moeprmnntwt fle an Gra color, scal appied
2 3 4 567
DISTMECE adEER]
10
DISTANCE dEIER]
10 20
DISTAICE [METER]
0 10 20
0 00 OOO
Fiue44 rudpntrtn aa rflsofnhooei lee Aei aldl sn
The~~ ~ ~ 90-9 nen
subsurfae disGontinuitiesalsoincreasda from tres ofaropotstump antrd Arocks. Mauany ofthse
discntiuites or 'noise were rnot etcted in tern 50-Hz fantuenna. Any usute o pchrangsi P
profleswihdisteinctive rdefletion caued by rcosntrasting soil properies weemreapreti
the90Mzatna h nrae eouinfo he 900-MHz antennawaofstbth
lessened depth of penetration. Radar signals were affected by both the type of anomaly and
depth. Coherent signals were attenuated with specific anthropogenic features.
The 900-MHz antenna was also affected by the depth to the argillic horizon. The depth of
the argillic horizon influenced the higher frequency antenna. On many transects the argillic
horizon was barely visible, or not detected using the 900-MHz antenna (Figure 4-6), but was
strongly evident with the 500-MHz antenna (Figure 4-3).
DISTMNCE *ETER]
OT1 20O
DISTANCE pETER]
Figure 4-5. Ground-penetrating radar profile of anthropogenic altered Arenic Hapludalf using
the 500-MHz antenna along transect 14. A) Filtering of horizontal banding and
background clutter is enhanced in Gray 1 color scale. B) Overburden is more
prominent when the energy decay processing step is applied in the Gray 1 color scale.
C) Note the very low amplitude reflection at the 9.5 to 12 m transect range is more
discernable when the Gray 1 color scale is used.
DISTRACE[MUETEF]
10 20
DIsTarrcE[MUETER]
Figure 4-6. Ground-penetrating radar profile of natural Arenic Hapludalf using the 900-MHz
antenna along transect 17. Velocity adaptation pick is inserted to highlight the argillic
horizon. A) Filtered profile reduces horizontal banding. The argillic horizon is less
discernable than from the 500- MHz antenna. B) Spectral whitening step is added to
filtered profile, highlighting the Argillic horizon. C) Filtering with spectral whitening
process combined with gray scale reduces horizontal banding significantly.
Anomalies detected by the 900-MHz antenna from the NCAS along transect 14 (Figure 4-7) are
discernable with post-processing procedures. Filtered profiles with energy decay processing
applied are more discernable than with just the filter alone; both with Gray 1 and Rainbow 1
color scales (Figure 4-6 b, c). Even filtered, numerous micro-reflections are evident throughout
the GPR profile. This background 'noise' may draw focus from subtle sub-surface features.
OIST~CE ~UIEIER]
O 10
B t..qi:a-r -.
A I =
i
8:5
~
'= -
:i=~i
,-;; ;
f"iv~ r- ~c;
DISTANCE IUETER]
10
DISTANCE IUETER]
Figure 4-7. Ground-penetrating radar profile of anthropogenic Arenic Hapludalf using a 900-
IVHz antenna along transect 14. A) Background filter reduces subsurface
discontinuities throughout the profile. Low amplitude reflection from a feature is
discernable between the 9.5 to 12 m range along transect from 0.5 to 1.6 m in depth.
B) Energy decay processing step is added to background filtering, highlighting the
scattering effect of low amplitude reflections. Overburden is discernable overlying
grave. C) Energy decay with background filtering using Gray 1 color scale further
reduces subsurface discontinuities and isolates the overburden and underlying grave.
Oakland Cemetery
The Oakland cemetery is located south of Lake Apopka in western Orange County,
Florida. This site was selected for the native soils (Entisols) and the anthropogenic context
(cemetery). The soils from the site area are mapped as both Entisols and Ultisols (Doolittle and
Schellentrager 1989). These soils are classified as a Candler-Apopka complex; the mapped areas
consist of generally 66% Candler soil (Entisols) and similar soils, with about 31% Apopka soil
(Ultisols) and similar soils. This soil complex is too mixed to be mapped separately (Doolittle
and Schellentrager 1989). The marked graves are from the late nineteenth to early twentieth
century; several unmarked graves are located within proximity of the existing cemetery. This
site, similar to the Newberry cemetery, addressed several objectives of the study: the application
of GPR to verify the existence of a clandestine grave while meeting the criteria of a specific
Florida soil Order.
Soil Physical Analysis
Particle-size distribution of Oakland cemetery natural soils (OCNS) was dominated in all
samples by the medium grain to very fine grain sand (Appendix A). The soil data were compared
to the information from the Orange County Soil Survey (Doolittle and Schellentrager 1989). The
site area has been mapped as Candler and Apopka-Candler complex. Candler soils are a
hyperthermic, uncoated Lamellic Quaritzipsamments. The Candler soils series consists of
excessively drained soils, an ochric epipedon, approximately 90% medium to very fine sand in
the A and C horizons, and less than 3% silt and 2.5% clay. The ochric epipedon had an average
silt content of 1.8%. The Candler series at the Oakland cemetery has clear, wavy lamellae at
approximately 1.0 to 1.2 m in depth. The amount of clay content increased from < 1.2% in the
Ap horizon, to 2.5% in the C3 horizons in association with the lamellae. At the Oakland site
area, the Candler soil series is associated with the Apopka series. Apopka soils are loamy,
siliceous, hyperthermic Grossarenic Paleudults. These two soils are morphologically very similar
in the upper 1.5 m. The Apopka series has an argillic horizon within 2.0 m of the surface.
Physical soil analyses from the site determined the absence of a Bt horizon, with the default
classification being a Candler soil series. Further discussion of taxonomic and morphological
classification of the Oakland cemetery soil will be addressed in Chapter 5 and Appendix A.
Oakland cemetery anthropogenic soils (OCAS) were dominated in all samples by medium
to very fine sand. Associated with OCNS, the mixed horizons of the altered soils did not change
noticeably in particle-size distribution. Particle-size distributions of the OCAS horizons were
dominated in all samples by the sand fraction, with a range of 95.1 to 97.9%, with low values of
silt (< 2.7%) and clay (< 2.6%). Potential surveyed graves displayed no significant change in
physical properties from the OCAS.
Soil Chemical Analysis
The acidity of the Oakland cemetery soils ranged from a pH 5.9 to 7.1 (Figure 4-8). The
OCNS had a pH range of 4.9 to 5.3, with lower pH values located in the Ap horizon and higher
pH associated with Cl horizons. Soil acidity for the OCNS was not significantly variable, with a
pH range of 4.9to 5.3 of all horizons. Orange groves are located within 75 meters upslope on the
east and north sides of the site area (Figure 2-3). This tertiary influence on pH and other
chemical analyses will be discussed in the next chapter.
The OCAS had a pH range of 6.0 to 7.2 across the site area. Cemetery samples had a
pattern of pH change based on sample depth. Soil pH increased varied from 6.0 in the lower C
horizon (85cm) to 7.2 (50 cm) at two grave samples (Figure 4-8). The pH range for soils sampled
from suspected burials is higher due to the mixing of soil horizons, including possible diagenesis
of bone.
I- pH Antropogenic soil
-m- pH natural soil
15 50 85 120
Depth (cm)
Figure 4-8. Depth distribution of pH values for Transect 2 at the Oakland cemetery.
The OC content of OCNS, determined by Walkley-Black digestion, was < 2 % in all
horizons along transect 2 (Table 4-2). The OC from the OCNS samples decreased with depth
until the C3 horizon. The Ap horizon contained of 1.32 % OC. This decreased in the Cl horizon
to 0.1 %, C2 horizon to 0.16 % and to a 0.29 % in the C3 horizon. The OCAS OC content was
slightly higher than native soils in the Cl horizon and C2, with lower values in the C3 horizon.
The Ap horizon in the OCAS had lower values of OC, with 0.55 %. A decrease in the
anthropogenic Cl horizons occurred to approximately 0.42 % of OC, with 0.48 % in the C2
horizon. The OCAS C3 horizon had lower values than the OCNS C1, C2 horizons with
approximately 0.03 % of OC.
The EC (EC) of the OCNS had low values from transect 2 (Table 4-2), ranging from 0.34
to 0.06 ds/m- The EC values in the Ap horizons of the OCNS were approximately 0.34ds/m l,
and decreased with depth in the Cl horizons, C2 horizons and C3 horizons from .08 to .06 ds/m
1. The EC of the OCAS had a lower range of values. The EC mean average for the Ap horizons
was .14 ds/m- The EC values decreased to .14 ds/m-l in the Cl horizons, .06 ds/m-l in the C2
horizons and increased slightly to.26 ds/m-l in the C3 horizons.
Ext P content in the OCNS (Table 4-2) from transect 2 ranged from 12.8 to 4.29 mg/kg-l
and was variable in depth between the C1, C2 and C3 horizons. The Ap horizon had a value of
12.8 mg/kg- with the C3 horizons having the next highest overall Ext P concentration at 10.41
mg/kg- The OCAS contained greater values of extractable P than the OCNS (Table 4-2). Ext P
content of anthropogenic soils increased markedly in the Ap, with 58.84 mg/kg- with 70.48
mg/kg-l and in the Cl horizon. Lower values of Ext P occurred in C2 with 6.87 mg/kg- and 4.69
mg/kg-l in the C3 horizon. The greatest values of Ext P occurred at a depth of 0-50 cm, where
the mixing of soil horizons was most pronounced.
Concentrations of Ca in OCNS from transect 2 ranged from 26. 14 to 65.45 mg/kg-l with
the lowest value occurring in the lower C2 horizon and the highest amount in the Ap (Table 4-2).
Ext Ca decreased with depth until the C3 horizon (13 5 to 150 cm) with a value of 46.3 8 mg/kg- .
Overall values of Ext Ca in the OCAS were significantly higher in the upper 0.5 m. Ext Ca for
the OCAS ranged from 148.29 mg/kg-l in the Cl horizon to 10.92 mg/kg-l in the C3 horizon.
The OCNS contained lower overall values of Mg than the anthropogenic soils. (Table 4-2).
Ext Mg in OCNS ranged from 25.21 to 9.49 mg/kg- with higher values in the upper 0.5 m and
the lowest values occurring between 0.85 to 1.00 m. Ext Mg in the anthropogenic soils decreased
with values of 14.91 mg/kg-l in the C2 horizon and to 6.01 mg/kg-l in the C3 horizon.
Soils chemical analyses were conducted to determine the differences between natural and
anthropogenic soils. The OGSN have low values of P, Ca, and Mg. Anthropogenic soils have
increased values of P, Mg, and Ca from suspect buried remains. These means of these three
elements from NCNS were compared to those of the NCAS by calculating t-tests
Table 4-2. Selected values of chemical properties of the Oakland Cemetery natural and
anthropogenic soils along transect 2. The EC (EC), extractable (Ext.), Organic carbon
(OC), Oakland cemetery natural soils (OCNS), Oakland cemetery anthropogenic soils
(OCAS).
Soil Depth Horizon EC Ext. P Ext.Ca Ext. Mg Org. C
(cm) ds ml mg/kg mg/kg mg/kg %
OCNS 0-15 Ap 0.34 12.8 65.45 25.21 1.32
Transect 35-50 Cl .08 8.02 47.49 12.46 0.1
2 85-100 C2 .06 4.29 26.14 9.49 0.16
135-150 C3 .06 10.41 46.38 13.05 0.29
OCAS 0-15 Ap 0.14 58.84 127 25.21 0.55
Transect 35-50 Cl 0.14 70.48 148.29 20.22 0.42
2 85-100 C2 0.06 6.87 29.91 14.91 0.48
135-150 C3 0.26 4.69 10.92 6.01 0.03
Samples were collected from both natural and anthropogenic soils at the Oakland cemetery
area. The OCNS from the site were used as the control for determination of suspect
anthropogenic soils. The OCNS from the site area were lower in extractable P concentrations and
variability than from the anthropogenic soils (t = -2.62, p = 0.1853) (Appendix E-2). The mean
for OCNS was 8.26 mg/kg, while the impacted soils had a mean of 34.4 mg/kg. The overall Ca
values of both the OCNS and OCAS were markedly different. Mixing of the anthropogenic soil
horizons altered the concentrations of Ca (t = -1.89, p = 0.2329) in the upper 0.5 m. Variability
of Ca values is limited to the upper soil horizons; this is reflected in the standard deviation that is
more than double that of the natural soils. Concentrations of Mg did change significantly
between the OCNS and OCAS (t = -1.69, p = 0.1625) (Appendix E-2).
GPR-Soil Results for Oakland Cemetery
The 500-MHz antenna
The OCNS has a homogenous matrix with little variation in physical properties (Figure 4-
9). The Candler series at this site has clear, wavy lamellae at approximately 1.0 to 1.2 m in depth
that is evident in the GPR profile with the 500-MHz antenna. Bioturbation, such as animal
burrows and tree roots, will be evident at depths less than 2 meters in the OCNS. Anomalies at
depths greater than two meters often entail targets larger than most bioturbation. Both OCNS and
OCAS GPR profiles are along the same transect.
Identical processing steps for the horizontal and vertical correlation of the GPR profiles at
the Newberry cemetery were used for the Oakland cemetery. This included marker interpolation
for distance (meters) and static correction time cuts for the removal of antenna ringing (Figure 4-
9a). After the soil surface and horizontal alignment was determined, a background filter was
applied to the transect profile. In order to accentuate and highlight a horizon interface, spectral
whitening was applied to profiles when necessary (Figure 4-9c). This step was primarily for
highlighting the presence or absence of altered, heterogeneous anthropogenic soils, but was also
used for the homogenous nature of the soils at the site area. Spectral whitening decreased the
hyperbolic tail associated with the anomalies in transect 2
The GPR profiles of anthropogenic soils at the Oakland cemetery produced distinct point
source anomalies in both the Cl and C2 horizons. Due to the soil properties associated with the
elongated and suspect graves, noticeable reflection hyperbolas occurred in the GPR profile
(Figure 4-9a). Medium to high-amplitude reflections with significant energy returned to the 500-
MHz antenna, enabling a distinct signal return separate from the surrounding matrix. This is
demonstrated with the presence of pronounced horizontal banding within the anomaly.
Background filters allow for a clearer image of an already distinct anomaly. With the application
of spectral whitening, the image becomes more pronounced (Figure 4-9c). A pick was inserted
into selected profiles to highlight subsurface amplitude value changes. Such changes included
the start of the lamellae from 1.0 to 1.5 m in depth.
DISTANCE hnETER]
10 20 30
01T ETR
E~ 07
Ol:T
0 10 20 30
Fiur 4-9. Grudpntaigrdrprfl sn h 0-2 atnawt w upc
bacgrondfilerignote hencrese conras ofsspectgrae and\ te reucio
of- hprboli tal )Bcgon itri pled nen os srmvdadGa
t colo scl sue.Cnrs i nacdadhprolcti sicesd
MFz anenna9 (Figurdee 4-9; wile thea inroieaused rsltion fromz athen 900-Hz atenn wasoffst
by shorter hyperbolic tails in processed profiles. The use of higher frequency antennas may limit
the operator to locating and interpreting anomalies at varied depths along a transect profile.
Anomalies detected by the 900-1VHz antenna from the anthropogenic soils along transect 2
maybe more discernable with post-processing procedures, but not necessary. Filtered profiles
with spectral whitening processing applied are no more discernable than with just the filter alone
(Figure 4-10 b); both with Gray 1 and Rainbow 2 color scales (Figure 4-10 a, c). Filtered, with
spectral whitening allows for less numerous micro-reflections throughout the profile. As with the
500-1VHz antenna profiles, velocity adaptation picks were inserted to the processed profiles to
highlight the lamellae from 1.0 to 1.5 m in depth (Figure 4-10).
Prehistoric Archeological Site
The prehistoric archaeological site is located in eastern Lake County, Florida on the
southwest shore of Lake Apopka. This site was selected for the study based on the both the soils,
(Inceptisol) and on the anthropogenic context (prehistoric). There are two soils are mapped with
the site area; a well-drained Orlando series (Inceptisol) and a very well-drained Entisols
classified as the Lake soil series (Furman et al. 1975). The Orlando series is the predominate soil
for this study. Two prehistoric archaeological components have been previously excavated in
this study area. Associated features within the prehistoric midden date as early as 1600 B.C.
(Austin 2006). This site addressed several objectives of the study: the application of GPR to
verify the extent of prehistoric anthropogenic influences while meeting the criteria of a specific
Florida soil Order.
DIsTaNlCE [FlER]n
"DSTNC [MBER]04
20-
DIsTaNCE [IunlER
10 00a:~ o
r016
10 02
C os
10l!c' 05;7 ,5 1
Figure 4-10. Ground-penetrating radar profile using the 900-MHz antenna of two suspect graves
in a Lamellic Quartzipsamment. A) Background filter is applied and antenna noise is
removed. Horizontal banding is still prevalent. B) Spectral whitening processing step
is added to background filtering, note the increased contrast of anomalies and the
reduction of hyperbolic tail. C) Background filter is applied, antenna noise is removed
and Gray 1 color scale is used. Contrast is enhanced and hyperbolic tail is increased.
Soil Physical Analysis
All horizon designations for this site were described morphologically and subdivided for
sampling purposes. The primary numerical suffixes are denote subdivisions within a master
horizon; e.g., Al, A2, C1, C2, and C3. Secondary numerical suffixes denote the sampling
subdivision within the horizon modifier. Particle-size distributions of the prehistoric
archaeological natural soils (PANS) at this site were dominated in all samples by medium to very
fine sand (Appendix A). The soil data was compared to the information in the Lake County Soil
Survey (Furman et al. 1975). The soil survey area has been mapped as a well-drained sandy,
siliceous, hyperthermic Psammentic Dystrudepts, with an umbric epipedon, approximately
93.5% coarse to fine sand throughout the A and C horizons, and less than 1% silt and 5.7% clay.
The umbric epipedon had an average silt content of 0.8% with a decrease to 0.3% in the C
horizon. The amount of clay content increased slightly from < 5.9% in the A horizon to 6.4% in
the C horizon.
Physical properties of the prehistoric archaeological anthropogenic soils (PAAS) at the
prehistoric site were very similar to the PANS. Both the PANS and PAAS had no morphological
differences in any of the horizons, except an A/C horizon at 0.9 to 1.05 m. The PAAS were
dominated with approximately 94.2% coarse to fine grain sands, less than 1% silt and 6.6% clay
in the A and C horizons. The silt content varied less than 0.7% among the A and C horizons.
Less than a 1% difference in clay content occurred among the A and C horizons in all
anthropogenic samples.
Chemical Analysis
The acidity of the all prehistoric site soils ranged from a pH 4.3 to 6.9 (Figure 4-11). The
PANS had a pH range of 4.3 to 5.5, with lower pH values located in the A horizon and higher pH
associated at a depth of 0.35 to 0.75 m. Soil acidity for the PANS was variable, with a pH range
of 4.4 to 4.6 below 0.75 m. Orange groves are located within 5 to 10 meters upslope on the west
side of the site area (Figure 2-6). This tertiary influence on pH and other chemical analyses will
be discussed in the next chapter.
The PAAS had a pH range of 6. 1 to 6.9 along selected GPR transects (Figure 4-1 1).
Samples had a pattern of pH change, increasing with sample depth. Soil pH increased from 6. 1 at
the surface (0-15 cm) to 6.9 at the base of the C horizon (1.8 to 1.95 m). The OC content of the
PANS, determined by Walkley-Black digestion, was < 2.5 % in all horizons (Table 4-3). In
general OC amounts decreased with depth. The Al horizon contained 2.4 g/kgl OC. This
decreased in the A2 horizon to approximately 1.32 %, with 0.34 % in the C horizons. The PAAS
OC content was slightly higher than native soils in the C horizon. The A horizon in the PAAS
had slightly lower values of OC (1.96%) than the PANS (Table 4-3). A decrease in the PAAS A2
horizons occurred to approximately 1.55 % of OC, with 0.44 % in the C horizons. The PAAS C
horizon had slightly higher values than the PANS C horizons.
5 -o- IpH (natural soils)
..4
-m- pH (anthropogenic
soilIs)
15 45 75 105 135 165 195
Depth (cm)
Figure 4-11. Depth distribution of pH values for transects at the prehistoric archeological site.
The EC (EC) of the PANS had values (Table 4-3), ranging from 1.36 to 0.04 ds/m-1. The
EC values in the Al horizons were approximately 1.36 and 0.62 ds/m-1, and decreased with
depth in the A2 horizons. The values in the C horizons were from 0.04 to .48 ds/m-1. EC of the
anthropogenic soils had slightly lower range of values. The EC values for the Al horizon was 0.4
to 0.28 ds/m-1. The EC values decreased to 0.26 to 0.22 ds/m-1 in the A2 horizons. The values
in the C horizons ranged from 0. 18 to 0. 14 ds/m-1. Overall values decreased with depth in both
the PANS and PAAS horizons. Ext P content in the PANS (Table 4-3) ranged from 343.2 to 70.9
mg/kg-1 and decreased in depth between the Al2 and C13 horizons. The Al2 horizon had
highest value of 353.5 mg/kg-1, with the C13 horizons having the lowest overall extractable
phosphorus concentration at 70.9 mg/kg-1. Anthropogenic soils contained much greater values
of Ext P than the PANS. Ext P content of anthropogenic soils increased markedly in the Al2 and
A21 horizons with lower values in C horizons.
Table 4-3. Selected values of chemical properties from natural and anthropogenic soils at
prehistoric archaeological site. The EC (EC), extractable (Ext.), Organic carbon (OC),
prehistoric archaeological natural soils (PANS), and prehistoric archaeological
anthropogenic soils (PAAS). Soil horizons subdivided for sampling depths.
Soil Depth Horizon EC Ext. P Ext. Ca Ext. Mg Org. C
PANS cm ds ml mg/kg mg/kg mg/kg %
0-15 All 1.36 278 310.4 28.4 2.4
30-45 Al2 0.62 343.2 353.3 36 1.62
60-75 A21 0.32 278 231.2 21.6 1.49
90-105 A21 0.38 203.6 112.6 13.3 1.1
120-135 C11 0.04 167.2 80.7 13.2 0.78
150-165 C12 0.6 78.4 39.9 10 0.13
180-195 C13 0.48 70.9 38.6 9.9 0.13
PAAS
0-15 All 0.4 1400.2 2085 81.4 2.07
30-45 Al2 0.28 1617 2278.1 80.9 2.27
60-75 A21 0.26 1633.5 2347.4 64.7 2.07
90-105 A22 0.22 759.2 801.4 37.4 0.65
120-135 C11 0.18 710 648.6 34.3 0.58
150-165 C12 0.18 449.2 379.5 28.8 0.39
180-195 C13 0.14 388.4 303.4 24.3 0.19
The greatest concentrations of Ext P occurred at a depth of 0.30 to 0.75 m with values of 1617
and 1633.5 mg/kg- Concentrations of Ext P in the anthropogenic C horizon were lower than the
overlying the soil horizons.
Concentrations of Ca in the PANS ranged from 353.3 to 39.9 mg/kg-l with the lowest value
occurring in the lower C horizon and the highest amount in the Al2 (Table 4-3). Ext Ca
decreased with depth. Overall values of Ext Ca in the PAAS were significantly higher in all
horizons. Ext Ca contents for the PAAS ranged from 2347.4 mg/kg-l in the A21 horizon to
303.48 mg/kg lin the C13 horizon. Similar to the PANS the overall Ca values decreased with
depth throughout all horizons.
The PANS contained lower overall values of Mg than the PAAS (Table 4-3). Ext Mg in
the PANS ranged from 36.04 to 9.9 mg/kg-1, with higher values in the Al and the lowest values
occurring in the C horizon. The concentration of Mg in the PAAS decreased with depth with
values from 81.4 mg/kg-1 in the Al horizons to 24.3 mg/kg-1 in the lower C13 horizons.
Native Quartzipsammentic Haplumbrepts from the site were used as the control for
determination of potential anthropogenic soils. Elevated overall concentrations of extractables P,
Ca, and Mg were present throughout the site area; the potential reason for such high values will
be covered in the following chapter. The PANS from the site area were much lower in Ext P
concentrations and variability than from the PAAS (t = -4.71, p = 0.00597) (Appendix E-3). The
mean for the PANS was 224.73 mg/kg, while the impacted soils had a mean of 994 mg/kg. These
values are quite high in both the PANS and the PAAS. The overall Ca values of both the PANS
and the PAAS were noticeably different. Concentrations of Ext Ca in all horizons (t = -1.72, p =
0.01706) (Appendix E-3) were distinct. Variability of Ca values is not limited to any soil
horizons; this is reflected in the standard deviation that is more than five fold that of the PANS.
Concentrations of Mg did change between the PAAS and the PANS (t = -0.541, p = 0. 109), but
not with the significance of both the Ext P and Mg.
GPR-Soil Results for the Prehistoric Archaeological Site
The 500-MHz antenna
The PANS has little variation in physical properties. The Orlando series at this site has a
clear, morphological horizon separation; this depth is evident in the 500-MHz antenna GPR
profile (Figure 4-12). Even in the PANS, punctuated human disturbances are clear throughout
this site area. The GPR profiles of the PANS are along different transects than the GPR profiles
of the PAAS, but run through active orange groves. The GPR transects of the PANS were
conducted upslope and away from the known archaeological site areas, which were situated
along the lake shore. The differences between GPR profiles of the PANS and PAAS are in
context to archaeological significance for this study. Both soils have been altered through human
activities; the difference is temporal instead of spatial and will be covered in the discussion
chapter.
Identical processing steps for the horizontal and vertical correlation of the GPR profies of the
previous sites were used for the prehistoric site. This includes marker interpolation for distance
(meters) and static correction time cuts for the removal of antenna ringing. After the soil surface
and horizontal alignment is determined, a background fi1ter was applied to each transect profie.
In order to accentuate and highlight a horizon interface, spectral whitening was applied to GPR
profiles when necessary. This step was primarily for highlighting the presence or absence of
altered, heterogeneous anthropogenic soils, but was also used for the homogenous nature of the
epipedon at this site.
The GPR profiles of both the PANS and PAAS produced distinct point source anomalies
and planar subsurface interfaces in both the A2 and C horizons. Due to the soil properties
associated with the elongated and perpendicular anomalies of subsurface irrigation lines,
noticeable reflection hyperbolas occurred in the GPR profile (Figure 4-13a). Medium to high-
amplitude reflections with significant energy returned to the 500-MHz antenna, enabling a
distinct signal return separate from the surrounding matrix.
With planar stratification in the soil horizons, removal of horizontal banding greatly
enhances any anomalies. Background filters also allow for a clearer image of an already distinct
anomaly. With the application of spectral whitening, images become more pronounced and non-
point source anomalies are highlighted (Figure 4-13c).
DISTANCE [MIETER]
0 10 20
A Horizon
10
D i"06 I
DISTACE [ETER
A~ Horizon on -
DISTANCE [MIETER]
10
Figure 4-12. Ground-penetrating radar profies of a natural Psammentic Dsystrudepts using the
500-1VHz antenna. A) Background fi1ter is applied and antenna noise is removed.
Velocity adaptation pick is inserted to highlight the C horizon. B) Spectral whitening
processing step is added to background filtering, note the increased contrast between
the A and C horizon. C) Background fi1ter is applied, antenna noise is removed and
Gray 1 color scale is used. Contrast is enhanced between the A and C horizon with
velocity adaptation pick is inserted.
DISTahce PRER]n
0 10 20
Irrigation Dine -
03
DISTA~CE nEER]
]|STANCE PETER]
Figure 4-13. Ground-penetrating radar profiles of an anthropogenic Psammentic Dsystrudepts
using the 500-MHz antenna. A) Background filter is applied and antenna noise is
removed. B) Spectral whitening processing step is added to background filtering, note
the increased contrast between the A and C horizon. C) Background filter is applied,
antenna noise is removed and Gray 1 color scale is used. Hyperbolic tail and contrast
between the A and C horizon is enhanced. Feature banding is highlighted with change
in color scale.
Varying color scales accentuate subtle changes within the GPR profile, allowing the
operator multiple views for data interpretation. A difference in interpreting GPR profiles when
subsurface variation is nominal, offers an advantage with specific sites. In the anthropogenic
soils at this site differences in color scale assisted in the overall interpretation of subsurface
features.
The 900-MHz antenna
The GPR profie of the PANS using the 900-MHz antenna exhibited no distinct reflections
from all horizons. Data acquisition of both PANS and the PAAS with the GPR using the 900-
MHz antenna created shorter wavelengths, thereby increasing resolution of radar images (Figure
4-14).
DISTANCE IAETER]
0 10 20
I~~l _1 4 Horznnn ji
DITN;pRR
,.10 20
DITNE MTR
10202
CL. -Or+Or- 1 er
10~~~- A oizn
-II:L I i E06
f ~SC Horizon 1
13
30 .l1 5
noise is furhe reovd C) Bakron 1ter is apied anea H znos isreovd
Figuran spectra whin-pntening randa Gray color sal iAs usmed.Futher contrat ips usomewhat
apparent. Contrast is enhanced between the A and C horizon with velocity adaptation
pick is inserted.
DISTANCE lulETER]
Irrivaton DiceFeature12
,r- ~132
14
DISTANCE [MIETER]
0 10 20
0 00
10
1'02
PC
Irrigation Dine Fealture r 1
30 1 5
s: :,;5; '.. 1,6,
Figure ~ ~ ~ ~ ~ ~ 3 4-15. Grudpnertn raa rflsoa nhooei smetcDytuet
using~~~~~~~~~~~~~~ th 0-Mzaten.A) Bckgon fite s plidan ntnaosei
reovd B) Spcrlwieigpoesigse saddt acgon trnnt
the~~~~~~~~~ inrese cotatbtenteAadChrzn.C akrudfle sapid
antnn nos srmvdadGa oo cl i sd yeblcti srdcdi
Thgue -5 GPRon-etrig a profiles of th ASpoie nl difuethratigrapic resoluntion Anystubetle
changes ing GPrflswthe 0~ ditnctiena refectirounsasd byte i cotastlieng soiln proerie s wr
aparntinthe anthrops ognic soil usieng the 900-M z antenona C (Figuren 4-1).The increased,
apresoltion from atheooi 900-M s antenna wa ofet by~ shotern hypeurboi tails ofthe irrigation ip
in processed GPR profiles of the PAAS. A pick was inserted into selected profiles to highlight
subsurface amplitude value changes. Such changes included the A and C horizon interface. A
suspected feature is located near the irrigation pipe; this might be associated with the excavation
of the pipe (Figure 4-15). This suspected feature is less prominent in the GPR profile using the
900-MHz antenna, then with the 500-MHz antenna.
Historic Archeological Site
The British Period occupation site is located in northeastern St. Johns County, Florida,
west Tolomato River. This site was selected for the study based on the both the soils,
(Spodosols) and on the anthropogenic context (historic). The two soil Orders mapped in the site
area are weakly to moderately developed Spodosols with associated Entisols; and are classified
as either Myakka/Immokalee (Spodosols) with Paola (Entisols) soils (Readle 1983). The
Immokalee series is the predominate soil for this study. The archaeological context of this site is
primarily the British Period (1763-1784 A.D.), with Spanish and prehistoric components
associated with the site area. This site addressed several objectives of the study: the application
of GPR to verify the extent of historic anthropogenic influences while meeting the criteria of a
specific Florida soil order.
Soil Physical Analysis
The particle-size distribution of the historic archaeological natural soils (HANS) at this site
was dominated in all samples by the medium to very fine sand fraction throughout (Appendix
A). The soil data was compared to the information from the St. Johns County Soil Survey
(Readle 1983). The sampled site area has been mapped as the Immokalee, sandy, siliceous,
hyperthermic Arenic Alaquods series with approximately 95% medium to fine sand in the Ap
and El, E2, and E3 horizons, with less than 2.5% silt and 3% clay. The underlying Bh horizon is
from 0.74-0.93 m, with 2.4% silt and 2.8% clay. The ochric epipedon had an average silt content
of 1.7% with a linear decrease to 0.9% in the E3 horizon. The amount of clay and silt content
increased slightly in the Bh horizon.
The historic site area has another associated soil, a hyperthermic, uncoated Spodic
Quartzipsamment. This soil is the St. Johns series and has very similar morphological
characteristics to the Immokalee. Due to the depth of water table, the St. Johns series may be
more closely relevant to the site. However, from a morphological interpretation, the Immokalee
series will be referred in this chapter as the dominant soil series.
The human impacted soils at the historic archaeological site were dissimilar to the native
Arenic Alaquods. The historic archaeological anthropogenic soils (HAAS) had soil color
differences, lower values and chroma (Appendix A-4) in the horizons El and E2 horizons from
0.2 to 0.45 m. The HAAS were dominated with approximately 93.7% medium to fine sands, with
values of less than 6.0% silt and 3.5% clay in the A, El, and E2 horizons. The Ap horizon had a
mean average of 3.4% silt and 0.9% clay. The El horizon, from 0.20 to 0.25 m, had a mean of
1.9% silt and 1.6% clay; while the underlying E2 horizon had 1.5% silt and 1.7% clay at 0.40 to
0.45 m below surface. Overall silt and clay values are elevated in the El and E2 horizons when
compared to the HANS.
Soil Chemical Analysis
The acidity of the all prehistoric site soils ranged from a pH 4.7 to 7.8 (Appendix C-4).
Representative samples were taken from a HANS transect and a HAAS transect (Figure 4-16).
The HANS had a pH range of 4.7 to 5.4, with lower pH values located in the E horizons and the
higher pH values associated with the Ap horizon. The HAAS had a higher pH range of 6. 1 to 7.8
across the site area (Appendix C-4). Samples had a pattern of pH change, increasing with
sample depth. Selected soil pH from transect 1 increased with 6.1 at the surface (0-5 cm) to 7.5
and 7.6 in the E horizons (20 to 45 cm) (Figure 4-16).
