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 Front Cover
 Copyright
 Florida State Board of Conserv...
 Transmittal letter
 Table of contents
 Abstract
 Introduction
 Geography
 Geology
 Summary and conclusions
 References
 Table 6. Measurements of water...
 Table 7. Logs of selected...


FGS





:i STATE OF FLORIDA
STATE BOARD OF CONSERVATION
Ernest MittsiDirector


FLORIDA GEOLOGICAL SURVEY
Robert O. Vernon, Director







REPORT OF INVESTIGATIONS NO. 21





THE ARTESIAN WATER OF THE. RUSKIN AREA

OF HILLSBOROUGH COUNTY, FLORIDA


By
HARRY M. PEEK
U. S. Geological Survey






Prepared by the
UNITED STATES GEOLOGICAL SURVEY
in cooperation with the
FLORIDA GEOLOGICAL SURVEY
and the
BOARD OF COUNTY COMMISSIONERS OF HILLSBOROUGH COUNTY


TALLAHASSEE, FLORIDA
1959









AGRI-

FLORIDA STATE BOAV L'

OF

CONSERVATION




LeROY COLLINS
Governor


R. A. GRAY
Secretary of State



J. EDWIN LARSON
Treasurer



THOMAS D. BAILEY
Superintendent of Public Instruction


RICHARD ERVIN
Attorney General



RAY E. GREEN
Comptroller



NATHAN MAYO
Commissioner of Agriculture


ERNEST MITTS
Director of Conservation








LETTER OF TRANSMITTAL


Jlorida geological Survey

&Callakassee

September 9, 1959

MR. ERNEST MITTS, Director
FLORIDA STATE BOARD OF CONSERVATION
TALLAHASSEE, FLORIDA


DEAR MR. MITTS:


The Florida Geological Survey will publish as their Report of
Investigations No. 21 a comprehensive study of THE ARTESIAN
WATER OF THE RUSKIN AREA OF HILLSBOROUGH
COUNTY. This study was made by Mr. Harry M. Peek, Geologist
with the U. S. Geological Survey, in cooperation the Florida Geo-
logical Survey and with the Board of County Commissioners of
Hillsborough County.

The area in the vicinity of Ruskin is used extensively for truck
farming. During drought periods, considerable difficulty has been
experienced through the -accumulation of salts in low places, the
salts having been derived from water used for irrigation. This
study provides data that will be helpful in evaluating the problem
of salt accumulation in soils and will provide the necessary help
for a wise and conservative utilization of our water resources in
that area.
Respectfully yours,
ROBERT 0. VERNON, Director






















































Completed manuscript received
May 18, 1959
Published by the Florida Geological Survey
E. O. Painter Printing Company
DeLand, Florida
September 9, 1959


iv











TABLE OF CONTENTS



Page
Abstract -------------- ------------------- -------- ----- 1
Introduction .-. __------....... .._--------.__ 2
Purpose and scope of the investigation ---------.-------- 3
Previous investigations ---------------------_ ----------------- 4
Acknowledgments __------------------------------.. 5
Well-numbering system -------------------___-___ ...---------__ 5
Geography ...--.__---------- 7-----------__-----. 7----- 7
Climate .-----------------------. --------- --- 7
Physiography .-------. .-----------------.--- 7
Culture ------------------------- ------- -------10
Geology _-- -_-----------.---.-----. ------11
Eocene series --------------.-----_----------.------ 13
Avon Park limestone---------- 13
Ocala group _------_------_-- --- ------------ --. 13
Oligocene series ----------------__------------------- 15
Suwannee limestone --..--------_.---------- ---- --- 15
Miocene series ------------------------- 15
Tampa formation ......------------------ -----------._ ----------15
Hawthorn formation ..--------------- ------------------__ 18
Pliocene and Pleistocene series -----_-------------------- 18
Ground water ---_ ------ -------- 19
Principles of occurrence ..........------- --------------..-- 19
Ground water in Florida --_---------------------- ------ 20
Artesian water ----------------------- 20
Piezometric surface ------_---.------- 21
Ground water in the Ruskin area ------- -------------------___ 21
Artesian water .......------ ------------- ---- ------ 23
Current-meter exploration _--__--__. ._______ 23
Fluctuation of artesian pressure head --- ---_------- 23
Piezometric surface ----------- -------- ------ -- 36
Depth of water levels below land surface --- ---- 40
Wells --...__ -- ---------------. -- ------------ 44
Temperature -------------------------------------------- 4 46
Quantitative studies -___ --------- ------ 47
Quality of water ---------------- ---- ._---.------- ---- 54
Salt-water contamination --_---------------------- ----- 64
Relative salinity of the artesian water -------- ------ 65
Sources of contamination -....--- _-------- ---6.. 69
Summary and conclusions ------------------------- 70
References ....----. .------- ----------.----.--- 72
Water-level measurements ------_--- ---------------- ---------- 75
Well logs -----_____---- __ ---------- 81







ILLUSTRATIONS


PI


Plate


1 Map of the Ruskin area showing location of wells ..---_... facing
Figure
1 Map of the peninsula of Florida showing location of Hillsborough
County and the Ruskin area
2 Precipitation and temperature at Tampa _-........------------------
3 Map of the Ruskin area showing the Pleistocene terraces -----
4 Geologic cross sections showing the formations penetrated by water
wells in the Ruskin area _- ----------------- ..-----.---.--
5 Map of the Ruskin area showing the configuration and altitude
of the top of the Suwannee limestone -- ------------....-------
6 Map of the Ruskin area showing the configuration and altitude
of the top of the Tampa formation .- -- .----. ----.. -----
7 Map of peninsular Florida showing the piezometric surface of the
Floridan aquifer in 1949 -.......... ....------------- -


Graph
Graph
Graph
Graph
Graph
Graph
Graph
Graph
Graph
Graph
Graph
Graph
Graph
Graph
Graph
Graph
Graph


showing well-exploration
showing well-exploration
showing well-exploration


showing
showing
showing
showing
showing
showing
showing
showing
showing


well-exploration
well-exploration
well-exploration
well-exploration
well-exploration
well-exploration
well-exploration
well-exploration
well-exploration


showing well-exploration
showing well-exploration
showing well-exploration
showing well-exploration
showing well-exploration


data
data
data
data
data
data
data
data


for well
for well
for well
for well
for well
for well
for well
for well


40-30-1 ---
43-26-4 ---
43-26-7 __--------
43-26-12 --
43-26-26----
44-24-15 ---
44-25-42 --
44-26-10 __---


data for well 44-26-31 --
data for well 45-24-13 ------


data for
data for
data for
data for
data for
data for
data for


25 Graphs showing well-exploration data


well 45-24-17
well 45-24-23
well 45-25-20
well 45-26-2 .
well 45-26-3 .
well 46-24-7 -
well 46-24-8
for wells 4


16-24-12 and


46-24-17 _------ --------------.
26 Graphs showing well-exploration data for wells 47-23-8 and
48-23-15 .- --- --
27 Hydrographs of wells 42-19-1 and 44-25-39 ----..----.---------...
28 Hydrographs of wells 39-30-1, 40-27-7, 41-30-5, and 42-28-9 ---
29 Hydrographs of wells 43-26-2, 44-25-5, 46-24-7, and 52-20-1 -.--..----
30 Hydrographs of and chloride content of water from wells 43-26-12
and 43-26-26 ____ -.----- ....------. ... ...- --------
31 Hydrographs of and chloride content of water from wells 44-25-38
and 44-26-31 _- _____ ------ .--------------
32 Hydrographs of and chloride content of water from wells 45-25-8
and 46-24-4
33 Hydrographs of and chloride content of water from wells 47-23-22
and 48-23-19 ._ --.. -_ __- -
34 Effects of earthquakes and atmospheric pressure changes on the
water levels in wells 42-19-1 and 44-25-39 ..--........---------- -.. .....


age
4


- -- -- -- --- -- --







35 Map of the Ruskin area showing the piezometric surface of the
Floridan aquifer in October 1952 ---_-- ___-- ------.- ---- 51
36 Map of the Ruskin area showing the piezometric surface of the
Floridan aquifer in May 1953 ---_ .---_.. ----_ 52
37 Map of the Ruskin area showing the area of artesian flow and
depth of water level below land surface ------_ ----------- 53
38 Logarithmic plot of drawdown in well 40-27-7 versus t/r2 ----_-- 54
39 Map of the Ruskin area showing wells sampled for chemical
analysis --...--. -------------.........----.... ---.. -- ... ........._.......... .... --------55
40 Map of the Ruskin area showing the sulfate content of water from
the Florida aquifer .....----- ----- ..-. --- __...... .... .. .. ........... 59
41 Map of the Ruskin area showing the chloride content of water from
the Tampa formation -- --..-.-. __ _--__ ------- -- ._ 60
42 Map of the Ruskin area showing the chloride content of water
from the Suwannee limestone and older formations ----.-------- 61
43 Map of the Ruskin area showing the dissolved-solids content of
water from the Floridan aquifer .----- ....------------___.__ 63
44 Map of the Ruskin area showing the hardness of water from the
Floridan aquifer _-... ----.....- -.. ------.----. -- ....--__ -... .. 64
45 Graph showing well-exploration data for well 44-25-28 ----------67
46 Graph showing well-exploration data for well 47-23-22 --- ------_ 68
47 Graph showing well-exploration data for well 48-23-8 ----------- 68


TABLES

Table Page
1 Pleistocene terraces and shorelines of the Ruskin area----------- 9
2 Geologic formations penetrated by water wells in the Ruskin area 12
3 Stratigraphic nomenclature of the upper Eocene in Florida _---- 14
4 Summary of results of the current-meter explorations ------- -- 24
5 Chemical analyses of artesian water from wells in the Ruskin area 57
6 Measurements of water level in wells in the Ruskin area .-------- 75
7 Logs of selected wells in the Ruskin area __----.------_-- ------81
















~r

































































































































i








THE ARTESIAN WATER OF THE RUSKIN AREA
OF HILLSBOROUGH COUNTY, FLORIDA
By
HARRY M. PEEK

ABSTRACT

The Ruskin area of Florida, as defined in this report, comprises
about 200 square miles in southwestern Hillsborough County. The
area has a subtropical climate and an average rainfall of more
than 50 inches, so that it is well suited to livestock farming and
growing of winter vegetables. As in much of the State, however,
truck crops and pasture require irrigation during periods of
relatively light rainfall; thus, large quantities of water are
withdrawn through many hundreds of wells during the growing
season.
The surface formations in the Ruskin area consist pre-
dominantly of deposits of sand, limestone, and shells, of
Pleistocene and Pliocene age, which range in thickness from a few
feet to about 60 feet. These deposits are underlain by the
Hawthorn formation, of middle Miocene age, which is exposed at
a few places. The Hawthorn consists of calcareous clay or marl
interbedded with limestone and sand and ranges in thickness from
less than 10 feet in the northern part of the area to more than
150 feet in the southern part. The Tampa formation,1 of early
Miocene age, underlies the Hawthorn formation and ranges in
thickness from 50 feet in the northern part of the area to about
200 feet in the southern part. Its upper surface ranges in eleva-
tion from about sea level in the northern part of the area to about
250 feet below sea level in the southern part. The Tampa is the
youngest of the limestone formations of Tertiary age, which have
a total thickness of several thousand feet in southwestern
Hillsborough County. The other limestone formations penetrated
by water wells in the area are the Suwannee limestone, of
Oligocene age, and the Ocala group and Avon Park limestone, of
Eocene age.

1The stratigraphic nomenclature used in this report conforms to that of
the Florida Geological Survey. It conforms also to that of the U. S.
Geological Survey, with the following exceptions: the Tampa limestone is
herein referred to as the Tampa formation and the Ocala limestone is
referred to as the Ocala group.






FLORIDA GEOLOGICAL SURVEY


The Hawthorn and younger formations are the source of some
domestic and other small water supplies, but the large quantities
of water required for irrigation and industrial use are obtained
from the underlying limestone formations.
The Suwannee limestone and Tampa formation are the principal
sources of artesian water in the area, although the older limestones
yield water to a few wells. The water in these formations occurs in
permeable zones that are separated by relatively impermeable
beds of considerable thickness. The water is replenished by rain-
fall in western Polk County and eastern Hillsborough County, and
it is confined under pressure by the relatively impermeable strata
within the formations and by the overlying Hawthorn formation.
The artesian aquifer has a transmissibility coefficient of about
115,000 gpd per foot and a storage coefficient of about 0.0006.
Significant fluctuations of artesian-pressure head result from
daily and seasonal variations in withdrawal of water from wells.
During periods of heaviest withdrawal, the piezometric surface
is lowered about four to five feet throughout the area and more
than eight feet at some places. The artesian pressure head
declined progressively in the coastal area during a period of
extensive agricultural development from 1950 to 1952. Since 1952,
however, seasonal fluctuations have decreased in magnitude and
a slight progressive rise in artesian head has occurred locally, as
a result of a decrease in withdrawals. Records of water levels
in wells not affected by local variations in discharge indicate that,
regionally, the artesian head declined progressively in 1955-56.

INTRODUCTION

Along much of the coast of Florida, salt water is present in
part or all of the principal water-bearing formations. Thus, the
problem in many coastal areas is to find supplies of fresh water
that are adequate to meet increased demands and are economically
feasible to develop. The problem in other areas is to protect
present supplies from contamination by salt water encroaching
from the sea or from formations that lie beneath the fresh-water
supply. Encroachment from either source may be induced by
excessive lowering of the fresh-water head.
During recent years, expansion of agriculture in the Ruskin
area of southwestern Hillsborough County has greatly increased
the use of artesian water for irrigation which has lowered the
artesian head in the area. The detection of -relatively salty water
in some wells has suggested that salt water may be encroaching






REPORT OF INVESTIGATIONS NO. 21


from Tampa Bay. Recognizing this possibility, the Board of
County Commissioners of Hillsborough County requested the U. S.
Geological Survey and the Florida Geological Survey to make a
study of the ground-water resources in the Ruskin area.
Accordingly, the Federal Geological Survey began an investigation
in October 1950, in cooperation with the above agencies.
Most of the fieldwork of the investigation was done by the
author prior to June 1953, under the immediate supervision of
H. H. Cooper, Jr., then District Engineer of the Federal Survey,
in Tallahassee. Completion of the fieldwork and preparation of
the report were under the immediate supervision of M. I.
Rorabaugh, present District Engineer of the U. S. Geological
Survey. The entire investigation was made under the general
supervision of A. N. Sayre, Chief of the Ground Water Branch,
U. S. Geological Survey.

PURPOSE AND SCOPE OF THE INVESTIGATION

The purpose of the investigation was to make a detailed study
of the geology and ground-water resources of southwestern
Hillsborough County, with the primary objective of determining
whether the artesian water had been contaminated by salt water
from Tampa Bay or from other sources. The investigation, there-
fore, consisted of several phases, as described below:

1. An inventory of about 650 selected wells, to obtain pertinent
information related to the occurrence and use of ground water in
the area.
2. Collection of data on water levels, to determine trends and
magnitude of water-level fluctuations, and for use in constructing
maps showing the altitude to which water will rise in artesian
wells.
3. Collection of water samples from selected wells, for chemical
analysis.
4. Determination of the chloride content of water from wells, to
ascertain the location and extent of areas in which the artesian
water has been contaminated.
5. Periodic determination of the chloride content of water from
selected wells, to understand the relation between the chlorinity
of the water and the artesian pressure head.
6. A study of geologic conditions as related to the occurrence
and movement of ground water.
7. Exploration of selected wells with a deep-well current meter,





FLORIDA GEOLOGICAL SURVEY


to determine the depth, thickness, and relative productivity of the
principal water-bearing zones.
8. Resistivity surveys and determination of the chloride content
of water samples collected at several different depths in selected
wells, to determine the relative chlorinity of the water in the
Principal water-bearing zones.
9. Studies to determine the water-transmitting and water-
storing capacities of the different formations.


PREVIOUS INVESTIGATIONS

No detailed study of the geology and ground-water resources
of southwestern Hillsborough County has been made previously.
However, the Florida Geological Survey and the U. S. Geological
Survey have published several reports that include brief
discussions' of the geology and the occurrence of ground water in
Hillsborough County.
One of the earlier reports (Matson and Sanford, 1913, p. 320,
323; pl. 5) contains a generalized map of the Pleistocene terraces,
logs of wells, descriptions of formations exposed at the land sur-
face, and a brief discussion of the ground water of Hillsborough
County. A report by Sellards and Gunter (1913, p. 258-262, fig.
16) includes a summary of the geology and ground-water resources
of the county and contains a map showing the area of artesian
flow.
The geology and ground water of Hillsborough County are
described in a report by Stringfield (1936, p. 127, 128, 152). This
report includes maps of the Florida Peninsula showing the area
of artesian flow, the height above sea level to which water will
rise in wells that penetrate the principal artesian aquifer, and the
areas in which water with a chloride content of more than 100
parts per million (ppm) is present at moderate depths. Water-
level measurements and other data from several wells in the
county also are included.
A report by Parker and Cooke (1944, pl. 3) contains a map
showing the general configuration of the Pleistocene terraces in
southern Florida, including Hillsborough County. Reports by
MacNeil (1949, p. 105, pl. 19), Cooke (1945, p. 11-13, 245-312),
and Parker (Parker and others, 1955, p. 89-124, pl. 10) discuss
the Pleistocene terraces of Florida and contain maps showing
the configuration of the terraces and shorelines in Hillsborough
County.








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141 333 .i
EXPLANATION 1
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INSET ;5I I

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41 ~ 37 *


Plate 1. Map of the Ruskin area showing location of wells.









REPORT OF INVESTIGATIONS NO. 21


The formations penetrated by wells and those exposed at the
surface are described in some detail in a report on the geology of
Florida by Cooke (1945, p. 34, 42, 47, 125, 208, 222, 290, 305).
A report by Vernon (1951, figs. 11, 33, pl. 2) contains maps
showing the subsurface features of some of the formations under-
lying Hillsborough County.
Chemical analyses of water from several wells and springs in
Hillsborough County are included in a report by Collins and
Howard (1928, p. 216-217) and one by Black and Brown (1951,
p. 64).

ACKNOWLEDGMENTS

Appreciation is expressed to the many well owners in the
Ruskin area who contributed information and otherwise aided
the investigation. Special acknowledgment is made to the well
drillers who collected rock cuttings and furnished much valuable
information. These include H. J. Tucker, Howard Morrill, and
E. E. Boyette, of Ruskin; and May Bros. of Tampa.

WELL-NUMBERING SYSTEM

The well-numbering system used in this report is based on
latitude and longitude. The Ruskin area, which lies between 270
and 280 north latitude and 82 and 830 west longitude (fig. 1),
has been divided into quadrangles by a grid of 1-minute parallels
of latitude and 1-minute meridians of longitude, as shown on
plate 1. The wells have been assigned numbers according to their
location within this grid. Each well number consists of three
parts: the first part is the latitude, in minutes, of the south side
of the 1-minute quadrangle in which the well is located; the
second part is the longitude, in minutes, of the east side of the
same 1-minute quadrangle; and the third part is the number of
the well within the quadrangle. For example, the number 43-25-4
designates the fourth well in the quadrangle bounded by latitude
43' on the south and longitude 25' on the east. The degree of
latitude and longitude are not included as a part of the well
number, as they are the same for all wells used in this report.
Well locations are shown on the map, plate 1. Complete well
descriptions, locations, and other data are published in Florida
Geological Survey Information Circular No. 22 and may be
obtained for one dollar per copy.






FLORIDA GEOLOGICAL SURVEY


Figure 1. Map of the peninsula of Florida showing location of Hillsborough
County and the Ruskin area.







REPORT OF INVESTIGATIONS NO. 21


GEOGRAPHY

The Ruskin area, as defined for this report, comprises about
200 square miles in southwestern Hillsborough County (fig. 1).
It is bounded on the south by Manatee County and extends
northward to the 27056' parallel of north latitude. From Tampa
Bay, which forms the western boundary, the area extends eastward
to the 82017' meridian of west longitude.

CLIMATE

The Ruskin area has a subtropical climate, with a mean
temperature of about 720 F, according to the U. S. Weather
Bureau. The mean monthly temperatures at Tampa range from
61.5 F in January to 820 F in August, as shown in figure 2. For
comparison, the figure shows the average maximum and minimum
monthly temperatures during 1956.
The records of the U. S. Weather Bureau show (fig. 2) that
the average yearly precipitation at Tampa during the period from
1891 through 1955 was 49.94 inches; the range was from 32.25
inches in 1908 to 67.19 inches in 1912. The average monthly rain-
fall ranged from 1.04 inches in November to 8.11 inches in July,
and more than 70 percent of the annual precipitation occurred
between June 1 and September 30.

PHYSIOGRAPHY

The Ruskin area is in the Terraced Coastal Lowlands of Vernon
(1951, p. 16), a subdivision of the Coastal Plain province. The
topographic forms consist mostly of marine terraces and associated
features that were developed during the Pleistocene time, when
the sea at several times stood above or below its present level.
The topography may be divided generally into units-a relatively
flat coastal area and a hilly upland area. The coastal area is about
three to six miles wide and extends inland from Tampa Bay to
an escarpment that represents the shoreline of the Pamlico sea
of late Pleistocene time. The coastal area slopes gently toward
the bay from the base of the escarpment, which is about 25 feet
above sea level. Most of the coastal area is between 5 and 15 feet
above sea level, but it contains a few low hills and ridges having
altitudes of 30 feet or more. The hilly upland area extends east-
ward from the Pamlico escarpment, gradually increasing in
altitude to more than 100 feet in the vicinity of Wimauma. Most







FLORIDA GEOLOGICAL SURVEY


6

2
I.aCz
C PW O
0IS~ Cd0 te


Figure 2. Precipitation and temperature at Tampa.

of the upland area consists of low rolling hills having relatively
flat summits, at altitudes of 50 to 90 feet. The marine terraces and
associated features have been modified to some extent by stream
dissection. Numerous ponds, depressions, and swamps occur in
the poorly drained parts of the area.
The history of the Pleistocene epoch and the marine terraces
and deposits associated with the fluctuations of sea level in Florida
are discussed in detail in reports by Cooke (1945, p. 11-13, 245-
312), Vernon (1951, p. 15-42, 208-215), and Parker (Parker and
others, 1955, p. 89-124). The rise and fall of the sea is attributed
to the advance and retreat of the great continental ice sheets,
the sea level rising during interglacial periods and falling during
glacial periods. When the sea remained relatively stationary for
long periods, shoreline features and marine plains were developed.
The remnants of five marine terraces of Pleistocene age and the
general configuration of four shorelines have been mapped in the
Ruskin area (Cooke, 1945, figs. 43-47; Parker and others, 1955,
pl. 10), as listed in the following table:


22 MAXIMUM (1891-1955)
20- -
18 AVERAGE (1891-1955) VVV
MINIMUM (1891-19551 K


7U.1


Y n ~2
W e e ~


2
W5
z
U-







REPORT OF INVESTIGATIONS NO. 21


TABLE 1. Pleistocene Terraces and Shorelines of the Ruskin Area

Terrace Altitude of shoreline
(feet above msl)

Sunderland ------- ...........------------- ..----------1701
Wicomico .-- ---------_--_-.-..-.. -----------.----........ 100
Penholoway ----------------- -------_. ... ----------....._.. 70
Talbot ----------- --------------................... 42
Pamlico ..-----------25

'Sunderland shoreline not present in Ruskin area.

Figure 3 shows the general boundaries of the Pleistocene ter-
races in the Ruskin area, as determined from aerial photographs,
topographic maps, and field observation. The highest and oldest
surface lies above the Wicomico shoreline and represents the
remnants of the Sunderland terrace (Cooke, 1945, p. 278-279).
The sea was about 170 feet above the present level when the
Sunderland was formed, and practically all of south Florida was
submerged.
During Wicomico time, the sea stood about 100 feet above the
present level and all the Ruskin area was submerged except the
Sunderland terrace and associated islands. The shoreline of the
Wicomico sea is marked by an escarpment that is well preserved
in many places.
The Penholoway terrace was formed when the sea stood at
an altitude of about 70 feet. The general configuration of the
shoreline can be distinguished on aerial photographs, on topo-
graphic maps, and in the field (fig. 3).
The shoreline of the Talbot sea, which stood at an altitude of
about 42 feet, is poorly defined throughout most of the area, and
in many places the shoreline escarpment coincides with the
escarpment of the Pamlico terrace.
The Pamlico terrace is the youngest Pleistocene terrace that
has been recognized in the Tampa Bay area. It was formed when
the sea was about 25 to 30 feet above the present level. The shore-
line of the Pamlico sea is marked by an escarpment which is well
preserved throughout most of the area. The base of the escarpment
is generally about 25 feet above sea level.
Surface drainage in the Ruskin area is principally through the
Little Manatee River, the Alafia River, and Bullfrog Creek, all of
which flow into Tampa Bay. Much of the coastal area is drained
by small streams that extend inland from Tampa Bay for relatively






FLORIDA GEOLOGICAL SURVEY


Figure 3. Map of the Ruskin area showing the Pleistocene terraces.

short distances. Canals have been dug throughout most of the
area to supplement the natural drainage.

CULTURE

The principal towns in the Ruskin area are East Tampa,
Gibsonton, Riverview, Ruskin, Sun City, and Wimauma (pl.
1). U. S. Highway 41 passes through all towns along the coast







REPORT OF INVESTIGATIONS NO. 21


and connects them with Tampa to the north and Bradenton to the
south. U. S. Highway 301 provides a north-south route through
the eastern part of the area. State Highway 674 and several
other paved roads- connect the U. S. Highways. The Atlantic
Coastline Railroad provides transportation in the coastal area and
the Seaboard Air Line Railroad serves Wimauma and the eastern
part of the area.

GEOLOGY

The surface formations over most of the Ruskin area consist
of undifferentiated deposits of Pleistocene age, although beds as
old as Miocene are exposed at some places. The geologic forma-
tions penetrated by water wells are listed and briefly described
in table 2, and geologic cross sections are shown in figure 4. The
subsurface formations are described on the basis of rock cuttings,
electric logs, and drillers' logs of wells in and adjacent to the
Ruskin area. Those penetrated by water wells in the area are the
only formations discussed in this report.


9 V o
0 (Pleis tocene5 Pliocene) -o

20 -200
A G TAMPA i
-300 FORMAION -- -300
p'j (Oligocene)






--4oo ------ ----^ -soo'^-
00-400
I .-300L TAMPRA L-
-.60o ---- ------ ^ OCALA GROUP ,j a 0^, o 0
S(Eoen e) 40 (Oli-occ E
-7 -too ^ : :cer^e
igure g rs seion sh n t m o


IL 0 --e- in -AuWaTHORN 0 ara
/I FORMATION
S -100 (Mioenc) -100
TAMPA -
-200 I FORMATION -200S
3-'
W SUWANNEE LIMESTONE
-400 -4
(Oligocene) r I "
-500 500
Figure 4. Geologic cross sections showing the formations penetrated by water
wells in the Ruskin area.







12 FLORIDA GEOLOGICAL SURVEY

TABLE 2. Geologic Formations Penetrated by Water Wells in the Ruskin Area

Thickness
Age Formation Characteristics (feet)

Pamlico sand Sand, shells, limestone, and calcareous
Older Terrace ay 0- 60
deposits Sand, silt, and some clay.

I Undifferentiated Sand and gravel of quartz and phos- 0- 20?
Deposits phate, clay, and bone fragments.
SSand, shells, gravel of quartz and 0- 25?
phosphate, and lignite.

Hawthorn Clay and marl, gray, greenish gray to 10-150
formation blue-gray, sandy, phosphatic, inter-
bedded with sandy limestone, sand,
silt and shells. Serves as a confining
layer for the water in the underlying
limestones but is the source of small
Water supplies.

Tampa Limestone, creamy white, gray, and tan, 50-200
formation fairly hard, porous to dense, sandy,
fossiliferous, silicified in part. A very
productive source of artesian water.

Suwannee Limestone, creamy white to tan, fairly 200-225
limestone soft, granular, porous, fossiliferous,
Crystalline and dolomitic in part. Prob-
Sably a more productive source of
Water than the Tampa, but water is
somewhat more mineralized.


Ocala group Limestone, white, cream and tan, soft, 250
granular, chalky, fossiliferous, co-
quinoid in part. Penetrated by only a
few wells in the Ruskin area but may
be a very productive source of ar-
tesian water. The water is probably
Highly mineralized in the coastal area.
Avon Park Limestone, white to tan, soft, somewhat 600-700
limestone chalky, granular, foraminiferal; dolo-
mite, tan to dark brown hard crystal-
line, lignitic in part, very porous. A
very productive source of artesian
water but tapped by very few wells.
Water is salty in the coastal area.







REPORT OF INVESTIGATIONS NO. 21


EOCENE SERIES

The Eocene limestones have a combined thickness of about
5,000 feet in the Tampa Bay area, but only the upper part of this
limestone section is tapped by water wells.

AVON PARK LIMESTONE

The upper part of the late middle Eocene limestone in Florida
was named the Avon Park limestone by Applin and Applin (1944,
p. 1680, 1686). It is the oldest formation exposed at the surface
(with outcrops in Citrus and Levy counties) and is also the oldest
formation penetrated by water wells in southwestern Hillsborough
County.
The upper part of the Avon Park consists predominantly of
white to tan, soft, chalky, granular limestone containing many
foraminifers and other fossils. The lower part is principally a
tan to dark brown, hard, crystalline dolomite containing
carbonaceous material but very few fossils.
The Avon Park limestone is probably about 600 to 700 feet
thick in the Ruskin area. The top of the formation ranges in
depth from about 575 feet below sea level in the northern part of
the area to about 900 feet in the southern part.
The formation is very permeable, owing to the extensive
development of solution channels, and is a productive source of
artesian water. However, relatively few wells in the area penetrate
the Avon Park, because it contains highly mineralized water in
much of the coastal zone and sufficient quantities of water of better
quality can be obtained from the younger formations at shallower
depths.

OCALA GROUP

Until recent years, all the limestone deposits of late Eocene
age in peninsular Florida were considered as a single formation,
the Ocala limestone. As shown in table 3, Cooke (1945, p. 53-62)
and Applin and Applin (1944, p. 1683) referred all late Eocene
limestones to the Ocala; however, Applin and Applin recognized
upper and lower members of the formation, on the basis of
lithologic and faunal differences. After completion of his studies
in Citrus and Levy counties, Vernon (1951, p. 111-171) separated
the late Eocene limestones into two formations--the Ocala lime-
stone, restricted to the upper part, and the Moodys Branch







FLORIDA GEOLOGICAL SURVEY


formation. He also divided the Moodys Branch formation into
two members-the Williston member, to include the upper part,
and the Inglis member, to include the lower part. Puri (1953, p.
130) changed the name of the Ocala limestone (as restricted by
Vernon) to the Crystal River formation, and gave formational
rank to the Williston and Inglis members of Vernon's Moodys
Branch formation. The Crystal River, Williston and Inglis
formations, as described by Puri, are now referred to as the Ocala
group by the Florida Geological Survey.


TABLE 3. Stratigraphic Nomenclature of the Upper Eocene in Florida


U. S. Geological Survey Florida Geological Survey

Cooke (1945) Applin (1944) Vernon (1951) Puri (1953)

Upper Ocala limestone Crystal
member (restricted) River
formation
--_ __ ______ -Ocala
Ocala Ocala
Lower Moodys group
limestone limestone member Branch Williston Williston
formation member formation

Inglis Inglis
member formation


The Ocala group lies unconformably on the Avon Park lime-
stone in southwestern Hillsborough County and is probably about
250 feet thick. The top of the formation ranges in depth from
about 300 feet below sea level in the northern part of the area to
about 600 feet in the southern part. The upper part of the Ocala
is a creamy white to tan, soft, somewhat granular, chalky,
coquinoid limestone, composed of the remains of foraminifers,
mollusks, echinoids, and other fossils which are loosely cemented
in a fine, granular, chalky matrix. The lower part of the Ocala
is more granular and less chalky than the upper part and contains
fewer foraminifers.
The Ocala is penetrated by relatively few wells in the Ruskin
area, although it may be a productive source of water. In the
coastal area, the water in the Ocala has a considerably higher
mineral content than the water in the younger limestones.







REPORT OF INVESTIGATIONS NO. 21


OLIGOCENE SERIES
SUWANNEE LIMESTONE
The Suwannee limestone, as defined in this report, includes all
deposits of Oligocene age in the Ruskin area. The Suwannee is
differentiated from the underlying Eocene formations and the
overlying Miocene formations on the basis of lithology and fauna
and is separated from these formations by unconformities.
The upper part of the Suwannee is generally a creamy white
to tan, soft, granular, fossiliferous limestone, but at some places
it contains beds that are crystalline, dolomitic, and partly silicified.
The lower part of the formation is generally a tan to brown, soft
to hard, granular to dense limestone that is harder, more crystal-
line and dolomitic, and less fossiliferous than the upper part. The
formation contains abundant remains of mollusks, echinoids, and
foraminifers. Specimens of the foraminifer Rotalia mexicana are
fairly abundant throughout the formation. The occurrence of
Dictyoconus cookei and Coskinolina floridana is generally restricted
to the lower part of the Suwannee.
The top of the Suwannee limestone in the Ruskin area ranges
in depth from about 75 feet below sea level in the northern part
of the area to about 400 feet in the southwestern part. The
formation has a fairly uniform thickness of about 200 to 225 feet.
The contours on the map in figure 5 show the configuration and
approximate altitude of the top of the formation.
The Suwannee limestone is probably the most productive
source of artesian water generally tapped in the Ruskin area. In
the coastal area, however, the water in the Suwannee is somewhat
more mineralized than the water in the overlying Tampa
formation.
MIOCENE SERIES
The deposits of Miocene age in the Ruskin area are herein
referred to the Tampa formation of early Miocene age (Cooke,
1945, p. 1070) and the Hawthorn formation of middle Miocene
age. Both formations are of marine origin, but they represent
different depositional environments and are separated .by un-
conformities.
TAMPA FORMATION
The Tampa formation lies unconformably on the Suwannee
limestone of Oligocene age and consists of white, gray, and tan
hard, dense, sandy limestone. It is crystalline and dolomitic in





FLORIDA GEOLOGICAL SURVEY


H C OLLS8ROUGH COUNTY /
/ -'. -JC7-- UN -
/ -,^<^ ~j MANATEE" COUNTY' '

Figure 5. Map of the Ruskin area showing the configuration and altitude of
the top of the Suwannee limestone.

part and contains silicified layers. The formation is generally
fossiliferous, containing echinoid plates and spines, tests of
ostracods and foraminifers, and many molds and casts of mollusks.
Specimens of the foraminifers Archaias and Sorites are fairly
abundant throughout most of the Tampa.
The top of the Tampa formation ranges in depth from a little
below sea level in the northern part of the Ruskin area to about





REPORT OF INVESTIGATIONS NO. 21


Figure 6. Map of the Ruskin area showing the configuration and altitude of
the top of the Tampa formation.

