Citation
Climate Change in Central America during the Late Deglacial and Early Holocene Inferred from Lacustrine Sediments in Lake Peten Itza, Guatemala

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Title:
Climate Change in Central America during the Late Deglacial and Early Holocene Inferred from Lacustrine Sediments in Lake Peten Itza, Guatemala
Creator:
HILLESHEIM, MICHAEL B. ( Author, Primary )
Copyright Date:
2008

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Carbonates ( jstor )
Climate change ( jstor )
Climate models ( jstor )
Lakes ( jstor )
Oxygen ( jstor )
Paleoclimatology ( jstor )
Pollen ( jstor )
Precipitation ( jstor )
Sediments ( jstor )
Water depth ( jstor )

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University of Florida
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University of Florida
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Copyright Michael B. Hillesheim. Permission granted to the University of Florida to digitize, archive and distribute this item for non-profit research and educational purposes. Any reuse of this item in excess of fair use or other copyright exemptions requires permission of the copyright holder.
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5/31/2006
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436098757 ( OCLC )

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CLIMATE CHANGE IN CENTRAL AM ERICA DURING THE LATE DEGLACIAL AND EARLY HOLOCENE INFERRED FROM LACUSTRINE SEDIMENTS IN LAKE PETÉN ITZÁ, GUATEMALA By MICHAEL B. HILLESHEIM A THESIS PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLOR IDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE UNIVERSITY OF FLORIDA 2005

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Copyright 2005 by Michael B. Hillesheim

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This thesis is dedicated to my grandmot hers, Mary Hillesheim and Patricia Harris

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iv ACKNOWLEDGMENTS I would like to thank my advisor, Dr. David A. Hodell, for his support of my academic and research goals and for understa nding. I thank Dr. Mark Brenner and Dr. John M. Jaeger for being on my committee and their constructive advice. Dr. Jason H. Curtis deserves special thanks for his expe rtise and lab support. I also thank William Kenney and the Micro-Paleo Lab Assistants for technical help. I thank my fellow graduate students, in particular Sarah Newell, for the fun times. Fi nally, I wish to thank my parents, sister, and Lauren Smith for their love and support.

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v TABLE OF CONTENTS page ACKNOWLEDGMENTS.................................................................................................iv LIST OF TABLES............................................................................................................vii LIST OF FIGURES.........................................................................................................viii ABSTRACT....................................................................................................................... ..x CHAPTER 1 INTRODUCTION........................................................................................................1 Study Site..................................................................................................................... .3 Environmental Setting...........................................................................................3 Climatic Setting.....................................................................................................5 2 METHODS...................................................................................................................7 3 RESULTS...................................................................................................................11 Chronology.................................................................................................................11 Lithology and Geochemistry......................................................................................13 Shallow-Water Cores...........................................................................................13 Deep-Water Cores...............................................................................................14 Pollen......................................................................................................................... .16 4 INTERPRETATION OF PROXY DATA..................................................................19 Oxygen Isotopes.........................................................................................................19 Lithologic and Geoc hemical Indicators......................................................................21 5 DISCUSSION.............................................................................................................23 Paleoclimatic History of Lake Petén Itzá...................................................................23 Comparisons with other Circum-Cari bbean and North Atlantic Records..................27 Proposed Mechanisms for Climate Change in the Preboreal and Early Holocene.....34 6 SUMMARY AND CONCLUSIONS.........................................................................37

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vi APPENDIX A CORE REFERENCE GUIDE....................................................................................39 Deep-Water Cores......................................................................................................41 Core 11A.............................................................................................................42 Core 11B..............................................................................................................43 Core 11F..............................................................................................................44 Shallow-Water Cores..................................................................................................45 Core 11C..............................................................................................................47 Core 11D.............................................................................................................48 Core 11E..............................................................................................................48 B ELEMENTAL GEOCHEMISTRY DATA FOR CORES 11A-11E..........................50 C ISOTOPIC DATA FROM CORE 11A......................................................................75 D SCANNING X-RAY FLUOR ESCENCE PILOT STUDY.......................................79 Introduction.................................................................................................................79 Methods......................................................................................................................80 Results........................................................................................................................ .81 LIST OF REFERENCES...................................................................................................84 BIOGRAPHICAL SKETCH.............................................................................................89

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vii LIST OF TABLES Table page 1-1 Mean ion concentrations of Petén Itzá lakewater.......................................................4 1-2 Oxygen isotopic composition of Petén Itzá lakawater...............................................5 2-1 Length, water depth, and location of cores retrieved along seismic line 11 in Lake Petén Itzá in June 2002......................................................................................7 3-1 Accelerator mass spectrometry (AMS) ra diocarbon dates and calibrated ages of terrestrial organic and aquatic shell mate rial from Lake Petén Itzá Cores 11A, 11B, 11C, 11D, and 11E..........................................................................................12 5-1 Chronology of Preboreal events recorded in Lake Petén Itzá Core 11A compared with reagional and global climate events.................................................................32 A-1 Core reference guide................................................................................................40 A-2 Deep-water core l ithologic description....................................................................42 A-3 Shallow-water core lithologic description................................................................46 B-1 Core 11A elementa l geochemistry data...................................................................51 B-2 Core 11A-MWI elemental geochemistry data.........................................................63 B-3 Core 11B elemental geochemistry data....................................................................64 B-4 Core 11C elemental geochemistry data....................................................................66 B-5 Core 11C-MWI elemental geochemistry data..........................................................70 B-6 Core 11D elementa l geochemistry data...................................................................72 B-7 Core 11E elemental geochemistry data....................................................................73 C-1 Core 11A isotopic data.............................................................................................75 D-1 Log of XRF trial scans.............................................................................................81

