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Sediment Core Images as Climate and Paleoenvironmental Indicators

Permanent Link: http://ufdc.ufl.edu/UFE0021148/00001

Material Information

Title: Sediment Core Images as Climate and Paleoenvironmental Indicators Evidence from Modern and Historical Sediments of Lake Peten Itza, Guatemala
Physical Description: 1 online resource (105 p.)
Language: english
Creator: Grzesik, Dustin
Publisher: University of Florida
Place of Publication: Gainesville, Fla.
Publication Date: 2010

Subjects

Subjects / Keywords: Geological Sciences -- Dissertations, Academic -- UF
Genre: Geology thesis, M.S.
bibliography   ( marcgt )
theses   ( marcgt )
government publication (state, provincial, terriorial, dependent)   ( marcgt )
born-digital   ( sobekcm )
Electronic Thesis or Dissertation

Notes

Abstract: Drilling of Lake Pete acuten Itza acute in the lowlands of northern Guatemala during February and March 2006 recovered 1,327 meters of sediment from seven sites. Accelerator Mass Spectrometry (AMS) 14C dates, and a tephra layer from a volcanic event of known age indicate that site (PI-6) has a sediment record spanning the past 84,000 years. Sediment core images were used to interpret the paleoenvironmental and paleoclimatic history of the region. Sediment image profiles were used successfully for stratigraphic correlation among cores collected from Lake Pete acuten Itza acute. A novel technique for image processing and automation was developed using ImageJ, the premier free, open-source software package funded by the National Institutes of Health. Semi-automatic routines for image normalization were necessary for quantitative comparison of sediment color data due to the large size of the dataset and the limitations of graphics processing engines of current computer hardware. Current hardware, software, and the utility of RGB analysis within a complex lithologic setting were addressed by tailoring algorithms and a multi-variable approach. A routine to determine the relative granularity of the sediments using the core images was developed. The resulting record displayed an inverse relation to magnetic susceptibility. L*a*b* colorspace data suggest the influence of precessional forcing. The a* variable is coherent and in-phase with precessionally influenced summer insolation. Changes in a composite record image clearly illustrate the transition from the Last Glacial Maximum (LGM) to the deglacial and modern conditions. Sediment data suggest that between 25,000 and 18,000 years before present the climate of Pete acuten, Guatemala was wet and cool. Image data were used to aid interpretation of magnetic susceptibility data and other preliminary core-logging data. The image and susceptibility data suggest correlations with climate events during the termination of the Pleistocene, including possible winter precipitation and response to a meltwater flux into the Gulf of Mexico. The image data also suggest that lightness is influenced by various depositional and diagenetic processes, as well as analytical methods. The lightness of sediments from site PI-6 was not correlated directly to changes in paleoclimate, although sediment lightness and carbonate content was related in the modern surface samples. The a* variable was found to be correlated to shifts in solar insolation and to be related to the oxidative regimes in the modern surface samples. The estimate of granularity illustrates the utility of developing complex algorithms for rapid, quantitative identification of features and characteristics of the sediment.
General Note: In the series University of Florida Digital Collections.
General Note: Includes vita.
Bibliography: Includes bibliographical references.
Source of Description: Description based on online resource; title from PDF title page.
Source of Description: This bibliographic record is available under the Creative Commons CC0 public domain dedication. The University of Florida Libraries, as creator of this bibliographic record, has waived all rights to it worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law.
Statement of Responsibility: by Dustin Grzesik.
Thesis: Thesis (M.S.)--University of Florida, 2010.
Local: Adviser: Brenner, Mark.
Electronic Access: RESTRICTED TO UF STUDENTS, STAFF, FACULTY, AND ON-CAMPUS USE UNTIL 2011-04-30

Record Information

Source Institution: UFRGP
Rights Management: Applicable rights reserved.
Classification: lcc - LD1780 2010
System ID: UFE0021148:00001

Permanent Link: http://ufdc.ufl.edu/UFE0021148/00001

Material Information

Title: Sediment Core Images as Climate and Paleoenvironmental Indicators Evidence from Modern and Historical Sediments of Lake Peten Itza, Guatemala
Physical Description: 1 online resource (105 p.)
Language: english
Creator: Grzesik, Dustin
Publisher: University of Florida
Place of Publication: Gainesville, Fla.
Publication Date: 2010

Subjects

Subjects / Keywords: Geological Sciences -- Dissertations, Academic -- UF
Genre: Geology thesis, M.S.
bibliography   ( marcgt )
theses   ( marcgt )
government publication (state, provincial, terriorial, dependent)   ( marcgt )
born-digital   ( sobekcm )
Electronic Thesis or Dissertation

Notes

Abstract: Drilling of Lake Pete acuten Itza acute in the lowlands of northern Guatemala during February and March 2006 recovered 1,327 meters of sediment from seven sites. Accelerator Mass Spectrometry (AMS) 14C dates, and a tephra layer from a volcanic event of known age indicate that site (PI-6) has a sediment record spanning the past 84,000 years. Sediment core images were used to interpret the paleoenvironmental and paleoclimatic history of the region. Sediment image profiles were used successfully for stratigraphic correlation among cores collected from Lake Pete acuten Itza acute. A novel technique for image processing and automation was developed using ImageJ, the premier free, open-source software package funded by the National Institutes of Health. Semi-automatic routines for image normalization were necessary for quantitative comparison of sediment color data due to the large size of the dataset and the limitations of graphics processing engines of current computer hardware. Current hardware, software, and the utility of RGB analysis within a complex lithologic setting were addressed by tailoring algorithms and a multi-variable approach. A routine to determine the relative granularity of the sediments using the core images was developed. The resulting record displayed an inverse relation to magnetic susceptibility. L*a*b* colorspace data suggest the influence of precessional forcing. The a* variable is coherent and in-phase with precessionally influenced summer insolation. Changes in a composite record image clearly illustrate the transition from the Last Glacial Maximum (LGM) to the deglacial and modern conditions. Sediment data suggest that between 25,000 and 18,000 years before present the climate of Pete acuten, Guatemala was wet and cool. Image data were used to aid interpretation of magnetic susceptibility data and other preliminary core-logging data. The image and susceptibility data suggest correlations with climate events during the termination of the Pleistocene, including possible winter precipitation and response to a meltwater flux into the Gulf of Mexico. The image data also suggest that lightness is influenced by various depositional and diagenetic processes, as well as analytical methods. The lightness of sediments from site PI-6 was not correlated directly to changes in paleoclimate, although sediment lightness and carbonate content was related in the modern surface samples. The a* variable was found to be correlated to shifts in solar insolation and to be related to the oxidative regimes in the modern surface samples. The estimate of granularity illustrates the utility of developing complex algorithms for rapid, quantitative identification of features and characteristics of the sediment.
General Note: In the series University of Florida Digital Collections.
General Note: Includes vita.
Bibliography: Includes bibliographical references.
Source of Description: Description based on online resource; title from PDF title page.
Source of Description: This bibliographic record is available under the Creative Commons CC0 public domain dedication. The University of Florida Libraries, as creator of this bibliographic record, has waived all rights to it worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law.
Statement of Responsibility: by Dustin Grzesik.
Thesis: Thesis (M.S.)--University of Florida, 2010.
Local: Adviser: Brenner, Mark.
Electronic Access: RESTRICTED TO UF STUDENTS, STAFF, FACULTY, AND ON-CAMPUS USE UNTIL 2011-04-30

Record Information

Source Institution: UFRGP
Rights Management: Applicable rights reserved.
Classification: lcc - LD1780 2010
System ID: UFE0021148:00001


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1 SEDIMENT CORE IMAGES AS CLIMATE AND PALEOENVIRONMENTAL INDICATORS: EVIDENCE FROM MODERN AND HISTORICAL SEDIMENTS OF LAKE PETN ITZ, GUATEMALA By DUSTIN AARON GRZESIK A THESIS PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVE RSITY OF FLORIDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE UNIVERSITY OF FLORIDA 2010

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2 2010 Dustin Aaron Grzesik

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3 In loving memory of my grandfather Richard Paul Grzesik Sr.

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4 ACKNOWLEDGMENTS I am honore d to thank my co chairs Dr. Mark Brenner, and Dr. David Hodell for welcoming me as a student, for their academic support, and for the opportunity to participate in the Petn Itz Scientific Drilling Project. I would also like to thank Dr. Jon Martin, for his critical evaluation of this thesis. I would like to recognize Dr. Jason Curtis for his help searching for gastropods, time spent on the mass spectrometer, time spent discussing mechanical and electronic systems, and for being such a great roommate at La Casa de Don David during the field campaign. I owe thanks to Andreas Mller for doing a great job as a co database curator during the field campaign and for being an excellent friend. Ray G. Thomas was critical in executing software deployment prior to the field campaign, and has inspired me to learn more about hardware and software design and modification. William Kenney provided assistance with measurements of surficial sediment samples. I would also like to acknowledge Dr. Adrian Gilli, Jennifer Mays, and Jaime Escobar for their support and collaboration on this project. I express my sincere thanks and appreciation to the Drilling, Observation and Sampling of the Earth s Continental Crust ( DOSECC) drilling team (Ed Brown, James Cramer, John Joice, B eau Marshall, Dennis Nielson, Vance Hiatt, Doug Schnurrenberger, Kent Thomas, and Ryan Wilson), the International Continental Scientific Drilling Program Operational Support Group ( ICDP OSG ) (Christian Carnein, Ronald Conz, Uli Harms, Jochem Kueck, Martin Toepfer), and Lacustrine Core Repository ( LRC/LacCore) (Kristina Brady, Amy Myrbo and Anders Noren) whose hard work and good humor made the project a success. Tom Guilderson provided assistance with radiocarbon dating. I am also grateful to the numerous agencies and individuals in

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5 Guatemala who provided assistance to this project. They include: Universidad del Valle, Universidad San Carlos, Ministerio de Ambiente y Recursos Naturales, Consejo Nacional de Areas Protegidas, Instituto de Antropologa e Histor ia, Autoridad Para el Manejo y Desarrollo Sostenible de la Cuenca del Lago PetnItz, Wildlife Conservation Society, Alex Arrivillaga, Cathy Lopez, Margaret Dix, Michael Dix, Margarita Palmieri, David, Rosita, & Kelsey Kuhn, and the staff at La Casa de Do n David, Lico Godoy, Tony Ortiz, Franz Sperisen, Luis Toruo, Julian Tesucn, Liseth Perez, Melissa Orozco, Silja Ramirez, Gabriela Alfaro, and Jacobo Blijdenstein. This project was funded by grants from the U.S. National Science Foundation, the International Continental Scientific Drilling Program, the Swiss Federal Institute of Technology, and the Swiss National Science Foundation. Chuang Xuan provided critical evaluation and support for spectral analysis and signal processing. Michael Cammer, former di rector of the Analytical Imaging Facility of the Albert Einstein College of Medicine was critical in improving my understanding of image analysis and provided support during the early phases of development of routines for normalizing the image dataset. I thank Dr. John Sum Ping, Jaime Escobar, and Andreas Mller for reviewing this thesis and for their critical evaluation. I would also like to thank the faculty and graduate students of the Department of Geological Sciences for their open doors, endless pati ence, and enthusiasm. Jie Wang and Ryan Francis were excellent colleagues as TAs. My officemates Mike Ritorto and Joshua Richards made work fun and Im thankful for the help they provided whenever I needed it. I enjoyed numerous lunches in the Plaza of the Americas with Jaime Escobar and Natalia Hoyos.

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6 Finally, I thank my parents Richard and Janice Grzesik and parents inlaw John and Lynal Sum Ping for their support and encouragement. And most importantly I would like to thank Joanne Sum Ping for her endless patience, support, and motivation, which allowed me to complete this work and remain not only sane, but supremely happy.