250 feet below sea level in the southern part. The contours on the
map in figure 6 show the configuration and approximate altitude
of the top of the formation in the area. The thickness of the
Tampa is about 50 feet near the northern boundary of the area and
increases southward, in the direction of dip, to about 200 feet (fig.
4). The average thickness is about 175.feet in the area south of
Big Bend Road (pl. 1).






FLORIDA GEOLOGICAL SURVEY


The Tampa formation is a productive source-of artesian water
in the Ruskin area. Most of the water is obtained from relatively
thin zones that have a high permeability, owing to the many inter-
connecting cavities formed by solution of the limestone.

HAWTHORN FORMATION

The Hawthorn formation, as defined in this report, includes
all marine deposits of middle Miocene age. It was deposited in
shallow water and consists predominantly of gray, blue-gray and
gray-green, sandy, calcareous, phosphoritic clay interbedded with
thin layers of gray, white, and tan sandy phosphoritic limestone,
and thin beds of sand and shells. The limestone layers are
dolomitic, silicified, and fossiliferous in part. The altitude of the
top of the Hawthorn ranges from about 25 feet above sea level
to about 50 feet below sea level, and the upper part of the
formation is exposed at several places in the area. The thickness
increases from north to south in the direction of dip, ranging from
less than 10 feet in the northern part of the area to more than
150 feet in the southern part (fig. 4).
The thin beds of sand and limestone yield artesian water to
some wells in the area, but the Hawthorn is not generally a very
productive source of water. Because of the thickness and low
permeability of the clay beds, the Hawthorn serves as a confining,
layer for the water in the underlying limestones.

PLIOCENE AND PLEISTOCENE SERIES

The Hawthorn formation is overlain at some places by about
5 to 10 feet of sediments that consist of shells, sand, carbonaceous
material, and gravel of phosphorite and quartz. At other places
it is overlain by several feet of sediments consisting predominantly
of sand but containing some clay, gravel of quartz and phosphate,
bone fragments, and shark teeth. The age of these sediments has
not been determined, but it is probably late Miocene or Pliocene.
Pleistocene sediments of the higher terraces consist mostly
of undifferentiated sands that range in thickness from about 10
feet to 60 feet. The surface of the Pamlico terrace/is underlain
by sand, sandy clay, and shells. The beds of limesto e and shells,
which pinch out near the Pamlico shoreline and are generally less
than 20 feet above sea level, were apparently deposited during
late Pleistocene time. However, these beds were referred by Cooke
(1945, p. 222-223) to the Caloosahatchee marl of Pliocene age.







REPORT OF INVESTIGATIONS NO. 21


Phe Pleistocene deposits beneath the Pamlico surface range in
sicknesss from about 10 feet to 50 feet, except where they have
been completely eroded by streams. The Pleistocene deposits are
the source of a few domestic water supplies in the area.

GROUND WATER

PRINCIPLES OF OCCURRENCE

Practically all the water of the earth moves through the vast
circulatory system known as the hydrologic cycle. Water
condenses from the moisture in the atmosphere and falls as rain
or snow, moves over or beneath the land surface to the oceans,
and is returned to the atmosphere. Actually, the cycle may be
modified or completed at any time after the water condenses from
the atmosphere, as evaporation may begin even before the water
reaches the earth and continue throughout the entire cycle. Great
quantities of water are returned to the atmosphere by
evaporation from vegetal surfaces (transpiration).
Much of the water that falls on the land surface as rain or
snow runs off into streams, lakes, or other bodies of surface water,
and a part eventually reaches the oceans. Some water is returned
to the atmosphere by evaporation directly from land and water
surfaces, and a part of it is absorbed by the soil or surficial rocks
and becomes subsurface water. The amount of water than sinks
directly into the ground from each rainfall depends on many
factors, such as the slope of the land surface, vegetal cover,
intensity of the rainfall, and previous moisture content and
character of the surface material.
Subsurface water may be divided into two general classes-
suspended water and ground water. Suspended water is the water
in the zone of aeration-the zone in which the interstices of the
soil or rocks are not completely filled with water. Ground water is
the water in the zone in which all the interstices are completely
filled with water under greater than atmospheric pressure. This
saturated zone is the reservoir that yields water to all springs and
wells.
The water in the zone of saturation may occur as (1)
unconfined ground water (under nonartesian conditions), or (2)
confined ground water (under artesian conditions). Where the
ground water is not confined-its upper surface is under
atmospheric pressure and is free to rise. and fall-it is said to be
under nonartesian conditions. Its upper surface is called the water





FLORIDA GEOLOGICAL SURVEY


table. Where the water is confined in a permeable bed that is
overlain and underlain by relatively impermeable beds, its upper
surface is not free to rise and fall and it is said to be under
artesian conditions. The term "artesian" is applied to ground
water that is confined under sufficient pressure to cause it to rise
above the top of the permeable bed that contains it, but not
necessarily above the land surface.
An aquifer is a formation, group of formations, or part of a
formation, in the zone of saturation, that is permeable enough to
transmit usable quantities of water. Recharge is the process of
replenishment of the water in an aquifer, and areas in which it
occurs are known as recharge areas. Generally, unconfined
aquifers may receive direct recharge from precipitation through-
out their lateral extent, whereas artesian aquifers may receive
such recharge only where their confining beds are absent or
relatively permeable.
The piezometric surface of an aquifer is an imaginary surface
to which water from an artesian aquifer will rise in tightly cased
wells that penetrate the aquifer. Where the piezometric surface is
above the land surface, artesian wells will flow under natural
pressure.

GROUND WATER IN FLORIDA

Ground water occurs in Florida under both nonartesian and
artesian conditions. Nonartesian conditions are generally
restricted to the shallow deposits of sand, gravel, shells, and lime-
stone which form many aquifers of relatively small areal extent.
These deposits are the source of many domestic water supplies
throughout the State and also of public and industrial supplies
in areas where the deeper formations contain salty water. The
water in the unconfined aquifers is generally replenished by local
rainfall.

ARTESIAN WATER

Most of Florida is underlain by a thick section of permeable
limestone formations of Eocene, Oligocene, and Miocene age. These
formations compose an extensive artesian aquifer from which
most of the large ground-water supplies of the State are obtained.
Stringfield (1936, p. 125-132, 146) described the aquifer and
mapped the piezometric surface in 1933 and 1934. The name
"Floridan aquifer" was introduced by Parker (Parker and others,






REPORT OF INVESTIGATIONS NO. 21


1955, p. 188-189) to include "parts or all of the middle Eocene
(Avon Park and Lake City limestones), upper Eocene (Ocala lime-
stone), Oligocene (Suwannee limestone), and Miocene (Tampa
limestone, and permeable parts of the Hawthorn formation that are
in hydrologic contact with the rest of the aquifer)," The artesian
water is confined by relatively impermeable layers in the limestone
formations and by the overlying clay beds of Miocene age which
extend over most of the State. The water in the artesian aquifer
is replenished chiefly by rainfall in areas where the confining beds
are absent, are breached by sinkholes, or are sufficiently permeable
to permit the passage of water from the land surface into the
limestone.

PIEZOMETRIC SURFACE

The configuration of the piezometric surface in peninsular
Florida is shown by the contour lines in figure 7. These lines
represent the height, in feet above sea level, to which water will
rise in wells that penetrate the Floridan aquifer. They indicate
the areas in which recharge occurs; and, through inference, the
general direction of water movement in the Floridan aquifer may
be deduced. In areas of recharge, the piezometric surface is
relatively high. The water moves away from these areas in the
direction of steepest gradient, at right angles to the contour lines,
toward areas of discharge, where the piezometric surface is
relatively low. In central Florida the piezometric surface forms
an elongated dome which is centered in northern Polk County.
The presence of this dome indicates that the lake region of Polk
County is the center of a relatively large area of recharge which
probably extends into adjacent counties (Stringfield, 1936, p. 148).
The water enters the limestone formations in this area through the
numerous sinkholes and at places where the confining bed is either
absent or slightly permeable.

GROUND WATER IN THE RUSKIN AREA

In the Ruskin area the water in the Pleistocene sands and other
permeable beds that lie above the Hawthorn formation is generally
unconfined and is replenished by local rainfall. A few small
domestic water supplies are obtained from these formations, but
most domestic and larger supplies are obtained from the permeable
beds of the Hawthorn formation or the underlying limestones.






FLORIDA GEOLOGICAL SURVEY


Figure 7. Map of peninsular Florida showing the piezometric surface of the
Floridan aquifer in 1949.







REPORT OF INVESTIGATIONS NO. 21


ARTESIAN WATER

In the Ruskin area, as in most of the State, the Floridan
aquifer is the principal artesian aquifer. The water in this
aquifer is replenished chiefly by infiltration of rainfall in the re-
charge area centered in northern Polk County. From there it
moves southwestward into the Ruskin area, as suggested by the
configuration of the contours in figure 7.
The Avon Park limestone and the Ocala group of Eocene age,
which are productive sources of water in much of peninsular
Florida, are probably capable of yielding large quantities of water
in the Ruskin area. These formations are penetrated by very few
wells in the area, however, as the Suwannee limestone and Tampa
formation are sufficiently productive to supply most wells.
The water in the Suwannee limestone and Tampa formation
occurs in permeable zones separated by relatively impermeable
layers which retard vertical movement of the water and serve
locally as confining beds.
The Hawthorn formation consists predominantly of clay and
serves as a confining bed for the water in the Floridan aquifer.
Thin beds of sand and limestone within the formation contain
artesian water that is the source of many domestic supplies and
some small irrigation supplies. The artesian pressure head in
the Hawthorn is considerably less than the head in the Floridan
aquifer; thus, the Hawthorn probably receives some recharge by
upward percolation of water from the Floridan aquifer.
Current-Meter Exploration: In order to determine the depth,
thickness, and relative productivity of the different water-bearing
zones in the limestone formations, explorations were made in
several selected wells with a deep-well current meter, a device
for measuring the velocity of flow of water through a well bore.
The results of the current-meter traverses are shown graphically
in figures 8 through 26, which also include well-construction data,
electric logs, and resistivity and chloride content of the water. The
velocity of the water is expressed in revolutions per minute (rpm)
of the current meter. Actual flow rates, which are a function of
velocity and cross-sectional area, cannot be computed accurately,
as the diameter of the uncased part of the wells is not uniform.
A summary of the information obtained from the current-
meter explorations (figs. 8-26) is given in table 4.
Fluctuations of Artesian Pressure Head: Fluctuations of
artesian pressure head range from a fraction of a foot to several
feet and are caused by one or more of several factors. The larger





FLORIDA GEOLOGICAL SURVEY


TABLE 4. Summary of Results of the Current-Meter Explorations


Depth of principal
producing zones
(feet below msl)


40-30-1 250 200 to 245
245 to 355
355 to 360
420 to 445


43-26-4 100 320 to 325
365 to 395
420 to 480


43-26-7 300 245 to 285
315 to 325
355 to 365


43-26-12 300 125 to 150
235 to 250
325 to 350


43-26-26 300 100 to 120
200 to 270
310 to 410


44-24-15 50 280 to 290


44-25-42 350 120 to 160
295 to 335
355 to 370


44-26-10 200 100 to 285
305 to 320
345 to 370


44-26-31 350 395 to 420+


45-24-13 350


70 to 190
395 to 404


Well
number


Rate of
flow
(gpm)


Depth of principal
producing zones
(feet below msl)


45-24-17 300 220 to 260
295 to 310
340 to 345

45-24-23 125 155 to 170
255 to 265
365 to 380

45-25-20 200 90 to 105
170 to 265

45-26-2 125 110 to 140
295 to 305

45-26-3 250 170 to 195
265 to 275
355 to 385
410 to 420

46-24-7 350 195 to 495

46-24-8 350 85 to 105
235 to 275
395 to 415

46-24-12 150 70 to 80
195 to 237+

46-24-17 250 170 to 190
295 to 333

47-23-8 125 150 to 160
255 to 275


48-23-15


150 175
215
265


190
240
280


Well Rate of
number flow
(gpm)


I







REPORT OF INVESTIGATIONS NO. 21


AE FORMA- SELF-POTENTIAL RELATIVE RESISTIVITY O(ro rWATE r
A e Wi (rpm of current meter)
IOmv 5 25ohms 50 10_
4 I


z
0
4
a:
0







Wd
Z
_j


PLEISTOCENE
5 PLIOCENE

z







I
z



z


Figure 8. Graph showing well-exploration data for well 40-30-1.

fluctuations generally result from daily and seasonal changes in
withdrawal of water from wells or from variations in recharge
from rainfall. Minor fluctuations are caused by tides, atmospheric-
pressure changes, winds, earthquakes, and passing trains. The
minor fluctuations of water levels and their causes are discussed
in detail in a paper by Parker and Stringfield (1950).
Records from continuous recording gages on two wells and
periodic water-level measurements in about 20 wells provide
information on the fluctuations of artesian pressure head in the
Ruskin area during a period of about 6 years. Hydrographs pre-
pared from the records of the continuous recording gages on
wells 42-19-1 and 44-25-39 are shown in figure 27. Hydrographs
of 16 wells in which water levels were measured periodically are
I hown in figures 28-33. Water-level measurements in other wells
are listed in table 6 and in Information Circular No. 22.


(


LJ
-I
W

z -200-
Z

0
I-

Ct -300i

Iii
[L

u-
'U


--400-

LUJ
0


-500-





FLORIDA GEOLOGICAL SURVEY


VELOCITY OF WAT I ER CHLORIDE
FORMA- WELL VELOCITY CONTENT
AGE TION 436 (rpm of current meter) kparts per million)
0 50- 100 0 50


PLEISTOCENE
3 PLIOCENE


z
oro
OcI


Figure 9. Graph showing well-exploration data for well 43-26-4.

The hydrograph of well 42-19-1 (fig. 27) shows the seasonal
fluctuations and regional trend of the artesian pressure head from
August 1951 to December 1956. The seasonal use of water i:s
indicated by the declines in head during periods of least rainfall,
when large quantities of water were being used for irrigation.
The rises in head, corresponding to periods of greater rainfall,
are due primarily to a decrease in discharge but at times may


0





,.J
LLU
> -100
LLU
-i

LU
(/


LLi
: -200
0

L1

L
Ll

Mr-300
1--
LJ
LU
LL


I-
0 -400
LU
0


o











1
_ _













t





=:=:| :::::


-500






REPORT OF INVESTIGATIONS NO. 21


-200-
bJ w

0.Z




0
-- -


-300-
U-


I--- _--
Ld
W



u-

--400 U J-
0 0
a- Iw
o0 __-
z


-500 --

Figure 10. Graph showing well-exploration data for well 43-26-7.


indicate an increase in recharge. The hydrograph indicates that
the magnitude of seasonal fluctuations has increased from about
four feet in 1952 to about eight feet in 1956. The lowest recorded
water level- in this well was 29.6 feet, in April 1956. The
progressive increase in the magnitude of seasonal fluctuations and
the general downward trend of the artesian pressure head
throughout the period of record reflect the regional increase in
both seasonal and perennial use of water.
The hydrograph of well 44-25-39 (fig. 27) shows the effects
of seasonal differences in local withdrawals. The slight downward













































Figure 11. Graph showing well-exploration data for well 43-26-12.






REPORT OF INVESTIGATIONS NO. 21


trend of the artesian pressure head from 1950 to 1952 probably
reflects the increased use of water resulting from expansion of
agriculture during this period. The hydrograph indicates that
local use of water has been relatively stable since 1952.
The hydrographs in figures 28-33 also show seasonal
fluctuations due to local discharge. Some hydrographs indicate
that discharge has remained relatively stable since about 1952,
whereas others show a general upward trend of the artesian
pressure head since 1953, thus indicating a decrease in local use of
water.
Although the principal fluctuations of artesian head in the
Ruskin area -are caused by changes in the rate of withdrawal of
water from wells, observable changes are caused by earthquakes,
atmospheric-pressure changes, and other factors.
Earthquake waves passing through the earth's crust cause a
relatively rapid expansion and contraction of artesian aquifers,
which results in fluctuations of the artesian pressure head. The
magnitude of these fluctuations in a particular well may range
from a few hundredths of a foot to several feet, according to the
intensity of the earthquake and the distance of the epicenter from


Figure 12. Graph showing well-exploration data for well 43-26-26.






30 FLORIDA GEOLOGICAL SURVEY


WELL VELOCITY
FORMA-
AGE TION 44-24-15 (rpm of current meter)
0 25 50
0- PLEISTOCENE
a PLIOCENE

zz
cr 0



0)
-J 0
o_





4
1 V




0 0

z -200- 2

<



0

oc o



Z
LL-


-400 w u -
Lu
z 0

a z
^ 2 A








REPORT OF INVESTIGATIONS NO. 21


0



_j
W
Id
W

V/)
-100-
W
Q
Id



z:
4
Id


0

LlJ
UIC
13:
td
U.
W


Id
S-300-
Id


z
X"
&
Q 30


R WE I VELOCITY OF WATER CHLORIDE CONTENT OF WATER RESISTIVITY OF WATER
AGE FORM I WE5-LL (tpm of current meter) (ports per million) (mllliohms)
TION 44-2- 50 10 0 15 0 O 25 1 200 250 31C


a PLIOCENE
^ 0


li


0

o z









uz p __I __ I


o ,J __ .._-




Figure 14. Graph showing well-exploration data for well 44-25-42.


Figure 15. Graph showing well-explorationdata for well 44-26-10.


_____ 1 _____ I _____ ~I1 _____Ii I......4~.


IPLFISt6eENE I ~~ '- 7' -' '



























- <



2 z







WOO

I o
w


0 C







Figure 16. Graph showing well-exploration data for well 44126-31.





DEPTH, IN FEET BELOW MEAN'SEA LEVEL

o o o o
0 0 0
9
C OLIGOCENE M I C E N E m
S0 ... o -q
HAWTHORN no n
S SUWANNEE LIMESTONE TAMPA FORMATION FORMAT
0 FORMATION m
N





0, o-

N- --


a
. a -0



_: -- O-- -- ---z--------z--------^ r
SZE"
1t -
';,| __ =O






FLORIDA GEOLOGICAL SURVEY


the well. The effects of earthquakes on water levels in wells 42-
19-1 and 44-25-39 are shown on the hydrographs in figure 34,
which were traced from the charts of continuous recording gages.
An earthquake in southern California, which occurred on July 21,
1952, had a magnitude of 7.5 (based on a comparative scale that
ranges from a minimum intensity of 1 to a maximum intensity of
10) and caused maximum water-level fluctuations of 0.85 foot
in well 42-19-1 and 0.46 foot in well 44-25-39. An earthquake
of 8.5 intensity near the east coast of Kamchatka, in Siberia, on
November 4, 1952, caused maximum water-level fluctuations of
0.86 foot in well 42-19-1 and 1.24 feet in well 44-25-39.
Daily changes in atmospheric pressure cause minor fluctuations
of artesian pressure head which are observable in most wells,
but these changes may be masked or modified by fluctuation due
to tides, local pumping, or other factors. The effects of
atmospheric-pressure changes on the water level in well 44-25-39
may be seen on the hydrographs in figure 34, even though these
fluctuations are probably modified somewhat by effects of ocean
tides and local discharge. The effects of changes in atmospheric
pressure on the water level in well 42-19-1, which is not affected
by local pumping or ocean tides, are shown also in figure 34. The

SFCRMA- SELF-POTENTIAL ;J RELATIVE I STIVIT VELOCITY OF WATER CH LORI
TlOlYE 250m (pm o! current melo PPCONTEN
101 0 5ohms so t0 100 5 0 ppm 50

X Z





z
O n- 3----



-____
0 t


Figure 18. Graph showing well-exploration data for well 45-24-17.






REPORT OF INVESTIGATIONS NO. 21


periods of low atmospheric pressure in the early morning and
late afternoon are represented by high water levels. The highest
atmospheric pressures occur about noon and midnight and are
represented by the lowest water levels. The magnitude of the
fluctuations caused by changes in atmospheric pressure is generally


Figure 19. Graph showing well-exploration data for well 45-24-23.






FLORIDA GEOLOGICAL SURVEY


less than 0.1 foot but may be considerably greater during a
hurricane, when extremely low pressure may cause water levels
to rise several tenths of a foot.
Piezometric Surface: The contours on the map in figure 35 show
the configuration of the piezometric surface of the Floridan
aquifer in October 1952. The piezometric surface at that time
was more than 45 feet above mean sea level (msl) in the south-
eastern part of the area and from there sloped northwestward to
sea level in the vicinity of East Tampa, indicating a general
movement of the artesian water from southeast to northwest. In
the eastern part of the area, where interference by discharging
wells is negligible, the gradient of the piezometric surface is about
three to five feet per mile. The depressions in the piezometric
surface along the coast reveal the areas in which water was being
discharged from the aquifer. The deepest depressions, and hence
the areas of greatest discharge, are indicated by the closed
contours north of Ruskin and northwest of Sun City.
The depressions in the piezometric surface are probably the
result of discharge from wells. However, as most of the wells are
cased to depths of less than 50 feet, the depressions may reflect,
in addition, losses of artesian pressure head caused by upward
leakage of water from the Floridan aquifer into the shallow
formations through unused wells. The relatively large depression
indicated by the contours north of Adamsville is probably the result
of perennial withdrawal of large quantities of water for industrial
use and also some natural discharge from springs and seeps.

VELOCItY OF WATER CHLORIDE
SFORMA- SELF POTENTIAL RELATIVE RESISTIVITY (r o current O ter CITER
TION 10Imw 25 ohms 0 50 100
.-.. 0 50 too 150 >
0- PLEISTOCPEE a ------ -- wl --20
PLIOCEE NE



100 W -- -----___^------ ^ ~ -
z l "

Sa 2
So IU




1 O- I
Fi

Figure 20. Graph showing well-exploration data for well 45-25-20.



























t-
I






12


M

-A


Figure 21. Graph showing well-exploration data for well 45-26-2.






FLORIDA GEOLOGICAL SURVEY


The contours on the map in figure 36 represent the
piezometric surface in May 1953, during an extended period of
dry weather when large quantities of ground water were being
withdrawn for irrigation. The altitude of the piezometric surface
ranged from more than 40 feet above msl in the southeastern
part of the area to sea level in the vicinity of East Tampa. A
comparison of figures 35 and 36 shows that the piezometric
surface was generally about 5 feet lower in May than in October


< z WELL VELOCITY OF WATER CHLORIDE WA TENT
S45-26-3 (rpm of current meter) (parts per million)
0- 45-26-3
< 50 100 150 0 50
0- PLEITCEN -
PUOCENE z

zz



-- 300- .
0-0 z
>O
-LJ
i100- M-

Li
zz -




S200- r --
0 o
.j 2 r_


-J



300-
z

iSi Li 4
Q o
W


Figure 22. Graph showing well-exploration data for well 45-26-3.







FORMA- SELF POTENTIAL jv RELATIVE RESISTIVITY VELOCITY OF WATER CHLORIDE CONTENT
TION 0 25ohms (rpm of current meter) (parts per million))
SI L ______ _____ 0 50 100 150 200 250 0 50


51 vi


W
W
-I
LJ

5 100-


U,
z
Lu

B 200
0



I.-
w
L


300


a
Lu
0W


TOC ENE
OCENE



01




z
0
I_


0
U-





I


z L

Lu



0 Z
- UJ

o I


400-


Figure 23. Graph showing well-exploration data for well 46-24-7.


-0

0


I






40 FLORIDA GEOLOGICAL SURVEY


as a result of the combined drawdown of several hundred irrigation
wells.
Depth of Water Levels Below Land Surface: The area of
artesian flow and the approximate depth to water below the land
surface in wells that penetrate the Floridan aquifer, based on the
piezometric surface in May 1953, are shown in figure 37. The
area of flow includes a zone about one to three miles wide along
the coast, south of the Alafia River, and extends completely across
the Ruskin area along the valley of the Little Manatee River. It
includes also a narrow zone along the Alafia River in the vicinity
of Riverview. The depth to water below the land surface is



AGE FR- WELL (rpm of current meter)
OGT TN 46-24-8


-1





,J




U-
- 100-




Ij
Z 1







a-
S200-



t-
LJ
o


L.j


S300-

CL
C.




400-


I lk


PLEISTOCENE
a PLIOCENE

z |
0

X LL.


0 50 100 150 290 250






.)<


Figure 24. Graph showing well-exploration data for well 46-24-8.
Figure 24. Graph showing well-exploration data for well 46-24-8.









-J '
.J
W
IJJ
-J


V)

< 100



0
_J
w


w 200-
LJ
2
I
I-

0
300-


^ S WELL VELOCITY OF WATER
S z 46-24-12 (rpm of current meter)
1 6 0 50 100 150
PLEISTOCENE
& PLIOCENE S


U




z
z
w 0

o I

o "

I-2




0 destruction

S^ -J=L -----
(Do ______ _____ _____ _____
OU ____ __ __


u 100
C,
z




0
-j
200-


w
I- .
UJ

2


a.
30
UJ


Figure 25. Graphs showing well-exploration data for wells 46-24-12 and
46-24-17.


WELL VELOCITY OF WATER
7 o 46-24-17 (rpm of current meter)
.< 0 50 100
PLEISTOCENE 8
PLIOCENE "
z z



o =
t z



u ___



o a.
4


0





W W
0 U
0






o L,








o --
0 i


-1

0





-I



=z
O


-o.
I-












E WELL VELOCITY OF WATER CH'ORIDW CONTENT
Fok WELF WATER.
TION (rpm of current metir) (ports per million)
482315 0 100 I 0 50 0
PLEISTCENE =
PLIOCENE




zw I
,w ---00
0







U1 I 256
0

-- _--=0 0



0 -300


Figure 26. Graphs showing well-exploration data for wells 47-23-8 and 48-23-15.










-j 3
W 34

<32

~n 30
z Well 42-19-1, I MILE WEST OF WIMAUMA
,w, 28



S18_____________
w
< m 6


14
I P_ I1_ .i 1_


12T


Well 44-25-39,2 MILES NORTH OF RUS KIN I
1950 1951 1952 1953 1954 1955 1956

Figure 27. Hydrographs of wells 42-19-1 and 44-25-39.






44 FLORIDA GEOLOGICAL SURVEY

greatest in the east-central part of the area, where it is 50 feet
or more. Throughout most of the area, however, it is less than
25 feet.
Wells: About 650 wells were inventoried during this investi-
gation, and the information obtained is given in Information
Circular No. 22. As shown in plate 1, most of the wells are in
a zone about three to five miles wide along the coast, and most
of them flow, at least intermittently. They range in depth from
60 to more than 700 feet, but most of them are between 300 and


14
Well 42-28-9 2 ILES NORTH OF SUN CITY__
1 L L .Ll L I 1l i IllI1s 1 ....,1 5ll l.3.. 1 .1. lL L LLlL955

Figure 28. Hydrographs of wells 39-30-1, 40-27-7, 41-30-5, and 42-28-9.







REPORT OF INVESTIGATIONS No. 21


500 feet deep. They range in diameter from 2 inches to 18
inches, but most of them are 6 to 8 inches in diameter.
Surface casings are generally seated in the Hawthorn formation,
at depths of 20 to 75 feet, although some wells contain as much
as 200 feet of surface casing. In addition to the surface casing,


14

12
Well 44-25-5, I MILE NORT-I OF RUKIN

20



16

14

12
Well 46-24-7,, MILES NORTHEAST OF RUSKIN


14

12
o,-------... .. .- --


10
8 W81-,5gq-i 1, MILE, WEST OFRIVERVI ,,, ,, ,
1951 1952 1953 1954 1955

Figure 29. Hydrographs of wells 43-26-2, 44-25-5, 46-24-7, and 52-20-1.


-J
LU

_J

*UJ

i-
>



4w
0
UZ


L-U



UJ.



z
2Z






46 FLORIDA GEOLOGICAL SURVEY

many wells are equipped with an inner casing extending to greater
depth to shut off caving sands.
The yields of the wells differ because of difference in the
permeability and thickness of the aquifer penetrated, the artesian
pressure head, and the size of the well bore. The irrigation wells
six inches or more in diameter, in the area of perennial artesian
flow, generally yield about 100 to 400 gpm.
Temperature: Measurements of the temperature of artesian
water from several hundred wells are given in Information Circular
No. 22 and a few are included in table 5. The temperature of the
water from the Hawthorn formation is generally between 740 and
76 F, and that from the Tampa formation is generally between
76 and 77.50F, depending upon the depth to the principal
producing zones. The temperature of the water from wells that
penetrate the Suwannee limestone and older formations is
generally about 780 to 790F, but it ranges from about 77.50 to
82: F, according to the depth and proportionate yield of the various
producing zones in these formations.

16 I I I I I I I I I I I





WATER LEVEL
8 iWell 43-26-12, I MILE NORTHWEST OF RUSKIN
CHLORIDE CONT NT
< 5041:--i------ -~~- -~"iaP~ -~-~~----~-- -----
50


14
Lu





WATER LEVEL
Well 43-26-26, 1 MILE NORTHWEST OF RUSKIN

w3 200
a CHLORIDE CONT NT
o 10 f. i .. 1 ll LL I I I 1 11 1 1 111 1
1951 1952 1953 1954 1955

Figure 30. Hydrographs of and chloride content of water from wells 43-26-12
and 43-26-26.







REPORT OF INVESTIGATIONS No. 21


QUANTITATIVE STUDIES

The withdrawal of water from an artesian aquifer creates a
depression in the piezometric surface in the vicinity of the point
of withdrawal. This depression generally has the approximate
form of an inverted cone and is referred to as the cone of
depression. The distance the piezometric surface is lowered at
any given point within this cone is known as the drawdown at

-i
S II -II ..- f l 1 1 11 1 i
-LJ



4 12



L WATER LEVEL
La 12


-J

to
w




AFTER .EVEL
Well 44-26-31, 2MILES NORTH OF RUSKIN

700 ----.

500 ...

200
cc













CHLORIDE CON ENT
1951 1952 N 1953 __ 1954 __ 1955

Figure 31. Hydrographs of and chloride content of water from wells 44-25-38
and 44-26-31.
and 44-26-31.






48 FLORIDA GEOLOGICAL SURVEY

that point. The size, shape, and rate of growth of the cone of
depression depends on several factors, including (1) the rate of
pumping, (2) the water-transmitting and storage capacities of
the aquifer, (3) the increase in recharge resulting from the
lowering of the piezometric surface, and (4) the decrease in
natural discharge due to the lowering of the piezometric surface.
The perennial yield of the artesian aquifer in the Ruskin area is
limited by the extent to which the piezometric surface can be
lowered without impairing the quality of the water or making
the cost of obtaining the water prohibitive.
The principal hydraulic properties of an aquifer are its
capacities to transmit and store water, for all aquifers serve as
S 20 | | | i i I1I 1 1 1 1 i111 11|1 I II I T 1 1 1 1 11 InIII I I I TI I I Ti


16 2

14--- ---






CHLORIDE CONTENT






S12-- --.-




S WATER LEVEL


z Well 45-25-8 3 MILES NORTHEAST OF RUSKIN
350- r -


















CHLORIDE CONTENT
S 50 195 195 195 194 19


and 46-24-4.







REPORT OF INVESTIGATIONS NO. 21


both conduits and reservoirs. An artesian aquifer functions
primarily as a conduit, transmitting water from places of recharge
to places of discharge; however, it is capable of storing water, by
expansion, or releasing water, by compression.
The coefficient of transmissibility is a measure of the capacity
of an aquifer to transmit water. In units commonly used by the
U. S. Geological Survey, it is the quantity of water, in gallons per
day (gpd), that will flow through a vertical section of the aquifer
one foot wide and extending the full saturated height, under a
unit hydraulic gradient, at the prevailing temperature of the
water. The coefficient of storage is a measure of the capacity of
an aquifer to store water, and is defined as the volume of water
released from or taken into storage per unit surface area of the
aquifer per unit change in head normal to that surface.


Well 48-23-19, + MILE WEST OF ADAMSVILLE


100 -- .

50Q CHLORIDE, CONTENT


K\KKA2~


iZIZSlI:


SA


.W 142


WATER LEVEL
z Well 47-23-22, IhMILES SOUTHWEST OF ADAMSVILLE
>50
a150 ------------- .^S -- ---- aBKsa5,f

CHLORINE CONTENT -
1951 1952 1953 1954 1955

Figure 8833. Hydrographs of and chloride content bf water from wells 47-23-22
and 48-23-19.


~____I~I


I W I---


.v


I1







FLORIDA GEOLOGICAL SURVEY


Figure 34. Effects of earthquakes and atmospheric-pressure changes on the
water levels in wells 42-19-1 and 44-25-39.


-J
> 14
LJ


-2
S13


2


Li
i,
U-

z
-j

LJ
UJ 38
_j
Cr 14
--


13



12


NOVEMBER 1952
1 2 3 4 5 6











Well 42-19-1










Well 44-25-39
I






REPORT OF INVESTIGATIONS NO. 21


In order to determine the transmissibility and storage
coefficients of the Floridan aquifer in the Ruskin area, a pumping
test was made in August 1955. Well 40-27-6, one-half mile east of
Sun City, was pumped at the rate of 650 gpm for a period of 31
hours, beginning at 9:15 a.m. on August 18 and ending at 4:12
p.m. on August 19. Throughout the period of pumping, water-
level measurements were made periodically in well 40-27-7, which


Figure 35. Map of the Ruskin area showing the piezometric surface of the
Floridan aquifer in October 1952.






FLORIDA GEOLOGICAL SURVEY


is 0.12 mile northwest of the pumped well, to determine the rate
and magnitude of drawdown. The coefficients obtained are not
necessarily correct for all parts of the area, but they are considered
to be representative.
The Theis graphical method, as described by Wenzel (1942, p.
87-89), was used to compute the transmissibility and storage
coefficients from the drawdown produced in well 40-27-7. This


Figure 36. Map of the Ruskin area showing the piezometric surface of the
Floridan aquifer in May 1953.






REPORT OF INVESTIGATIONS NO. 21


method relates the drawdown in the vicinity of a pumping well
to the rate and duration of discharge and is based on several
simplifying assumptions which include the following: (1) the
aquifer has an indefinite areal extent, (2) the aquifer is
homogeneous and transmits water with equal facility in all
directions, (3) the discharge well obtains water from the full
thickness of the aquifer, (4) the coefficient of transmissibility is


Figure 37. Map of the Ruskin area showing area of artesian flow and depth
of water level below land surface.