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viii LIST OF FIGURES Figure page 1-1 Map of the northern lowla nd Neotropics and study site............................................2 1-2 Water column depth profiles of Petén Itzá lakewater................................................4 2-1 High-resolution seismic image of Line 11.................................................................8 3-1 Images of piston cores taken al ong a depth transect on seismic line 11..................13 3-2 Core 11D sediment variables...................................................................................14 3-3 Core 11A sediment variables...................................................................................16 3-4 Pollen percentage diagrams from Lake Petén Itzá shallow-water Core 11D and deep-water Core 11B................................................................................................17 4-1 Illustration of 18O related to changes in E/P...........................................................20 4-2 Plots of ostracod oxygen isotope ( 18O) measured in Core 11A.............................21 4-3 Scanning electron micrograph (SEM) image of a gypsum grain.............................22 5-1 Hypsographic curve of cumulative lake volume versus water depth.......................23 5-2 Comparison of the first-derivative of the detrended oxygen isotopic signal of ostracods from Petén Itzá Core 11A with density and percent carbonate................25 5-3 Oxygen isotopic records of ostracods from three circum-Caribbean lakes..............28 5-4 Comparison of density measured in Pe tén Itzá Core 11A with percent Titanium from the Cariaco Basin.............................................................................................30 5-5 Comparison of ostracod 18O from Core 11A with records of sea ice extent and solar variability from the hi gh-latitude North Atlantic............................................33 5-6 Comparison of the GISP2 ice core 18O with density measured in Core 11A.........33 A-1 Core 11A image with plots of physical and elemental geochemical properties......43 A-2 Core 11B image with plots of physi cal and elemental geochemical properties.......44

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ix A-3 Core 11F image with plots of physical properties....................................................45 A-4 Core 11C image with plots of physical and elemental geochemical properties.......47 A-5 Core 11D image with plots of physical and elemental geochemical properties......48 A-6 Core 11E image with plots of physical and elemental geochemical properties.......49 C-1 Comparison of bulk and ostracod oxyge n isotopic and carbon isotopic values.......78 D-1 Pictures of the AVAA Tech XRF Core Scanner......................................................79 D-2 Comparison of percent calcium carbona te with calcium measured using the XRF Core Scanner............................................................................................................82 D-3 Comparison of percent clay with titanium measured using the XRF Core Scanner.....................................................................................................................82

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x Abstract of Thesis Presen ted to the Graduate School of the University of Florida in Partial Fulfillment of the Requirements for the Degree of Master of Science CLIMATE CHANGE IN CENTRAL AM ERICA DURING THE LATE DEGLACIAL AND EARLY HOLOCENE INFERRED FROM LACUSTRINE SEDIMENTS IN LAKE PETÉN ITZÁ, GUATEMALA By Michael B. Hillesheim May 2005 Chair: David A. Hodell Major Department: Geological Sciences The transition from arid glacial to moist early Holocene conditions represented a profound change in northern lowland Neotropical climate. Here I report of a detailed record of changes in moisture availability during the latter part of this transition (~11,250 to 7,500 cal yr BP) inferred from sediment co res retrieved in Lake Petén Itzá, northern Guatemala. Pollen assemblages demonstrat e that a mesic forest had been largely established by ~11,250 cal yr BP, but sediment properties indicate th at lake level was more than 35 m below modern stage. From 11,250 to 10,350 cal yr BP, during the Preboreal period, lithologic changes in sedi ments from deep-water cores (>50 m below modern water level) indicate several wet-dry cycles that suggest distinct changes in effective moisture. Four dry events (d esignated PBE1-4) occurred centered at 11,200, 10,900, 10,700, and 10,400 cal yr BP and correlate w ith similar variability observed in the Cariaco Basin titanium record and glacial meltwater pulses into the Gulf of Mexico. After 10,350 cal yr BP, multiple sediment proxies suggest a shift to a more persistently

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xi moist early Holocene climate. Comparison of results from Lake Petén Itzá with other records from the circum-Caribbean demonstr ates a coherent climate response during the entire span of the record. Furthermore, lowland Neotropical climate during the late deglacial and early Holocene period appears to be tightly linked to climate change in the high-latitude North Atlantic. The observed ch anges in lowland Neotropical precipitation were most likely related to the intensity of the annual cycle and associated displacements in the mean latitudinal position of the Intertropical Convergence Zone and AzoresBermuda high-pressure system. This mech anism operated on millennial-to-submillennial timescales and may have responded to change s in solar radiati on, glacial meltwater, North Atlantic sea ice, and the Atlantic meridional overturning circulation (MOC).

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1 CHAPTER 1 INTRODUCTION The northern lowland Neotropics encompasses the area of the New World with elevations <500 m and extends north from the equator to the Tropic of Cancer. It includes areas of southern Mexico, Central America, and northern South America, as well as the West Indies (F igure 1-1A). During the la st deglaciation, this region experienced a pronounced increase in moisture availability. At the onset of deglaciation, all shallow lakes were dry or ephemeral and on ly deep basins contained water. The Petén Lake District of northern Guat emala (Figure 1-1B) is one of the few regions with basins deep enough to have retained water du ring the arid late Pleistocene (Deevey et al ., 1980). Cores recovered from Lakes Quexil (zmax = 32 m) and Salpetén (zmax = 32 m) in 1980 provided some of the first in sights into climatic and ecol ogical change in the lowland Neotropics during the last Ice Age and the transiti on to the Holocene (Deevey et al ., 1983). Pollen and geochemical profiles demons trated an abrupt shift from cool, arid conditions during the last glaciation to wa rmer, moister conditions during the early Holocene (Leyden et al ., 1993, 1994; Brenner, 1994). Because of incomplete recovery, drilling disturbance, and poor dating resoluti on of the 1980 cores, details of the timing, rate and structure of this transition were uncertain. In 1999, a seismic survey (3.5 kHz) of si x Petén lakes was conducted to identify potential targets for coring and drilling (Anselmetti et al ., in review). From the seismic data the first detailed bathymetric map of Lake Petén Itzá was produced (Figure 1-1C). Lake Petén Itzá was of particular inte rest because it is the largest (100 km2) and deepest