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7 TABLE OF CONTENTS ACKNOWLEDGMENTS .................................................................................................. page 4 LIST OF TABLE S .......................................................................................................... 10 LIST OF FIGURES ........................................................................................................ 11 ABSTRACT ................................................................................................................... 16 CHAPTER 1 INTRODUCTION .................................................................................................... 18 Analytical Challenges ....................................................................................... 19 Imaging ............................................................................................................. 20 2 BACKGROUND ...................................................................................................... 21 Petn Paleolimnology ....................................................................................... 21 Petn Itz Limnology and Setting ..................................................................... 21 Cultural Setting ................................................................................................. 22 Petn Itz Scienti fic Drilling Project ( PISDP) .................................................... 23 3 METHODS .............................................................................................................. 26 Field Methods ......................................................................................................... 26 Sediment Drilling .............................................................................................. 26 Core Compositing with SPLICER ..................................................................... 27 Modern Surface Sediment Transect ................................................................. 28 Analytical Methods .................................................................................................. 28 Subsampling ..................................................................................................... 29 Image Acquisition ............................................................................................. 29 Red, green, blue color digital images ......................................................... 30 L*a*b* colorspace ...................................................................................... 30 Image Processing and Analysis ....................................................................... 31 Geochemical Analyses ..................................................................................... 32 Core Chronology .............................................................................................. 32 4 RESULTS AND DISCUSSION ............................................................................... 39 Site PI 6 Chronology ............................................................................................... 39 Surface Sediments from the Water Depth Transect ............................................... 39 Transect Image Data ........................................................................................ 39 Transect G eochemistry .................................................................................... 40 Transect Lithology ............................................................................................ 41

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8 Site PI 6 Sediment Cores ....................................................................................... 41 Site PI 6 Lithology ............................................................................................ 41 Core Logging Data ........................................................................................... 41 Density ....................................................................................................... 41 Magnetic susceptibility ............................................................................... 42 XRF data .................................................................................................... 43 Composite image RGB data ...................................................................... 43 L*a*b* colorspace ...................................................................................... 44 PI 6 granularity ........................................................................................... 44 5 INTERPRETATION OF SEDIMENTS FROM SITE PI 6 ......................................... 64 Modern Sediment Properties .................................................................................. 64 Modern Limnological Setting ............................................................................ 64 Lightness and E/P ............................................................................................ 64 Confounding Factors ........................................................................................ 65 Surface Sediment Transect Samples ............................................................... 65 Sediment Cores ...................................................................................................... 65 Core Images ..................................................................................................... 65 Va riations in Sediment Lithology ...................................................................... 66 X Ray Fluorescence ( XRF ) Data ...................................................................... 67 L*a*b* Data Evaluation and Interpretation ........................................................ 67 Magnetic Susceptibility ..................................................................................... 68 Granularity ........................................................................................................ 68 6 CORRELATION TO OTHER CLIMATE RECORDS ............................................... 79 Regional Paleoclimate ............................................................................................ 79 Global Paleoclimate and Timeseries Analysis ........................................................ 80 7 SU MMARY AND CONCLUSIONS .......................................................................... 89 Limitations of Images as Paleoclimatic Proxies ...................................................... 90 Future Work ............................................................................................................ 91 APPENDIX A SOFTWARE USED ................................................................................................. 92 Field Software ......................................................................................................... 92 Drilling Information System ............................................................................... 92 SPLICER .......................................................................................................... 92 Image Processing and Analysis .............................................................................. 93 ImageJ .............................................................................................................. 94 Matlab ............................................................................................................... 95 Corelyzer and Corewall .................................................................................... 95 Analyseries ....................................................................................................... 96

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9 B PALEOLAKE HIGH STANDS ................................................................................. 97 C SITE PI 3 ................................................................................................................ 99 LIST OF REFERENCES ............................................................................................. 101 BIOGRAPHICAL SKETCH .......................................................................................... 105

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10 LIST OF TABLES Table page 3 1 Drilling site summary ......................................................................................... 33 3 2 Locations of surface sediment samples collected along a water depth transect. .............................................................................................................. 33 4 1 Dates and tie points used to develop the chronology for site PI 6 including sample, dept h, 14C dates, positions. ................................................................... 46 4 2 Composition of surface sediments along the water depth transect. All samples were collected using a clamshell dredge. ............................................. 47 5 1 Multivariate correlations between elements of core sections from site PI 6. .................................................................................................................... 70

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11 LIST OF FIGURES Figure page 1 1 Maps o f the Americas showing t he location of the study site. ............................ 24 1 2 Lake Petn Itz climate regime .......................................................................... 25 3 1 Flowchart of field data and operations ................................................................ 34 3 2 Gretag MacBeth mini c hecker calibration card. ................................................. 35 3 3 Surface sediments collected along the water depth transe ct ............................. 36 3 4 No rmalized sediment core images. .................................................................... 37 3 5 Sediment core image granularity threshold images. ........................................... 38 4 1 PI 6 and PI 3 radiocarbon ages and composite PI 6 age model. ....................... 48 4 2 Magnetic susceptibility of PI 3 and PI 6. ........................................................... 49 4 3 Surface sediment transect L*a*b* versus water depth meters (m). .................. 50 4 4 Surface sediment transect %CaCO3 and % orga nic carbon versus water depth. ................................................................................................................. 51 4 5 Surface sediment transect %N, and % organic carbon ...................................... 52 4 6 Surface sediment transect total phosphorus. ...................................................... 53 4 7 Digital images of various lithologic units from Lake Petn Itz cores ................. 54 4 8 Stratigraphy of PI 6 (with permission from A. Mller). ........................................ 55 4 9 PI 6 composite Gamma R ay A ttenuation P orosity E valuation ( GRAPE ) density record (g/cm3). ........................................................................................ 56 4 10 PI 6 composite magnetic susceptibility reco rd (SI x E06). .................................. 57 4 11 Selected X Ray Fluorescence ( XRF ) data (kcps) from site PI 6 6C 4H 1 plotted versus depth in the core section (mm). ................................................... 58 4 12 PI 6 Composite green color reflectance data versus age raw data (ybp). .......... 59 4 13 L* image data versus age (ybp). ......................................................................... 60 4 14 a image data versus age (ybp). ......................................................................... 61

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12 4 15 b image data versus age (ybp). ......................................................................... 62 4 16 Image derived granularity versus age (ybp) ....................................................... 63 5 1 Cartoon depicting stratification of Lake Petn Itz .............................................. 70 5 2 CaCO3 content of modern surface sediment samples. ....................................... 71 5 3 Surf ace sample L* and a* vs depth. ................................................................... 72 5 4 Multivariate correl ation matrix of PI 6 XRF data ................................................. 73 5 5 PI 6 6C 4H 1 XRF C a, Fe, Sr, and Ti data (kcps). ............................................. 74 5 6 PI 6 6C 4H 1 XRF S, Mn, K, and Si data (kcps). ................................................ 75 5 7 PI 6 6C 4H 1 L*a*b* data. ............................................................................... 76 5 8 PI 6 composite oxygen isotopic data (blue) courtesy of Jaime Escobar (in prep), and a* color data. ..................................................................................... 77 5 9 PI 6 Composite estimate of grain size proxy (using the find edges based algorithm). Magnetic susceptibility composite data (courtesy of Dr. A. Gilli) ...... 78 6 1 P ollen accumulation, charcoal concentration, magnetic susceptibility from site PI 18O of the Greenland Ice Core. ....................... 81 6 2 PI 6 a* data plotted vs time and the Cariaco 5 50 nm reflectance plotted on its independent time scale. ...................................................................................... 82 6 3 a* frequency spectrum, colored horizontal bars indicate significance (red= 99.9, yellow= 99, green= 95, teal=90, white=50). ............................................... 83 6 4 a* frequency spectrum following cubic spline filter to remove low frequency signal ................................................................................................................. 84 6 5 a* wavelet surface plot, statistic al envelope shown with curved lines and transparent mask. ............................................................................................... 85 6 6 L*a* plots of PI 6 and agemodel fitted images showing the relation between composite sediment core images and the L* a nd a* variables. .......................... 86 6 7 Summer insolation at 17 degrees north (Analyseries) plotted vs age (kybp). ..... 87 6 8 Cross correlation between fil tered a* and summer insolation at 17 degrees north. .................................................................................................................. 88 B 1 Hydrobiidae gastropods (1mm ticks) .................................................................. 97

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13 B 2 A cartoon illustrating the implications for a 20meter rise in the level of Lake Petn Itz. .......................................................................................................... 98 C 1 PI 3 composite lithological description by Andreas Mller. ............................... 100

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1 4 LIST OF ABBREVIATIONS AMS Accelerator Mass Spectrometry AMSL Above Mean Sea Level DIS Drilling Information System DOSECC Drilling, Observation and Sampling of the Earths Continental Crust dpi dots per inch GB Gigabyte GPS Global Positioning System GRAPE Gamma R ay A ttenuation P orosity E valuation GUI Graphical User Interface HPC Hydraulic Piston Corer IC Inorganic Carbon ICDP International Continental Scientific Drilling Program IODP Integrated Ocean Drilling Program L*a*b* Lightness, a, and b colorspace LGM Late Glacial Maximum m meter MB Megabyte MBLF Meters Below Lake Floor MCD Mean Composite Depth MIS Marine Isotope Stage MSL Mean Sea Level MSCL Multi Sensor Core Logger PISDP Petn Itz Scientific Drilling Project px pixel(s)

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15 TC Total Carbon TN Total Nitrogen TP Total Phosphorus XRF X Ray Fluorescence ybp years before present (1950) zmax maximum depth in meters %OC Percent Organic Carbon

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16 Abstract of Thesis Presented to the Graduate School of the University of Florida in Partial Fulfillment of the Requirem ents for the Master of Science SEDIMENT CORE IMAGES AS CLIMATE AND PALEOENVIRONMENTAL INDICATORS: EVIDENCE FROM MODERN AND HISTORICAL SEDIMENTS OF LAKE PETN ITZ, GUATEMALA By Dustin Aaron Grzesik Ma y 2010 Chair : Mark Brenner Major: Geology Drilling of Lake Petn Itz in the lowlands of northern Guatemala during February and March 2006 recovered 1,327 meters of sediment from seven sites. Accelerator Mass Spectrometry (AMS) 14C dates, and a tephra layer from a volcanic event of known age indicate that site (PI 6) has a sediment record spanning the past 84,000 years. Sediment core images were used to interpret the paleoenvironmental and paleoclimatic history of the region. Sediment image profiles were used successfully for stratigraphic corr elation among cores collected from Lake Petn Itz. A novel technique for image processing and automation was developed using ImageJ, the premier free, opensource software package funded by the National Institutes of Health. Semi automatic routines for image normalization were necessary for quantitative comparison of sediment color data due to the large size of the dataset and the limitations of graphics processing engines of current computer hardware. Current hardware, software, and the utility of RGB analysis within a complex lithologic setting were addressed by tailoring algorithms and a multi variable approach.

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17 A routine to determine the relative granularity of the sediments using the core images was developed. The resulting record displayed an inverse relation to magnetic susceptibility. L*a*b* colorspace data suggest the influence of precessional forcing. The a* variable is coherent and inphase with precessionally influenced summer insolation. Changes in a composite record image clearly illustr ate the transition from the Last Glacial Maximum (LGM) to the deglacial and modern conditions. Sediment data suggest that between 25,000 and 18,000 years before present the climate of Petn, Guatemala was wet and cool. Image data were used to aid interpretation of magnetic susceptibility data and other preliminary corelogging data. The image and susceptibility data suggest correlations with climate events during the termination of the Pleistocene, including possible winter precipitation and response to a meltwater flux into the Gulf of Mexico. The image data also suggest that lightness is influenced by various depositional and diagenetic processes, as well as analytical methods. The lightness of sediments from site PI 6 was not correlated directly to changes in paleoclimate, although sediment lightness and carbonate content was related in the modern surface samples. The a* variable was found to be correlated to shifts in solar insolation and to be related to the oxidative regimes in the modern surface samples. The estimate of granularity illustrates the utility of developing complex algorithms for rapid, quantitative identification of features and characteristics of the sediment.