FLORIDA GEOLOGICAL SURVEY


constant at all places and at all times, (5) the discharge well has
an infinitesimal diameter, and (6) water taken from storage by
the decline in water level is discharged instantaneously with the
decline in head.
The observed data for well 40-27-7 matched against the type
curve, as shown in figure 38, yielded the following figures:
Where W (u) = 1.0, s = 0.65
and where u = 0.1, t/r2 = 1.0 x 10-7
114.6 QW(u)
These figures inserted in the formulas T = 1 W--
s
uTt
and S = 1.87 r- give a transmissibility coefficient of 114,600 gpd/ft
and a storage coefficient of .0006.

QUALITY OF WATER

The water that falls on the earth's surface as rain or snow is
practically free of mineral matter except for very small quantities
of atmospheric gases and dust. Therefore, the mineral constituents
and the degree of mineralization of ground water depends generally

1 :---------------------------------10.






1.0 1.0
S 0Q650gpm
4W(u).10 0.1; W(u)1.0

T 114.6Q W(u)
S114.6 x 650x1.0
o 0.65
I T114,600gpd/fl.
o,, ___ / I. uTt 0.1x4.600x.OxI1 A


Figure 38. Logarithmic plot of drawdown in well 40-27-7 versus t/r2.






REPORT OF INVESTIGATIONS NO. 21


upon the composition and solubility of the soil and rocks through
which the water passes. In some places, mineralization of ground
water may result from the mixing of relatively fresh water with
highly mineralized, residual sea water within the water-bearing
formations.
Chemical analyses of water samples from 29 selected wells in
the Ruskin area (fig. 39) were made by the Quality of Water


Figure 39 Map of the Ruskin area showing wells sampled for chemical
analysis.






FLORIDA GEOLOGICAL SURVEY


Branch of the U. S. Geological Survey. The results of these
analyses are shown in table 5 and are discussed briefly-below.
The concentrations of mineral constituents are given in parts
per million (ppm)-1 ppm is approximately equivalent to 8.34
pounds per million gallons of water. The specific conductance is
expressed in micromhos at 250C, and the hydrogen-ion content in
standard pH units. The concentration limits given for the ions,
unless otherwise stated, are taken from standards for drinking
water prescribed by the U. S. Public Health Service (1946).
Calcium (Ca) is dissolved principally from limestone, which is
predominantly calcium carbonate, by water containing carbon
dioxide. Calcium is a principal cause of hardness in water.- As
indicated by the analyses, the water from the Floridan aquifer
in the Ruskin area has a calcium content ranging from 81 to
275 ppm.
Magnesium (Mg) is dissolved principally from dolomite or
dolomitic limestone and, like calcium, is a major cause of hardness
in water. As magnesium is one of the principal mineral con-
stituents of sea water, ground water that has been contaminated
by sea water usually has a relatively high magnesium content.
The water from the Floridan aquifer in the Ruskin area has a
magnesium content ranging from 33 to 109 ppm. (See table 5.)
Sodium (Na) and potassium (K) are dissolved in small
amounts from many types of rocks, but they constitute only a small
to moderate part of the total mineral content of fresh ground
water. The sodium content of water that has been contaminated
by sea water is generally high, as sea water is principally a solution
of sodium chloride. Water from the Floridan aquifer in south-
western Hillsborough County contained 7 to more than 100 ppm
of sodium and potassium.
Bicarbonate (HCO,) in ground water results from the solution
of limestone and other carbonate rocks. Hardness caused by
calcium and magnesium equivalent to the carbonate and
bicarbonate is known as carbonate hardness in water. The
bicarbonate content of water from the Floridan aquifer is
relatively high, ranging from about 150 to more than 225 ppm.
Sulfate (SO,) in ground water may be due to the oxidation
of sulfide minerals or the solution of sulfate salts in the formations.
Large quantities of sulfates in water may impart a bitter taste.
and have a laxative effect. Sulfates of calcium and magnesium
cause boiler scale. The concentration limit of sulfate in drinking
and culinary water is considered to be about 250 ppm. The sulfate
content of water from the Floridan aquifer in southwestern




TABLE 5. Chemical Analyses of Artesian Water from Wells in the Ruskin Area
(Analyses by U. S. Geological Survey; chemical constituents in parts per million)


cd4

IC/ riS iu I

C a Cd UQ 0 w. 0
-4 .,q 2 W ;4 z 1


39-18-1 4-4-55 .. ...... 81 83 6.7 158 192 16 .... .... 480 338 696 8.1 82
39-80-5 4-8-55 .... ...... 110 50 8.3 178 300 28 .... .... 692 480 950 7.8 78.3
40-27-3 4-7-55 .... .... 104 48 18 182 275 35 .... .... 656 457 894 7.7 78.2
40-29-4 4-8-55 .... ...... 101 43 16 188 260 28 .... .... 634 429 876 7.9 77
40-29-5 4-8-55 .... ...... 84 39 25 200 215 25 .... ...- 554 370 806 7.9 76
40-29-24 4-7-55 .... ... 90 44 12 194 232 22 .... .... 594 406 827 7.9 77
41-30-5 4-7-55 .... ...... 110 50 17 182 320 24 .... .... 706 480 943 7.9 77
42-28-8 4-7-55 .... ...... 97 43 14 190 255 21 .... .... 606 419 846 7.9 77
42-28-9 4-7-55 .... ...... 117 52 12 188 332 23 .. .... 718 506 987 7.9 78.5
43-24-6 4-14-65 .... ...... 105 46 9.9 190 272 24 .... .... 632 451 886 7.9 78.1
43-24-9 4-14-55 .... ...... 83 38 10 198 185 22 ... .... 536 363 745 8.0 76
43-26-2 4-7-55 .... ...... 115 51 11 180 330 21 .... .... 702 496 950 7.8 78
43-26-12 8-9-53 21 0.10 234 96 74 170 678 202 0.7 0.9 1,560 978 1,920 7.5 79
43-27-6 4-14-55 .... ...... 135 59 10 182 405 22 .... .... 854 580 1,090 7.9 78
43-28-4 4-14-55 .. ...... 104 58 12 190 305 22 .... .... 674 478 938 7.9 77
44-24-1 7-27-55 ... ...... 81 86 21 210 165 26 .... .... 484 350 686 7.3 76.5
44-25-1 4-8-55 .... ...... 95 43 7.4 192 232 22 .... .... 590 414 825 7.9 77
44-25-38 4-8-55 .. ...... 177 75 43 172 475 148 .... .... 1,230 750 1,690 7.6 79
44-26-25 7-27-55 .... ...... 135 55 18 186 388 25 .... .... 800 563 1,010 7.4 77.5
44-26-31 3-5-53 17 .69 199 81 89 168 582 190 .9 .8 1,350 830 1,780 7.3 80


I









a.
l-I'
03
02







Table 5 (Continued)




.s IE" ^
~A


aa A 8L01 I d 0
C S z 9k El1 J4 j i I 4 j? aI


.6
.14
0.06




.28


105
276
122
87
162
161
177
206
170


47
109
52
38
69
60
68
79
65


16
108
16
14
86
15
16
76
52


156
162
178
228
170
198
181
176
172


812
821
864
188
475
455
525
610
510


26
270
19
14
94
28
26
157
88


653
1,840
750
531
1,100
909
1,010
1,340
1,080


456
1,140
518
878
688
648
721
889
693


870
2,800
956
718
1,420
1,110
1,220
1,720
1,370


78



77.5
76
77
79.5
77


45-24-7
46-24-4
46-24-7
47-20-1
47-28-22
48-22-5
48-22-7
48-23-8
48-28-19


7-27-55
3-6-53
8-10-53
8-6-68
4-8-55
7-27-55
7-27-55
7-27-55
8-6-58






REPORT OF INVESTIGATIONS NO. 21


Hillsborough County is relatively high, ranging from about 165
to more than 800 ppm. Throughout the coastal area, the sulfate
content is more than 250 ppm (fig. 40).
Chloride (Cl) in small quantities is dissolved from most soils
and rocks and is found in large quantities in ground water that
has been contaminated by sea water. Chloride salts do not
generally decrease the potability of water except when present in


Figure 40. Map of the Ruskin area showing-the sulfate content of water from
the Floridan aquifer.





FLORIDA GEOLOGICAL SURVEY


quantities sufficient to cause a salty taste. The chloride content
of water from the Floridan aquifer in the Ruskin area ranges
from about 15 ppm to more than 1,000 ppm. The chloride content
of water from the Tampa formation is shown in figure 41, and
that from the Suwannee and older formations is shown in figure
42. The chloride content of the artesian water is discussed in
more detail under the heading "Salt-Water Contamination."
Iron (Fe) occurs in almost all rocks, but the quantity of iron


Figure 41. Map of the Ruskin area showing the chloride content of water
from the Tampa formation.






REPORT OF INVESTIGATIONS No. 21


dissolved by ground water is relatively small in comparison with
the quantity of more soluble minerals. Water containing more
than about 0.3 ppm of iron causes stains on fixtures,
utensils, and clothing; and water containing 0.5 to 1.0 ppm has an
objectionable taste. Iron can generally be removed from water by
aeration and filtration. The iron content of water from six wells
in the Ruskin area ranged from 0.06 to 0.69 ppm (table 5).
Fluoride (F) is present in minor amounts in most ground


Figure 42. Map of the Ruskin area showing the chloride content of water
from the Suwannee limestone and older formations.






FLORIDA GEOLOGICAL SURVEY


water. Water containing fluoride in excess of 1.5 ppm may cause
mottling of children's teeth during their formation (Cox and Ast,
1951, p. 641-648). In concentrations of 1.5 ppm or less, fluoride is
recognized as being beneficial to dental health through reducing
tooth decay and is added to many public water supplies for this
reason. As shown in table 5, the fluoride content of water from
six wells that penetrate the Floridan aquifer ranged from 0.4
ppm to 1.2 ppm.
The dissolved-solids content of ground water represents the
approximate amount of mineral matter in solution. Water
containing less than 500 ppm of dissolved solids is generally of
good chemical quality, according to the U. S. Public Health Service
drinking-water standards, and water containing as much as 1,000
ppm may be used for public supplies if a less mineralized water is
not available. The concentration of dissolved solids in water from
the Floridan aquifer in the Ruskin area ranges from slightly less
than 500 ppm to more than 1,800 ppm. (See fig. 43 and table 5.)
The hardness of water is due principally to the salts of calcium
and magnesium. The most noticeable effects of hardness are the
formation of curds and the lack of suds when soap is added to
the water, and the formation of a scale in vessels in which the
water is heated. Water having a hardness of 60 ppm or less is
generally satisfactory for most purposes. Water having a hardness
between 60 and 120 ppm requires treatment for many industrial
uses. Water having a hardness of more than 200 ppm is commonly
softened for domestic and some other uses, although many private
and some public supplies having a hardness of more than 500 ppm
are not treated. The hardness of water from the Floridan aquifer
in the Ruskin area ranges from about 350 ppm in the eastern part
to more than 1,100 ppm near the coast (fig. 44).
The specific conductance of water is a measure of its capacity
to conduct an electric current and depends upon the concentration
and ionization of the minerals in solution. It indicates in a general
way the relative mineralization of the water. As shown in table
5, the specific conductance of water from the Floridan aquifer in
the Ruskin area ranged from 686 to 2,300 micromhos.
Hydrogen sulfide (H2S) is a gas that gives water an objection-
able odor and may cause corrosion of plumbing. Water containing
it is often referred to as "sulfur water." Aeration is generally the
most practical method of treatment. No analyses were made of
the hydrogen sulfide content of water from the Floridan aquifer
in the Ruskin area, but the odor of the gas is detectable in water
from most wells.







REPORT OF INVESTIGATIONS NO. 21


The pH of a water indicates the instantaneous concentration of
hydrogen ions. Water that has a pH of 7.0 is said to be neutral.
Water having a pH of less than 7.0 is acidic and may be corrosive;
water having a pH greater than 7.0 is alkaline and not generally
corrosive. The water from the Floridan aquifer in the Ruskin
area is slightly alkaline, the pH ranging from 7.3 to 8.1.


, ..- .. ,', \ .-' .." ,
3. .HILLSBOROUGH ,/ OU.NTY,-',,_
MANATEE COUNTY
B2'30' B2,25'


Figure 43. Map of the Ruskin area showing the dissolved-solids content of
water from the Floridan aquifer.






FLORIDA GEOLOGICAL SURVEY


SALT-WATER CONTAMINATION

In coastal areas underlain by permeable water-bearing
formations that are hydraulically connected to the sea, the depth
to salt water is directly related to the height of the fresh ground
water above sea level. The density of fresh water is slightly less
than that of sea water, so that fresh water floats on sea water in


Figure 44. Map of the Ruskin area showing the hardness of water from the
Floridan aquifer.






REPORT OF INVESTIGATIONS No. 21


much the same way that ice floats on water. The specific gravity
of sea water is generally about 1.025, whereas that of fresh water,
for practical purposes, is 1.000. Thus, with these specific gravities
a column of sea water 40 feet high will exactly balance a column
of fresh water 41 feet high. This principle was first applied to
the hydrology of coastal areas by Badon Ghyben and Alexander
Herzberg (Brown, 1925, p. 16) who found that for each foot of
fresh water above sea level there was approximately 40 feet of
fresh water below sea level. Although the 40-to-1 ratio is strictly
applicable only under a condition of static equilibrium, it applies
approximately in coastal aquifers, except in areas very close to
the shore.
Salty water is present in the Floridan aquifer at relatively
shallow depths throughout most of the coastal area of Florida. At
some places, the lowering of the artesian head by withdrawal of
large quantities of water from wells has caused the encroachment
of sea water into the aquifer. In most of the area, however, the
artesian pressure head is sufficiently high to prevent encroachment
of water directly from the sea; thus, the widespread salty water
probably represents residual sea water that entered the aquifer
prior to Recent time.
The Floridan aquifer was partly filled with sea water several
times during the interglacial stages of the Pleistocene epoch, when
the sea rose above the present level. Since the last recession of
the sea, the circulation of fresh water through the aquifer has been
gradually diluting and flushing out the salty water. In much of the
coastal area, however, a part or all of the water-bearing formations
still contain water that is too salty for most uses, although it is
considerably less salty than sea water. Excessive lowering of the
head may reverse the flushing action and cause lateral migration
of sea water into the aquifer. It may also cause an upward
migration of the salty water from the lower zones of the aquifer
into the upper part, except where such migration is retarded by
relatively impermeable strata.

RELATIVE SALINITY OF THE ARTESIAN WATER

The dissolved mineral constituents of sea water consist pre-
dominantly of chloride salts; thus, an abnormally high chloride
content of ground water is generally a reliable indicator of salt-
water contamination. Water samples from about 400 wells were
analyzed in order to determine the chloride content of the water
from the Floridan aquifer in the Ruskin area. The results of





FLORIDA GEOLOGICAL SURVEY


these analyses are included in table 5 and are shown by symbols
in figures 41 and 42.
The chloride content of the water from the Floridan aquifer
is about 10 ppm in western Polk County and about 15 ppm in
eastern Hillsborough County. It increases gradually toward
Tampa Bay, in the direction in which the water is moving.
Throughout most of the Ruskin area, the chloride content of water
from the Floridan aquifer is about 20 to 30 ppm, but in some parts
of the coastal area it ranges from 31 to more than 500 ppm.
The chloride content of water from the Tampa formation is
shown in figure 41. Most of the wells that yield water of relatively
high chloride content are in a narrow zone that extends along,the
coast from the vicinity of Adamsville to the northern boundary of
the area. The chloride content of water from these wells ranges
from less than 50 to more than 500 ppm. A few wells south of
Adamsville yield water from the Tampa containing about 35 to 40
ppm of chloride. The relatively high chloride content of the water
from these wells may represent contamination from nearby wells
that penetrate the deeper formations.
Figure 42 shows the chloride content of water from wells that
penetrate the Suwannee limestone, the Ocala group, and the Avon
Park limestone. Most of the wells that yield water of relatively
high chloride content are in a zone about a mile wide that extends
along the coast from the Little Manatee River to the northern
boundary of the area. Wells that penetrate the Suwannee limestone
in this zone yield water having a chloride content ranging from
about 30 ppm to more than 800 ppm, and wells that penetrate the
Ocala group and Avon Park limestone yield water having a chloride
content of more than 1,000 ppm. A few wells south of the Little
Manatee River yield water whose chloride content is 35 to 65 ppm.
In order to determine the relative salinity of the water from
the different producing zones in the aquifer, water samples were
collected at several depths in selected wells with a deep-well
sampler and measurements of the electrical resistivity of the
water at different depths were made in several wells. The chloride
content of water samples collected in wells is shown graphically
in figures 9-12, 14-18, 20-23, 26, and 45-47. The results of
resistivity measurements also are included in figures 14, 16, and 45.
As indicated by these graphs, the salty water enters the wells
from the deep producing zones and is diluted by fresher water
from other producing zones as it moves up the well bore. For
example, the analyses of samples collected in well 44-25-42 (fig.
14) show that the chloride content of the water from the Suwannee

















w

-'100 -,
z 0


- u
-r w

0

* 0

LJ W




400- -
Figure 45. Graph showing well-exploration data for well 44-25-28.



400- 0_

Figure 45. Graph showing well-exploration data for well 44-25-28.







DEPTH, IN FEET REFERRED TO MEAN SEA LEVEL


OLIGOCENE MIOCENE 9 m

SUWANNEE TAMPA m r
LIMESTONE FORMATION ag mz







-I
---- -------WELL
6 Casing 46-23-8



F 6


-4
oL ;









r'1


--
om
a-2






REPORT OF INVESTIGATIONS NO. 21


limestone was 225 ppm at a depth of 370 feet and 135 ppm at a
depth of 320 feet. The sharp increase in the resistivity from about
207 milliohms at 330 feet to about 256 milliohms at 315 feet in-
dicates that most of the fresh water entered the well in this
interval.
Periodic analysis of water samples shows that the chloride
content of the water varies with changes in artesian pressure
head. A decrease in head is generally accompanied by an increase
in chloride content, and vice versa. This relationship indicates
that the lowering of the head causes a vertical movement of salty
water from the deeper formations. It may also reflect variations
in the proportion of the total yield of the well that is obtained
from each formation or producing zone. During periods of heavy
withdrawal, the artesian head of the Tampa formation may be
slightly less in some places than the head of the Suwannee lime-
stone or deeper formations. This difference in head would increase
the proportional yield of the deeper formations and increase the
chloride content of the water obtained.

SOURCES OF CONTAMINATION
As indicated by the contours in figures 35 and 36, the mean
artesian head along the coast ranges from about sea level in the
area north of the Alafia River to about 18 feet above sea level
near the Manatee County line. If the 40-to-1 ratio applies, the
depth below sea level to salt water in the aquifer would be nearly
zero at East Tampa and more than 600 feet south of the Little
Manatee River. In the area south of Adamsville, the mean
artesian head is sufficiently high to prevent encroachment of water
from the sea into the Suwannee limestone (see fig. 4) ; thus, the
occurrence of relatively salty water in the Suwannee or in the
Tampa formation probably represents residual sea water that
entered the formations during Pleistocene time.
Studies of current-meter traverses show that the Floridan
aquifer contains permeable zones separated by relatively
impermeable beds of considerable thickness. The permeable zones
tapped by most wells in the area are generally less than 450 feet
below sea level. The relatively impermeable beds beneath the
principal water-bearing zones retard or prevent upward migration
of salty water from the deeper formations.
The salinity of the water in the Suwannee limestone and Tampa
formation in the area north of Adamsville is probably due in
part to residual Pleistocene sea water and in part to encroachment
of water from Tampa Bay during recent years.






FLORIDA GEOLOGICAL SURVEY


The Tampa formation is at or near the land surface in the
northern Tampa Bay area, and in 1955 large quantities of artesian
water were being discharged from the formation through springs
and seeps. The northern part of Tampa Bay is apparently the
center of a large area of natural discharge which has existed for
many thousands of years. The withdrawal of large quantities of
water from wells during recent years has lowered the piezometric
surface to sea level at some places, permitting salt water from
Tampa Bay to enter the upper part of the aquifer.
The withdrawal of large quantities of salt water at East Tampa,
through wells that penetrate the Avon Park limestone, has created
a cone of depression which extends below sea level in the vicinity
of the pumped wells but is relatively small in areal extent. The
limited extent of this cone is probably due to the salvage of natural
discharge and the induction of recharge from Tampa Bay. The
quantity of water discharged from the wells is apparently near
equilibrium with the recharge from Tampa Bay and the intercepted
natural discharge, so that the artesian head is relatively stable;
however, salt water is steadily encroaching.

SUMMARY AND CONCLUSIONS

The investigation of the ground-water resources of the Ruskin
area of Hillsborough County involved collecting and evaluating data
from about 650 wells. The principal results of the study are
summarized below:
1. The Ruskin area is underlain by a thick section of Tertiary
limestones whose upper surface ranges in depth from about sea
level in the northern part of the area to about 250 feet below sea
level in the southern part. The limestone formations penetrated
by water wells include the Avon Park limestone and Ocala group
of Eocene age, the Suwannee limestone of Oligocene age, and the
Tampa formation of early Miocene age. The Tampa is overlain by
the Hawthorn formation of middle Miocene age which consists
of sandy, calcareous clay and thin beds of limestone and sand.
2. The Suwannee limestone and Tampa formation are the
principal sources of artesian water in the area, although the deeper
limestones yield water to a few wells. The water in these
formations occurs in permeable zones which are generally separated
by relatively impermeable layers of considerable thickness. The
water is replenished by rainfall in western Polk County and
eastern Hillsborough County and is confined under pressure by
the relatively impermeable strata within the formations and by







REPORT OF INVESTIGATIONS No. 21


the overlying Hawthorn formation. The beds of limestone and
sand in the Hawthorn are the source of many domestic water
supplies.
3. Water-level records show that significant fluctuations of
artesian pressure head result from the daily and seasonal variations
in withdrawal of water from wells. During periods of heaviest
withdrawal, the piezometric surface is lowered about 4 feet
throughout the area and more than 8 feet at some places. The
artesian pressure head declined progressively in the coastal area
during a period of extensive agricultural development from 1950
to 1952. Since 1952 the seasonal fluctuations in the coastal area
have decreased in magnitude and a slight progressive increase in
artesian pressure head has occurred locally as a result of a decrease
in withdrawals. In wells not affected by local use of water the
artesian pressure head declined progressively in 1955-56.
4. Analysis of data collected during a pumping test indicates
that the artesian aquifer has a transmissibility coefficient of about
115,000 gpd/ft and a storage coefficient of 0.0006.
5. Chemical analyses show that the mineral content of the
water in the Suwannee limestone and Tampa formation is lowest
in the eastern part of the area and progressively higher toward
Tampa Bay, in the direction in which the water is moving.
Concentrations of dissolved solids range from less than 500 ppm
in the eastern part of the area to more than 1,800 at some places
along the coast, and the hardness ranges from about 350 ppm to
more than 1,000 ppm. The water in the Suwannee limestone is
somewhat more mineralized than the water in the Tampa, and that
in the Eocene formations probably is much more mineralized than
the water in the Suwannee limestone, particularly in the coastal
area.
6. The chloride content of the artesian water is about 20 to 30
ppm throughout most of the area. In a narrow zone along the
coast north of the Little Manatee River, many wells yield water
having a considerably higher chloride content, indicating that the
artesian water has been contaminated to some extent by salty
water.
In the area south of Adamsville, salt-water contamination is
apparently due to residual sea water that entered the aquifer
during Pleistocene time, as the mean artesian head along the coast
is sufficiently high to prevent encroachment of water from Tampa
Bay into the Suwannee limestone and Tampa formation. The
circulation of fresh water through the aquifer has flushed most of
the sea water from these formations, although some water from the






FLORIDA GEOLOGICAL SURVEY


Suwannee limestone has a chloride content of several hundred
ppm. The water in the Tampa formation generally contains about
30 ppm of chloride or less.
Contamination in the vicinity of Adamsville and northward is
probably due to both residual Pleistocene sea water and
encroachment of water from Tampa Bay during recent decades.
The northern part of Tampa Bay is the approximate center of an
area of natural discharge that has existed for many thousands of
years. The withdrawal of water through wells in recent decades
has lowered the artesian head to sea level at some places, permitting
water from Tampa Bay to enter the upper part of the Floridan
aquifer. Some wells that penetrate the Eocene limestones yield
water as salty as sea water.
Periodic analysis of water from selected wells shows that the
chloride content varies with significant changes in artesian pres-
sure head. The chloride content generally increases as the artesian
head declines, and vice versa. This relationship may reflect
variations in the proportion of the total yield of the well that is
obtained from each formation or producing zone, or it may indicate
that a decline in artesian pressure head results in upward
encroachment of salty water from the deeper formations. The
relatively impermeable strata in the aquifer probably retard or
prevent an upward movement of the salty water throughout most
of the area, as only a few wells have yielded water that has
shown a progressive increase in chloride content and the
contaminated zone has not expanded during the period of record.
An appreciable lowering of the artesian pressure head in the
coastal area, however, would eventually result in lateral
encroachment. It might result also in vertical encroachment in
areas where the impermeable strata are breached or absent.

REFERENCES

Applin, Esther R. (see Applin, Paul L.)
Applin, Paul L.
1944 (and Applin, Esther R.) Regional subsurface stratigraphy and
structure of Florida and southern Georgia: Am. Assoc. Petroleum
Geologists Bull., v. 28, no. 12, p. 1673-1753.
Ast, D. B. (see Cox, C. R.)
Black, A. P.
1951 (and Brown, Eugene) Chemical character of Florida's waters:
Florida State Board of Cons., Division Water Survey and Re-
search Paper 6.







REPORT OF INVESTIGATIONS NO. 21


Brown, Eugene (see Black, A. P.)
Brown, J. S.
1925 A study of coastal ground water, with special reference to Con-
necticut: U. S. Geol. Survey Water-Supply Paper 537.
Collins, W. D.
1928 (and Howard, C. S.) Chemical character of waters of Florida:
U. S. Geol. Survey Water-Supply Paper 596-G.
Cooke, C. W. (also see Parker, G. C.)
1945 Geology of Florida: Florida Geol. Survey Bull. 29.
Cox, C. R.
1951 (and Ast, D. B.) Water fluoridation-a sound public health prac-
tice: Am. Water Works Assoc. Jour., v. 43, no. 8, p. 641-648.
Ferguson, G. E. (see Parker G. G.)
Gunter, Herman (see Sellards, E. H.)
Howard, C. S. (see Collins, W. D.)
Love, S. K. (see Parker G. G.)

MacNeil, F. S.
1949 Pleistocene shorelines in Florida and Georgia: U. S. Geol. Survey
Prof. Paper 221-F.
Matson, G. C.
1913 (and Sanford, Samuel) Geology and ground waters of Florida:
U. S. Geol. Survey Water-Supply Paper 319.
Parker, G. G.
1944 (and Cooke, C. W.) Late Cenozoic geology of southern Florida
with a discussion of the ground water: Florida Geol. Survey
Bull. 27.
1950 (and Stringfield, V. T.) Effects of earthquakes, trains, tides,
winds, and atmospheric pressure changes on water in the geo-
logic formations of southern Florida: Econ. Geology, v. 45, no.
51, p. 441-460.

1955 (and Ferguson, G. E., Love, S. K., and others) Water resources
of southeastern Florida, with special reference to the geology and
ground water of the Miami area: U. S. Geol. Survey Water-
Supply Paper 1255.

Puri, Harbans
1953 Zonation of the Ocala group in peninsular Florida: Jour. Sedi-
mentary Petrology, v. 23, p. 130.

Sanford, Samuel (see Matson, G. C.)

Sellards, E. H.
1913 (and Gunter, Herman) The artesian water supply of eastern and
southern Florida: Florida Geol. Survey 5th Ann. Rept.






74 FLORIDA GEOLOGICAL SURVEY

Stringfield, V. T. (also see Parker, G. C.)
1936 Artesian water in the Florida peninsula: U. S. Geol. Survey
Water-Supply Paper 773-C.
U. S. Public Health Service
1946 Drinking water standards: Public Health Repts., v. 61, no. 11,
p. 371-384.
Vernon, R. O.
1951 Geology of Citrus and Levy counties, Florida: Florida Geol. Sur-
vey Bull. 33.
Wenzel, L. K.
1942 Methods for determining permeability of water-bearing materials,
with special reference to discharging-well methods, with a sec-
tion on direct laboratory methods and bibliography on perme-
ability and laminar flow, by V. C. Fishel: U. S. Geol. Survey
Water-Supply Paper 887.





TABLE 6. Measurements of Water Levels in Wells in the Ruskin Area
(All measurements shown in feet above or below' (-) measuring point)

Well Date Water Date Water Date Water Date Water
Number level level level level

38-81-5 8-22-52 4.2 12-23-52 8.2 8-17-53 12.6
9-29-52 8.6 5-18-58 5.8 9-14-54 12.0

89-18-1 9- 7-51 10.6 5-18-58 4.9 4- 4-55 8.0
7- 2-52 9.0 9-80-54 11.1

89-81-5 2- 1-51 11.8 8-28-51 10.7 5-18-52 8.6

40-20-1 2-19-51 -28.5 3-26-51 -24.2 6-11-51 -25.75 8- 4-53 -23.9
2-26-51 -24.5. 4-17-51 -28.0 7-11-51 -24.84 4-14-58 -25.7
8-16-51 -25.8 5- 4-51 -22.7 9- 8-51 -22.80 5-21-58 -26.75

40-24-1 2-19-51 20.1 8-16-51 22.9 4-27-51 22.5 9- 7-51 25.9
2-26-51 24.9 8-26-51 24.0 6-11-51 20.6 5-16-52 18.9

40-27-4 5-18-52 -8.75 10-10-52 1.8 8-17-53 0.7 6- 8-55, -8.18

40-28-2 11-26-51 -6.15 12- 3-51 -8.27 12-14-51 -10.50 9-29-52 -11.25

40-30-1 8-28-51 8.1 5-18-52 8.8 5-18-53 5.6
9- 7-51 7.0 10-18-52 18.2


0


0




0Z
Oi
z~j
'p







Table (, (Continued)
(All measurements shown in feet above or below ( -) measuring point)
1-- -, .....------~---


Water
level

--11.52
-18,7


Well
Number

41-24-1


41-29-23


Date


-623-52
10-10-52


10-22-52
11-18-52
12-22-58


Water
level

-14.65
-12.3


Date


Water
level


5-18-53 -19.2


1-80-58
5-21-58
8-17-58


41-80-6 2-19-51 9.3 3-16-51 9.9 4-17-51 14.6
2-26-51 8.3 3-26-51 12.7 6-11-51 9.9


3.0
4.6

10.1
1.78

8.9
4.2
4.6
-2.15


5-13-52


10-10-52
6- 8-55

10-13-52
5-14-58

6-23-52
8-25-52
9-29-52
10-10-52


2.5

6.8
2.45

11.2
8.5

4.6
2.5
5.7
7.0


10-10-52

9-27-55


9.2

5.7


5-18-53 2.9


10-22-52
1-30-58
9-30-54
6- 8-55


7.6
5.5
8.0
'1.05


Date


10-15-58
11-20-53
6- 8-55


Water
level





1.2
3.2
4.62


9- 7-51 12.2
10-10-62 13.7

10-22-52 10.3


7-27-55


0.7
-4,57
5.7


Date


9- 7-51
5-16-52


3-28-51
5-13-52
10-10-52


41-30-13


42-25-13


42-26-12


43-24-6


9- 7-51


2- 1-51
9- 6-51

9- 6-51
5-14-52

2- 1-51
3-28-51
9- 6-51
5-18-52


0


---- ------- c-I--c~~--I --- l--- --I


I- I ~ ~ c -


-





Table 6. (Continued)
(All measurements shown in feet above or below (-) measuring point)

Well Date Water Date Water Date Water Date Water
Number level level level level

48-24-17 2- 1-51 0.8 2-26-51 -4.1 4-17-51 6.9 5- 4-51 0.1
2-19-51 1.8 3-26-51 1.9 4-25-51 6.8 6-11-51 -1.6

48-25-8 9- 6-51 8.5 5-14-52 -0.5 10-10-52 9.2 10-22-52 9.7

48-25-18 2- 1-51 4.4 3-28-51 8.9 9- 6-51 6.8 5-13-52 -0.2

48-27-4 2- 1-52 9.9 9- 6-51 10.0 5-15-52 5.4 10- 9-52 11.1

4M-27-6 2-19-51 9.9 8-26-51 12.2 6-11-51 9.1 5-15-53 8.0
S2-26-51 9.9 4-17-51 14.3 9- 6-51 8.8 5-21-58 8.5
3-16-51 11.8 4-24-51 13.2 10-13-52 12.1

43-27-11 2- 1-51 11.9 9- 6-51 10.7 10-13-52 13.2
3-27-51 12.5 5-15-52 7.9

44-24-1 9- 6-51 4.1 5-15-53 -4.4 10-15-53 1.95
10-18-52 3.7 8-17-52 3.4

44-24-17 2- 1-51 4.4 3-27-51 1.7 9- 6-51 8.4 10-13-52 5.8


to
r '






Table 0, (Continued)
(All measurements shown in feet above or below ( --) measuring point)


Well
Number

44-24-20


Date


2- 1-51
8-27-51


Water
level


Date


9- 6-51
5-14-52


Water
level


9.9
-0.15


Date


10-13-52
10-22-52


Water
level

5.6
6.6


44-25-1 2- 1-51 5.6 4- 2-52 10.1 9-29-52 6.1
3-27-51 4.5 7-25-52 8.95 10- 9-52 8.5
9- 6-51 9.0 8-22-52 6.2 10-22-52 9.2

44-25-9 2- 1-51 5.7 8-27-51 8.9 9- 6-51 9.1


44-26-9


46-23-8


8-26-51


1-81-51


11.6


9- 6-51


3-26-51


12.0


5-15-52


9- 5-51 6.6


Date


Water


level





1-30.-5 6.5
11-20-58 4.1


5-15-52 0.85


10- 9-52


5-21-58


12.0


-1.1


45-24-6 1-31-51 5.2 5-15-52 0.3 10- 9-52 6.4 10-21-52 7.5

45-25-10 9- 7-51 8.5 10- 9-52 9.7 10-21-52 10.8 12-22-52 6.1

45-25-15 1-31-51 7.7 3-26-51 9.0 9- 5-51 7.2 5-15-63 2.0

45-25-18 1-31-51 9.6 9- 5-51 8.5 10- 9-62 10.1
3-26-51 11.4 6-15-52 4.15 5-21-63 ,5.2


0



'.