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2 (zmax = 160 m) lake in the region. Seismic prof iles revealed a paleoshoreline feature at ~58 m below modern lake level that probabl y represents the lake low-stand during the last glacial period (Anselmetti et al ., in review). Because of the great depth of its northern basin, Lake Petén Itzá likely cont ains one of the few continuous sediment records in Central America of the last glacia tion. Consequently, it is a prime target to obtain long, undisturbed sediment co res for paleoclimate studies. AAtlantic Ocean Caribbean Sea Gulf of Mexico Pacific1 2 4 5 N320oN 70o W 10oN 90o W Tikal Sacnab Yaxha Macanche Quexil Salpetén Peténxil SacpuyLake PeténItzáPetén Lake District N 10 0 km 90o WB C 14A 5A11A 11B11F 8B 8A25-meter contour intervalLake PeténItzá N11C 11D 11E ! 5 0 km 93 Flores 89.90o W 89.45o W 17.00oN 17oN Perdida Figure 1-1. Maps of the north ern lowland Neotropics and study site. (A) Map of the circum-Caribbean and Gulf of Mexico s howing site locations discussed in this study: 1-Petén Lake District, northern Guatemala; 2-Cariaco Basin, offshore northern Venezuela; 3-Lake Valencia, Venezuela; 4-Lake Miragoane, Haiti; 5-Louisiana slope, northern Gulf of Mexico. (B) Map of the Petén Lake District. (C) Bathymetric map of Lake Petén Itzá with the locations of cores collected along seismic line 11 in 2002. Black dots ( ) indicate cores used in this study and the black line ( —— ) is the location of seismic line 11. Cores along other seismic lines in the northern basin are also indicated (5A, 8A, 8B, 14A). 93 refers to the locati on of Core PI 6-VII-93 (Curtis et al ., 1998) taken from Petén Itzá’s southern basin east of the isla nd of Flores.

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3 In June 2002, thirteen Kullenberg-type piston cores were retrieved from 10 sites in Petén Itzá’s northern basin (Figure 1-1C). Undisturbed glacial-age sediment was not recovered because of the thickness of cohe sive late Holocene sediments, known as the Maya Clay, which limited penetr ation of the piston corer to 6 m. The oldest continuous sediment record recovered is dated to 11,250 cal yr BP, and captures only the terminal part of the last deglaciation. This is a report of the pale oclimatic history of the Petén lowlands during the late deglacial and early Holocen e period (~11,250 to 7,500 cal yr BP). Results from this multi-proxy study are compared with other paleoclimate records from sites under the same climate regime, such as the marine Cariaco Basin off Venezuela (Haug et al ., 2001), as well as with the climat e history of the high-latitude North Atlantic recorded in marine sediments and Greenland ice cores (Bond et al ., 2001; Stuiver et al ., 1995). Findings indicate a coherent response of climate throughout the circum-Caribbean region during the late de glaciation and early Holocene with tight linkages to climate changes observed in the high-latitude North Atlantic. Study Site Environmental Setting Lake Petén Itzá is located at ~17.00ºN, 89.50ºW in the Department of Petén, northern Guatemala (Figure 1-1B). The lake is comprised of two connected basins. The deeper, northern basin (Zmax = 160 m) occupies a large half-graben formed by a series of east-west aligned en echelon faults (Vinson, 1962). The northern shore is marked by a steep karst ridge consisti ng of lower Tertiary limestone that follows the strike of the fault system, whereas the southern shore is ge ntly sloping and, in places, rimmed by poorly drained seasonal swamps ( bajos ). The smaller southern basin is much shallower, averaging ~5 m water depth.

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4 Lake Petén Itzá's water is dilute (11.22 meq l-1) and dominated by calcium and bicarbonate, with magnesium and sulfate followi ng closely in concentration (Table 1-1). Table 1-1. Mean ion concentratio ns of Petén Itzá lakewater (n = 24). Ion concentrations were measured on a Dionex Model DX 500 chromatograph. Bicarbonate was calculated as the sum of the cation ch arges minus the sum of chloride and sulfate charges. Ca2+ 3.15 meq l-1 Mg2+ 1.86 meq l-1 Na+ 0.60 meq l-1 Cl0.26 meq l-1 SO4 22.11 meq l-1 HCO3 3.24 meq l-1 Total 11.22 meq l-1 Lakewater pH is high (~8.0) and is satura ted for calcium carbonate, and there are abundant shells of carbonate microfossils pr eserved in the lake sediments (Covich, 1976; Curtis et al ., 1998). Lake Petén Itzá is a term inal basin fed by precipitation, subsurface groundwater inflow, and a small input stream in the southeast. The basin is effectively closed, lacking any surface outlets, alt hough some downward leakage may occur. O2(mg l-1)18O(‰)ABC 0 40 80 120 160 262830Depth in Water Column (m)Temperature (oC) 0369 2.62.83 Figure 1-2. Water column depth profiles of Peté n Itzá lakewater. (A) Temperature (ºC), (B) dissolved oxygen content (mg l-1), and (C) oxygen isotopic composition ( 18Olw, ‰; VSMOW) of Petén Itzá lakewate r. The temperature profile and samples for 18O analysis were collected on 13 August 2002 at 17.00ºN, 89.85ºW. Dissolved oxygen is plotted for May (solid line) and August (dashed line) 1980 (unpublished data).

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5 Thermal stratification is pers istent year round with hypolimne tic temperatures averaging ~25.4ºC, close to the mean annual air temper ature (Figure 1-2A). Hypolimnetic oxygen depletion has been observed near the deepest point in the lake (Figure 1-2B). The oxygen isotopic composition of lakewater is enrich ed in surface waters (Figure 1-2C) and averages 2.9‰, which is enriched by ~7‰ rela tive to regional precipitation (Table 1-2), indicating that evaporation is an importa nt part of the lake’s water budget. Table 1-2. Oxygen isotopic composition ( 18Olw)VSMOW of Petén Itzá lakewater at various depths in the water column. Mean oxygen isotopic composition ( 18Olw)VSMOW of Petén Itzá lakewater based on 34 samples collected at various sites and water depths in June and August 2002. Oxygen isotopic composition of precipitation ( 18Op) interpolated from circum-Caribbean stations in the GNIP database (IAEA, 2001). 18Olw was measured on a VG Prism II mass spectrometer using a modified method from Socki et al . (1992). Depth in Water Column (m) 18Olw (‰) VSMOW 0 3.01 10 3.02 20 2.95 30 2.94 40 2.79 60 2.84 90 2.81 120 2.72 150 2.67 18Olw +2.9‰ (VSMOW) 18Op 4.0‰ (VSMOW) Climatic Setting Petén’s climate is marked by uniformly high temperatures (averaging 25ºC), with variability most notably expressed as tem poral and spatial changes in rainfall. Precipitation in Petén varies from 900 to 2500 mm yr-1, with a regional mean of ~1600