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18 CHAPTER 1 INTRODUCTION Paleolimnological research has provided highre solution records of past continental climate and environmental change (Smol, 1992). Several long term climate records have been recovered from the continents and oceans. However, because of expanded glacial ice cover at high latitudes it has proved diffi cult to find ice age climate records from low elevation tropical lakes (Deevey, 1957). Many of these lakes, especially the shallower ones, dried completely during the glacial advance. Here I examine highresolution digital images of sediment cores from t he deep Lake Petn Itz basi n, Guatemala, and explore the potential for using them to infer paleoenvironmental conditions over the past ~85,000 years. I also discuss the use of sediment images, and the characteristics of Red Green Blue ( RGB ) analysis and other image processing techniques for project planning and sampling strategy. I argue that color reflectance of surface sediment samples collected along a water depth transect in Lake Petn Itz reflect various properties of the sediment that are indicat ive of environmental conditions. Modern surface sediment depth transect samples vary in geochemical and optical properties. My hypothesis is that color reflectance measured in Lake Petn Itz sediment cores can be related to reflectance in the surface sediment samples from the water depth transect and used to infer changes in paleoenvironmental conditions. Shifts in the location of the carbonate depositional zone cause changes in sediment lightness and such changes in sediment lightness within a core thus indicate past changes in water depth. The comparison of X Ray Fluorescence (XRF) data, core composite images and paleoclimate proxies are used to test the hypothesis. Confounding factors include diagenetic changes, and strata that

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19 are not represented i n the modern lake sediments and limit the application of lightness as a paleoclimatic proxy in the Petn Itz sediment record Hue specific image interpretation, such as a* image data provide a mechanism for paleoclimatic interpretation from sediment core image data of Lake Petn Itz The Petn Itz Scientific Drilling Project (Hodell et al., 2006) recovered 1,327 m of sediment core from seven sites in early 2006. These cores are the first such long reco rds from the lowland Neotropics. O perating procedur es generally followed the workflow standards of the Integrated Ocean Drilling Program (IODP). Sediments recovered from Lake Petn Itz provide the opportunity to study global and regional climate change. Analys e s of oxygen isotopes and pollen in cores col lected in 2002 provided insight in to the impact of climate change on Classic Maya culture (Hodell et al., 2005; Brenner et al., 2002). Such studies are relatively expensive and time consuming and require destructive analyses of sedimen ts. Analytical Chal lenges R ecent development s of core logging methods and equipment such as the Geotek Multi Sensor Core Logger (MSCL) have allowed researchers to assess sediment characteristics rapidly Measures that can be made include Gamma Ray Attenuation Porosity Evaluation (GRAPE) density, magnetic susceptibility, pwave velocity, natural gamma, and hi gh resolution digital imaging. Automated logging of lake sediment cores and analysis with scanning XRF have allowed scientists to generate highly detailed chemical profil es of sediment cores, minimizing the need to perform time consuming wet chemical analyses. S canning XRF techniques however, are still not widely available and require expensive, specialized equipment.

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20 Imaging Imaging techniques, including microscopy an d Munsell color charts, have long played a role in sediment and geological description and interpretation. Images, however, have traditionally been used in a descriptive, qualitative fashion, failing to take advantage of the valuable quantitative informat ion that may be extracted from these analog and digital data. As imaging technologies have become cheaper and more reliable, image analysis techniques have been used increasingly in se diment studies (Francus, 2004). Varved lake sediment cores provide an i deal subject for image analysis given their dramatic changes in color/shade. They possess layers that are clearly distinguishable both by eye and by the sensors of digital cameras. Varved deposits, however, are rare. Non laminated sediments, with more s ubtle changes in hue and intensity, may best illustrate the quantitative pow ers of digital image analysis.

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21 CHAPTER 2 BACKGROUND Petn Paleolimnology C limate change in the lowland tropics of northern Guatemala was first explored by Dr. Edward S. Deevey, a pioneer in paleolimnological study of the region. The search for Pleistoceneage sediments in the region began in 1940 when Deevey cored lakes in Mexico (Deevey, 1955). This early boring expedition failed to recover Pleistocene lake deposits, but in a prescient speculation, Deevey noted that such a record should be sought in the Petn, in Guatemala (Deevey, 1957). In May 1980 Deevey and others cored several relatively small lakes in Petn, including Quexil, Salpeten, and Macanche. The region was selected because lake basins in the area were thought to have been deep enough to have held water during the Last Glacial Maximum (LGM) (Deevey et al., 1980). Deevey et. al. (1983), referring to the 20 m core that was retrieved from Lake Quexil, noted that R ecovery of Pleistocene lacustrine deposits culminates a forty year search Indeed, sediments spanning the Holocene and penetrating into the late Pleistocene had been collected. The record, however, remained poorly dated and was discontinuous, in that there were gaps between each of the sections recovered by the split spoon corer. Furthermore, there was some concern that the oldest deposits might contain hiatuses, or were deposited in very shallow water. More than 25 years passed before further attempts were made to raise Pleistoce ne sediments from a Petn lake. Petn Itz Limnology and Setting Lake Petn Itz ( Figure 11) has a surface area of ~100 km2 ( 1655 North, ~8950 West, 110 meters AMSL). It was formed by a combination of tectonic activity

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22 and solution processes (Vinson, 1962). The lake is sensitive to changes in climate and lake level fluctuates in response to precipitation (Deevey et al., 1980). The dominant cation and anion in Lake Petn Itz s water are, in terms of milli equivalents, cal cium and sulfate, respectively, with magnesium and bicarbonate following in abundance (Deevey et al., 1980: Hillesheim, 2005). The lakes pH is basic (8.0), and sediments in water depths <~30 m are rich in the remains of calcareous organisms such as snai ls and ostracods High calcium carbonate (CaCO3) content of shallow water deposits forms a lighter halo in the littoral zone of the lake, particularly in the gradually sloping southern basin, where sediments are replete with the remains of lacustrine gastropods and other calcareous microfossils (Covich, 1976; Curtis et al., 1998). The modern lake level fluctuates in response to variations in evaporation/precipitation (E/P). The water body has no major outlets and loss to groundwater seepage is minor so that the basin is effectively closed. Lake Petn Itz is sensitive to global climate through shifts in the seasonal movement of the Inter Tropical Convergence Zone (ITCZ) (Hodell et al., 2001). The lake is located along a steep northsouth gradient of precipitation on the Yucatan Penin sula (Wilson, 1980) ( Figure 12 ). The climatologic setting makes it sensitive to changes in the ITCZ and precipitation in the region. Cultural Setting Lake Petn Itz is part of a chain of lakes that includes, from west to east, Perdida, Sacpuy, Petenxil, Quexil, Salpeten, Macanche, Yaxha, and Sacnab. This region, referred to as the Petn Lake District, constitutes part of the core region for ancient lowland Maya settlement. Located approximately 50 km north are the

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23 arc haeological ruins of Tikal. Sediments from Lake Petn Itz suggest that changes in Holocene climate may have had an impact on Maya cultural evolution (Mller et al. 2009, 2010). Petn Itz Scientific Drilling Project ( PISDP) Lake Petn Itz (zmax = 160 m ) was selected as a potential candidate for lake drilling after detailed seismic surveys were completed (Anselmetti et al. 2005) and Kullenberg coring was unable to penetrate stiff gypsum rich sediments about 6 m below the lake floor deposited during the lat e Glacial (Hillesheim, 2005). Seismic stratigraphy provided evidence for up to 100 m of sediment in some basins (Anselmetti, 2006).

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24 Figure 11. Maps of the Americas showing the location of the study site. (a) the Petn Lake District, northern Guatemala. (Modified from Anselmetti et al. 2006). (b) Lakes of the Petn Lake District (Modified from Hilleshiem et al. 2005). (c) Coring sites and bathymetry of Lake Petn Itz (from Anselmetti et al. 2006). Drilling sites were selected after preliminary seismic surveys and Kullenbe rg coring provided evidence for a continuous sediment record.

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25 Figure 12. Lake Petn Itz lies in an area that may be described as a tropical monsoon climate regime, along the steep precipitation gradient of the Yucatan peninsula ( Modified from Wilson, 1980). Contours are mm of annual rainfall.

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26 CHAPTER 3 METHODS Field Methods Sediment Drilling Sediment cores were collected during the Lake Petn Itz Scientific Drilling Project ( PISDP) in February and March 2006. The modifi ed GLAD 8 00 (Global Lake Drilling System, aka RV Kerry Kelts) served as the drilling platform for core recovery. A team from Drilling, Observation and Sampling of the Earths Continental Crust (DOSECC), and scientists of the PISDP collected cores around th e clock, during two twelvehour shifts. All tolled, 1 327 m of sediment was collected from seven sites (Table 31). Drilling was accomplished using proprietary DOSECC coring tools including the Hydraulic Piston Corer (HPC), Extended Nose, and Alien. The HPC was the most used coring tool during the PISDP because of the tools suitability for recovering complete, 3m sections of undisturbed clay rich sediments with each drive. Prior to each drive, the coring tool was fitted with a polycarbonate liner. After a successful drive, the sediment filled liner was retrieved, cut in to 1.5 m lengths, capped and labeled. All core sections were measured and labeled with Expedition, Site, Hole, Core, Section, and Type (tool type) in preparation for shipping and st orage. The 3 meter stroke of the coring tools left gaps or section breaks between drives. To recover sediment from the missing intervals it was necessary to core secondary and tertiary holes near the first hole. Drives in secondary hole B w ere offset v ertically by ~1.5 m with respect to depths in primary hole A. Hole C was typically offset by 0.75 m relative to holes A and B. At sites PI 1, PI3, PI4, PI 6, PI 7 the team first cored hole A,

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27 and subsequently holes B and C. Coring at shallow water sit e PI 9 was halted after slumping prevented drilling progress. Five holes (A, B, C, D, E) were drilled at Site PI 2. Following each work shift change, sediment cores were transported to the landbased laboratory where science team members measured gamma r ay attenuation (GRAPE density), magnetic susceptibility, and pwave velocity using a Geotek Multi Sensor Core Logger (MSCL) provided by the International Continental Drilling Program (ICDP). Scientists also measured porefluid alkalinity and pH, and analy zed smear slides to describe core lithology. Platform and labcollected data were managed and stored using the Drilling Information System (D IS) database developed and supported by the ICDP. Sediment cores were bar coded, boxed, and stored in an on site refrigerated shipping container. Upon completion of the field campaign, the sediment core s were shipped to the Lacustrine Core Repository (LacCore) at the University of Minnesota, Minneapolis. Core C ompositing with SPLICER MSCL data were correlated stratigraphically with SPLICER software to enable real time drilling decisions for increased efficiency and to guarantee recovery of complete sediment records at each site ( Figure 31 ). SPLICER software is used often on IODP drilling projects, but has not bee n used frequently in lake drilling projects because of equipment and personnel limitations SPLICER played an important role in drilling decisions and the shorebased laboratory team members would often contact the drilling platform via cellular phone to discuss drilling depth offsets for the final hole at a site. SPLICERs graphical user interface (GUI) allows movement of data from core section s from different holes at a site in relation to one another, so that features may be

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28 correlated A real time co rrelation coefficient is displayed. A composite record for each site was created by depthshifting cores from multiple holes at a site, using SPLICER. During the field campaign, GRAPE density and magnetic susceptibility were used for splicing. A key, called a Splice table was created by moving downcore, and selecting tie points from one core section to another. Splicer allowed the science team to identify gaps in recovery and to target sediment gaps that had to be recovered in the final hole. Spl icer was also used to construct the composite section for sampling and analysis. Modern Surface Sediment Transect In addition to sediment coring, a suite of surface sediment samples was collected along a water depth transect from the shoreline to ~100 m water depth, using a clamshell dredge (Table 32). Global Positioning System ( GPS ) coordinates and water depth were recorded at each location. Analytical Methods PI 6 was selected as the primary site for study because of the continuity of the record and the apparent lack of sediment slumping. Disturbances and slumping were observed in the record of PI 3 ( Appendix F igure C 1). In June 2006 the PISDP held a sampling party at the LacCore facility. Sediment core liners were split lengthwise using an oscillatin g cast saw. Soft clay sediments were split with a metal plate and stiffer deposits were cu t with a metal guitar string. Each core was split into working and archive halves. The core surfaces were cleaned and smoothed using glass slides. The working hal ves were sampled for sediment analyses that are destructive. The archival halves were used for nondestructive imaging, logging, and lithologic description.

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29 Subsampling Sediment subsamples were collected for analyses of pollen, diatom s 18O and geomicrobiology. During this process, cores were described and a lithologic profile was created. Visual inspection of cores improved the understanding of among hole correlations and the final spliced composite core table was created. U channels, elongate plasti c boxes 2 cm wide by 2 cm deep, were cut to length according to the SPLICER table. The cut channels were placed on top of the working core half and firmly pressed into the sediment. Polypropylene line was pulled along the open face of the U channell to c ut the sediment filled box from the remaining sediment in the core tube. Next the channels were capped and prepared for transport. Image Acquisition S ediment image data were collected using a Geotek multi track core line scan camera, which collects images free from parallax or barrel distortion. T he camera scans the core sections line by line as it moves down a track. Archival core halves were placed one at a time on the core line scanner and a Gretag MacBeth Mini Checker calibration card was placed at the bottom of each core section ( Figure 32 ). The light source of the Geotek was polarized with a film A n additional polarizer on the camera allowed for glarefree imaging. Images were saved as lossless RGB (.bmp or .tif) image files with a full resolu tion of 10 pixels (px) per mm and average file size of ~40 MB per 1.5 m core section. A sample tray was built to hold modern surface sediment samples collected along the water depth transect The tray was loaded with sediment samples and placed on the Geotek multi track line scanner and imaged under conditions identical to those used for scanning the sediment cores (Figure 33).