------I I-~---~ I





Table 6. (Continued)
(All measurements shown in feet above or below (-) measuring point)


Water
level


' Well
Number

46-28-2


46-24-9

46-24-12

46-24-15


47-20-1




47-22-2


47-22-6


47-22-12


-7.5
-9.1


Date


9- 5-51
10-10-52

10- 9-52

3-26-51

5-15-52
6-23-62

8-23-54
9-30-54
12-28-54


9- 5-51
10-10-52


8-17-53
2-25-54


4-27-51
5- 4-51


Water
level


6.5
5.1

10.4

11.1

3.25
8.3

-29.20
-28.65
-29.80


-5.85
-6.45


Date


8.2
6.8

10.0

10.2

11.1
10.0

-36.65
-29.15
-29.40


5-21-53


4- 8-55
6- 8-55

6-11-51
9- 5-51


Date


9-30-54


10-22-52

9- 5-61

8-25-52
9-29-52


1-31-51
3-26-51

9- 5-51

1-31-51

9- 5-51
4- 2-52

6-11-51
11-20-53
6-28-54


-1.65


-6.60
-6.55


2- 1-55
3-10-55
4- 8-55


Water
level

6.8


10.6

11.5

8.5
9.0


-80.75
-32.50
-31.72


1-81-51
8-26-51


5-15-53
5-21-53


3-26-51
4-17-51


Date


11-19-53

10- 9-52





6- 8-55
7-27-55
10-25-55


Water
level


6.6

11.0





-33.0
-30.45
-30.60


'"--------' ~------'


'-----"c~'





'~-----'------







Table 0, (Continued)
(All measurements shown in feet above or below ( -) measuring point)

Well Date Water Date Water Date Water Date Water
Number level level level level

47-22-18 2-19-61 0.6 2-26-51 2.1 8-16-51 3,8 3-26-51 5.1

47-28-19 9- 5-51 6-7 10-10-52 5.4 5-21-53 -0.5
5-14-52 0.2 10-21-52 5.6

47-28-21 1-31-51 3.9 9- 5-51 6.6 4-14-58 5.5
3-27-51 6.8 10-10-52 5.7 5-21-53 0.9

47-23-31 1-31-51 3.9 3-27-51 6.8 9- 5-51 6.1 5-14-52 1.25

48-22-5 8-27-51 8.7 10-10-52 2.8 11-20-52 0.25 9-30-54 1.80
9- 5-51 4.2 5-21-53 --2.5 2-25-54 0.70 7-27-55 1.30
5-14-52 -1.7 8-17-58 2.2 6-28-54 0.90
6-23-52 1.1 10-14-53 2.0 8-24-54 1.1

48-28-10 1-81-51 4.2 9- 5-51 3.6 2- 6-53 5.7
3-27-51 6.6 5-14-52 2.24 5-21-53 2.3

49-22-1 2-19-51 0.1 3-22-51 0.8 5- 4-51 0.4 9- 5-51 1.87
2-26-51 0.0 4-17-51 1.4 6-11-51 -0.8
3-16-51 0.3 4-27-51 1.3 8-13-51 1.30






REPORT OF INVESTIGATIONS NO. 21


TABLE 7. Logs of Selected Wells in the Ruskin Area

Well 40-28-2
(Florida Geol. Survey No. W-2323)
Lithology Depth Below
Land Surface
Pleistocene and Pliocene

Sand, white, quartz, fine to medium, subrounded to well-
rounded, carbonaceous. 0- 10


Sand, brown, quartz, fine to coarse, subrounded to well-
rounded, carbonaceous. ____
Sand, brown, quartz, carbonaceous, fine to medium.
Sand, as above; peat; wood; amber. _
Sand, as above; abundant shells and fragments; carbonaceous
material; gray silty clay. _
Shell fragments and sand; quartz pebbles and black phosphate
pebbles, rounded and frosted. _____


10- 20
20- 35
35- 40

40- 50

50- 60


Hawthorn formation
Clay, gray, sandy, calcareous, phosphatic; quartz and phos-
phate pebbles, as above; a few shell fragments. 60- 70
Clay, gray-white, chalky, phosphatic, sandy in part. 70- 90
Clay, as above, with some gray impure limestone. __ 90-100
Clay, as above. ___ 100-110
No sample. ____ __ 110-120
Clay, white, chalky, sandy in part, phosphatic. 120-125
No sample. 125-130
Clay, white, chalky, sandy; gray-white sandy limestone, with
a few mollusk molds and casts. __ __ 130-140
Clay, greenish gray calcareous, sandy, phosphatic. 140-145
No sample. 145-150
Clay, as above but very sandy; much chert. 150-155
No sample. 155-160
Clay, gray-white calcareous, sandy, phosphatic; gray-white
sandy limestone; some chert. 160-165
Clay, greenish gray, calcareous, sandy, phosphatic; some chert. 165-170
Limestone, gray-white, impure, porous. -170-175
No sample. __ 175-180
Clay and limestone, with some chert. ___ 180-185
No sample. 185-210
Clay, gray-white, sandy, phosphatic; some chert. __ 210-215
Tampa formation
Limestone, white to cream, hard to soft, very sandy; some
chert. Archaias sp. and Sorites sp. 215-220
Limestone, creamy white, gray, and tan, soft to hard, granu-
lar, porous, granular to dense, sandy, fossiliferous; crys-
talline calcite. Archaias sp. and Sorites sp.-__ 220-230
Limestone, as above. 230-250





82 FLORIDA GEOLOGICAL SURVEY

Table 7. (Continued)
Lithology Depth Below
Land Surface
No sample. __ 250-270
Limestone, white to tan, granular to dense, sandy; some chert. __ 270-275
Limestone, buff and tan, soft to hard, dense to granular,
sandy; crystalline calcite in solution cavities. 275-285
No sample. --_ 285-300
Limestone, buff and tan, soft to hard, dense to granular, fossil-
iferous; contains numerous fragments of gastropod molds
and casts. 300-305
No sample. 305-310
Limestone, white to brown, soft to hard, chalky, porous,
sandy in part, fossiliferous. 310-315
No sample. 315-325
Limestone, as above; also dark brown, hard, porous. .__- 325-330
Limestone, as above, and some chert. 330-340
No sample. 340-345
Limestone, as above, Archaias sp. ___-345-350
Limestone, as above. 350-360
Limestone, as above, but no chert. 360-370
No sample. 370-380
Limestone, white, tan, and brown, granular to dense, porous,
dolomitic in part, fossiliferous; crystalline calcite and some
chert. ______ __ 380-385
No sample. 385-400
Sawannee limestone
Limestone, creamy white to white, soft, granular to chalky,
porous, fossiliferous, calcitic. _____400-410
Limestone, as above. Rotalia mexicana and other foraminifers. 410-420
Limestone, creamy white, soft, granular, calcitic, porous,
chalky matrix, fossiliferous, abundant molds, casts, spines,
and foraminifers. Rotalia mexicana. ____ 420-425
No sample. -_ 425-430
Limestone, as above. 430-460
No sample. 460-470
Limestone, buff and tan to white, fairly soft, porous, chalky;
brown crystalline dolomite; some chert. Rotalia mexicana,
Dictyoconus cookei and other foraminifers present. 470-475
No sample. 475-480
Limestone, as above. ____ 480-485
No sample. 485-490
Limestone, white to tan, granular, porous, dolomitic in part,
fossiliferous. Abundant Dictyoconus cookei, Coskinolina
floridana and Rotalia mexicana. ___ 490-500
Limestone, as above, and brown shaly, carbonaceous clay. 500-510'
Limestone, as above. 510-520
Limestone, white, soft, granular, porous, fossiliferous; hard
brown crystalline dolomite; Dictyoconus cookei and other
foraminifers poorly preserved. 520-525






REPORT OF INVESTIGATIONS NO. 21


Table 7. (Continued)
Lithology Depth Below
Land Surface

No sample. ____ __ ....__ ..... 525-530
Dolomite, brown, hard, crystalline. __-______ ____ 530-535
Dolomite, as above, with some soft granular porous fos-
siliferous limestone. Dictyoconus cookei and Coskinolina
floridana. ____...__ 535-550
No sample. ___..______ 550-560
Limestone, white, granular, soft to hard, porous to dense;
small amount of fossiliferous dolomite. Dictyoconus cookei
and Coskinolina floridana. _____ 560-565
No sample. ----------__......__....__ 565-575
Limestone, as above, but dolomite not present. 575-580
No sample. __ 580-600
Limestone, white, finely granular, soft, porous, fossiliferous;
abundant foraminifers, echinoid spines. 600-605
No sample. --. ____.___- ____ 605-615

Ocala group

Limestone, white, chalky, soft, finely granular, porous, fossi-
liferous. Lepidocyclina ocalana, L. floridana, Nummu-
lites sp., Gypsina globula, and other foraminifers. ----_ 615-642


Well 42-23-1

(Florida Geol. Survey No. W-2675)

Pleistocene and Pliocene

Soil and sand. ___ 0- 5
Sand, brown stained, quartz, fine to coarse. 5- 40
Clay, gray, calcareous, very sandy with phosphate; frosted
gray and brown, quartz grains and pebbles; fish teeth; pyrite. 40- 45
Clay, gray, very sandy, calcareous, phosphatic; coarse to fine
sand; frosted rounded quartz pebbles. ___45- 55

Hawthorn formation

Clay, gray-white, calcareous, chalky, sandy, phosphatic. --_-- 55- 70
Clay, as above, with some gray, sandy, impure limestone. --------- 70- 85
Clay, as above; limestone, white, hard, sandy, fossiliferous,
phosphatic. _-_ 85- 90
No sample. --------___ 90- 95
Clay, as above, with some impure limestone. 95-115
No sample. __ 115-125
Clay, gray-green to white, waxy to chalky, calcareous, sandy
in part; impure limestone with a few mollusk fragments;
phosphate and some chalcedony. -- 125-135






FLORIDA GEOLOGICAL SURVEY


Table 7. (Continued)
Lithology Depth Below
Land Surface
Tempa formation
Clay, olive green to gray, calcareous, sandy; gray, sandy
limestone; some crystalline calcite; chert and phosphate. .--- 135-145
Limestone, gray-white, fairly hard, sandy, dolomitic in part;
chert; a few mollusk fragments and foraminifers, Archaias
and Sorites. ______-__ 145-165
No sample. _.-- --- 165-170
Limestone, gray-white, fairly hard, sandy, porous in part,
fossiliferous, dolomitic in part; chert and pyrite. Archaias
and Sorites. _____--------__----------- 170-180
No sample. _180-185
Limestone, as above. ______ 185-195
No sample. 195-205
Limestone, as above. ______ 205-215
No sample. ____ 215-225
Limestone, gray-white, tan and brown, hard, dense, dolomitic
and crystalline in part, sandy, porous in part, fossiliferous;
crystalline calcite and chert; mollusks and foraminifers.
Archaias. _____-_----_-_---____ 225-235
No sample. 235-240
Limestone, as above. _____ 240-250
No sample. ___ __ 250-255
Limestone, gray-white to brown, fairly soft to hard, granular
to dense, porous, dolomitic in part, sandy in part; crystal-
line calcite and pyrite; mollusk molds and casts, foramini-
fers. Archaias. _______- 255-275
No sample. ---_ -- ----- ------- __-.... 5 275-300
Suwannee limestone
Limestone, white to buff, soft, granular to somewhat chalky,
very porous, fossiliferous; chert; echinoid spines and
plates, mollusk molds and casts, many small foraminifers.
Rotalia mexicana. -___ 300-310
No sample. 310-320
Limestone, as above. ___. -- ___320-345
No sample. 345-350
Limestone, as above, but more chalky and less porous. 350-360
No sample. 360-365
Limestone, as above. _____ 365-375

Well 42-25-3
(Florida Geol. Survey No. W-2796)
Pleistocene and Pliocene

Sand, white, fine to coarse. _____ 0- 10
Sand, brown, fine to coarse, carbonaceous, shells. ___ __ __ 10- 20






REPORT OF INVESTIGATIONS No. 21 85

Table 7. (Continued)
Lithology Depth Below
Land Surface
Sand, quartz and phosphate, fine to coarse. _- 20- 23

Hawthorn formation
Clay, gray-white, calcareous, chalky, phosphatic; few mollusk
molds and casts. ____- ___ 23- 25
Clay, white, chalky, sandy, calcareous, phosphatic; gray-white
impure sandy limestone; pyrite. ____ -----.... .__ -.. ..__ ...._. 25- 35
No sample. -_ --- __ __ _-._.____ 35- 45
Clay, gray-white, calcareous, sandy, phosphatic; gray impure
sandy fossiliferous limestone; pyrite; chert; mollusk molds
and casts. ____ 45- 50
No sample. __ 50- 60
Clay, white to gray, chalky, sandy; chert and phosphate. 60- 70
No sample. ___________ 70- 75
Clay, greenish gray, sticky, sandy, calcareous; phosphate
grains and pebbles; gray impure sandy limestone, oolitic
in part, phosphatic. --- 75- 85
No sample. -----_--______- _____ 85- 90
Clay, gray-white, chalky; phosphatic sand and pebbles; gray
hard impure limestone; phosphatic sand. ...___ 90-100
No sample. __ 100-110
Clay, gray-white, calcareous, very sandy; white to buff sandy
limestone; phosphate and pyrite. _____110-120
No sample. ____-._ 120-140
Clay, as above; gray to buff, hard, dense sandy limestone;
phosphate; chalcedony; dolomite. ........- .....-.........--___ ...__ 140-150
Clay, gray-green, calcareous, very sandy, phosphatic. -----_--_ 150-153

Tampa formation

Limestone, white, chalky, soft, fossiliferous, fairly porous.
Archaias. _- --____ _-__---_ 153-155
No sample. ---_ _____ 155-165
Limestone, gray-white, fairly hard, sandy, fossiliferous; chert. -_ 165-170
No sample. ---- __________ __ 170-175
Limestone, gray-white, hard, porous to dense, crystalline,
sandy; chert; mollusk fragments. Abundant Archaias
and Sorites. __ ___--- ._... ---- --.-._.____ 175-185
No sample. ____ 185-190
Limestone, gray to tan, hard, porous to dense, dolomitic in
part, sandy in part; gray and tan chert; crystalline cal-
cite; mollusks and foraminifers. Sorites. __ -__ 190-200
No sample. _____200-210
Limestone, gray-white to brown, granular, sandy, porous to
dense, hard, dolomitic, and crystalline in part, fossili-
ferous; chert. Archaias. ___ 210-245
No sample. __ _-_ ._ ._ 245-255






FLORIDA GEOLOGICAL SURVEY


Table 7. (Continued)
Lithology Depth Below
Land Surface
Limestone, as above. ___ 255-275
Limestone, gray-white to dark brown, soft to hard, granular,
porous to dense, fossiliferous, dolomitic, slightly sandy;
crystalline calcite, chert; mollusks and foraminifers. ..__-- 275-285
No sample. 285-290
Limestone, as above but no chert. ___ _------__ 290-300
Limestone, gray-white to brown, fairly soft to hard, granular,
porous to dense, fossiliferous, dolomitic in part, slightly
sandy; gray and brown chert; crystalline calcite. 300-305
No sample. ______ 305-310
Limestone, white and buff, fairly soft, granular, porous in
part, fossiliferous; crystalline calcite; chert; Sorites. ___ 310-315
No sample. --------- -- 315-320
Limestone, as above, but dolomitic in part. ...- 320-330
No sample. -------- ---.- 330-340
Su wannee limestone
Limestone, white, soft, granular to chalky, porous, fossilifer-
ous; crystalline calcite; mollusks, echinoid spines, fora-
minifers. _____________ 340-345
No sample. _345-365
Limestone, creamy white, soft, granular, porous, finely crystal-
line in part; crystalline calcite. Rotalia mexicana. __ ___ 365-375
No sample. __ __ 375-380
Limestone, as above. _______ 380-390
No sample. -- =- -___ 390-415
Limestone, creamy white to buff, soft, granular to chalky, por-
ous; fossils abundant but poorly preserved. Rotalia mexi-
cana, Dictyoconus cookei. ____ __ 415-425
No sample. __________425-435
Limestone, gray-tan, fairly hard, granular with a chalky
matrix, not very porous, fossiliferous as above. 435-445
No sample. 445-460
Limestone, gray-tan, soft, granular, porous, fossiliferous;
crystalline in part. Rotalia mexicana, Dictyoconus cookei. 460-470
No sample. -___ 470-480
Limestone, white, soft, granular, fossiliferous; dolomite, tan
and brown, hard, crystalline; chert. Rotalia mexicana,
Dietyoconus cookei, Coskinolina floridana._ -- -_ 480-490
Limestone, gray-tan, fairly hard, granular, impure, dolomitic
in part, fairly porous; chert. Rotalia mezicana, Dictyo-
conus cookei, Coskinolina floridana, Gypsina globula. Top
of Ocala group apparently in this interval. _---- 490-500
Ocala group
Limestone, gray-white to tan, granular, fairly porous, fossil-
ferous, dolomitic in part; chert; crystalline calcite. Gyp-
sina globula abundant. 500-510






REPORT OF INVESTIGATIONS NO. 21


Table 7. (Continued)
Lithology Depth Below
Land Surface

Limestone, gray-white to buff, fairly soft, granular to chalky,
porous, fossiliferous; chert and crystalline calcite. Gypsina
globula, Nummulites sp., Operculinoides sp., Heteroste-
gina ocalana. _________ 510-520
Limestone, predominantly a coquina of mollusk fragments
and poorly preserved foraminifers in a finely granular to
chalky matrix. Nummulites sp., Gypsina globula, Lepi-
docyclina ocalana. __ _____ 520-550

Well 45-25-8

(Florida Geol. Survey No. W-2546)

No sample. _--_ 0- 30
Hawthorn formation
Clay, white, chalky, sandy, calcareous, phosphatic. ------ 30- 35
Limestone, gray-white, dense, sandy with chert; pyrite; phosphate. 35- 40
Clay, light green, waxy, sandy, calcareous, phosphatic; some chert. 40- 50
As above. ___________ 50- 65
Clay, as above; limestone, white, dense, sandy; some chert and
a few mollusk fragments. -- 65- 85
As above. __---------- -- 85- 95
Tampa formation
Limestone, gray-white, hard, dense, sandy, fossiliferous;
crystalline calcite in solution cavities; dolomite, gray-tan,
hard, dense, crystalline. ---- --- ---- 95-100
No sample. __ -- 100-110
Limestone, white and gray, hard, sandy; chert fragments;
mollusk molds and casts. ___ 110-120
Limestone, white and gray, granular, porous, chalky, sandy in
part; chert; mollusk molds and casts. Archaias and other
foraminifers. ____-120-130
Limestone, as above but more porous. Sorites, abundant Archaias. 130-140
No sample. _-___ ---- 140-150
Limestone, white, gray, and tan, fairly hard, dense to porous,
sandy in part, fossiliferous; chert. _--------- 150-160
No sample. 160-170
Limestone, white to tan, fairly hard, dense, sandy in part;
chert; pyrite and crystalline calcite. 170-180
No sample. -__-__ 180-200
Limestone, as above, but dolomitic in part. ------ 200-210
No sample. 210-240
Limestone, white to tan, fairly hard, dense to granular, por-
ous; contains a few foraminifers. --- 240-250
No sample. --- ___-__ ----250-270






88 FLORIDA GEOLOGICAL SURVEY

Table 7. (Continued)
Lithology Depth Below
Land Surface
Suwannee limestone

Limestone, white, chalky, granular, porous; abundant small
foraminifers and echinoid fragments. 270-275
Limestone, creamy white to tan, soft, granular, porous,
fossiliferous. 275-285
No sample. 285-315
Limestone, as above. ______315-325
No sample. 325-340
Limestone, as above. Rotalia mexicana and Dictyoconus
cookei. ______ __ ______ 34 340-350
As above. ____- ___350-365
No sample. 365-415
Limestone, buff and tan, soft, granular, porous, fossiliferous.
Dictyoconus cookei. ___ __ 415-425

Well 42-27-6

(Florida Geol. Survey No. W-2674)

Pleistocene and Pliocene

Sand and shells. ________ 0- 38

Hawthorn formation

Clay, gray, calcareous, sandy, phosphatic. ________ 38- 45
No sample. __________________._______ --__ 45-140
Clay, gray, sandy, calcareous, waxy in part; phosphate grains
and pebbles; chert. _____________ __ -___ 140-165

Tampa formation

Limestone, white, gray, buff and tan, fairly soft, granular,
fossiliferous; chert; Sorites. _.___ 165-170
Limestone, gray-white to buff, soft, granular, porous, sandy;
chert; crystalline calcite in solution cavities; mollusk
fragments, small foraminifers. Sorites. _______ ___ 170-175
No sample. 175-210

Well 43-26-4

(Florida Geol. Survey No. W-2414)
Pleistocene and Pliocene

Sand. _______ 0- 5
Sand and shells. 5- 15
Sand, shells, clay, gray, calcareous, sandy, phosphatic. ._....... 15- 20






REPORT OF INVESTIGATIONS NO. 21 89

Table 7. (Continued)

Lithology Depth Below
Land Surface

Hawthorn formation

Clay, gray, sandy, calcareous, phosphatic. __ 20- 40
Clay, gray-green, white, calcareous, sandy, phosphate grains
and pebbles; large quartz grains. ---.. ..._ ..-_ --. ..-__..... ----- 40- 50
Clay, gray-white, calcareous, sandy, phosphatic; white to tan,
impure, sandy limestone; chert. ___ __ ___ __ 50- 60
Clay, as above, with pyrite fragments. ------__- _... .------- 60- 80
Clay, as above, with some impure limestone and chert. _...- 80- 85
Clay, blue-gray, calcareous, sandy; phosphate and chert. _... 85-100
Clay, white to blue-gray, chalky, sandy; phosphate and chert. -----. 100-110
Clay, white to green, chalky, shaly, sandy, calcareous; phos-
phate and chert. --... ___L___ ..........--_.....-.. .... ._.. 110-115
Clay, green, calcareous, very sandy; phosphate and chert. --___.. 115-125
Clay, green, calcareous, shaly, slightly sandy; phosphate and
chert. ..- ------- -_______125-130
No sample. ---------------- ..-____ ___ ______. 130-135

Tampa formation

Limestone, white to tan, fairly hard, granular to dense, por-
ous, sandy in part, fossiliferous; chert; mollusks and
foraminifers. Archaias and Sorites. -----------______. ........ 135-140
Limestone, white to dark gray, hard, very sandy, crystalline
calcite in solution cavities; chert; few mollusk molds and
casts. Archaias and Sorites. --_----------...---------- ...._.._..__ 140-170
Limestone, white, chalky, granular, slightly sandy in part,
porous; crystalline calcite in cavities; mollusk fragments.
Archaias and Sorites. -___ -_ -----------_-----.-- .--..---- .... .. 170-180
No sample. .-- -----------.-----.--. -----....-.. --- .. ---- -- ......... 180-190
Limestone, as above. --_-----____- 190-195
Limestone, gray-white, granular to tan, hard, dense, sandy;
crystalline calcite; chert. Archaias and Sorites. _____ --. ... 195-220
Limestone, tan to dark gray, very hard, dense, slightly sandy
in part, dolomitic; chert. -..-.___--___-- ___ ____......... 220-235
Limestone, gray-white, fairly hard, sandy, chalky; crystalline
calcite in solution cavities; mollusk molds and casts. ---__. ... 235-240
No sample. _____ .._-_______-_. 240-250
Limestone, white, gray, and tan, hard, dense, sandy; chert
and crystalline calcite. --- __-- -- _- _- ------ -- 250-265
No sample. ---------------------------- --. .-... 265-275
Limestone, as above. _-------------------- --------- 275-280
Limestone, white, soft, granular, chalky, sandy; crystalline
calcite; mollusk molds and echinoid spines. ______ --...- _-. 280-290
Limestone, buff, fairly soft, granular, slightly sandy, crystal-
line in part; chert and calcite. __- _______. 290-295
No sample. ------------------------ -----_-. 295-300





90 FLORIDA GEOLOGICAL SURVEY

Table 7. (Continued)
Lithology Depth Below
Land Surface

Limestone, gray-white, tan, and brown, hard, dense, dolomitic,
slightly sandy. -..---. -.......... ---.-.......-....---. ............--..... 300-305
Limestone, gray-white, tan, soft to hard, granular to dense,
dolomitic in part; chert and calcite; mollusk fragments ..---....-. 305-315
No sample. .------.. --------.--------.- ----................... 315-325
Suwannee limestone
Limestone, creamy white, buff, and tan, soft, granular,
porous fossiliferous; chert and calcite. --...--...-----.........-- .---......----. 325-345
Limestone, as above, somewhat harder. Rotalia mexicana. .-..-....- 345-355
Limestone, white, soft, granular, somewhat chalky, fairly por-
ous; mollusks, echinoids and foraminifers. Rotalia mexicana. .. 355-435
Limestone, white to tan, soft, granular, somewhat chalky, not
very porous, fossiliferous; crystalline calcite. Rotalia mexi-
cana and Dictyoconus cookei. ...-----.....................-----....---------- 435-455
Limestone, white to tan, soft to hard, granular to dense, fos-
siliferous. Rotalia mexicana, Dictyoconus cookei, Coskino-
lina floridana. -_- -------;__-.. -- ---....---------..------- .. 455-465
Limestone, tan, gray, and brown, soft to hard, granular to
dense, crystalline in part, fossilferous. Dictyoconus cookei,
and Coakinolina floridana. ...........--- .........---------------- .....--- 465-475
Limestone, gray-brown, fairly soft, granular, crystalline in
part, fossiliferous. Dictyoconus cookei and Coskinolina
ftoridana. ..---..---..........--....... ------...... --...........- .....- 475-510

Well 46-23-5
(Florida Geol. Survey No. W-2668)
Pleistocene and Pliocene
No sample. ---------------- --------....-..................... -- ---0- 20
Sand, gray-brown, fine to coarse, rounded, carbonaceous. .--.------ 20- 27
Hawthorn formation
Clay, gray, waxy, sandy in part, calcareous, phosphatic. .-......---- .. 27- 30
Clay, gray, calcareous, sandy, phosphatic ....---.............. -----............- 30- 40
Clay, as above; limestone, gray-white, sandy, chalky, impure;
chert and phosphate. ..... ---- ------.----...--............--- 40- 70
Clay, gray-green, waxy, calcareous, sandy in part; chert and
phosphate. .---- ..... --.....--..................-...- -.......-.... 70- 80

Tampa formation
Limestone, dark gray to brown, hard, sandy, silicified in part,
dolomitic in part. --........---......-------......--...................--......... 80-100
Limestone, gray-white, fairly hard, sandy, porous, fossilifer-
ous; dolomite, brown, crystalline; chert. Archaias and Sorites. .. 100-120






REPORT OF INVESTIGATIONS NO. 21


Table 7. (Continued)
Lithology Depth Below
Land Surface

Limestone, white, soft, chalky, slightly sandy, granular por-
ous; gray-brown hard, dense, splintery, sandy limestone;
brown crystalline dolomite. Archaias and Soritcs. .....-.......... -120-130
Limestone, gray-white, sandy, hard, porous to dense; dolomite,
as above; chert and a few poorly preserved fossils. ..-....-...... 130-140
Limestone, gray-white to tan, fairly soft, chalky; hard dense,
porous in part, sandy, fossiliferous limestone; dolomite,
as above, and some chert. Sorites and other foraminifers. ..- 140-150
Limestone, gray to tan, hard, sandy; gray-brown hard, crys-
talline dolomite; chert .------..... ............--............---- ----....... 150-170
Limestone, gray-white, tan, fairly hard, sandy, dolomitic,
fossiliferous; chert. Sorites. ....--..-.... -.....-.... ............ ---. 170-180
Limestone, white, gray and brown, hard, sandy; gray-brown
hard crystalline dolomite, porous in part. -..---.....-..---- ..--------- 180-200
Limestone, gray-white, tan, brown, hard, dense, sandy in
part, dolomitic in part; chert; few poorly preserved fossils. 200-220
Limestone, white, soft, granular, porous, fossiliferous; dolo-
mite, gray-brown; echinoid spines. Archaias. ...-...--.....-.. ...--- 220-230
Limestone, as above, also gray-brown, sandy, dolomitic. Sorites. .-.. 230-250
Limestone, creamy white, buff, and tan, soft, granular, fos-
siliferous ..-........ ...- ........ .............. .. ........ ....- .... .-..- ..- 250-260

Well 46-23-8

(Florida Geol. Survey No. W-2671)

No sample. ------......----........--....--..-------- --. .------ -- 0- 30
Hawthorn formation
Clay, gray-white, calcareous, sandy; phosphate grains and
pebbles, interbedded with gray hard sandy, fossiliferous
limestone ....---------------.. .. -- ---------.----- .........------------ 30- 55
Tampa formation
Limestone, gray to white, fairly soft to hard, granular, porous
to dense, sandy; brown dolomite; chert; mollusk frag-
ments and foraminifers. Sorites. -..-......----... -------..------------........ 55- 70
Limestone, gray-brown, hard, dense, sandy, dolomitic in part,
porous in part, fossiliferous; chert. Sorites. ----.......--------------.... 70-100
Limestone, white, soft, granular, having chalky matrix, por-
ous, fossiliferous; much chert. Sorites, Archaias. .----......-.......... 100-110
Limestone, gray, white, tan, fairly soft, porous, sandy; chert;
mollusks, echinoids, foraminifers. .-......--- ....-- ..-....... ----------....... 110-120
No sample. ...---...--.... -------.....................-------------------...... ..... 120-130
Limestone, gray-white, tan, hard, dense, sandy to soft, chalky,
porous; chert; mollusks, milliolids. Sorites .--...............----....-..... 1.30-140






92 FLORIDA GEOLOGICAL SURVEY

Table 7. (Continued)
Lithology Depth Below
Land Surface

Limestone, gray-white, tan, fairly hard, dense, porous in part,
sandy in part, dolomitic in part; chert. Archaias. --...----.... ..----.. 140-150
No sample. --._-- ....-------.---..-- -------------- ..-. ------..-- 150-160
Limestone, as above. __ ---_ ------...---.----.. -----.............. ...... 160-170
Limestone, gray-brown, hard, sandy, dolomitic, fossiliferous;
chert; mollusks and echinoid spines. --_-----_......-.... --................ 170-180
Limestone, white, soft, chalky; brown hard dolomite contain-
ing much sand. ---__----------.-- .._..----- ..................................--- -...--- 180-190
No sample. _-----------------____.__..-----......... 190-200
Limestone, gray-brown, hard to soft, dense, chalky, fossilifer-
ous in part; chert. --_ -__ ------.--- --- --...- .......... 200-205
No sample. -----..--------------.....-----....... ----............. 205-210
Limestone, gray-white and tan, fairly soft, granular, sandy in
part, dolomitic in part; chert; fossils poorly preserved .............. 210-220
No sample. --- --- ----. -- -- ---- 220-230
Limestone, gray-brown, hard, dense, crystalline in part,
chalky and porous in part, dolomitic in part, fossiliferous. ...-.... 230-255
No sample. --------------------_------------- --............. .. ............... 255-260
Suwannee limestone
Limestone, creamy white, soft, granular, porous, fossiliferous;
echinoid spines and plates, mollusk fragments, abundant
foraminifers. Rotalia mexicana .-...-...............----............... ............. 260-300

Well 46-24-10
(Florida Geol. Survey No. W-2321)

No sample. ----- --------- ---- ------ --.........-..-.....-..-....-.... --.... --.............. 0-180
Tampa formation
Limestone, white, chalky, sandy, porous; brown hard dense,
dolomitic, fossiliferous limestone; chert; mollusks and
foraminifers. Archaias and Sorites .....-.........----......-...................... 180-200
No sample. --_-- ----------------------- --.-.. ---------......- ---.. ....-. 200-210
Limestone, white, buff, and tan, chalky, granular, porous; hard
dense, very sandy limestone. ---- ---------- ---....................... 210-230
No sample. ..-------------------- --------.............. ---....... 230-240
Limestone, white, tan, and brown, soft to hard, granular,
porous to dense, fossiliferous; chert; abundant small
foraminifers. Archaias. ---.----..........------------------. ............... 240-245
As above, with pyrite fragments. .__ ..._.. ............ .......... 245-265
No sample.' ------------------ --------.......................... 265-285
Suwannee limestone
Limestone, creamy white to buff, soft, granular, porous,
foraminiferal; mollusks, echinoids, milliolids, and other
small foraminifers abundant but poorly preserved. .....---.....-- .. 285-300






REPORT OF INVESTIGATIONS NO. 21


Table 7. (Continued)
Lithology Depth Below
Land Surface

Limestone, as above, crystalline in part, somewhat chalky;
Rotalia mexicana. .--..-----..-----..----....--...---............................. ... 300-365
No sample ........-------------.................--.--.............--------.............-------------...................-...-.....-......-........ 365-375
Limestone, as above ..-........-..-..--.... ---..---........ ...-........-..- ....... 375-380
No sample ....-----..........--..---------....... .....---..----------... .. ----... .........------ 380-390
Limestone, gray-white to tan, fairly soft, granular; lime-
stone, fairly hard, dense, crystalline, porous in part,
fossiliferous; some chert. Rotalia mexicana, Dictyoconus
cookei, and Coskinolina floridana ............ ..........-..---------- ..-- .. 390-400
Limestone, as above, but no chert. .--..---..---..........-----....-....--.. ......... 400-410
Limestone, as above, with pyrite and chalcedony. -...-..-........-..-...---.... 410-420
Limestone, creamy white, soft, granular, porous, fossiliferous,
with some carbonaceous material. Rotalia mexicana,
Dictyoconus cookei, Coskinolina floridana .-..----.........-.........-...--- 420-435
Limestone, gray-brown, hard, dense, crystalline in part,
fossiliferous; abundant milliolids, poorly preserved. ...........----. 435-450
Limestone, gray-brown, fairly soft to hard, granular, porous
to dense, crystalline in part; mollusks and foraminifers. .......-.... 450-460
No sample. .......-................---------------.------.---- ..---------------------.---- 460-470
Limestone, as above. Coskinolina floridana and Dictyoconus
cookei; white, buff and tan soft granular fossiliferous
limestone. Gypsina globula. Top of Ocala group in this interval. 470-480

Well 47-23-1
(Florida Geol. Survey No. W-2670)