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6 mm yr-1 (Deevey et al ., 1980). Lake Petén Itzá is situat ed in a climatically sensitive region where the amount of rainfall is re lated to the seasona l migration of the Intertropical Convergence Zone (ITCZ) a nd Azores-Bermuda high-pressure system (Hastenrath, 1984). Approximately 90% of the precipitation falls during the summer months (June to October) dr iven by increased convection as sociated with the northward migration of the ITCZ. The rainy season is of ten interrupted by a slight rainfall decrease in July and August, which is known as th e canicula or "lit tle dry" (Magaña et al ., 1999). The rainy season usually ends by late Oc tober and is followed by a pronounced dry season during the winter (January to May) as the ITCZ moves equatorward (i.e. southward), allowing the Azores-Bermuda hi gh to dominate the Gulf of Mexico and Caribbean Sea region. The region is also ma rked by subsidence during winter related to the descending limb of the Hadley Ce ll, centered at ~20ºN (Waliser et al ., 1999). Lake Petén Itzá's volume is sensitive to precipitation changes and has fluctuated markedly in the recent past. For example, mean annual rainfall during the period from 1934 to 1942 was relatively high (2055 mm yr-1) and resulted in incr eased lake levels and flooding (Deevey et al ., 1980). In contrast, the early to mid-1970s were relatively dry (mean annual rainfall = 1415 mm yr-1) resulting in lower lake levels. During the late 1970s lake level rose again in response to increased precipita tion continuing until the early 1990s at which time the trend reversed. Petén Itzá's level va ries seasonally, by as much as 80 cm, displaying a rise after the summer rainy season and a fall during the dry season with a 1-2 month lag (Deevey et al ., 1980). On seasonal to decadal time scales, lake volume and water chemistry are sensit ive to changes in the balance between precipitation and evaporation.

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7 CHAPTER 2 METHODS In June 2002, six piston cores (Table 2-1) were retrieved along a depth transect on seismic line 11 in water depths ranging fr om 9.7 to 63.2 m (Figure 2-1). Cores were recovered using a Kullenberg-type piston corer triggered by a mud-water interface (MUCK) corer. In the laboratory, each co re section was measured in its original polycarbonate liner for magnetic susceptibi lity and gamma-ray attenuation (GRA) bulk density at 0.5-cm increments using a GEOT EK Multi-Sensor Core Logger (MSCL). The instrument was calibrated at the start of each day using an aluminum standard. After logging, cores were split and imaged with a GEOTEK digital color line-scan camera that was calibrated each day using a white ceramic calibration tile. Table 2-1. Length, water depth, and location of cores retrieved along seismic line 11 in Lake Petén Itzá in June 2002. Cores ar e labeled by abbreviated lake name, day-month-year, and site. Core Length (cm) Depth (m) Latitude Longitude PI 8-VI-02 11A 558 58.2 17.000ºN89.779ºW PI 5-VI-02 11B 515 51.6 16.998ºN89.779ºW PI 9-VI-02 11C 275 30.0 16.991ºN89.780ºW PI 6-VI-02 11D 210 20.9 16.988ºN89.779ºW PI 8-VI-02 11E 255 9.7 16.984ºN89.779ºW PI 9-VI-02 11F 585 63.2 17.004ºN89.780ºW The six cores retrieved along Depth Transe ct 11 can be grouped into deep-water (>50 m modern water depth) and shallow-wate r (<35 m modern water depth). The three deep-water cores are PI 8-V I-02 11A, PI 5-VI-02 11B and PI 9-VI-02 11F (Table 2-1), hereafter, referred to as Cores 11A, 11B and 11F. Core 11A was selected as the representative of the deep-w ater sediment stratigraphy because it contained abundant

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8 terrestrial organic material for radiocarbon da ting. Core 11B was sampled for pollen and placed on the same sediment depth scale as Co re 11A by correlating variations in color (rgb) intensity (correlation coefficient, r =0.84) using Analyseries 1.1 (Paillard et al ., 1996). Core 11F was excluded because it does not span the whole lithologic sequence observed in Cores 11A and 11B (Appendix A). The three shallow-water cores are PI 9VI-02 11C, PI 6-VI-02 11D, and PI 8-VI-02 11E (Table 2-1), hereafter referred to as Cores 11C, 11D, and 11E. Core 11D was select ed as representative of the sediment stratigraphy in shallow-water co res because it contained the mo st generalized lithology of the three shallow-water cores (Appendix A). Figure 2-1. High-resolution seismic image of Line 11 showing the location of piston Cores 11A-11F (see also Table 2). No te the Late Glacial/Holocene (LG/H) sequence boundary (bold dashed-solid lin e) and the paleoshoreline feature at ~58 m paleo water depth (adapted from Anselmetti et al ., in review). The primary focus of this study is on d eep-water Core 11A (water depth = 58.2 m) and shallow-water Core 11D (water depth = 20.9 m). The working halves of Cores 11A and 11D were sampled at 1-cm and 5-cm intervals, respectively. Small subsamples (~5

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9 cc) were taken for elemental analysis, oven dried, and ground to a fine powder with a mortar and pestle. The remainder of the sample was wet sieved at 63m to isolate microfossils and terrestrial organic mate rial for isotopic and radiocarbon analysis. Radiocarbon ages were determined at the Center for Accelerator Mass Spectrometry (CAMS) at Lawrence Livermor e National Laboratory. Eighteen samples of terrestrial organic matter (wood, leaf, or charcoal) and eight samples of aquatic gastropod ( Pyrgophorus sp.) shell were dated. Samples of shell material were used to date intervals where terrestrial organic matter was scarce. Samples of terrestrial organic matter used for radiocarbon dating were pretreated at the Univ ersity of Flor ida using the acid-base-acid pretreatment method. Radiocarbon ages were determined after blank subtraction as determined on sim ilarly pretreated and processed 14C-free wood. Organic matter samples were also analyzed for 13C content and corrected to –25‰ prior to calibration. Five samples from Core 11A were too small for 13C analysis and were assumed to have values of –25‰. Calibrated ag es, in calendar years before 1950 (cal yr BP), were calculated using INTCAL98, with a 100-yr moving average of the tree ring calibration data set (Stuiver and Reimer, 1993; Stuiver et al ., 1998). Inorganic carbon (IC) was determined by coulometric titration using a UIC/Coulometrics 5011 coulometer c oupled with a UIC 5240-TIC carbonate autosampler. Weight per cent calcium carbonate (CaCO3, %) was calculated by multiplying IC by 8.33. Total weight per cent carbon (TC) and sulfur (S, %) were measured using a Carlo Erba NA 1500 CNS el emental analyzer with autosampler. Weight percent organic carbon (OC) was estimat ed by subtracting IC from TC. Weight percent organic matter (OM, %) was estimated by multiplying OC by 2.2.