5 1 -o ~pH (natural soils)
a.4-
-m- pH (anthropogenic
soilIs)
5 25 45 65 85
Depth (cm)
Figure 4-16. Depth distribution of selected pH values for transects at historic archaeological site.
Historic site data did not exceed 0.50 m.
The OC content of the HANS, determined by Walkley-Black digestion, was < 6 % in all
horizons (Table 4-4). The OC content decreased with depth in the El and E2 horizons, and
increased in the underlying E3 and Bh horizons. The Ap horizon contained 5.07 % OC. This
decreased to approximately 0.32 %, with 0.26 % in the El and E2 horizons. The Bh horizons
increased to 1.8 %. Both the PANS and anthropogenic soils did not differ significantly in the Ap
horizon. Anthropogenic soil OC content was higher than native soils in the El horizon.
Decreases in the anthropogenic E2 horizon occurred to approximately 0.64 % of OC, yet was
double that of the PANS E2 horizon with 0.25%.
The HANS had values of EC (Table 4-4), ranging from .42 to .02 ds/m- The EC values
in the Ap horizons had the highest PANS values with approximately .42 ds/m l, and decreased
with depth in the E2 horizons, and E3 horizons from 0.04 to 0.02 ds/m- A slight change
occurred in the Bh horizon to a value of 0.06 ds/m- The EC of the anthropogenic soils had
slightly higher range of values. The EC mean average for the Ap
Table 4-4. Selected mean values of chemical properties from PANS and anthropogenic soils at
prehistoric archaeological site. Electrical conductivity (EC), extractable (Ext.),
Organic carbon (OC), historic archaeological natural soils (HANS), historic
archaeological anthropogenic soils (HAAS).
Soil Depth Horizon EC Ext. P Ext. Ca Ext. Mg Org. C
(cm) ds m-1 mg/kg mg/kg mg/kg %
HANS 0-4 Ap 0.42 14.3 7.4 47.6 5.07
4-16 El 0.02 1.1 5.1 3.4 0.32
16-46 E2 0.04 1.2 3.2 2.1 0.26
46-74 E3 0.02 1 3.5 1.4 0.26
74-93 Bh 0.06 27.8 23.4 8.7 1.8
HAAS 0-5 A 0.80 64.3 759.8 130.1 4.49
20-25 El 0.42 383.2 1390.8 50.9 1.28
40-45 E2 0.14 130.8 339.7 9.8 0.64
horizons was 0.80 ds/m- The EC mean values decreased to 0.42 ds/m-l in the El horizons, and
0.14 ds/m-l in the E2 horizons. Overall values decreased with depth in both the PANS and
anthropogenic soil horizons in the upper 0.5 m.
The HANS had Ext P contents that ranged from 1.1 to 27.8 mg/kg-l and decreased in depth
from the Ap to E3 horizons. In the Bh horizon the concentration of Ext P increased. The Ap
horizon had a value of 14.3 mg/kg- with the values stabilizing in the El, E2, and E3 horizons at
1.1 to 1.2 mg/kg- The highest concentrations occurred in the Bh horizon with mean values of
27.8 mg/kg- The HAAS contained more Ext P than the HANS (Table 4-4). Extractable P
content of anthropogenic soils increased distinctly in all horizons. The greatest value of
extractable P occurred in the E2 horizon with 383.2 mg/kg- where morphological alteration was
most prominent. Concentrations of Ext P in the HAAS for the A horizon was 64.3 mg/kg-l and
130.8 mg/kg-l for the E2 horizon.
Concentrations of Ext Ca in the HANS ranged from 3.2 to 23.4 mg/kg-l with the lowest
value occurring in the E2 and the highest amount in the Bh horizon (Table 4-4). Concentrations
of Ext Ca decreased with depth from the Ap horizon (7.4 mg/kg- ), until the Bh. Overall values
of Ext Ca in the HAAS were significantly higher in all horizons. Concentrations of Ext Ca
content for the anthropogenic soil ranged from a low of 339.7 mg/kg-l in the E2 horizon to
1390.8 mg/kg- soils in the El horizon. The Ap horizon also had an elevated concentration of
extractable Ca in the HAAS.
The HANS contained lower overall values of Mg than the HAAS. (Appendix C-4).
Concentrations of Ext Mg in the HANS ranged from 1.4 to 47.6 mg/kg- with higher values in
the Ap and the lowest values occurring in the E3 horizon. The concentration of Ext Mg in the
HAAS also decreased with depth with values from 130.1 mg/kg-l in the Ap horizons to 9.8
mg/kg-l in the E2 horizons (Table 4-4).
The HANS from the site were used as the control for determination of suspected
anthropogenic soils. The HANS from the site area were much lower in extractable P, Ca and Mg
concentrations and variability than from the anthropogenic soils (Appendix E-4). Extractable P
values differed in the HANS than from the HAAS (t = -2.97, p = 0.0934) (Appendix E-4). The
mean for the HANS was 9.65 mg/kg, while the HAAS had a mean of 85.6 mg/kg. The overall Ca
values of both the HANS and the HAAS were significantly different. Concentrations of Ca in all
horizons (t = -2.87, p = 0.0601) varied between soils. Variability of Ca values is reflected in the
standard deviation that is more than ten fold that of the HANS (Appendix E-4). The overall
concentrations of Mg did change between the HAAS and the HANS (t = -1.71, p = 0. 1751i), but
not with the significance of Ext P and Ca.
GPR-Soil Results for the Historic Archaeological Site
The 500-MHz antenna
The natural soil of the HANS has a diverse matrix with variation in physical properties
between the E and Bh horizon (Figure 4-17). The Immokalee series at this site has clear, abrupt
spodic horizon at approximately 0.74 to 0.93 m. This Bh horizon is evident in the GPR profile
from the 500-MHz antenna. Bioturbation, such as tree roots, are evident at depths less than 1
meter (Figure 4-17). The GPR profiles of the HANS and the HAAS are along different transects,
but with 25 m of each other. The length of the GPR transect for the HANS is 3 meters; while the
GPR transects of the HAAS are 2 to 3 meters in length. The length of the anthropogenic GPR
transects were based on the size of excavation unit coverage. In the GPR profile, wall fall debris,
wall footer and a floor from a structure are highlighted in Figures 18 and 20.
Identical processing steps for the horizontal and vertical correlation of the GPR profiles for
the natural soils and the anthropogenic soil at the Newberry cemetery, Oakland cemetery and the
prehistoric site were used for the historic site. This includes marker interpolation for distance
(meters) and static correction time cuts for the removal of antenna ringing (Figure 4-17a-c). In
order to accentuate and highlight the Bh horizon interface, spectral whitening was applied to
profiles when necessary (Figure 4-17b). This step was primarily for highlighting the presence or
absence of the altered, heterogeneous HAAS, but was also used for the homogenous nature of
the soils at the site area. A pick was inserted into selected profiles to highlight subsurface
amplitude value changes. Such changes included a Bh horizon and wall footer. The GPR profiles
of anthropogenic soils at the Historic site produced distinct planar anomalies in both the El and
E2 horizons. Medium to high-amplitude reflections with significant energy returned to the 500-
MHz antenna, enabling a distinct signal return separate from the surrounding matrix. This is
demonstrated with the presence of pronounced horizontal banding within the anomaly
Background filters allow for a clearer image of an already distinct anomaly. With the application
of spectral whitening, any contrast between archaeological features and the overlying soil is
enhanced (Figure 4-18c). The use of Gray 1 color scale enables the operator alternate data
interpretation.
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1 INVESTIGATING ARCHAEOLOGICAL SITE S, CEMETERIES AND SOILS, WITH GROUND-PENETRATING RADAR IN FLORIDA By CHRISTOPHER CHILTON A THESIS PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLOR IDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE UNIVERSITY OF FLORIDA 2007
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2 2007 Christopher Chilton
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3 To my family: Jennifer, Richard, Elizabeth, Cynthi a, Richard Jr. and Randa ll, and all my friends who have helped through the years.
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4 ACKNOWLEDGMENTS This research could not have been comple ted without the advice, guidance and support from numerous individuals. The integration of multiple disciplines required the assistance of many friends, colleagues and mentors. Chiefly, I w ould like to express my gratitude for the vital support, advice and input from my diverse comm ittee. Dr. Mary Collins was essential to my understanding and interest in so il science. Her passion for teachi ng helped create a remarkable environment for learning and critic al thinking. She was an inspirati on for all of her students and I will always appreciate the commitment she had in my education. Dr. James Davidson provided unique insight and knowledge because of his ar chaeological expertise. His work on AfricanAmerican cemeteries allowed for a critical unde rstanding of much of my research. I was most fortunate to learn from him not onl y in the classroom, but in the field as well. Dr. John Schultz provided valuable counseling and support for my research. His tech nical and practical understanding of my work was a tremendous help and allowed me to work through difficult problems. I was most fortunate to have a comm ittee that provided valuable comments and patience while writing this thesis. The Department of Soil and Water Science at th e University of Florida has fostered a great environment for cooperative learning. Never have I seen so many professors and students who are genuinely interested in each others work and who are willing to assist without reservation. Dr. Willie Harris has been a wonderful mentor and a remarkable scientist who helped me as well as many other students throughout his great care er. My fellow graduate students who not only shared an office, but much more, assisted me throughout my research. Dr. Larry ‘Rex’ Ellis, Thomas Saunders and Kelly Fischler were instru mental in my graduate school development and eagerly assisted me whenever needed. I woul d like to recognize thos e undergraduate students who assisted me on many occasions: Victoria Ga rdner, Aja Stoppe and Leanna Woods. I would
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5 also like to recognize Dr. Roc ky Cao, Lisa Stanely and Genero Keehn at the Environmental Pedology and Land Use Laboratory at the University of Florida for their assistance with my soil analyses. I would like to express my gr atitude to the archaeologica l community that guided me through many years of support and inspiration. Dr. Kathleen Deagan and Al Woods took me from the basement of the Florida Museum of Na tural History to the fi eld. Their support guided me to the wonderful people of Southeastern Archaeological Research Inc. The confidence and opportunity afforded me by Dr. A nne Stokes and James Pochurek allowed for my archaeological development for which I will always be grateful . Dr. Robert Austin, Dr . Elizabeth Carlson and Dr. Deborah Mullins have not only had a great impact on my archaeological maturation but have offered assistance and support for my research.
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6 TABLE OF CONTENTS page ACKNOWLEDGMENTS...............................................................................................................4 LIST OF TABLES................................................................................................................. ..........9 LIST OF FIGURES................................................................................................................ .......12 ABSTRACT....................................................................................................................... ............15 CHAPTER 1 INTRODUCTION..................................................................................................................17 Tools and Methodology of GPR.............................................................................................18 GPR Antennas.................................................................................................................18 Radar Propagation and Parameters..................................................................................21 Properties and Materials Af fecting Radar Propagation...................................................22 History of GPR................................................................................................................. ......24 Archaeological and Cemetery Application of GPR................................................................25 History and Use of GPR Mapping in Archaeology and Cemeteries......................................26 Soils of Florida............................................................................................................... ........29 Soil Taxonomy................................................................................................................29 Diagnostic Surface Horizons...........................................................................................30 Histic Epipedon...............................................................................................................31 Mollic Epipedon..............................................................................................................32 Umbric Epipedon.............................................................................................................32 Ochric Epipedon..............................................................................................................32 Diagnostic Subsurface Horizons.....................................................................................32 Albic Horizon..................................................................................................................33 Argillic Horizon...............................................................................................................33 Cambic Horizon...............................................................................................................33 Spodic Horizon................................................................................................................34 Soil Orders in Florida......................................................................................................34 Alfisols....................................................................................................................... .....34 Entisols....................................................................................................................... .....34 Histosols...................................................................................................................... ....35 Inceptisols.................................................................................................................... ....35 Mollisols...................................................................................................................... ....36 Spodosols...................................................................................................................... ...36 Ultisols....................................................................................................................... ......36 Objectives of the Study........................................................................................................ ...37 2 FIELD SITES.................................................................................................................... .....38 Study Site Selection........................................................................................................... .....38
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7 Newberry Cemetery.............................................................................................................. ..38 Description.................................................................................................................... ..38 Soils.......................................................................................................................... .......39 Cultural History...............................................................................................................41 Oakland Cemetery Site.......................................................................................................... .43 Description.................................................................................................................... ..43 Soils.......................................................................................................................... .......43 Cultural History...............................................................................................................45 Historic Archaeological Site...................................................................................................46 Description.................................................................................................................... ..46 Soils.......................................................................................................................... .......46 Cultural History...............................................................................................................48 Prehistoric Archaeological Site..............................................................................................49 Description.................................................................................................................... ..49 Soils.......................................................................................................................... .......50 Cultural History...............................................................................................................51 3 MATERIALS AND METHODS...........................................................................................53 Site Criteria.................................................................................................................. ...........53 Soil Sampling.................................................................................................................. ........54 Soil Analyses.................................................................................................................. ........55 Physical Analysis.............................................................................................................56 Chemical Analysis...........................................................................................................56 Statistical Analysis........................................................................................................... .......57 GPR Data Collection............................................................................................................ ..57 GPR Analysis................................................................................................................... .......59 GPR Post-Processing Analysis...............................................................................................59 Study Sites.................................................................................................................... ..........60 Newberry Cemetery.........................................................................................................60 Oakland Cemetery...........................................................................................................61 Historic Archaeological Site............................................................................................63 Prehistoric Archaeological Site.......................................................................................64 4 RESULTS........................................................................................................................ .......65 Newberry Cemetery.............................................................................................................. ..65 Soil Physical Analysis.....................................................................................................65 Soil Chemical Analysis...................................................................................................67 GPR-Soil Results for Newberry Cemetery......................................................................70 The 500-MHz antenna..............................................................................................70 The 900-MHz antenna..............................................................................................73 Oakland Cemetery............................................................................................................... ...77 Soil Physical Analysis.....................................................................................................77 Soil Chemical Analysis...................................................................................................78 GPR-Soil Results for Oakland Cemetery........................................................................81 The 500-MHz antenna..............................................................................................81
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8 The 900-MHz antenna..............................................................................................83 Prehistoric Archeological Site................................................................................................84 Soil Physical Analysis.....................................................................................................85 Chemical Analysis...........................................................................................................86 GPR-Soil Results for the Prehistoric Archaeological Site..............................................89 The 500-MHz antenna..............................................................................................89 The 900-MHz antenna..............................................................................................93 Historic Archeological Site.................................................................................................... .95 Soil Physical Analysis.....................................................................................................95 Soil Chemical Analysis...................................................................................................96 GPR-Soil Results for the Hist oric Archaeological Site...................................................99 The 500-MHz antenna..............................................................................................99 The 900-MHz antenna............................................................................................102 Summary........................................................................................................................ .......105 5 DISCUSSION..................................................................................................................... ..106 Newberry Cemetery..............................................................................................................107 Oakland Cemetery............................................................................................................... .110 Historic Archaeological Site.................................................................................................113 Prehistoric Archaeological Site............................................................................................117 Ground-Penetrating Radar Comparisons..............................................................................120 GPR-Cemetery..............................................................................................................120 GPR-Archaeological Sites.............................................................................................121 Summary........................................................................................................................ .......122 6 CONCLUSIONS..................................................................................................................128 APPENDIX A SOIL DESCRIPTIONS........................................................................................................132 B PARTICLE-SIZE ANALYSIS.............................................................................................140 C SOIL CHEMICAL ANALYSES..........................................................................................144 D GPR PROFILES...................................................................................................................149 E STATISTICS..................................................................................................................... ...153 LIST OF REFERENCES.............................................................................................................157 BIOGRAPHICAL SKETCH.......................................................................................................164
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9 LIST OF TABLES Table page 1-1 Typical relative dielectric perm ittivities (RDPs) of common materials............................24 1-2 Diagnostic summary of the four epipedons used to classify soils in Florida.....................31 1-3 Cation exchange capacities (CEC) of soil materials (Birkeland 1999).............................31 2-1 Graves at the Newberry Cemetery. Prel iminary Report, South eastern Archaeological Research, Inc. Gainesville, Florida....................................................................................42 3-1 Data points for the four corners of the cemetery boundary. The projection system used was UTM, NAD 1983, Zone 17 North......................................................................61 3-2 Data points for the four corners of the cemetery boundary. The projection system used was UTM, NAD 1983, Zone 17 North......................................................................63 3-3 Data points for the four corners of th e historic archaeological survey area. The projection system used was UTM, NAD 1983, Zone 17 North.........................................64 4-1 Selected soil chemical analysis of the Newberry Cemetery natural and anthropogenic soils along transects 14 and 17. The EC (EC), extractable (Ext.),.....................................68 4-2 Selected values of chemical properti es of the Oakland Cemetery natural and anthropogenic soils along transect 2. The EC (EC), extractable (Ext.),............................81 4-3 Selected values of chemical properti es from natural and anthropogenic soils at prehistoric archaeological site. Th e EC (EC), extractable (Ext.),......................................88 5-1 Coordinate positions of the Newberry cemet ery of selected transects and location of graves......................................................................................................................... ......110 A-1 Official description of Jonesville soil series in Alachua County, Florida.......................132 A-2 Soil description of Jonesville series at the Newberry gravesite natural soils (NGNS)....133 A-3 Official description of Candler soil series in Orange County, Florida............................134 A-4 Soil description of Candler series at the Oakland grav esite natural soils (OGNS), Orange County, Florida...................................................................................................135 A-5 Official description of Orlando so il series in Lake County, Florida................................136 A-6 Soil description of Orlando series at the prehistoric ar chaeological natural soils (PANS)......................................................................................................................... ....137 A-7 Official description of Immokalee so il series in St. Johns County, Florida....................138
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10 A-8 Soil description of Immoka lee series at the historic archaeological natural soils (HANS)......................................................................................................................... ...139 B-1 Soil data from the Newberry Cemete ry Anthropogenic Soils (NCAS) and the Newberry Cemetery Natural Soils (NCNS).....................................................................140 B-2 Soil data from the Oakland Cemetery Anthropogenic Soils (OCAS) and the Oakland Cemetery Natural Soils (OCNS)......................................................................................141 B-3 Soil data from the Prehistoric Archae ological Anthropogenic Soils (PAAS) and the Prehistoric Archaeological Natural Soils (PANS)...........................................................142 B-4 Soil data from the Historic Archaeo logical Anthropogenic Soils (HAAS) and the Historic Archaeological Natural Soils (HANS)...............................................................143 C-1 Soil data for the Newberry Cemetery Anthropogenic Soils (NCAS) from selected transects. Extractable (Ext.) . NCAS Transect 22 15N/21E.............................................144 C-2 Soil data for the Newberry Cemetery Anthropogenic Soils (NCAS) from selected transects. Extractable (Ext.) . NCAS Transect 14 5N/13E..............................................144 C-3 Soil data for the Newberry Cemetery Anthropogenic Soils (NCAS) from selected transects. Extractable (Ext.) . NCAS Transect 10 8N/9E................................................144 C-4 Soil data for the Newberry Cemetery Anthropogenic Soils (NCAS) from selected transects. Extractable (Ext.) . NCAS Transect 14 9N/13E..............................................145 C-5 Soil data for the Oakland Cemetery Anthropogenic Soils (OCAS) from selected transects. Extractable (Ext.) . OCAS Transect 9 40N/10E...............................................145 C-6 Soil data for the Oakland Cemetery Anthropogenic Soils (OCAS) from selected transects. Extractable (Ext.) . OCAS Transect 22 40N/54W............................................145 C-7 Soil data for the Oakland Cemetery Anthropogenic Soils (OCAS) from selected transects. Extractable (Ext.) . OCAS Transect 22 14N/52W............................................146 C-8 Soil data for the Prehistoric Archaeo logical Anthropogenic Soils (PAAS) from selected transects. Extractable (Ext.). PAAS Transect 2 2N/1E......................................146 C-9 Soil data for the Historic Archaeo logical Anthropogenic Soils (HAAS) from selected transects. Extr actable (Ext.). HAAS Test Unit 17, Transect 1 52N/44E...........146 C-10 Soil data for the Historic Archaeological Anthropogenic Soils (HAAS) from selected transects. Extractable (Ext.). HAAS Test Unit 17 , Transect 1 50N/44E.........................146 C-11 Soil data for the Historic Archaeological Anthropogenic Soils (HAAS) from selected transects. Extractable (Ext.). HAAS Test Unit 17 , Transect 3 52N/46E.........................147
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11 C-12 Soil data for the Historic Archaeological Anthropogenic Soils (HAAS) from selected transects. Extractable (Ext.). HAAS Test Unit 17 , Transect 3 51N/46E.........................147 C-13 Soil data for the Historic Archaeological Anthropogenic Soils (HAAS) from selected transects. Extractable (Ext.). HAAS Test Unit 17 , Transect 3 50N/46E.........................147 C-14 Soil data for the Historic Archaeological Anthropogenic Soils (HAAS) from selected transects. Extractable (Ext.). HAAS Test Unit 18 , Transect 8 50N/40E.........................147 C-15 Soil data for the Historic Archaeological Anthropogenic Soils (HAAS) from selected transects. Extractable (Ext.). HAAS Test Unit 18 , Transect 8 52N/40E.........................147 C-16 Soil data for the Historic Archaeologi cal Natural Soils (HANS) from selected transects. Extracta ble (Ext.). HANS, Transect 12 48N/30E............................................148 C-17 Soil data for the Historic Archaeologi cal Natural Soils (HANS) from selected transects. Extracta ble (Ext.). HANS, Transect 14 40N/20E............................................148 E-1 Results of t-tests for Newberry Cemetery natural soils (NCNS) and Newberry Cemetery....................................................................................................................... ...153 E-2 Results of t-tests for Oakland Cemetery natural soils (OCNS) and Oakland Cemetery.154 E-3 Results of t-tests for Prehistoric archaeological natural soils (PANS) and Prehistoric archaeological anthropogenic soils (PAAS) samples......................................................155 E-4 Results of t-tests for Historic ar chaeological soils (HANS) and Historic archaeological anthropogen ic soil (HAAS) samples.......................................................156
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12 LIST OF FIGURES Figure page 1-1 Scale of relative depth of penetration to resolution for gr ound-penetrating radar antennas....................................................................................................................... .......20 1-2 A schematic of reflected and scattered electromagnetic waves as they are transmitted through differing soil properties........................................................................................21 2-1 Location of research sites in Alachua County, Lake County, St. Johns County, and Orange County, Florida.....................................................................................................39 2-2 Soil survey map showing soil series a nd complex at the Newberry cemetery..................40 2-3 Soil depth to limerock va riability of an Alfisol in Alachua County, Florida....................41 2-4 Soil survey map showing the Candler-Apopka soil complex at the Oakland cemetery....44 2-5 Photograph of an Entisol profile in Florida.......................................................................45 2-6 Soil survey map showing soil series and co mplex at the historic archaeological site.......47 2-7 Photograph of an Immoka lee soil series profile................................................................48 2-8 Photograph of an excavation at the prehistoric archaeol ogical site along the southwest shore of Lake Apopka, Montverde, Florida......................................................50 2-9 Aerial photograph (1999) of the prehistoric archeol ogical site at Monteverde showing shovel tests and test unit location (Austin 2006).................................................51 3-1 Aerial photograph of Oakland Cemetery from 1947. Site boundary is highlighted in red............................................................................................................................ ..........62 4-1 Depth distribution of total clay conten t of natural (transec t 17) and anthropogenic (transect 14) soils at the Newberry cemetery.....................................................................66 4-2 Depth distribution of Transect 14 pH va lues and Transect 17 pH values at the Newberry cemetery............................................................................................................67 4-3 Ground-penetrating radar pr ofiles of the Arenic Hapluda lf using a 500-MHz antenna along transect 17.............................................................................................................. ..72 4-4 Ground-penetrating radar profiles of anthropogenic altered Arenic Hapludalf ................73 4-5 Ground-penetrating radar profile of an thropogenic altered Arenic Hapludalf .................74 4-6 Ground-penetrating radar profile of natu ral Arenic Hapludalf using the 900-MHz antenna along transect 17...................................................................................................75
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13 4-7 Ground-penetrating radar profile of an thropogenic Arenic Hapludalf using a 900MHz antenna along transect 14..........................................................................................76 4-8 Depth distribution of pH values fo r Transect 2 at the Oakland cemetery.........................79 4-9 Ground-penetrating radar profile usi ng the 500-MHz antenna with two suspect graves from a Lamellic Quartzipsamment.........................................................................83 4-10 Ground-penetrating radar pr ofile using the 900-MHz antenn a of two suspect graves in a Lamellic Quartzipsamment.........................................................................................85 4-11 Depth distribution of pH values for trans ects at the prehistoric archeological site...........87 4-12 Ground-penetrating radar pr ofiles of a natural Psammentic Dsystrudepts using the 500-MHz antenna...............................................................................................................91 4-13 Ground-penetrating radar profiles of an anthropogenic Psammentic Dsystrudepts using the 500-MHz antenna...............................................................................................92 4-15 Ground-penetrating radar profiles of an anthropogenic Psammentic Dsystrudepts using the 900-MHz antenna...............................................................................................94 4-16 Depth distribution of selected pH values fo r transects at historic archaeological site. Historic site data did not exceed 0.50 m............................................................................97 4-17 Ground penetrating radar pr ofiles of a natural Arenic Alaquodos using the 500 MHz antenna........................................................................................................................ .....101 4-18 Ground-penetrating radar profiles of an anthropogenic Arenic Alaquods using the 500-MHz antenna.............................................................................................................102 4-19 Ground-penetrating radar profiles of a PANS using the 900-MHz antenna. A) Background filter is applied and antenna noise is removed............................................103 4-20 Ground-penetrating radar pr ofiles of a historic archaeo logical anthropogenic soil using the 900-MHz antenna.............................................................................................104 5-1 Example of a root ball in version caused by severe weat her in Newberry cemetery area........................................................................................................................... ........109 5-2 GPR profile at Newberry cemetery of tr ansect 22 using 500-MHz antenna. Grave is outlined demonstrating how a vertic al feature produces scattering.................................110 5-3 Photograph of excavation unit from the hi storical archaeological site. Wall footer/ trench is located in southwest corner of unit...................................................................115 5-4 Ground-penetrating radar prof ile (GPR) of the prehistoric archaeological natural soil (PANS) using the 900-MHz antenna...............................................................................118
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14 5-5 Photograph of soil in abandoned excavati on unit from the prehis toric archaeological site........................................................................................................................... .........119 5-6 Ground-penetrating radar profile us ing 500-MHz antenna from the Newberry cemetery anthropogenic soils (NCAS)............................................................................124 D-1 Ground-penetrating radar (GPR) tran sect 22 of the Newberry Cemetery Anthropogenic Soils (NCAS) using 500-MHz antenna...................................................149 D-2 Ground-penetrating radar (GPR) tran sect 22 of the Newberry Cemetery Anthropogenic Soils (NCAS) using 500-MHz antenna...................................................149 D-3 Ground-penetrating radar (G PR) transect 4 of the Oakl and Cemetery anthropogenic Soils (OCAS) using 500-MHz antenna............................................................................150 D-4 Ground-penetrating radar (G PR) transect 4 of the Oakland Cemetery Anthropogenic Soils (OCAS) using 500-MHz antenna............................................................................150 D-5 Ground-penetrating radar (G PR) transect 4 of the Oakland Cemetery Anthropogenic Soils (OCAS) using 500-MHz antenna............................................................................150 D-6 Ground-penetrating radar (GPR) transect 2 of the Prehistoric Archaeological Anthropogenic Soils (PAAS) using 500-MHz antenna...................................................151 D-7 Ground-penetrating radar (GPR) transect 2 of the Prehistoric Archaeological Anthropogenic Soils (PAAS) using 500-MHz antenna ...........................151 D-8 Ground-penetrating radar (GPR) transect 2 of the Prehistoric ArchaeologicalAnthropogenic Soils (PAAS)..................................................................151 D-9 Ground-penetrating radar (GPR) transect 3 of the Historic ArchaeologicalAnthropogenic Soils (HAAS) using 500-MHz antenna..........................152 D-10 Ground-penetrating radar (GPR) transect 3 of the Historic Archaeological Anthropogenic Soils (HAAS) using 500-MHz antenna..................................................152 D-11 Ground-penetrating radar (GPR) transect 3 of the Historic Archaeological Anthropogenic Soils (HAAS) using 500-MHz antenna..................................................152
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15 Abstract of Thesis Presen ted to the Graduate School of the University of Florida in Partial Fulfillment of the Requirements for the Degree of Master of Science INVESTIGATING ARCHAEOLOGICAL SITE S, CEMETERIES AND SOILS WITH GROUND-PENETRATING RADAR IN FLORIDA By Christopher Chilton May 2007 Chair: Mary E. Collins Major: Soil and Water Science Ground-penetrating radar (GPR) is an effi cient and nondestructive instrument for collecting information below the ground surface re lating to potential archaeological sites and cemeteries. This research assessed the appli cation of GPR technologi es for archaeological investigations with multiple soil orders of Flor ida. By differentiating the archaeological anomaly from natural pedogenic properties, a qualitative interpretation of a site can determined. Four sites were selected based upon arch aeological context and soil properties in Florida. The anthropogenic sites included two cemeteries; the Newberry cemetery located in Alachua County and the Old African American Cemetery in Oran ge County. The one historic archaeological site is located in St. Johns County a nd a prehistoric archaeological site is in Lake County. Each site had a different soil order commonly encountered in Florida (Alfisols, Entisols, Inceptisols and Spodosols). Natural and anthropogenic soils we re surveyed using 900and 500-MHz antennae. Soil samples were collected along GPR surveyed transects and analyzed for physical and chemical properties including text ure, pH, and electrical conduc tivity. Post-processing of the GPR data was conducted to augment profile interp retation and assess the differences in imagery of the 900and 500-MHz antennae.
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16 Results of the GPR and soil analyses revealed that each was dependent upon the anthropogenic context. Diagnostic horizons had a greater influence than soil order classification on the successful application of GPR on archaeo logical sites and cemeteries. Soil physical properties, specifically texture, had a greater overall impact than soil chemical properties on the radar propagation in every site. The 500-MHz antenna was preferred over the 900-MHz antenna for general performance in all four research s ites, regardless of soil order. 500-MHz antenna preference for the GPR was based on depth of radar wave penetra tion and the general background noise associated w ith the higher frequency antenna. Though diagnostic surface horizons and soil texture influenced GPR inte rpretation, this study showed that GPR is applicable in a wide variety of soil and archaeological cont exts in Florida.
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17 CHAPTER 1 INTRODUCTION Ground-penetrating radar (GPR) ha s become a comprehensive and reliable remote sensing tool for gathering and processing geophysical info rmation. GPR is a method that provides rapid and non-invasive identification of subsurface fe atures and materials. Recent technological innovations, such as real time video display with post processing software on the control unit, have improved the effectiveness of data acquisi tion and processing along with increasing the use and application of this tool. The technological adva nces in GPR in the past decades have allowed its use today to become common and accepte d procedures in many disciplines. Many land-use activities have the potential for the application of GPR. Numerous scientific and commercial fields such as: geol ogy, mining, engineering, c onstruction, agriculture, environmental science and ar chaeology are turning to real -time and nondestructive data acquisition tool. Also, because of the easy and rapid use of this instrument, there has been an increase in the utilization for surveying, mappi ng, mitigating and delineating subsurface features. Soil scientists and geologists have used GPR to map subsurface horizons, delineate karst features, detect sinkhole formati on, and differentiate bedrock un its for industrial minerals (Doolittle and Collins 1998, Collins 1990, Puckett 1990, and Dekeyser 2005). The military is able to save lives by detecting buried la nd mines and unexploded ordinance (Hyde 1997). Engineers have applied this efficient technol ogy to high-speed rail trackbed investigations associated with high-speed trains (Doshi a nd Al-Nuaimy 2006). GPR was used in May 2005 for a search mission after a mountai n accident in the Chilean An des involving the death of 45 military troops (Casassa 2006). The success of GPR in the past has create d strategies for the future; scientists are planni ng to conduct geophysical surv eys on Mars (Olhoeft 1998).