Pleistocene and Pliocene
Sand and shells. .---......-....--...--.------V---------------------- -----..------.- 0- 25
Hawthorn formation:
Clay, gray, sandy, calcareous, phosphatic; sandy hard
phosphatic limestone; a few mollusk molds and casts. ....---........ 25- 30
No sample. ....------......-.------------------------------- --------------....... 30- 50
Clay, greenish gray, waxy, calcareous, sandy, phosphatic. ............. 50- 60
Clay, gray-white, chalky. ---------....................---- --..--........-... 60- 65
Tampa formation:
Limestone, gray-white to tan, fairly hard, dense, sandy; chert,
pyrite, and a few fragments of mollusk molds and casts. .-..-...--- 65- 70
Limestone, gray-white, very sandy, fairly hard, with very
fine black phosphate grains; chert. Sorites sp. and other
fossils. .......----.--.------------------------------------ ----------------- ---... 70- 80
Limestone, white to buff, soft, chalky to granular, porous,
sandy in part, some chert, fossiliferous.. Specimens of
Archaias and Sorites fairly abundant .........----. -------................. 80- 90





94 FLORIDA GEOLOGICAL SURVEY

Table 7. (Continued)

Lithology Depth Below
Land Surface

Limestone, as above. --.. .....-- --.................. .................................... 90-100
Limestone, gray-white, fairly soft, granular, porous in part;
very sandy, hard limestone, dense in part; chert; fossili-
ferous, as above, including specimens of Archaias and Sorites. 100-110
Limestone, gray to white, soft to hard, dense to porous; sandy,
dolomitic in part; chert; fossiliferous, as above. ......--.................. 110-120
Limestone, gray to tan, fairly hard, dense, sandy; mollusk
molds and casts and foraminifers. --..-----..-..-...........-- ................-- 120-130
Limestone, as above. ----------------------------......... .. ......................... 130-140
No sample ------.......-........................ ....-..-. .....--.........----.......--.... .... 140-150
Limestone, gray to tan and brown, hard, dense, sandy,
dolomitic in part. ............. ........................................................... .. 150-165
Limestone, as above, but more dolomitic; a few fossil molds
and casts. ...--. ..----- ---.. ----.... --...-.......................... ............ 165-175
Limestone, gray, white, and tan, fairly hard, dense to granu-
lar, porous, dolomitic in part; some poorly preserved
foraminifers and other fossils. -.---------------.....-........--------.............. 180-200
Limestone, white to tan, soft, granular to chalky, porous;
milliolids, echinoid plates and spines abundant. .--....----...........---. 200-220
Limestone, gray to tan, fairly hard, dense to granular and
porous, fossiliferous as above. ----------.. ...... ........-...- -................. 220-230

Suwannee limestone

Limestone, creamy white, soft, granular, porous; small
amount of chert; foraminifers abundant but poorly preserved. 230-250
Limestone, creamy white, soft, granular, porous, chalky,
fossiliferous. Rotalia mexicana fairly abundant. .......................... 250-290
No sample. .....--.....-...-- ...... -- ------ -.................. .......................... 290-330
Limestone, gray-tan, fairly soft, granular, porous, fossilifer-
ous. Dictyoconus cookei, Coskinolina floridana ............................. 330-340

Well 51-23-2

(Florida Geol. Survey No. W-2411)

Pleistocene and Pliocene

Sand, quartz, medium to coarse, carbonaceous material, shell
fragments. --... ..---.------........--...... ----........................ ......-.........-- .....-.. 0- 5

Hawthorn formation

Clay, gray to brownish, sandy, calcareous; phosphate grains
and pebbles. .-.....- .............. --- ---..- -......-......................-................ 5- 20
Clay, gray, sandy, calcareous; gray-white hard sandy, argil-
laceous limestone; chert and phosphate grains and pebbles ...... 20- 38






REPORT OF INVESTIGATIONS No. 21 95

Table 7. (Continued)
Lithology Depth Below
Land Surface
Tampa formation
Limestone, white, fairly soft, chalky, sandy; chert and calcite. -...... 38- 45
Limestone, white, soft, chalky, slightly sandy; chert and
calcite; few foraminifers. Sorites. .......--..--..------.-----.......--.. 45- 50
SLimestone, as above, with mollusk fragments ........-.......------------....--. 50- 55
Limestone, as above, with very little sand; chert and calcite.
Sorites and Archaias. ....--...-------.....----------..................-- ..-..---- .. 5-5- 60
Limestone, gray-white to tan, fairly hard, sandy; calcite;
mollusk molds and casts. Sorites, Archaias and other
foraminifers. ...................-- .............................-- ..---.. .----- .. 60- 80
Limestone, gray-white to tan, hard, dense, sandy; abundant
mollusk fragments. Sorites. -....................----- ..---- ..--- -.......--- ..- 80- 85
Limestone, gray-white, fairly soft, slightly sandy; gray and
tan, hard dense impure limestone. Archaias. -..-...-......---....---- .. -- 85- 90
Limestone, as above, with some chert and a few fossils ....-..-........ -- 90- 95
Limestone, gray-white to tan, hard, dense, impure; very little
sand; chert. ....--....-.............------ ----.---.----- ---- ..-------. 95-100
SnwaCnc limestone
Limestone, creamy white to buff, soft, granular, porous,
crystalline in part, having a chalky matrix; chert;
mollusks, abundant echinoid spines. Rotalia mexicana and
other foraminifers --.......--...................------ ..--..-...-------------.... ..... 100-145
Limestone, creamy white to buff, soft, granular, porous,
crystalline in part, fossiliferous; foraminifers abundant
but poorly preserved. .....-...-.........---.........----- .........-....... ... ------ 145-160
Limestone, as above, with chert fragments. ...-...................-- ............... 160-175
Limestone, creamy white to buff, soft, granular, porous,
crystalline in part; abundant mollusk fragments, echinoid
spines, and foraminifers ----...........-- -.....--.........-----.........-.....- ... 175-210
Limestone, gray-white to tan, soft, granular, porous, crystal-
line in part, fossiliferous; few poorly preserved Dictyo-
conus cookei. .............. ................... ..... ............ .... ...... ------ 210-215
Limestone, as above, with some chert. Dictyoconus cookei and
Coskinolina floridana. --------------........... .........---------..-.--.. 215-220
Limestone, as above, but no chert. ........--.... .............-...---......... 220-225
Limestone, gray, white, and tan, soft to hard, granular to
dense, fossiliferous; mollusks, echinoids, foraminifers.
Dictyoconus cookci and Coskinolina floridana. --....----..............---- .. 225-260
Limestone, as above, with some chert; no Dictyoconus or
Coskinolina noted. .--...--..-..----...........--. ------..............--..-...... 260-270
No sample. .......-...----- ......-- ...........-----...... ............ -- ------ ---- 270-275
Limestone, gray-white to tan, fairly soft, granular, porous,
fossiliferous; chert -......--......-------..........-----------------------..... 275-290
Limestone, white, buff, and tan, granular, chalky to dense,
fossiliferous, granular cemented with calcite paste; po-
rosity probably low; some crystalline calcite and chert. ..-.......... 290-300




FLORIDA GEOLOGICAL SURVEY


Table 7. (Continued)
Lithology Depth Below
Land Surface

Limestone, buff and tan, granular, with a chalky calcite
matrix; dolomitic in part, fossiliferous. ..................................... 300-325
Limestone, as above. Rotalia mexicana, Dictyoconus cookei,
and Coakinolina floridana. ....................................................... 825-380

Ocala group
Limestone, creamy white, buff and tan, soft, granular, porous,
foraminiferal with a chalky matrix. Gypsina globula,
Lepidocyclina floridanus, L. ocalana. ........................................ 830-400
Limestone, buff and tan, coquinoid, with fine granular matrix,
porous. Gypsina globula, Lepidocyclina, Camerina. .................. 400-450
Limestone, creamy white to tan, coquinoid, with a chalky
matrix; foraminifers include Gypsina globula, Lepidocy-
clina ocalana, Operculinoides sp., Heterostegina ocalana. ............ 450-500
Limestone, creamy white to buff, soft, granular, porous,
crystalline in part, fossiliferous; a few larger foramini-
fers and mollusks. Gypsina globula, Operculinoides sp.,
Nummnulites sp. .......-.... .. ......... .....-............................... 500-520
Limestone, creamy white to buff, granular, fossiliferous;
chert and limonite; foraminifers poorly preserved. .................. 520-585
Limestone, creamy white to buff, soft, chalky, granular,
fossiliferous, echinoid spines. Operculinoides sp., Nummu-
lites sp. ---..... .......-- ........- ........ ....... .......................... 535-555
Limestone, white, buff, and gray, soft, granular, fossiliferous;
abundant echinoid spines. ................... ................... ................ 555-570
Limestone, creamy white to buff, soft, very fine, granular,
less fossiliferous than above. .................. -....-- ................... 570-575
A von Park limestone
Limestone, white, buff, and tan, soft, granular, chalky; lime-
stone, hard, dense, crystalline, fossiliferous. Dictyoconus cookei. 575-585
Limestone, white, buff, and tan, soft, granular, chalky,
fossiliferous. Dictyoconus cookei. ........................ ...... 585-610
No sample. --...-..............-......... ................................ 610-670
Dolomite, brown, hard, crystalline, lignitic, and limonitic;
white to brown granular to dense limestone; crystalline
calcite in abundant solution cavities. ...................... ............. 670-780
No sample ................................. ...-. ............... ................... 780-765
Dolomite, as above; tan to brown dolomitic crystalline limestone. .. 765-775
No sample. .............. ...................................................... ... ............ 775-785
Dolomite and limestone, as above. ....-.... ....... ...... ........... 785-795
No sample. .... .. ......--- ............ .......................... 795-805
Dolomite, medium to dark brown, hard, crystalline, porous;
brown hard crystalline dolomitic limestone; crystalline
calcite in solution cavities. ................................................... 805-850




,~lt~


i




The artesian water of the Ruskin area of Hillsborough County, Florida ( FGS: Report of investigations 21 )
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 Material Information
Title: The artesian water of the Ruskin area of Hillsborough County, Florida ( FGS: Report of investigations 21 )
Series Title: ( FGS: Report of investigations 21 )
Physical Description: 96 p. : illus., maps (1 fold.) ; 23 cm.
Language: English
Creator: Peek, Harry M ( Harry Miles ), 1923-
Publisher: s.n.
Place of Publication: Tallahassee
Publication Date: 1959
 Subjects
Subjects / Keywords: Artesian wells -- Hillsborough Co., Fla   ( lcsh )
Genre: non-fiction   ( marcgt )
 Notes
Statement of Responsibility: Prepared by the U. S. Geological Survey in cooperation with the Florida Geological Survey and the Board of County Commissioners of Hillsborough County.
General Note: At head of title: State of Florida State Board of Conservation.
General Note: "References": p. 72-74.
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Table of Contents
    Front Cover
        Page i
    Copyright
        Copyright
    Florida State Board of Conservation
        Page ii
    Transmittal letter
        Page iii
        Page iv
    Table of contents
        Page v
        Page vi
        Page vii
        Page viii
    Abstract
        Page 1
        Page 2
    Introduction
        Page 2
        Page 3
        Page 4
        4a
        Page 5
        Page 6
    Geography
        Page 7
        Page 8
        Page 9
        Page 10
        Page 11
    Geology
        Page 12
        Page 13
        Page 14
        Page 11
        Page 15
        Page 16
        Page 17
        Page 18
        Page 19
        Page 20
        Page 21
        Page 22
        Page 23
        Page 24
        Page 25
        Page 26
        Page 27
        Page 28
        Page 29
        Page 30
        Page 31
        Page 32
        Page 33
        Page 34
        Page 35
        Page 36
        Page 37
        Page 38
        Page 39
        Page 40
        Page 41
        Page 42
        Page 43
        Page 44
        Page 45
        Page 46
        Page 47
        Page 48
        Page 49
        Page 50
        Page 51
        Page 52
        Page 53
        Page 54
        Page 55
        Page 56
        Page 57
        Page 58
        Page 59
        Page 60
        Page 61
        Page 62
        Page 63
        Page 64
        Page 65
        Page 66
        Page 67
        Page 68
        Page 69
        Page 70
    Summary and conclusions
        Page 71
        Page 72
        Page 70
    References
        Page 73
        Page 72
        Page 74
    Table 6. Measurements of water levels in wells
        Page 75
        Page 76
        Page 77
        Page 78
        Page 79
        Page 80
    Table 7. Logs of selected wells...
        Page 81
        Page 82
        Page 83
        Page 84
        Page 85
        Page 86
        Page 87
        Page 88
        Page 89
        Page 90
        Page 91
        Page 92
        Page 93
        Page 94
        Page 95
        Page 96
Full Text


^ STATE OF FLORIDA
STATE BOARD OF CONSERVATION
Ernest MittsiDirector


FLORIDA GEOLOGICAL SURVEY
Robert 0. Vernon, Director







REPORT OF INVESTIGATIONS NO. 21





THE ARTESIAN WATER OF THE R.USKIN AREA

OF HILLSBOROUGH COUNTY, FLORIDA


By
HARRY M. PEEK
U. S. Geological Survey





Prepared by the
UNITED STATES GEOLOGICAL SURVEY
in cooperation with the
FLORIDA GEOLOGICAL SURVEY
and the
BOARD OF COUNTY COMMISSIONERS OF HILLSBOROUGH COUNTY


TALLAHASSEE, FLORIDA
1959










FLRD GEOLIOWC( ICA SURflViEWY~


COPYRIGHT NOTICE
[year of publication as printed] Florida Geological Survey [source text]


The Florida Geological Survey holds all rights to the source text of
this electronic resource on behalf of the State of Florida. The
Florida Geological Survey shall be considered the copyright holder
for the text of this publication.

Under the Statutes of the State of Florida (FS 257.05; 257.105, and
377.075), the Florida Geologic Survey (Tallahassee, FL), publisher of
the Florida Geologic Survey, as a division of state government,
makes its documents public (i.e., published) and extends to the
state's official agencies and libraries, including the University of
Florida's Smathers Libraries, rights of reproduction.

The Florida Geological Survey has made its publications available to
the University of Florida, on behalf of the State University System of
Florida, for the purpose of digitization and Internet distribution.

The Florida Geological Survey reserves all rights to its publications.
All uses, excluding those made under "fair use" provisions of U.S.
copyright legislation (U.S. Code, Title 17, Section 107), are
restricted. Contact the Florida Geological Survey for additional
information and permissions.









AGRI-

FLORIDA STATE BOA ^tL'

OF

CONSERVATION




LeROY COLLINS
Governor


R. A. GRAY
Secretary of State



J. EDWIN LARSON
Treasurer



THOMAS D. BAILEY
Superintendent of Public Instruction


RICHARD ERVIN
Attorney General



RAY E. GREEN
Comptroller



NATHAN MAYO
Commissioner of Agriculture


ERNEST MITTS
Director of Conservation








LETTER OF TRANSMITTAL


Jlorida geological Surveyj

Callakassee

September 9, 1959

MR. ERNEST MITTS, Director
FLORIDA STATE BOARD OF CONSERVATION
TALLAHASSEE, FLORIDA


DEAR MR. MITTS:


The Florida Geological Survey will publish as their Report of
Investigations No. 21 a comprehensive study of THE ARTESIAN
WATER OF THE RUSKIN AREA OF HILLSBOROUGH
COUNTY. This study was made by Mr. Harry M. Peek, Geologist
with the U. S. Geological Survey, in cooperation the Florida Geo-
logical Survey and with the Board of County Commissioners of
Hillsborough County.

The area in the vicinity of Ruskin is used extensively for truck
farming. During drought periods, considerable difficulty has been
experienced through the -accumulation of salts in low places, the
salts having been derived from water used for irrigation. This
study provides data that will be helpful in evaluating the problem
of salt accumulation in soils and will provide the necessary help
for a wise and conservative utilization of our water resources in
that area.
Respectfully yours,
ROBERT 0. VERNON, Director





















































Completed manuscript received
May 18, 1959
Published by the Florida Geological Survey
E. 0. Painter Printing Company
DeLand, Florida
September 9, 1959


iv










TABLE OF CONTENTS



Page
Abstract ..--..-------------------------------- ------------------ 1
Introduction ---------------..... -- --.-- 2
Purpose and scope of the investigation ------ 3
Previous investigations ------- --------4--------------- --4
Acknowledgments ------------ 5
Well-numbering system ------------------___-___.------- 5
Geography .... .-------------- -----------7-----.------- 7
Climate .----------------------. --------- --- 7
Physiography ------------------ 7
Culture ------------------------ 1--------------10
Geology ------ ------.---.----.- ------ 11
Eocene series ----------------------- ---------- --- 13
Avon Park limestone ---------13
Ocala group --------------- --------------.- --- 13
Oligocene series ------------------__------------------- 15
Suwannee limestone -------- ---------- -- 15
Miocene series ------------------------ 15
Tampa formation ...-----------------------------------------15
Hawthorn formation ..------------------------ --------- 18
Pliocene and Pleistocene series ----- _---------------------- 18
Ground water ---_ ------- -------- 19
Principles of occurrence -----------------.---- 19
Ground water in Florida --_---------------------- .----- 20
Artesian water -------- ---- ------ -----20
Piezometric surface -------.-21
Ground water in the Ruskin area --------------------.-.----- 21
Artesian water ....-----...._-------.-..._---- -----23
Current-meter exploration -------- 23
Fluctuation of artesian pressure head ---------_------ 23
Piezometric surface ----------- -------- ------ -- 36
Depth of water levels below land surface ------ 40
Wells ..----. ----------.-------- ------------ 44
Temperature ---------- -..---------- ----- ------- -----.------ 46
Quantitative studies ----------- --------- 47
Quality of water ----- .- ----- 54
Salt-water contamination --- -------------- ------- 64
Relative salinity of the artesian water .--------- 65
Sources of contamination --- --.--. ._----...---- 69
Summary and conclusions ----------------- 70
References ..---... ----....------. ------- --- 72
Water-level measurements --------- ------------- --- 75
Well logs ____-- --- ------ 81







ILLUSTRATIONS


P


Plate


1 Map of the Ruskin area showing location of wells ..... ... facing
Figure
1 Map of the peninsula of Florida showing location of Hillsborough
County and the Ruskin area
2 Precipitation and temperature at Tampa --.......-----------
3 Map of the Ruskin area showing the Pleistocene terraces ------
4 Geologic cross sections showing the formations penetrated by water
wells in the Ruskin area _---- ..... -- ----... ---------....
5 Map of the Ruskin area showing the configuration and altitude'
of the top of the Suwannee limestone ....-- ------ -- --.----
6 Map of the Ruskin area showing the configuration and altitude
of the top of the Tampa formation .- .....----------. --- -
7 Map of peninsular Florida showing the piezometric surface of the
Floridan aquifer in 1949 -----.........- ....--------


Graph showing well-exploration data for well
Graph showing well-exploration data for well
Graph showing well-exploration data for well
Graph showing well-exploration data for well
Graph showing well-exploration data for well
Graph showing well-exploration data for well
Graph showing well-exploration data for well
Graph showing well-exploration data for well
Graph showing well-exploration data for well
Graph showing well-exploration data for well
Graph showing well-exploration data for well
Graph showing well-exploration data for well
Graph showing well-exploration data for well
Graph showing well-exploration data for well
Graph showing well-exploration data for well
Graph showing well-exploration data for well
Graph showing well-exploration data for well
Graphs showing well-exploration data for
46-24-17 ---_ ...-------..


40-30-1
43-26-4
43-26-7 --------
43-26-12
43-26-26 --
44-24-15
44-25-42
44-26-10
44-26-31
45-24-13
45-24-17 ---
45-24-23
45-25-20
45-26-2 -------
45-26-3 --------
46-24-7 ------
46-24-8 ----
wells 46-24-12 and


26 Graphs showing well-exploration data for wells 47-23-8 and
48-23-15 .....--_
27 Hydrographs of wells 42-19-1 and 44-25-39 .........-----.....---------- ...
28 Hydrographs of wells 39-30-1, 40-27-7, 41-30-5, and 42-28-9 --.----
29 Hydrographs of wells 43-26-2, 44-25-5, 46-24-7, and 52-20-1 -.--..--
30 Hydrographs of and chloride content of water from wells 43-26-12
and 43-26-26 ..- ..------------.......... ..---------........--
31 Hydrographs of and chloride content of water from wells 44-25-38
and 44-26-31 _....-.. ..--.. _-
32 Hydrographs of and chloride content of water from wells 45-25-8
and 46-24-4
33 Hydrographs of and chloride content of water from wells 47-23-22
and 48-23-19
34 Effects of earthquakes and atmospheric pressure changes on the
water levels in wells 42-19-1 and 44-25-39 .--.--.........-----....---.....


age
4


25
26
27
28
29
30
31
31
32
33
34
35
36
37
38
39
40

41

42
43
44
45

46

47

48

49

50







35 Map of the Ruskin area showing the piezometric surface of the
Floridan aquifer in October 1952 -------- ------ ---- 51
36 Map of the Ruskin area showing the piezometric surface of the
Floridan aquifer in May 1953 ---.-- ------ --- 52
37 Map of the Ruskin area showing the area of artesian flow and
depth of water level below land surface ----------------------- 53
38 Logarithmic plot of drawdown in well 40-27-7 versus t/r2 ----- 54
39 Map of the Ruskin area showing wells sampled for chemical
analysis --..--..------------------................. .. ............----------------------55
40 Map of the Ruskin area showing the sulfate content of water from
the Florida aquifer .....------.----- ..- ----.......... .............. 59
41 Map of the Ruskin area showing the chloride content of water from
the Tampa formation -------..-. --- --------- 60
42 Map of the Ruskin area showing the chloride content of water
from the Suwannee limestone and older formations ------------ ---61
43 Map of the Ruskin area showing the dissolved-solids content of
water from the Floridan aquifer .---- ..-----------.. 63
44 Map of the Ruskin area showing the hardness of water from the
Floridan aquifer _-....----.....--.. ---------- --....- -... 64
45 Graph showing well-exploration data for well 44-25-28 -------- 67
46 Graph showing well-exploration data for well 47-23-22 --- ---------68
47 Graph showing well-exploration data for well 48-23-8 -------------68


TABLES

Table Page
1 Pleistocene terraces and shorelines of the Ruskin area------------- 9
2 Geologic formations penetrated by water wells in the Ruskin area 12
3 Stratigraphic nomenclature of the upper Eocene in Florida ---- 14
4 Summary of results of the current-meter explorations -------- ---- 24
5 Chemical analyses of artesian water from wells in the Ruskin area 57
6 Measurements of water level in wells in the Ruskin area --------- 75
7 Logs of selected wells in the Ruskin area ----.-------- ------ 81











THE ARTESIAN WATER OF THE RUSKIN AREA
OF HILLSBOROUGH COUNTY, FLORIDA
By
HARRY M. PEEK

ABSTRACT

The Ruskin area of Florida, as defined in this report, comprises
about 200 square miles in southwestern Hillsborough County. The
area has a subtropical climate and an average rainfall of more
than 50 inches, so that it is well suited to livestock farming and
growing of winter vegetables. As in much of the State, however,
truck crops and pasture require irrigation during periods of
relatively light rainfall; thus, large quantities of water are
withdrawn through many hundreds of wells during the growing
season.
The surface formations in the Ruskin area consist pre-
dominantly of deposits of sand, limestone, and shells, of
Pleistocene and Pliocene age, which range in thickness from a few
feet to about 60 feet. These deposits are underlain by the
Hawthorn formation, of middle Miocene age, which is exposed at
a few places. The Hawthorn consists of calcareous clay or marl
interbedded with limestone and sand and ranges in thickness from
less than 10 feet in the northern part of the area to more than
150 feet in the southern part. The Tampa formation,1 of early
Miocene age, underlies the Hawthorn formation and ranges in
thickness from 50 feet in the northern part of the area to about
200 feet in the southern part. Its upper surface ranges in eleva-
tion from about sea level in the northern part of the area to about
250 feet below sea level in the southern part. The Tampa is the
youngest of the limestone formations of Tertiary age, which have
a total thickness of several thousand feet in southwestern
Hillsborough County. The other limestone formations penetrated
by water wells in the area are the Suwannee limestone, of
Oligocene age, and the Ocala group and Avon Park limestone, of
Eocene age.

'The stratigraphic nomenclature used in this report conforms to that of
the Florida Geological Survey. It conforms also to that of the U. S.
Geological Survey, with the following exceptions: the Tampa limestone is
herein referred to as the Tampa formation and the Ocala limestone is
referred to as the Ocala group.






FLORIDA GEOLOGICAL SURVEY


The Hawthorn and younger formations are the source of some
domestic and other small water supplies, but the large quantities
of water required for irrigation and industrial use are obtained
from the underlying limestone formations.
The Suwannee limestone and Tampa formation are the principal
sources of artesian water in the area, although the older limestones
yield water to a few wells. The water in these formations occurs in
permeable zones that are separated by relatively impermeable
beds of considerable thickness. The water is replenished by rain-
fall in western Polk County and eastern Hillsborough County, and
it is confined under pressure by the relatively impermeable strata
within the formations and by the overlying Hawthorn formation.
The artesian aquifer has a transmissibility coefficient of about
115,000 gpd per foot and a storage coefficient of about 0.0006.
Significant fluctuations of artesian-pressure head result from
daily and seasonal variations in withdrawal of water from wells.
During periods of heaviest withdrawal, the piezometric surface
is lowered about four to five feet throughout the area and more
than eight feet at some places. The artesian pressure head
declined progressively in the coastal area during a period of
extensive agricultural development from 1950 to 1952. Since 1952,
however, seasonal fluctuations have decreased in magnitude and
a slight progressive rise in artesian head has occurred locally, as
a result of a decrease in withdrawals. Records of water levels
in wells not affected by local variations in discharge indicate that,
regionally, the artesian head declined progressively in 1955-56.

INTRODUCTION

Along much of the coast of Florida, salt water is present in
part or all of the principal water-bearing formations. Thus, the
problem in many coastal areas is to find supplies of fresh water
that are adequate to meet increased demands and are economically
feasible to develop. The problem in other areas is to protect
present supplies from contamination by salt water encroaching
from the sea or from formations that lie beneath the fresh-water
supply. Encroachment from either source may be induced by
excessive lowering of the fresh-water head.
During recent years, expansion of agriculture in the Ruskin
area of southwestern Hillsborough County has greatly increased
the use of artesian water for irrigation which has lowered the
artesian head in the area. The detection of -relatively salty water
in some wells has suggested that salt water may be encroaching






FLORIDA GEOLOGICAL SURVEY


The Hawthorn and younger formations are the source of some
domestic and other small water supplies, but the large quantities
of water required for irrigation and industrial use are obtained
from the underlying limestone formations.
The Suwannee limestone and Tampa formation are the principal
sources of artesian water in the area, although the older limestones
yield water to a few wells. The water in these formations occurs in
permeable zones that are separated by relatively impermeable
beds of considerable thickness. The water is replenished by rain-
fall in western Polk County and eastern Hillsborough County, and
it is confined under pressure by the relatively impermeable strata
within the formations and by the overlying Hawthorn formation.
The artesian aquifer has a transmissibility coefficient of about
115,000 gpd per foot and a storage coefficient of about 0.0006.
Significant fluctuations of artesian-pressure head result from
daily and seasonal variations in withdrawal of water from wells.
During periods of heaviest withdrawal, the piezometric surface
is lowered about four to five feet throughout the area and more
than eight feet at some places. The artesian pressure head
declined progressively in the coastal area during a period of
extensive agricultural development from 1950 to 1952. Since 1952,
however, seasonal fluctuations have decreased in magnitude and
a slight progressive rise in artesian head has occurred locally, as
a result of a decrease in withdrawals. Records of water levels
in wells not affected by local variations in discharge indicate that,
regionally, the artesian head declined progressively in 1955-56.

INTRODUCTION

Along much of the coast of Florida, salt water is present in
part or all of the principal water-bearing formations. Thus, the
problem in many coastal areas is to find supplies of fresh water
that are adequate to meet increased demands and are economically
feasible to develop. The problem in other areas is to protect
present supplies from contamination by salt water encroaching
from the sea or from formations that lie beneath the fresh-water
supply. Encroachment from either source may be induced by
excessive lowering of the fresh-water head.
During recent years, expansion of agriculture in the Ruskin
area of southwestern Hillsborough County has greatly increased
the use of artesian water for irrigation which has lowered the
artesian head in the area. The detection of -relatively salty water
in some wells has suggested that salt water may be encroaching






REPORT OF INVESTIGATIONS NO. 21


from Tampa Bay. Recognizing this possibility, the Board of
County Commissioners of Hillsborough County requested the U. S.
Geological Survey and the Florida Geological Survey to make a
study of the ground-water resources in the Ruskin area.
Accordingly, the Federal Geological Survey began an investigation
in October 1950, in cooperation with the above agencies.
Most of the fieldwork of the investigation was done by the
author prior to June 1953, under the immediate supervision of
H. H. Cooper, Jr., then District Engineer of the Federal Survey,
in Tallahassee. Completion of the fieldwork and preparation of
the report were under the immediate supervision of M. I.
Rorabaugh, present District Engineer of the U. S. Geological
Survey. The entire investigation was made under the general
supervision of A. N. Sayre, Chief of the Ground Water Branch,
U. S. Geological Survey.

PURPOSE AND SCOPE OF THE INVESTIGATION

The purpose of the investigation was to make a detailed study
of the geology and ground-water resources of southwestern
Hillsborough County, with the primary objective of determining
whether the artesian water had been contaminated by salt water
from Tampa Bay or from other sources. The investigation, there-
fore, consisted of several phases, as described below:

1. An inventory of about 650 selected wells, to obtain pertinent
information related to the occurrence and use of ground water in
the area.
2. Collection of data on water levels, to determine trends and
magnitude of water-level fluctuations, and for use in constructing
maps showing the altitude to which water will rise in artesian
wells.
3. Collection of water samples from selected wells, for chemical
analysis.
4. Determination of the chloride content of water from wells, to
ascertain the location and extent of areas in which the artesian
water has been contaminated.
5. Periodic determination of the chloride content of water from
selected wells, to understand the relation between the chlorinity
of the water and the artesian pressure head.
6. A study of geologic conditions as related to the occurrence
and movement of ground water.
7. Exploration of selected wells with a deep-well current meter,





FLORIDA GEOLOGICAL SURVEY


to determine the depth, thickness, and relative productivity of the
principal water-bearing zones.
8. Resistivity surveys and determination of the chloride content
of water samples collected at several different depths in selected
wells, to determine the relative chlorinity of the water in the
principal water-bearing zones.
9. Studies to determine the water-transmitting and water-
storing capacities of the different formations.


PREVIOUS INVESTIGATIONS

No detailed study of the geology and ground-water resources
of southwestern Hillsborough County has been made previously.
However, the Florida Geological Survey and the U. S. Geological
Survey have published several reports that include brief
discussions' of the geology and the occurrence of ground water in
Hillsborough County.
One of the earlier reports (Matson and Sanford, 1913, p. 320,
323; pl. 5) contains a generalized map of the Pleistocene terraces,
logs of wells, descriptions of formations exposed at the land sur-
face, and a brief discussion of the ground water of Hillsborough
County. A report by Sellards and Gunter (1913, p. 258-262, fig.
16) includes a summary of the geology and ground-water resources
of the county and contains a map showing the area of artesian
flow.
The geology and ground water of Hillsborough County are
described in a report by Stringfield (1936, p. 127, 128, 152). This
report includes maps of the Florida Peninsula showing the area
of artesian flow, the height above sea level to which water will
rise in wells that penetrate the principal artesian aquifer, and the
areas in which water with a chloride content of more than 100
parts per million (ppm) is present at moderate depths. Water-
level measurements and other data from several wells in the
county also are included.
A report by Parker and Cooke (1944, pl. 3) contains a map
showing the general configuration of the Pleistocene terraces in
southern Florida, including Hillsborough County. Reports by
MacNeil (1949, p. 105, pl. 19), Cooke (1945, p. 11-13, 245-312),
and Parker (Parker and others, 1955, p. 89-124, pl. 10) discuss
the Pleistocene terraces of Florida and contain maps showing
the configuration of the terraces and shorelines in Hillsborough
County.

















H /


01 0.0 3 .' oil
ti 174 oi 0 11 30 91
S ** I i/ s



41 .> *'


27'.

INSET 'I"


Plate 1. Map of the Ruskin area showing location of wells.


L L SI


to-l






REPORT OF INVESTIGATIONS NO. 21


The formations penetrated by wells and those exposed at the
surface are described in some detail in a report on the geology of
Florida by Cooke (1945, p. 34, 42, 47, 125, 208, 222, 290, 305).
A report by Vernon (1951, figs. 11, 33, pl. 2) contains maps
showing the subsurface features of some of the formations under-
lying Hillsborough County.
Chemical analyses of water from several wells and springs in
Hillsborough County are included in a report by Collins and
Howard (1928, p. 216-217) and one by Black and Brown (1951,
p. 64).

ACKNOWLEDGMENTS

Appreciation is expressed to the many well owners in the
Ruskin area who contributed information and otherwise aided
the investigation. Special acknowledgment is made to the well
drillers who collected rock cuttings and furnished much valuable
information. These include H. J. Tucker, Howard Morrill, and
E. E. Boyette, of Ruskin; and May Bros. of Tampa.

WELL-NUMBERING SYSTEM

The well-numbering system used in this report is based on
latitude and longitude. The Ruskin area, which lies between 270
and 280 north latitude and 82 and 830 west longitude (fig. 1),
has been divided into quadrangles by a grid of 1-minute parallels
of latitude and 1-minute meridians of longitude, as shown on
plate 1. The wells have been assigned numbers according to their
location within this grid. Each well number consists of three
parts: the first part is the latitude, in minutes, of the south side
of the 1-minute quadrangle in which the well is located; the
second part is the longitude, in minutes, of the east side of the
same 1-minute quadrangle; and the third part is the number of
the well within the quadrangle. For example, the number 43-25-4
designates the fourth well in the quadrangle bounded by latitude
43' on the south and longitude 25' on the east. The degree of
latitude and longitude are not included as a part of the well
number, as they are the same for all wells used in this report.
Well locations are shown on the map, plate 1. Complete well
descriptions, locations, and other data are published in Florida
Geological Survey Information Circular No. 22 and may be
obtained for one dollar per copy.






FLORIDA GEOLOGICAL SURVEY


Figure 1. Map of the peninsula of Florida showing location of Hillsborough
County and the Ruskin area.







REPORT OF INVESTIGATIONS NO. 21


GEOGRAPHY

The Ruskin area, as defined for this report, comprises about
200 square miles in southwestern Hillsborough County (fig. 1).
It is bounded on the south by Manatee County and extends
northward to the 27056' parallel of north latitude. From Tampa
Bay, which forms the western boundary, the area extends eastward
to the 82017' meridian of west longitude.

CLIMATE

The Ruskin area has a subtropical climate, with a mean
temperature of about 720 F, according to the U. S. Weather
Bureau. The mean monthly temperatures at Tampa range from
61.50 F in January to 820 F in August, as shown in figure 2. For
comparison, the figure shows the average maximum and minimum
monthly temperatures during 1956.
The records of the U. S. Weather Bureau show (fig. 2) that
the average yearly precipitation at Tampa during the period from
1891 through 1955 was 49.94 inches; the range was from 32.25
inches in 1908 to 67.19 inches in 1912. The average monthly rain-
fall ranged from 1.04 inches in November to 8.11 inches in July,
and more than 70 percent of the annual precipitation occurred
between June 1 and September 30.