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10 Oxygen isotope ratios in Core 11A were measured on adult carapaces of the ostracod Limnocythere sp., which were isolated from the >250 m sediment fraction. Ostracod valves were abundant from 558 to 500 cm, but gradually decreased above this level until they became absent at 491 cm . Ostracods were cleaned with 15% H2O2 to remove organic matter, and then washed with de-ionized water, rinsed in methanol, and dried. Ostracod aggregates of 15-20 valves were measured from each 1-cm sample. The samples were reacted in 100% orthophosphor ic acid at 70ºC using a ThermoFinnigan Kiel III automated preparation syst em. Isotopic ratios of purified CO2 gas were measured online with a ThermoFinnigan 252 mass spectrome ter. Isotopic values are reported in delta ( ) notation as the per mil (‰) deviati on from Vienna PeeDee Belemnite (VPDB). 18OVPDB (‰) = ([(18O/16O)sample / (18O/16O)reference] –1) *1000 Analytical precision was estimated by measur ing eight samples of a powdered carbonate standard (NBS-19) with each sample run. Precision for 18O was estimated to be ±0.10‰ (1 ; n = 24 standards). Samples for pollen analysis were processed using 1-cm3 of sediment taken from Core 11B at 1-cm to 10-cm intervals and Core 11D at 5-cm intervals. One Lycopodium tablet (batch 124961; mean = 12,542; std. dev. = 931) was added to each sample to calculate pollen concentration. Samples we re processed using a standard sequence of HCL, KOH, HF, and acetolysis. The resi due was stained with Basic Fuchsin and suspended in tertiary butyl alcohol (TBA), and measured aliquots of the suspension were mounted in silicone oil on mi croscope slides. Pollen fr om Cores 11B and 11D were counted at 400x magnification to a mi nimum sum of 200, excluding pteridophytes, aquatic algae and macrophytes, and unident ifiable grains (B. Leyden, pers. comm.).

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11 CHAPTER 3 RESULTS Chronology All thirteen radiocarbon samples from Co re 11A yielded dates in stratigraphic order (Table 3-1). An age-depth model was derived by linear interpolation between dated horizons (Figure 3-1, inset). We estimated the basal age of Core 11A to be ~11,250 cal yr BP by extrapolating the sedimentation rate 6 cm beyond the lowermost radiocarbon date at 558 cm. Linear sedimentation rate s (Figure 3-1, inset) average ~0.025 cm yr-1 from the base of the core at 558 cm to 335 cm (11,250 to 3,000 cal yr BP). Between 335 and 57 cm (3,000 to ~1,400 cal yr BP), sedimentation rates increase to ~0.2 cm yr-1 concomitant with the onset of deposition of th e Maya Clay. The temporal resolution is ~40 yrs for each 1-cm sample during the late deglacial and early Holocene (558 to 463 cm or 11,250 to 7,500 cal yr BP). Charcoal near the top of a so il horizon found in the shallow-water cores (Table 3-1; Figure 3-1) wa s dated to constrain the onset of lacustrine deposition associated with lake filling. Ages ranged from 11,120 ± 60 cal yr BP in Core 11C (31.8 m water depth) to 10,220 ± 70 cal yr BP in Core 11E (9.7 m water depth). Shell material from the soil horizon was also dated to assess the magnitude of hard-waterlake error (Deevey and Stuiver, 1964). Th e difference in the paired ages varied dramatically (Table 3-1), ranging from 5,300 to 1,700 cal yrs. Because of this, all ages are reported as measured values and no hard -water-lake error correction was applied. Three shell samples from the base of each sh allow-water core were also dated, yielding ages between 20,540 and 37,650 cal yr BP (Table 3-1; Figure 3-1).

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12 Table 3-1. Accelerator mass spectrometry (A MS) radiocarbon dates and calibrated ages of terrestrial organic and aquatic shel l material from Lake Petén Itzá Cores 11A, 11B, 11C, 11D, and 11E. All Radiocarbon ages were corrected to 13C values of –25‰, except leaf and wood samples (indicated with #), that were too small for 13C analysis and are assumed to be –25‰. Core Sample Type Depth (cm) CAMS No. 13C (‰) Radiocarbon Age (1 , 14C yr BP) Calibrated Age (2 , cal yr BP) PI 8-VI-02 Leaf 75.5 99102 -23.31 1660 ± 40 1570 ± 60 11A Wood 190.5 99103 # 2095 ± 35 2070 ± 80 Wood 247.5 101228 # 2530 ± 60 2600 ± 150 Wood 297.5 99104 -22.27 2570 ± 45 2740 ± 35 Wood 353.5 92837 -30.30 3240 ± 30 3435 ± 55 Wood 369.5 99105 -31.68 3525 ± 25 3795 ± 75 Wood 446.5 101229 -23.63 6160 ± 70 7065 ± 180 Leaf 448.0 101230 # 6155 ± 50 7025 ± 135 Wood 463.5 99106 # 6585 ± 35 7470 ± 40 Wood 489.5 92836 -30.80 7925 ± 30 8720 ± 90 Wood 504.5 101231 -28.67 8425 ± 30 9475 ± 55 Wood 547.0 101232 # 9470 ± 110 10820 ± 340 Wood 552.0 101233 -22.70 9555 ± 30 11015 ± 75 PI 5-VI-02 Shell 280.0 94597 -2.69 3970 ± 40 4440 ± 90a 11B Charcoal 365.0 94606 -27.12 5930 ± 40 6730 ± 70 Wood 433.0 92835 -28.30 7330 ± 40 8105 ± 85 PI 9-VI-02 Charcoal 140.0 94607 -15.67 9665 ± 45 11120 ± 60 11C Shell 140.0 94598 0.47 13810 ± 45 16580 ± 480a Shell 270.0 94599 -0.56 32420 ± 290 37635 ± 315a,b PI 6-VI-02 Charcoal 75.0 94608 -17.92 9460 ± 45 10670 ± 110 11D Shell 75.0 94600 -1.50 11025 ± 40 13020 ± 150a Shell 140.0 94601 -1.85 19320 ± 70 22950 ± 730a Shell 205.0 94602 1.59 22110 ± 90 26035 ± 105a,b PI 8-VI-02 Charcoal 165.0 94609 -12.71 9055 ± 50 10220 ± 70 11E Shell 165.0 94603 -3.68 10280 ± 40 12070 ± 310a Shell 250.0 94604 -3.50 17250 ± 60 20540 ± 650a PI 6-VI-02 Wood 162.0 99107 -26.19 8185 ± 50 9150 ± 140 11E Wood 163.0 99108 -26.19 8240 ± 45 9210 ± 120 Wood 205.0 99109 -28.16 8740 ± 60 9735 ± 185 a Ages are potentially susceptible to hard -water-lake error (Deevey and Stuiver, 1964) b Radiocarbon ages were too old for INTCAL98; therefore, ages were calibrated using the following equation from Bard et al . (1998): Age (cal yr BP) = -3.0126 x 10-6 (14C age BP)2 + 1.2896 (14C age BP) 1005