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18 Tools and Methodology of GPR GPR is a method that is able to prod uce large amounts of high resolution, multidimensional information through the transmission of electromagnetic waves. This tool actively produces multiple pulses of energy derived from a control unit. Fiber-optic cables transmit a digital signal to and from the antennas; the raw da ta derived from the generated electrical pulses are received and displayed in a video or prin ted format (Conyers and Goodman 1997, Davis and Annan 1989, and Schultz 2003). The transmission of electromagnetic radar pulses travel through the earth’s surface and any of these pulses whic h are reflected will be received and recorded. Energy is transmitted and energy is received thro ugh antennas; the frequencies of these antennas range from a bandwidth of about 10 megahertz (MHz) to 1500 MHz. GPR Antennas Transmitting and receiving antennas used for GPR are configured in either a monostatic or bistatic mode. The monostatic mode is where th e transmitting and receiving antennas is at a zerooffset, there is no separation from the point of tr ansmission to the point of reception. This allows for a self-contained unit with less variability. On the contrary, the bistatic mode has two separate points for transmission and reception of radar en ergy. Separation of these independent points can be manipulated in the field to determine radar wave velocity. The recorded time of transmission from one antenna to another through a known distan ce of material can be measured and thereby calculate the radar wave veloci ty (Conyers and Goodman 1997). Configuration choices for GPR antennas may be based on the type of field questions asked. Different GPR applications demand different antennas. The choice for standard transmitting antennas is generally straightforward, the dipole or bowtie traveling-wave antenna have been primarily used for the impulse-based radar system (Daniels 1996). The transmitting antenna emits an elliptical cone of radar energy with the apex of the cone located in the center of
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19 the antenna (Davis and Annan 1989, Schultz 2003). The elongated shape of the elliptical is usually parallel to the dir ection of the antenna moveme nt along the ground (Conyers 2004, Conyers and Goodman 1997). This shape of tran smitted radar energy plays a role in survey parameters. The size and shape of the transm ission cone is primarily dependent upon the physical properties of the soil, th ereby dictating the spa tial parameters of collecting data in the field. Some antennas have an added feature that allow for a reference mark to be employed during a survey. This mark is activated when a trigger switch is pushed on the antenna handle by the operator, allowing for a spat ially referenced point along a GPR transect. Marked points on the radar transect are coordinated with field gr id markers that can be located using a global positioning system (GPS) to create a three-di mensional reference points (Conyers 2004, Conyers and Goodman 1997, Tischler 2003). Techniques for GPR vary widely, each according to their application. There are restrictions to the range of the operating system. Selections of antennas are based on the depth and resolution for area of study (Davis and Annan 1989). Figure 11 illustrates the commercial range of antenna frequencies and properties. Highe r frequency antennas (e.g. 900 MHz) offer a greater ability to differentiate features of vary ing size from a surrounding matri x, but are limited in depth of penetration. Conversely, the lower frequency ante nnas (e.g. 120 MHz) allow for greater depth at which a GPR signal will be reflected back to the surface, but provide a lower range of resolution. Any radar frequency used will be determined upon not only by the depth of study and the subsurface features of that study, but upon the inherent properties of site area.
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20 Antenna Frequency Properties1 2 3 4 5 6 7 8 9 10 10 9 8 7 6 5 4 3 2 1Blue = Resolution Red = Depth All on a scale of 1-10 1000 mHz 900 mHz 800 mH z 700 mHz 600 mH z 500 mHz 400 mHz 300 mHz 200 mHz 100 mHz Figure 1-1. Scale of relative depth of penetra tion to resolution for ground-penetrating radar antennas. Resolution capability is inversel y proportional to depth of penetration. (From Tischler, 2003. Integrating Ground-Pene trating Radar, Geographic Information Systems and Global Positioning Systems fo r ThreeDimensional Soil Modeling). The type of antenna frequency used is limite d by the properties of the material that is surveyed. A receiver bandwidth in excess of 500 MHz, and typically 1 GHz, is required to provide a typical resolution of between 5 and 20 cm, depending on the relative properties of the soil (Daniels 1996). Antennas used in most archaeological co ntexts are the 500-MHz and 900MHz antennas; while lower freque ncy antennas are often used to interpret the geomorphology of many prehistoric sites. Equipment choice can be a compromise between resolution, scope of signal processing, and the ability to effectively offset the negligible properties of subsurface material. Frequency selection is dependent upon site parameters and survey objectives. Annan and Cosway (1994) listed a number of factors co ntrolling frequency selection: (i) electrical
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21 properties of the host environment, (ii) depth re solution, (iii) clutter dimension, (iv) depth of exploration and target size, (v) site a ccess and (vi) any external interference. Radar Propagation and Parameters The effectiveness of the radar is depe ndent upon the ground in which it penetrates; specifically the properties beneath the surface. GPR has been used to investigate ice, water, rock, pavement, soil and many other natural and human environments (Olhoeft 1996). The success of these numerous applications has all been ba sed on the ability of the transmission of electromagnetic waves. Figure 1-2. A schematic of reflected and scattere d electromagnetic waves as they are transmitted through differing soil properties. Antenna disp layed is a monostatic system with both a transmitter (Tx) and recei ver (Rx). (From Schultz, 2003. Detecting Buried Remains in Florida Using Ground-Penetrating Ra dar. Doctoral Thesis in Forensic Anthropology, University of Florida, p.28, Figure 4). The physical properties that affect the radar wave s as they pass through a medium are electrical conductivity and magnetic permeability (Annan et al. 1975). Radar pulses generate a wavefront which propagates downward and is partially refl ected by any change in the electrical bulk properties of the soil (Figur e 1-2) (Vaughan 1986), GPR meas ures the changes in these
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22 properties. Any of the electromagnetic energy that is reflected because of changes in these properties is amplified and record ed through the rece iving antenna. Use of GPR requires the system operator to accurately understand the constraints of the study area. Two factors must be determined prior to the operation of the equipment: the dielectric constant and the range. Accurate configuration of the system will determine the proper depth of signal penetration and resolution of that signal. Both range and dielectric constant are system parameters that are set individually, but are dependent upon one another. An accurate range cannot be set without a general knowledge of the subsurface dielectric constant. The range is a parameter that has a time va lue measured in nanoseconds (ns.) A range value is entered into the GPR control unit in order to determine how long to record received signals after a radar pulse has been transmitted (Geophysical Survey Systems Inc. 1994). Any portion of the radar pulse which can penetrate into the subsurface material, reflect from a boundary or object and return to th e antenna is recorded and displa yed in real-time. As time is increased for the range setting, radar waves will penetrate the subsurface further in depth, yet resolution and reflected data decreas e with depth. There are finite restrictions to range settings and the distance for which radar waves will travel. The time (ns) for a pulse to reach an object or boundary is dependent upon the material through wh ich it passes. Restrictions to the range are reliant upon frequency of the antenna and the dielectric constant. Properties and Materials Affecting Radar Propagation Electromagnetic pulses that are transmitted from the GPR antenna pass through space. If this space is in a vacuum, then an electrom agnetic pulse will travel at 0.2999 meters per nanosecond. However, GPR is used over the gr ound and the materials located beneath the surface range from soil, rock, ice, water and air to anthropogenic re mains. Materials in the earth have a range of dielectric properties which a llow the passage of electromagnetic energy. The
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23 more electrical conductivity a gi ven material has the less dielectri c it is; therefore for maximum radar-energy penetration, a highly dielectric medium with a low electrical conductivity is required (Conyers and Goodman 1997). The dielectric constant is a parameter require d in the calibration for the maximum effective depth of the GPR energy waves. This constant, al so known as the relative dielectric permittivity (RDP), is measured against the heterogeneity of an object or ear th’s natural subsurface system. The RDP is the capacity of a material to store, and then allow the passage of electromagnetic energy (von Hippel 1954). Dielectric characteristics of materials vary greatly. Calculation and measurement of RDP is based on of the velocity of an electromagnetic pul se in a vacuum. When a pulse travels in a vacuum at 0.2998 meters per nanosecond then the RDP is 1 (Conyers and Goodman 1997). Materials with a low dielectric consta nt, allow the passage of electromagnetic waves with little or no dissipation, while highe r conductivity will create greater dissipation of radar waves or attenuation. Soil and consolidated earthen material are bo th filters and boundaries to radar waves, depending upon the dielectric proper ties of the medium. Dielectric constant values range from air (low), to sea water (high) and vary according to the properties associated with subsurface materials (Table 1-1), (Davis and Annan 1989, Geophysical Survey Systems Inc. 1994). Materials composed primarily of air are less elec trically conductive and are termed to be less dielectric. Conversely, the RDP of water is of the order of 80, therefore even small amounts of moisture will cause a significan t increase of the relative permitt ivity of material (Daniels 1996).
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24 Table 1-1. Typical relative dielectric perm ittivities (RDPs) of common materials. Material RDP Air 1 Dry sand 3-5 Limestone 4-8 Clay 5-40 Concrete 6 Dry sandy coastal land 10 Average organic-rich surface soil 12 Marsh or forested land 12 Organic-rich ag ricultural land 15 Saturated sand 20-30 Fresh water 80 Sea water 81-88 Modified from Davis and Annan (1989) and Geophysical Survey Systems, Inc. (1987). History of GPR GPR has a history that was a precursor to its own rediscovery. The first practical application of GPR was in 1929 by W. Stern for de termining the depth of an Austrian glacier (Olhoeft 1996). The United States Air Force deve loped better radar systems in the late 1950’s when several pilots crashed on icy runways b ecause conventional radar was transmitting through the ice and reading inaccurate altitudes. In 1960, John Cook made the first proposal for the detection of subsurface reflections using radar in his article “Proposed monocycle-pulse, VHF radar for airborne ice and snow measurements.†From this work, the development of radar systems to detect subsurface reflections continue d. The subsurface radar system from the late 1920’s had not changed all that much when us ed for the Apollo 17 lunar mission in 1972. The need for alternative applications by the U.S. m ilitary during the Vietnam War created an increase in GPR development and advancement, hence the redundant use of acronyms. Radar is an acronym for Radio Detection and Ranging. Commercial availability for GPR technology was introduced in 1972 by Geophysical Survey Systems Inc. (GSSI), ushering in a myriad of applications and extensive research to
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25 universities and private companies alike. GPR development increased during the 1970’s; Moffatt and Puskar (1976) improved the target-to-clut ter ratio of antennas and thereby increased subsurface reflection accuracy. With increased an tenna capability, new methods were able to estimate the location of mines, faults a nd underground tunnels (Cook 1975, Moffatt and Puskar 1976). GPR technology in the early 1980’s was used as a pedologic tool (Collins 1992, Doolittle 1982) and to investigate the depth of groundwater (van Overmeeren 1994). GPR has been used to map bedrock surfaces, detect sinkholes and delineate karst features (Collins et al., 1990, Doolittle and Collins 1998, Puckett 1990). As advancements in technologies emerged during the 1980’s, methods of processing and analyzing GPR data became more widespread and available to a variety of scientific fiel ds. This increase in available GP R technology created many diverse applications. Archaeological and Cemetery Application of GPR The field of archaeology has long relied upon the use of multiple sc ientific disciplines, ranging from geology to zoology. T echniques and tools from these other areas of studies have worked well in shaping the way archaeologists c onduct their research. In the past three decades, the use of GPR has provided a means for analyz ing an archaeological site in a nondestructive way. GPR is a tool that increases the spatial extent of a study ar ea, while reducing the amount of time to conduct a preliminary survey. Data is coll ected in real-time and conveyed to the operator allowing for rapid reconnaissance. Archaeologists often destroy the area they study through excavation. GPR nondestructively records and saves all data that are collected, th ereby allowing decisions to be made prior to disturbing a site. The capability of GPR to estimate depth and sh ape of buried objects make its use suitable to grave detection (Bevan 1991). Vary ing site characteristics and context are also amenable to the use of radar. To determine whet her artifacts were present in a site often required
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26 a great deal of exploratory digging, thereby greatly increas ing time and expense (Vaughan 1986). Field season at an archaeological site is usually short and successes are often dependent upon many variables including equipment, personne l and weather. Surveys conducted with GPR may narrow the scope of interest and reduce th e labor-intensive process associated with excavation. History and Use of GPR Mapping in Archaeology and Cemeteries The increased success of GPR in archaeology has been related to the various circumstances in which the technology is used. Advances in te chniques have created gr eater interpretation of data. Until recently, GPR was simply used to id entify subsurface “anomalies†that may not have represented archaeological f eatures (Conyers and Cameron 1998). Fast and accurate archaeological surveying of large areas using GPR has even created new word usage. Geophysical ‘prospection’ is now considered a standard method for detecting buried archaeological features and structures (Leck ebusch 2003). No matter the terminology, GPR has become recognized as an important tool for numerous archaeologi cal applications. The archaeological applications of GPR range fr om spatial parameters to temporal context. Spatially, surveys are able to locate site s and delineate anthrop ogenic boundaries, while superposition can be conveyed through stratig raphic sequencing and the mapping of features (Dalan and Bevan 2002, Conyers 1995, Conyers and Goodman 1997, Sassaman et al. 2003, Schultz 2003). The absence or presence of soil he terogeneity may also indicate an anthropogenic site. This is contextual and site specific. A GP R survey of a possible prehistoric mound from the Effigy Mounds National Monument in Iowa revealed symmetrical curving strata more consistent with a prehistoric cultural mound than caused by natural phenomena (Whittaker and Storey, 2005). Reinterpretation and nondestructive analyses of the mounds has continued for the past 40
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27 years. Whittaker and Storey (2005) affirm the potential of GPR for archaeological preservation with ongoing research at Effigy Mounds Nati onal Monument. Sufficient knowledge of local landforms and processes may allow a determina tion of earthen features (Dalan and Bevan, 2002). When taken in context to surrounding geomorphology, sequencing and uniformity in radar profiles may suggest possible human augmentation. GPR use can incorporate surface anomalies wi th subsurface uniformity. Discontinuities between cultural features with the natural soil matrix extend spatial parameters for delineating the lateral extent and thickness of shell mi ddens (Chadwick and Ma dsen 2000). Near surface lithological features create discrete anomalous characteristics. Such highlighted features may expose potential voids beneath such as gravesto ne chambers (Lorenzo and Arias 2005). GPR in archaeology not only highlights di scontinuities within the soil, but reveals materials and objects anomalous to a known area. The successful use of GPR for locating histor ic graves has ranged widely, often with varying results in the same site area. Intrasit e soil conditions and burial practices may vary, enabling clear and distinct reflections or attenuation. Even with mixed success, GPR is considered the most reliable geophysical t ool for locating graves. A model study by Bevan (1991) was conducted at nine diffe rent sites in the United States that used both GPR. One study site, the Poor Farm Cemetery in Rockville, Mary land, had no marked graves. Radar reflections at this site exhibited grave features; however, ex cavation showed the reflection to be a natural change in the soil. The study Bevan (1991) conducted at the different sites illustrated the varying degree of success with GPR on cemetery graves. Controlled archaeological and forensic tests ha ve been conducted to establish the efficacy of GPR. Schultz (2003) tested th e applicability of GPR to detect buried bodies in two different
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28 Florida soils. Pig cadavers, with varying wei ghts and sizes, were selected as surrogates for human bodies and buried at two depths. Factors that controlled decomp osition were monitored and assessed with the GPR. Schultz (2003) c oncluded that depth and time were the most significant factors in the decom position of the cadavers. Another controlled test conducted with GPR was a simulated archaeologica l site in Illinois. This study replicated features present in some North American archaeo logical sites under a controlled environment (Hildebra nd et al. 2002). Features in cluded pig and dog burials in mounds, isolated pits, hearths, artifact clusters and structures. In addition to the GPR, seismic reflection imaging (SRI) was used. This allowe d the authors to compare geophysical methods based on reflection imaging in anthropogenic soil conditions. Both methods worked well in the study with the GPR providing a more accurate de pth range to target (Hildebrand et al. 2002). A combination of pedological insight with the use of GPR allows for comprehensive site analysis. Distinct change in soil structure or bulk density may enable a GPR operator to distinguish cultural augmentation from natural occu rrences. Surficial features, such as circular trample zones associated with animal feeding ar eas, were identified with time-slice depth maps created by processed radar data (Nishimura and Goodman 2000). A 300-MHz antenna was chosen for a Roman period site in Wroxeter, England as a conse quence of anticipated depth of stratigraphy. This approach in data acquisition increases opportun ity in locating site specific feature characteristics. Prior knowledge of a site’s archaeolo gical component, along with physical soil properties, such as soil texture, can dictate prop er antenna use. Another Roman period building in the United Kingdom was surveyed using GPR; a 450-MHz antenna was chosen over a lower frequency due to the potential signal attenuation in clay-rich soils at great
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29 depths (Linford and Linford 2004). These are two examples of balancing depth of penetration with the potential of known f eature resolution in similar archaeological site parameters. Soils of Florida To understand the limitations and efficacy of GPR in Florida, characteristics and properties of the soil will be discussed. Soil “is a collection of natural bodies on the earth’s surface, which may be modified or created by human activ ity, containing living matter and capable of supporting plants†(Collins 1992). Al l soils are the product of the environment factors in which they are associated. The five soil forming factor s (time, parent material, topography, climate and biota) were described first by Dokuchaev (1883) and later by Jenny (1941). Distinct soil forming factors associated with Florida are reflected in the dynamic and varied soil properties. Resulting pedogenic processes are the basis for describing and classifying soils. Soil Taxonomy Soils in the United States are classified acco rding to Soil Taxonomy (Soil Survey Staff, 1999). Specific information is based on this system of soil classification will be from the Soil Survey Staff (1999), unless cited otherwise. Soil Taxonomy is based on measurable or observable properties of soils as described in the field and labo ratory. Classification indicators include diagnostic subsurface and surface (epipe don) horizons based on physical, mineralogical, morphological, and chemical properties. Soil in dicators are referenced and classified to a maximum depth of two meters, while diagnostic feat ures may be restricted to or exceed this depth. Soil Taxonomy is hierarchical with the following categories from the highest to lowest: (i) Order, (ii) Suborder, (iii) Great Group, (iv) Group, (v) Family and (vi) Series. Soil Orders are the highest and most inclusive categ ory, while the soil Series is the most comprehensive category. The state of Florida has seven of the twelve soil Orders: Alfisols, Entisols, Histosols, Inceptisols,
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30 Mollisols, Spodosols and Ultisols (Collins 1997). Soil Order classification is based on the presence or absence of major diagnos tic surface or subsurface horizons. Diagnostic Surface Horizons All diagnostic surface horizons are termed epipedons, based on the Greek words epi, meaning over or upon, and pedon, soil. Epipedons that exist in Florida are either organic (histic, folistic) or mineral (mollic, ochric, and umbric ). A summary table of the five epipedons in Florida is listed in Table 1-2, with the folistic epipedon not incl uded due to the very specific nature of its classification a nd limited coverage. Diagnostic surface horizons that have been altered through anthropogeni c influences could be considered anthropic epipedons. Understanding diagnostic surface horizons is vita l in determining successful GPR application. Epipedon determination may also establish soil Order classification. Epipedons range in physical, chemical and morphological characte ristics. Physical parameters include mineral and organic soils, while morphological include soil thickness, structure, and color. Chemical diagnostic properties associated with epipedons include base saturation (BS) percentage in cluding cation exchange capacity (CEC), listed in Table 1-3. Particles <0.002 mm in size in Florida have a ne t negative charge. Positive ly charged cations are attracted to these negatively charged surfaces. Mo st of the cations attr acted to the sites are exchangeable. These soil chemical properties have a tremendous impact on the performance of the GPR. According to Daniels (2004) soils with a high CEC are more attenuating to GPR than soils with an equivalent percentage of low CEC. This is similar for soils with elevated levels of BS, more cation activity in the soil will increase attenuation in the GPR.
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31 Table 1-2. Diagnostic summary of the four epip edons used to classify soils in Florida. Epipedon Base Saturation (B.S.) Typical Color (moist) Thickness Organic Content Horizon General Description Histic Low to high. 0100% 10YR 2/1, 2/2 > 20 cm > 12% Organic Saturated 30 days a year Mollic > 50% 10YR 3/3 or less > 25 cm 0.6 to 12% Mineral > 50% B.S. Ochric 0-100% 10YR 4/4 or more < 25 cm 0.6% Mineral Fails to meet definition of all other epipedons Umbric < 50% 10YR 3/3 or less > 25 cm 0.6 to 12% Mineral Similar to Mollic but less than 50% B.S. Table 1-3. Cation exchange capacities (C EC) of soil materials (Birkeland 1999). Soil Material Net Negative Charge (cmol c/kg) Humus (Organic) 100-550 Vermiculite 100-180 Smectite 80-120 Chlorite 15-40 Gibbsite 4-14 Goethite 4-12 Kaolinite 2-5 Histic Epipedon The histic epipedon (from Greek histos, mean ing tissue) is a horizon 20 cm or more thick of organic soil material consisting of either mu ck, peat, hemic or a combination. This organic soil horizon overlies a mineral subsurface horiz on and has a very low bulk density. This epipedon is saturated with water at some period (30 days or more ) of the year and are common in very poorly drained areas in Fl orida. Histic epipedons have high electric c onductivity, high BS and very high CEC, (Table 1-2).
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32 Mollic Epipedon A mollic epipedon is a mineral surface hor izon with high accumulated organic matter content (from .6 to 12 % organic carbon throughout), allowing for a dark brown (10 YR 3/2) to black moist color (10 YR 2/1). Other diagnostic properties associated with a mollic epipedon are it must exceed 25 cm in thickness and have a B. S. greater than 50%. Mo llic epipedons have a high electric conductivity and a high CEC. Umbric Epipedon Morphologically, the umbric epipedon appears to have the same general characteristics as a mollic epipedon; the only difference is the B. S. is lower than 50%. Electric conductivity and CEC are lower than the mollic epipedon. Ochric Epipedon The most common mineral epipedon in soils is the ochric (Collins 1992). The morphological description of an ochric epip edon is a default category by not meeting the classification of any other ep ipedons. This surface horizon do es not have the diagnostic properties associated with other epipedons; it is low in organi c matter and not dark or thick enough to be a mollic or umbric epipedon. Electri c conductivity and CEC have a wide range of values in an ochric epipedon and often tend to be lower than most epipedons. Diagnostic Subsurface Horizons Diagnostic subsurface horizons provide morphological, mineralogical and chemical characteristics that enable the soil to be clas sified. Many of the diagnostic subsurface horizons are defined by clay mineralogy and chemical components. Only 5 of the more than 18 subsurface horizons (Soil Survey Staff, 1999) used to classi fy soils apply to this research and will be considered. All 5 are located in Florida and pertinen t to this study: albic, argillic, cambic, kandic, and spodic.
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33 Albic Horizon An albic horizon is defined by a light-colored horizon of eluviation that is low in, organic matter, clay minerals and iron and aluminum oxide s. This horizon is generally associated above subsurface illuviated horizons in Florida: s podic, argillic, or kandic (Collins 1997). Albic horizons are predominately made up of white to li ght gray sand (ex: 10YR 7/1-8/1) particles in Florida with low electrical conductivity and low CEC. Argillic Horizon An argillic horizon is a subsurface illuvi ation of high-activity silicate clays. The accumulation of layer-latti ce silicate clays in the argillic horizon is due to physical translocation and chemical transformation soil processes. Conc entrations of clay translocated from upper horizons are called argillans. These interstitial cl ay skins often coat and form on the surface of peds and within soil pores between sand and silt pa rticles; it is often th e amount of clay that determines an argillic horizon. An arg illic horizon is an illuvial horizon 15 cm thick in a soil with 15 to 40% clay. Argillic horizons have medi um values of electrica l conductivity and a wide range of CEC. Cambic Horizon A subsurface soil horizon that is weakly develo ped with some color, texture and structure change is classified as a cambic horizon. The ca mbic horizon has very little or no significant accumulation and is characterized by the alterati on or minor accumulation of mineral material. This diagnostic subsurface horizon is weakly to moderately weathered and relates a recent soil genesis. Cambic horizons have moderate to high electrical co nductivities and low to moderate range of CEC.
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34 Spodic Horizon An illuvial horizon having an accumulation of colloidal organic matter, Al, and/or Fe oxides is classified as a spodi c horizon. Spodic horizons are highl y illuviated subsurface soil horizons commonly located in Florida’s pine fl atwood forests. The black or reddish organic illuvial horizon is very acidic. Often spodic horizons in Florida underlay highly eluviated subsurface horizons or mineral and organic ep ipedons. The amorphous accumulation of organic matter and oxides in a spodic horizon will increase the bulk density and lower the pH in relation to surrounding horizons. Soil Orders in Florida According to soil taxonomy there are currently 12 soil orders assigned to soils throughout the world. Soil taxonomy is the classification scheme in use in the United States, and is based mainly on observable properties (B irkeland 1999). A wide range of soil orders (7) are present throughout Florida: (i) Alfisols, (ii) Entisols, (iii) Histos ols, (iv) Inceptisols, (v) Mollisols, (vi) Spodosols, (vii) and Ultisols. Alfisols Alfisols are classified by the subsurface di agnostic argillic horiz on. An argillic horizon and also a thin gray to brown ochric epipedon are commonly associ ated with this soil Order. Alfisols in Florida are characterized by a s ubsurface accumulation of silicate clays (argillic horizon) and have a moderate to high level of bases (> 35%). Alfisols are moderately leached soils that are commonly associated with mixed hardwood forests in well drained to poorly drained soils. Entisols This Order is a very common and morphologi cally diverse group of soils in Florida. Entisols are recently developed or show little if any pedogenic development. Parent materials of
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35 this soil Order range from to a marine, aeolian, or alluvium deposition in Florida. Diagnostic horizons are limited and may include ochric epipe dons and albic horizons, yet argillic or spodic horizons may be present below a depth of 2 m (Collins, 1997, W.G. Harris, personal communication, 2006, Schultz, 2003). Entisols are primarily quartz sand and may range from well to poorly drained soils; the CEC and electric conductivity range of these soils are widely varied as well. Histosols Histosols are comprised of organic soil materi al. Histosols have soil organic material in half or more of the upper 80 cm, or in two-thir ds of a soil overlying shallow rock. Due to the high organic content, these soils are generally black to dark brow n in color and have high waterholding capacities on a mass basis. Not all wetlands in Florida contain Histosols, however all Histosols (except Folists) occur in wetland envi ronments. Common names for Histosols are peat (slightly to moderately decomposed) or muck (highly decomposed). Generally, Histosols have very high amounts of CEC. Inceptisols Inceptisols are the ‘inception’ of soil development with few diagnostic features. Unlike Entisols, Inceptisols show more significant so il development in both surface and subsurface horizons. Umbric and ochric epipedons are very common in this soil Order, yet may have a mollic or histic surface as well. Subsurface horizons, such as albic or cambic horizons are represented with the establishment of a struct ural, textural or color change. Soil properties associated with Inceptisols range from textures of a sandy loam to fine sand, and moderate to high CEC in the clay fraction of recently developed illuvial horizons (Collins 1997).
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36 Mollisols Mollisols are mineral soils which have an accumulation of high organic matter, with a B.S. greater than 50%. All Mollisols have a dark, humus-rich mollic epipedon 18-25 cm in thickness (10 cm over bedrock); however a histic epipedon may overlay a mollic. In Florida, Mollisols have argillic, albic or cambic diagnost ic subsurface horizons. A majority of Mollisols are associated with grassland or prairie envir onments; however, in Florida this soil Order is primarily poorly to very poorly drained condi tions (Collins 1997). High ranges of CEC and low ranges of electric conductivity occur due to the high organic matter and B.S. inherent to Mollisols. Spodosols Spodosols are mineral soils with a spodic hor izon within 2 m of soil surface. Spodic horizons often underlay very leached eluvial al bic horizons, but may have argillic or kandic horizons as well. Epipedons associated with Spodos ols range from ochric to a thin histic. These soils are often sandy, acidic forest soils with low bases and high amounts of Al. Most Spodosols occur in poorly drained pine flatwood regions throughout Florida (Colli ns 1997). Spodosols have low CEC ranges, while electric conductivity ma y be quite high down to the spodic horizon. Ultisols Ultisols are highly weathered so ils with silicate clays and low bases. Intense leaching from upper horizons allow for the translocation of clay minerals into argillic or kandic subsurface horizons. Prolonged leaching of Ultisol s is characterized by a low amount of bases (<35%), relatively acidic silicate clays, and Fe and Al oxides. Ultisols may have either an ochric or umbric epipedon. This soil is commonly associat ed with stable landscapes with mature forest vegetation. Ultisols are morphologica lly similar to Alfisols, but are more highly weathered and
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37 acidic. In Florida, Ultisols range from welldrained to poorly drai ned soils (Collins 1997). Ultisols have low CEC ranges, with moderate electric conductivity. Objectives of the Study The general objective of this research was to demonstrate the efficacy of GPR on anthropogenic sites with selected Florida soils Or ders. The suitability of GPR for archaeological and gravesite detection is not always applicable to pedogeni c models. The purpose of this research is to assist archaeologists and GPR operators to better unde rstand the context of anthropogenic influences on natural soils. Conduct GPR surveys to obtain information a bout the selected arch aeological sites and cemeteries in Florida Establish the extent of archaeological and cem etery soil properties in producing distinctive anomalous responses. Document resolution differences between 900-MHz and 500-MHz GPR antenna usage for obtaining anthropogenic ta rgets in study areas. Determine the suitability of GPR on various Fl orida soil Orders in an archaeological and gravesite context by demonstrati ng the influences of soil physic al and chemical properties.
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38 CHAPTER 2 FIELD SITES Study Site Selection Four sites were studied to evaluate the appli cation and feasibility for the use of GPR in an archaeological and cemetery context in the NorthCentral and Central Flor ida (Figure 2-1). Field sites were based on archaeological context and soil variability. Archaeol ogical sites included a prehistoric habitation site in Lake County on the shore of Lake Apopka and a historic structure site in St. Johns County, north of St. Augustine. Th e two historic cemeteries date from the latenineteenth century in Orange County to the ea rly and mid twentieth cen tury in Alachua County. Both the Orange and Alachua County sites are associated with African-American cemeteries. These study areas were based on four different soil Orders. In Fl orida soils there are contrasting subsurface features, i.e. argillic ho rizons, spodic horizons, layers (organic); lithic (bedrock) contacts; wetting fronts; and lamellae that are easily exhibited by GPR (Collins 1992). The properties from a majority of Florida soils are conducive to the use of GPR (Collins et al. 1996, Doolittle et al. 2002). The four field study s ites selected will elucid ate potential concerns for the use of GPR when applied with soil properties in an anth ropogenic context. Newberry Cemetery Description The Newberry cemetery (Davis Cemetery 8AL49 92) is located in Section 34 of Township 9, Range 17 East in western Alac hua County, Florida. This site lies east of the Brooksville range on the Wicomico terrace; underlain by alternately thick layers of Plio-Pleistocene material overlying loamy marine sediments and limestone bedrock (Thomas et al. 1985). Part of the Alachua Formation, the Newberry Cemetery site area is in the southwes tern part of Alachua County, where it forms low and rolling hills (T homas et al. 1985). The substrate materials
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39 represent the residuum of pos t-Eocene formations (Schmidt 1997). This area has been extensively mined for rock. This formation vari es in depth from 8-12 meters (Thomas et al. 1985). Naturally occurring vegetation in this area includes: live oa k (Quercus virginiana), laurel oaks (Quercus laurifolia) and wate r oaks (Quercus nigra) ; longleaf pine (Pinus palustris) and saw palmetto (Serenoa repens). Figure 2-1. Location of resear ch sites in Alachua County, Lake County, St. Johns County, and Orange County, Florida. Soils The soils at the Davis cemeter y are well-developed Alfisols (Thomas et al. 1985). They are mapped as PedroJonesville complex, with va rying depths of argillic horizon; which are so Newberry Cemetery St Johns County Historic Site Lake County Prehistoric Site Oakland Cemetery N
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40 200 Meters 40 Meters Transect 17 Transect 14 200 Meters Site area intermixed, that they cannot be separated at the scale of mapping (Figure 2-2). Mapped areas of the complex range from 10 to 50 hectares. Pedro soils are fine-loamy, siliceous, Figure 2-2. Soil survey map showing soil series and complex at the Newberry cemetery. The map was created in ArcGIS 9.1 using data derived from the Alachua County Soil Survey (Thomas BP, et al. 1985). hyperthermic, shallow Typic Hapl udalfs. The thickness of the solu m and the depth to limestone range from 15-45 cm. The other soil in this comp lex is the Jonesville series; loamy, siliceous, hyperthermic Arenic Hapludalfs. Mapped as a complex, the major difference between the Jonesville soil as compared to th e Pedro soil is the depth to limest one. Both soils have an argillic horizon which is from 32-72 cm in depth. Depths to limestone and the argillic horizon greatly vary within the site. An example of depth to lim e rock variability for Alachua County soils is in Figure 2-3. Overall, this complex has severe limitations for cemetery use. N
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41 Figure 2-3. Soil depth to limer ock variability of an Alfiso l in Alachua County, Florida. Cultural history Three headstones were identified in a heav ily wooded area north of Newberry, Florida along transects 14, 17 and 21 in Figure 2-2. In additi on to the marked graves, four suspect graves were located in immediate vicinity; two linear de pression and two uninscribed marble footstones. All three marked graves were inscribed with name , date of birth and date of death. The graves were identified bearing the names Catherine Al ridge, Willies Davis, and W.J. Long. The earliest recorded date of death was Willie Davis on Fe bruary 14, 1892. Catherine Alridge was the most recent grave, dated to June 4, 1918. All marked graves and linear depressions were in an east to west alignment, denoting a Wester n Christian burial pa ttern. Gravestone type and dates of the four marked graves are in Table 2-1.
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42 Table 2-1. Graves at the Newberry Cemetery. Pr eliminary Report, Southeastern Archaeological Research, Inc. Gainesville, Florida. Name Date of Birth Date of Death Gravestone Type Material Catherine Alridge 1832 June 4, 1918 Rounded Marker Marble Willie Davis May 14, 1818 February 14, 1892 Shouldered Marker Marble W.J. Long May 1867 August 14, 1916 Rounded Marker Marble Historic research conducted by Southeastern Archaeological Researc h, Inc. (SEARCH) in the area was inconclusive as to the original name of the cemetery. No known churches or homesteads with common last names were connect ed with the Davis Cemetery. No information could be found on Catherine Alridge or Willie Davis, while only one report of W.J. Long (black male) places him in the Newberry area during th e year of 1916 (SEARCH 2005). Historic deed research of the Davis Cemetery area indica ted that in the first decade of the 20th century the property was owned, but not developed, by the Florida Land Development Company and was sold on July 14th 1910 to the Mutual Mining Compa ny of Marion County (SEARCH 2005). Located in a mixed hardwood hammock, this si te area has a high canopy with little under story growth. North of the graves are three small cedar trees. Cedar trees were typically planted near the periphery of cemetery boundaries during the late 19th and 20th century in Florida. The cemetery boundary is identified to be no larger than 32 m east to west and 25 m north to south. During the time of the research at this site area a 27 m preservati on buffer zone was put in place. No protective fences or markers are located around the heavily w ooded area. A town facility is adjacent to the Davis Cemetery. As of the fall of 2006, this cemetery does not meet the criteria for eligible inclusion in the National Register of Histor ic Places (NRHP).