PHYSIOGRAPHY

The Ruskin area is in the Terraced Coastal Lowlands of Vernon
(1951, p. 16), a subdivision of the Coastal Plain province. The
topographic forms consist mostly of marine terraces and associated
features that were developed during the Pleistocene time, when
the sea at several times stood above or below its present level.
The topography may be divided generally into units-a relatively
flat coastal area and a hilly upland area. The coastal area is about
three to six miles wide and extends inland from Tampa Bay to
an escarpment that represents the shoreline of the Pamlico sea
of late Pleistocene time. The coastal area slopes gently toward
the bay from the base of the escarpment, which is about 25 feet
above sea level. Most of the coastal area is between 5 and 15 feet
above sea level, but it contains a few low hills and ridges having
altitudes of 30 feet or more. The hilly upland area extends east-
ward from the Pamlico escarpment, gradually increasing in
altitude to more than 100 feet in the vicinity of Wimauma. Most







FLORIDA GEOLOGICAL SURVEY


14
;;iiii____-
2
10


8


MINIMM- (1891-1


Figure 2. Precipitation and temperature at Tampa.

of the upland area consists of low rolling hills having relatively
flat summits, at altitudes of 50 to 90 feet. The marine terraces and
associated features have been modified to some extent by stream
dissection. Numerous ponds, depressions, and swamps occur in
the poorly drained parts of the area.
The history of the Pleistocene epoch and the marine terraces
and deposits associated with the fluctuations of sea level in Florida
are discussed in detail in reports by Cooke (1945, p. 11-13, 245-
312), Vernon (1951, p. 15-42, 208-215), and Parker (Parker and
others, 1955, p. 89-124). The rise and fall of the sea is attributed
to the advance and retreat of the great continental ice sheets,
the sea level rising during interglacial periods and falling during
glacial periods. When the sea remained relatively stationary for
long periods, shoreline features and marine plains were developed.
The remnants of five marine terraces of Pleistocene age and the
general configuration of four shorelines have been mapped in the
Ruskin area (Cooke, 1945, figs. 43-47; Parker and others, 1955,
pl. 10), as listed in the following table:


22 MAXIMUM (1891-1955)
20- -
18- AVERAGE (1891-1955) V
MINIMUM (1891-1955i


7U.1


W


2

Sz
-







REPORT OF INVESTIGATIONS NO. 21


TABLE 1. Pleistocene Terraces and Shorelines of the Ruskin Area

Terrace Altitude of shoreline
(feet above msl)

Sunderland ----------.-------------... ..........------------. 1701
Wicomico .---------- .... ----------------.............. 100
Penholoway -------------------------- ----------..... 70
Talbot ---- --- ----- ------------- ---------................................... ...... 42
Pamlico ------------------------25

'Sunderland shoreline not present in Ruskin area.

Figure 3 shows the general boundaries of the Pleistocene ter-
races in the Ruskin area, as determined from aerial photographs,
topographic maps, and field observation. The highest and oldest
surface lies above the Wicomico shoreline and represents the
remnants of the Sunderland terrace (Cooke, 1945, p. 278-279).
The sea was about 170 feet above the present level when the
Sunderland was formed, and practically all of south Florida was
submerged.
During Wicomico time, the sea stood about 100 feet above the
present level and all the Ruskin area was submerged except the
Sunderland terrace and associated islands. The shoreline of the
Wicomico sea is marked by an escarpment that is well preserved
in many places.
The Penholoway terrace was formed when the sea stood at
an altitude of about 70 feet. The general configuration of the
shoreline can be distinguished on aerial photographs, on topo-
graphic maps, and in the field (fig. 3).
The shoreline of the Talbot sea, which stood at an altitude of
about 42 feet, is poorly defined throughout most of the area, and
in many places the shoreline escarpment coincides with the
escarpment of the Pamlico terrace.
The Pamlico terrace is the youngest Pleistocene terrace that
has been recognized in the Tampa Bay area. It was formed when
the sea was about 25 to 30 feet above the present level. The shore-
line of the Pamlico sea is marked by an escarpment which is well
preserved throughout most of the area. The base of the escarpment
is generally about 25 feet above sea level.
Surface drainage in the Ruskin area is principally through the
Little Manatee River, the Alafia River, and Bullfrog Creek, all of
which flow into Tampa Bay. Much of .the coastal area is drained
by small streams that extend inland from Tampa Bay for relatively







FLORIDA GEOLOGICAL SURVEY


"C.

Y.9 ..f^.-3.H^ILLSBOROUGH ^ C.UTY ^ \1
MANATEE COUNTY
''* i^ ;*3Cf 2'2S f


Figure 3. Map of the Ruskin area showing the Pleistocene terraces.

short distances. Canals have been dug throughout most of the
area to supplement the natural drainage.

CULTURE

The principal towns in the Ruskin area are East Tampa,
Gibsonton, Riverview, Ruskin, Sun City, and Wimauma (pl.
1). U. S. Highway 41 passes through all towns along the coast








REPORT OF INVESTIGATIONS NO. 21


and connects them with Tampa to the north and Bradenton to the
south. U. S. Highway 301 provides a north-south route through
the eastern part of the area. State Highway 674 and several
other paved roads- connect the U. S. Highways. The Atlantic
Coastline Railroad provides transportation in the coastal area and
the Seaboard Air Line Railroad serves Wimauma and the eastern
part of the area.

GEOLOGY

The surface formations over most of the Ruskin area consist
of undifferentiated deposits of Pleistocene age, although beds as
old as Miocene are exposed at some places. The geologic forma-
tions penetrated by water wells are listed and briefly described
in table 2, and geologic cross sections are shown in figure 4. The
subsurface formations are described on the basis of rock cuttings,
electric logs, and drillers' logs of wells in and adjacent to the
Ruskin area. Those penetrated by water wells in the area are the
only formations discussed in this report.








s-500 F 0 -900
-oSUWANNEE -
zA2i A i6 6 n o t to m -50









-6oX OCALA GROUP ,o
0 (Pleis tocene Pliocene) Zeg 0











ooEo


S H HAWTHORN
T 06 R NTAMPA -
-J-








-100 FORMATION -20
(Migocene)














SUWANNEE LIMESTONE
400 -400
> -00 50












Figure 4. Geologic cross sections showing the formations penetrated by water
wells in the Ruskin area.
FO FORMATION 0
-100 o(Miocenc) -100

Miocene) S

WSUWANNEE LIMESTONE -500
-(Oligocene) 1
W_ 500 ------------*- -- ---,0 ---- -00-^ -







wells in the Ruskin area.







12 FLORIDA GEOLOGICAL SURVEY

TABLE 2. Geologic Formations Penetrated by Water Wells in the Ruskin Area

Thickness
Age Formation Characteristics (feet)

Pamlico sand Sand, shells, limestone, and calcareous
Older Terrace clay. 0- 60
deposits Sand, silt, and some clay.

rI Undifferentiated Sand and gravel of quartz and phos- 0- 20?
deposits phate, clay, and bone fragments.
SSand, shells, gravel of quartz and 0- 25?
phosphate, and lignite.

Hawthorn Clay and marl, gray, greenish gray to 10-150
formation blue-gray, sandy, phosphatic, inter-
bedded with sandy limestone, sand,
silt and shells. Serves as a confining
layer for the water in the underlying
limestones but is the source of small
water supplies.

Tampa Limestone, creamy white, gray, and tan, 50-200
formation fairly hard, porous to dense, sandy,
fossiliferous, silicified in part. A very
productive source of artesian water.

Suwannee Limestone, creamy white to tan, fairly 200-225
limestone soft, granular, porous, fossiliferous,
crystalline and dolomitic in part. Prob-
ably a more productive source of
water than the Tampa, but water is
somewhat more mineralized.

Ocala group Limestone, white, cream and tan, soft, 250
granular, chalky, fossiliferous, co-
quinoid in part. Penetrated by only a
few wells in the Ruskin area but may
be a very productive source of ar-
tesian water. The water is probably
highly mineralized in the coastal area.
Avon Park Limestone, white to tan, soft, somewhat 600-700
limestone chalky, granular, foraminiferal; dolo-
mite, tan to dark brown hard crystal-
line, lignitic in part, very porous. A
very productive source of artesian
water but tapped by very few wells.
Water is salty in the coastal area.







REPORT OF INVESTIGATIONS NO. 21


EOCENE SERIES

The Eocene limestones have a combined thickness of about
5,000 feet in the Tampa Bay area, but only the upper part of this
limestone section is tapped by water wells.

AVON PARK LIMESTONE

The upper part of the late middle Eocene limestone in Florida
was named the Avon Park limestone by Applin and Applin (1944,
p. 1680, 1686). It is the oldest formation exposed at the surface
(with outcrops in Citrus and Levy counties) and is also the oldest
formation penetrated by water wells in southwestern Hillsborough
County.
The upper part of the Avon Park consists predominantly of
white to tan, soft, chalky, granular limestone containing many
foraminifers and other fossils. The lower part is principally a
tan to dark brown, hard, crystalline dolomite containing
carbonaceous material but very few fossils.
The Avon Park limestone is probably about 600 to 700 feet
thick in the Ruskin area. The top of the formation ranges in
depth from about 575 feet below sea level in the northern part of
the area to about 900 feet in the southern part.
The formation is very permeable, owing to the extensive
development of solution channels, and is a productive source of
artesian water. However, relatively few wells in the area penetrate
the Avon Park, because it contains highly mineralized water in
much of the coastal zone and sufficient quantities of water of better
quality can be obtained from the younger formations at shallower
depths.

OCALA GROUP

Until recent years, all the limestone deposits of late Eocene
age in peninsular Florida were considered as a single formation,
the Ocala limestone. As shown in table 3, Cooke (1945, p. 53-62)
and Applin and Applin (1944, p. 1683) referred all late Eocene
limestones to the Ocala; however, Applin and Applin recognized
upper and lower members of the formation, on the basis of
lithologic and faunal differences. After completion of his studies
in Citrus and Levy counties, Vernon (1951, p. 111-171) separated
the late Eocene limestones into two formationis-the Ocala lime-
stone, restricted to the upper part, and the Moodys Branch







FLORIDA GEOLOGICAL SURVEY


formation. He also divided the Moodys Branch formation into
two members-the Williston member, to include the upper part,
and the Inglis member, to include the lower part. Puri (1953, p.
130) changed the name of the Ocala limestone (as restricted by
Vernon) to the Crystal River formation, and gave formational
rank to the Williston and Inglis members of Vernon's Moodys
Branch formation. The Crystal River, Williston and Inglis
formations, as described by Puri, are now referred to as the Ocala
group by the Florida Geological Survey.


TABLE 3. Stratigraphic Nomenclature of the Upper Eocene in Florida


U. S. Geological Survey Florida Geological Survey

Cooke (1945) Applin (1944) Vernon (1951) Puri (1953)

Upper Ocala limestone Crystal
member (restricted) River
formation
--_ __ ______ -Ocala
Ocala Ocala
letn cl m n Lower Moodys group
limestone limestone member Branch Williston Williston
formation member formation

Inglis Inglis
member formation


The Ocala group lies unconformably on the Avon Park lime-
stone in southwestern Hillsborough County and is probably about
250 feet thick. The top of the formation ranges in depth from
about 300 feet below sea level in the northern part of the area to
about 600 feet in the southern part. The upper part of the Ocala
is a creamy white to tan, soft, somewhat granular, chalky,
coquinoid limestone, composed of the remains of foraminifers,
mollusks, echinoids, and other fossils which are loosely cemented
in a fine, granular, chalky matrix. The lower part of the Ocala
is more granular and less chalky than the upper part and contains
fewer foraminifers.
The Ocala is penetrated by relatively few wells in the Ruskin
area, although it may be a productive source of water. In the
coastal area, the water in the Ocala has a considerably higher
mineral content than the water in the younger limestones.








REPORT OF INVESTIGATIONS NO. 21


and connects them with Tampa to the north and Bradenton to the
south. U. S. Highway 301 provides a north-south route through
the eastern part of the area. State Highway 674 and several
other paved roads- connect the U. S. Highways. The Atlantic
Coastline Railroad provides transportation in the coastal area and
the Seaboard Air Line Railroad serves Wimauma and the eastern
part of the area.

GEOLOGY

The surface formations over most of the Ruskin area consist
of undifferentiated deposits of Pleistocene age, although beds as
old as Miocene are exposed at some places. The geologic forma-
tions penetrated by water wells are listed and briefly described
in table 2, and geologic cross sections are shown in figure 4. The
subsurface formations are described on the basis of rock cuttings,
electric logs, and drillers' logs of wells in and adjacent to the
Ruskin area. Those penetrated by water wells in the area are the
only formations discussed in this report.








s-500 F 0 -900
-oSUWANNEE -
zA2i A i6 6 n o t to m -50









-6oX OCALA GROUP ,o
0 (Pleis tocene Pliocene) Zeg 0











ooEo


S H HAWTHORN
T 06 R NTAMPA -
-J-








-100 FORMATION -20
(Migocene)














SUWANNEE LIMESTONE
400 -400
> -00 50












Figure 4. Geologic cross sections showing the formations penetrated by water
wells in the Ruskin area.
FO FORMATION 0
-100 o(Miocenc) -100

Miocene) S

WSUWANNEE LIMESTONE -500
-(Oligocene) 1
W_ 500 ------------*- -- ---,0 ---- -00-^ -







wells in the Ruskin area.







REPORT OF INVESTIGATIONS NO. 21


OLIGOCENE SERIES
SUWANNEE LIMESTONE
The Suwannee limestone, as defined in this report, includes all
deposits of Oligocene age in the Ruskin area. The Suwannee is
differentiated from the underlying Eocene formations and the
overlying Miocene formations on the basis of lithology and fauna
and is separated from these formations by unconformities.
The upper part of the Suwannee is generally a creamy white
to tan, soft, granular, fossiliferous limestone, but at some places
it contains beds that are crystalline, dolomitic, and partly silicified.
The lower part of the formation is generally a tan to brown, soft
to hard, granular to dense limestone that is harder, more crystal-
line and dolomitic, and less fossiliferous than the upper part. The
formation contains abundant remains of mollusks, echinoids, and
foraminifers. Specimens of the foraminifer Rotalia mexicana are
fairly abundant throughout the formation. The occurrence of
Dictyoconus cookei and Coskinolina floridana is generally restricted
to the lower part of the Suwannee.
The top of the Suwannee limestone in the Ruskin area ranges
in depth from about 75 feet below sea level in the northern part
of the area to about 400 feet in the southwestern part. The
formation has a fairly uniform thickness of about 200 to 225 feet.
The contours on the map in figure 5 show the configuration and
approximate altitude of the top of the formation.
The Suwannee limestone is probably the most productive
source of artesian water generally tapped in the Ruskin area. In
the coastal area, however, the water in the Suwannee is somewhat
more mineralized than the water in the overlying. Tampa
formation.
MIOCENE SERIES
The deposits of Miocene age in the Ruskin area are herein
referred to the Tampa formation of early Miocene age (Cooke,
1945, p. 1070) and the Hawthorn formation of middle Miocene
age. Both formations are of marine origin, but they represent
different depositional environments and are separated .by un-
conformities.
TAMPA FORMATION
The Tampa formation lies unconformably on the Suwannee
limestone of Oligocene age and consists of white, gray, and tan
hard, dense, sandy limestone. It is crystalline and dolomitic in





FLORIDA GEOLOGICAL SURVEY


,, .C- HILLSBOROUGH COUNTY .__ / -
1 '. 8225 MANATEE" COUNTY U' +1

Figure 5. Map of the Ruskin area showing the configuration and altitude of
the top of the Suwannee limestone.

part and contains silicified layers. The formation is generally
fossiliferous, containing echinoid plates and spines, tests of
ostracods and foraminifers, and many molds and casts of mollusks.
Specimens of the foraminifers Archaias and Sorites are fairly
abundant throughout most of the Tampa.
The top of the Tampa formation ranges in depth from a little
below sea level in the northern part of the Ruskin area to about





REPORT OF INVESTIGATIONS NO. 21


Figure 6. Map of the Ruskin area showing the configuration and altitude of
the top of the Tampa formation.

250 feet below sea level in the southern part. The contours on the
map in figure 6 show the configuration and approximate altitude
of the top of the formation in the area. The thickness of the
Tampa is about 50 feet near the northern boundary of the area and
increases southward, in the direction of dip, to about 200 feet (fig.
4). The average thickness is about 175.feet in the area south of
Big Bend Road (pl. 1).






FLORIDA GEOLOGICAL SURVEY


The Tampa formation is a productive source-of artesian water
in the Ruskin area. Most of the water is obtained from relatively
thin zones that have a high permeability, owing to the many inter-
connecting cavities formed by solution of the limestone.

HAWTHORN FORMATION

The Hawthorn formation, as defined in this report, includes
all marine deposits of middle Miocene age. It was deposited in
shallow water and consists predominantly of gray, blue-gray and
gray-green, sandy, calcareous, phosphoritic clay interbedded with
thin layers of gray, white, and tan sandy phosphoritic limestone,
and thin beds of sand and shells. The limestone layers are
dolomitic, silicified, and fossiliferous in part. The altitude of the
top of the Hawthorn ranges from about 25 feet above sea level
to about 50 feet below sea level, and the upper part of the
formation is exposed at several places in the area. The thickness
increases from north to south in the direction of dip, ranging from
less than 10 feet in the northern part of the area to more than
150 feet in the southern part (fig. 4).
The thin beds of sand and limestone yield artesian water to
some wells in the area, but the Hawthorn is not generally a very
productive source of water. Because of the thickness and low
permeability of the clay beds, the Hawthorn serves as a confining,
layer for the water in the underlying limestones.

PLIOCENE AND PLEISTOCENE SERIES

The Hawthorn formation is overlain at some places by about
5 to 10 feet of sediments that consist of shells, sand, carbonaceous
material, and gravel of phosphorite and quartz. At other places
it is overlain by several feet of sediments consisting predominantly
of sand but containing some clay, gravel of quartz and phosphate,
bone fragments, and shark teeth. The age of these sediments has
not been determined, but it is probably late Miocene or Pliocene.
Pleistocene sediments of the higher terraces consist mostly
of undifferentiated sands that range in thickness from about 10
feet to 60 feet. The surface of the Pamlico terrace/ is underlain
by sand, sandy clay, and shells. The beds of limesto e and shells,
which pinch out near the Pamlico shoreline and are generally less
than 20 feet above sea level, were apparently deposited during
late Pleistocene time. However, these beds were referred by Cooke
(1945, p. 222-223) to the Caloosahatchee marl of Pliocene age.






REPORT OF INVESTIGATIONS NO. 21


Phe Pleistocene deposits beneath the Pamlico surface range in
sicknesss from about 10 feet to 50 feet, except where they have
been completely eroded by streams. The Pleistocene deposits are
the source of a few domestic water supplies in the area.

GROUND WATER

PRINCIPLES OF OCCURRENCE

Practically all the water of the earth moves through the vast
circulatory system known as the hydrologic cycle. Water
condenses from the moisture in the atmosphere and falls as rain
or snow, moves over or beneath the land surface to the oceans,
and is returned to the atmosphere. Actually, the cycle may be
modified or completed at any time after the water condenses from
the atmosphere, as evaporation may begin even before the water
reaches the earth and continue throughout the entire cycle. Great
quantities of water are returned to the atmosphere by
evaporation from vegetal surfaces (transpiration).
Much of the water that falls on the land surface as rain or
snow runs off into streams, lakes, or other bodies of surface water,
and a part eventually reaches the oceans. Some water is returned
to the atmosphere by evaporation directly from land and water
surfaces, and a part of it is absorbed by the soil or surficial rocks
and becomes subsurface water. The amount of water than sinks
directly into the ground from each rainfall depends on many
factors, such as the slope of the land surface, vegetal cover,
intensity of the rainfall, and previous moisture content and
character of the surface material.
Subsurface water may be divided into two general classes-
suspended water and ground water. Suspended water is the water
in the zone of aeration-the zone in which the interstices of the
soil or rocks are not completely filled with water. Ground water is
the water in the zone in which all the interstices are completely
filled with water under greater than atmospheric pressure. This
saturated zone is the reservoir that yields water to all springs and
I wells.
The water in the zone of saturation may occur as (1)
unconfined ground water (under nonartesian conditions), or (2)
confined ground water (under artesian conditions). Where the
ground water is not confined-its upper surface is under
atmospheric pressure and is free to rise. and fall-it is said to be
under nonartesian conditions. Its upper surface is called the water





FLORIDA GEOLOGICAL SURVEY


table. Where the water is confined in a permeable bed that is
overlain and underlain by relatively impermeable beds, its upper
surface is not free to rise and fall and it is said to be under
artesian conditions. The term "artesian" is applied to ground
water that is confined under sufficient pressure to cause it to rise
above the top of the permeable bed that contains it, but not
necessarily above the land surface.
An aquifer is a formation, group of formations, or part of a
formation, in the zone of saturation, that is permeable enough to
transmit usable quantities of water. Recharge is the process of
replenishment of the water in an aquifer, and areas in which it
occurs are known as recharge areas. Generally, unconfined
aquifers may receive direct recharge from precipitation through-
out their lateral extent, whereas artesian aquifers may receive
such recharge only where their confining beds are absent or
relatively permeable.
The piezometric surface of an aquifer is an imaginary surface
to which water from an artesian aquifer will rise in tightly cased
wells that penetrate the aquifer. Where the piezometric surface is
above the land surface, artesian wells will flow under natural
pressure.

GROUND WATER IN FLORIDA

Ground water occurs in Florida under both nonartesian and
artesian conditions. Nonartesian conditions are generally
restricted to the shallow deposits of sand, gravel, shells, and lime-
stone which form many aquifers of relatively small areal extent.
These deposits are the source of many domestic water supplies
throughout the State and also of public and industrial supplies
in areas where the deeper formations contain salty water. The
water in the unconfined aquifers is generally replenished by local
rainfall.

ARTESIAN WATER

Most of Florida is underlain by a thick section of permeable
limestone formations of Eocene, Oligocene, and Miocene age. These
formations compose an extensive artesian aquifer from which
most of the large ground-water supplies of the State are obtained.
Stringfield (1936, p. 125-132, 146) described the aquifer and
mapped the piezometric surface in 1933 and 1934. The name
"Floridan aquifer" was introduced by Parker (Parker and others,






REPORT OF INVESTIGATIONS NO. 21


1955, p. 188-189) to include "parts or all of the middle Eocene
(Avon Park and Lake City limestones), upper Eocene (Ocala lime-
stone), Oligocene (Suwannee limestone), and Miocene (Tampa
limestone, and permeable parts of the Hawthorn formation that are
in hydrologic contact with the rest of the aquifer)," The artesian
water is confined by relatively impermeable layers in the limestone
formations and by the overlying clay beds of Miocene age which
extend over most of the State. The water in the artesian aquifer
is replenished chiefly by rainfall in areas where the confining beds
are absent, are breached by sinkholes, or are sufficiently permeable
to permit the passage of water from the land surface into the
limestone.

PIEZOMETRIC SURFACE

The configuration of the piezometric surface in peninsular
Florida is shown by the contour lines in figure 7. These lines
represent the height, in feet above sea level, to which water will
rise in wells that penetrate the Floridan aquifer. They indicate
the areas in which recharge occurs; and, through inference, the
general direction of water movement in the Floridan aquifer may
be deduced. In areas of recharge, the piezometric surface is
relatively high. The water moves away from these areas in the
direction of steepest gradient, at right angles to the contour lines,
toward areas of discharge, where the piezometric surface is
relatively low. In central Florida the piezometric surface forms
an elongated dome which is centered in northern Polk County.
The presence of this dome indicates that the lake region of Polk
County is the center of a relatively large area of recharge which
probably extends into adjacent counties (Stringfield, 1936, p. 148).
The water enters the limestone formations in this area through the
numerous sinkholes and at places where the confining bed is either
absent or slightly permeable.

GROUND WATER IN THE RUSKIN AREA

In the Ruskin area the water in the Pleistocene sands and other
permeable beds that lie above the Hawthorn formation is generally
unconfined and is replenished by local rainfall. A few small
domestic water supplies are obtained from these formations, but
most domestic and larger supplies are obtained from the permeable
beds of the Hawthorn formation or the underlying limestones.






FLORIDA GEOLOGICAL SURVEY


Figure 7. Map of peninsular Florida showing the piezometric surface of the
Floridan aquifer in 1949.






REPORT OF INVESTIGATIONS NO. 21


ARTESIAN WATER

In the Ruskin area, as in most of the State, the Floridan
aquifer is the principal artesian aquifer. The water in this
aquifer is replenished chiefly by infiltration of rainfall in the re-
charge area centered in northern Polk County. From there it
moves southwestward into the Ruskin area, as suggested by the
configuration of the contours in figure 7.
The Avon Park limestone and the Ocala group of Eocene age,
which are productive sources of water in much of peninsular
Florida, are probably capable of yielding large quantities of water
in the Ruskin area. These formations are penetrated by very few
wells in the area, however, as the Suwannee limestone and Tampa
formation are sufficiently productive to supply most wells.
The water in the Suwannee limestone and Tampa formation
occurs in permeable zones separated by relatively impermeable
layers which retard vertical movement of the water and serve
locally as confining beds.
The Hawthorn formation consists predominantly of clay and
serves as a confining bed for the water in the Floridan aquifer.
Thin beds of sand and limestone within the formation contain
artesian water that is the source of many domestic supplies and
some small irrigation supplies. The artesian pressure head in
the Hawthorn is considerably less than the head in the Floridan
aquifer; thus, the Hawthorn probably receives some recharge by
upward percolation of water from the Floridan aquifer.
Current-Meter Exploration: In order to determine the depth,
thickness, and relative productivity of the different water-bearing
zones in the limestone formations, explorations were made in
several selected wells with a deep-well current meter, a device
for measuring the velocity of flow of water through a well bore.
The results of the current-meter traverses are shown graphically
in figures 8 through 26, which also include well-construction data,
electric logs, and resistivity and chloride content of the water. The
velocity of the water is expressed in revolutions per minute (rpm)
of the current meter. Actual flow rates, which are a function of
velocity and cross-sectional area, cannot be computed accurately,
as the diameter of the uncased part of the wells is not uniform.
A summary of the information obtained from the current-
meter explorations (figs. 8-26) is given in table 4.
Fluctuations of Artesian Pressure Head: Fluctuations of
artesian pressure head range from a fraction of a foot to several
feet and are caused by one or more of several factors. The larger





FLORIDA GEOLOGICAL SURVEY


TABLE 4. Summary of Results of the Current-Meter Explorations


Depth of principal
producing zones
(feet below msl)


40-30-1 250 200 to 245
245 to 355
355 to 360
420 to 445


43-26-4 100 320 to 325
365 to 395
420 to 480


43-26-7 300 245 to 285
315 to 325
355 to 365


43-26-12 300 125 to 150
235 to 250
325 to 350


43-26-26 300 100 to 120
200 to 270
310 to 410


44-24-15 50 280 to 290


44-25-42 350 120 to 160
295 to 335
355 to 370


44-26-10 200 100 to 285
305 to 320
345 to 370


44-26-31 350 395 to 420+


45-24-13 350


70 to 190
395 to 404


Well
number


Rate of
flow
(gpm)


Depth of principal
producing zones
(feet below msl)


45-24-17 300 220 to 260
295 to 310
340 to 345

45-24-23 125 155 to 170
255 to 265
365 to 380

45-25-20 200 90 to 105
170 to 265

45-26-2 125 110 to 140
295 to 305

45-26-3 250 170 to 195
265 to 275
355 to 385
410 to 420

46-24-7 350 195 to 495

46-24-8 350 85 to 105
235 to 275
395 to 415

46-24-12 150 70 to 80
195 to 237+

46-24-17 250 170 to 190
295 to 333

47-23-8 125 150 to 160
255 to 275


48-23-15


150 175
215
265


190
240
280


Well Rate of
number flow
(gpm)


I







REPORT OF INVESTIGATIONS NO. 21


AGE FORMA- SELF-POTENTIAL RELATIVE RESISTIVITY O(rpm cWA ter)
TIN (rpm of current meter)
T2 5m 25 ohms0 50 10
4 I


z


0L



W
a:
0

_j


PLEISTOCENE
5 PLIOCENE

z



0
I




z


Figure 8. Graph showing well-exploration data for well 40-30-1.

fluctuations generally result from daily and seasonal changes in
withdrawal of water from wells or from variations in recharge
from rainfall. Minor fluctuations are caused by tides, atmospheric-
pressure changes, winds, earthquakes, and passing trains. The
minor fluctuations of water levels and their causes are discussed
in detail in a paper by Parker and Stringfield (1950).
Records from continuous recording gages on two wells and
periodic water-level measurements in about 20 wells provide
information on the fluctuations of artesian pressure head in the
Ruskin area during a period of about 6 years. Hydrographs pre-
pared from the records of the continuous recording gages on
wells 42-19-1 and 44-25-39 are shown in figure 27. Hydrographs
of 16 wells in which water levels were measured periodically are
3hown in figures 28-33. Water-level measurements in other wells
are listed in table 6 and in Information Circular No. 22.


(


_j
LJ
W
_j
-J
-I




I-
2



0
LI
C -300-
<


ud

1-
Q
lI-I



-400-

a_
[Li


0-00


-500-





FLORIDA GEOLOGICAL SURVEY


FORMA- WELL VELOCITY OF WATER CHLORIDE
AGE TION 43E (rpm of current meter) LoPrts per million)
0 50- 100 0 50


PLEISTOCENE
a PLIOCENE

z z
Cr 0


Figure 9. Graph showing well-exploration data for well 43-26-4.

The hydrograph of well 42-19-1 (fig. 27) shows the seasonal
fluctuations and regional trend of the artesian pressure head from
August 1951 to December 1956. The seasonal use of water i:s
indicated by the declines in head during periods of least rainfall,
when large quantities of water were being used for irrigation.
The rises in head, corresponding to periods of greater rainfall,
are due primarily to a decrease in discharge but at times may


0




,.J
LUI
> -100
LU
-i

LU
(/)

LL
: -200
0
H


0
LU
L-
CC

ILL
iU
Mr -300
1--
Lii
LJ
LL
U-


0 -400
LU
0


I 1
__ 8 __ ^ _







=:=|=::::














___ ___ __ __




I t I


-500






REPORT OF INVESTIGATIONS NO. 21


Figure 10. Graph showing well-exploration data for well 43-26-7.

indicate an increase in recharge. The hydrograph indicates that
the magnitude of seasonal fluctuations has increased from about
four feet in 1952 to about eight feet in 1956. The lowest recorded
water level in this well was 29.6 feet, in April 1956. The
progressive increase in the magnitude of seasonal fluctuations and
the general downward trend of the artesian pressure head
throughout the period of record reflect the regional increase in
both seasonal and perennial use of water.
The hydrograph of well 44-25-39 (fig. 27) shows the effects
of seasonal differences in local withdrawals. The slight downward














































Figure 11. Graph showing well-exploration data for well 43-26-12.






REPORT OF INVESTIGATIONS NO. 21


trend of the artesian pressure head from 1950 to 1952 probably
reflects the increased use of water resulting from expansion of
agriculture during this period. The hydrograph indicates that
local use of water has been relatively stable since 1952.
The hydrographs in figures 28-33 also show seasonal
fluctuations due to local discharge. Some hydrographs indicate
that discharge has remained relatively stable since about 1952,
whereas others show a general upward trend of the artesian
pressure head since 1953, thus indicating a decrease in local use of
water.
Although the principal fluctuations of artesian head in the
Ruskin area -are caused by changes in the rate of withdrawal of
water from wells, observable changes are caused by earthquakes,
atmospheric-pressure changes, and other factors.
Earthquake waves passing through the earth's crust cause a
relatively rapid expansion and contraction of artesian aquifers,
which results in fluctuations of the artesian pressure head. The
magnitude of these fluctuations in a particular well may range
from a few hundredths of a foot to several feet, according to the
intensity of the earthquake and the distance of the epicenter from


Figure 12. Graph showing well-exploration data for well 43-26-26.






30 FLORIDA GEOLOGICAL SURVEY


FORMA- WELL VELOCITY
AGE TION 44-24-15 (rpm of current meter)
0 25 50
0- PLEISTOCENE
SPLIOCENE

zz



0 0
LL u





0 2 -
ti-
1o o


00
z -100- LJ --- b -- "












-300-
LL 0

0U


z 0 w
-400- U
-- -D z
S-20- S -- -- -- --









Lu
Hi z.
LU1 -J ^






REPORT OF INVESTIGATIONS No. 21 31


Figure 14. Graph showing well-exploration data for well 44-25-42.


Figure 15. Graph showing well-exploration data for well 44-26-10.



















- ,00 --. --




:: ,l^_y
z
i4






W2
300-







o R
LhJ4300 1----- :: -------_---- -__--- --







400 _j^'?
Liii


4igur 16. Graph showing----l-ep rin---- ---- ----
o o

Figure 16. Graph showing well-exploration data for well 44-26-31.





DEPTH, IN FEET BELOW MEAN'SEA LEVEL

o o o
0 0 0

C OLIGOCENE M I C E N E m
HAWTHORN go
S SUWANNEE LIMESTONE TAMPA FORMATION FORMAN 5
FORMATION m










H a






or

1- :zr
;, ___ =tO






FLORIDA GEOLOGICAL SURVEY


the well. The effects of earthquakes on water levels in wells 42-
19-1 and 44-25-39 are shown on the hydrographs in figure 34,
which were traced from the charts of continuous recording gages.
An earthquake in southern California, which occurred on July 21,
1952, had a magnitude of 7.5 (based on a comparative scale that
ranges from a minimum intensity of 1 to a maximum intensity of
10) and caused maximum water-level fluctuations of 0.85 foot
in well 42-19-1 and 0.46 foot in well 44-25-39. An earthquake
of 8.5 intensity near the east coast of Kamchatka, in Siberia, on
November 4, 1952, caused maximum water-level fluctuations of
0.86 foot in well 42-19-1 and 1.24 feet in well 44-25-39.
Daily changes in atmospheric pressure cause minor fluctuations
of artesian pressure head which are observable in most wells,
but these changes may be masked or modified by fluctuation due
to tides, local pumping, or other factors. The effects of
atmospheric-pressure changes on the water level in well 44-25-39
may be seen on the hydrographs in figure 34, even though these
fluctuations are probably modified somewhat by effects of ocean
tides and local discharge. The effects of changes in atmospheric
pressure on the water level in well 42-19-1, which is not affected
by local pumping or ocean tides, are shown also in figure 34. The


SFCRM- SELF-POTENTIAL ;J RELATIVE RESISTIVITY VELOCITY OF WATER LOR




1CO 'u



z




0~ n
0 .o
u


ZC ----- S ---- -- i* '' -- -1 -- ~ ~~


o ____ __ ___ ____ __ __ __


Figure 18. Graph showing well-exploration data for well 45-24-17.