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13 0 100 200 300 400 500 600 020004000600080001000012000Depth in Core 11A (cm)Calibrated Age (cal yr BP)Avg. Sed. Rate = ~0.2 cm yr-1Avg. Sed. Rate = ~0.025 cm yr-1Lake PeténItzáCore11A Change in Sedimentation Rate at ~3,000 cal yr BP LG/H Transition Figure 3-1. Images of piston co res taken along a depth transect on seismic line 11. Water depths are relative to modern (2001) la ke level. Dated horizons are indicated by arrows and inter-core correlations ar e marked by solid lines. The LG/H boundary (bold line) is marked by dark paleosols in shallow-water Cores 11C, 11D, and 11E and gypsum precipitation in deeper-water Cores 11A and 11B. Inset Calibrated age versus depth fo r Lake Petén Itzá Core 11A. Core chronology was established by linear inter polation between thirteen calibrated radiocarbon dates measured on terrestrial wood and leaf samples. Average sedimentation rates vary between ~0.2 and ~0.025 cm yr-1, with a transition in sedimentation rate occurring at ~ 3,000 cal yr BP. Dating error (2 ) on all samples is smaller than the plot symbols, except where indicated by error bar. Lithology and Geochemistry Shallow-Water Cores Sediment properties of Core 11D (Figure 3-2) represent the general pattern of lithologic and geochemical changes observed in the three shallow-water cores (<35 m water depth). Pleistocene age sediments c onsist of dense, carbonate-rich silty-clays

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14 overlain by a paleosol that is marked by incr eased magnetic susceptibility (Figure 3-2D), the presence of terrestrial gastropods and plant roots, and the absence of aquatic microfossils. The transition to lacust rine deposition, dated between 11,100 and 10,200 cal yr BP (Figure 3-1), is marked by decr eases in density and ma gnetic susceptibility concurrent with increases in percent carbonate and organic matter content (Figure 3-2), as well as the reappearance of lacust rine gastropods and ostracods. 2468OM (%) 50 100 150 200 607080Depth in Core (cm)CaCO3(%) 1.21.51.8Density (g cc-1 ) 051015Mag.Susc. (cgs) 50100150 50 100 150 200Red Intensity ( nm ) 10,670 ±110 cal yr BPLake Petén ItzáCore 11DPaleosol ABCDE Figure 3-2. Sediment variables measured in Lake Petén Itzá Core 11D. (A) Weight percent calcium carbonate (CaCO3, %), (B) weight percent organic matter (OM, %), (C) GRA bulk density (g cc-1), (D) magnetic susceptibility (cgs), (E) red color intensity (nm). The dashed line (---) denotes the dated lithologic transition from paleosol to lacustrine deposition. The approximate thickness of the paleosol is highlighted in gray. Deep-Water Cores The bottom 25 cm (~11,250 to 10,350 cal yr BP) in both deep-water cores (11A, 11B) is composed of dense gypsum sands interb edded with silty clays. These lithologic changes are reflected in the calcium carbonate (CaCO3), organic matter (OM), and sulfur (S) records (%, Figure 3-3A-C). Gypsum-ri ch intervals are indicated by high sulfur content centered at ~10,400, 10,700, 10,900, and 11,200 cal yr BP. The intervening siltyclay layers contain higher pe rcentages of carbonate and or ganic matter and are centered

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15 at ~10,500, 10,800, and 11,000 cal yr BP. At 10,350 cal yr BP, gypsum precipitation ceased and sediments became dominated by calcium carbonate and organic matter. Between 10,350 and 7,500 cal yr BP, %CaCO3 decreased from 60 to 10% and %OM increased slightly, averaging 14%, with the remainder of the sediment being composed mostly of inorganic clay. Superimposed upon these long-term trends are small, shortterm variations. At 9,700 cal yr BP, %CaCO3 decreased by 25% and %OM increased by ~10%. From 9,700 to 8,800 cal yr BP, %CaCO3 and %OM remained relatively constant averaging 25 and 14%, respectiv ely. At 8,800 cal yr BP, %CaCO3 began to decrease more rapidly coincident with a distinct incr ease in %OM. This trend is interrupted at 8,100 cal yr BP by a ~10% decrease in organic matter and a ~5% increase in carbonate, relative to the bulk sediment, that persiste d until 7,800 cal yr BP when both proxies returned to pre-excursion values. GRA bulk density follows lithologic ch anges between 11,250 and 10,350 cal yr BP. High density is associated with gypsum beds and low density with clay-rich layers (Figure 3-3D). At 10,350 cal yr BP, de nsity decreased abruptly followed by progressively lower values until the end of th e record at 7,500 cal yr BP. This trend was interrupted, however, by a small (0.1 g cc-1), short-lived (~100 yr) increase centered at 9,400 cal yr BP and a larger (0.2 g cc-1), longer-lived (~300 yr) increase centered at ~8,000 cal yr BP. Ostracods from the base of Co re 11A record the greatest 18O values averaging 4.5‰ (Figure 3-3E). Between ~11,250 and 10,400 cal yr BP, 18O generally decreased by ~1.3‰. Superimposed upon this trend are two distinct 18O minima centered at 11,000 and 10,500 cal yr BP. At 10,400 cal yr BP, 18O values increased slightly and