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43 Oakland Cemetery Site Description Located in Orange County, Oakland Cemetery (OR9576), also known as the Old African American Cemetery, is situated in Section 20 of Township 22, Range 27 East. This site lies south of Lake Apopka in the southern end of the Ce ntral Valley. The Lake Apopka area is underlain by undifferentiated Plio-Pleistocene sediments a nd sedimentary deposits of the Hawthorn Group overly the upper Eocene limestone (Doolittle and Schellentrager 1989, Schmidt 1997, White 1970). The geomorphology of the site area is at th e interface of the Central Valley and Lake Wales ridges, part of the Wicomico Terrace (Doolittle and Schellentrager 1989, White 1970). Topographic variability, associated with the Cent ral Valley and Lake Wales ridge, range from a 5-12 % slope in the site area (Fi gure 2-3). Natural vegetation is predominately live oak (Quercus virginiana), bluejack oak (Querc us incana), turkey oak (Quercus laevis), and sand pine (Pinus clausa). Surrounding site area ha s been used for citrus crops during the past century. Soils Oakland Cemetery is predominately comprised of Entisols and Ultisols, and is mapped as Candler-Apopka fine sands with 5-12% slopes a nd adjacent, depressional Basinger fine sands (Doolittle and Schellentrager 1989). The Candler -Apopka complex is an excessively drained soil. This soil complex is associated with uplan ds and low ridges (Figure 2-4). Candler soils are classified as hyperthermic, uncoated Lamellic Quar tzipsamments; they form in thick deposits of aeolian or marine sand. Similar in pattern and pr oportion to the Candler, th e Apopka soil series is a loamy, siliceous, hyperthermic Grossarenic Paleudult. This soil complex is widespread throughout the site area. The indivi dual soil series cannot be di fferentiated on a small scale and are therefore mapped together as a complex.
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44 125 Meters Transect2 Survey area Basinger Soil Series Candler-Apopka Soil Complex Figure 2-4. Soil survey map showing the Candler-Apopka soil comp lex at the Oakland cemetery. The map was created with ArcGIS 9.1 using data derived from the Orange County Soil Survey (Doolittle and Schellentrager 1989). Apopka consists of well drained soils that formed in sandy and loamy marine sediment. Both the Apopka and Candler soil series are mor phologically very similar in the upper meter of each horizon (see Discussion). The Basinger series is classified as a siliceous, hyperthermic Spodic Psammaquents; which form in sandy marine sediment. These poorly drained soils are in shallow depressions and along the r im of larger depressions. An ex ample of a Florida Entisol soil is in Figure 2-5. The homogenous matrix of the C horizon is evident in the uniform subsurface radar profiles. N StateRoad50 Florida Turnpike
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45 Figure 2-5. Photograph of an Entisol profile in Florida. Cultural History The Old African American Cemetery is located north of the State Road 50 and Florida Turnpike intersection. Along the south border of th e cemetery is the remnant of the Tavares and Gulf Railroad (1891-1971) roadbed. No longer an active cemetery, approximate dates of early graves are from the early 1890’s. The last known graves are from as late as 1952. The cemetery was not affiliated with any reli gious organizations and African Americans from the surrounding communities were also buried in the cemetery (S EARCH 2005). Both the citrus crops and the railroad line facilitated an influx of migrant work ers in the area. Many of the people buried in the cemetery were citrus farmers and service worker s. Also, if any of the migrant workers or possible transients died while in the area, th ey were buried in the cemetery as well (Deacon Entisol A C1 C2
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46 Moore 2006: personal communi cation). Census searches revealed most of those buried in the cemetery are originally from North or S outh Carolina and Georgia (SEARCH 2005, Florida Census 1920). African American burial practices associated with this site had a significant relationship with results of the GPR surv ey and will be discussed in Chapter 5. Historic Archaeological Site Description This British Period occupation site area is lo cated west of the Tolomato River and north of Marshall Creek in St. Johns County, Florida. The site (8SJ3149) lies within the Atlantic Coastal Lowlands and is less th an one-half mile west of th e Atlantic Ocean on the Pamlico terrace. This area was formed as barrier islands and lagoons from the Plio-Pleistocene to recent times (Davis 1997). Silver Bluffs and Pamlico terra ces occur in this interc oastal area. Physical environment is dominated by pine flatwoods, hardwood hammocks and salt marshes. Hammocks within the Marshall Creek property are associated with th e bottomland hardwood wetlands that border the coastal salt marshes. Soils The soils mapped in the site area are weakly to moderately developed Spodosols with associated Entisols; and are classified as eith er Myakka or Immokalee (Spodosols) soils (Readle 1983). The Myakka-Immokalee complex is a nearly level, poorly drained sandy soils located on flat marine terraces in broad flat wood areas (Figure 2-6). Most of the soils in this complex have loamy to sandy subsoils that are stained with da rk organic accumulations. The Myakka series is Florida’s state soil and is classified as a sandy, siliceous, hyperthermic Aeric Alaquod. Immokalee soils are classified as sandy, silice ous, hyperthermic Arenic Alaquods (Figure 2-7).
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47 Figure 2-6. Soil survey map showi ng soil series and complex at th e historic archaeological site. The map was created with ArcGIS 9.1 using data derived from the St. Johns County Soil Survey (Readle 1983). 200 Meters 200 Meters HAAS Transect 1 HANS Transect 1 Site area Immokalee Soil Series St. Johns Soil Series N Myakka Soil Series
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48 Figure 2-7. Photograph of an Immokalee soil series profile. Cultural History The Tolomato River and Marshall Creek area s have varied historic and prehistoric archaeological components. Multip le phases of the St. Johns cultu re occupied northeast Florida from around 500 B.C. and lasted until shortly afte r permanent historical settlements occurred in 1565 A.D. (Milanich 1994). A European power struggle of French and Spanish interests occurred in the St. Johns River area during the mid-16th century (Contact Period: from 1565 A.D.). In 1565 the Spanish, led by Pedro Menendez de Aviles dispatched the French and A E2 E1 Bh
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49 established St. Augustine. Chosen for its strate gic location, St. Augustine existed as a military outpost and a base for missionaries for the ar ea (Deagan 1983). The First Spanish Period (15651763 A.D.) in northeast Florida was a rural mix of Franciscan missi ons, Indian villages, Spanish cattle ranches and military fortifications (B ond et al. 1990, SEARCH, 2005). During the British Period (1763-1784 A.D.), rural construction in nort heast Florida increased; plantations, industrial construction, trading posts, sl ave cabins and planta tion houses developed throughout the region (Bond et al. 1990, SEARCH, 2005). Numerous excavations were conducted in the Marshall Creek (8SJ3149) area over the last decade. Extensive amounts of information have b een collected on both prehistoric and historic archaeological components from the site area. Archaeology on 8SJ3149 was conducted in order to mitigate development in the vicinity. Multiple scientific disciplines were employed to facilitate the survey and excavation of this site. Prehistoric Archaeological Site Description This prehistoric archaeological site is known as the Montverde site (8LA243), located in the town of Montverde in Lake County, Florida. The s ite is situated in an agricultural area on the west side of Lake Apopka (Figure 2-8). The site 8LA243 is bordered to the east and north by the lake, and to the northwest by a freshwater ma rsh. The geomorphology of the area includes PlioPleistocene sediments overlying Hawthorn deposits and upper Eo cene limestone (Doolittle and Schellentrager 1989, Schmidt 1997, White 1970). La ke Apopka lies in the Central Valley, associated with the Lake Wales and Winter Ha ven Ridge along the Wicomico terrace (White 1970). The well-drained soils and proximity to La ke Apopka (Figure 2-9) was conducive to long term citrus cultivation at the site area. Natural vegetation includes live oak (Quercus virginiana),
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50 turkey oak (Quercus laevis), longleaf pine (Pinus palustris), slash pine (Pinus elliottii), and saw palmetto (Serenoa repens). Figure 2-8. Photograph of an excavation at the prehistoric archaeological site along the southwest shore of Lake Apopka, Montverde, Florida. Soils Two soils are mapped with the site area; a we ll-drained Orlando series and a very welldrained Entisols classified as the Lake soil se ries (Furman et al. 1975). Predominately, the site associated with the Orlando series (Figure 2-6). This series is classifi ed as a sandy siliceous, hyperthermic Humic Psammentic Dystrudepts. The Orlando series is a nearly level to gently sloping (0-5%), well-drained sa ndy soils in association with upland ridges. This Inceptisol formed in sandy marine sediments and has a thick umbric epipedon. The other soil in the research site is the Lake series; classified as a hyperthermic, coated Typic Quartzipsamment.
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51 Figure 2-9. Aerial photograph ( 1999) of the prehistoric archeo logical site at Monteverde showing shovel tests and test unit locati on (Austin 2006). Shovel tests and excavation units were conducted prior to survey by S outheastern Archaeologi cal Research Inc. Soil series information derived from Lake County Soil Survey (Furman et al. 1975). The Orlando and Lake soil soils make up 93 to 99 percent of mapped areas with marine sediment on upland slopes of 0-5% (Furman et al. 1975). Cultural History Previous excavations in the Montverde site area have indicated the presence of two archaeological components. Upper levels of th e excavation units contained St. Johns Check Stamp pottery, indicating a St. Johns II occupation site; while the lowe r levels appear to be a St. PA NSTransect PAASTransect2 OrlandoSoilSeries Survey area
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52 Johns I period, dominated by St. Johns Plain ceram ics (Austin 2006). The organic midden base is an early St. Johns I period with related features dating from as early as 1600 B.C.; while dates within the midden go up to 400 B.C.(R. Aus tin, personal communication, 2006). Two cultural features were identified in an excavation unit as circular, basin-shaped pits with fragments of burned wood in the sandy fill (Austin 2006). The burned wood associated with pit features allowed for accurate 14 C dating.
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53 CHAPTER 3 MATERIALS AND METHODS Site Criteria Each field site area was selected on the ke y variables of temporal component, spatial extent, pedological criteria and availability for research. Every site was to be represented by a soil Order in Central Florida and not to exceed a surv ey size of 2 hectares. Selected sites were to reflect field conditions encount ered during standard operatin g archaeological surveys and excavations. Every field site c ontained an element of bioturba tion and anthropogenic influence of varying degrees. A common element in all four research areas were the materials used and the methods employed. Each individu al site will include : archaeological field work, GPR survey, soil sampling and description. Equipment and soft ware used and soil analyses conducted were identical for all four sites. Equipment and Software: All four field sites were surv eyed with the same GPR system: SIR-2000 control unit with 500 MHz and 900 MHz ground-coupled monostatic, dipole antennas with control unit (Geogr aphical Survey Systems, Incorporat ed, North Salem, New Hampshire). Both antennas have marker switches located on the handle and manually controlled by the antenna operator. The control unit is a digital pulse system, with internal hard drive, keypad and color screen. GPR files may be viewed real-time in the field or data may be downloaded to an external computer. Each antenna is connected to the control unit by a 60-m eter cable. A twelvevolt battery powers the GPR unit. Multiple software packages were used in the field and laboratory for GPR, Global Positioning System (GPS) and Geographic Informa tion System (GIS) data calculation. For all four sites, GPR files were downloaded from the field to the comput er for post-processing analyses with Data Transfer Utility for Wi ndows 95 and Windows NT, proprietary software of
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54 GSSI (Geophysical Survey Systems Inc.). Post-p rocessing analyses for th e manipulation of GPR data of all sites were conduc ted using the same computer so ftware package (ReflexW 2.5X, Sandmeier Scientific Software, Karlsruhe, Germ any). The primary GIS software package used was ArcGIS 9.1 (Environmental Re search Institute, Redlands, CA .). Two different GPS devices were used in the acquisition of spatially refe renced data, TOPCOM 3C total station with TOPCOM SC data collector. The Garmin etrex VistaTM handheld GPS receiver was also used. Soil Sampling Soil samples were collected on site specific criteria. Collection of anthropogenic soils samples was uniform in depth and quantity within each site area. Physical data acquisition and soil sampling was done with a bucke t auger (8 cm diameter and 17 cm in length). Archaeological field sites incorporated both bucket auger a nd hand trowel during excavation. Auger samples were taken with a bucket auger, which was f ound to pack and hold a greater range of soil textures encountered from all four site areas. So ils were described and sa mpled up to a depth of 2 meters for every site. Anthropogenic soils were described on a site specific basis, with no maximum depth requirement. Soil samples of approximately 400-500 g each were collected in the field and placed in labeled plastic bags. Soil descriptions were reco rded and sample bags were returned to the University of Florida Environmental Pedol ogy and Land Use Laboratory. In the pedology laboratory, soil color was determined by visual comparison on moist samples to a Munsell Soil Color Book (GretagMacbeth, 2000). Morphological descriptions fr om the field and from NRCS soil survey data were augmented with laboratory data and are listed in Appendix A. Appendices B and C list the physical and chemical data from each site.
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55 Two types of sampling increments were us ed for anthropogenic and pedogenic soils: 1. Natural soil samples were taken from each de signated genetic horizon revealed in auger samples for morphological descriptions and lab analyzed in the laboratory. 2. Anthropogenic soils sampled were taken from 20-30 cm interval (depth) samples for physical and chemical analysis from surface to appropriate depth. Soil Analyses Procedural analyses for all soil samples of the four site areas were id entical. Processing of soil samples was done at the same time, using the same equipment and environmental conditions. Samples were air-dried, screened through a 2-mm sieve, and stor ed in Analytical Research Laboratory (ARL) approved soil sample bags. Each of the 232 collected soil samples was assigned an individual catalogue number for use in laboratory te sting and curation. Site specific identification numbers (e.g., 8LA243: 8 = state of FL, LA = Lake County, 243 = site #), included the provenience descriptions. Soil samples were subject to physical and chem ical analyses. Specific analyses included: particle size, pH, organic car bon (OC) content, electrical co nductivity (EC), extractable aluminum (Al), extractable iron (Fe), extracta ble phosphorus (P), extractable magnesium (Mg), extractable sodium (Na), extractable calcium (Ca) and extractable potassium (K) contents. Particle-size analysis was used to determine the percentage of sand, silt and clay for textural classification and subsequent sand fractionation. Soil pH is known as the “master variableâ€; this test is done in order to unders tand the chemical range and parame ters within the soil. The amount of OC was determined to diffe rentiate between a mineral soil (<12%) and an organic soil. The percentage of O C may also gr eatly influence the taxonomic clas sification of a soil, chemical properties and indicate the pr esence archaeological middens. Amounts of extractables P, Ca , Na, Mg, K, Fe, and Al were analyzed to determine the extent of anthropogenic influences on a pedol ogic landscape using the GPR Archaeologists have
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56 used soil chemical analyses as both a temporal and spatial indicator of site habitation. Soil chemical testing of the four bases (Na, Ca, K, and Mg) along with the tw o acid cations (Al, Fe) will allow for an increased understanding of natura l and anthropogenic site context. Extractables P and Ca were analyzed to determine if bone diagen esis occurred in the site areas; both P and Ca are the two most common minerals in bone (Schultz 2003). Distri bution of extractable P is a good indicator of anthropogenic activity, becaus e mean extractable P is notably lower in naturally occurring soils. Physical Analysis All particle-size an alysis was conducted at the En vironmental Pedology and Land Use Laboratory, Soil and Water Science Department, at the University of Florida. Particle-size distribution analysis was c onducted using the pipette method (Gee and Bauder, 1986). Soil samples of 50 g were treated with hydrogen pero xide and heated on hot pl ates to oxidize organic material. The samples were then dispersed with sodium hexameta phosphate in de-ionized water. Dispersed samples were immersed in a 20 C wate r bath and pipetted to retrieve the clay fraction. The clay fractions retrieved were drie d and weighed. Sand fractions were obtained from the original sample and removed of remain ing silt and clay, then oven-dried and shaken through nested sieves. Silt content was derived by the subtraction of sand and clay weight from the total sample weight. Chemical Analysis Organic carbon content, pH, EC , extractables P, Fe, and Al were all analyzed at the Analytical Research Laboratory, Institute of Food and Agricultural Sciences, Soil and Water Science Department, at the University of Flor ida. OC content was determined by a modified WalkleyBlack method of dichromate sulfuric acid (Soil Survey Staff, 1996). The calculation of pH was done by 1:2 water to soil solution by glass electrode of pH meter and deionized water.
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57 EC was determined by 2:1 deionized water to soil solution using a glass electrode. This procedure was done because EC is directly re lated to the amount and distribution of ionic charges in the soil (McNeill, 1980). The procedure to determine extractables P, Al, and Fe was using a Mehlich 1 extraction (Mehlich, 1953). This procedure entails 5 grams of soil sample to be added to 20 ml Mehlich 1 solution (0.05 M HCL and 0.0125 M H2SO4 ). The solution and sample are shaken for 5 minutes and filtered through Whatman # 42 paper. The extrac t is then analyzed by an inductively coupled plasma-atomic emission spectroscopy (ICP-AE S) (EPA Method 200.7, Analytical Research Laboratory 2006). Mehlich 1 was also used for the analyses of extractables Ca, K, Mg, and Na; the extract is analyzed by atom ic adsorption spectroscopy (AAS). Statistical Analysis Statistical analyses of the data was based on a standard two-tailed, pa ired t-Test. Analyses of the soil data with a t-Test was used to dete rmine whether two soil samples were likely to have come from the same two populations that have the same mean. The de pendent variables are based on the pedogenic soils from the site. An thropogenic soil samples are the independent variable, measured with the dependent pedogenic soil samples. Data from physical and chemical soil properties sampled from the site associated with GPR transects. The two-tailed t-Test was performed to determine if soils from a potential anthropogenic site corresponds to the probability of the known values of the pedogenic site. The sta tistical program used to perform the standard two-tailed, paired t-Test was the Microsof t Office Excel 2003, st atistical functions. GPR Data Collection Each research site was cleared of underbrush prior to GPR survey. Cleared transect paths allow for an uninterrupted flow of data co llection; thereby minimizing post-processing corrections. Datum points were acquired for ev ery site by a TOPCOM 3C total station and
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58 TOPCOM SC data collector. Reference points we re recorded from the datum points located in the southwest corner of each site. A hand held GPS receiver was used to correlate spatial coordinates of transects emanating away from the datum points. The GPS handheld receiver was used along transects in all f our field sites. Signal error due to tree canopy obstruction was minimized by the GPS receiver being placed over known coordinates and physically rectified by pull tape. GPR transects for each site were collected in single line grid formation emanating from datum point coordinates. A 100-meter pull tape laid out each transect in a north-south direction. Direction and distance were corrected w ith the use of GPS and hand held SUUNTOTM sighted compass. Pin flags were placed every one to tw o meters along each transect. Transects were spaced in one-meter interval grid patterns. A one meter distance between transects was necessary for complete site coverage with GPR. An ante nna was walked along each tr ansect and referenced with corresponding intermediary tr igger-switch marks associated wi th measured pin flag points. The antenna was pulled along the sa me side of the line for consis tency. All sites received the same spatial reference methodology. Each site contained different and varying soil properties, a nd thereby required different range settings and RDP calibrations to de termine time-depth conversions. An accurate conversion of two-way travel time to depth is ne cessary before the interpretation of data can commence. Time-depth calculation was determined by auguring to a known depth just off-site. At one and two meter depths, water was added to the base of the auger hole and immediately geo-referenced with the GPR with both 900-MH z and 500-MHz antennas. Ranges and dielectric constants were established and set on each individual site location and date from this information and referenced with known RDP ranges.
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59 GPR Analysis Analysis of GPR data often is conducted in a two-step process. The GPR technology used in this research allowed for real-time data viewin g in the field. This enabled the operator to take corrective measures in equipmen t calibration and survey technique . In the field, GPR data files were viewed using a Color Table of 2 and Color Xform of 2. These visual screen settings are qualitative and subject to viewer preference for optimum data in terpretation. Field interpretation of visual GPR data was consider ed the preliminary step for over all data acquisition. Often times transects were discounted and field data were reacquired based upon preliminary field observations. Raw field data co ntain extraneous background nois e or reflections that make definitive interpretations difficult. Horizontal scale and vertical scales are often not coordinated effectively in non-processed data. GPR Post-Processing Analysis Post-processing is an important step in GPR analysis and interpretation. Qualitative assessments are greatly enhanced with the manipulation of GPR data; often images and anomalies are not clear to the operator until the da ta has been processed. Interpretive strategies and procedures for the processing of GPR data are numerous. There are fundamental procedures in the rectification and manipul ation of data sets. Spatial ad justment, both vertically and horizontally, along with background filtering ar e primary procedures often employed by the operator. Processing of GPR prof iles required a minimum 4 differe nt procedures in order to interpret the raw data. Horizontal adjustment was the first procedur e for every GPR file. Linear correction is necessary because the GPR antenna is not pul led across a transect at a constant speed. Intermediary marks were created at prescribed intervals along each transect during the collection of data. The known distances between each interval allows the software to the correct distances
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60 between each mark. This step was a trace interpol ation/resorting procedure. Vertical correction was the next step taken for proper depth. GPR antennas are housed in a fiberglass box and suspended above the ground surface. The actual distance between the antenna and the ground is seen as an ‘antenna ringing’ noi se that can be corrected. This ‘ringing’ is seen as a uniform reflection image and is included in the original da ta as part of the profile depth. Elimination of this noise will set the time transm ission depth at 0 ns, as 0 mete rs; this is done through gain compensation. After vertical and horizontal adjustments are made, filtering the files of horizontal banding is done. This process allows for enhanced view ing of anomalies and th e removal of unwanted clutter. Radar attenuation is filtered out, leaving continuous pedogenic horizons, planar and point-source anomalies. This procedure is a combination of a running and background removal process. Study Sites Newberry Cemetery The Alfisols at the Newberry Cemetery are no t considered highly suitable soil orders in Florida for GPR application (Collin s et al. 1996). Thus, GPR use for this site is not ideal from a pedogenic context. However, this site was select ed for availability, pe dogenic diversity from other selected soil orders and for the comm unity need. The area is heavily wooded and surrounded by planted pine. Cemeteries are confin ed to area no greater than 500 sq m; coupled with a strict temporal range of less than 30 years. There are numerous occurrences of bioturbation throughout the site that include animal burrows (kroto vinas), tree stumps, root ball inversion and roots. These subsurface anoma lies are detected by the GPR and have varying influences on both the 900-MHz and 500-MHz antennas.
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61 A total of 24 transects were conducted in the cemetery every meter. Each transect was 20 m in length with marker flags placed every tw o meters for reference points. The general cemetery area surveyed and staked at 27 m east to west and 21 m north to south by a previously contracted survey team (Table 3-1). GPR surv eys and soil sample colle ctions were conducted several times over a five-month period (O ctober of 2005 to February of 2006). Table 3-1. Data points for the four corners of the cemetery boundary. The projection system used was UTM, NAD 1983, Zone 17 North. Northwest Corner: 17R 0344765 W 3283016 N Northeast Corner: 17R 0344786 W 3283015 N Southwest Corner: 17R 034464 W 3282990 N Southeast Corner: 17R 0344886 W 3282989 N Oakland Cemetery The selection of Oakland Cemetery as a research site was a combination of soil suitability, anthropogenic criteria and the need fo r mitigation before future development in the area. The presence of unmarked graves outsi de the cemetery boundaries was not known by the town residents or the local, affiliated church. A survey was conducted in order to determine if any unmarked graves existed outs ide the historic boundaries of th e Oakland Cemetery. This was achieved through a combination of archived aerial photographs (Figure 3-3), ethnographic accounts and a GPR survey. On the eastern shoulder of the site area is a transition from the Lamellic Quartzipsamment (Candler) down slope to the Gro ssarenic Paleudult (Apopka). Both of these series are ideal soils orders in Florida for GPR applications in a pedogenic context (Colli ns et al. 1996). Typical vegetation of these soils is sand pine (Pinus clausa), slash pine (Pinus elliottii), chapman oak (Quercus chapmanii), live oak (Que rcus virginiana, and saw palmetto (Serenoa repens). The area is subject to krotovinas. At th e base of the slope is a Spodic Psammaquent (Basinger), which is
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62 seasonally flooded for extended periods of tim e. Naturally occurring vegetation includes pondcypress (Taxodium ascendens), sweetgum (L iquidambar styraciflua) and scattered pond pine (Pinus serotina). Figure 3-1. Aerial photograph of Oakland Cemetery from 1947. Site boundary is highlighted in red. A GPR survey was conducted along the histor ical boundaries of the Oakland Cemetery. Transects emanating outward from known graves were completed in a grid pattern. Each transect was separated by a meter and reference points were placed every 5 meters. The large scale of this survey was augmented by a number of volunteers, w ho were able to place pin-flags on suspected anomalies during the data collecti on. A total of 7 suspected unmark ed graves were located in the N 100m
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63 course of three days of surveying. The site was stak ed with survey markers (T able 3-2) in all four corners prior to the GPR survey. Table 3-2. Data points for the four corners of the cemetery boundary. The projection system used was UTM, NAD 1983, Zone 17 North. Northwest Corner: 17R 0437596 W 3158418 N Northeast Corner: 17R 0437696 W 3158417 N Southwest Corner: 17R 0437596 W 3158285 N Southeast Corner: 17R 0437696 W 3158347 N Historic Archaeological Site Research interest in the Mars hall Creek site (8SJ3149) was based primarily on the historic occupation component. The field site in St. Johns County cont ained Spodosols and peripheral Entisols, which are two of the best soils orders in Florida for GPR app lications in a pedogenic context (Collins et al. 1996). The area is h eavily wooded with nume rous occurrences of bioturbation that throughout the s ite that include; animal burrows (krotovinas), tree stumps and roots. Large areas of underbrus h were cleared to prepare the site and restrict the unwanted influences of the GPR survey. Both the 900MHz and 500-MHz antennas were used and had varying influences on subsurface detection. The research site at Marshall Creek wa s a collaborative effort with SEARCH. Archaeological excavations were conducted in th e area over a six-year period. A small scale GPR survey was conducted in the August 2005 in a known multi-component site area. GPR data collection was confined to 100 m2 area adjacent to a block exca vation. The excavation units were placed near previously tested units which cont ained abundant British period materials (Carlson 2005). The coordinates of site area is shown Table 3-3. A total of 16 transects were placed in a gr id pattern and ran in both north-south and eastwest directions. This was conducted to achieve a greater spatial context of any possible historic features. Transects were 3 to 5 meters in length with half-meter interval s. Interval distance was
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64 reduced due to the depth of potential targets a nd smaller elliptical ra diation footprint. GPR surveys and soil sample collections were c onducted two times over a period of one month. Table 3-3. Data points for the four corners of the historic archaeological survey area. The projection system used was UTM, NAD 1983, Zone 17 North. Northwest Corner: 17R 0463935 3322503 Northeast Corner: 17R 0463926 W 3322502 N Southwest Corner: 17R 0463933 3322494 Southeast Corner: 17R 0463925 3322493 Prehistoric Archaeological Site Preliminary archaeological work at the Mont verde site (8LA243) wa s conducted in 2004 due to possible future development. Independent to the research work, a contract archaeological firm (SEARCH) began testing with a subsurface survey of 87 shovel tests throughout the project area. Prehistoric artifacts were recovered from 50 shovel tests; the center and the southwest corner of the grove were the only areas void of cultural material (Austi n 2005). Excavations units were then placed in areas of high artifact concen tration, along the eastern project area. The units were situated between the citrus grove edges a nd the lake shore. The si te area extends about 25 hectares across an active orange grove. The site area has a marked slope (>5%) from west at 36 m to the lake shore at 21 m above mean sea level. The scope of the GPR research site area was confined to pote ntial archaeological concentrations. A GPR survey was conducted from the block excavation areas between previous T.U. 1 and T.U. 2. The survey began from an Orlando series (Inceptisol) and continued upslope in to the Lake series (Entisols). A total of 24 transects were conducted in an east to west direction in order to determine the transition of the umbric epipedon to an ochric epipedon. Transects were one meter apart and restricted in grid size due to presence of orange trees, and were referenced off existing excavation un it datum points and handheld GPS receivers.
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65 CHAPTER 4 RESULTS Results of interpreting GPR profiles and soil an alyses are separated into sections covering the four research sites. Each section will include: (i) physical a nd (ii) chemical analyses of anthropogenic and natural soils, (iii) GPR prof iles with the 500-MHz antenna and (iv) 900-MHz antenna of anthropogenic and natural soils. Compar ison of all four sites will be covered in the discussion chapter. A summary of morphological pedon descriptions and selected physical and chemical properties are given in Appendices A and C. Additional GP R profiles suing the 500MHz and 900-MHz antennas are given in Appendix D. Newberry Cemetery Located in western Alachua Count y, Florida, the Newberry cemetery was selected for this study based on soil Order (Alfisols) and on anth ropogenic context. Research was conducted to see the effect of the soil on GPR to detect unmar ked graves. In order to asses the suitability of GPR with the soil properties, two different frequency antennas (900-MHz and 500-MHz) were compared during the survey. The soils from the site area are mapped as well developed Alfisols (Thomas et al. 1985). These soils are classified as a PedroJonesville complex, with varying depths of argillic horizon; which are so intermixe d, that they cannot be se parated at the scale of mapping (Thomas et al. 1985). The marked graves are from the early twentieth century; several unmarked graves are located with in proximity of only a few meters . This site addressed several objectives of the study: the application of GPR to verify the existence of a clandestine grave while meeting the criteria of a specific Florida soil Order. Soil Physical Analysis Particle-size distribution of nativ e soils at this site indicated soil texture ranging from fine sand to clay textures. The Newberry cemetery na tural soils (NCNS), native Arenic Hapludalfs,
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66 were approximately 91% medium to very fine sand throughout the A and E horizons, with less than 4% silt or clay. The Ap horizon had a silt content of 3.5 % w ith a decrease to 2.3% in the E horizon. The amount of clay increased from < 4% in the Ap and the E horizons to >21% in the Bt horizon. The silt content increased to < 6% in the Bt horizon for the native soils. The particle-size distribution of the Newb erry cemetery anthropogenic soils (NCAS) ranged from medium grain sand to a clay frac tion. The mixed horizons of the NCAS varied widely in particle-size dist ribution. Soils from suspected surveyed graves were ranged approximately from 86% to 91 % medium to very fine sand in the Ap horizon, with ranges of 4%-6% silt and 3%-6% clay. Soils from the altered E1 horizon (45-60 cm) had a backfill scattering that ranged from 11.6% to 42.2% clay. (Figure 4-1). 0 5 10 15 20 25 30 35 40 450-15 (A)45-60 (E1)83-98(E2)130-142(Bt)Depth (cm)Percent % Clay (Anthropogenic) % Clay (pedogenic) Figure 4-1. Depth distribution of total clay c ontent of natural (trans ect 17) and anthropogenic (transect 14) soils at the Newberry cemetery. Medium to very fine sand ranged from 64.2% to 85.1% and the silt content was 5%-6% in the soil from the anthropogenic altered E horizon. Clay content increased in the associated Bt horizon in the anthropogenic soil to 41.2%. When the percentage of clay is compared with depth, clay increased in the NCAS at 45-60 cm along transect 14
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67 Soil Chemical Analysis The acidity of the NCNS ranged from a pH 5.2 to 8.5 (Appendix C-1). The NCNS along transect 17 had a pH range of 5.2 to 6.1, with lower pH values locate d in the E horizon and higher pH associated with A and Bt horizons . The Bt horizon had 10% regolith, indicating underlying limestone. Soil acidity was conti ngent upon depth to limestone. Soil samples collected near the limestone had pH values higher than any other horizon. The NCAS had a wide pH range of 5.3 to 8.4 acr oss the site area (Figure 4-2). Cemetery samples had a discernible pattern of pH change based on sample depth. Soil pH increased along transect 14, from 7.5 at the Ap horizon (15 cm) to 8.4 at a depth of 115 cm. The pH range for soils sampled from suspected burials is highe r due to the mixing of soil horizons, including limerock and possible diagenesis of bone. 0 1 2 3 4 5 6 7 8 9 154585115145 Depth (cm)pH pH Anthropogenic soil pH Natual soil Figure 4-2. Depth distribution of Transect 14 pH values and Transect 17 pH values at the Newberry cemetery The OC content of NCNS, determined by Walkley-Black digestion, was < 5 g/kg-1 in all horizons (Table 4-1). The OC content decreased with depth until the Bt horizon. The NCNS Ap horizon contained 2.61 % OC. This decreased in the E horizons to approximately 0.35 % average. The OC content increased in the NC NS Bt to 1.25%. Anthropogenic soil OC content
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68 was similar with the natural soils. The Ap horiz on contained 2.8 % OC. A decrease in the E and Bt horizon occurred to approximately 0.48% and 0.42 % of OC respectively. The EC (EC) of the NCNS had low values (Table 4-1), ranging from 0.74 to .04 ds/m-1. The EC values decreased with depth in the NCNS E horizon, .04 to .06 ds/m-1. The Bt horizon’s highly conductive clay media had the highest values of .41 ds/m-1. The EC of the anthropogenic soils had a higher range of values. The values for the Ap horizon were .74 ds/m-1. The EC values for the E/Bt mixed horizons had a smaller decrease to .35 ds/m-1 on average. Table 4-1. Selected soil chemical analysis of the Newberry Cemetery natural and anthropogenic soils along transects 14 and 17. The EC (E C), extractable (Ext.), Organic carbon (OC), of the Newberry cemetery natural soils (NCNS), and Newberry cemetery anthropogenic soils (NCAS). Soil Depth (cm) Horizon EC ds m-1 Ext. P mg/kg Ext.Ca mg/kg Ext. Mg mg/kg OC % NCNS 0-15 Ap 0.28 12.72 188.72 28.06 2.61 Transect 17 45-60 85-100 116-131 E1 E21 E22 0.06 0.06 0.04 9.88 11.96 7.1 60.13 12.69 8.56 3.94 3.5 1.51 0.48 0.23 0.23 145-160 Bt 0.41 40.12 1209.4 21.22 1.25 NCAS 0-15 Ap 0.74 32.1 2693.1 53.2 2.8 Transect 14 45-60 83-98 115-130 E1 E2 Bt 0.4 0.28 0.38 189.8 36.6 80.5 2141.4 1167.7 978.6 17.2 13.1 27.7 0.48 0.48 0.42 Ext P contents in the NCNS (Table 4-1) ranged from 7.1 to 40.12 mg/kg-1 and increased in depth except between the Ap and E1 horizons. The Bt horizon had a four-fold increase of Ext P than from the overlying E1 and E2 horizon. Over all, the NCAS containe d greater values of extractable P than the NCNS (Table 4-1). Ext P content increased markedly in the E1 horizon and reduced to lower values in both the overl ying Ap and underlying E2 horizons. The greatest values of Ext P occurred where the mixing of soil horizons was most pronounced. Ext P content increased again in the Bt horizon, more than twice as much than the overlying E2 horizon.