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30 Red, green, blue color digital images Red, Green, Blue (RGB) color digital images typically consist of a matrix of individual pix els with numerical values that represent the intensity of three hues; Red, Green, and Blue. These pixels have discrete values assigned to them that are dependent on the bit depth of the camera. The range of intensity values that cameras can record is known as the dynamic range. An 8bit color image has RGB values that range from 0 (black) to 255 (white). Conventionally, 0 indicates the darkest possible pixels (pure black) and 255 represents the brightest (pure white) (Russ, 1999). In this system, a blac k pixel has the values (0, 0, 0), a white pixel is coded (255, 255, 255), a red one is (255, 0, 0), and so on. With this system, it is possible to quantify the relative change in hue of an objects surface from reddish to greenish. Similarly, with a grayscale image, it is possible to determine the relative change in intensity from the darkest to lightest areas. L*a*b* c olorspace L*a*b* colorspace divides color images into three components. Lightness is named the L* component where L* of 0 is black and L* of 100 is white. The ratio of green to red is named a* In the a* channel, positive (+) a* levels are indicative of red and negative ( ) values are greenish. Finally the ratio of yellow to blue is named b* where ( ) values are blue and (+) are yellow These ratios do not include the effect of lightness (Francus, 2004). The combination of these two channels a* (+) and b* (+) represents yellow. Sediments shifting from greenish to reddish can be identified by the shif t in a* values from ( ) to (+). Because the sediment core and transect sample images were calibrated, it was possible to perform a trans formation from RGB to L*a*b* colorspace for analysis. The

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31 transformed L*a*b* images were analyzed using the ImageJ pro file macro used for RGB image s. Image Processing and Analysis Post acquisition image processing was performed with ImageJ image analysis software (Appendix A). Because of the limited range of the 8bit sensors, post acquisition normalization was done to compare sections with highly v ariable sediment lightness. Normalization of the image dataset was performed using an algorithm that measured RGB values of the red, green and blue tiles from the Gretag MacBeth Mini Checker from the entire dataset (Figure 3 4) After normalization, the images were cropped, labeled and added to a composite image dataset developed with the SPLICER splice file. Sulfur nodules were excluded from the composite image record because they were thought to have been created by post depositional diagenesis and t herefore are not a proxy for paleoenvironmental or paleoclimatic conditions. Similarly the image dataset was scrutinized and gaps in the core sections, or disturbances due to coring were also excluded from the composite by filling the disturbed area s wi th pure black (0, 0, 0). These quality control decisions were made after examining the sediment core image s, and would not have been possible by visual examination or measurements through the core liner. A composite RGB profile was created using an ImageJ macro. The macro was modified to include a find edges command, and the images were thresholded to estimate granularity, i.e. shifts in grainsize (Figure 35 ). In addition, a L*a*b* (Lightness, a and b ) colorspace conversion and profile was created with a modified version of the macro. Corelyzer was used to visualize the core image composite

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32 dataset at full resolution. Images were used to aid stratigraphic correlation among holes and to project 14C dates from site PI 3 to PI 6 Geochemical Analyses S amples from the surface sediment transect were freezedried and crushed with a mortar and pestle. Total carbon (TC) and total nitrogen (TN) were analyzed using a Carlo Erba NA 1500 C/N/S analyzer. Total phosphorus in sediments (TP) was analyzed using a Bran Luebbe auto analyzer. Inorganic carbon (IC) was measured by coulometric titration using a UIC/Coulometrics 5011 coulometer and a UIC 5240 TIC carbonate autosampler. Percent organic carbon by weight (%OC) was figured as TC IC. Select archival core s ections were analyzed for element concentrations at the University of Minn esota, Duluth by Dr. Erik Brown, using an ITRAX X Ray Fluorescence (XRF) core scanner Core Chronology Samples of wood, leaves, and charcoal were taken from the sediments for 14C dat ing. Samples were pretreated (acidbase acid treatment) and analyzed at the Lawrence Livermore National Laboratory using Accelerator Mass Spectrometry (AMS). Dates were calibrated using Fairbanks et al. (2005) using the online radiocarbon calibration pr ogram Stratigraphic correlation between the magnetic susceptibility records from sites PI 6 and PI 3 permitted use of radiocarbon dates from the PI 3 core in the final age model for the PI 6 composite section. Electron microprobe glass analysis was used to identify known tephra layers and extended the chronology beyond the limits of 14C dating.

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33 Table 3 1. Drilling site summary. Drilling at site PI 9 was stopped after slumping caused high pressure on the drill string and prevented advancement. Wate r Depth Penetration Depth (mblf) Average % Site Latitude Longitude (m) Hole A Hole B Hole C Holes D/E Recovery PI 1 16 59.9706' N 89 47.7396' W 65 94.5 90.3 82.5 89.3 PI 2 16 59.9712' N 89 44.685' W 54 66.5 41.2 82.4 42/68.5 86.3 PI 3 17 0. 2016' N 89 49.24' W 100 96.9 95.3 90 92.9 PI 4 17 0.3342' N 89 50.772' W 150 67.4 46.1 25.4 86.7 PI 6 17 0.0162' N 89 47.0868' W 71 75.9 66.4 66.8 94.9 PI 7 16 59.7234' N 89 47.6844' W 46 133.2 122.8 63.8 92.1 PI 9 16 59.436' N 89 47.6 46' W 30 16.4 91.8 Table 32. Locations of surface sediment samples collected along a water depth transect. Site Latitude Longitude Water Depth (M) TS06 89 47.309' 16 58.469' 1 TS05 89 47.309' 16 58.469' 1.2 TS07 89 47.283' 16 58.54' 1.5 TS08 89 47.336' 16 58.54' 1.5 TS09 89 47.346' 16 58.6' 2 TS10 89 47.357' 16 58.637' 3 TS24 89 41.81' 16 59.662' 5 TS11 89 47.419' 16 58.727' 6 TS12 89 47.429' 16 58.795' 7 TS13 89 47.466' 16 58.884' 8.3 TS14 89 47.497' 16 58.988' 10 TS15 89 47.547' 16 59.134' 12 TS16 89 47.564' 16 59.191' 14 TS17 89 47.527' 16 59.248' 17.7 TS18 89 47.563' 16 59.296' 20.8 TS03 89 49.663' 17 0.317' 23 TS19 89 47.599' 16 59.38' 25.9 TS20 89 47.613' 16 59.48' 32 TS02 89 43.282' 16 59.37' 40 TS21 89 47.663' 16 59.682' 40.6 TS22 89 47.623' 16 59.818' 50 TS23 89 47.542' 17 0.082' 70 TS04 89 49.657' 17 0.324' 108

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34 Figure 31. Flowchart of field data and operations

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35 Figure 32. Gretag MacBeth mini checker calibration card. The lower right square (pure white) was used for image recognition and calibration.

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36 Figure 33 Surface sediments collected along the water depth transect in trays arranged from shallowest water (upper left) to deepest water (lower right). Refer to Table 32 for locations and water depths.

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37 Figure 34 Normalized sediment core images. Top 3 sections prenormalization, bottom 3 are post normalization. From top to bottom cores sections are PI 6 6A 24E 2, PI6 6A 10H 2, and PI 6 6A 7H 2.

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38 Figure 35 Sediment core image granularity threshold images. Top core images are original gypsum dominant, and clay dominant sections characterized by coarse and relatively fine grainsize. The thresholded images below are red where edges indicate a roughness in image texture. Black vertical lines in the top grainsize threshold image indicate areas excluded from the composite record. From top to bottom are sections from cores and PI 6 6B 5H1, and PI 6 6B 2H 2

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39 CHAPTER 4 RESULTS AND DISCUSSI ON Site PI 6 Ch ronology Twenty radiocarbon dates from the PI 6 composite section were used to establish the core chronology (Table 41). Not all radiocarbon ag es were in stratigraphic order. A te p hra layer near the base of the section has a geochemical signature consistent with the Los Chocoyos eruption of Atitlan, which occurred approximately 84,000 ybp. An age depth model was generated by linear interpolation between points (Figure 41). At depths with more than three 14C dates grouped closely together, a single age/depth point was established using mean values for the ages/depths in the group. The date from 6C 6H 1 120121 cm was excluded because of contamination concerns. The date from 6A 20 E 1 45 was beyond the range of 14C dating and was excluded from the mo del. As mentioned, stratigraphic correlation with site PI 3 allowed projection of 14C dates from cores at PI 3 onto PI 6 for development of the PI 6 composite age model (Figure 4 2). Several plateaus in the 14C calibration curve used to convert 14C years to calendar years occur during the termination of the last glacial period and early Holocene. There are two possible volcanic ashes in sediments deposited during the last deglaciation (17 ,000 10,000 ybp) that may provide additional age constraint s Surface Sediments from the Water Depth Transect Transect Image Data Surface sediment samples from the water depth transect varied with respect to L*, a* and b* color channels. Variations in lightness (L*) and the a* channel are more closely correlated than is eit her to the b* variable (Figure 43). Sediments from depths

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40 0 14 m have the highest L* values. Samples from depths >14 m are characterized by lower L* values and are darker than sediments from shallower water. The a* values of sediments from the shallowest water fluctuate between values of 5 and approximately 3.5, indicating that shallowest water sediments may be both reddish (+) and greenish ( ). Sediment sample a* values from depths of 514 m are in the range of 46, representing generally reddish sediments. At depths >14 m, surface sediments range from approximately 0.5 to 2 and are generally greenish. The b* values range from 21 to 31 for samples from 014 m. At greater depths, the sample b* values range from 18 to 25. Transect Geochemistry CaCO3 and organic carbon content were measured on samples from the surface sediment transect. There is an inverse relationship between the two constituents ( Figure 44 ). CaCO3 content in sediments ranged from 50% to 80% of dry mass in samples from depths of 0 20 m. The CaCO3 content dropped to ~40% in samples from 2550 m, and to 5% at the 108m site. Percent organic carbon was highest ~11%, in the sample from 110 m water depth, and ranged from 2 to 8% in samples from 040 m water depth. Percent nitrogen ( %N) and percent organic carbon (%orgC) in surface sediments varied similarly as a function of water depth (r = 0.91) (Figure 4 5 ). Total p hosphorus generally increase d with water depth, ranging from 0.03 to 0.3 mg/g with the highest concentration, 0.6 mg/g recorded at a depth of ~26 m (Figure 46).

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41 Transect Lithology M odern surface sediments are dominated by organic rich (gyttja) deposits in deep water (>20 m) and carbonaterich sediments in the shallow, littoral zone. Sediments from shallowest water sit es contained organic debris, including root material from aquatic macrophytes. Gastropods and coarse material were found in high concentrations of winnowed sediments collected at a water depth of ~20 m. Site PI 6 Sediment Cores Site PI 6 Lithology The sed iment cores are characterized by several lithologic facies including coarse gypsum sands. In addition, gray clay, carbonate turbidites, and sulfur nodules a re present (Figure 4 7) A detailed lithologic description was constructed by Andreas Mller (Fig ure 48 ) (Mller et al. 2010). Coarse authigenic gypsum sands and crystals in some glacial age sections suggest a high evaporation to precipitation ratio (E/P) in Petn at the time of deposition. Sulfur nodules observed in the sediment record are post dep ositional, diagenetically formed facies. Sulfur reducing bacteria have been cultured from the sulfur nodules (Vasconcelos et al. 2006). A bundant hydrogen sulfide at depths in the cores suggests the absence of oxidative metals in the sediments Core Logging Data Density GRAPE density was measured on cores from sites PI 1, PI 2, PI 3, PI 4, PI 7, and PI 9 on site during the field campaign. PI 6 was also logged at the LRC. The PI 6 density record is reported in units of g/cm3 as determined on the Geotek M SCL ( Figure 4 9 ). Data were processed to remove gaps. Total drive recovery was calculated by

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42 subtracting the sum of all MSCL section lengths from the total drive lengths recorded i n the fielddrilling database. The oldest sediments are marked by density fluctuations on millennial to sub millennial scales with values ranging from 1.5 to 1.9 g/cm3. Between ~24,000 and 18,000 ybp, sediment density is low (~1.5 g/cm3). A transition to higher density (~1.8 g/cm3) at 18,000 persists until ~9,000 ybp. The re maining record is marked by a shift to lower density Holocene sediments. GRAPE density values reflect changes in lithology. Clays have density values ~1.5 g/cm3. The density of gypsum rich sediment ranges between 1.8 and 2.0 g/cm3. Changes in density al so reflect gaps such as gas pockets sediment breaks or other disturbances. Because sediment density was measured on unopened core tubes, gaps or other disturbances were not identified until core liners were opened and cores were split. Th is limit s the a ccuracy and utility of GRAPE density. Nevertheless, the measure was still useful for onsite core correlation for making drilling decisions. Magnetic s usceptibility Magnetic susceptibility data are presented as SI units (SI x E06) (Figure 410 ). A spi ke with a maximum of ~200 SI x E06 in the susceptibility record is observed at ~83,000 ybp. It is not associated with a visible ash layer Sediments with low, but variable susceptibility persist through ~25,000 ybp. Between 25,000 ybp and 18,000 ybp v alues are relatively high, ranging from 45 to 50 SI x E06. At 18,000 ybp there is an abrupt transition to lower susceptibility which generally persists through 9,000 ybp. Two intervals of slightly higher susceptibility are exceptions during this period Values ranging from 30 to 40 SI x E06 persist from ~9,000 ybp until present.