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16 then gradually decreased until ~9,600 cal yr BP , at which point values begin to increase again. At 9,300 cal yr BP, this trend reversed and 18O reached its lowest values of ~3.1‰ at 8,800 cal yr BP. Ostracods are absent in the sediment profile after this time. 204060 7500 8000 8500 9000 9500 10000 10500 11000CaCO3 ( % ) Age (cal yr BP)1020OM ( % ) 1.61.8Densit y (g cc-1 ) 4.5 4 3.5 3 7500 8000 8500 9000 9500 10000 10500 1100018O ( ‰ ) Age (cal yr BP)AC BDE1.4 15 5 0Lake Petén ItzáCore 11A PB/H transition wetter drier 4812Sulfur (%) Figure 3-3. Sediment variables measured in Lake Petén Itzá Core 11A. (A) Weight percent calcium carbonate (CaCO3, %), (B) weight percent organic matter (OM, %), (C) weight per cent sulfur (S, %), (D) GRA bulk density (g cc-1), (E) oxygen isotopic composition ( 18O, ‰) of ostracods. Distinct changes in sediment composition are highlighted in gray. Pollen Pollen is poorly preserved prior to ~11,500 cal yr BP (86 cm) in Core 11D (Fig. 7A). Within the soil horizon (75 to 115 cm), Pinus (pine) predominates together with Quercus (oak), Asteraceae (composites), and Poaceae (grasses), but pollen concentrations are low. A small increase in aquatic taxa o ccurs as lacustrine de position begins at 10,670 cal yr BP (75 cm). After which Brosimum -type becomes a dominant taxon, along with Gymnanthes , pine, oak, Bursera , and grasses (B. Leyden, pers. comm.).

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17 5250 5750 6250 6750 7250 7750 8250 8750 9250 9750 10250 10750 11250Age (cal yr BP)20406080B r o si m u m20Pin u s20Quercus20Gymn a nthe s B u r sera U lmus G y m n o po d ium L i q u i d a mbar M yrt a ce a e Are c ac ea e A lnu s Cro t on-type Trema20A ca l ypha C e lt is 3p Moraceae Mela s tome/Combretac. S p o ndias Protea c eae C o r di a C e cr o p i a Al c horn e a B y rs o n i m a20U r ti ca ce a e A s t era c ea e20P oace a e Cyperaceae T y p h a2040B o t ryoco c cus20 40C h a rcoalLake Petén ItzáCore 11B Pollen Percentage Diagram 60 65 70 75 80 85Depth (cm)20B r o si m u m204060P i n u s20Qu e rcus G y m n an t h e s Burse ra U lmus Gymn o podium Liqui d a m b a r M y r ic a C ro t o n -ty p e Sp o n d i a s T r e ma A l n u s Acalyp h a C e l ti s By rs o n ima Urt i caceae Ma lv a ce ae P l a n ta g o C h e n o p o d -Am a ra n th .20Asteraceae20P o a c ea e Cyperaceae T y p h a N ymphac e ae CharcoalLake Petén ItzáCore 11D Pollen Percentage Diagram10,670 cal yr BPA B Figure 3-4. Pollen percentage diagrams from Lake Petén Itzá (A) shallow-water Core 11D and (B) deep-water Core 11B. For both cores, certain taxa (i.e. ferns, algae, aquatic vegetation, and unidentif iable pollen) were excluded from the pollen sum used to calculate percentages. Aquatic taxa were excluded so that the pollen sum reflects only terrestrial taxa and Brosimum-type was excluded from the pollen sum of Core 11B, in orde r to enhance the changes in the other taxa. Stippled curves in Core 11D repr esent a factor of five exaggeration of the original pollen percentages (present ed with permission from B. Leyden). The pollen percentage profile for Core 11B (Fig. 7B) can be divided into three zones that correlate with the sedimentologi cal and isotopic record s, but typically lag behind them by ~100 yrs based on the high-re solution sampling of pollen (i.e. 1-cm intervals) over the late deglacial-to-early Holocene transition. Total pollen accumulation rates in Core 11B were low prior to 10,250 cal yr BP, less than one-third of the values calculated for later deposits. Subsequent accumulation rates follow the percentage trends. Brosimum -type predominates in the basal zone from 11,250 to 10,250 cal yr BP

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18 together with Bursera , Ulmus , Gymnanthes , pine, and oak. Percentages for Liquidambar (sweet gum), Typha (cattail) and Asteraceae are notable. From 10,250 to 8,250 cal yr BP Brosimum -type, other Moraceae, Celtis, and Melastomataceae/ Combretaceae increase while Liquidambar, oak, and to a lesser extent, Gymnanthes decline. The aquatic alga Botryococcus increases sharply by 8,800 cal yr BP. After 8,300 cal yr BP Brosimum type and Gymnanthes decrease and secondary forest taxa such as Bursera and Cecropia increase, followed later by increases in Byrsonima , grasses, and charcoal (B. Leyden, pers. comm.).

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19 CHAPTER 4 INTERPRETATION OF PROXY DATA Oxygen Isotopes The oxygen isotopic ( 18O) composition of shell carbonate is influenced by temperature, 18O of lake water, and vital effect s (i.e. taxon-specific fractionation) (Covich and Stuiver, 1974). Vital effects were minimized by measuring a single species of adult ostracod ( Limnocythere sp.) from the >250 m sediment fraction. Temperature change in the region during the Preboreal and early Holocene was probably small given the minor change in pollen assemblage relative to the last glacial, as well as the lack of cool indicator species such as Juniperus and Liquidambar . It is therefore suggested that ostracod 18O was controlled principally by changes in the 18O of lake water, which is related to the ratio of evaporat ion to precipitation (E/P) and the 18O of precipitation (Figure 4-1; Fontes and Gonfiantini, 1967; Gasse et al ., 1990). Between 11,500 and 8,700 cal yr BP, the 18O of western Caribbean seawater decreased by ~0.4‰ (Schmidt et al ., 2004), which should have decreased the 18O of precipitation by the same amount because the Caribbean is the primary source of water vapor to the Yucatan Peninsula. The 18O of precipitation in the lowland tropics is also dependent on the amount of rainfall, with lower 18O values associated with greater precipitation (Ro zanski et al., 1993). Both the “amount effect” and ch anges in E/P influence lakewater 18O in the same direction such that increa sed precipitation results in lower 18O values of both rainfall and lake water.