REPORT OF INVESTIGATIONS NO. 21


periods of low atmospheric pressure in the early morning and
late afternoon are represented by high water levels. The highest
atmospheric pressures occur about noon and midnight and are
represented by the lowest water levels. The magnitude of the
fluctuations caused by changes in atmospheric pressure is generally


Figure 19. Graph showing well-exploration data for well 45-24-23.






FLORIDA GEOLOGICAL SURVEY


less than 0.1 foot but may be considerably greater during a
hurricane, when extremely low pressure may cause water levels
to rise several tenths of a foot.
Piezometric Surface: The contours on the map in figure 35 show
the configuration of the piezometric surface of the Floridan
aquifer in October 1952. The piezometric surface at that time
was more than 45 feet above mean sea level (msl) in the south-
eastern part of the area and from there sloped northwestward to
sea level in the vicinity of East Tampa, indicating a general
movement of the artesian water from southeast to northwest. In
the eastern part of the area, where interference by discharging
wells is negligible, the gradient of the piezometric surface is about
three to five feet per mile. The depressions in the piezometric
surface along the coast reveal the areas in which water was being
discharged from the aquifer. The deepest depressions, and hence
the areas of greatest discharge, are indicated by the closed
contours north of Ruskin and northwest of Sun City.
The depressions in the piezometric surface are probably the
result of discharge from wells. However, as most of the wells are
cased to depths of less than 50 feet, the depressions may reflect,
in addition, losses of artesian pressure head caused by upward
leakage of water from the Floridan aquifer into the shallow
formations through unused wells. The relatively large depression
indicated by the contours north of Adamsville is probably the result
of perennial withdrawal of large quantities of water for industrial
use and also some natural discharge from springs and seeps.


SFORMA- SELF POTENTIAL j RELATIVE RESISTIVITY rpm o current Omter) CITED
I TION 10m~, 25 ohms
.-.. 0 50 too 150 >
0- PLEISTOCPEE a ------ -- wl --20
PLIOCEE NE


z l "
U, xu.

if a
o o




L114- .
Fi

Figure 20. Graph showing well-exploration data for well 45-25-20.















0








CO


z
M


t-


Figure 21. Graph showing well-exploration data for well 45-26-2.





FLORIDA GEOLOGICAL SURVEY


The contours on the map in figure 36 represent the
piezometric surface in May 1953, during an extended period of
dry weather when large quantities of ground water were being
withdrawn for irrigation. The altitude of the piezometric surface
ranged from more than 40 feet above msl in the southeastern
part of the area to sea level in the vicinity of East Tampa. A
comparison of figures 35 and 36 shows that the piezometric
surface was generally about 5 feet lower in May than in October

< z WELL VELOCITY OF WATER CHLORIDE WATENT
45-26-3 (rpm of current meter) (parts per million)
<_ 50 100 150 0 50
0- PLEITCEN -
PUOCENE z

zz


-- 300- .
-'0 z
Li oZ
o L o
z_ 100- M--






200- r -
0 0





-300-


QC


Figure 22. Graph showing well-exploration data for well 45-26-3.









































Figure 23. Graph showing well-exploration data for well 46-24-7.


-J
hJ
W
-J
<

z
L4J
2

I
0

I.-
LU
LJ

LL
z

CL
QI
a


W






I
0



z

0
pL






40 FLORIDA GEOLOGICAL SURVEY

as a result of the combined drawdown of several hundred irrigation
wells.
Depth of Water Levels Below Land Surface: The area of
artesian flow and the approximate depth to water below the land
surface in wells that penetrate the Floridan aquifer, based on the
piezometric surface in May 1953, are shown in figure 37. The
area of flow includes a zone about one to three miles wide along
the coast, south of the Alafia River, and extends completely across
the Ruskin area along the valley of the Little Manatee River. It
includes also a narrow zone along the Alafia River in the vicinity
of Riverview. The depth to water below the land surface is


GEFORMA- WELL (rpm of current meter)
OGT TN 46-24-8


-1




-J






2 00-
0=
I-
LI





Q.




400-


IIlk


PLEISTOCENE
a PLIOCENE

Z |

X LL.


0 50 100 150 290 250





.)<


Figure 24. Graph showing well-exploration data for well 46-24-8. I
Figure 24. Graph showing well-exploration data for well 46-24-8.













IJJ
-J

w




-


-J
< 100-




W

I-,
w 200-
Lu.
2
I
I-
0

300-


Figure 25. Graphs showing well-exploration data for wells 46-24-12 and
46-24-17.


5 100

z




0
_J
200


Lii
I--

IJ


I.


z WELL VELOCITY OF WATER
S O 46-24-17 (rpm of current meter)
< 0 50 100
PLEISTOCENE -
PLIOCENE z
z z
So P





X

o p.
ll z
z P




o \



0


2 -


Z W






o j -












E FOM WELL VELOCITY OF WATER CHLO'RID CONTENT
AGE ON (rpm of current meter) (ports per mil lion)
82315 0 100 C 0 50 0
PLIOCENE


I --- -50


U I
0




---- 200



j ^ __ ____ --- -- .. -- --__^
0 -300


Figure 26. Graphs showing well-exploration data for wells 47-23-8 and 48-23-15.










^34 ,-- --------

<32 .

(n 30
z Well 42-19-1, I MILE WEST OF WIMAUMA
<, 28



S18_____________
< m 6
CMIl i V __ -- ______



L. 12 ..
10

Well 44-25-39,2 MILES NORTH OF RUS KIN I
1950 1951 1952 1953 1954 1955 1956

Figure 27. Hydrographs of wells 42-19-1 and 44-25-39.






44 FLORIDA GEOLOGICAL SURVEY

greatest in the east-central part of the area, where it is 50 feet
or more. Throughout most of the area, however, it is less than
25 feet.
Wells: About 650 wells were inventoried during this investi-
gation, and the information obtained is given in Information
Circular No. 22. As shown in plate 1, most of the wells are in
a zone about three to five miles wide along the coast, and most
of them flow, at least intermittently. They range in depth from
60 to more than 700 feet, but most of them are between 300 and


14
Well 42-28-9 2 ILES NORTH OF SUN CITY__
1 L L .Ll L I 1l i IllI1s 1 ....,1 5ll l.3.. 1 .1. lL L LLlL955

Figure 28. Hydrographs of wells 39-30-1, 40-27-7, 41-30-5, and 42-28-9.








REPORT OF INVESTIGATIONS No. 21


500 feet deep. They range in diameter from 2 inches to 18
inches, but most of them are 6 to 8 inches in diameter.
Surface casings are generally seated in the Hawthorn formation,
at depths of 20 to 75 feet, although some wells contain as much
as 200 feet of surface casing. In addition to the surface casing,


12
Well 44-25-5, I MILE NORT.-I OF RUKIN_

20






14

12
10 Well 46-24-7,,4-MILES NORTHEAST OF RUSKIN .







10
8 W8i 424--gq7i I, L ESNOTET OF ,RIV ,,, RU ,

1951 1952 1953 1954 1955

Figure 29. Hydrographs of wells 43-26-2, 44-25-5, 46-24-7, and 52-20-1.


-J
LU
>
LL)
_J

W

_J<
*UJ

>
UJZ

LJ
i-



4w
0


1-
LU
LU
UL.
z






46 FLORIDA GEOLOGICAL SURVEY

many wells are equipped with an inner casing extending to greater
depth to shut off caving sands.
The yields of the wells differ because of difference in the
permeability and thickness of the aquifer penetrated, the artesian
pressure head, and the size of the well bore. The irrigation wells
six inches or more in diameter, in the area of perennial artesian
flow, generally yield about 100 to 400 gpm.
Temperature: Measurements of the temperature of artesian
water from several hundred wells are given in Information Circular
No. 22 and a few are included in table 5. The temperature of the
water from the Hawthorn formation is generally between 740 and
76 F, and that from the Tampa formation is generally between
76 and 77.50F, depending upon the depth to the principal
producing zones. The temperature of the water from wells that
penetrate the Suwannee limestone and older formations is
generally about 780 to 790F, but it ranges from about 77.50 to
82: F, according to the depth and proportionate yield of the various
producing zones in these formations.

16 1 1 1 1 1 1 I I I I I I I I I I I I







S43-26-12, MILE NORTHWEST OF RUSKIN
CL 102










WATER LEVEL
0


SWell 43-26-26, MILE NORTHWEST OF RUSKIN____
CHLORIDE CONT NT









~ 95 195 12 ------ -954 -1------
Well 43-26-26, 1 MILE NORTHWEST OF RUSKIN

w:3 200
5 CHLORIDE CONT NT 0>
1951 1952 1953 1954 1955

Figure 30. Hydrographs of and chloride content of water from wells 43-26-12
and 43-26-26.








REPORT OF INVESTIGATIONS No. 21


QUANTITATIVE STUDIES


The withdrawal of water from an artesian aquifer creates a
depression in the piezometric surface in the vicinity of the point
of withdrawal. This depression generally has the approximate
form of an inverted cone and is referred to as the cone of
depression. The distance the piezometric surface is lowered at
any given point within this cone is known as the drawdown at

-i
S II -II ..- f l 1 1 11 1 i
-LJ



4 12

0 o

S WATER LEVEL
I C


-J









10-Well 44-26-31, 2-MILES NORTH OF RUSKIN
700 ....
40





200
cc



700














and 44-26-31. R
600 ----

n 500-----

J00--




CHLORIDE CONTENT
1951 1952 1953 1954 1 1955

Figure 31. Hydrographs of and chloride content of water from wells 44-25-38
and 44-26-31.






48 FLORIDA GEOLOGICAL SURVEY

that point. The size, shape, and rate of growth of the cone of
depression depends on several factors, including (1) the rate of
pumping, (2) the water-transmitting and storage capacities of
the aquifer, (3) the increase in recharge resulting from the
lowering of the piezometric surface, and (4) the decrease in
natural discharge due to the lowering of the piezometric surface.
The perennial yield of the artesian aquifer in the Ruskin area is
limited by the extent to which the piezometric surface can be
lowered without impairing the quality of the water or making
the cost of obtaining the water prohibitive.
The principal hydraulic properties of an aquifer are its
capacities to transmit and store water, for all aquifers serve as

S 20 | | | i i I1I 1 1 1 1 i111 11|1 I II I T 1 1 1 1 11 InIII I I I TI I I Ti


16 0






S WATER LEVEL
8


8Well 46-24-4, 3* MILES NORTHEAST OF RUSKIN
350 r .-. ..
CHLORIDE CONTENT
300
-j

0 200 -. -

150
1 oo




w 12

2 WATER LEAVE
8
z 00 Well 45-25-8,3 MILES NORTHEAST OF RUSKIN
9 CO CHLORIDE CONTENTbf
2 50 195L 1952 1953 1954 1955

Figure 32. Hydrographs of and chloride content of water from wells 45-25-8
and 46-24-4.







REPORT OF INVESTIGATIONS NO. 21


both conduits and reservoirs. An artesian aquifer functions
primarily as a conduit, transmitting water from places of recharge
to places of discharge; however, it is capable of storing water, by
expansion, or releasing water, by compression.
The coefficient of transmissibility is a measure of the capacity
of an aquifer to transmit water. In units commonly used by the
U. S. Geological Survey, it is the quantity of water, in gallons per
day (gpd), that will flow through a vertical section of the aquifer
one foot wide and extending the full saturated height, under a
unit hydraulic gradient, at the prevailing temperature of the
water. The coefficient of storage is a measure of the capacity of
an aquifer to store water, and is defined as the volume of water
released from or taken into storage per unit surface area of the
aquifer per unit change in head normal to that surface.


Well 48-23-19, + MILE WEST OF ADAMSVILLE


100 -- .

50Q CHLORIDE, CONTENT


K\KKA2~


iZIZSlI:


SA


WATER LEVEL
z Well 47-23-22, I-MILES SOUTHWEST OF ADAMSVILLE
150


CHLORIDE CON ENT -
50 IIIIIII Ii I IIIIII I lll I ll III IIIItl
50 1951 1952 1953 1954 1955

Figure 883. Hydrographs of and chloride content of water from wells 47-23-22
and 48-23-19.


~____I~I


I W I---


.v


I







FLORIDA GEOLOGICAL SURVEY


Figure 34. Effects of earthquakes and atmospheric-pressure changes on the
water levels in wells 42-19-1 and 44-25-39.


-J
t
> 14
LiL
_1

2
L13

z

12


Li
i,
W
U-
z
-j
W
Li
UJ 38
_j
CC 14
UJ
--


13



12


NOVEMBER 1952
1 2 3 4 5 6










Well 42-19-1









Well 44-25-39
tIII






REPORT OF INVESTIGATIONS NO. 21


In order to determine the transmissibility and storage
coefficients of the Floridan aquifer in the Ruskin area, a pumping
test was made in August 1955. Well 40-27-6, one-half mile east of
Sun City, was pumped at the rate of 650 gpm for a period of 31
hours, beginning at 9:15 a.m. on August 18 and ending at 4:12
p.m. on August 19. Throughout the period of pumping, water-
level measurements were made periodically in well 40-27-7, which


Figure 35. Map of the Ruskin area showing the piezometric surface of the
Floridan aquifer in October 1952.





FLORIDA GEOLOGICAL SURVEY


is 0.12 mile northwest of the pumped well, to determine the rate
and magnitude of drawdown. The coefficients obtained are not
necessarily correct for all parts of the area, but they are considered
to be representative.
The Theis graphical method, as described by Wenzel (1942, p.
87-89), was used to compute the transmissibility and storage
coefficients from the drawdown produced in well 40-27-7. This


Figure 36. Map of the Ruskin area showing the piezometric surface of the
Floridan aquifer in May 1953.






REPORT OF INVESTIGATIONS NO. 21


method relates the drawdown in the vicinity of a pumping well
to the rate and duration of discharge and is based on several
simplifying assumptions which include the following: (1) the
aquifer has an indefinite areal extent, (2) the aquifer is
homogeneous and transmits water with equal facility in all
directions, (3) the discharge well obtains water from the full
thickness of the aquifer, (4) the coefficient of transmissibility is


Figure 37. Map of the Ruskin area showing area of artesian flow and depth
of water level below land surface.






FLORIDA GEOLOGICAL SURVEY


constant at all places and at all times, (5) the discharge well has
an infinitesimal diameter, and (6) water taken from storage by
the decline in water level is discharged instantaneously with the
decline in head.
The observed data for well 40-27-7 matched against the type
curve, as shown in figure 38, yielded the following figures:
Where W (u) = 1.0, s = 0.65
and where u = 0.1, t/r2 = 1.0 x 10-7
114.6 QW(u)
These figures inserted in the formulas T = 114.6 QW--(u)
s
uTt
and S = 1.87 r- give a transmissibility coefficient of 114,600 gpd/ft
and a storage coefficient of .0006.

QUALITY OF WATER

The water that falls on the earth's surface as rain or snow is
practically free of mineral matter except for very small quantities
of atmospheric gases and dust. Therefore, the mineral constituents
and the degree of mineralization of ground water depends generally

1 :---------------------------------10.






0 -1.0
j >0650gpm
4 M W(u) 10 u 0.1; W(u)1.0
~ 1 s 0.65; t/rtI.0XI0'

ST 114.6 x 650 x 10
S / 0.65
T Te114,600 gpd/fl.
5 -, _______ __. uTt 0.1xi14.600x10xI1 A.,


Figure 38. Logarithmic plot of drawdown in well 40-27-7 versus t/r2.






REPORT OF INVESTIGATIONS NO. 21


upon the composition and solubility of the soil and rocks through
which the water passes. In some places, mineralization of ground
water may result from the mixing of relatively fresh water with
highly mineralized, residual sea water within the water-bearing
formations.
Chemical analyses of water samples from 29 selected wells in
the Ruskin area (fig. 39) were made by the Quality of Water


Figure 39 Map of the Ruskin area showing wells sampled for chemical
analysis.






FLORIDA GEOLOGICAL SURVEY


Branch of the U. S. Geological Survey. The results of these
analyses are shown in table 5 and are discussed briefly -below.
The concentrations of mineral constituents are given in parts
per million (ppm)-1 ppm is approximately equivalent to 8.34
pounds per million gallons of water. The specific conductance is
expressed in micromhos at 250 C, and the hydrogen-ion content in
standard pH units. The concentration limits given for the ions,
unless otherwise stated, are taken from standards for drinking
water prescribed by the U. S. Public Health Service (1946).
Calcium (Ca) is dissolved principally from limestone, which is
predominantly calcium carbonate, by water containing carbon
dioxide. Calcium is a principal cause of hardness in water.- As
indicated by the analyses, the water from the Floridan aquifer
in the Ruskin area has a calcium content ranging from 81 to
275 ppm.
Magnesium (Mg) is dissolved principally from dolomite or
dolomitic limestone and, like calcium, is a major cause of hardness
in water. As magnesium is one of the principal mineral con-
stituents of sea water, ground water that has been contaminated
by sea water usually has a relatively high magnesium content.
The water from the Floridan aquifer in the Ruskin area has a
magnesium content ranging from 33 to 109 ppm. (See table 5.)
Sodium (Na) and potassium (K) are dissolved in small
amounts from many types of rocks, but they constitute only a small
to moderate part of the total mineral content of fresh ground
water. The sodium content of water that has been contaminated
by sea water is generally high, as sea water is principally a solution
of sodium chloride. Water from the Floridan aquifer in south-
western Hillsborough County contained 7 to more than 100 ppm
of sodium and potassium.
Bicarbonate (HCO,) in ground water results from the solution
of limestone and other carbonate rocks. Hardness caused by
calcium and magnesium equivalent to the carbonate and
bicarbonate is known as carbonate hardness in water. The
bicarbonate content of water from the Floridan aquifer is
relatively high, ranging from about 150 to more than 225 ppm.
Sulfate (SO4) in ground water may be due to the oxidation
of sulfide minerals or the solution of sulfate salts in the formations.
Large quantities of sulfates in water may impart a bitter taste.
and have a laxative effect. Sulfates of calcium and magnesium
cause boiler scale. The concentration limit of sulfate in drinking
and culinary water is considered to be about 250 ppm. The sulfate
content of water from the Floridan aquifer in southwestern





TABLE 5. Chemical Analyses of Artesian Water from Wells in the Ruskin Area
(Analyses by U. S. Geological Survey; chemical constituents in parts per million)









89-18-1 4-4-55 ... ...... 81 83 6.7 158 192 16 .... .... 480 338 696 8.1 82
39-30-5 4-8-55 .... ...... 110 50 8.3 178 800 28 .... .... 692 480 950 7.8 78.3
40-27-3 4-7-55 .... ... 104 48 13 182 275 35 .... .... 656 457 894 7.7 78.2
40-29-4 4-8-55 .... ..... 101 43 16 188 260 28 .... .... 684 429 876 7.9 77
40-29-5 4-8-55 .... ...... 84 39 25 200 215 25 .... .... 554 370 806 7.9 76
40-29-24 4-7-55 .... .-.. 90 44 12 194 232 22 .... .... 594 406 827 7.9 77
41-30-5 4-7-55 .... ...... 110 50 17 182 820 24 .... .... 706 480 943 7.9 77
42-28-8 4-7-55 .... ..... 97 43 14 190 255 21 .... .... 606 419 846 7.9 77 0
42-28-9 4-7-55 .... ...... 117 52 12 188 832 28 .. .... 718 506 987 7.9 78.5 Z
43-24-6 4-14-55 .... ...... 105 46 9.9 190 272 24 .... .... 632 451 885 7.9 78.1
48-24-9 4-14-55 .... ...... 83 38 10 198 185 22 .... .... 536 363 745 8.0 76 z
43-26-2 4-7-55 .--... ...... 115 51 11 180 330 21 .. .... 702 496 950 7.8 78
43-26-12 8-9-53 21 0.10 234 96 74 170 678 202 0.7 0.9 1,560 978 1,920 7.5 79
43-27-6 4-14-55 .... ...... 135 59 10 182 405 22 .... .... 854 580 1,090 7.9 78
43-28-4 4-14-55 ..... 104 53 12 190 805 22 .... .... 674 478 938 7.9 77
44-24-1 7-27-55 ..... 81 36 21 210 165 26 .... .... 484 850 686 7.3 76.5
44-25-1 4-8-55 ....---- ...... 95 48 7.4 192 232 22 .... .... 590 414 825 7.9 77
44-25-88 4-8-55 ... ...... 177 75 43 172 475 148 ... .... 1,230 750 1,590 7.6 79
44-26-25 7-27-55 .... ...... 135 55 18 186 388 25 .... .... 800 568 1,010 7.4 77.5
44-26-31 3-5-58 17 .69 199 81 89 168 582 190 .9 .8 1,350 830 1,780 7.3 80 m
____________________ _______________________ -








Table 5 (Continued)


z z




Iw Z l- L


.6
.14
0.06




.28


105
276
122
87
162
161
177
206
170


47
109
52
38
69
60
68
79
65


16
108
16
14
86
15
16
76
52


156
162
178
228
170
198
181
176
172


812
821
364
188
475
455
525
610
510


25
270
19
14
94
28
26
157
88


653
1,840
750
531
1,100
909
1,010
1,340
1,080


456
1,140
518
878
688
648
721
889
693


870
2,800
956
718
1,420
1,110
1,220
1,720
1,870


78



77.5
76
77
79.5
77


45-24-7
46-24-4
46-24-7
47-20-1
47-28-22
48-22-5
48-22-7
48-23-8
48-28-19


7-27-45
8-6-58
8-10-538
8-6-538
4-8-55
7-27-55
7-27-55
7-27-55
3-6-58


*i,






REPORT OF INVESTIGATIONS NO. 21


Hillsborough County is relatively high, ranging from about 165
to more than 800 ppm. Throughout the coastal area, the sulfate
content is more than 250 ppm (fig. 40).
Chloride (Cl) in small quantities is dissolved from most soils
and rocks and is found in large quantities in ground water that
has been contaminated by sea water. Chloride salts do not
generally decrease the potability of water except when present in


Figure 40. Map of the Ruskin area showing-the sulfate content of water from
the Floridan aquifer.





FLORIDA GEOLOGICAL SURVEY


quantities sufficient to cause a salty taste. The chloride content
of water from the Floridan aquifer in the Ruskin area ranges
from about 15 ppm to more than 1,000 ppm. The chloride content
of water from the Tampa formation is shown in figure 41, and
that from the Suwannee and older formations is shown inj figure
42. The chloride content of the artesian water is discussed in
more detail under the heading "Salt-Water Contamination."
Iron (Fe) occurs in almost all rocks, but the quantity of iron


Figure 41. Map of the Ruskin area showing the chloride content of water
from the Tampa formation.






REPORT OF INVESTIGATIONS No. 21


dissolved by ground water is relatively small in comparison with
the quantity of more soluble minerals. Water containing more
than about 0.3 ppm of iron causes stains on fixtures,
utensils, and clothing; and water containing 0.5 to 1.0 ppm has an
objectionable taste. Iron can generally be removed from water by
aeration and filtration. The iron content of water from six wells
in the Ruskin area ranged from 0.06 to 0.69 ppm (table 5).
Fluoride (F) is present in minor amounts in most ground


Figure 42. Map of the Ruskin area showing the chloride content of water
from the Suwannee limestone and older formations.






FLORIDA GEOLOGICAL SURVEY


water. Water containing fluoride in excess of 1.5 ppm may cause
mottling of children's teeth during their formation (Cox and Ast,
1951, p. 641-648). In concentrations of 1.5 ppm or less, fluoride is
recognized as being beneficial to dental health through reducing
tooth decay and is added to many public water supplies for this
reason. As shown in table 5, the fluoride content of water from
six wells that penetrate the Floridan aquifer ranged from 0.4
ppm to 1.2 ppm.
The dissolved-solids content of ground water represents the
approximate amount of mineral matter in solution. Water
containing less than 500 ppm of dissolved solids is generally of
good chemical quality, according to the U. S. Public Health Service
drinking-water standards, and water containing as much as 1,000
ppm may be used for public supplies if a less mineralized water is
not available. The concentration of dissolved solids in water from
the Floridan aquifer in the Ruskin area ranges from slightly less
than 500 ppm to more than 1,800 ppm. (See fig. 43 and table 5.)
The hardness of water is due principally to the salts of calcium
and magnesium. The most noticeable effects of hardness are the
formation of curds and the lack of suds when soap is added to
the water, and the formation of a scale in vessels in which the
water is heated. Water having a hardness of 60 ppm or less is
generally satisfactory for most purposes. Water having a hardness
between 60 and 120 ppm requires treatment for many industrial
uses. Water having a hardness of more than 200 ppm is commonly
softened for domestic and some other uses, although many private
and some public supplies having a hardness of more than 500 ppm
are not treated. The hardness of water from the Floridan aquifer
in the Ruskin area ranges from about 350 ppm in the eastern part
to more than 1,100 ppm near the coast (fig. 44).
The specific conductance of water is a measure of its capacity
to conduct an electric current and depends upon the concentration
and ionization of the minerals in solution. It indicates in a general
way the relative mineralization of the water. As shown in table
5, the specific conductance of water from the Floridan aquifer in
the Ruskin area ranged from 686 to 2,300 micromhos.
Hydrogen sulfide (H2S) is a gas that gives water an objection-
able odor and may cause corrosion of plumbing. Water containing
it is often referred to as "sulfur water." Aeration is generally the
most practical method of treatment. No analyses were made of
the hydrogen sulfide content of water from the Floridan aquifer
in the Ruskin area, but the odor of the gas is detectable in water
from most wells.







REPORT OF INVESTIGATIONS NO. 21


The pH of a water indicates the instantaneous concentration of
hydrogen ions. Water that has a pH of 7.0 is said to be neutral.
Water having a pH of less than 7.0 is acidic and may be corrosive;
water having a pH greater than 7.0 is alkaline and not generally
corrosive. The water from the Floridan aquifer in the Ruskin
area is slightly alkaline, the pH ranging from 7.3 to 8.1.


,,..- .., .. ,',. \ / .*-' .."-,
SILLSBOROU COUNTY ,-
MANATEE COUNTY
.. ,


Figure 43. Map of the Ruskin area showing the dissolved-solids content of
water from the Floridan aquifer.






FLORIDA GEOLOGICAL SURVEY


SALT-WATER CONTAMINATION

In coastal areas underlain by permeable water-bearing
formations that are hydraulically connected to the sea, the depth
to salt water is directly related to the height of the fresh ground
water above sea level. The density of fresh water is slightly less
than that of sea water, so that fresh water floats on sea water in


Figure 44. Map of the Ruskin area showing the hardness of water from the
Floridan aquifer.






REPORT OF INVESTIGATIONS No. 21


much the same way that ice floats on water. The specific gravity
of sea water is generally about 1.025, whereas that of fresh water,
for practical purposes, is 1.000. Thus, with these specific gravities
a column of sea water 40 feet high will exactly balance a column
of fresh water 41 feet high. This principle was first applied to
the hydrology of coastal areas by Badon Ghyben and Alexander
Herzberg (Brown, 1925, p. 16) who found that for each foot of
fresh water above sea level there was approximately 40 feet of
fresh water below sea level. Although the 40-to-1 ratio is strictly
applicable only under a condition of static equilibrium, it applies
approximately in coastal aquifers, except in areas very close to
the shore.
Salty water is present in the Floridan aquifer at relatively
shallow depths throughout most of the coastal area of Florida. At
some places, the lowering of the artesian head by withdrawal of
large quantities of water from wells has caused the encroachment
of sea water into the aquifer. In most of the area, however, the
artesian pressure head is sufficiently high to prevent encroachment
of water directly from the sea; thus, the widespread salty water
probably represents residual sea water that entered the aquifer
prior to Recent time.
The Floridan aquifer was partly filled with sea water several
times during the interglacial stages of the Pleistocene epoch, when
the sea rose above the present level. Since the last recession of
the sea, the circulation of fresh water through the aquifer has been
gradually diluting and flushing out the salty water. In much of the
coastal area, however, a part or all of the water-bearing formations
still contain water that is too salty for most uses, although it is
considerably less salty than sea water. Excessive lowering of the
head may reverse the flushing action and cause lateral migration
of sea water into the aquifer. It may also cause an upward
migration of the salty water from the lower zones of the aquifer
into the upper part, except where such migration is retarded by
relatively impermeable strata.

RELATIVE SALINITY OF THE ARTESIAN WATER

The dissolved mineral constituents of sea water consist pre-
dominantly of chloride salts; thus, an abnormally high chloride
content of ground water is generally a reliable indicator of salt-
water contamination. Water samples from about 400 wells were
analyzed in order to determine the chloride content of the water
from the Floridan aquifer in the Ruskin area. The results of





FLORIDA GEOLOGICAL SURVEY


these analyses are included in table 5 and are shown by symbols
in figures 41 and 42.
The chloride content of the water from the Floridan aquifer
is about 10 ppm in western Polk County and about 15 ppm in
eastern Hillsborough County. It increases gradually toward
Tampa Bay, in the direction in which the water is moving.
Throughout most of the Ruskin area, the chloride content of water
from the Floridan aquifer is about 20 to 30 ppm, but in some parts
of the coastal area it ranges from 31 to more than 500 ppm.
The chloride content of water from the Tampa formation is
shown in figure 41. Most of the wells that yield water of relatively
high chloride content are in a narrow zone that extends along, the
coast from the vicinity of Adamsville to the northern boundary of
the area. The chloride content of water from these wells ranges
from less than 50 to more than 500 ppm. A few wells south of
Adamsville yield water from the Tampa containing about 35 to 40
ppm of chloride. The relatively high chloride content of the water
from these wells may represent contamination from nearby wells
that penetrate the deeper formations.
Figure 42 shows the chloride content of water from wells that
penetrate the Suwannee limestone, the Ocala group, and the Avon
Park limestone. Most of the wells that yield water of relatively
high chloride content are in a zone about a mile wide that extends
along the coast from the Little Manatee River to the northern
boundary of the area. Wells that penetrate the Suwannee limestone
in this zone yield water having a chloride content ranging from
about 30 ppm to more than 800 ppm, and wells that penetrate the
Ocala group and Avon Park limestone yield water having a chloride
content of more than 1,000 ppm. A few wells south of the Little
Manatee River yield water whose chloride content is 35 to 65 ppm.
In order to determine the relative salinity of the water from
the different producing zones in the aquifer, water samples were
collected at several depths in selected wells with a deep-well
sampler and measurements of the electrical resistivity of the
water at different depths were made in several wells. The chloride
content of water samples collected in wells is shown graphically
in figures 9-12, 14-18, 20-23, 26, and 45-47. The results of
resistivity measurements also are included in figures 14, 16, and 45.
As indicated by these graphs, the salty water enters the wells
from the deep producing zones and is diluted by fresher water
from other producing zones as it moves up the well bore. For
example, the analyses of samples collected in well 44-25-42 (fig.
14) show that the chloride content of the water from the Suwannee














LiJ

-' 100 -,
z 0

Lii

-- 00
Z __ __ __ ___ --____ -4





0 00
x200 2 7---- f----- -- -- ---- ___ __

* 0 ---- -^--, -
LJ W



400- -
Figure 45. Graph showing well-exploration data for well 44-25-28.
0. W



400- 0___

Figure 45. Graph showing well-exploration data for well 44-25-28.






DEPTH, IN FEET REFERRED TO MEAN SEA LEVEL


OLIGOCENE MIO SCENE 9 m "

SUWANNEE TAMPA -t r S
LIMESTONE FORMATION a, mz





-I
2 -
\-I


----------- WELL
6 Causing'\ 4-23-8
m

-t
^ ^ ^i/l,, .N
*V 'W /1^ i











y ---- s






REPORT OF INVESTIGATIONS NO. 21


limestone was 225 ppm at a depth of 370 feet and 135 ppm at a
depth of 320 feet. The sharp increase in the resistivity from about
207 milliohms at 330 feet to about 256 milliohms at 315 feet in-
dicates that most of the fresh water entered the well in this
interval.
Periodic analysis of water samples shows that the chloride
content of the water varies with changes in artesian pressure
head. A decrease in head is generally accompanied by an increase
in chloride content, and vice versa. This relationship indicates
that the lowering of the head causes a vertical movement of salty
water from the deeper formations. It may also reflect variations
in the proportion of the total yield of the well that is obtained
from each formation or producing zone. During periods of heavy
withdrawal, the artesian head of the Tampa formation may be
slightly less in some places than the head of the Suwannee lime-
stone or deeper formations. This difference in head would increase
the proportional yield of the deeper formations and increase the
chloride content of the water obtained.

SOURCES OF CONTAMINATION
As indicated by the contours in figures 35 and 36, the mean
artesian head along the coast ranges from about sea level in the
area north of the Alafia River to about 18 feet above sea level
near the Manatee County line. If the 40-to-1 ratio applies, the
depth below sea level to salt water in the aquifer would be nearly
zero at East Tampa and more than 600 feet south of the Little
Manatee River. In the area south of Adamsville, the mean
artesian head is sufficiently high to prevent encroachment of water
from the sea into the Suwannee limestone (see fig. 4) ; thus, the
occurrence of relatively salty water in the Suwannee or in the
Tampa formation probably represents residual sea water that
entered the formations during Pleistocene time.
Studies of current-meter traverses show that the Floridan
aquifer contains permeable zones separated by relatively
impermeable beds of considerable thickness. The permeable zones
tapped by most wells in the area are generally less than 450 feet
below sea level. The relatively impermeable beds beneath the
principal water-bearing zones retard or prevent upward migration
of salty water from the deeper formations.
The salinity of the water in the Suwannee limestone and Tampa
formation in the area north of Adamsville is probably due in
part to residual Pleistocene sea water and in part to encroachment
of water from Tampa Bay during recent years.






FLORIDA GEOLOGICAL SURVEY


The Tampa formation is at or near the land surface in the
northern Tampa Bay area, and in 1955 large quantities of artesian
water were being discharged from the formation through springs
and seeps. The northern part of Tampa Bay is apparently the
center of a large area of natural discharge which has existed for
many thousands of years. The withdrawal of large quantities of
water from wells during recent years has lowered the piezometric
surface to sea level at some places, permitting salt water from
Tampa Bay to enter the upper part of the aquifer.
The withdrawal of large quantities of salt water at East Tampa,
through wells that penetrate the Avon Park limestone, has created
a cone of depression which extends below sea level in the vicinity
of the pumped wells but is relatively small in areal extent. The
limited extent of this cone is probably due to the salvage of natural
discharge and the induction of recharge from Tampa Bay. The
quantity of water discharged from the wells is apparently near
equilibrium with the recharge from Tampa Bay and the intercepted
natural discharge, so that the artesian head is relatively stable;
however, salt water is steadily encroaching.