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43 XRF data Scanning XRF data were collected for selected sections of PI 6, however these data have not been prepared as a composite record and there is not yet a composite XRF r ecord for the site. A suite of XRF derived metal concentrations is plotted (Figure 4 1 1 ) to illustrate the variability of key earth elements within a core section that displays high variability. These data and their relation to lithologic and image characterizations, are discussed further in Chapter 5. Composite i mage RGB d ata The Green component of the digital images was selected because green light is similar in wavelength to widely cited 550 nm spectrometer reflectance data. Data were normalized to a scale in which 0 represents the darkest pixels and 255 is the brightest value. The green profile illustrates changes in sediment lithology throughout the record ( Figure 41 2 ). The oldest part of the record is marked by fluctuations on millennial and subm illennial scales. The Green profile remains light from ~18,000 to 9,000 ybp. The gray clay transitions to greenish gyttja, and at about 9,000 ybp, the sediment is darker. The Holocene sediments lighten at about 5,000 ybp, with the shift to gray clay. S ediments near the sediment surface are darker, similar to modern greenish brown gyttja found in surface sediments from the deeper parts of the lake. RGB profiles of the surface sediment transect illustrate variability with water depth. Sediments from the shallower littoral zone are light, with values of 150200. At depths > 20 m, however, samples are darker, with values ranging from 50100. The surface sediment sample collected at 110 m water depth had a value <50.

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44 L *a*b* colorspace L *a*b* colorspace anal yses generated profiles from the sediment core images of Lake Petn Itza. The response of the lightness ( L* ) channel of the Lab colorspace of the sediment record was very similar to the individual green reflectance channel ( Figure 4 1 3 ). The oldest part of the a* record is characterized by millennial and submillenial variations and displays a high degree of noise (Figure 4 1 4 ). Minima in the record occur at approximately 41,000 and 21,000 ybp. From the 21,000 ybp minim um until approximately 9,000 ybp, the record displays a trend toward more positive values but with significant variability during the climb. An abrupt decrease in a* is observed at approximately 9,000 ybp after which the record stabilizes and a* begins to increase. The b* channel (Figure 4 1 5 ) shows patterns that are similar to those of green reflectance and L* The b* record, however, is less variable than either the L* or green reflectance. PI 6 granularity G rain size analys e s are presented as a proportion of a 1cm wide cross secti on of the core composite image area that was thresholded after being processed with a find edges command (Figure 41 6 ). The earliest part of record is characterized by mostly smooth surfaces except for 12 kyr intervals at 55,000 ybp, 53,000 ybp and 45,000 ybp. A transition to sediments with high granularity occurs at ~40,000 ybp, after which there is an increase in granularity through ~25,000 ybp. Between 25,000 and 18,000 ybp the sediments were generally smooth. Between 18,000 and 15,000 ybp there is a shift in values that suggests a moderate decrease in granularity A minimum in granularity occurs at about 15,000 ybp. Since then, granularity oscillates, with alternating smooth

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45 and rough surfaces through ~9,000 ypb. Following the PleistoceneHolo cene transition there is a shift to much smoother surfaces typical of the modern deepwater sediment.

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46 Table 4 1 Dates and tie points used to develop the chronology for site PI 6 including sample, depth, 14C dates positions AMS 14C ages were measured at the Lawrence Livermore National Laboratory. Accession # Site hole coretype section Depthinterval Depth (mcd) 14C yr BP Age (cal yr BP) 125895 6C 3H 1 141.5 cm 8.076 3,920 35 4,376 53 125903 6C 3H 1 141.5 cm 8.076 3,905 35 4,355 61 125896 6B 4H 2 77.5 cm 10.406 8,655 30 9,579 31 125904 6B 4H 2 77.5 cm 10.406 8,630 60 9,572 52 131225 6C 4H 1 59 cm 10.436 7,98 5 40 8,882 102 131226 6C 4H 1 101 cm 10.856 9,040 35 10,213 16 128611 6B 5H 2 33 cm 13.354 11,290 60 13,125 72 128613 6B 5H 2 39 cm 13.414 11,380 140 13,229 154 131224 6B 5H 2 85 cm 13.874 11,390 50 13,236 74 128612 6C 5H 2 7 cm 14.448 12,460 60 14,39 6 150 131223 6C 6H 1 120 cm 17.12 12,280 60 14,079 95 125897 6A 7H 1 128 cm 20.026 14,130 120 16,537 212 125898 6C 8H 2 6 cm 23.636 17,650 240 20,896 321 125899 6C 9H 1 62 cm 25.729 19,990 180 23,880 217 125900 6A 11H 2 145 cm 33.733 30,700 3600 36,00 0 3663 125901 6B 12H 1 82.5 cm 33.828 29,120 170 34,536 224 125905 6B 12H 1 82.5 cm 33.828 29,010 170 34,421 222 126525 6B 12H 1 138.5 cm 34.388 28,040 470 33,406 517 126526 6C 14H 1 80.5 cm 41.303 39,000 700 43,855 634 126528 6B 15H 1 60 cm 42.762 35 ,900 1200 41,145 1103 126527 6A 15H 2 90.5 cm 45.307 38,100 1100 43,080 967 126529 6A 16H 2 85 cm 46.879 40,500 2600 126530 6A 20E 1 4 cm 57.912 54,000

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47 Table 4 2 Composition of surface sediments along the water depth t ransect All samples w ere collected using a clamshell dredge. Sample ID %N %C %CaCO 3 %orgC Total P (mg/g) Water Depth ( m ) TS06 0.15 8.56 55.92 1.85 0.064 1 TS05 0.06 7.58 51.83 1.36 0.031 1.2 TS07 0.12 9.25 60.42 2.00 0.039 1.5 TS08 0.16 8.17 50.08 2.16 0.056 1.5 TS09 0.26 9.99 54.67 3.43 0.050 2 TS10 0.29 10.90 66.92 2.87 0.080 3 TS24 0.46 14.17 70.17 5.75 0.171 5 TS11 0.71 15.88 68.50 7.66 0.152 6 TS12 0.21 11.24 69.42 2.91 0.068 7 TS13 0.32 13.82 80.17 4.20 0.086 8.3 TS14 0.39 14.19 71.58 5.60 0.204 10 TS15 0.20 1 3.08 70.58 4.61 0.047 12 TS16 0.18 12.91 64.83 5.13 0.061 14 TS17 0.39 13.60 72.33 4.92 0.240 17.7 TS18 0.28 12.80 76.58 3.61 0.250 20.8 TS03 0.32 11.23 57.46 4.34 0.160 23 TS19 0.60 13.41 57.42 6.52 0.599 25.9 TS20 0.25 8.45 39.17 3.75 0.213 32 TS0 2 0.55 9.87 32.67 5.95 0.305 40 TS21 0.53 12.43 40.17 7.61 0.264 40.6 TS22 0.51 11.53 20.75 9.04 0.124 50 TS23 0.69 12.37 19.92 9.98 0.312 70 TS04 0.73 11.96 6.58 11.17 0.323 108

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48 Age (Years BP) Age (Years BP) Figure 41. PI 6 and PI 3 ra diocarbon ages and composite PI 6 agemodel. A. Radiocarbon dates calibrated using Fairbanks et al. (2005) versus mcd for Sites PI 3 (blue) and PI 6 (red). A sample at 59.44 mcd yielded an infinite radiocarbon age (>54 kyr). Green dots represent the positi on of tephra layers. CGT = Congo Tephra; Guasal1 = Guatemala El Salvador Tephra 1; ACT = Arce Tephra; LCY = Los Chocoyos Tephra B. Combined radiocarbon dates from Sites PI 3 (blue open circles) and PI 6 (red open circles) based upon correlation of the magn etic susceptibility records in Fig. 42. Age model (line) was derived using a weighted fit through selected age depth points from Sites PI 3 and PI 6 and three ash layers (CGT, Guasal1 and LCY). After Hodell et al. (2008)

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49 Figure 42. Magnetic susceptibi lity of PI 3 and PI 6. ( L ower panels) Spliced magnetic susceptibility records from Sites PI 3 (red) and PI 6 (blue). (Upper panel) Comparison of magnetic susceptibility records after the PI 3 record was correlated to the mcd scale of PI 6.

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50 0 20 40 60 80 100 120 10 20 30 40 50 60 70 80 90 -4 -2 0 2 4 6Sediment surface sample L*a*b* vs depth L* a* b*Depth (m)L*, b* a* Figure 43. S urface sediment transect L*a*b* versus water depth (m). Samples were collected using a clamshell dredge. After Hodell et al. (2008)

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51 0 20 40 60 80 100 120 0 20 40 60 80 100 0 2 4 6 8 10 12Surface sediment geochemistry (% CaCO3, % organic C) % CaCO3 % organic carbonDepth (m)% organic C % CaCO3 Figure 44 Surface sediment t ransect %CaCO3 and % organic carbon v ersus water d epth. Samples from the shallowest wat er sites had a large amount of plant material, reducing the %CaCO3.

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52 0 20 40 60 80 100 120 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0 2 4 6 8 10 12Surface sediment transect (% N, % organic C) % nitrogen % organic carbonDepth (m)% N % organic C Figure 45 Surface sediment t ransect %N, and % organic carbon are highly correlated (R= 0.91) in surface sediment transect samples.

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53 0 20 40 60 80 100 120 0 0.1 0.2 0.3 0.4 0.5 0.6Surface sediment geochemistry (total phosphorus (mg/g)) Total P (mg/g)Depth (m)Total P (mg/g) Figure 46. Surface sediment t ransect total phosphorus.

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54 a. b. c. d. e. f. Figure 47 Digital i mages of various lithologic units from Lake Petn Itz cores (scale interval is 1 cm) a. brown organic rich gyttja b. gray clay, c. gypsum interbanded gray clay, d. carbonate tu rbidites within greenish clay, e. sulfur nodules, f. limestone gravel.

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55 Figure 48 Stratigraphy of PI 6 (with permission from A. Mller ) A. PI 6 lithologic units and 14C ages. B. Magnetic susceptibility and lake level inference.

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56 1 1.2 1.4 1.6 1.8 2 2.2 0 10000 20000 30000 40000 50000 60000 70000 80000PI-6 density record vs time (ybp) densitydensity (g/cm3)Age (ybp) Figure 49. PI6 composite GRAPE density record (g/cm3). Black line represents original data, the red line is a 100 point running mean. After Mueller et al. (2010)

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57 -20 0 20 40 60 80 100 120 140 600 800 1000 0 20000 40000 60000 80000magnetic susceptibility (SI x E-06) magnetic susceptibility (SI x E-06)magnetic susceptibility (SI x E-06)Age (ybp) Figure 410. PI 6 composite magnetic susceptibility r ecord (SI x E06).

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58 0 50,000 100,000 150,000 200,0000 2,000 4,000 6,000 8,000 10,0000 200 400 600 800 1000 1200 1400PI-6-6C-4H1 XRF data vs depth in core (mm) Ca Fe Sr Si S K Ti MnCa, Fe, SrSi, S, K, Ti, Mndepth in core (mm) Figure 41 1 Selected XRF data (kcps) from site PI 6 6C 4H 1 plotted versus depth in the core section (mm).

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59 0 50 100 150 200 250 0 20000 40000 60000 80000PI-6 composite green color reflectance data green Intensitygreen intensityAge (ybp) Figure 41 2 PI 6 Composite g reen color reflectance data versus age raw data (ybp).

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60 Figure 413. L* image data versus age (ybp). Original values are light grey, and a 100 point running mean is plotted with a thick dark blue line.

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61 Figure 414. a* image data versus age (ybp). Original values are light green, and a 100 point running mean is plotted with a thick dark green line.

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62 Figure 415. b* image data versu s age (ybp). Original values are gold, and a 100 point running mean is plotted with a thick black line.