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69 Concentrations of Ext Ca in the NCNS ranged from 8.5 to 1209.4 mg/kg with the lowest value occurring in the E2 horiz on and the highest amount in the underlying Bt horizon (Table 41). Proximity of the underlying limerock to the Bt horizon facilitates increased values of Ca in NCNS. The Ap horizon contained higher values of Ca than that of the underlying E1 horizon. Overall values of Ca in the anthropogenic soils were significantly higher in all recorded depths. Ca content for the NCAS samples were at the high end of the range of all soils in the site area. Unlike the NCNS, the overall Ca values de creased with depth; both the natural and anthropogenic soil samples had similar Ca values in the Bt horizon. Both the natural and anthropogenic soils co ntained comparable amounts of Mg throughout (Table 4-1), with the highest values occurring in the Ap horizon and lowest in the E1 and E2 horizons. The content of Mg in both soils increase d in the Bt horizon from overlying E1 and E2 horizons. Soils chemical analyses were conducted to de termine the differences between natural and anthropogenic soils. The NCNS have low values of P, and Mg; while increased Ca values are associated with depth to limestone. The NCAS ha ve increased values of P, Mg, and Ca from suspected buried remains. The means of these th ree elements from natural soils were compared to those of anthropogenic soils by calculating t -tests (Appendix E) Samples were collected from both natural a nd anthropogenic soils at the Newberry site area. The NCNS from the site were used as th e control for determination of potential natural soils. The NCNS from the site area were lower in extractable P concentrations than from the anthropogenic soils (t = -3.04, p = 0.01019) (Appendix E-1). The mean average for native soils was 20.5 mg/kg, while the NCAS had a mean aver age of 68.4 mg/kg. The overall Ca values of both the NCNS and NCAS were significantly different. Mixing of the anthropogenic soil
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70 horizons fundamentally altered the concentratio ns of Ca (t = -3.92, p = 0.00153) (Appendix E-1). Variability of Ca values throughout the soil horizons is reflected in the standard deviation that is more than double the NCNS. Concentrations of Mg did change between the NCNS and the NCAS (t = -2.53, p = 0.09874) (Appendix E-1), bu t not to the extent of the P and Ca concentrations. GPR-Soil Results for Newberry Cemetery The 500-MHz antenna Data acquisition of both NCNS and the NC AS soils with the GPR using the 500-MHz antenna created approximate profiles with dis tinctive reflections caused by contrasting soil properties. The NCNS has a planar stratification w ith occasional voids from the karst subsurface (Figure 4-3). Multiple, continuous contrasting layers in the NCNS soil represent the presence of an argillic (Bt) horizon. The dept h to argillic horizon in Figure 4-3 is approximately 0.9 to 1.1 m. Soils associated with Typic and Arenic Hapluda lfs are often not strati graphically homogenous. Bioturbation, such as animal burrows and tree roots, will frequently alter soil horizons. Processing steps for the horizontal and vert ical correlation of the NCNS and NCAS profiles include marker interpolation for distance (meters) and static correction time cuts for the removal of antenna ringing and velocity adaptation (Figure 4-3a). The lines superimposed on the GPR profiles in Figure 4-4 are manual velocity adaptation picks displayed to highlight the argillic horizon. After the soil su rface and horizontal alignment was determined, a background filter was applied to the transect profile. In order to accentuate and highlight a horizon interface, spectral whitening was applied to the GPR profiles when necessary (Figure 4-3b). A discernable difference in interpreting GPR prof iles is from the color scale; this is often the preference of the GPR operator. However by viewing multiple color scales, subtle images may become enhanced. In the an thropogenic soils, differences in color scale assisted in the
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71 overall interpretation. The profiles viewed in Rai nbow 2 color scale from Figure 4-3a is shown in Grey 1 color scale (Figure 4-3c). Energy decay was a final processing step chosen for select GPR profiles to augment data interpretation. The process extract s an energy decay curve of the line and applies the inverse of this function on the data. By activating this functi on a gain curve in the time direction (y-axis) is applied on the complete profile based on the me an amplitude decay curve. This step was primarily for highlighting the pr esence or absence of altered, he terogeneous anthropogenic soils (Figure 4-4). A pick was inserted into selected profiles to highlight subsurface amplitude value changes. Such changes included the interface of overlying horizons and the argillic horizon (Figure 4-3a, c). The GPR profiles of the NCAS produced dis tinct non-point source anomalies in both the E2 and Bt horizons. Due to the soil properties associated with the anomaly and stratigraphic break of the horizons, radar scatte r occurred in the GPR profile (F igure 44a). A low-amplitude reflection with little or no energy returned to the 500-MHz antenna. This is demonstrated with the absence of pronounced horizon tal banding within the anomal y. Application of specific processing procedures may either hi ghlight or mask the selected feature. The processing step of energy decay enables the operator to both highlight the grave and the backfill overburden (Figure 4-4b). With the application of spectral whitening, used for the NCNS profiles, the subtle image of overburden is less pronounced (Figure 4-4c). GPR profiles with Grey 1 color scale augment energy decay and spectral whitening processi ng features while reducing background noise (Figure 4-5).
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72 A B C Argillic Horizon Argillic Horizon Argillic Horizon Figure 4-3. Ground-penetrating ra dar profiles of the Arenic Ha pludalf using a 500-MHz antenna along transect 17. A) Background filter is applied and ante nna noise is removed. In this profile, both the ante nna noise and the horizontal banding are removed with no loss of interpretative data. Velocity adaptation pick is inserted to highlight the argillic horizon B) The depth to th e argillic horizon has been rectified and is more pronounced when spectral whitening is appl ied with a background filter. Argillic horizon is highlighted with manual pick. C) Background noise and argillic horizon is more prominent with filter and Gray color scale applied.
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73 A B C G r ave G ra ve G r ave Figure 4-4. Ground-penetrating rada r profiles of anthropogenic altere d Arenic Hapludalf using a 500-MHz antenna along transect 14. A) Background filter is applied and antenna noise is removed. Note the very low amp litude reflection at 9.5 to 12 m transect range. B) Energy decay step is added to the post-processing from profile A. Overburden is more pronounced overlying th e feature. C). The use of spectral whitening is added to the post-pr ocessing step from profile A. The 900-MHz antenna Data acquisition of both NCNS and the NCAS with the GPR using the 900-MHz antenna created shorter wavelengths, thereby increasing th e resolution of radar images. Reflections from subsurface discontinuities also increased from tree roots, stumps and rocks. Many of these discontinuities or ‘noise’ were not detected in the 500-MHz antenna. Any subtle changes in GPR profiles with distinctive reflectio ns caused by contrasting soil pr operties were more apparent in the 900-MHz antenna. The increased resolution from the 900-MHz antenna was offset by the
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74 lessened depth of penetration. Ra dar signals were affected by both the type of anomaly and depth. Coherent signals were attenuated with specific anthropogenic features. The 900-MHz antenna was also affected by the depth to the argillic horizon. The depth of the argillic horizon influenced the higher fre quency antenna. On many transects the argillic horizon was barely visible, or not detected using the 900-MHz antenna (Figure 4-6), but was strongly evident with the 500MHz antenna (Figure 4-3). A B C G r ave G r ave G r ave Figure 4-5. Ground-penetrating rada r profile of anthropogenic altere d Arenic Hapludalf using the 500-MHz antenna along transect 14. A) Filtering of horizontal banding and background clutter is enhanced in Gray 1 color scale. B) Overburden is more prominent when the energy decay processing step is applied in the Gray 1 color scale. C) Note the very low amplitude reflection at the 9.5 to 12 m transect range is more discernable when the Gray 1 color scale is used.
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75 A Argillic Horizon C Argillic Horizon B Argillic Horizon Figure 4-6. Ground-penetrating ra dar profile of natural Arenic Hapludalf using the 900-MHz antenna along transect 17. Velocity adaptation pick is inserted to highlight the argillic horizon. A) Filtered profile reduces horizont al banding. The argillic horizon is less discernable than from the 500MHz antenna. B) Spectral whitening step is added to filtered profile, highlighting the Argillic horizon. C) Filtering with spectral whitening process combined with gray scale re duces horizontal banding significantly. Anomalies detected by the 900-MHz antenna from the NCAS along transect 14 (Figure 4-7) are discernable with post-processing procedures. Filt ered profiles with energy decay processing applied are more discernable than with just th e filter alone; both with Gray 1 and Rainbow 1 color scales (Figure 4-6 b, c). Even filtered, numerous micro-reflections are evident throughout the GPR profile. This background ‘noise’ may dr aw focus from subtle sub-surface features.
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76 B Overburden G ra ve C Overburden G ra ve A Overburden G ra ve Figure 4-7. Ground-penetrating ra dar profile of anthropogenic Arenic Hapludalf using a 900MHz antenna along transect 14. A) B ackground filter reduces subsurface discontinuities throughout the profile. Lo w amplitude reflection from a feature is discernable between the 9.5 to 12 m range along transect from 0.5 to 1.6 m in depth. B) Energy decay processing step is adde d to background filtering, highlighting the scattering effect of low amplitude reflect ions. Overburden is discernable overlying grave. C) Energy decay with background filte ring using Gray 1 color scale further reduces subsurface discontinuities and isolat es the overburden and underlying grave.
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77 Oakland Cemetery The Oakland cemetery is located south of Lake Apopka in western Orange County, Florida. This site was select ed for the native soils (Entisol s) and the anth ropogenic context (cemetery). The soils from the site area are mapped as both Entisols and U ltisols (Doolittle and Schellentrager 1989). These soils ar e classified as a Candler-Apopka complex; the mapped areas consist of generally 66% Candler soil (Entisols) and similar so ils, with about 31% Apopka soil (Ultisols) and similar soils. This soil complex is too mixed to be mapped separately (Doolittle and Schellentrager 1989). The marked graves are from the late nineteen th to early twentieth century; several unmarked graves are located wi thin proximity of the existing cemetery. This site, similar to the Newberry cemetery, addresse d several objectives of the study: the application of GPR to verify the existence of a clandestin e grave while meeting the criteria of a specific Florida soil Order. Soil Physical Analysis Particle-size distributi on of Oakland cemetery natural soil s (OCNS) was dominated in all samples by the medium grain to very fine grai n sand (Appendix A). The soil data were compared to the information from the Orange County Soil Survey (Doolittle and Schellentrager 1989). The site area has been mapped as Candler and Apopka-Candler complex. Candler soils are a hyperthermic, uncoated Lamellic Quaritzipsamment s. The Candler soils series consists of excessively drained soils, an ochric epipedon, ap proximately 90% medium to very fine sand in the A and C horizons, and less than 3% silt and 2.5% clay. The ochric epipedon had an average silt content of 1.8%. The Candler series at th e Oakland cemetery has clear, wavy lamellae at approximately 1.0 to 1.2 m in depth. The amount of clay content increased from < 1.2% in the Ap horizon, to 2.5% in the C3 horizons in associ ation with the lamellae. At the Oakland site area, the Candler soil series is associated with the Apopka series. A popka soils are loamy,
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78 siliceous, hyperthermic Grossare nic Paleudults. These two soils ar e morphologically very similar in the upper 1.5 m. The Apopka series has an ar gillic horizon within 2.0 m of the surface. Physical soil analyses from the site determined the absence of a Bt horizon, with the default classification being a Candler soil series. Further discussion of taxonomic and morphological classification of the Oakland cemetery soil will be addressed in Chapter 5 and Appendix A. Oakland cemetery anthropogenic soils (OCAS) were dominated in all samples by medium to very fine sand. Associated with OCNS, the mi xed horizons of the altered soils did not change noticeably in particle-size distribution. Particle -size distributions of the OCAS horizons were dominated in all samples by the sand fraction, w ith a range of 95.1 to 97.9%, with low values of silt (< 2.7%) and clay (< 2.6%). Potential surveyed graves displayed no significant change in physical properties from the OCAS. Soil Chemical Analysis The acidity of the Oakland cemetery soils ra nged from a pH 5.9 to 7.1 (Figure 4-8). The OCNS had a pH range of 4.9 to 5.3, with lower pH values located in the Ap horizon and higher pH associated with C1 horizons. Soil acidity for the OCNS was not significantly variable, with a pH range of 4.9to 5.3 of all horizons. Orange grov es are located within 75 meters upslope on the east and north sides of the site area (Figure 23). This tertiary influence on pH and other chemical analyses will be discussed in the next chapter. The OCAS had a pH range of 6.0 to 7.2 acro ss the site area. Cemetery samples had a pattern of pH change based on sample depth. Soil pH increased varied from 6.0 in the lower C horizon (85cm) to 7.2 (50 cm) at two grave sample s (Figure 4-8). The pH range for soils sampled from suspected burials is higher due to the mixi ng of soil horizons, includ ing possible diagenesis of bone.
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79 0 1 2 3 4 5 6 7 8 155085120 Depth (cm)pH pH Antropogenic soil pH natural soil Figure 4-8. Depth distribution of pH values for Transect 2 at the Oakland cemetery. The OC content of OCNS, determined by Walkley-Black digestion, was < 2 % in all horizons along transect 2 (Table 4-2). The OC from the OCNS samples decreased with depth until the C3 horizon. The Ap horizon contained of 1.32 % OC. This decreased in the C1 horizon to 0.1 %, C2 horizon to 0.16 % and to a 0.29 % in the C3 horizon. The OCAS OC content was slightly higher than native soils in the C1 horizon and C2, with lower values in the C3 horizon. The Ap horizon in the OCAS had lower valu es of OC, with 0.55 %. A decrease in the anthropogenic C1 horizons occu rred to approximately 0.42 % of OC, with 0.48 % in the C2 horizon. The OCAS C3 horizon had lower values than the OCNS C1, C2 horizons with approximately 0.03 % of OC. The EC (EC) of the OCNS had low values fr om transect 2 (Table 4-2), ranging from 0.34 to 0.06 ds/m-1. The EC values in the Ap horizons of the OCNS were approximately 0.34ds/m-1, and decreased with depth in the C1 horizons, C2 horizons and C3 horizons from .08 to .06 ds/m1. The EC of the OCAS had a lower range of va lues. The EC mean average for the Ap horizons was .14 ds/m-1. The EC values decreased to .14 ds/m-1 in the C1 horizons, .06 ds/m-1 in the C2 horizons and increased slightly to.26 ds/m-1 in the C3 horizons.
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80 Ext P content in the OCNS (Table 4-2) from transect 2 ranged from 12.8 to 4.29 mg/kg-1 and was variable in depth between the C1, C2 and C3 horizons. The Ap horizon had a value of 12.8 mg/kg-1, with the C3 horizons having the next hi ghest overall Ext P concentration at 10.41 mg/kg-1. The OCAS contained greater values of extr actable P than the OCNS (Table 4-2). Ext P content of anthropogenic soils increase d markedly in the Ap, with 58.84 mg/kg-1, with 70.48 mg/kg-1 and in the C1 horizon. Lower values of Ext P occurred in C2 with 6.87 mg/kg-1, and 4.69 mg/kg-1 in the C3 horizon. The greatest values of Ext P occurred at a depth of 0-50 cm, where the mixing of soil horizons was most pronounced. Concentrations of Ca in OCNS from transect 2 ranged from 26.14 to 65.45 mg/kg-1 with the lowest value occurring in the lower C2 horizon and the highest am ount in the Ap (Table 4-2). Ext Ca decreased with depth until the C3 horiz on (135 to 150 cm) with a value of 46.38 mg/kg-1. Overall values of Ext Ca in the OCAS were si gnificantly higher in the upper 0.5 m. Ext Ca for the OCAS ranged from 148.29 mg/kg-1 in the C1 horizon to 10.92 mg/kg-1 in the C3 horizon. The OCNS contained lower overall values of Mg than the anthropogenic soils. (Table 4-2). Ext Mg in OCNS ranged from 25.21 to 9.49 mg/kg-1, with higher values in the upper 0.5 m and the lowest values occurring between 0.85 to 1.00 m. Ext Mg in the anthro pogenic soils decreased with values of 14.91 mg/kg-1 in the C2 horizon and to 6.01 mg/kg-1 in the C3 horizon. Soils chemical analyses were conducted to de termine the differences between natural and anthropogenic soils. The OGSN have low values of P, Ca, and Mg. Anthropogenic soils have increased values of P, Mg, and Ca from susp ect buried remains. These means of these three elements from NCNS were compared to those of the NCAS by calculating t -tests
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81 Table 4-2. Selected values of chemical prop erties of the Oakland Cemetery natural and anthropogenic soils along transect 2. The EC (EC), extractable (Ext.), Organic carbon (OC), Oakland cemetery natural soils (OCN S), Oakland cemetery anthropogenic soils (OCAS). Soil Depth (cm) Horizon EC ds m-1 Ext. P mg/kg Ext.Ca mg/kg Ext. Mg mg/kg Org. C % OCNS 0-15 Ap 0.34 12.8 65.45 25.21 1.32 Transect 35-50 C1 .08 8.02 47.49 12.46 0.1 2 85-100 C2 .06 4.29 26.14 9.49 0.16 135-150 C3 .06 10.41 46.38 13.05 0.29 OCAS 0-15 Ap 0.14 58.84 127 25.21 0.55 Transect 35-50 C1 0.14 70.48 148.29 20.22 0.42 2 85-100 C2 0.06 6.87 29.91 14.91 0.48 135-150 C3 0.26 4.69 10.92 6.01 0.03 Samples were collected from both natural and anthropogenic soils at the Oakland cemetery area. The OCNS from the site were used as the control for dete rmination of suspect anthropogenic soils. The OCNS from the site area were lower in extractabl e P concentrations and variability than from the anthropogenic soils (t = -2.62, p = 0.1853) (Appendix E-2). The mean for OCNS was 8.26 mg/kg, while the impacted so ils had a mean of 34.4 mg/kg. The overall Ca values of both the OCNS and OCAS were marked ly different. Mixing of the anthropogenic soil horizons altered the concentratio ns of Ca (t = -1.89, p = 0.2329) in the upper 0.5 m. Variability of Ca values is limited to the upper soil horizons; this is reflected in the sta ndard deviation that is more than double that of the natural soils. Concentrations of Mg did change significantly between the OCNS and OCAS (t = -1.69, p = 0.1625) (Appendix E-2). GPR-Soil Results for Oakland Cemetery The 500-MHz antenna The OCNS has a homogenous matrix with little variation in physical properties (Figure 49). The Candler series at this site has clear, wavy lamellae at approximately 1.0 to 1.2 m in depth
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82 that is evident in the GPR profile with the 500-MHz antenna. Bioturbation, such as animal burrows and tree roots, will be evident at depths less than 2 meters in the OCNS. Anomalies at depths greater than two meters often entail targ ets larger than most bi oturbation. Both OCNS and OCAS GPR profiles are al ong the same transect. Identical processing steps for the horizontal and vertical correlation of the GPR profiles at the Newberry cemetery were used for the Oaklan d cemetery. This included marker interpolation for distance (meters) and static correction time cuts for the removal of antenna ringing (Figure 49a). After the soil surf ace and horizontal alignment was determined, a background filter was applied to the transect profile. In order to a ccentuate and highlight a horizon interface, spectral whitening was applied to profiles when necessary (Figure 4-9c). This step was primarily for highlighting the presence or absence of altered, heterogeneous anthropogenic soils, but was also used for the homogenous nature of the soils at the site area. Spectral whitening decreased the hyperbolic tail associated with the anomalies in transect 2 The GPR profiles of anthropogenic soils at th e Oakland cemetery produced distinct point source anomalies in both the C1 and C2 horizons. Du e to the soil properties associated with the elongated and suspect graves, noticeable reflec tion hyperbolas occurred in the GPR profile (Figure 4-9a). Medium to high-am plitude reflections with signif icant energy returned to the 500MHz antenna, enabling a distinct signal return separate from the surrounding matrix. This is demonstrated with the presence of pronoun ced horizontal banding within the anomaly. Background filters allow for a clearer image of an already distinct anomaly. With the application of spectral whitening, the image becomes more pronounced (Figure 4-9c). A pick was inserted into selected profiles to highlight subsurface amplitude value changes. Such changes included the start of the lamellae from 1.0 to 1.5 m in depth.
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83 . C Potential g raves L a m e ll ae B A L a m e ll ae L a m e ll ae Potential g raves Potential g raves B C Figure 4-9. Ground-penetrating radar profile using the 500-MH z antenna with two suspect graves from a Lamellic Quartzipsamment. A) Background filter is applied and antenna noise is removed. B) Spectral whitening processing step is added to background filtering, note the increased contra st of suspect graves and the reduction of hyperbolic tail. C) Backgr ound filter is applied, antenna noise is removed and Gray 1 color scale is used. Contrast is enha nced and hyperbolic tail is increased. The 900-MHz antenna Data acquisition of OCNS and OCAS with the GPR using the 900-MHz antenna created shorter wavelengths, thereby increas ing resolution of radar images. Any distinctive reflections in the GPR profiles that were caused by contrasting soil properties became more apparent with the 900-MHz antenna. Many discontinuiti es in the transect profile we re not detected with the 500MHz antenna (Figure 4-9); while the increased resolution from the 900-MH z antenna was offset Sus p ect g raves Suspectgraves Sus p ect g raves
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84 by shorter hyperbolic tails in pr ocessed profiles. The use of hi gher frequency antennas may limit the operator to locating and inte rpreting anomalies at varied de pths along a transect profile. Anomalies detected by the 900-MHz antenna fr om the anthropogenic so ils along transect 2 maybe more discernable with post-processing pr ocedures, but not necessary. Filtered profiles with spectral whitening processing applied are no mo re discernable than with just the filter alone (Figure 4-10 b); both with Gray 1 and Rainbow 2 co lor scales (Figure 4-10 a, c). Filtered, with spectral whitening allows for less numerous micro -reflections throughout the profile. As with the 500-MHz antenna profiles, velocity adaptation pick s were inserted to the processed profiles to highlight the lamellae from 1.0 to 1.5 m in depth (Figure 4-10). Prehistoric Archeological Site The prehistoric archaeological site is located in eastern Lake County, Florida on the southwest shore of Lake Apopka. This site was se lected for the study based on the both the soils, (Inceptisol) and on the anthropogenic context (prehistoric). There are two soils are mapped with the site area; a well-drained Orlando series (In ceptisol) and a very well-drained Entisols classified as the Lake soil se ries (Furman et al. 1975). The Orlando series is the predominate soil for this study. Two prehistoric archaeological components have been pr eviously excavated in this study area. Associated featur es within the prehis toric midden date as early as 1600 B.C. (Austin 2006). This site addresse d several objectives of the st udy: the application of GPR to verify the extent of prehistori c anthropogenic influences while m eeting the criteria of a specific Florida soil Order.
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85 Potential g raves A L a m e ll ae L a m e ll ae Potential g raves B L a m e ll ae Potential g raves C Figure 4-10. Ground-penetrating ra dar profile using the 900-MHz an tenna of two suspect graves in a Lamellic Quartzipsamment. A) Background filter is applied and antenna noise is removed. Horizontal banding is still preval ent. B) Spectral whitening processing step is added to background filteri ng, note the increased contrast of anomalies and the reduction of hyperbolic tail. C) Background filte r is applied, antenna noise is removed and Gray 1 color scale is used . Contrast is enhanced and hyperbolic tail is increased. Soil Physical Analysis All horizon designations for this site were described mor phologically and subdivided for sampling purposes. The primary numerical suffixe s are denote subdivisions within a master horizon; e.g., A1, A2, C1, C2, and C3. Sec ondary numerical suffixe s denote the sampling subdivision within the horizon modifier. Particle-size distri butions of the prehistoric archaeological natural soils (PANS) at this site we re dominated in all samples by medium to very fine sand (Appendix A). The soil data was compared to the information in the Lake County Soil Sus p ect g raves Suspectgraves Sus p ect g raves
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86 Survey (Furman et al. 1975). The soil survey ar ea has been mapped as a well-drained sandy, siliceous, hyperthermic Psammentic Dystrudept s, with an umbric epipedon, approximately 93.5% coarse to fine sand throughout the A and C horizons, and less than 1% silt and 5.7% clay. The umbric epipedon had an average silt content of 0.8% with a decrease to 0.3% in the C horizon. The amount of clay content increased sli ghtly from < 5.9% in the A horizon to 6.4% in the C horizon. Physical properties of the prehistoric arch aeological anthropogenic soils (PAAS) at the prehistoric site were very similar to the P ANS. Both the PANS and PAAS had no morphological differences in any of the horizons, except an A/C horizon at 0.9 to 1. 05 m. The PAAS were dominated with approximately 94.2% coarse to fine grain sands, le ss than 1% silt and 6.6% clay in the A and C horizons. The silt content vari ed less than 0.7% among the A and C horizons. Less than a 1% difference in clay content occurred among the A and C horizons in all anthropogenic samples. Chemical Analysis The acidity of the all prehistoric site soils ranged from a pH 4.3 to 6.9 (Figure 4-11). The PANS had a pH range of 4.3 to 5.5, with lower pH values located in the A horizon and higher pH associated at a depth of 0.35 to 0.75 m. Soil aci dity for the PANS was variable, with a pH range of 4.4 to 4.6 below 0.75 m. Orange groves are loca ted within 5 to 10 meters upslope on the west side of the site area (Figure 2-6). This tertiary influence on pH and other chemical analyses will be discussed in the next chapter. The PAAS had a pH range of 6.1 to 6.9 along selected GPR transects (Figure 4-11). Samples had a pattern of pH change, increasing with sample depth. Soil pH increased from 6.1 at the surface (0-15 cm) to 6.9 at the base of the C horizon (1.8 to 1.95 m). The OC content of the PANS, determined by Walkley-Black digestion, was < 2.5 % in all horizons (Table 4-3). In
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87 general OC amounts decreased with dept h. The A1 horizon contained 2.4 g/kg-1 OC. This decreased in the A2 horizon to approximately 1. 32 %, with 0.34 % in th e C horizons. The PAAS OC content was slightly higher than native soil s in the C horizon. The A horizon in the PAAS had slightly lower values of OC (1.96%) than th e PANS (Table 4-3). A decrease in the PAAS A2 horizons occurred to approximately 1.55 % of OC, with 0.44 % in the C horizons. The PAAS C horizon had slightly higher valu es than the PANS C horizons. Range of pH to depth at Prehistoric Site0 1 2 3 4 5 6 7 8 154575105135165195 Depth (cm)pH pH (natural soils) pH (anthropogenic soils) Figure 4-11. Depth distribution of pH values for transects at the prehistoric archeological site. The EC (EC) of the PANS had values (Table 4-3), ranging from 1.36 to 0.04 ds/m-1. The EC values in the A1 horizons were approxima tely 1.36 and 0.62 ds/m-1, and decreased with depth in the A2 horizons. The values in the C hor izons were from 0.04 to .48 ds/m-1. EC of the anthropogenic soils had slightly lower range of va lues. The EC values for the A1 horizon was 0.4 to 0.28 ds/m-1. The EC values decreased to 0.26 to 0.22 ds/m-1 in the A2 horizons. The values in the C horizons ranged from 0.18 to 0.14 ds/m-1 . Overall values decreased with depth in both the PANS and PAAS horizons. Ex t P content in the PANS (Table 4-3) ranged from 343.2 to 70.9 mg/kg-1 and decreased in depth between th e A12 and C13 horizons. The A12 horizon had highest value of 353.5 mg/kg-1, with the C13 horizons having th e lowest overall extractable
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88 phosphorus concentration at 70.9 mg/kg-1. Anthr opogenic soils contained much greater values of Ext P than the PANS. Ext P content of anthro pogenic soils increased markedly in the A12 and A21 horizons with lower values in C horizons. Table 4-3. Selected values of chemical prop erties from natural and anthropogenic soils at prehistoric archaeological site. The EC (EC) , extractable (Ext.), Organic carbon (OC), prehistoric archaeological natural soils (PANS), and prehistoric archaeological anthropogenic soils (PAAS). Soil horizons subdivided for sampling depths. Soil Depth Horizon EC Ext. P Ext. Ca Ext. Mg Org. C PANS cm ds m-1 mg/kg mg/kg mg/kg % 0-15 A11 1.36 278 310.4 28.4 2.4 30-45 A12 0.62 343.2 353.3 36 1.62 60-75 A21 0.32 278 231.2 21.6 1.49 90-105 A21 0.38 203.6 112.6 13.3 1.1 120-135 C11 0.04 167.2 80.7 13.2 0.78 150-165 C12 0.6 78.4 39.9 10 0.13 180-195 C13 0.48 70.9 38.6 9.9 0.13 PAAS 0-15 A11 0.4 1400.2 2085 81.4 2.07 30-45 A12 0.28 1617 2278.1 80.9 2.27 60-75 A21 0.26 1633.5 2347.4 64.7 2.07 90-105 A22 0.22 759.2 801.4 37.4 0.65 120-135 C11 0.18 710 648.6 34.3 0.58 150-165 C12 0.18 449.2 379.5 28.8 0.39 180-195 C13 0.14 388.4 303.4 24.3 0.19 The greatest concentrations of Ext P occurred at a depth of 0.30 to 0.75 m with values of 1617 and 1633.5 mg/kg-1. Concentrations of Ext P in the anthropogenic C horizon were lower than the overlying the soil horizons. Concentrations of Ca in the PANS ranged from 353.3 to 39.9 mg/kg-1 with the lowest value occurring in the lower C horizon and the highest amount in the A12 (Table 4-3). Ext Ca decreased with depth. Overall values of Ext Ca in the PAAS were significantly higher in all horizons. Ext Ca contents for the PAAS ranged from 2347.4 mg/kg-1 in the A21 horizon to
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89 303.48 mg/kg-1in the C13 horizon. Similar to the PANS the overall Ca values decreased with depth throughout all horizons. The PANS contained lower overa ll values of Mg than the PAAS (Table 4-3). Ext Mg in the PANS ranged from 36.04 to 9.9 mg/kg-1, with higher values in the A1 and the lowest values occurring in the C horizon. The concentration of Mg in the PAAS decreased with depth with values from 81.4 mg/kg-1 in the A1 horizons to 24.3 mg/kg-1 in the lower C13 horizons. Native Quartzipsammentic Haplumbrepts from the site were used as the control for determination of potential anthropogenic soils. Elevat ed overall concentrations of extractables P, Ca, and Mg were present throughout the site area; the potential reason for such high values will be covered in the following chapter. The PANS from the site area were much lower in Ext P concentrations and variability than from the PA AS (t = -4.71, p = 0.00597) (Appendix E-3). The mean for the PANS was 224.73 mg/kg, while the im pacted soils had a mean of 994 mg/kg. These values are quite high in both the PANS and the PAAS. The overall Ca values of both the PANS and the PAAS were noticeably different. Concentrati ons of Ext Ca in all horizons (t = -1.72, p = 0.01706) (Appendix E-3) were distinct. Variabilit y of Ca values is not limited to any soil horizons; this is reflected in the standard deviation that is more than five fold that of the PANS. Concentrations of Mg did change between the PAAS and the PANS (t = -0.541, p = 0.109), but not with the significance of both the Ext P and Mg. GPR-Soil Results for the Prehis toric Archaeological Site The 500-MHz antenna The PANS has little variation in physical properties. The Orla ndo series at this site has a clear, morphological horizon separation; this depth is evident in the 500-MHz antenna GPR profile (Figure 4-12). Even in the PANS, punctu ated human disturban ces are clear throughout this site area. The GPR profiles of the PANS are along different transects than the GPR profiles
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90 of the PAAS, but run through ac tive orange groves. The GPR tr ansects of the PANS were conducted upslope and away from the known archaeo logical site areas, which were situated along the lake shore. The differences between GPR profiles of the PANS and PAAS are in context to archaeological significan ce for this study. Both soils have been altered through human activities; the difference is temporal instead of spatial and will be covered in the discussion chapter. Identical processing steps for the horizontal and vertical correlat ion of the GPR profiles of the previous sites were used for the prehistoric site . This includes marker interpolation for distance (meters) and static correction time cuts for the removal of antenna ringing. After the soil surface and horizontal alignment is determined, a backgr ound filter was applied to each transect profile. In order to accentuate and highlight a horizon in terface, spectral whitening was applied to GPR profiles when necessary. This step was primarily for highlighting the presence or absence of altered, heterogeneous anthropoge nic soils, but was also used fo r the homogenous nature of the epipedon at this site. The GPR profiles of both the PANS and PAAS produced distinct point source anomalies and planar subsurface interfaces in both the A2 and C horizons. Due to the soil properties associated with the elongated and perpendicu lar anomalies of subsurface irrigation lines, noticeable reflection hyperbolas occurred in the GPR profile (F igure 4-13a). Medium to highamplitude reflections with significant energy returned to the 500-MHz antenna, enabling a distinct signal return separa te from the surrounding matrix. With planar stratification in the soil horizons, removal of horizontal banding greatly enhances any anomalies. Background filters also a llow for a clearer image of an already distinct
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91 anomaly. With the application of spectral whitening, images become more pronounced and nonpoint source anomalies are highlighted (Figure 4-13c). A B C H o riz o n A H o riz o n A H o riz o n A H o riz o n C H o riz o n C H o riz o n C Figure 4-12. Ground-penetrating ra dar profiles of a natural Psammentic Dsystrudepts using the 500-MHz antenna. A) Background filter is applied and an tenna noise is removed. Velocity adaptation pick is inserted to highlight the C horizon. B) Spectral whitening processing step is added to background filte ring, note the increased contrast between the A and C horizon. C) Background filter is applied, antenna noise is removed and Gray 1 color scale is used. Contrast is enhanced between the A and C horizon with velocity adaptation pick is inserted. AHorizon A Horizon AHorizon CHorizon CHorizon CHorizon
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92 Irri gat i o n p i pe F eatu r e Irri gat i o n p i pe F eatu r e A B C Irri gat i o n F eatu r e Irri gat i o n p i pe Figure 4-13. Ground-penetrating ra dar profiles of an anthropoge nic Psammentic Dsystrudepts using the 500-MHz antenna. A) Background f ilter is applied and antenna noise is removed. B) Spectral whitening processing st ep is added to background filtering, note the increased contrast between the A and C horizon. C) Background filter is applied, antenna noise is removed and Gray 1 color sc ale is used. Hyperbol ic tail and contrast between the A and C horizon is enhanced. F eature banding is highlighted with change in color scale. Varying color scales accentuate subtle ch anges within the GPR profile, allowing the operator multiple views for data interpretation. A difference in interpreting GPR profiles when subsurface variation is nominal, offers an adva ntage with specific sites. In the anthropogenic soils at this site differences in color scale a ssisted in the overall inte rpretation of subsurface features.