SUMMARY AND CONCLUSIONS

The investigation of the ground-water resources of the Ruskin
area of Hillsborough County involved collecting and evaluating data
from about 650 wells. The principal results of the study are
summarized below:
1. The Ruskin area is underlain by a thick section of Tertiary
limestones whose upper surface ranges in depth from about sea
level in the northern part of the area to about 250 feet below sea
level in the southern part. The limestone formations penetrated
by water wells include the Avon Park limestone and Ocala group
of Eocene age, the Suwannee limestone of Oligocene age, and the
Tampa formation of early Miocene age. The Tampa is overlain by
the Hawthorn formation of middle Miocene age which consists
of sandy, calcareous clay and thin beds of limestone and sand.
2. The Suwannee limestone and Tampa formation are the
principal sources of artesian water in the area, although the deeper
limestones yield water to a few wells. The water in these
formations occurs in permeable zones which are generally separated
by relatively impermeable layers of considerable thickness. The
water is replenished by rainfall in western Polk County and
eastern Hillsborough County and is confined under pressure by
the relatively impermeable strata within the formations and by







REPORT OF INVESTIGATIONS No. 21


the overlying Hawthorn formation. The beds of limestone and
sand in the Hawthorn are the source of many domestic water
supplies.
3. Water-level records show that significant fluctuations of
artesian pressure head result from the daily and seasonal variations
in withdrawal of water from wells. During periods of heaviest
withdrawal, the piezometric surface is lowered about 4 feet
throughout the area and more than 8 feet at some places. The
artesian pressure head declined progressively in the coastal area
during a period of extensive agricultural development from 1950
to 1952. Since 1952 the seasonal fluctuations in the coastal area
have decreased in magnitude and a slight progressive increase in
artesian pressure head has occurred locally as a result of a decrease
in withdrawals. In wells not affected by local use of water the
artesian pressure head declined progressively in 1955-56.
4. Analysis of data collected during a pumping test indicates
that the artesian aquifer has a transmissibility coefficient of about
115,000 gpd/ft and a storage coefficient of 0.0006.
5. Chemical analyses show that the mineral content of the
water in the Suwannee limestone and Tampa formation is lowest
in the eastern part of the area and progressively higher toward
Tampa Bay, in the direction in which the water is moving.
Concentrations of dissolved solids range from less than 500 ppm
in the eastern part of the area to more than 1,800 at some places
along the coast, and the hardness ranges from about 350 ppm to
more than 1,000 ppm. The water in the Suwannee limestone is
somewhat more mineralized than the water in the Tampa, and that
in the Eocene formations probably is much more mineralized than
the water in the Suwannee limestone, particularly in the coastal
area.
6. The chloride content of the artesian water is about 20 to 30
ppm throughout most of the area. In a narrow zone along the
coast north of the Little Manatee River, many wells yield water
having a considerably higher chloride content, indicating that the
artesian water has been contaminated to some extent by salty
water.
In the area south of Adamsville, salt-water contamination is
apparently due to residual sea water that entered the aquifer
during Pleistocene time, as the mean artesian head along the coast
is sufficiently high to prevent encroachment of water from Tampa
Bay into the Suwannee limestone and Tampa formation. The
circulation of fresh water through the aquifer has flushed most of
the sea water from these formations, although some water from the






FLORIDA GEOLOGICAL SURVEY


Suwannee limestone has a chloride content of several hundred
ppm. The water in the Tampa formation generally contains about
30 ppm of chloride or less.
Contamination in the vicinity of Adamsville and northward is
probably due to both residual Pleistocene sea water and
encroachment of water from Tampa Bay during recent decades.
The northern part of Tampa Bay is the approximate center of an
area of natural discharge that has existed for many thousands of
years. The withdrawal of water through wells in recent decades
has lowered the artesian head to sea level at some places, permitting
water from Tampa Bay to enter the upper part of the Floridan
aquifer. Some wells that penetrate the Eocene limestones yield
water as salty as sea water.
Periodic analysis of water from selected wells shows that the
chloride content varies with significant changes in artesian pres-
sure head. The chloride content generally increases as the artesian
head declines, and vice versa. This relationship may reflect
variations in the proportion of the total yield of the well that is
obtained from each formation or producing zone, or it may indicate
that a decline in artesian pressure head results in upward
encroachment of salty water from the deeper formations. The
relatively impermeable strata in the aquifer probably retard or
prevent an upward movement of the salty water throughout most
of the area, as only a few wells have yielded water that has
shown a progressive increase in chloride content and the
contaminated zone has not expanded during the period of record.
An appreciable lowering of the artesian pressure head in the
coastal area, however, would eventually result in lateral
encroachment. It might result also in vertical encroachment in
areas where the impermeable strata are breached or absent.

REFERENCES

Applin, Esther R. (see Applin, Paul L.)
Applin, Paul L.
1944 (and Applin, Esther R.) Regional subsurface stratigraphy and
structure of Florida and southern Georgia: Am. Assoc. Petroleum
Geologists Bull., v. 28, no. 12, p. 1673-1753.
Ast, D. B. (see Cox, C. R.)
Black, A. P.
1951 (and Brown, Eugene) Chemical character of Florida's waters:
Florida State Board of Cons., Division Water Survey and Re-
search Paper 6.






FLORIDA GEOLOGICAL SURVEY


The Tampa formation is at or near the land surface in the
northern Tampa Bay area, and in 1955 large quantities of artesian
water were being discharged from the formation through springs
and seeps. The northern part of Tampa Bay is apparently the
center of a large area of natural discharge which has existed for
many thousands of years. The withdrawal of large quantities of
water from wells during recent years has lowered the piezometric
surface to sea level at some places, permitting salt water from
Tampa Bay to enter the upper part of the aquifer.
The withdrawal of large quantities of salt water at East Tampa,
through wells that penetrate the Avon Park limestone, has created
a cone of depression which extends below sea level in the vicinity
of the pumped wells but is relatively small in areal extent. The
limited extent of this cone is probably due to the salvage of natural
discharge and the induction of recharge from Tampa Bay. The
quantity of water discharged from the wells is apparently near
equilibrium with the recharge from Tampa Bay and the intercepted
natural discharge, so that the artesian head is relatively stable;
however, salt water is steadily encroaching.

SUMMARY AND CONCLUSIONS

The investigation of the ground-water resources of the Ruskin
area of Hillsborough County involved collecting and evaluating data
from about 650 wells. The principal results of the study are
summarized below:
1. The Ruskin area is underlain by a thick section of Tertiary
limestones whose upper surface ranges in depth from about sea
level in the northern part of the area to about 250 feet below sea
level in the southern part. The limestone formations penetrated
by water wells include the Avon Park limestone and Ocala group
of Eocene age, the Suwannee limestone of Oligocene age, and the
Tampa formation of early Miocene age. The Tampa is overlain by
the Hawthorn formation of middle Miocene age which consists
of sandy, calcareous clay and thin beds of limestone and sand.
2. The Suwannee limestone and Tampa formation are the
principal sources of artesian water in the area, although the deeper
limestones yield water to a few wells. The water in these
formations occurs in permeable zones which are generally separated
by relatively impermeable layers of considerable thickness. The
water is replenished by rainfall in western Polk County and
eastern Hillsborough County and is confined under pressure by
the relatively impermeable strata within the formations and by







REPORT OF INVESTIGATIONS NO. 21


Brown, Eugene (see Black, A. P.)
Brown, J. S.
1925 A study of coastal ground water, with special reference to Con-
necticut: U. S. Geol. Survey Water-Supply Paper 537.
Collins, W. D.
1928 (and Howard, C. S.) Chemical character of waters of Florida:
U. S. Geol. Survey Water-Supply Paper 596-G.
Cooke, C. W. (also see Parker, G. C.)
1945 Geology of Florida: Florida Geol. Survey Bull. 29.
Cox, C. R.
1951 (and Ast, D. B.) Water fluoridation-a sound public health prac-
tice: Am. Water Works Assoc. Jour., v. 43, no. 8, p. 641-648.
Ferguson, G. E. (see Parker G. G.)
Gunter, Herman (see Sellards, E. H.)
Howard, C. S. (see Collins, W. D.)
Love, S. K. (see Parker G. G.)

MacNeil, F. S.
1949 Pleistocene shorelines in Florida and Georgia: U. S. Geol. Survey
Prof. Paper 221-F.
Matson, G. C.
1913 (and Sanford, Samuel) Geology and ground waters of Florida:
U. S. Geol. Survey Water-Supply Paper 319.
Parker, G. G.
1944 (and Cooke, C. W.) Late Cenozoic geology of southern Florida
with a discussion of the ground water: Florida Geol. Survey
Bull. 27.
1950 (and Stringfield, V. T.) Effects of earthquakes, trains, tides,
winds, and atmospheric pressure changes on water in the geo-
logic formations of southern Florida: Econ. Geology, v. 45, no.
51, p. 441-460.

1955 (and Ferguson, G. E., Love, S. K., and others) Water resources
of southeastern Florida, with special reference to the geology and
ground water of the Miami area: U. S. Geol. Survey Water-
Supply Paper 1255.

Puri, Harbans
1953 Zonation of the Ocala group in peninsular Florida: Jour. Sedi-
mentary Petrology, v. 23, p. 130.

Sanford, Samuel (see Matson, G. C.)

Sellards, E. H.
1913 (and Gunter, Herman) The artesian water supply of eastern and
southern Florida: Florida Geol. Survey 5th Ann. Rept.






FLORIDA GEOLOGICAL SURVEY


Suwannee limestone has a chloride content of several hundred
ppm. The water in the Tampa formation generally contains about
30 ppm of chloride or less.
Contamination in the vicinity of Adamsville and northward is
probably due to both residual Pleistocene sea water and
encroachment of water from Tampa Bay during recent decades.
The northern part of Tampa Bay is the approximate center of an
area of natural discharge that has existed for many thousands of
years. The withdrawal of water through wells in recent decades
has lowered the artesian head to sea level at some places, permitting
water from Tampa Bay to enter the upper part of the Floridan
aquifer. Some wells that penetrate the Eocene limestones yield
water as salty as sea water.
Periodic analysis of water from selected wells shows that the
chloride content varies with significant changes in artesian pres-
sure head. The chloride content generally increases as the artesian
head declines, and vice versa. This relationship may reflect
variations in the proportion of the total yield of the well that is
obtained from each formation or producing zone, or it may indicate
that a decline in artesian pressure head results in upward
encroachment of salty water from the deeper formations. The
relatively impermeable strata in the aquifer probably retard or
prevent an upward movement of the salty water throughout most
of the area, as only a few wells have yielded water that has
shown a progressive increase in chloride content and the
contaminated zone has not expanded during the period of record.
An appreciable lowering of the artesian pressure head in the
coastal area, however, would eventually result in lateral
encroachment. It might result also in vertical encroachment in
areas where the impermeable strata are breached or absent.

REFERENCES

Applin, Esther R. (see Applin, Paul L.)
Applin, Paul L.
1944 (and Applin, Esther R.) Regional subsurface stratigraphy and
structure of Florida and southern Georgia: Am. Assoc. Petroleum
Geologists Bull., v. 28, no. 12, p. 1673-1753.
Ast, D. B. (see Cox, C. R.)
Black, A. P.
1951 (and Brown, Eugene) Chemical character of Florida's waters:
Florida State Board of Cons., Division Water Survey and Re-
search Paper 6.






74 FLORIDA GEOLOGICAL SURVEY

Stringfield, V. T. (also see Parker, G. C.)
1936 Artesian water in the Florida peninsula: U. S. Geol. Survey
Water-Supply Paper 773-C.
U. S. Public Health Service
1946 Drinking water standards: Public Health Repts., v. 61, no. 11,
p. 371-384.
Vernon, R. 0.
1951 Geology of Citrus and Levy counties, Florida: Florida Geol. Sur-
vey Bull. 33.
Wenzel, L. K.
1942 Methods for determining permeability of water-bearing materials,
with special reference to discharging-well methods, with a sec-
tion on direct laboratory methods and bibliography on perme-
ability and laminar flow, by V. C. Fishel: U. S. Geol. Survey
Water-Supply Paper 887.





TABLE 6. Measurements of Water Levels in Wells in the Ruskin Area
(All measurements shown in feet above or below' (-) measuring point)

Well Date Water Date Water Date Water Date Water
Number level level level level

38-81-5 8-22-52 4.2 12-23-52 8.2 8-17-53 12.6
9-29-52 8.6 5-18-58 5.8 9-14-54 12.0

89-18-1 9- 7-51 10.6 5-18-568 4.9 4- 4-55 8.0
7- 2-52 9.0 9-80-54 11.1

89-81-5 2- 1-51 11.8 8-28-51 10.7 5-18-52 8.6

40-20-1 2-19-51 -28.5 3-26-51 -24.2 6-11-51 -25.75 8- 4-53 -23.9
2-26-51 -24.5. 4-17-51 -28.0 7-11-51 -24.84 4-14-58 -25.7
8-16-51 -25.8 5- 4-51 -22.7 9- 8-51 -22.80 5-21-568 -26.75

40-24-1 2-19-51 20.1 8-16-51 22.9 4-27-51 22.5 9- 7-51 25.9
2-26-51 24.9 8-26-51 24.0 6-11-51 20.6 5-16-52 18.9

40-27-4 5-18-52 -8.75 10-10-52 1.8 8-17-53 0.7 6- 8-55, -8.18

40-28-2 11-26-51 -6.15 12- 3-51 -8.27 12-14-51 -10.50 9-29-52 -11.25

40-30-1 8-28-51 8.1 5-18-52 8.8 5-18-53 5.6
9- 7-51 7.0 10-18-52 18.2


0




0

0
~i2
z
'p







Table (, (Continued)
(All measurements shown in feet above or below ( ) measuring point)


Water
level

--11.52
-18.7


Well
Number

41-24-1


41-29-23


Date


6-23-52
10-10-52


10-22-52
11-18-52
12-22-58


Water
level

-14.65
-12.3


Date


Water
level


5-18-53 -19.2


1-80-58
5-21-53
8-17-58


41-80-6 2-19-51 9.3 3-16-51 9.9 4-17-51 14.6
2-26-51 8.3 3-26-51 12.7 6-11-51 9.9


3.0
4.6

10.1
1.78

8.9
4.2
4.6
-2.15


5-13-52


10-10-52
6- 8-55

10-13-52
5-14-53

6-23-52
8-25-52
9-29-52
10-10-52


2.5

6.8
2.45

11.2
8.5

4.6
2.5
5.7
7.0


10-10-52

9-27-55


9.2

5.7


5-18-53 2.9


10-22-52
1-30-58
9-30-54
6- 8-55


7.6
5.5
8.0
'1.05


Date


10-15-58
11-20-53
6- 8-55


Water
level





1.2
3.2
4.62


9- 7-51 12.2
10-10-52 13.7

10-22-52 10.3


7-27-55


0.7
-4.57
5.7


Date


9- 7-51
5-16-52


3-28-51
5-13-52
10-10-52


41-80-13


42-25-13


42-26-12


48-24-6


9- 7-51


2- 1-51
9- 6-51

9- 6-51
5-14-52

2- 1-51
3-28-51
9- 6-51
5-13-52


0


---- ------- --- I~-c~~-- --- l--- --I


I- I ~ ~ c -


-





Table 6. (Continued)
(All measurements shown in feet above or below (-) measuring point)

Well Date Water Date Water Date Water Date Water
Number level level level level

48-24-17 2- 1-51 0.8 2-26-51 -4.1 4-17-51 6.9 5- 4-51 0.1
2-19-51 1.8 3-26-51 1.9 4-25-51 6.8 6-11-51 -1.6

48-25-8 9- 6-51 8.5 5-14-52 -0.5 10-10-52 9.2 10-22-52 9.7


48-25-18 2- 1-51 4.4 3-28-51 8.9 9- 6-51 6.8 5-13-52 -0.2


43-27-4 2- 1-52 9.9 9- 6-51 10.0 5-15-52 5.4 10- 9-52 11.1


4M-27-6 2-19-51 9.9 8-26-51 12.2 6-11-51 9.1 5-15-53 8.0
2-26-51 9.9 4-17-51 14.3 9- 6-51 8.8 5-21-58 8.5
3-16-51 11.8 4-24-51 13.2 10-13-52 12.1

43-27-11 2- 1-51 11.9 9- 6-51 10.7 10-13-52 13.2
3-27-51 12.5 5-15-52 7.9

44-24-1 9- 6-51 4.1 5-15-53 -4.4 10-15-53 1.95
10-18-52 3.7 8-17-52 3.4

44-24-17 2- 1-51 4.4 3-27-51 1.7 9- 6-51 8.4 10-13-52 5.8


.,4 ',



0*
S ':




02



Is, ,






Table 0, (Continued)
(All measurements shown in feet above or below ( -) measuring point)


Well
Number

44-24-20


Date


2- 1-51
8-27-51


Water
level


Date


9- 6-51
5-14-52


Water
level


9.9
-0.15


Date


10-13-52
10-22-52


Water
level

5.6
6.6


44-25-1 2- 1-51 5.6 4- 2-52 10.1 9-29-52 6.1
3-27-51 4.5 7-25-52 8.95 10- 9-52 8.5
9- 6-51 9.0 8-22-52 6.2 10-22-52 9.2

44-25-9 2- 1-51 5.7 8-27-51 8.9 9- 6-51 9.1


44-26-9


46-23-8


8-26-51


1-81-51


11.6


9- 6-51


3-26-51


12.0


5-15-52


9- 5-51 6.6


Date


Water


level




1-80-58 6.5
11-20-58 4.1


5-15-52 0.85


10- 9-52


5-21-58


12.0


-1.1


45-24-6 1-81-51 5.2 5-15-52 0.3 10- 9-52 6.4 10-21-52 7.5

45-25-10 9- 7-51 8.5 10- 9-52 9.7 10-21-52 10.8 12-22-52 6.1

45-25-15 1-31-51 7.7 3-26-51 9.0 9- 5-51 7.2 5-15-53 2.0

45-25-18 1-31-51 9.6 9- 5-51 8.5 10- 9-52 10.1
3-26-51 11.4 5-15-52 4.15 5-21-53 ,5.2


0


------I I-~---~ I





Table 6. (Continued)
(All measurements shown in feet above or below (-) measuring point)


Water
level


' Well
Number

46-28-2


46-24-9

46-24-12

46-24-15


47-20-1



47-22-2


47-22-6


47-22-12


-7.5
-9.1


Date


9- 5-51
10-10-52

10- 9-52

3-26-51

5-15-52
6-23-62

8-23-54
9-30-54
12-28-54


9- 5-51
10-10-52


8-17-53
2-25-54


4-27-51
5- 4-51


Water
level


6.5
5.1

10.4

11.1

3.25
8.3

-29.20
-28.65
-29.30


-5.85
-6.45


Date


8.2
6.8

10.0

10.2

11.1
10.0

-36.65
-29.15
-29.40


5-21-53


4- 8-55
6- 8-55

6-11-51
9- 5-51


Date


9-30-54


10-22-52

9- 5-61

8-25-52
9-29-52


1-31-51
3-26-51

9- 5-51

1-31-51

9- 5-51
4- 2-52

6-11-51
11-20-53
6-28-54


-1.65


-6.60
-6.55


2- 1-55
3-10-55
4- 8-55


Water
level

6.8


10.6

11.5

8.5
9.0


-80.75
-32.50
-31.72


1-81-51
8-26-51


5-15-53
5-21-53


3-26-51
4-17-51


Date


11-19-58

10- 9-52





6- 8-55
7-27-55
10-25-55


Water
level


6.6

11.0





-33.0
-30.45
-30.50


~--------' ~------'


'-----"c~'





'~-----'------







Table 0, (Continued)
(All measurements shown in feet above or below ( -) measuring point)

Well Date Water Date Water Date Water Date Water
Number level level level level

47-22-18 2-19-51 0.6 2-26-51 2.1 8-16-51 3.8 3-26-51 5.1

47-28-19 9- 5-51 6-7 10-10-52 5.4 5-21-53 -0.5
5-14-52 0.2 10-21-52 5.6

47-28-21 1-31-51 3.9 9- 5-51 6.6 4-14-58 5.5
8-27-51 6.8 10-10-52 5.7 5-21-53 0.9

47-23-31 1-31-51 3.9 3-27-51 6.8 9- 5-51 6.1 5-14-52 1.25

48-22-5 8-27-51 8.7 10-10-52 2.8 11-20-52 0.25 9-30-54 1.80
9- 5-51 4.2 5-21-53 --2.5 2-25-54 0.70 7-27-55 1.30
5-14-52 -1.7 8-17-58 2.2 6-28-54 0.90
6-23-52 1.1 10-14-53 2.0 8-24-54 1.1

48-28-10 1-31-51 4.2 9- 5-51 3.6 2- 6-53 5.7
8-27-51 6.6 5-14-52 2.24 5-21-53 2.3

49-22-1 2-19-51 0.1 3-22-51 0.8 5- 4-51 0.4 9- 5-51 1.87
2-26-51 0.0 4-17-51 1.4 6-11-51 -0.8
3-16-51 0.3 4-27-51 1.3 8-13-51 1.30






REPORT OF INVESTIGATIONS NO. 21


TABLE 7. Logs of Selected Wells in the Ruskin Area

Well 40-28-2
(Florida Geol. Survey No. W-2323)
Lithology Depth Below
Land Surface
Pleistocene and Pliocene

Sand, white, quartz, fine to medium, subrounded to well-
rounded, carbonaceous. 0- 10


Sand, brown, quartz, fine to coarse, subrounded to well-
rounded, carbonaceous.
Sand, brown, quartz, carbonaceous, fine to medium.
Sand, as above; peat; wood; amber. _
Sand, as above; abundant shells and fragments; carbonaceous
material; gray silty clay. ___
Shell fragments and sand; quartz pebbles and black phosphate
pebbles, rounded and frosted.


10- 20
20- 35
35- 40

40- 50

50- 60


Hawthorn formation
Clay, gray, sandy, calcareous, phosphatic; quartz and phos-
phate pebbles, as above; a few shell fragments. 60- 70
Clay, gray-white, chalky, phosphatic, sandy in part. 70- 90
Clay, as above, with some gray impure limestone. 90-100
Clay, as above. 100-110
No sample. __ 110-120
Clay, white, chalky, sandy in part, phosphatic. 120-125
No sample. 125-130
Clay, white, chalky, sandy; gray-white sandy limestone, with
a few mollusk molds and casts. ____ 130-140
Clay, greenish gray calcareous, sandy, phosphatic. 140-145
No sample. 145-150
Clay, as above but very sandy; much chert. 150-155
No sample. 155-160
Clay, gray-white calcareous, sandy, phosphatic; gray-white
sandy limestone; some chert. ___ 160-165
Clay, greenish gray, calcareous, sandy, phosphatic; some chert. 165-170
Limestone, gray-white, impure, porous. 170-175
No sample. 175-180
Clay and limestone, with some chert. 180-185
No sample. 185-210
Clay, gray-white, sandy, phosphatic; some chert. 210-215
Tampa formation
Limestone, white to cream, hard to soft, very sandy; some
chert. Archaias sp. and Sorites sp. 215-220
Limestone, creamy white, gray, and tan, soft to hard, granu-
lar, porous, granular to dense, sandy, fossiliferous; crys-
talline calcite. Archaias sp. and Sorites sp. 220-230
Limestone, as above. 230-250





82 FLORIDA GEOLOGICAL SURVEY

Table 7. (Continued)
Lithology Depth Below
Land Surface
No sample. ___ 250-270
Limestone, white to tan, granular to dense, sandy; some chert. __ 270-275
Limestone, buff and tan, soft to hard, dense to granular,
sandy; crystalline calcite in solution cavities. 275-285
No sample. -- 285-300
Limestone, buff and tan, soft to hard, dense to granular, fossil-
iferous; contains numerous fragments of gastropod molds
and casts. 300-305
No sample. 305-310
Limestone, white to brown, soft to hard, chalky, porous,
sandy in part, fossiliferous. 310-315
No sample. 315-325
Limestone, as above; also dark brown, hard, porous. 325-330
Limestone, as above, and some chert. 330-340
No sample. 340-345
Limestone, as above, Archaias sp. 345-350
Limestone, as above. 350-360
Limestone, as above, but no chert. 360-370
No sample. 370-380
Limestone, white, tan, and brown, granular to dense, porous,
dolomitic in part, fossiliferous; crystalline calcite and some
chert. 380-385
No sample. 385-400
Sawannee limestone
Limestone, creamy white to white, soft, granular to chalky,
porous, fossiliferous, calcitic. 400-410
Limestone, as above. Rotalia mexicana and other foraminifers. 410-420
Limestone, creamy white, soft, granular, calcitic, porous,
chalky matrix, fossiliferous, abundant molds, casts, spines,
and foraminifers. Rotalia mexicana. 420-425
No sample. 425-430
Limestone, as above. 430-460
No sample. 460-470
Limestone, buff and tan to white, fairly soft, porous, chalky;
brown crystalline dolomite; some chert. Rotalia mexicana,
Dictyoconus cookei and other foraminifers present. 470-475
No sample. 475-480
Limestone, as above. 480-485
No sample. 485-490
Limestone, white to tan, granular, porous, dolomitic in part,
fossiliferous. Abundant Dictyoconus cookei, Coskinolina
floridana and Rotalia mexicana. 490-500
Limestone, as above, and brown shaly, carbonaceous clay. 500-510'
Limestone, as above. 510-520
Limestone, white, soft, granular, porous, fossiliferous; hard
brown crystalline dolomite; Dictyoconus cookei and other
foraminifers poorly preserved. 520-525






REPORT OF INVESTIGATIONS NO. 21


Table 7. (Continued)
Lithology Depth Below
Land Surface

No sample. __._... ... ... 525-530
Dolomite, brown, hard, crystalline. 530-535
Dolomite, as above, with some soft granular porous fos-
siliferous limestone. Dictyoconus cookei and Coskinolina
floridana. _-... 535-550
No sample. __ __ 550-560
Limestone, white, granular, soft to hard, porous to dense;
small amount of fossiliferous dolomite. Dictyoconus cookei
and Coskinolina floridana. 560-565
No sample. ------__......_..... .. 565-575
Limestone, as above, but dolomite not present. 575-580
No sample. 580-600
Limestone, white, finely granular, soft, porous, fossiliferous;
abundant foraminifers, echinoid spines. 600-605
No sample. ._______ 605-615

Ocala group

Limestone, white, chalky, soft, finely granular, porous, fossi-
liferous. Lepidocyclina ocalana, L. floridana, Nummu-
lites sp., Gypsina globula, and other foraminifers. 615-642


Well 42-23-1

(Florida Geol. Survey No. W-2675)

Pleistocene and Pliocene

Soil and sand. -_ 0- 5
Sand, brown stained, quartz, fine to coarse. 5- 40
Clay, gray, calcareous, very sandy with phosphate; frosted
gray and brown, quartz grains and pebbles; fish teeth; pyrite. 40- 45
Clay, gray, very sandy, calcareous, phosphatic; coarse to fine
sand; frosted rounded quartz pebbles. 45- 55

Hawthorn formation

Clay, gray-white, calcareous, chalky, sandy, phosphatic. ---.- 55- 70
Clay, as above, with some gray, sandy, impure limestone. -------- 70- 85
Clay, as above; limestone, white, hard, sandy, fossiliferous,
phosphatic. 85- 90
No sample. 90- 95
Clay, as above, with some impure limestone. 95-115
No sample. 115-125
Clay, gray-green to white, waxy to chalky, calcareous, sandy
in part; impure limestone with a few mollusk fragments;
phosphate and some chalcedony. 125-135






FLORIDA GEOLOGICAL SURVEY


Table 7. (Continued)
Lithology Depth Below
Land Surface
Tempa formation
Clay, olive green to gray, calcareous, sandy; gray, sandy
limestone; some crystalline calcite; chert and phosphate. --.. 135-145
Limestone, gray-white, fairly hard, sandy, dolomitic in part;
chert; a few mollusk fragments and foraminifers, Archaias
and Sorites. 145-165
No sample. 165-170
Limestone, gray-white, fairly hard, sandy, porous in part,
fossiliferous, dolomitic in part; chert and pyrite. Archaias
and Sorites. ______-----------------170-180
No sample. 180-185
Limestone, as above. 185-195
No sample. 195-205
Limestone, as above. 205-215
No sample. 215-225
Limestone, gray-white, tan and brown, hard, dense, dolomitic
and crystalline in part, sandy, porous in part, fossiliferous;
crystalline calcite and chert; mollusks and foraminifers.
A rchaias. __________---225-235
No sample. 235-240
Limestone, as above. 240-250
No sample. 250-255
Limestone, gray-white to brown, fairly soft to hard, granular
to dense, porous, dolomitic in part, sandy in part; crystal-
line calcite and pyrite; mollusk molds and casts, foramini-
fers. Archaias. 255-275
No sample. -------- .------- .. .-- ... 275-300
Suwannee limestone
Limestone, white to buff, soft, granular to somewhat chalky,
very porous, fossiliferous; chert; echinoid spines and
plates, mollusk molds and casts, many small foraminifers.
Rotalia mexicana. -- 300-310
No sample. 310-320
Limestone, as above. -.----. 320-345
No sample. 345-350
Limestone, as above, but more chalky and less porous. 350-360
No sample. 360-365
Limestone, as above. 365-375

Well 42-25-3
(Florida Geol. Survey No. W-2796)
Pleistocene and Pliocene

Sand, white, fine to coarse. __._ 0- 10
Sand, brown, fine to coarse, carbonaceous, shells. -_-___ -- 10- 20






REPORT OF INVESTIGATIONS No. 21 85

Table 7. (Continued)
Lithology Depth Below
Land Surface
Sand, quartz and phosphate, fine to coarse. 20- 23

Hawthorn formation
Clay, gray-white, calcareous, chalky, phosphatic; few mollusk
molds and casts. ____ 23- 25
Clay, white, chalky, sandy, calcareous, phosphatic; gray-white
impure sandy limestone; pyrite. --....- ......... 25- 35
No sample. ____ .- -.. 35- 45
Clay, gray-white, calcareous, sandy, phosphatic; gray impure
sandy fossiliferous limestone; pyrite; chert; mollusk molds
and casts. __- 45- 50
No sample. 50- 60
Clay, white to gray, chalky, sandy; chert and phosphate. 60- 70
No sample. 70- 75
Clay, greenish gray, sticky, sandy, calcareous; phosphate
grains and pebbles; gray impure sandy limestone, oolitic
in part, phosphatic. 75- 85
No sample. -------- .---__ 85- 90
Clay, gray-white, chalky; phosphatic sand and pebbles; gray
hard impure limestone; phosphatic sand. 90-100
No sample. 100-110
Clay, gray-white, calcareous, very sandy; white to buff sandy
limestone; phosphate and pyrite. 110-120
No sample. 120-140
Clay, as above; gray to buff, hard, dense sandy limestone;
phosphate; chalcedony; dolomite ........ ...... --.-.-...- 140-150
Clay, gray-green, calcareous, very sandy, phosphatic. --- 150-153

Tampa formation

Limestone, white, chalky, soft, fossiliferous, fairly porous.
Archaias. ------ 153-155
No sample. -.---- ___---- 155-165
Limestone, gray-white, fairly hard, sandy, fossiliferous; chert. -- 165-170
No sample. ---- --_------ 170-175
Limestone, gray-white, hard, porous to dense, crystalline,
sandy; chert; mollusk fragments. Abundant Archaias
and Sorites. ----------------- 175-185
No sample. 185-190
Limestone, gray to tan, hard, porous to dense, dolomitic in
part, sandy in part; gray and tan chert; crystalline cal-
cite; mollusks and foraminifers. Sorites. ___ _- 190-200
No sample. 200-210
Limestone, gray-white to brown, granular, sandy, porous to
dense, hard, dolomitic, and crystalline in part, fossili-
ferous; chert. Archaias. 210-245
No sample. 245-255






FLORIDA GEOLOGICAL SURVEY


Table 7. (Continued)
Lithology Depth Below
Land Surface
Limestone, as above. 255-275
Limestone, gray-white to dark brown, soft to hard, granular,
porous to dense, fossiliferous, dolomitic, slightly sandy;
crystalline calcite, chert; mollusks and foraminifers. 275-285
No sample. 285-290
Limestone, as above but no chert. ____ __----- 290-300
Limestone, gray-white to brown, fairly soft to hard, granular,
porous to dense, fossiliferous, dolomitic in part, slightly
sandy; gray and brown chert; crystalline calcite. 300-305
No sample. 305-310
Limestone, white and buff, fairly soft, granular, porous in
part, fossiliferous; crystalline calcite; chert; Sorites. ____ 310-315
No sample. 315-320
Limestone, as above, but dolomitic in part. ... 320-330
No sample. 330-340
Suwannee limestone
Limestone, white, soft, granular to chalky, porous, fossilifer-
ous; crystalline calcite; mollusks, echinoid spines, fora-
minifers. 340-345
No sample. 345-365
Limestone, creamy white, soft, granular, porous, finely crystal-
line in part; crystalline calcite. Rotalia mexicana. ___ 365-375
No sample. ____- 375-380
Limestone, as above. 380-390
No sample. 390-415
Limestone, creamy white to buff, soft, granular to chalky, por-
ous; fossils abundant but poorly preserved. Rotalia mexi-
cana, Dictyoconus cookei. 415-425
No sample. 425-435
Limestone, gray-tan, fairly hard, granular with a chalky
matrix, not very porous, fossiliferous as above. 435-445
No sample. 445-460
Limestone, gray-tan, soft, granular, porous, fossiliferous;
crystalline in part. Rotalia mexicana, Dictyoconus cookei. 460-470
No sample. 470-480
Limestone, white, soft, granular, fossiliferous; dolomite, tan
and brown, hard, crystalline; chert. Rotalia mexicana,
Dictyoconus cookei, Coskinolina floridana. 480-490
Limestone, gray-tan, fairly hard, granular, impure, dolomitic
in part, fairly porous; chert. Rotalia mexicana, Dictyo-
conus cookei, Coskinolina floridana, Gypsina globula. Top
of Ocala group apparently in this interval. 490-500
Ocala group
Limestone, gray-white to tan, granular, fairly porous, fossil-
ferous, dolomitic in part; chert; crystalline calcite. Gyp-
sina globula abundant. 500-510