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63 0 10 20 30 40 50 60 70 80 0 20000 40000 60000 80000Image-derived granularity vs time (ybp) % area (granularity threshold)Age (ybp)% area Figure 41 6 Image derived granularity versus age (ybp)

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64 CHAPTER 5 INTERPRETATION OF SE DIMENTS FROM SITE PI 6 Modern Sediment Properties Modern Limnological Setting Aerial photographs of lakes in the Petn region, notably Petn Itz, Quexil, and Salpetn display a halo of lighter colored sediments in the shallow, littoral zones of the lakes. This is consequence of accumulation of bioinduced carbona te in shallow water (Brenner, 1994). Lake Petn Itzs north basin has a gradually sloping southern littoral zone, whereas the north shore is steeper and has a narrow littoral zone. In the modern lake, the southern, shallow water zone is the major region of carbonate accumulation. G astropod and ostracod shells are abundant on the lake floor at a water depth of 20 m in the southern basin. This shell accumulation may be explained by the winnowing of fine sediments and the concentration of shell material at this water depth, associated with epilimnetic water column circulation ( Figure 51). Lightness and E/P My hypothesis is that shifts in the location of the carbonate depositional zone cause changes in sediment core lightness and that such changes in core lightness indicate changes in water depth. Hodell et al. (2007) reported similar relations between water depth and sediment lightness in the relatively shallow (zmax<25m) Lake Punta Laguna in the northeastern Yucatan Penin sula, Mexico. Shallow water sedi ments in both Punta Laguna and Petn Itz contain high amounts of bio induced carbonate and are lighter In the deeper areas of these thermally stratified lakes, dissolution of carbonate under relatively lower pH conditions yields sediments that have higher organic matter content and are hence darker.

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65 My hypothesis is that when lake level dropped in the past, the zone of carbonate deposition migrated toward deeper areas of the lake, changing the color and hue of the deposited sediment s. Thus, past lake l evel can be inferred using changes in lightness and hue of the sediments. Lighter sediments are indicative of lower water levels, and hence an increase in the E/P ratio. Confounding Factors The original hypothesis is confounded when using the composite se diment core record lightness of PI 6. The variations in sediment lithology and the presence of gypsum, carbonate turbidites and variations in the clay all influence sediment core lightness so that sediment core lightness alone is not an indicator of water depth in Lake Petn Itz. Surface Sediment Transect Samples The goal of collecting modern surface sediment samples along a water depth transect was to evaluate the hypothesized relation of changes in sediment lightness and geochemistry to water depth, and to calibrate the hypothesized paleoclimatic signal in changes of sediment core image lightness. The modern Lake Petn Itz surface sediment samples show a relat ion between water depth, carbonate content and lightness of the sediments (Figures 5 2 5 3 ). Sediment Cores Core Images Core images are representations of the sediment record. Image hue, brightness, and structure are functions of the biological, geochemical, and lithological characteristics of the sediment as well as the depositional environment and perhaps diagenetic changes. Understanding the relation between an image and the

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66 biogeochemical properties of sediments is the first step in using images as proxies for paleoenvironmental conditions. Variations in Sediment Lithology The diversit y of facies within the PI 6 sediment cores suggests that modern surface sediment samples do not capture the whole range of depositional and lithologic environments that existed in the lake through time. This finding makes sense in light of the major climat e changes during the last glacial period and termination, which lack analogs i n modern Lake Petn Itz (e.g. deglacial gypsum deposition). Carbonaterich turbidite layers are observed in several cores, but the record does not suggest direct climatic link age to the turbidites. Holocene gray clays are believed to be largely a consequence of anthropogenic erosion of detrital material into the lake (Hodell et al., 2000) whereas glacial age clays are thought to have been delivered by increased precipitation. Turbidites, gypsum layers and sulfur nodules are lighter than clays, but they do not influence sediment lightness in a manner that corresponds to a direct relation with E/P. Because of these complex depositional and post depositional changes to sediments lightness alone was not linked to changes in E/P T here are no surface sediment lithologic units with modern day analogs of gypsum sands or sulfur nodules. Although the gypsum sands lack a modern day analog in Lake Petn Itz, precipitation of gypsum has been observed in nearby Lake Salpeten and in Lake Chichancanab, farther north on the Mexican part of the Yucatan Peninsula (Hodell et al. 2001). Dryer conditions favor greater E/P and concentrate gypsum CaSO4H2O and other salts in Lake Petn Itz. The granular, gypsum rich intervals are not significantly lighter than the clay/carbonate or turbidite units in the cores. They are however, easily

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67 identified using find edges as part of an algorithm to estimate granularity of the sediments (i.e. roughnes s of the core surface). XRF Data Scanning XRF data collected from sections of the PI 6 sediment record provide nearly continuous, non destructive measurements of elemental concentrations. The data have not yet been assembled into a composite record, but individual core section data were used to evaluate changes in lithology and optical properties to understand the elemental and depositional conditions influencing the sediment core record. Multivariate analysis suggests that certain detrital elements are highly correlated within the sediment record of PI 6 (Table 51, Figure 5 4). Titanium and iron are extremely closely correlated, and both are correlated to silicon and manganese. Calcium is slightly negatively correlated with the detrital elements. L*a *b* Data Evaluation and Interpretation L*a*b* data provide an opportunity to independently evaluate changes in lightness and hue of sediments. Shifts in a* values are well suited to evaluating changes in sediment redox conditions as reddish oxidative envi ronments are more positive in a* and reducing environments with iron are often greenish. Sediment redox conditions and mineralogy have been studied using a* variations in marine cores (Nagao, 1992), and pigments of lake sediments and marine sediments have been used to understand changes in redox conditions ( Lyle 1982, Engstrom, 1985). In the surface sediments from the shallowest water the a* data from surface sediment samples suggest they are greenish. This may be due to mineralogy in the littoral zone, or the presence of macrophytes. In water depths that range from 5 to 14 m, the samples have the highest a* values, and are reddish in color. This may indicate

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68 that sediments in this depositional environment are within an oxidizing zone. Surface sediment samples in water depths >14 m have more negative a* values and indicate greener gyttja, which is suggestive of an anaerobic depositional setting. A selected core section from site PI 6 is presented with XRF and L*a*b* image data to illustrate the common elemental variations among the lithological units (Figure 55 to 5 7). Using scanning XRF data from surface sediment samples, the following relations were identified between the sediment and a* values: 1) Carbonates are characterized by higher a* values. 2 ) Clays are characterized by lower a* values under reducing conditions and display more positive in a* values under oxidizing conditions. This may be due to the presence of manganese or the oxidation state of Mn and Fe. 3) Gypsum layers are characterized by higher a* values. 4) Oxygen isotopic data, which are influenced by changes in E/P, and a* values ar e correlated in PI 6 sediments (Figure 5 8). Magnetic Susceptibility Magnetic susceptibility may reflect changing climate conditions in that E/P influenc es weathering and input of allochthonous clays to the lake. In addition, magnetic susceptibility is known to vary with particle size. Susceptibility spikes coincide with the presence of volcanic ash and accessory minerals. Gypsum rich layers are charact erized by low magnetic susceptibility and relatively large particle size. Granularity The proxy for particle size ( granularity ) provides a rapid estimate of roughness of the composite coresurface. This measure is presented as a ratio of the area, and is not an absolute measure of the particle size or grainsize. Because of the relation

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69 between susceptibility and particle size, the grainsize proxy and susceptibility are inversely related (Figure 59). Because of the great difference in grain size between g ypsum rich intervals and clay dominated sediments, the granularity proxy was very useful to classify the lithology of site PI 6 cores.

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70 Table 51. Multivariate correlations between elements of core sections from site PI 6. Si S K Ca Ti Mn Fe Sr Si 1 0 .6894 0.6933 0.4403 0.8889 0.8111 0.8867 0.7126 S 0.6894 1 0.632 0.2804 0.6809 0.7305 0.6869 0.5282 K 0.6933 0.632 1 0.2243 0.6535 0.7392 0.6676 0.6044 Ca 0.4403 0.2804 0.2243 1 0.6662 0.2672 0.6725 0.4392 Ti 0.8889 0.6809 0.6535 0.666 2 1 0.7603 0.9962 0.7488 Mn 0.8111 0.7305 0.7392 0.2672 0.7603 1 0.7682 0.6711 Fe 0.8867 0.6869 0.6676 0.6725 0.9962 0.7682 1 0.7559 Sr 0.7126 0.5282 0.6044 0.4392 0.7488 0.6711 0.7559 1 Figure 51 Cartoon depicting stratification of L ake Petn Itz ( water temperature profile taken on 13 August 2002 (Hillesheim et al., 2005) ) The thermocline at approximately 30 m water depth is associated with an erosional feature due to subaquatic currents (Anselmetti et al., 2006 figure modified by A. Mller, 2009). Dissolved oxygen is plotted for May (solid line) and August (dashed line) 1980 (unpublished data).

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71 0 20 40 60 80 100 120 0 20 40 60 80 100Surface sediment geochemistry (CaCO3) vs depth (m) CaCO3Depth (m)% CaCO3 Figure 52. CaCO3 content of modern surface sediment samples.

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72 0 20 40 60 80 100 120 10 20 30 40 50 60 70 80 90 -4 -2 0 2 4 6Surface sample L*, a* vs depth L* a*Depth (m)L*a* Figure 53. Surface sample L* and a* vs depth. H ighest (reddish ) a* values circled. Right plate shows transect sample images in depthorder with lines showing select correlating points on plot.

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73 Figure 54. Multivariate correlation matrix of PI 6 XRF data. Ellipses are calculated and plotted using JMP (by SAS) so ftware for multivariate analysis.

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74 0 50,000 100,000 150,000 200,000 -500 0 500 1,000 1,500 2,000 2,500 3,000 3,5000 200 400 600 800 1000 1200 1400PI-6 6C-4H1 XRF data vs depth in section (mm) Ca Fe Sr TiCa, Fe, Sr (mg/kg)Core position (mm)Ti (mg/kg) Figure 55. PI6 6C 4H 1 XRF Ca, Fe, Sr, and Ti data (kcps). Clay, dominant in the core section from 0 to 1000 mm has high concentrations of Ti, and Fe, which are detrital in Lake Petn Itz. Carbonate turbidites are low in Fe and Ti but elevated in Ca between 300 and 400 mm section depth. Gypsiferous intervals from 1000 to 1400 mm depth are characterized by lower levels of detrital elements (Fe, Ti) but are elevated in Ca, and Sr.

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75 0 2,000 4,000 6,000 8,000 10,000 0 200 400 600 800 1,000 1,200 1,4000 200 400 600 800 1000 1200 1400PI-6 6C-4H1 XRF data vs depth in section (mm) S Mn K SiS, Mn (mg/kg)Core position (mm)K, Si (mg/kg) Figure 56. PI 6 6C 4H 1 XRF S, Mn, K, and Si data (kcps). The clays in the top of the core section are higher in Si, and K, both indicative of detrital material. Clay between 500 and 1000 mm in the core section has higher levels of manganese. Gypsum in the bottom of the core section has elevated levels of sulfur.

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76 0 20 40 60 80 100 -8 -6 -4 -2 0 0 200 400 600 800 1000 1200 1400PI-6 6C-4H-1 L*a*b* data L* b* a*L*, b*a*Core position (mm) Figure 57. PI 6 6C 4H 1 L*a*b* data. Carbonate turbidites have elevated L* values and drops in a*. The greenish clays from 500 to 900 mm in the core section have lower a* values.

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77 3 4 5 6 7 8 -10 -5 0 5 10 15 12000 16000 20000 24000 28000 32000 36000 40000 44000PI-6 18O and a* vs time (ybp) 18O a* 18OA*Age (ybp) Figure 58. PI 6 c omposi te oxygen isotopic data (blue) courtesy of Jaime Escobar (in prep), and a* color data.