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93 The 900-MHz antenna The GPR profile of the PANS using the 900-MHz antenna exhibited no distinct reflections from all horizons. Data acquisition of both P ANS and the PAAS with the GPR using the 900MHz antenna created shorter wave lengths, thereby increasing reso lution of radar images (Figure 4-14). C H o riz o n A B C AH o riz o n AH o riz o n AH o riz o n C H o riz o n C H o riz o n Figure 4-14. Ground-penetrating ra dar profiles of a PANS Psa mmentic Dsystrudepts using the 900-MHz antenna. A) Background filter is applied and an tenna noise is partially removed. Numerous micro-reflections occur. Velocity adaptation pick is inserted. B) Spectral whitening processing step is added to background filtering. Background noise is further removed. C) Background filte r is applied, antenna noise is removed, and spectral whitening and Gray 1 color scale is used. Further contrast is somewhat apparent. Contrast is enhanced between th e A and C horizon with velocity adaptation pick is inserted.
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94 A Irri g ati on p i pe Feature B Irri gat i on p i pe Feature C Irri g ati on p i pe Feature Figure 4-15. Ground-penetrating ra dar profiles of an anthropogenic Psammentic Dsystrudepts using the 900-MHz antenna. A) Background f ilter is applied and antenna noise is removed. B) Spectral whitening processing st ep is added to background filtering, note the increased contrast between the A and C horizon. C) Background filter is applied, antenna noise is removed and Gray 1 color sc ale is used. Hyperbolic tail is reduced in higher frequency antenna. Contrast between the A and C horizon is enhanced. Feature banding is highlighted with change to Gray 1 color scale. The GPR profiles of the PANS provided only di ffuse stratigraphic resolution. Any subtle changes in GPR profiles with distinctive reflec tions caused by contras ting soil properties were apparent in the anthropogenic soils using the 900-MHz antenna (Figure 4-15). The increased resolution from the 900-MHz antenna was offset by s horter hyperbolic tails of the irrigation pipe Feature
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95 in processed GPR profiles of the PAAS. A pick wa s inserted into selected profiles to highlight subsurface amplitude value changes. Such cha nges included the A and C horizon interface. A suspected feature is located near the irrigation pipe; this might be associated with the excavation of the pipe (Figure 4-15). This suspected featur e is less prominent in the GPR profile using the 900-MHz antenna, then with the 500-MHz antenna. Historic Archeological Site The British Period occupation site is located in northeastern St. Johns County, Florida, west Tolomato River. This site was select ed for the study based on the both the soils, (Spodosols) and on the anthropogenic context (histori c). The two soil Orders mapped in the site area are weakly to moderately developed Spodosols with associated Entisols; and are classified as either Myakka/Immokalee (Spodosols) with Paola (Entisols) soils (Readle 1983). The Immokalee series is the predominate soil for this study. The archaeological c ontext of this site is primarily the British Period (1763-1784 A.D.), with Spanish and prehistoric components associated with the site area. This site addres sed several objectives of the study: the application of GPR to verify the extent of historic anthr opogenic influences while meeting the criteria of a specific Florida soil order. Soil Physical Analysis The particle-size distribution of the historic archaeological natural soils (HANS) at this site was dominated in all samples by the medium to very fine sand fraction throughout (Appendix A). The soil data was compared to the inform ation from the St. Johns County Soil Survey (Readle 1983). The sampled site area has been mapped as the Immokalee, sandy, siliceous, hyperthermic Arenic Alaquods series with approx imately 95% medium to fine sand in the Ap and E1, E2, and E3 horizons, with less than 2.5% silt and 3% clay. The underlying Bh horizon is from 0.74-0.93 m, with 2.4% silt and 2.8% clay. The ochric epipedon had an average silt content
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96 of 1.7% with a linear decrease to 0.9% in the E3 horizon. The amount of clay and silt content increased slightly in the Bh horizon. The historic site area has another associated soil, a hyperthermic, uncoated Spodic Quartzipsamment. This soil is the St. Johns series and has very similar morphological characteristics to the Immokalee. Due to the dept h of water table, the St. Johns series may be more closely relevant to the site. However, fr om a morphological interp retation, the Immokalee series will be referred in this chapter as the dominant soil series. The human impacted soils at the historic arch aeological site were dissimilar to the native Arenic Alaquods. The historic archaeologica l anthropogenic soils (HAAS) had soil color differences, lower values and chroma (Appendix A4) in the horizons E1 and E2 horizons from 0.2 to 0.45 m. The HAAS were dominated with a pproximately 93.7% medium to fine sands, with values of less than 6.0% silt and 3.5% clay in the A, E1, and E2 horizons. The Ap horizon had a mean average of 3.4% silt and 0.9% clay. The E1 horizon, from 0.20 to 0.25 m, had a mean of 1.9% silt and 1.6% clay; while the underlying E2 horizon had 1.5% silt and 1.7% clay at 0.40 to 0.45 m below surface. Overall silt and clay values are elevated in the E1 and E2 horizons when compared to the HANS. Soil Chemical Analysis The acidity of the all prehistoric site soils ranged from a pH 4.7 to 7.8 (Appendix C-4). Representative samples were taken from a HANS transect and a HAAS transect (Figure 4-16). The HANS had a pH range of 4.7 to 5.4, with lo wer pH values located in the E horizons and the higher pH values associated with the Ap horizon . The HAAS had a higher pH range of 6.1 to 7.8 across the site area (Appendix C-4). Samples had a pattern of pH change, increasing with sample depth. Selected soil pH from transect 1 increased with 6.1 at the surface (0-5 cm) to 7.5 and 7.6 in the E horizons (20 to 45 cm) (Figure 4-16).
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97 Range of pH to depth at Historic Site0 1 2 3 4 5 6 7 8 525456585 Depth (cm)pH pH (natural soils) pH (anthropogenic soils) Figure 4-16. Depth distribution of selected pH values for transects at historic archaeological site. Historic site data did not exceed 0.50 m. The OC content of the HANS, determined by Walkley-Black digestion, was < 6 % in all horizons (Table 4-4). The OC content decreased with depth in the E1 and E2 horizons, and increased in the underlying E3 and Bh horizons. The Ap horizon contained 5.07 % OC. This decreased to approximately 0.32 %, with 0.26 % in the E1 and E2 horizons. The Bh horizons increased to 1.8 %. Both the PANS and anthropo genic soils did not differ significantly in the Ap horizon. Anthropogenic soil OC content was high er than native soils in the E1 horizon. Decreases in the anthropogenic E2 horizon occurred to approximately 0.64 % of OC, yet was double that of the PANS E2 horizon with 0.25%. The HANS had values of EC (Table 4-4), ranging from .42 to .02 ds/m-1. The EC values in the Ap horizons had the highest P ANS values with approximately .42 ds/m-1, and decreased with depth in the E2 horizons, and E3 horizons from 0.04 to 0.02 ds/m-1. A slight change occurred in the Bh horizon to a value of 0.06 ds/m-1. The EC of the anthropogenic soils had slightly higher range of values. The EC mean average for the Ap
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98 Table 4-4. Selected mean values of chemical properties from PANS and anthropogenic soils at prehistoric archaeological si te. Electrical conductivity (EC), extractable (Ext.), Organic carbon (OC), historic archaeol ogical natural soils (HANS), historic archaeological anthropog enic soils (HAAS). Soil Depth (cm) Horizon EC ds m-1 Ext. P mg/kg Ext. Ca mg/kg Ext. Mg mg/kg Org. C % HANS 0-4 Ap 0.42 14.3 7.4 47.6 5.07 4-16 E1 0.02 1.1 5.1 3.4 0.32 16-46 46-74 74-93 E2 E3 Bh 0.04 0.02 0.06 1.2 1 27.8 3.2 3.5 23.4 2.1 1.4 8.7 0.26 0.26 1.8 HAAS 0-5 A 0.80 64.3 759.8 130.1 4.49 20-25 E1 0.42 383.2 1390.8 50.9 1.28 40-45 E2 0.14 130.8 339.7 9.8 0.64 horizons was 0.80 ds/m-1. The EC mean values decreased to 0.42 ds/m-1 in the E1 horizons, and 0.14 ds/m-1 in the E2 horizons. Overall values decr eased with depth in both the PANS and anthropogenic soil horizons in the upper 0.5 m. The HANS had Ext P contents that ranged from 1.1 to 27.8 mg/kg-1 and decreased in depth from the Ap to E3 horizons. In the Bh horizon the concentration of Ext P increased. The Ap horizon had a value of 14.3 mg/kg-1, with the values stabilizing in the E1, E2, and E3 horizons at 1.1 to 1.2 mg/kg-1. The highest concentrations occurred in the Bh horizon with mean values of 27.8 mg/kg-1. The HAAS contained more Ext P than the HANS (Table 4-4). Extractable P content of anthropogenic soils increased distin ctly in all horizons. The greatest value of extractable P occurred in the E2 horizon with 383.2 mg/kg-1, where morphological alteration was most prominent. Concentrations of Ext P in the HAAS for the A horizon was 64.3 mg/kg-1 and 130.8 mg/kg-1 for the E2 horizon. Concentrations of Ext Ca in the HANS ranged from 3.2 to 23.4 mg/kg-1 with the lowest value occurring in the E2 and the highest amount in the Bh horizon (Table 4-4). Concentrations of Ext Ca decreased with depth from the Ap horizon (7.4 mg/kg-1), until the Bh. Overall values of Ext Ca in the HAAS were significantly highe r in all horizons. Concen trations of Ext Ca
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99 content for the anthropogenic soil ranged from a low of 339.7 mg/kg-1 in the E2 horizon to 1390.8 mg/kg-1soils in the E1 horizon. The Ap horizon al so had an elevated concentration of extractable Ca in the HAAS. The HANS contained lower overall values of Mg than the HAAS. (Appendix C-4). Concentrations of Ext Mg in the HANS ranged from 1.4 to 47.6 mg/kg-1, with higher values in the Ap and the lowest values occurring in the E3 horizon. The concentration of Ext Mg in the HAAS also decreased with depth with values from 130.1 mg/kg-1 in the Ap horizons to 9.8 mg/kg-1 in the E2 horizons (Table 4-4). The HANS from the site were used as the control for determination of suspected anthropogenic soils. The HANS from the site area were much lower in extractable P, Ca and Mg concentrations and variability than from the anthropogenic soils (Appendi x E-4). Extractable P values differed in the HANS than from the HAAS (t = -2.97, p = 0.0934) (Appendix E-4). The mean for the HANS was 9.65 mg/kg, while the H AAS had a mean of 85.6 mg/kg. The overall Ca values of both the HANS and the HAAS were signifi cantly different. Concentrations of Ca in all horizons (t = -2.87, p = 0.0601) varied between soils . Variability of Ca values is reflected in the standard deviation that is more than ten fo ld that of the HANS (Appendix E-4). The overall concentrations of Mg did change between the HAAS and the HANS (t = -1.71, p = 0.1751), but not with the significan ce of Ext P and Ca. GPR-Soil Results for the Historic Archaeological Site The 500-MHz antenna The natural soil of the HANS has a diverse ma trix with variation in physical properties between the E and Bh horizon (Figure 4-17). The Imm okalee series at this site has clear, abrupt spodic horizon at approximately 0.74 to 0.93 m. Th is Bh horizon is evident in the GPR profile from the 500-MHz antenna. Bioturbation, such as tr ee roots, are evident at depths less than 1
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100 meter (Figure 4-17). The GPR profiles of the HA NS and the HAAS are along different transects, but with 25 m of each other. The length of the GPR transect for the HANS is 3 meters; while the GPR transects of the HAAS are 2 to 3 meters in length. The length of the anthropogenic GPR transects were based on the size of excavation unit coverage. In the GPR profile, wall fall debris, wall footer and a floor from a structur e are highlighted in Figures 18 and 20. Identical processing steps for the horizontal and vertical correlation of the GPR profiles for the natural soils and the anthropogenic soil at the Newberry cemetery, Oakland cemetery and the prehistoric site were used for the historic site. This includes marker interpolation for distance (meters) and static correction time cuts for the removal of antenna ringi ng (Figure 4-17a-c). In order to accentuate and highlight the Bh horiz on interface, spectral whitening was applied to profiles when necessary (Figure 417b). This step was primarily for highlighting the presence or absence of the altered, heterogeneous HAAS, but was also used for the homogenous nature of the soils at the site area. A pick was inserted into selected profiles to highlight subsurface amplitude value changes. Such changes included a Bh horizon and wall footer. The GPR profiles of anthropogenic soils at the Historic site produced distinct planar anoma lies in both the E1 and E2 horizons. Medium to high-amplitude reflections with significant ener gy returned to the 500MHz antenna, enabling a distinct signal return separate from the surrounding matrix. This is demonstrated with the presence of pronoun ced horizontal banding within the anomaly Background filters allow for a clearer image of an already distinct anomaly. With the application of spectral whitening, any contra st between archaeological featur es and the overlying soil is enhanced (Figure 4-18c). The use of Gray1 co lor scale enables the operator alternate data interpretation.
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101 A Bh horizo n Palm root C Bh horizo n Palm root B Bh horizo n Palm r oot A Bh h o riz on Palm r oot Figure 4-17 Ground penetrating ra dar profiles of a natural Aren ic Alaquodos using the 500 MHz antenna. A) Background filter is applied and antenna noise is removed. B) Spectral whitening processing step is added to b ackground filtering, note the increased contrast between the E and Bh horizon. C) Background filter is applied, antenna noise is removed and Gray 1 color scale is used. Contrast is further enhanced between the E and Bh horizon.
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102 C A w a llf oote r fl oo r Wa ll f a ll B Wa ll f a ll Wa ll f a ll w a llf oote r w a llf oote r fl oo r fl oo r Figure 4-18. Ground-penetrating ra dar profiles of an anthropoge nic Arenic Alaquods using the 500-MHz antenna. Wall footer, wall fall a nd floor are highlighted. A) Background filter is applied and antenna noise is rem oved. B) Spectral whitening processing step is added to background filtering. C) Backgr ound filter is applied, antenna noise is removed and Gray 1 color scale is used. Contrast is further enhanced. The 900-MHz antenna The GPR profile with the 900-MH z antenna exhibits no distinct reflections throughout the E horizons of the HANS (Figure 4-19). The palm tree root is less distinct with use of the 900-MHz antenna, than with the 500-MHz antenna. The extent of the Bh horizon is less evident in the GPR profile using the 900-MHz antenna. Data acquisi tion of both the HANS and the HAAS with the
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103 GPR using the 900-MHz antenna created shorter wavelengths, thereby sacrificing depth of resolution (Figure 4-20). Figure 4-19. Ground-penetrating radar profiles of a PANS us ing the 900-MHz antenna. A) Background filter is applied and antenna noi se is removed. B) Spectral whitening processing step is added to background filte ring, note the increased contrast between the E and Bh horizon. C) Background filter is applied, antenna noise is removed and Gray 1 color scale is used. Contrast is further enhanced between the E and Bh horizon. A Bh horizon Palm roo t C Bh horizon Palm roo t A Bh horizon Palm roo t
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104 A B C Wa ll f ooter Wa ll f ooter W all f oo t er W all fall W all fall W all fall Fl oo r Fl oo r Fl oo r Figure 4-20. Ground-penetrating ra dar profiles of a historic ar chaeological anthropogenic soil using the 900-MHz antenna. Wall footer, wall fall and floor features are labeled. A) Background filter is applied and antenna noi se is removed. B) Spectral whitening processing step is added to background f iltering. C) Background filter is applied, antenna noise is removed and Gray 1 color sc ale is used. Contrast is further enhanced between the soil matrix, wall footer, wall fall and floor. The changes in depth of resolution for the 900MHz antenna created th e need for a cropped profile for the anthropogenic tran sect. The remnant of wall footer is evident in the GPR profile using the 900-MHz antenna; however the collapse of the wall a nd the underlying floor of the structure are less discerna ble as compared to the use of the 500-MHz antenna.
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105 Summary The suitability of GPR on the four selected sites (Newberry and Oakland cemeteries, prehistoric and historic archaeo logical sites) had varying resu lts based on soil properties and anthropogenic context. Both physical and chemical soil properties influenced the performance of the GPR in terms of detecting discontinuities within natural soil environments. There are significant differences between the levels of extr actables Ca, P, and pH of soils sampled from both the natural soils and anthropogenic soils at each site. Overall levels of extractables Ca, P, and pH in the anthropogenic soils were significantly higher than the natural soils. Differences between natural and anthropogenic soils were not always well expressed for every site in the physical properties of the sampled soils. Elevated levels of P, Ca, and pH were often independent of the physical properties of an thropogenic soils. Overall values of EC and OC had no significant correlation among either anthropogenic soils or natural soils between the four site areas.
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106 CHAPTER 5 DISCUSSION The general objective of this study addressed the use and limi tations of ground-penetrating radar as an important geophysical tool for archaeo logical applications. GPR has been used as a pedologic and archaeological tool in Florida and throughout the world (Batey, 1987; Doolittle and Miller, 1990; Kong et al., 1992) for more than two decades. Knowledge of the soil environment in an archaeologi cal site beforehand may determ ine the potential success for the application of GPR. The use of geophysical tool s in an archaeological context does not work well in some instances, while in other circumstan ces, it will perform quite well. This is based on the pedologic parameters. Many GPR operators ha ve a limited knowledge of soils properties and the general suitability of the soils within th eir areas of research (Doolittle et al. 2002). Understanding the soils in an area, the operato r of the GPR will be able to make some predictions on how well the GPR will perform be fore going into the field (Collins 1992). Overall, the use of GPR has become increa singly popular based on technology and cost. Equipment has become more affordable and soft ware easier to operate. The efficacy of GPR in archaeological applications is based on the soil properties and what quest ions are being asked by the archaeologist. The use of GPR for a specific archaeological s ite may vary within the site based on subsurface targets or features. This stu dy has determined that there are distinctive and varying results on the use of GPR among archaeol ogical sites. While the four study site have been selected to demonstrate and asses the su itability of GPR with diverse soils in an anthropogenic context; this research has also pr ovided the opportunity to study parameters of various processing techniques. Each site offe red unique challenges; they will be discussed individually and related together , in order to assess the similarities and differences among anthropogenic influences.
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107 Newberry Cemetery Newberry cemetery and its anthropogenic imp act on the soil offered distinctive targets for the use of GPR. Varying soil textures in the natural soil create a wide array of subsurface reflections and distinct interfaces. Soil strata at this site were somewhat convoluted, yet were not so complex that the graves could not be identifi ed. Alfisols are the soils that dominate the site area; they are classified by an argillic subs urface horizon. Because of their high absorptive capacity for water and exchangeable cations, the argillic horizon will produce high attenuation losses (Daniels, 2004). Underlying th e argillic horizon is soft lim estone. The depth to limestone is variable throughout the site ar ea, ranging from 40 cm (Pedro soil series) to >80 cm (Jonesville soil series). Calcium carbonates from the limerock will increase pH values in the soil and may increase radar attenuation. When taken in context to surrounding geomor phology, uniformity in ra dar profiles enable the operator to distinguish suspected graves fr om undulating subsurface horizons. This was the scenario at the Newberry cemetery; multiple disc ontinuities in the soil from natural occurrences contrasted any linear, anthropogeni c influences in the soil. Bevan (1991) stated that the natural soil have a planar stratification, thus the mixed soil that fills the grave shaft could be detectable with GPR. This is also possible when the natural soil does not have planar stratification. The soil that filled two grave shafts at the Newberry site had both clay and lim erock within the mixed matrix (Figures 4-5 and 4-7). The attenuation and the major scattering from the grave shaft allowed distinct anomalous low amplitude reflec tions in the GPR profile. Conyers (1997) refers to the convex and concave reflections to be ‘illuminated’ by the radar beam as the antenna passes over the anomaly. In order to determine the extent of unmarked or clandestine graves at the Newberry site area using GPR, an overall unders tanding of the natural soils wa s paramount. The role of GPR
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108 for this site was to differentiate and assess th e important reflections or subsurface interfaces germane to the soil conditions in the area. A comprehensive understa nding of soil morphology from the surrounding area enables the GPR operator to accurately assess subsurface dissimilarities germane to the site. GPR can ge nerate approximate images of soil profiles (Vaughn, 1986) with reflections caused by contrast s in dielectric constant, yet with multiple subsurface dissimilarities context of soil conditio ns is important. One particular problem with natural alteration of the soil horizon for this site was root ball invers ion. This concern was specific to this site and with th e soil conditions that were associ ated with Alfisols, made this challenge somewhat distinctive. The Newberry cemetery has a Pedro-Jonesville complex, with an argillic horizon and limestone that varies in depth. Depth to limesto ne has a significant imp act on the propensity for root ball inversion. The thickness of the soil will affect root growth and the stability of trees. Native tree cover for the site included mature la urel oaks (Quercus la urifolia) and live oaks (Quercus virginiana). Three mature laurel oaks had fallen during the same time period within 50 m proximity of the site. The root ball inversions created curvilinear voids within the soil matrix. This series of root ball inversions had similar dimensions to the su spected graves in the site area; one in particular had a depth of 1.25 m, length of 1.5 m and a width of 1.2 m (Figure 5-1). The general path of the three fallen trees was to the southeast. This left a northeast to southwest curvilinear void in the soil matrix, unlike the east to west direction of mo st Christian burials. Bioturbation is not exclusive to cemetery or arch aeological sites in general, however the impact on the soils in the site often have unique properties.
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109 Figure 5-1. Example of a root ball inversion caused by severe weather in Newberry cemetery area. Curvilinear void of depression resemble s that of existing graves at the site. The soil properties of the Newberry cemetery are conducive to the ap plication of GPR for the detection of graves. Even though the presence of clay has been described as a limiting factor in limiting the detection of grav es with the use of GPR (Unterberger, 1992), this was proven otherwise for this site. Useful characteristics that may help discern a suspect target with a weak response is a gap or a break in th e argillic horizon due to attenuation in the clay horizon (Schultz, 2003). This was evident in two graves identified at the site. Both graves had abrupt changes in the GPR profile along the interface of the E and Bt horizons. Attenuation and energy scattering in the GPR profiles revealed abrupt demarcation of the natural soil with the anthropogenic soil. GPR profiles identified both location and approximat e depth of the graves due to combination of attenuation and scattering (Figures 4-4, 4-5). A linear void is outlined in the GPR profile with overlying mixed soil or overburden (Figure 5-2).
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110 Grave Transect 22 Figure 5-2. GPR profile at Ne wberry cemetery of transect 22 using 500-MHz antenna. Grave is outlined demonstrating how a vertic al feature produces scattering. The three GPR profiles highlighted in this re search are the two known graves of transects 14 and 22 and the natural soil in transect 17. The two graves along transect 14 and transect 22 had very similar GPR profiles, with linear featur es and overburden. The natural soil transect (Figure 4-3) demonstrate th e undulating subsurface conditi on of the argillic horizons. Coordinates of transects ar e listed in Table 5-1. Table 5-1. Coordinate positions of the Newberry cemetery of selected transects and location of graves. Transect Coordinate Position Remarks 14 82 36’ 14.41 W / 29 40’ 02.43 N Grave shaft detection with overburden. 17 82 36’ 14.29 W / 29 40’ 02.39 N Argillic is present in GPR profile. 22 82 36’ 14.18 W / 29 40’ 02.51 N Grave shaft detection with overburden. Oakland Cemetery Even though the soil properties of the Oakl and cemetery are conducive to the application of GPR for the detection of grav es, the GPR profiles contrasted significantly from the Newberry cemetery. The well-drained soil Lamellic Quartzip samments located within the site boundaries enabled the detection of two graves along the same transect with the GPR. GPR is highly suited
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111 to most application in dry or well-drained sands with a wide range of frequency antennas (Smith and Jol 1995, Doolittle and Collins, 1998). Bo th the 500-MHz and 900-MHz antenna were successful in the acquisition of targets. The so mewhat homogenous nature of the Candler soils enables the GPR to acquire most anthropogenic anomalies. The OCNS are slightly acidic with a pH range of 5.9 to 6.6 along transect 2. These pH values are higher overall than values recorded fo r the Candler soil series. Candler soils have pH values from 4.5 to 6.0 (Doolittle and Schellent rager 1989). Higher recorded pH values for the OCNS may be attributed to the influence of citr us cultivation upslope of the tested site area. Extensive agriculture has dominated the area and this can be seen in the aerial photograph from 1947. Secondary anthropogenic influences may have impacted the primary suspected graves in transect 2; chemical leaching coupled with perm eable soils had a possible affect on the sampling results. Soil influences taking place with older graves have profound affects on the ability of GPR to identify targets. Over time it is difficult fo r the GPR to detect bones due to their small size, loss of mineral components and because of similar electrical properties to the dry soil (Schultz 2003, Davis et al. 2000). Along tran sect 2, from 35 to 50 cm, pH concentrations in the OCAS were 7.2 compared to 6.6 for the OCNS. EC at the same sampled depths along transect 2 were only 0.14 ds/m-1 in the OCAS and 0.08 ds/m-1 in the OCNS. The range of pH was more variable than the EC. Elevated values of pH corresponded with the elevated values of extractables Ca and P. Concentrations of extractables Ca and P had significantly higher values for the OCAS as compared to the OCNS (Table 4-2). Soil ch emical properties of the OCAS had varying influences on the selected GPR anomalies. EC was not affected by the substantial increases in
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112 extractables P and Ca. This is not a surprise si nce EC is a measure of total concentration of dissolved salts. Increase of ex tractables Ca and P in the soil matrix surrounding the anomaly provided a high enough contrast to produce an increase in signal reflections. A historical background of the site area enables the GPR ope rator to fully utilize the equipment and adjust the parameters accordingl y. Anomalies identified along GPR transect 2 occurred at shallow depths, 30 to 50 cm. Historic al accounts by local residents revealed specific details of random burial procedures . Migrant workers in the area fo r the harvest of citrus crops were often buried along the perimeter of th e cemetery (OR9567) (p ersonal communication, Deacon Moore). The two point source anomalies along transect two were 18 m east of existing grave markers, upslope. Bevan (1991) discusses cu ltivated next to non-cultivated boundaries as possible landuse indicators for a cemetery. Less than 10 m to th e east of transect 2 is an abandoned citrus grove. Vertical spatial scale also has significance in the determination of clandestine graves. The depth of most forensic bodies will be less th an 1 meter (Schultz, 2003 ), and in the Oakland cemetery, both suspect anomalies were at depths less than 70 cm. Prio r knowledge of varying burial practices at the site required multiple settings in both range and antenna frequency. The contrast of the point source anomalies were dist inct enough to exhibit hyperbolic reflections. The range or depth of viewing for the GPR was at a de pth of 1.6 m. This setting enable both the 500MHz and 900-MHz antennas to di scern suspected targets. African American burial practices were quite di fferent from that of the white community in the late-nineteenth and early-tw entieth centuries. After a person had died, the body would be laid out on a cooling board in the home for viewing and to make sure the individual was indeed dead (Deacon Moore 2006: personal communication). Em balming did not occur and bodies were
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113 placed in wooden boxes or in fabric. Such burial practices often lead to poor preservation of human remains in the OCAS over long periods of time. Thus, the radar profiles (Figure 4-9) reveal only three reflections bands, or half cy cles associated with both suspected graves. Historic Archaeological Site Application of GPR in an archaeological cont ext often has mixed resu lts. Locating graves with GPR often have dichotomous results; either the grave is present or absent in the soil. Archaeological investigations with GPR entail many different questions. Various archaeologists view GPR as way of only identifying buried anomalies (Sternberg and McGill 1995, Conyers 2004), yet post-processing of data enable more information than just prospecting. Also, archaeology has a significant contribution to offer GPR operators in terms of verifiable data from the field. In this historical archeological site, GPR profile in formation was collected prior to excavation. Like all archaeol ogical excavations, photographs, pl an view maps and profiles documented the information collected. GPR data was processed and compared to the archaeological information afterwards. Both anthropogenic context and soil conditions determined the selection of this site. The comparison and contrast of differe nt frequency antennas in a historic site was also conducted to better distinguish subtle changes in the shallow site area. Other research has demonstrated the differences in data quality that varies with ante nna frequencies and the ty pes of data analyses used to display the final product (Neubauer et al. 2002; Goodman et al. 1998; Conyers 2004). Improved processing software has established verifiab le differences in field data collection. With multiple frequency antennas used at a site, overlapping data sets are able to be recorded by the GPR and processed. Post-processing of GPR data is imperative for an accurate assessment of subsurface anomalies.
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114 An additional benefit from GPR surveys of an active archaeological site is the integration of physical data with the geophys ical acquisition with remote-sensing. The archaeologist is capable of assessing GPR data in the field prior and during excavat ion. Often a field archaeologist will examine a wall profile and only be able to interpret general features, color change or even texture change. GPR allows arch aeologists to differentiate important subsurface interfaces. Dissimilar physical or chemical prope rties between two materials in a soil matrix identified by GPR reflections will otherwise be missed by even the most trained eye in the excavation unit. Conversely, archaeological prof iles and plan view ma ps will often recognize discrete features in greater detail. Also, ther e are circumstances where the GPR operator actually sees the same thing the archaeologist sees and vice versa. In Figure 5-3, the wall footer/trench is visible in the photograp h of the excavation unit. The dark er color soil ov erlying the wall footer/trench is the floor base of the structure. Both the floor and debris from the collapse of an adjoining wall are apparent in both th e profiles produced by the 500-MHz and 900-MHz antennas (Figures 4-18 and 4-20). Disparate soil colors are clea r in the photograph (Figure 5-3) and in the GPR profiles a corresponding change in the RDP of the subsurfa ce features (Figures 4-18 and 4-20). Collins and Shapiro (1987) from their study at the San Luis Mission archaeol ogical site, discuss the use of soil morphological features to distinguish from anthropogenic features. Th is includes examples of abrupt smooth boundaries between soil layers, dark matrix colors and mixed soil textures extending into natural soil horizons. Soil chemical properties are quite different between the HANS and the HAAS as well. Extractable Ca values are low for the HANS, w ith a range of 3.2 to 23.4 mg/kg. Unlike the
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115 Floor with overlying wall fall. Figure 5-3. Photograph of excav ation unit from the historical archaeological site. Wall footer/ trench is located in southwest corner of unit. Ground-penetrating radar profile of transect (Figure 4-18 and 4-20) associated w ith wall footer and floor and wall fall in photograph is evident. Photogra ph courtesy of E. Carlson. HANS, the HAAS had extractable Ca values substa ntially greater with values of 339.7 to 1390.8 mg/kg. In the excavation unit numerous small frag ments of limerock were observed in the buried floor matrix in the profile. Extractable P was a good indicator for that site because the mean values in the natural soils were significantly lower than the anthropogenic soils. Extractable P concentrations increases corres ponded with extractable Ca in depth, though P had lower overall values. EC values are double in the HAAS when compared to the HANS. Multiple reflections of contrasting layers associated with the wall fall and floor features (Figures 4-18) are due to changes in RDP and may partially denote increased ionic activity. Artifacts associated with the HAAS are not very large and co mmonly did not exceed 10 to 15 cm in length. Assemblages of marine she ll were located throughout a majority of the excavation units. Small point source anomalies were not visible in a majority of the GPR profiles Wall footer from transect 1
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116 using the 900-MHz antenna. Even with the higher frequency antenna some subtle reflections in the near-field zone of multiple reflections may never be noticeable in standard two-dimensional profiles, but become visible w ith three dimensional models (C onyers 2004). Transects using the 500-MHz and 900-MHz antennas were conducted in both east to west and north to south directions. This was done to aid in feature delineation. The application of GPR on a hi storical archaeological site associated with Spodosols has several benefits. Soil chemical properties of Spodosols in genera l and, specifically the HANS, have low values of EC, pH, and extractables Ca, P, and Mg. Anthropogenic intrusions for a substantial period of time will have chemical sign atures that will outlin e a site area and any amendments to the soil would be evident with HANS . The EC of soils will in crease if clay, water or soluble salts increase as well (Daniels 2004). This was not the case with the HANS. The HANS has an ochric epipedon and an albic subsurface horizon, with a water table greater than one meter at the time of the research. If res earch was conducted in a di fferent season, a higher water table may have affected the re sults of the GPR survey at this site due to an increase of EC. Vertical limitations of the HANS may be dependent upon depth to the spodic horizon. Abrupt changes in the Bh horizon would most likely have a pronounced subsurface gap in the GPR reflection. Overlying albic horizons are commonly comprised of medium to fine quartz sands. Areas dominated by mineral soil materials with less than 10 percent clay or with deep organic soils with pH values<4.5 in all layers have very high potential for GPR applications (Doolittle 2005). The HANS had soil with little or no clay and a spodic horizon > 90 cm. GPR was able to distinguish subsurface features in th e HAAS due to the shallow depth of the site and soil properties conducive to radar propagation.