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78 -20 0 20 40 60 80 100 120 140 600 800 1000 0 20 40 60 80 0 20000 40000 60000 80000Granularity and magnetic susceptibility (SI x E-06) magnetic susceptibility (SI x E-06) granularity magnetic susceptibility (SI x E-06)% AreaAge (ybp) Figure 59. PI 6 Composite estimate of grain size proxy (using the find edges based algorithm). Magnetic susceptibility composite data (courtesy of Dr. A. Gilli)

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79 CHAPTER 6 CORRELATION TO OTHER CLIMATE RECORDS Regional Paleoclimate Bradbury (1997) proposed that strong inputs of winter Pacific precipitation accounted for wet conditions in the central Mexican highlands during the last glacial period. The lowlands of Petn were thought to have been dry during the last glacial maximum. Interpretation of pollen records from Lake Quexil, Guatemala suggested that the climate in the region was cool and dry (Leyden et al. 1993). The Pleistocene portion of the Quexil section, however, was poorly dated, leaving uncertainties about the timing of vegetation shifts. Magnetic susceptibility, grainsize, and the green reflectance of sediments from Lake Petn Itz suggest that the last glacial maximum (2518 kybp) was cool and wet ( Figure 61). At ~18,000 ybp the sediment record suggests a change to cool, dry climate. During the deglaciation, two periods of increased magnetic susceptibility coincide with clay dominant sediments (Bush et al. 2009). The marine Cariaco Basin sediments, off Venezuela, have been studied to examine the shifts in the position of the ITCZ. The basin sediments are in an anoxic depositional environment and display changes associated with fluctuations in productivity due to increased upwelling. The 550 nm spectral reflectance in sediment cores is interpreted to reflect past climate change. Increases in the reflectance values are linked to increased upwelling and a southerly shift in the annual mean position of the ITCZ. The PI 6 a* channel is plotted on a n independent timescale with Cariaco 550 nm reflectance (Figure 62). Between ~48,000 and ~23,000 ybp the PI 6 record alternates between gypsum and clay rich intervals during stadials and interstadials,

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80 respectively, that correlate well with other recor ds including Cariaco (Mller et al. 2009). The a* variable illustrates the millennial fluctuations that are influenced by these changes in lithology. The PI 6 lithology and a* values indicate that the paleoenvironmental conditions of Lake Petn Itz may be interpreted using the image data, and that the a* variable may be influenced by shifts in the depositional regime and redox conditions. Global Paleoclimate and Timeseries Analysis The PI 6 record exhibits orbitally influenced precessiondriven variabi lity (Bush et al. 2009), however, a suite of wholerecord timeseries analysis has not yet been generated. The PI 6 image data provide a continuous, highresolution record that should prove useful for investigating such changes and conducting timeseries analysis. Spectral analysis was performed on linearly spaced data using AutoSignal (Figure 6 3). A low frequency component was removed using the cubic spline normalization function AutoSignal (Figure 64). The resulting spectrum exhibits statistically significant signals at frequencies of 0.021, 0.043, 0.103, and 0.189, which correspond to periods of ~48, ~23, ~9 and ~5 ky respectively. Wavelet analysis also captures some of the statistically significant components of the a* dataset (Figure 65) The a* variable was filtered with a 20kyr filter using Analyseries ( Berger 1992, Paillard et al. 1996) and was plotted along with L* and aged images. The images have been stretched and compressed according to the age model so that they correspond with the agescaled data (Figure 66). Cross correlation of the filtered 20ky component indicates that the a* variable is coherent and inphase with the summer insolation at 17 degrees north (Figure 67). A cross spectral analysis was performed to test the correlation and the correlation ranges from 0.64 to 0.93 (Figure 68)

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81 Figure 61. Pollen accumulation, charcoal concentration, magnetic susceptibility from site PI 6 (Bush et al., 2009), color reflectance from site 1002 (Cariaco Basin Peterson et al., 2000), a (Grootes et al., 1993).

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82 Figure 6 2 PI 6 a* data plotted vs time (light green are original data and the dark green line is a 100point running mean) and the Cariaco 550 nm reflectance (Peter son et al., 2000) plotted on its independent time scale. H0 H1 H2 H3 H4 H5 H6 H0 H1 H2 H3 H4 H5 H6

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83 Figure 63. a* frequency spectrum, colored horizontal bars indicate significance (red= 99.9, yellow= 99, green= 95, teal=90, white=50).

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84 Figure 64. a* frequency spectrum following cubic spline f ilter to remove low frequency signal. Colored horizontal bars indicate significance (red= 99.9, yellow= 99, green= 95, teal=90, white=50).

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85 Figure 65. a* wavelet surface plot, statistical envelope shown with curved lines and transparent mask.

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86 Figure 6 6 L*a* plots of PI 6 and agemodel fitted images showing the relation between composite sediment core images and the L* and a* variables. The a* data are plotted with a 20kyr filtered component that corresponds with solar insolation.

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87 Figure 67. S ummer insolation at 17 degrees north (Analyseries) plotted vs age (kybp).

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88 Figure 68. Cross correlation between filtered a* and summer insolation at 17 degrees north.

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89 CHAPTER 7 SUMMARY AND CONCLUSI ONS The sediment core lithology and image data suggest that Lake Petn Itz continuously held water throughout the past ~85,000 years. Data from several proxies, including image data, provide evidence for a wetter climate regime between 25,000 and 18,000 ybp. Variations in lightness may be less sensitive to shifts in sediment type between facies such as gypsum and carbonaterich clay, but shifts in hue allow for the comparison of these sediments. The hypothesis that lightness of sediments is correlated to climatic signals was rejected. Image data are influ enced by the biogeochemistry and depositional environments of a lake, as well as post depositional diagenetic changes. Although lightness was not suitable for paleoclimatic interpretation, the a* variable is correlated to shifts in geochemical properties of modern day sediments and to historic changes in solar insolation, when measured in cores. Modern surface sediments did show a relation between geochemical properties, lightness and a*. The a* image data are influenced by the oxidative state of the sedi ments, and provide a mechanism for evaluating changes in the varied lithologies. Some clay layers were more red and others more green. The shifts in hue of these clays may be due to changes in redox conditions. These variations could be evaluated with a complete series of XRF data for site PI 6. This work suggests that sediment core images from Lake Petn Itz are well suited to the investigation of paleoenvironmental conditions and that the a* variable is well suited to understanding millennial scale va riations and orbital influenced variability in sediments. Image analysis of granularity is useful for classifying sediment lithology

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90 and provides an approximation for grainsize in the sediments. Analyses of both granularity and L*a*b* in sediments from Lake Petn Itz were performed nondestructively and at high resolution. In the future, other researchers will have the opportunity to analyze the original images. The digital files will not degrade with time, enabling new algorithms or techniques to be applied to the same images used in this study. Limitations of Images as Paleoclimatic Proxies The image data collected for this project were limited by the dynamic range of the Geotek hardware. The camera used in this study had a dynamic range of 8bits (o r 0 255). Normalization of images with very light sediments led to saturation of some pixels. The degree of lightness extended beyond the range of possible values. Cameras with 16bit and even 32bit greyscale capabilities are currently available, but such cameras are still expensive. Normalization allowed comparison of sediment images in this study, but improvement in the dynamic range of imaging hardware would allow direct comparison of extremely light and dark sediments on a continuous scale. An ad ditional limitation of the method in this study was that images were influenced by a wide range of depositional and post depositional processes. Because the sediments are not composed solely of varying proportions of clay, carbonate, gypsum, and organic m atter, the assumption that lightness is controlled largely by lake level and carbonate deposition is not valid, especially in the Pleistocene deposits. Estimations of grainsize (granularity) were useful to identify regions of gypsum deposition and would n ot have been as easily measured without automated image processing.

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91 Future Work As the remaining sediment cores collected during the Petn Itz Scientific Drilling Project are processed, digital core images and image analysis will continue to provide a rap id means of sediment characterization. With the integration of NCLIP, the successor to SPLICER, the Corewall Suite images will provide the backbone for collaborative interpretation of sediments. Additional radiocarbon dates will improve core chronology a nd permit a more accurate interpretation of the data during the Pleistocene deglaciation. With a more tightly constrained 14C profile, oxygen isotopic signatures may be useful to determine source of the precipitation during events that occurred at 15,000 and 12,000 ybp.

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92 APPENDIX A SOFTWARE USED Field Software Drilling Information System The primary field database was designed and implemented by the Operational Support Group (OSG) of the International Continental Scientific Drilling Program (ICDP) and cust om tailored for the drilling operations prior to field deployment. Two database curators were trained by Ronald Conz of the OSG in December of 2005. This database was critical for keeping track of drilling information, Multi Sensor Core Logger (MSCL), a nd smear slide data. The science team also used the software to update the project web page: http://www.icdp online.de/contenido/icdp/front_content.php?idart=1082 SPLIC ER Splicer was used for stratigraphic correlation on site, using the GEOTEK MSCL data. The software runs on Unix, and for this project much effort expended by University of Florida Geosciences guru Ray G. Thomas. Luckily, Rays expertise prevailed, and Splicer was successfully ported through the X environment on an Apple iBook. Splicer was designed by Peter DeMenocal and Ann Esmay for the Ocean Drilling Program (ODP). This software is currently being overhauled and the successor is NCLIP, one part of t he Corewall suite. SPLICER http://www.iagp.net/joi/index.html Please note that this is far from a plug and play installation. Proceed with caution! NCLIP http://www.iagp.net/NClip/Binaries/

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93 Image Processing and Analysis The large file sizes prevent current computers from opening core composite images at full resolution. In the case of the Petn Itz cores, a full resolution composite core image for site Pi 6 is well over 2 Gigabytes ( GB ) When combined with multiple holes and sites, a dataset of full resolution images cannot be rapidly transmitted over current computer networks. One of the best ways of transferring such data locally is the use of a sneakernet. A sneakernet describes moving external storage devices from location to location by physically carrying them. Many large image files necessitate the automation of tasks and batch process ing of individual section images. However, becaus e the needs of these analyses are unique, software packages such as Adobe Photoshop are not adequate for analysis and processing. The first step in performing the digital image analysis was to normalize the core images. Despite the assembly line approac h to core curation at the Lacustrine Core Repository ( LRC/LacCore), there is still variability in the imaging conditions over time. The variability is most visible (pun intended) when imaging of cores is performed over several days or by different users. One of the essential safeguards during the image acquisition process is the scanning of the same, uniform, color calibration plate with each core section. Acquiring an image of the tile is critical for understanding the variability of the relative hue or color of the sediments and fundamental for creating an accurate composite core image or image dataset. Using the LRC standard core acquisition protocol the calibration tile is placed near the bottom of the core section (the right side) and it is placed so that the white gray tiles are located along the bottom of the core image. The calibration plate must be clean, free of debris and on the same plane as the sample being analyzed.

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94 ImageJ ImageJ is an opensource Java based program funded by the National Institutes of Health, and is freely available for download at: http://rsb.info.nih.gov/ij/. It was the primary software used for image analysi s and normalization. Due to limitations of current computing hardware, it is not yet possible to manipulate image datasets spanning several 10s of meters of sediment core. Because images are scanned in individual sections they may be handled individually. The design and use of macros (small scripts) to automate image normalization and analysis to perform tasks requires an initial investment in time, but upon development, the macros may be easily and rapidly used to perform the operations on other image datasets. All image processing discussed in this manuscript was performed in ImageJ. A series of macros was designed for image processing of large image datasets for the Petn Itz Scientific Drilling Project (PISDP). To measure the degree of variability across the image set, a macro was written to measure the values of the Red, Green, and Blue colored squares on the digital image. However, because each image is different in length, the image position of the calibration color tiles was unknown. The f ollowing ImageJ plug ins were used and are necessary for the use of macros included in this thesis: Stack Combiner http://rsb.info.nih.gov/ij/plugins/combiner.html stackreg http://bigwww.epfl.ch/thevenaz/stackreg/ turboreg http://bigwww.epfl.ch/thevenaz/turboreg/ RGB Measure http://rsb.info.nih.gov/ij/plugins/rgb measure.html Colorspace Converter http://rsb.info.nih.gov/ij/plugins/color spaceconverter.html

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95 Matlab Matlab was us ed for data manipulation and plotting. Corelyzer and Corewall Several limnologists and sedimentologists who have worked in the field for a number of years have seen the effects of a dry coldroom and poorly handled cores. One of the great aspects of images, and especially properly collected digital core images, is that the sediment image will remain exactly the same as when it was collected, for as long as the data can be stored. This allows for maintenance of a virtual core, which scientists may consul t to review stratigraphy or select depths where samples are to be collected. Core images are poised to be the backbone of a suite of applications now known as Corewall. This suite will allow users to view enormous image datasets and other data, which will enable collaborators to comment and share images in real time. Currently, the visualization tool is functioning and is known as the Corelyzer. This software allows the science team to load an image dataset (at full resolution) and then view the image dataset on a common personal computer, as opposed to the considerably more costly commercial alternatives. Corewall will incorporate several aspects of previous software packages into a tool for presenting data and images. The software should also allow researchers to collaborate remotely. url: http://www.evl.uic.edu/cavern/corewall/about.html wiki: http://sql core.geo.umn.edu/CoreVault/cwWiki/index.php/Main_Page

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96 Analyseries Analyseries is a MacIntosh time series analysis tool by Didier Paillard, LSCE. The latest version of AnalySeries is compatible with Mac OSX and is available at the LSCE website. url: http://www.lsce.ipsl.fr/logiciels/index.php

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97 APPENDIX B PALEOLAKE HIGH STAND S During the field campaign of the Petn Itz Scientific D rilling P roject lacustrine deposits were identified by the presence of aquatic gastropods at elevations ranging from 15 to 20 meters above the modern lake level (Grzesik Curtis, Escobar unpublish ed data). These samples may provide the means for stratigraphic correlation of extreme lake level highstands to the studied paleo record. Initial analysis of gastropods from the high elevation deposits revealed oxygen isotopic signatures that are slightly 18O than th ose of modern day lake gastropods. This va lue may serve as a fingerprint to identify down core gastropods that are contemporaneous with the shells that were deposited above the modern lake surface R esults of this research increase understanding of an unknown aspect of the history of Petn lakes which have been studied during the past 30 years (Deevey 1978). Understanding the highstand timing and magnitude is something that will allow more accurate modeling of the regional and global climate. The Petn Itz Scientific Drilling Project will benefit from this research as interpretation and analysis of longer cores begins. Figure B 1. Hydrobiidae gastropods (1mm ticks)

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98 Figure B 2. A cartoon illustrating the implicatio ns for a 20meter rise in the level of Lake Petn Itz. The dark area shows the extent of the modern lake. Lighter shaded area shows areas that would be flooded by a 20m rise in water level. (white dot illustrates sample locality)

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99 APPENDIX C SITE PI 3 Site PI 3 was split and imaged at the LRC during the Summer 2006 sampling party, but it was not presented in this thesis because of concern over slumping below 32 meters, and the lack of a well defined chronology. Image data were used for stratigraphic co rrelation with the Corelyzer application.

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100 Figure C 1 PI 3 composite lithological description by Andreas Mlle r.

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101 LIST OF REFERENCES Anselmetti FS, Ariztegui D, Hodell DA, Hillesheim MB, Brenner M, Gilli A, McKenzie JA, Mller, AD (2006) Late Quaternary climate induced lake level variations in Lake Petn Itz, Guatemala, inferred from seismic stratigraphic analysis. Palaeogeogr Palaeoclimatol Palaeoecol 230: 52 69 Binford MW, Brenner M, Whitmore TJ, HigueraGundy A, Deevey ES, Leyden BW (1987) Ecosyst ems, paleoecology, and human disturbance insubtropical and tropical America. Quat Sci Rev 6: 115 128 Brenner M (1994) Lakes Salpetn and Quexil, Petn, Guatemala, Central America. In: Kelts K, Gierlowski Kordesch E (eds). Global Geological Record of Lake Basins, Volume 1. Camb University Press. Cambridge, UK, pp 377 380 Brenner M, Rosenmeier MF, Hodell DA, Curtis JH (2002) Paleolimnology of the Maya Lowlands: long term perspectives on interactions among climate, environment, and humans. Anc Mesoam 13: 141 157 Bond G, Kromer B, Beer J, Muscheler R, Evans MN, Showers W, Hoffman S, Lotti Bond R, Hajdas I, Bonani G (2001) Persistent solar influence on North Atlantic climate during the Holocene. Science 294: 2130 2136 Bradbury JP (1997) Sources of glacial moisture in Mesoamerica. Quat Int 43/44: 97 110 Bronk Ramsey C (2006) OxCal 4.0 (Oxford Radiocarbon Accelerator Unit, Oxford, UK) Bush MB, CorreaMetrio A, Hodell DA, Brenner M, Anselmetti FS, Ariztegui D, Mller A D, Curtis JH, Grzesik D, Burton C, Gilli A (200 9) The Last Glacial Maximum in lowland Central America. In: Vimeux F, Sylvestre F, and Khodri M (eds) Past Climate Variability in South America and Surrounding Regions. Springer Verlag, GmbH, pp 380 Covich AP, Stuiver M (1974) Changes in oxygen 18 as a measure of long term fluctuations in tropical lake levels and molluscan populations. Limnol Oceanogr 19: 682 691 Deevey ES (1957) Limnologic studies in Middle America, with a chapter on Aztec limnology. Conn Acad Arts Sci Trans 39: 213 328 Deevey ES (1978) H olocene forests and Maya disturbance near Quexil Lake, Petn, Guatemala. Polskie Arch Hydrobiol 25, No. 1/2: 117 129 Deevey ES, Brenner M, Flannery MS, Yezdani GH (1980) Lakes Yaxha and Sacnab, Petn, Guatemala: Limnology and hydrology. Archaeol Hydrobiol 57: 419 460

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102 Deevey ES, Brenner M, Binford MW( 1983) Paleolimnology of the Petn Lake District, Guatemala III: Late Pleistocene and Gamblian environments of the Maya area. Hydrobiologia 103: 211 216 Delvaux D, Kervyn F, Vittori E, Kajara RSA, Kilembe E (1998) Late Quaternary tectonic activity and lake level change in the Rukwa Rift Basin. J Afr Earth Sci 26, 3: 397 421 Engstrom DR, Swain EB, Kingston JC (1985) A paleolimnological record of human disturbance from Harveys Lake, Vermont: geochemistry, pigments and diatoms. J Freshw Biol 15: 261 288 Flower BP, Hastings DW, Hill HW, Quinn TM (2004) Phasing of deglacial warming and Laurentide Ice Sheet meltwater in the Gulf of Mexico. Geology 32: 597 600 Francus P (2004) Image Analysis, Sediments and Paleoenvironm ents. Vol 7. Kluwer Haug GH, Hughen KA, Peterson LC, Sigman DM, Rhl U (2001). Southward migration of the Intertropical Convergence Zone through the Holocene. Science 293: 1304 1308 Haug GH, Gunther D, Peterson LC, Sigman DM, Hughen KA, Aeschlimann B (200 3) Climate and the collapse of Mayan civilization. Science 299: 1731 1735 Hillesheim MB, Hodell DA, Leyden BW, Brenner M, Curtis JH, Anselmetti F S, Ariztegui D, Buck DG, Guilderson TP, Rosenmeier MF, Schnurrenberger DW (2005) Climate change in lowland Cent ral America during the late deglacial and early Holocene. J Quat Sci 20: 363 376 Hodell DA, Curtis JH, Brenner M (1995) Possible role of climate change in the collapse of the Maya civilization. Nature 375: 391 394 Hodell DA, Brenner M, Curtis JH, Guilderso n T (2001). Solar forcing of drought frequency in the Maya Lowlands. Science 292: 1367 1369 Hodell DA, Brenner M, Curtis JH (2000) in: D. L. Lentz, (ed) Imperfect Balance: Landscape Transformations in the Precolumbian Americas, Columbia Univ Press, New Yor k, pp 13 38 Hodell DA, Brenner M, Curtis JH (2005) Terminal Classic drought in the northern Maya Lowlands inferred from multiple sediment cores in Lake Chichancanab (Mexico). Quat Sci Rev 24: 1413 1427 Hodell DA, Brenner M, Curtis JH, MedinaGonzalez R, R osenmeier MF, Guilderson TP, ChanCan EI, Albornaz Pat A (2005). Climate change on the Yucatan Peninsula during the Little Ice Age. Quat Res 63: 109 121

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103 Hodell DA, Brenner M, Curtis JH (2007) Climate and cultural history of the northeastern Yucatan Penins ula, Quintana Roo, Mexico. Climatic Change. DOI 10.1007/s1058400691774 Hodell DA, Anselmetti F, Ariztegui D, Brenner M, Curtis J, Gilli A, Mller A, Grzesik D, and members of the Peten Itza Scientific Drilling Party (2006) Preliminary Results of the Lak e Peten Itza Scientific Drilling Project, 10th Int Paleolimnol Symp Hughen K, Southon J, Lehman S, Bertrand C, Turnbull J (2006) Marinederived 14C calibration and activity record for the past 50,000 years updated from the Cariaco Basin. Quat Sci Rev 25: 3 216 3227 Johnnson TC, Scholz CA, Talbot MR, Kelts K, Ricketts RD, Ngobi G, Beuning K, Ssemmanda I, McGill JW (1996) Late Pleistocene dessication of Lake Victoria and rapid evolution of Cichlid fishes. Science 273: 1091 1093 Leyden B W (1984) Guatemalan For est Synthesis after Pleistocene Aridity. Proc of the Natl Acad of Sci USA 81: 4856 4859 Leyden BW, Brenner M, Hodell DA, Curtis JH (1993) Orbital and internal forcing of Climate on the Yucatan Peninsula for the past ~36 kyr. Palaeogeogr Palaeoclimatol Palaeoecol 109: 193 210 Lyle M, (1982) The browngreen color transition in marine sediments: A marker of the FE(III) Fe(II) redox boundary. Limnol Oceonogr 28(5): 1026 1033 Mller AD, Anselmetti FS, Ariztegui D, Brenner M, Hodell DA, Curtis JH, Escobar J, Gilli A, Grzesik DA, Guilderson TP, Kutterolf S, Plotze M (2010) Late Quaternary palaeoenvironment of northern Guatemala:evidence from deep drill cores and seismic stratigraphy of Lake Peten Itza. Sedimentology (In press) Nagao S, Nakashima S (1992) The factors controlling vertical color variations of North Atlantic Madeira Abyssal Plain sediments. Geology 109: 83 94. Peterson LC, Haug GH, Hughen KA, Rohl U (2000) Rapid Changes in the HydrologicalCycle of the Tropical Atlantic During the Last Glacial. Science 290: 1947 1951 Rosenmeier MF, Hodell DA, Brenner M, Curtis JH, (2002) A 4000year lacustrine record of environmental change in the southern Maya lowlands, Petn, Guatemala. J Quat Res 57: 183 190 Rosenmeier MF, Hodell DA, Brenner M, Curtis JH, Martin JB, A nselmetti FS, Ariztegui D, Guilderson TP(2002) Influence of vegetation change on watershed hydrology: 18O records. J Paleolim 27: 117 131

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104 Russ JC (1999) The Image Processing Handbook. CRC Press, Boca Raton, Florida, 771 pp Smol JP, GlewJR (1992) Paleolim Encycl Earth Syst Sci Vol 3:551 564 Vasconcelos C, Postec A, Warthmann R, McKenzie JA, Anselmetti F, Ariztegui D, Hodell D (2006) Geomicrobiological Study of Sulfur Nodules Forming in Sediments of Lake Peten Itza, Guatemala, Eos Trans AGU, 87(52) Vinson GL (1962) Upper Cretaceous and Tertiary stratigraphy of Guatemala. Bull of the Amer Assoc of Petrol Geol 46: 425 456 Weaver AJ, Saenko OA, Clark PU, Mitrovica JX(2003) Meltwater Pulse 1A from Antar ctica as a Trigger of the Blling Allerd Warm Interval, Science 299: 1709 Wilson EM (1984). in Moseley ED, Terry ED (eds) Physical geography of the Yucatan Peninsula., Yucatan: A World Apart, second ed., University of Alabama Press, Tuscaloosa, pp 5 40

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105 BIOGRAPHICAL SKETCH Dustin Aaron Grzesik was born in Utica New York in 1980 to Richard and Janice Grzesik. He grew up on the northeastern shore of Oneida Lake, and in third grade wrote a prizewinning editorial addressing his concern with pollution of the lake. As a h igh school j unior, Dustin was a Rotary y outh e xchange student in Coffs Harbour, NSW, Australia. After graduating from High School in June 1998 Dustin enrolled at Paul Smiths College, Paul Smiths NY where he studied e cology and e nvironmental t echnology. After graduating with an Associate of Applied Science (A.A.S.) Dustin participated in a field campaign to collect sediments from Lake Victoria, in Kenya and Uganda with Dr. Curt Stager and three fellow students In September of 2000, Dustin enrolled at Northern Arizona University. While at Northern Arizona University Dr. Lawrence Fritz welcomed Dustin to the Electron Microscopy Facility and he began analysis of the diatoms in sediments recovered from Lake Victoria cores In May of 2002 he graduated with a Bachelor of Science ( B.S. ) degree in z oology. From June 2002 to April 2003, Dustin served as a U.S. Peace Corps Volunteer in Chongqing China, where he was a lecturer of e nvironmental chemistry and e nvironmental e ngineering at Chongqing P olytechnic College. It was in China that Dustin met his wife Joanne Sum Ping. After returning from China, Dustin worked as a Research Technician at the Albert Einstein College of Medicines Analytical Imaging Facility. At the AIF he learned the nuances of confocal microscopy and digital image analysis In August 2005 Dustin enrolled at the University of Florida in the Department of Geological Sciences. Dustin moved to New York, New York, in May of 2007 where hes employed as a geochemist for Malcolm Pirnie Inc. specializing in contaminated sediments and their remediation.