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117 Prehistoric Archaeological Site Detecting subsurface features or artifacts fr om a prehistoric archaeological site have varying degrees of success. Most geophysical inves tigations at a prehistori c archaeological site are conducted to locate a section of the archaeological fe atures buried (Dal an and Bevan 2002; Conyers and Goodman 1997).The great er temporal scale of the site , the greater the challenge of detecting identifiable features with GPR. Often the only evidence of prehistoric sites is the truncated horizons of culturally modified soil. Depending upon the soil, this may prove difficult. Cultural middens often contain la rge concentrations of base cations, yielding clues for GPR operators through acute and discre te attenuation. Frequently, resu lts are achieved with the GPR on older prehistoric sites, but only after extensive data processing. Research was conducted at the prehistoric ar chaeological site (8LA 243) to document the suitability of GPR with the soils in an archaeo logical context. Howeve r, to demonstrate the differences between the PANS at the site with the PAAS with the GPR entailed an underlying challenge of conducting a survey in an active citrus grove. In orde r to determine the presence of the PAAS any anthropogenic influence incurred in the last century of human activity had to be differentiated. Modern human modification of the landscape often has symmetrical, linear patterns and distinct vertical sh afts in the soil as opposed to ancient human patterns (Holliday 2004). Irrigations pipes, as well as trenches, transected the citrus groves in numerous directions and at alternating depths in the soil. Physic al and chemical alteration of the soil occurred throughout the site area. The soil properties of the PANS satisfied the re quirements of an Inceptisol, with an umbric epipedon and a pH of <6.0. A uniform umbric epipedon (40-50 cm) existed across much of the site area, with shallower depths existing upslope. Physical properties of the PANS did not change between the A horizon and the underlying C horiz on. Color change (Appendix A) is the only
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118 major distinction involving the PANS horizons. Si milarly, the PAAS have only color difference to distinguish horizons; partic le size changed insignificantly in both the A and C horizon. A contrast in geophysical properties, however, is not necessarily indicative of a cultural origin. There are many natural processes that may also produce such changes (Dalan and Bevan 2002). The GPR profile (Figure 5-4) of the PANS using the 900-MHz antenna is ab le to illu strate the interface of the A and C horizons. Figure 5-4. Ground-penetra ting radar profile (GPR) of the prehistoric archaeological natural soil (PANS) using the 900-MHz antenna. GPR profil e of transect 3 Profile is in Gray 1 color scale with spectral whitening to contrast soil horizon change. Soil chemical properties had the greatest in fluence of distinguishing between the PANS and the PAAS. Concentrations of extractables P, Ca, and Mg in the PAAS had higher overall values than from the PANS; even though the samp les from the PANS were within the citrus grove. The PANS samples were collected upslope from the PAAS. Prehistoric human impact has altered the soil along the shores of Lake Apopka, especially in the form of middens. Soils around dwellings or middens have been shown to be high in phosphate con centrations, often bonding with Ca (Macphail 1981; Sandor 1992). Possible accu mulation of chemical runoff down slope in the cultural middens areas associated with the PAAS may also explain the higher overall values of pH, and extractables Ca, Mg, and P. The entir e site area has been impacted by current human influence, either directly or indire ctly over the past several decades. A Horizon C Horizon
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119 GPR transects at the prehistoric site (8 LA243) exhibited no signi ficant difference in resolution between the 900-MHz and 500-MHz antenna s, aside from depth of penetration. Both GPR antennas were able to dist inguish soil horizons and human-p roduced anomalies, such as irrigation pipes. Prehistoric features, such as refu se pits or hearths were suspected targets for the GPR. Culturally emplaced soils may be have elec tromagnetic dissimilarities either because of firing or through the addition of fired products (Dalan and Bevan 2002).This was a possibility at this site, however results prove d inconclusive. Modern anthropoge nic features convoluted the radar reflection from suspected prehisto ric features along se lected transects. Modern alteration of the soil environment is evident throughout the s ite area. A discrete physical modification in the soil of an abandoned excavation unit is illustrated in Figure 5-5. The vertical truncation of the soil is apparent. Stratification of the darker mixed soil is gradually filling-in with the lighter mixed soils. The dark er color of the umbric epipedon overlying the lighter C horizon is seen on either side of the imp acted soil. This is an example of a soil matrix that would produce side-scattering in a GPR profile. Down slope from citrus g rove Figure 5-5. Photograph of soil in abandoned excavation unit from the prehistoric archaeological site. Example of truncated soil from anthr opogenic alteration adjoin ing a citrus grove.
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120 Ground-Penetrating Radar Comparisons At all four research sites both the 500-MHz and 900-MHz antennas were used in order to compare the efficacy of the GPR on four different soil orders. There were slight differences between the two antennas for cemet ery applications. Possible probl ems may have existed if only one frequency antenna was used. Anomalies belo w a certain depth may be missed entirely with the GPR if a higher frequency antenna was used. C onversely, features or targets may be obscure due to weak reflections close to the surface for lower frequency antennas. Comparing and contrasting GPR profiles with different antennas will often aid in discerning common reflections in both, either as potential targ ets or background clutter. There ar e benefits and disadvantages for either antenna frequency, depending upon the application and the soil. GPR-Cemetery Using the GPR with the lower frequency 500MHz antenna had no limitations in detecting suspected graves in both the NCAS and the OCAS. The 900-MHz antenna may have difficulty with similar graves in Alfisols if the argillic horizon was deeper than a meter. Any break or gap in the argillic horizon could possi bly be attenuated with the 9 00-MHz antenna, and thereby not discern a buried target (Schu ltz 2003). With natural soils the 900-MHz antenna had slight limitations, but for the same reason as the possible problems of the NCAS, detecting the argillic horizon below a certain depth. The radar waves of the GPR using the 90 0-MHz antenna spread and attenuates with depth and may be recovered to some extent with pos t-acquisition processing, through gain control (Shih and D oolittle 1984; Jol and Bristow 2003). Using the GPR with the 500-MHz antenna is capable of detecting subsurface targets without excessive reflections of secondary and tertiary anomalies. A setback encountered with the 900-MHz antenna is the higher frequency an d higher amount of background clutter in the soil. Numerous roots, burrows, lime rocks and ge neral bioturbation are co mmon in most soils.
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121 Depending upon the soil environment, this may be overwhelming for field determinations of moderate to small size targets if using the GP R with the 900-MHz antenna. In the NCAS and NCNS, a significant amount of lime rock and tree roots were widespread in all soil horizons. Many of these unwanted GPR reflections were reduced with the use of the 500-MHz antenna; thereby the contrast of any buria ls in the soil was increased. If suspected targets are acquired with the GPR using the 500-MHz antenna, a sec ond transect may be conducted with the 900MHz antenna augment the survey with supplementary data. In most cases, the 500-MHz antenna out performed the 900-MHz antenna in both cemeteries. Resolution with the GPR using th e 500-MHz was not sacrificed in terms of distinguishing suspected clandestine or unmarked graves. Subtle reflections within the radar profiles were evident in both ante nnas. The hyperbolic tails of the two suspected graves in OCAS were less distinct with the higher frequency antenna. Of the two cemeteries the 500-MHz antenna performed better in the OCAS than in the NCAS. Unlike the NCAS, the soil in the OCAS provided no limitations for the acquisition of targets; the absence of clay and high ionic activity limited the pote ntial of attenuation for both the 900-MHz and 500-MHz antennas. GPR-Archaeological Sites The GPR had contrasting results in both arch aeological sites. The different frequency antennas were not significant factors in the genera l performance of the GPR. Application of GPR in an archaeological context often has multiple goals, and the use of multiple antennas allows for the accumulation of multiple data sets. With the P AAS, the limitations were not specific to either antenna, but to the anthropogeni c context. The GPR with the 500-MHz antenna ha d better radar penetration than the 900-MHz antenn a; however resolution was not sa crificed due to the depth of suspected targets.
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122 At high frequencies, material near the surf ace may have both detrimental and beneficial influences upon the performance of the GPR. This was a impending consequence with the 900MHz antenna in regard to the HAAS. Cultural mate rial and historic feat ures located within 40 cm of the surface had the propensity to retain wate r. The earthen floor and fallen wall were quite different in composition and diel ectric properties than from the HANS. Materials saturated with water, such as mortar, coquina, and limestone, w ill exhibit higher than normal energy attenuation (Annan and Cosway 1994). Conversely, Daniels states (1996) a small amount of moisture has the capacity to accentuate radar reflections in th e GPR profile, thereby highlighting specific anomalies. This was neither the case in th e HAAS. The GPR with the 500-MHz antenna was better suited for the acquisition of features; both the floor and the fallen wall were more identifiable than when the higher frequency antenna was used. Summary GPR has numerous applications, all of whic h are non-invasive. In archaeology much of what is studied is destroyed, an excavation cannot be undone. Also, as all archaeologists know well, any mistakes that are made in the field are compounded later in th e analyses, results and report. Unmarked graves, if not discovered befo re they are unearthed, will cost considerable amounts of time, money and the possible ire of a community. If old graves are discovered before they are destroyed, irreplaceable cultural informa tion about mortuary rituals and social structure may be retrieved (Tainter 1978; Brown 1981; Main fort 1985). Time, money and cultural heritage are just a few reasons for the application of GPR in an archaeological context. However, GPR is not an archaeological panacea. The use of GPR will not always work well, and sometimes not work effectively at all for archaeological sites and cemeteries. For many archaeologists, soil has been the contex t in which they work instead of the focus of study. A Pedologist st udies the soil as a natu ral body in the environment and humans just get
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123 in the way. The relationship between pedology a nd archaeology has always been beneficial to both. GPR has been used extensively by pedologi sts and archaeologists for survey mapping and site delineation (Vaughn 1986; Collins 1992; Conyers and Cameron 1998). Maps have been constructed based on the State So il Geographic data base (Doo little et al. 2006), showing the relative suitability of soils with GPR. This guide line assists operators to evaluate the relative appropriateness of using GPR in the field. However, this crite rion for pedology does not always apply to archaeology. Principles for the application of GPR as a pedologic tool generally follow the same for archaeology. Specific soil properties exhibit certa in characteristics. In saline and sodic soils, GPR is unsuited to most applications. In wet cl ays the GPR has very low potentials for most applications (Doolittle et al. 2006) . These pedologic principles hol d true for the most part in archaeology as well. Some soils are highly rated fo r general use of GPR, such as sandy materials, highly weathered soils or areas underlain by cr ystalline bedrock (Doolittle and Collins 1998). However some soils that have moderate potential for pedologic applicatio ns with GPR may have unique properties that make arch aeological research advantageous. Both cemeteries in this research had success with GPR in locating suspected graves even though the NCAS and the OCAS cond itions are dissimilar. The NCAS contain 41% clay in some sampled areas, while the OCAS site does not have values greater than 3%. To some extent, lime rock is present in most of the NCAS horizons , the OCAS has none. Soil chemical properties are also disparate in the NCAS and OCAS. The pH, and extractables P, Ca, and Mg values are all significantly higher in the NCAS; both within the NCAS and NCNS as well as between the different cemetery areas. Possible reasons for the successful use of GPR at the NCAS are a combination of the various soil properties.
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124 A great concern for the successful operation of GPR for a site area is the amount of clay in the soil. The penetration depth of GPR is inversely related to the clay content; soils containing 35% clay or more are considered restrictive for favorable usag e (Doolittle et al. 2006). Clays produce high attenuation losses due to their high absorptive capacity for water and exchangeable cations (Daniels 2004). It is also important to note that the same absorptive capacity of clay can act as an indicator for anthropoge nic alteration of a soil, acting as a trace marker for the GPR. This was the case in the NCNS, with two GPR profiles. A truncation of the soil horizon and the subsequent backfill of the grave shaft are highlighted by the increased attenuation due to clay content in an E hor izon (Figure 5-6). Reflection of backfill and grave shaft Ehorizon Figure 5-6. Ground-penetrating radar profile using 500-MHz antenna from the Newberry cemetery anthropogenic soils (N CAS). Along transect 22 a grav e shaft is visible with overlying backfill; the E horizon is depicted. The detection of subsurface anomalies using th e GPR in the field gives the operator realtime information. Decisions can be made almost immediately after the antenna passes the target. For cemeteries, often post acquisiti on data processing is not necessary. If th e coffin, burial vault or an air cavity is still intact, the target will be more easily identified (Bevan 1991, Davis et al. 2000). However, many older graves have woode n caskets that deteri orate over time. Some graves will have no coffin at a ll, possibly just a shroud wrappi ng the body. For example, Schultz
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125 (2003) asserts the GPR will generally not identify ju st the skeletal remains over long periods of time, even when the radar wave penetrat es the backfill and scans the skeleton. Until recently, GPR was used to simply identify the presence or absence of subsurface anomalies. GPR equipment and software processi ng today enables the opera tor to not only locate buried archaeological material, but be an integr al part of archaeologi cal data recovery and research tool (Conyers and Cameron 1998). GPR and archaeological research does work well together, but every site does not have the same potential for the successf ul acquisition of data. Conditions must be conducive to radar propaga tion in the ground; some conditions may change overnight (soil moisture content), while some conditions will never change. Subsurface features may be present in the ground, yet the features mu st be distinct enough to be differentiated by the radar waves from the background soil matrix. The use of GPR in an archaeol ogical context is dependent upon the soil properties. Similar to the conditions of a proper excavation through difficult soil conditions, all sites have different parameters for successful data recovery. The loos e, sandy conditions of the HAAS site were easy to excavate, yet a less sandy texture would have aided in the identification and mapping of features. These same soil conditions had successf ul results for the GPR in terms of radar propagation and feature identification. Unifor m soil morphology throughout the upper 50 cm of the HANS, made identification of contrasting HAAS straightforward for both the archaeology and GPR. An albic horizon in hi storical archaeology is similar to a blank sheet of paper, with most cultural features or arti facts becoming apparent to even the common observer. However, the same properties for albic horizons make it diffi cult for subtle features to retain shape and uniformity during excavation. GPR is a non-destruc tive tool that may identify the feature before excavation and create a ‘snapshot’ of the ta rget, thereby aiding in data recovery.
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126 Historical archaeology has dist inctive advantages over prehistoric arch aeology in Florida; the amount of time a site is exposed to the de structive weathering proc esses being the number one concern. Destructive human impact often wi ll alter the weathering process of surrounding soil. Compaction of the soil, floors from structur es and chemical loading are a few examples of altering a soil environment, which may alter th e process of weathering. Such anthropogenic ‘footprints’ allow the GPR to differentiate between natural soils and human-influenced soils. The GPR had distinct reflections from the HAAS as co mpared to the PAAS, in part due to different periods of exposure to weathering processes. The question is if a GPR survey can differentiate between natural or prehistoric cultural constructed earthen forms in the PAAS and to what extent. Soil forming processes, such as time and biota, at the HAAS had minimal effects on the integrity of the site a nd for the use of GPR; this was not the case for the PAAS. The temporal range at the PAAS ha s Carbon-14 dates from within the middens as early as 1600 B.C. to components as late as 1300 A.D. (Austin 2006: personal communication). Time and biot a had profound effects on the PAAS, both archaeologically and with geophysical operations. Biota, in the form of recent human impact, had an effect on the successful a pplication of GPR at the PAAS. Bo th direct (physical alteration) and indirect (chemical alteration) consequences of current human influence created obstacles for the use of GPR. The amorphous nature of some pr ehistoric features made it difficult to discern archaeological targets from the PANS and recent anthropogenic influences. Archaeological site boundaries ar e not always clear and discrete ; this is also the case with natural soils. Soil delineations are not always homogenous and contain anom alies (Doolittle et al. 2006); some of which may be anth ropogenic. The age of an archaeo logical site and specific soil properties appears to be the constant with all four sites. Both of th e cemeteries date to the turn of
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127 the 20th century, yet the OCAS has the possibility for a higher rate of deterioration from the more acidic soils. The NCAS limitations for GPR due to attenuation from clay also assist in the preservation of the human remains at the site. Cemetery boundaries are mo re discrete than the HANS and PANS, either the grave an omaly is present or it is not. The use of GPR for the HAAS had better result s than the PAAS. Once again both time and soil properties are major factors for the success of GPR in an anthropogenic context. The amount of reflection that occurs at soil and feature boundaries is more evid ent in recently disturbed sites, therefore increasing the amount of data obtained from the GPR. Different frequency antennas used with the GPR assist in either reducing b ackground clutter or augmenting subtle reflections in the soil. This may be important with the length of time a site as altered. Older sites, depending upon depth, may need the higher frequency antennas to capture faint reflections from the less mixed surrounding soils.
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128 CHAPTER 6 CONCLUSIONS The main purpose of this research was to di fferentiate natural and anthropogenic soils in four Florida sites with the use of GPR. GPR research was conducte d to determine to what extent that anthropogenic features could be identified based on soil properties. Data provided by the GPR survey and soil analyses from this study ha ve quantitatively and qualitatively contrast the four distinct anthropogenic sites. Two of the study s ites are cemetery located in Alachua County and Orange County. The two soil or ders associated with these site s are Alfisols in the Alachua County site and Entisols for the Orange County s ite. Another research site is the Montverde prehistoric archaeological site, located in Lake County. The primary soil order is Inceptisol. The fourth site is a British Period hi storic archeological si te. It is located in St. Johns County and the soils are predominately Spodosols. This contrast of the different soil orders in an anthropogenic context has demonstrated underlying differences and similarities fo r the successful applications of geophysical tools. Soil suitab ility of the sites and the app lication of GPR are dependent upon the archaeological conditions. Comparison and inte rpretation of intrasite data was the primary focus of the survey; only after the information was collected was a general intersite assessment concluded. Variations in particle size were interprete d in terms of natural soils and anthropogenic soils. Soil particle distribution had a more si gnificant effect on the determination of an anthropogenic site for the GPR than soil chemical values. This is not surp rising since the greater the differences in particle size within a soil, th e greater potential difference between the relative dielectric permittivity of those materials. The smaller clay-size particles are more reactive and have higher water holding capacitie s than the sand-size particles that predominate most of the soils in Florida. Clay particles in the soil clea rly exhibited the most im portant variable on radar
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129 propagation. Due to the very re active properties associ ated with clay particles, small amounts demonstrated important effects on the subsurface acquisition and interpre tation of GPR targets. Soil chemical analyses from the different sites had noteworthy influences in the differentiation of natural soils and human impact ed soils. Although soil physical properties had a more profound effect on the research sites, selected soil chemical data often reflected the results from the GPR surveys. Soil chemical properties had an impact on the GPR performance. Similar pedologic parameters for the use of GPR apply for archaeological applications, most notably attenuation of radar signals in soils with elev ated ionic activity. Both the PAAS and the NCAS had elevated pH and high concentrations of extr actables Ca and P, thereby influencing the GPR results with using the higher frequency antenna. Both the 900-MHz and the 500-MHz antennas we re used on each site for comparative study. The 500-MHz antenna outperformed the 900MHz antenna at every site in terms of attenuation, imagery, depth of penetration and conical spreading. GPR surveys performed at the two cemeteries had varying results with the 900-M Hz antenna. The higher frequency antenna at the NCAS encountered difficulties w ith attenuation at the base of the grave shaft along transects 14 and 22. With the presence of clay in the grav e shaft attenuation occurred, to some extent, throughout the GPR profile. Extens ive processing augmented the reflections in both antennae; however accurate interpretation of the graves dimensions were less conclusive with the 900-MHz antenna. Using the 900-MHz antenna multiple reflections occurred from numerous rocks, roots and general bioturbation. Similar to the concerns stated by Schultz (2003), excessive detail made it difficult to discern potential targets from the natural soil matrix. Higher frequency antennas have decreased dept h of radar penetration, as well as smaller radar ‘footprints’ or conical spr eading. Intervals between GPR tran sects have to be shorten for
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130 the 900-MHz as compared to the 500-MHz antenna. Thus, additional transects are added. For large site areas extra transects will require additional time in the field, often quite substantial. Another benefit for the use of the 500-MHz was ev ident at the OCAS. Susp ect graves exhibited well-expressed hyperbolic tails in the GPR profiles. For suspect gravesite surveys with the GPR the 500-MHz antenna has distinct advantages ov er the 900-MHz antenna. However, in some situations, a second antenna may prove useful. Overall, GPR antenna preference for bot h the HAAS and PAAS was for the 500-MHz antenna. Once again the same general benefits for the lower frequency antenna applied to two different sites. Attenuation con cerns and suspected target de pths made the 500-MHz antenna preferable over the higher fre quency antenna at the PAAS. Conve rsely, both frequency antennas had no significant drawbacks at the HAAS. Some horizontal bandi ng and antenna noise from the 500-MHz antenna occurred, but not substantial enough to in fluence the detection of any targets. In fact the lower frequency antenna differentiate d historical features in the HAAS to a greater extent than the 900-MHz ante nna in the GPR profiles. For this research, the successf ul application of GPR for arch eological investigations is based on soil suitability. Presumably, this basi s of soil suitability would be linked to the classification of a soil’s Order. However, from an archaeological perspective, this is not necessarily the case. Prio r knowledge of the soil cla ssification that is associ ated with a site is a very general starting point and s hould be perquisite for the use of GPR. The identification of the soil Order was secondary to the di agnostic horizons associated w ith that Order. This may be considered a question of semantics; however a GP R survey for archaeological purposes is based more on the diagnostic horizons of the soil in re gard to the site. An example is the HAAS site; the presence of a spodic horizon was unrelated to the function of the GPR. The successful
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131 application of the GPR with th is historical component was ba sed on the properties associated with the ochric epipedon and the albic subs urface horizon and not ne cessarily the underlying spodic subsurface horizon. Both NCAS and OCAS cemeteries have differe nt relationships with soil properties than the HAAS or PAAS. The NCAS and the OCAS are di screte vertical intrus ions into the natural soil landscape that have occurred over that la st century. As with the HAAS and the PAAS, the soil Order classification is less a fa ctor than the diagnostic horizons in terms of soil suitability for the GPR. With the NCNS depth to the diagnos tic subsurface horizon (argillic) is more a controlling factor for the GPR than the whether the soil Orders are Ultisols or Alfisols. Grave shafts in the NCAS have the pot ential to remain intact substant ially longer than any detectable remains, due to the argillic horizon. Conversely, the OCAS burial remains have already outlasted any grave shafts that were present. Soil classification may be confusing to non-pedologi sts; after all it is difficult to get most pedologists to agree on some fundamental nomencl ature. Soils associated with the OCAS are classified as Entisols, which are recently de veloped soils. Yet the di fference between Entisols and the highly weathered, old soils of Ultisols may be a matter of only a few centimeters difference in horizon placement of a diagnostic hori zon. In either case, soil Order classification had no bearing on the suitab ility of GPR on this gravesite. If the site contained Ultisols with an argillic horizon only a few centimeters from the surface, there might be significant issues involving the GPR. Soil classificatio n has an important role with th e selection of a archeological site’s suitability for the use of GPR. Prior knowledge of the soils associated with a site is no different from any other information gather ed by archaeologists before they commence excavation; but for the use of GPR it may be essential.
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132 APPENDIX A SOIL DESCRIPTIONS Table A-1. Official description of Jonesvil le soil series in Alachua County, Florida. TAXONOMIC CLASS: Loamy, siliceous , hyperthermic Arenic Hapludalfs A1 to 17 cm; dark gray (10YR 4/1) sand; we ak fine granular stru cture; very friable; common fine and medium roots; medium acid; clear wavy boundary. E1 to 42 cm; pale brown (10YR 6/3) fine sand; single grained; loose; common fine and medium roots; neutral; clear wavy boundary. E2 to 72 cm; very pale brown (10YR 7/3) fine sand; single graine d; loose; few fine and medium roots; neutral; clear wavy boundary. B2t to 82 cm; brownish yellow (10Y R 6/6) sandy clay loam; weak medium subangular blocky struct ure; friable; few fine and medi um roots; sand grains are well coated and bridged with clay ; neutral abrupt wavy boundary. R to 200 cm; white (10YR 8/2) limest one that can be dug with light power equipment such as a backhoe; moderately al kaline; the pedon had a 14 by 33 inch deep solution hole extending into the limestone, which contained strong brown (7.5YR 5/6) sandy clay loam between depths of 82 and 130 cm and sandy clay between depths of 130 and 165 cm; moderate medium subangular blocky structure; friable a nd firm; few distinct clay films on faces of peds; few fine nodul es and fragments of limestone; neutral. DIAGNOSTIC HORIZONS: Ochric epipedon and argillic horizon Adapted from Thomas BP, Cummings E, Witts truck W.H. 1985. Soil Survey of Alachua County, Florida. United States Department of Agriculture, Soil Conservation Service. p. 126.
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133 133 Table A-2. Soil description of Jonesville seri es at the Newberry Cemetery natural soils (NCNS) SOIL SERIES: Jonesville CLASSIFICATION: Loamy, siliceous , hyperthermic Arenic Hapludalfs GENERAL LOCATION: Davis Cemetery, Newberry, FL SOIL DESCRIBED BY: Christophe r Chilton (Bucket auger) Date: March 30, 2006 Ap to 4 cm; dark gray (10YR 4/1) sand; weak fine granular st ructure; common fine and medium roots; abrupt wavy boundary. E1 to 53 cm; light brownish gray (10YR 6/ 2) fine sand; single grained loose; common fine and medium roots; gradual boundary. E21 to 75 cm; very pale brown (10YR 7/3) fine sand; few dis tinct reddish (2.5YR 4/6 redox accumulations; single grained loose; few fine and medium roots; gradual boundary E22 to 93 cm; light gray (10YR 7/1) fine sand; single grained loos e; few fine roots; sand grains are uncoate d; abrupt boundary. Bt21 to 104 cm; yellowish brown (10YR 5/6) fine sandy loam; weak subangular blocky structure; friable; fe w fine and medium roots; few phosphatic limestone nodules; sands grains are well coated and bridged with clay; clear boundary. Bt22 to 137 cm; yellowish brown (10YR 5/6) sandy clay loam; weak medium subangular blocky; friabl e; few fine and medium roots; sand grains are well coated and bridged with clay; gradual boundary. R to 143 cm; white (10YR 8/2) limestone. DIAGNOSTIC HORIZONS: Ochric epipedon and argillic horizon
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134 134 Table A-3. Official descri ption of Candler soil series in Orange County, Florida. TAXONOMIC CLASS: Hyperthermic unc oated Lamellic Quartzipsamments. A--0 to 12 cm; dark gray (10YR 4/1) sand; si ngle grained; loose; few fine and medium roots; many uncoated and thinly coated sa nd grains; some mixing of light yellowish brown (10YR 6/4) in lower 1.0 inch to 1. 5 inches; strongly acid; clear wavy boundary. (2 to 8 inches thick) E1 to 67 cm; yellow (10YR 7/6) sand; sing le grained; loose; few fine and medium roots; many uncoated sand grains; st rongly acid; gradual wavy boundary. E2--67 to 167 cm; yellow (10YR 7/8) sand; sing le grained; loose; few fine and medium roots; many uncoated sand grains; str ongly acid; clear wavy boundary. (Combined thickness of the E horizons range from 95 to 187 cm) E&Bt1--167 to 237 cm; very pale brown ( 10YR 7/4) sand (E); fe w fine and medium distinct very pale br own (10YR 8/2) splotches; single gr ained; loose; fe w fine roots; many uncoated sand grains; few distinct yellowish brown (10YR 5/8) loamy sand lamellae (Bt) 1 to 3 mm thick and 1 to 8 cm long; slight increase in abundance with depth; sand grains in lamellae are well coat ed; strongly acid; gra dual wavy boundary. (22 to 38 inches thick) E&Bt2--237 to 272 cm; very pale brown ( 10YR 7/4) sand (E); fe w fine and medium distinct very pale br own (10YR 8/2) splotches; single gr ained; loose; many sand grains are uncoated; yellowish brown (l0YR 5/8) loamy sand lamellae (Bt) about 1 to 8 cm long and 3 to 8 mm thick, increasing in abundance wi th depth; sand grains in lamellae are well coated; very strongly aci d; gradual wavy boundary. Bt--272to 287 cm; brownish yellow (10YR 6/ 6) sandy loam; moderate medium granular structure; friable; sa nd grains well coated; very strongly acid. DIAGNOSTIC HORIZONS: Ochric epipedon Adapted from Doolittle, JA, Schellentrager, G. 1989. Soil Survey of Orange County, Florida. United States Department of Agri culture, Soil Conservation Service. p. 85. Revised July, 2003
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135 Table A-4. Soil description of Candler series at the Oakland Cemetery natural soils (OCNS), Orange County, Florida. SOIL SERIES: Candler CLASSIFICATION: Hyperthermic unc oated Lamellic Quartzipsamments GENERAL LOCATION: State Road 50 and Florida Turnpike (OR9567) SOIL DESCRIBED BY: Christophe r Chilton (Bucket auger) Date: May 3, 2006 Ap to 10 cm; dark grayish brown (10YR 4/2) fi ne sand; single grained; loose; few fine and medium roots; many uncoated sand grains; clear boundary. C1 to 65 cm; light yellowish brown (10YR 6/4) fine sand; single graine d; loose few fine and medium roots; many uncoated sand grains; clear boundary. C2 to 135 cm; brownish yellow (10YR 6/6) fi ne sand; single grained; loose; few fine and medium roots; few uncoated sand grains; gradual boundary. C3 to 180 cm; brownish yellow (10YR 6/8) fi ne sand; (C) strong brown (7.5YR 5/6) thin loamy sand lamellae; (Bt); single grained; loose; few fine roots; many coated grains; strongly acid. DIAGNOSTIC HORIZONS: Ochric epipedon
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136 Table A-5. Official descri ption of Orlando soil series in Lake County, Florida. TAXONOMIC CLASS: Siliceous, hypertherm ic Humic Psammentic Dystrudepts. A1 to 20 cm; black (10YR 2/1) rubbed, fine sa nd; weak fine crumb structure; friable; many fine medium coarse roots; organic matter mixed with uncoa ted sand grains; strongly acid; gradual wavy boundary. A2 to 50 cm; very dark gray (10YR 3/1) r ubbed, fine sand, weak fine crumb structure; friable; many fine and medium roots; few narrow streaks of light gray along root channels, few small pockets of light gray sand; strongly acid; gradual wavy boundary (Combined thickness of the A horizon is 10 to 24 inches). A/C to 80 cm; dark grayish brown (10YR 4/2) rubbed fine sand, mixed dark gray (10 YR 4/1), very pale brown (10YR 7/3), and gray (10Y R 6/1); single grained; lo ose; few fine roots; strongly acid; gradual wavy boundary. (0 to 35 cm thick) C1 to 155 cm; yellowish brown (10YR 5/4), fine sand; single grained; loose; few fine roots in upper part; about 5 percent of sand grains are coated; strong ly acid; gradual wavy boundary. (25 to 65 cm thick) C2 to 220 cm; pale brown (10YR 6/3), fine sa nd, few fine faint brownish yellow and light gray mottles, few fine distinct strong brown (7.5 YR 5/8) mottles; single grained; loose; common uncoated sand grains; strongly acid. DIAGNOSTIC HORIZONS: Umbric epipedon Adapted from Furman A.L., White H.O., Cruz O.E., Russell W.E., and Thomas B.P. Soil Survey of Lake County, Florida. Unite d States Department of Agriculture, Soil Conservation Service. p. 126. Revised May, 2005.
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137 Table A-6. Soil description of Orlando series at the prehistori c archaeological natural soils (PANS). SOIL SERIES: Orlando CLASSIFICATION: Siliceous, hyperthermic Humic Psammentic Dystrudepts. GENERAL LOCATION: (8LA243) Southwest shore of Lake Apopka, Montverde, Florida SOIL DESCRIBED BY: Christophe r Chilton (Bucket auger) Date: March 2, 2005 Ap to 27 cm; very dark brown (10YR 2/2) fine sand; weak fine granular structure; friable; many fine and medium roots; gradual boundary. A to 90 cm; dark brown (7.5YR 3/2) fine sa nd; single grain; loose; many fine and medium roots; gradual boundary. A/C to108 cm; dark brown (7.5 3/4) fine sand; single grain; loose; few fine and medium roots; gradual boundary. C to195 cm; strong brown (7.5YR 4/6) fine sand; single grain; l oose; abrupt boundary. DIAGNOSTIC HORIZONS: Umbric epipedon
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138 Table A-7. Official description of Immokal ee soil series in St. Johns County, Florida. TAXONOMIC CLASS: Sandy, siliceous , hyperthermic Arenic Alaquods A to 15 cm; very dark gray (10YR 3/1) fine sand; weak fine granular st ructure; very friable; many fine and medium roots; many uncoated white grain sands; extremely acid; gradual smooth boundary. E1 to 30 cm; light gray (10YR 6/1) fine sand; common fine faint gray mottles; single grained; loose; few fine distinct dark gray (10YR 4/1) stains along root channels ; few fine and medium roots; very strongly acid; gradual smooth boundary. E2 to 87 cm; white (10YR 8/1) fine sand; co mmon medium and coarse distinct dark gray (10YR 4/1), dark grayish brow n (10YR 4/2), and dark brown (10YR 3/3) stai ns along root channels; single grained; loose; very strongly acid; abrupt irregular boundary. Bh1to 107 cm; black (10YR 2/1) fine sand; lowe r 5 cm grades to dark reddish brown (5YR 2/2); weak fine granular struct ure; friable common fine and me dium roots; very strongly acid; clear wavy boundary. Bh2 to 135 cm; dark reddish brown (5YR 3/3) fine sand; single graine d; loose; few fine and medium roots; common fine and medium dark reddish brown (5YR 2/ 2); few fine distinct gray (10YR 5/1) sand lenses and pockets; very strongly acid; gradual wavy boundary (Combined thickness of the Bh horizon ranges from 25 to 125 cm). BC to 180 cm; dark brown (10YR 4/3) fine sand; few fine faint dark brown, pale brown, and light gray mottles; single grained; loose; strongly acid. DIAGNOSTIC HORIZONS: Ochric epipedon, albic and spod ic subsurface horizons, Adapted from Readle E.L. Soil Survey of St. Johns County, Florida. United States Department of Agriculture, Soil Conservation Serv ice. p. 85. Revised July, 1993.
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139 Table A-8. Soil description of I mmokalee series at the historic archaeological natural soils (HANS). SOIL SERIES: Immokalee CLASSIFICATION: Sandy, siliceous , hyperthermic Arenic Alaquods. GENERAL LOCATION: (8SJ3149) East of highway U.S.1. and west of the Tolomato River, north of St. Augustine, Florida. SOIL DESCRIBED BY: Christopher Chilton and Mary Collins (Profile) Date: Sept 20, 2005 Ap to 3 cm; very dark gray (10YR 3/1) fine sand; weak fine granular structure; many fine and medium roots; many uncoated white grain sands; gradual smooth boundary. E1 to 16 inches; light gray (10YR 6/1) fine sa nd; single grained; loos e; few fine and medium roots; gradual smooth boundary. E2 to 46 cm; light gray (10YR 7/1) fine sand ; single grained; loose; few fine and medium roots; gradual smooth boundary. E3 to 74 cm; white (10YR 8/1) fine sand; singl e grained; loose; few fi ne and medium roots; clear smooth boundary. Bh to 119 cm; very dark gray (10YR 3/1) fine sand; moderate medium subangular blocky structure; noncemented; fr iable; clear smooth boundary.
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140 APPENDIX B PARTICLE-SIZE ANALYSIS Table B-1. Soil data from the Newberry Ce metery Anthropogenic Soils (NCAS) and the Newberry Cemetery Natural Soils (NCNS) . Sand fractions are displayed as very coarse (VC, 2-1 mm), coarse (C, 1-500 m), medium (500-250 m), fine (F, 250-106 m), and very fine (VF, 106-45 m). ID is the sample number. NCAS ID Depth Horizon VC %C % M %F % VF % Sand % Silt % Clay % 73 0-15 A 0 2 17 43 25 88 10 3 74 45-60 E 0 1 12 47 32 93 1 6 75 85-100 E 0 2 15 47 29 94 4 2 76 112-127 E 0 2 14 45 32 92 4 4 77 144-159 Bt 0 1 13 50 31 72 6 22 86 0-15 A 0 2 17 49 25 93 5 3 87 45-60 E 0 2 16 49 26 94 4 2 88 85-100 E 0 1 13 50 31 94 4 1 89 120-131 E 0 2 15 49 29 95 4 1 90 145-159 Bt 0 1 12 47 32 71 5 24 103 0-15 A 0 2 14 44 28 87 6 7 104 48-62 E 1 3 15 42 26 87 7 6 105 87-102 E 1 3 15 44 27 89 6 5 NCNS ID Depth Horizon VC %C % M %F % VF % Sand % Silt % Clay % 73 0-15 A 0 2 17 43 25 88 10 3 74 45-60 E 0 1 12 47 32 93 1 6 75 85-100 E 0 2 15 47 29 94 4 2 76 112-127 E 0 2 14 45 32 92 4 4 77 144-159 Bt 0 1 13 50 31 72 6 22 86 0-15 A 0 2 17 49 25 93 5 3 87 45-60 E 0 2 16 49 26 94 4 2 88 85-100 E 0 1 13 50 31 94 4 1 89 120-131 E 0 2 15 49 29 95 4 1 90 145-159 Bt 0 1 12 47 32 71 5 24
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141 Table B-2. Soil data from the Oakland Ceme tery Anthropogenic Soils (OCAS) and the Oakland Cemetery Natural Soils (OCNS). OCAS ID Depth Horizon VC %C % M %F % VF % Sand % Silt % Clay % 114 0-15 A 0 2 27 58 11 97 2 1 115 35-50 C1 0 1 24 61 11 97 2 1 116 85-100 C2 0 1 25 59 12 97 2 1 117 135-150 C3 0 1 25 61 11 98 2 0 130 0-15 A 0 2 31 56 8 96 0 3 131 35-50 C1 0 1 25 25 11 63 36 1 132 85-100 C2 0 1 24 60 12 97 2 1 133 135-150 C3 0 1 26 60 10 97 2 0 154 0-15 A 0 2 41 47 7 98 1 1 155 35-50 C1 0 3 46 43 5 98 1 1 156 85-100 C2 0 2 40 48 7 98 0 2 157 135-150 C3 0 3 42 46 7 98 1 2 OCNS ID Depth Horizon VC %C % M %F % VF % Sand % Silt % Clay % 122 0-15 A 0 1 23 59 13 97 3 0 123 35-50 C1 0 1 27 59 10 97 2 1 124 85-100 C2 0 1 22 61 13 97 2 1 125 135-150 C3 0 1 26 61 10 98 2 0 146 0-15 A 0 2 30 58 8 98 1 1 147 35-50 C1 0 2 31 56 9 98 1 1 148 85-100 C2 0 2 31 57 8 98 2 0 149 135-150 C3 0 2 32 56 8 98 2 1
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142 Table B-3. Soil data from the Prehistoric Archaeological Anthropogenic Soils (PAAS) and the Prehistoric Archaeological Natural Soils (PANS). PAAS Sample Depth Horizon VC %C %M %F % VF % Sand % Silt % Clay % 162 0-15 Ap 0 7 47 39 1 94 1 6 163 30-45 A11 0 8 48 36 1 93 1 6 164 60-75 A12 1 7 47 37 1 93 1 6 165 90-105 A/C 1 8 49 35 1 93 0 6 166 120-135 C11 0 5 42 44 2 93 0 6 167 150-165 C12 0 7 46 39 1 94 0 7 168 180-195 C13 0 7 49 36 1 94 0 6 192 0-15 Ap 0 7 49 38 1 94 0 6 193 30-45 A 0 7 45 39 1 93 1 6 194 60-75 A 1 9 51 32 1 93 1 6 195 90-105 A/C 0 9 50 35 1 94 0 6 196 120-135 C11 0 9 50 34 1 94 0 6 197 150-165 C12 0 8 49 36 1 94 0 6 198 180-195 C13 0 7 46 39 1 94 0 6 PANS Sample Depth Horizon VC %C %M %F % VF % Sand % Silt % Clay % 226 0-15 Ap 0 5 46 42 1 94 0 6 227 30-45 A 0 7 50 36 1 94 0 6 228 60-75 A 0 8 48 38 1 95 1 5 229 90-105 A/C 0 8 49 37 1 95 0 5 230 120-135 C11 0 8 46 39 1 93 1 6 231 150-165 C12 0 8 47 37 1 95 1 5 232 180-195 C13 0 8 45 40 2 95 0 5
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143 Table B-4. Soil data from the Historic Ar chaeological Anthropogeni c Soils (HAAS) and the Historic Archaeological Natural Soils (HANS). HAAS Sample Depth Horizon VC % C % M % F % VF % Sand % Silt % Clay % 3 0-5 A 0 0 3 85 5 94 5 1 12 20-25 E1 0 0 3 89 6 97 1 2 21 40-45 E2 0 0 3 87 6 95 2 3 4 0-5 A 0 0 3 87 6 96 3 1 13 20-25 E1 0 0 3 87 6 96 3 1 20 40-45 E2 0 0 2 88 6 96 3 2 9 0-5 A 0 0 3 87 6 96 3 1 18 20-25 E1 0 0 2 87 6 95 3 1 19 40-45 E2 0 0 3 88 6 97 2 1 1 0-5 A 0 0 3 86 6 96 3 1 10 20-25 E1 0 0 2 89 6 97 2 1 27 40-45 E2 0 0 3 87 5 95 2 3 5 0-5 A 0 0 3 87 6 96 4 1 14 20-25 E1 0 0 2 89 6 97 2 1 23 40-45 E2 0 0 2 89 6 97 1 1 7 0-5 A 0 0 3 87 6 96 3 1 16 20-25 E1 0 0 3 89 6 97 1 1 25 40-45 E2 0 0 3 89 6 98 1 1 28 0-5 A 0 4 31 48 13 97 2 1 34 20-25 E1 0 0 3 89 6 97 1 1 42 40-45 E2 0 0 3 87 6 97 0 3 HANS Sample Depth Horizon VC % C % M % F % VF % Sand % Silt % Clay % 31 0-6 A 0 0 2 88 6 96 2 2 36 6 18 E1 0 0 3 89 6 97 1 1 41 18-44 E2 0 0 3 89 5 98 2 1 43 44-70 E3 0 0 3 89 6 98 1 1 32 0-5 A 0 0 3 88 6 97 2 1 39 20-25 E2 0 0 3 90 5 98 2 1 40 40-45 E2 0 0 3 90 6 99 1 0 46 0-3 A 0 0 3 88 5 97 2 1 47 3 16 E1 0 0 3 90 5 98 1 1 48 16-46 E2 0 0 4 90 5 98 1 1 49 46-74 E3 0 0 3 90 5 99 1 1 50 74-93 Bh 0 0 4 86 5 95 2 3
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144 APPENDIX C SOIL CHEMICAL ANALYSES Table C-1. Soil data for the Newberry Cemete ry Anthropogenic Soils (NCAS) from selected transects. Extractable (Ext.) . NCAS Transect 22 15N/21E ID Depth (cm) Horizon pH Ext. P Ext. Ca. Ext. Mg Org. C EC mg/kg mg/kg mg/kg % ds/m-1 103 0-15 Ap 6.4 57 54 51.4 4.0 0.5 104 45-60 E1 8.3 26 2486 31.7 3.2 0.4 105 85-100 E2 8.7 87 2744 29.6 0.4 0.2 106 112-127 E2 8.7 12 548 12.4 0.1 0.3 107 147-159 Bt 6.7 17 684 17.3 0.4 0.7 Table C-2. Soil data for the Newberry Cemete ry Anthropogenic Soils (NCAS) from selected transects. Extractable (Ext.) . NCAS Transect 14 5N/13E ID Depth (cm) Horizon pH Ext. P Ext. Ca. Ext. Mg Org. C EC mg/kg mg/kg mg/kg % ds/m-1 69 0-15 Ap 5.6 6.66 149.81 26.83 1.73 0.1 70 45-60 E1 6.1 17.98 142.63 11.88 0.64 0.04 71 85-100 E2 7.6 18.2 260.19 7.75 0.71 0.34 72 104-118 E2/Bt 8.2 50.16 2201.35 21.22 1.22 0.44 Table C-3. Soil data for the Newberry Cemete ry Anthropogenic Soils (NCAS) from selected transects. Extractable (Ext.) . NCAS Transect 10 8N/9E ID Depth (cm) Horizon pH Ext. P Ext. Ca. Ext. Mg Org. C EC mg/kg mg/kg mg/kg % ds/m-1 66 0-15 Ap 7.3 19.2 380.12 21.24 1.67 0.32 67 40-55 E1 8.4 90.52 2697 29.92 0.51 0.32 68 85-100 E2 8.5 67.04 2563.91 23.34 0.13 0.26
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145 Table C-4. Soil data for the Newberry Cemete ry Anthropogenic Soils (NCAS) from selected transects. Extractable (Ext.) . NCAS Transect 14 9N/13E ID Depth (cm) Horizon pH Ext. P Ext. Ca. Ext. Mg Org. C EC mg/kg mg/kg mg/kg % ds/m-1 73 0-15 A 6.6 28.48 372.36 51.83 4.04 0.36 74 45-60 E 6.1 35.48 77.56 7.29 0.38 0.04 75 85-100 E 7.2 12.66 70.9 2.55 0.13 0.1 76 112-127 E 7.1 8.44 115.93 3.45 0.86 0.08 77 144-159 Bt 6.2 38.24 1187.53 23.14 1.17 0.43 Table C-5. Soil data for the Oakland Cemete ry Anthropogenic Soils (OCAS) from selected transects. Extractable (Ext.) . OCAS Transect 9 40N/10E ID Depth Horizon pH Ext. P Ext. Ca. Ext. Mg Org. C EC mg/kg mg/kg mg/kg % ds/m-1 130 0-15 Ap 5.9 56.72 268.34 54.74 2.35 0.18 131 35-50 C1 6.6 52.56 85.25 21.22 0.42 0.08 132 85-100 C2 6.6 18.98 29.57 10.73 0.16 0.04 133 135-150 C3 6.6 5.93 15.56 6.15 0.03 0.02 Table C-6. Soil data for the Oakland Cemete ry Anthropogenic Soils (OCAS) from selected transects. Extractable (Ext.) . OCAS Transect 22 40N/54W ID Depth Horizon pH Ext. P Ext. Ca. Ext. Mg Org. C EC mg/kg mg/kg mg/kg % ds/m-1 146 0-15 A 4.9 4.32 73.14 73.14 1.58 0.14 147 35-50 C1 5.2 6.3 46.82 46.82 1.19 0.1 148 85-100 C2 5 12.4 6.09 6.09 0.55 0.04 149 135-150 C3 5.3 8.06 17.16 17.16 0.68 0.06
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146 Table C-7. Soil data for the Oakland Cemete ry Anthropogenic Soils (OCAS) from selected transects. Extractable (Ext.) . OCAS Transect 22 14N/52W ID Depth Horizon pH Ext. P Ext. Ca. Ext. Mg Org. C EC mg/kg mg/kg mg/kg % ds/m-1 154 0-15 Ap 4.9 3.2 44.6 10.7 1.6 0.2 155 35-50 C1 5.2 3.4 29.0 7.5 0.8 0.1 156 85-100 C2 5.2 3.9 18.6 5.0 0.6 0.0 157 135-150 C3 5.2 7.1 5.1 1.8 0.2 0.0 Table C-8. Soil data for the Prehistoric Archaeological Anthropoge nic Soils (PAAS) from selected transects. Extractable (Ext.). PAAS Transect 2 2N/1E ID Depth Horizon pH Ext. P Ext. Ca Ext. Mg Org. C EC (cm) mg/kg mg/kg mg/kg % ds/m-1 162 0-15 Ap 5.4 1192 1336 60.7 1.8 0.2 163 30-45 A11 6 1320 2661 90.1 1.6 0.2 164 60-75 A12 6.3 1014 936 61.9 1.1 0.2 165 90-105 A/C 6.6 611 600 41.6 0.4 0.1 166 120-135 C11 6.6 251 506 36.1 0.5 0.1 167 150-165 C12 6.5 236 31 24.4 0.8 0.1 168 180-195 C13 6.6 193 179 24.9 0.1 0.1 Table C-9. Soil data for the Historic Archaeolo gical Anthropogenic Soil s (HAAS) from selected transects. Extractable (Ext.). HAAS Test Unit 17 , Transect 1 52N/44E ID Depth Horizon pH Ext. P Ext. Ca. Ext. Mg Org. C EC (cm) mg/kg mg/kg mg/kg % ds/m-1 3 0-5 Ap 6 170.0 1449.6 142.4 4.5 0.8 12 20-25 E1 6.6 22.2 291.2 29.2 1.1 0.1 21 40-45 E2 6 55.1 54.3 8.1 0.4 0.1 Table C-10. Soil data for the Historic Ar chaeological Anthropogenic Soils (HAAS) from selected transects. Extractable (Ext.) . HAAS Test Unit 17, Transect 1 50N/44E ID Depth Horizon pH Ext. P Ext. Ca. Ext. Mg Org. C EC (cm) mg/kg mg/kg mg/kg % ds/m-1 9 0-5 Ap 6.2 52.1 656.7 103.8 3.8 0.6 18 20-25 E1 8 332.4 257.8 29.1 1.4 0.4 19 40-45 E2 7.8 84.4 281.9 5.7 0.6 0.2
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147 Table C-11. Soil data for the Historic Ar chaeological Anthropogenic Soils (HAAS) from selected transects. Extractable (Ext.) . HAAS Test Unit 17, Transect 3 52N/46E ID Depth Horizon pH Ext. P Ext. Ca. Ext. Mg Org. C EC (cm) mg/kg mg/kg mg/kg % ds/m-1 1 0-5 Ap 6.3 56.84 622.84 120.17 4.68 1.4 10 20-25 E1 6.6 69.84 299.76 23.95 0.9 0.16 27 40-45 E2 6.5 55.84 102.68 10.03 0.45 0.08 Table C-12. Soil data for the Historic Ar chaeological Anthropogenic Soils (HAAS) from selected transects. Extractable (Ext.) . HAAS Test Unit 17, Transect 3 51N/46E ID Depth Horizon pH Ext. P Ext. Ca. Ext. Mg Org. C EC (cm) mg/kg mg/kg mg/kg % ds/m-1 5 0-5 Ap 6.2 42.12 608.87 141.09 4.43 1.08 14 20-25 E1 7.2 149.3 527.59 32.73 1.15 0.28 23 40-45 E2 7.1 41.84 278.51 8.02 1.09 0.12 Table C-13. Soil data for the Historic Ar chaeological Anthropogenic Soils (HAAS) from selected transects. Extractable (Ext.) . HAAS Test Unit 17, Transect 3 50N/46E ID Depth (cm) Horizon pH Ext. P Ext. Ca. Ext. Mg Org. C EC mg/kg mg/kg mg/kg % ds/m-1 7 0-5 Ap 6.1 45.36 488.15 112.79 3.85 0.8 16 20-25 E1 6.3 36.2 235.31 13.75 0.9 0.12 25 40-45 E2 6.7 15.14 54.34 3.1 0.26 0.04 Table C-14. Soil data for the Historic Ar chaeological Anthropogenic Soils (HAAS) from selected transects. Extractable (Ext.) . HAAS Test Unit 18, Transect 8 50N/40E ID Depth Horizon pH Ext. P Ext. Ca. Ext. Mg Org. C EC (cm) mg/kg mg/kg mg/kg % ds/m-1 28 0-5 Ap 6.3 46.2 246.04 22.67 1.35 0.54 34 20-25 E1 6.5 23.6 273.92 21.64 1.09 0.18 42 40-45 E2 6.6 51.12 224.96 15.83 0.83 0.12 Table C-15. Soil data for the Historic Ar chaeological Anthropogenic Soils (HAAS) from selected transects. Extractable (Ext.) . HAAS Test Unit 18, Transect 8 52N/40E ID Depth Horizon pH Ext. P Ext. Ca. Ext. Mg Org. C EC (cm) mg/kg mg/kg mg/kg % ds/m-1 32 0-5 Ap 6.2 23.6 369.54 54.86 3.02 0.74 39 20-25 E1 6.4 41.28 238.99 13.84 1.15 0.2 40 40-45 E2 6.8 2.4 32.39 2.27 0.06 0.02
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148 Table C-16. Soil data for the Historic Arch aeological Natural Soils (HANS) from selected transects. Extracta ble (Ext.). HANS, Transect 12 48N/30E ID Depth Horizon pH Ext. P Ext. Ca. Ext. Mg Org. C EC (cm) mg/kg mg/kg mg/kg % ds/m-1 31 0-6 A 5.4 17.74 26.07 67.43 2.89 0.6 36 15-25 E1 4.9 1.62 11.38 5.49 1.03 0.04 41 29-44 E2 4.8 1.89 4.43 3.65 0.26 0.06 43 55-70 E3 5.1 2.1 2.79 1.89 0.26 0.02 Table C-17. Soil data for the Historic Arch aeological Natural Soils (HANS) from selected transects. Extracta ble (Ext.). HANS, Transect 14 40N/20E ID Depth Horizon pH Ext. P Ext. Ca. Ext. Mg Org. C EC (cm) mg/kg mg/kg mg/kg % ds/m-1 46 0-5 A 5.4 14.36 7.42 47.67 5.07 0.42 47 10-25 E1 4.7 1.1 5.19 3.45 0.32 0.02 48 31-46 E2 4.9 1.27 3.22 2.15 0.26 0.04 49 59-74 E3 5.3 1.03 3.57 1.46 0.26 0.02 50 78-93 Bh 5.1 27.8 23.44 8.76 1.8 0.06
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149 GRAVE PEDOGENIC PEDOGENIC GRAVE APPENDIX D GPR PROFILES Figure D-1. Ground-penetrating radar (GPR) transect 22 of the Newberry Cemetery Anthropogenic Soils (NCAS) using 500-MH z antenna. Grave shaft is present between 9-11 meter mark. Note between the 3-5 meter undulating subsurface resembles suspect anomaly for potential gr ave. No sampled physical evidence the anomaly is a grave. Figure D-2. Ground-penetrating radar (GPR) transect 22 of the Newberry Cemetery Anthropogenic Soils (NCAS) using 500-MH z antenna. Background filter and energy decay postprocessing is applied. Reflections are exaggerated and suspect anomaly at the 3-5 meter mark is highlighted. Grave sh aft illustrates scattering and attenuation of radar.
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150 Anomaly from auger Suspect grave Suspect grave Anomaly from auger Suspect grave Anomaly from auger Figure D-3. Ground-penetrating ra dar (GPR) transect 4 of the Oakland Cemetery anthropogenic Soils (OCAS) using 500-MHz antenna. Su spect grave is less than 50 cm from surface.Radar reflections at the 13.5 meter mark is from an auger Figure D-4. Ground-penetrating ra dar (GPR) transect 4 of the Oakland Cemetery Anthropogenic Soils (OCAS) using 500-MHz antenna. Sp ectral whitening is applied to profile. Suspect grave is less than 50 cm from surf ace. Radar reflections at the 13.5 meter mark is from an auger Figure D-5. Ground-penetrating ra dar (GPR) transect 4 of the Oakland Cemetery Anthropogenic Soils (OCAS) using 500-MHz antenna. Background filter with Gray 1 color scale Potential grave is less than 50 cm from su rface. Radar reflections at the 13.5 meter mark is from an auger.
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151 C horizon C horizon A horizon A horizon C horizon A horizon Figure D-6. Ground-penetrating ra dar (GPR) transect 2 of th e Prehistoric Archaeological Anthropogenic Soils (PAAS) using 500-MH z antenna.. The interface of the A horizon and C horizon is evident at a depth of 70 to 80 cm (dashed line). Figure D-7. Ground-pene trating radar (GPR) tr ansect 2 of the Preh istoric Archaeological Anthropogenic Soils (PAAS) using 500-MHz antenna. Background filter is applied with spectral whitening to enhance the C horizon. The interface of the A horizon and C horizon is evident at a depth of 70 to 80 cm (dashed line). Figure D-8. Ground-penetra ting radar (GPR) transect 2 of the Prehistoric ArchaeologicalAnthropogenic Soils (P AAS) using 500-MHz antenna. Background filter is applied with spectral whitening to enhance the C horizon.
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152 Figure D-9. Ground-penetr ating radar (GPR ) transect 3 of the Historic ArchaeologicalAnthropogenic Soils (HAAS) using 500-MHz antenna. Structure floor is evident at a depth of 40-50 cm. Figure D-10. Ground-penetrating radar (GPR) transect 3 of the Historic Archaeological Anthropogenic Soils (HAAS) using 500-MHz antenna. Background filter is applied. Spectral whitening allows bac kground clutter to decrease. St ructure floor is evident at a depth of 40-50 cm. Figure D-11 Ground-penetrating radar (GPR) transect 3 of the Historic Archaeological Anthropogenic Soils (HAAS) using 500-MHz antenna. Background filter is applied. Spectral whitening allows bac kground clutter to decrease. Structure floor is evident at a depth of 40-50 cm. Gray 1 scale is applied. Structure Floor Structure Floor Structure Floor
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153 APPENDIX E STATISTICS Table E-1 Results of t-tests for Newberry Cemetery natural soils (NCNS) and Newberry Cemetery anthropogenic soil (NCAS) samples using data derived from Table 4-1 and C-1 Phosphorus (mg/kg) NCNS NCAS Mean 20.5 68.4 Standard Deviation 13.4 49.9 Observations 20 20 Df 19 t Stat P(T<=t) two tail -3.04 0.010191 Calcium (mg/kg) NCNS NCAS Mean 330 1811 Standard Deviation 470 1063 Observations 20 20 Df 19 t Stat P(T<=t) two tail -3.92 0.001539 Magnesium (mg/kg) NCNS NCAS Mean 14.6 30.1 Standard Deviation 16.4 13.8 Observations 20 20 Df 19 t Stat P(T<=t) two tail -2.53 0.098741
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154 Table E-2. Results of t-tests for Oakland Cemete ry natural soils (OCNS) and Oakland Cemetery anthropogenic (OCAS) soil samples using da ta derived from Table 4-2 and C-2. Phosphorus (mg/kg) OCNS OCAS Mean 8.26 34.4 Standard Deviation 3.23 27.8 Observations 18 18 Df 17 t Stat P(T<=t) two tail -2.62 0.1853 Calcium (mg/kg) OCNS OCAS Mean 41.1 89.4 Standard Deviation 23.1 89.2 Observations 18 18 Df 17 t Stat P(T<=t) two tail -1.89 0.2329 Magnesium (mg/kg) OCNS OCAS Mean 12.1 19.9 Standard Deviation 7.18 15.8 Observations 18 18 Df 17 t Stat P(T<=t) two tail -1.69 0.1625
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155 Table E-3. Results of t-tests for Prehistoric archaeological natural soils (PANS) and Prehistoric archaeological anthropogenic soils (PAAS) samples using da ta derived from Table 43 and C-3. Phosphorus (mg/kg) PANS PAAS Mean 224.73 994 Standard Deviation 104.2 542 Observations 17 17 Df 16 t Stat P(T<=t) two tail -4.71 0.005987 Calcium (mg/kg) PANS PAAS Mean 166.28 1080.36 Standard Deviation 131.15 868.65 Observations 17 17 Df 16 t Stat P(T<=t) two tail -1.72 0.01706 Magnesium (mg/kg) PANS PAAS Mean 18.93 50.4 Standard Deviation 10.12 25.0 Observations 17 17 Df 16 t Stat P(T<=t) two tail -0.541 0.1096
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156 Table E-4. Results of t-tests for Historic archaeological soils (HANS) and Historic archaeological anthropogenic soil (HAAS) samples using data derived from Table 4-4 and C-4. Phosphorus (mg/kg) HANS HAAS Mean 9.65 85.61 Standard Deviation 11.94 40.38 Observations 18 18 Df 17 t Stat P(T<=t) two tail -2.97 0.09344 Calcium (mg/kg) HANS HAAS Mean 11.07 306.1 Standard Deviation 8.78 134.16 Observations 18 18 Df 17 t Stat P(T<=t) two tail -2.87 0.06014 Magnesium (mg/kg) HANS HAAS Mean 15.06 46.08 Standard Deviation 23.9 50.61 Observations 18 18 Df 17 t Stat P(T<=t) two tail -1.71 0.09344
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157 LIST OF REFERENCES Annan, A.P. and S.W. Cosway. 1994. GPR frequency selection. In Proceedings of the Fifth International Conference on Ground-Penetra ting Radar: 747-760. Waterloo Centre for Groundwater Research, Waterloo, Canada. Annan, A.P. 2002. GPR-history, trends, a nd future developments. Subsurface Sensing Technologies and Applica tions, Vol. 3, 4:253-270. Annan, A.P., W.M. Waller, D.W. Strangway, J.R. Rossiter, J.D. Redman, and R.D. Watts. 1975. The electromagnetic response of a low-loss, 2-la yer, dielectric earth for horizontal electric dipole excitation. Geophysics 40, 2: 285-298. Batey, R.A. 1987. Subsurface interface radar at Sepphoris, Israel, 1985. Journal of Field Archaeology 14, 1:1-8. Bevan, B.W. 1991. The search for graves. Geophysics 56:1310-1319. Birkeland, P.W. 1999. Soils and Geomorphology. 3rd Edition. Oxford University Press, New York Bohn, H.L., B.L. McNeal, and G.A. O’Conner. 1985. Soil Chemistry. John Wiley and Sons, New York. Bond, S., S. Parker, and S. Smith. 1990. The Saba te plantation: The history and archaeology of a Minorcan farmstead. Historic St. Augustin e Preservation Board, St. Augustine. Brown, J.A. 1981. The search fo r rank in prehistoric burials. In The Archaeology of Death, ed. R. Chapman, I. Kinnes, K. Randsborg, p. 2537. Cambridge University Press, Cambridge. Chadwick, W.J. and J.A. Madsen. 2000. The applic ation of ground-penetrati ng radar to a coastal prehistoric archaeological site , Cape Henlopen, Delaware, U.S.A. Geoarchaeology, 15, 8:765-781. Collins, M.E. 1990. Applicati on of ground-penetrating radar. In XVII Reunion Nacional sobre Edafologia: 15-32. Badajoz, Spain. Collins, M.E. 1992. Soil taxonomy: A useful guide for the application of ground-penetrating radar. In Proceedings of the Fourth Internationa l Conference on Ground-Penetrating Radar, p.125-132. Rovaniemi, Finland. Collins, M.E. 1997. Key to soil orders in Florida. Document SL-43, Soil and Water Sciences Department, Institute of Food and Agricultu ral Services, University of Florida, Gainesville.
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158 Collins, M.E., F.A. Ovalles, R.J. Kuehl, J.L. Kurtz, B.K. Miller, and P. Kostaanch. 1996. Characterization and comparison of soils fo r ground penetrating radar measurements. University of Florida report to MIT/Li ncoln Laboratory and the Army Research Laboratory. Collins, M.E. and G. Shapiro. 1987. Comparisons of human-influenced and natural soils at the San Luis Archaeological Site, Florida. Soil Science Society of America Journal 51:171176. Conyers, L.B. 2004. Ground-Penetrating Radar for Ar chaeology. Altamira Press, Walnut Creek, California. Conyers, L.B. 1995. The use of Ground Penetrat ing Radar to map the buried structures and landscape of the Ceren site, El Salvador. Geoarchaeology 10:275-299. Conyers, L.B. and C.M. Cameron. 1998. Finding bur ied archaeological featur es in the American Southwest: New ground-penetrating radar tech niques and three-dimensional computer mapping. Journal of Field Archaeology 25, 4:417-430. Conyers, L.B., and D. Goodman. 1997. GroundPenetrating Radar: An Introduction for Archaeologists. Altamira Press, Walnut Creek, California. Cook, J.C. 1960. Proposed monocycle-pulse , VHF radar for airborne ice and snow measurements. AIE Transmission Communi cation and Electronics 79, 2:588-594. Cook, J.C. 1975. Radar transparencies of mine and tunnel rocks. Geophysics 40:865-885. Dalan, R.A. and B.W. Bevan. 2002. Geophysical indicators of culturally emplaced soils and sediments. Geoarchaeology 17, 8:779-810. Daniels, D.J. 1996. Surface-Penetrating Radar. The Institute of Electrical Engineers, London, United Kingdom. Daniels, D.J. 2004. Ground Penetrating Radar, 2nd Edition. The Institute of Electrical Engineers, London, United Kingdom. Davis, J.L., and A.P. Annan. 1989. Ground-penetr ating radar for high-reso lution mapping of soil rock and stratigraphy. Geophysics 37:531-551. Davis, J.L., J.A. Higgenbottom, A.P. Annan, a nd K.E. Duncan. 1998. Plan view presentation of gpr data. In Seventh Internationa l Conference on Ground Penetrating Radar: 39-45. Lawerence, Kansas. Davis, R.A. 1997. Geology of the Florida coast. In The Geology of Florida. ed. A.F. Randazzo and D.S. Jones. University of Flor ida Press, Gainesville, Florida. Day, P.R. 1965. Particle fractionation and particle-size analysis. Agronomy 9:545-567.
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163 Whittaker, W.E. and G.R. Storey. 2005. Ground-pene trating radar survey of the possible mounds 13AM446 Mound, Effigy Mounds National Monu ment, Allamakee County, Iowa. The University of Iowa, Office of the St ate Archaeologist, Iowa City, Iowa.
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164 BIOGRAPHICAL SKETCH Christopher P. Chilton was born and raised in Ho-Ho-Kus, New Jersey. He attended excellent schools and followed many career path s until he settled in Florida. There, the archaeology bug caught him in 1998 and he worked contract archaeology for several years. He returned to school and received a B.S. in anthr opology from the University of Florida in 2004. Before graduation, Christopher was exposed to the world of soils a nd returned to the University of Florida to begin a Master of Scienc e degree. With an emphasis on pedology and anthropogenic impact, Christopher was exposed to the world of ground-penetrating radar and thus was the inception for his thesis.
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