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20 Holocene Conditions Late Pleistocene Conditions low 18O high 18O Figure 4-1. Cartoon illustrating the di fferences between high and low 18O values and how they are related to ch anges in E/P (from Hodell et al ., 2001). Consequently, variations in Lake Petén Itzá ostracod 18O most likely represent relative changes in the ratio of preci pitation to evapora tion. Times of changing E/P are represented by changes in the slope of 18O and periods of unchanging 18O represent times of fairly constant E/P. Therefore, by comparing the first de rivative (i.e. changing slope) of the 18O signal (Figure 4-2) w ith other proxy records a clearer picture of the timing and rate of change is achieved.

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21 9000 9500 10000 10500 11000 345Age (cal yr BP)18O (‰) -10118Oresidual(‰) 9000 9500 10000 10500 11000 -0.0100.01Age (cal yr BP)d( 18O)/dt (‰) A BC Figure 4-2. Plots of os tracod oxygen isotope ( 18O) measured in Core 11A. (A) Threepoint running average of 18O (bold line) with a second-order polynomial curve fit (dashed line), (B) 18O residual of curve fit minus the raw 18O data, and (C) first-derivative with respect to time of the 18O residual. Lithologic and Geochemical Indicators Changes in precipitation affect delivery rates of detrital material to the lake basin. Changing rainfall also alters the concentrati on of dissolved salts by enriching or diluting ions in lake water. Sediment lithology and chemical composition are used to infer past changes in detrital input and lake water chemistr y that are, in turn, controlled by climate. For example, greater gypsum content in sedime nts and associated increases in sediment density reflect lake volume reduction and hi gher lakewater salinity during dry periods,

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22 similar to the interpretation of the record from Lake Chichancanab, northern Yucatan Peninsula (Hodell et al ., 1995, 2001, in press). Scanning el ectron micrographs (SEMs) of gypsum grains from Lake Petén Itzá show th ey are euhedral and show no evidence of rounding or abrasion that woul d indicate transport or rede position (Figure 4-3). The gypsum formed authigenically, perhaps in the littoral zone where the evaporation rate was higher than that of deeper, open water. Figure 4-3. Scanning electron micrograph (SEM) image of a gypsum grain taken from the base of Core 11A.

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23 CHAPTER 5 DISCUSSION Paleoclimatic History of Lake Petén Itzá Seismic profiles suggest that lake leve l was ~58 m below modern prior to 11,250 cal yr BP (Figure 2-1; Anselmetti et al ., in review), which required an ~87% (4.8 km3) reduction in volume relative to today (Figure 5-1). Sha llow-water cores (<35 m below modern lake level) contain a paleosol indi cating subaerial exposure. Cores from nearby, shallower Lakes Quexil and Salpetén also indicated lake level lowering of at least 30-40 m during the last glacial period (Deevey et al ., 1983), which likely caused them to become ephemeral. Glacial-age vegetation c onsisted of sparse temp erate thorn scrub and taxa such as Juniperus indicating much cooler temperat ures. One estimate suggests that temperatures were ~6.5 to 8º C lower than today (Leyden et al ., 1993, 1994). 0 20 40 60 80 100 120 140 160 020406080100Lake Depth (m)Cumulative Volume (%)late glacial (>11,250 cal yr BP) Modern 10,200 cal yr BP 11,100 cal yr BP Figure 5-1. Hypsographic curve of cumulative lake volume versus wa ter depth. Arrows indicate inferred lake levels based on flood surface ages.

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24 During the last deglaciation, Petén climate wa s marked by an abrupt shift from arid to humid conditions, as inferred from multiple sediment proxies (Leyden et al ., 1993, 1994; Brenner, 1994). Pollen assemblages in shallow-water Core 11D (Figure 3-4A) changed from Pinus to Brosimum -type dominance concomitant with the rise of other mesic taxa. This increase in mesic taxa corr elates with a similar change in the pollen profile from nearby Lake Quexil that o ccurred after ~12,600 cal yr BP (Leyden et al ., 1993, 1994). Deep-water cores from Lake Petén It zá do not capture the entire deglacial sequence. Instead, they begin during the latter part of deglaciation, at ~11,250 cal yr BP. Predominance of Brosimum at the base of Core 11B indicat es a mesic tropical forest had largely been established in Petén by this time (Figure 3-4B). This is in agreement with 18O and pollen records from Lake Quexil that indicate warmer a nd wetter conditions following the glacial period (Leyden et al ., 1993, 1994). Dated paleosols in shallowwater Petén Itzá cores, however, indicate lake level was at least 35 m lower than today (Figure 3-1). This conclusion is supported by the presence of Typha pollen in deep-water cores (>50 m) that indicates a nearby littora l zone with emergent vegetation (Figure 34B). From 11,250 to 10,350 cal yr BP, during the Preboreal period, the 18O of Lake Petén Itzá ostracods in Core 11A decreased, i ndicating greater effective moisture (Figure 3-3E). The lithologic change in shallow-wa ter cores (<35 m water depth), from subaerial exposure (paleosol) to subaque ous deposition (lacustrine sedi ments), marks a lake level rise at this time (Figures 3-1 and 3-2). In deep-water Core 11A, variations in oxygen isotopes, density, and sediment composition (Figure 3-3) show a number of abrupt

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25 changes that suggest varying e ffective moisture and lake leve l instability. These changes represent a series of wet-dr y cycles of ~250 yr duration. During the Preboreal, four distinct dry events (desi gnated PBE1-4) are identified by lithologic changes (i.e., increased gypsum content) centered at 11,200, 10,900, 10,700, and 10,400 cal yr BP (Figure 5-2). Changes in 18O, as expressed by the first derivative of the signal, are consistent with the lithologic changes, typica lly leading them by ~50 yrs (Figure 5-2). 9500 10000 10500 11000Age (cal yr BP)d( 18O)/dt Wet DryWet Dry -0.01 0 0.01 1.41.61.8Density (g cc-1) -0.0100.01 204060CaCO3(%) d( 18O)/dt PBE1 PBE2 PBE3 PBE4AB Figure 5-2. Comparison of the first-deriva tive of the detrended oxygen isotopic signal d( 18O)/dt of ostracods from Petén Itzá Co re 11A (bold line) with (A) density (g cc-1) and (B) percen t carbonate (CaCO3, %). PBE1-4 designate dry events listed in Table 4 and are highlighted in gray. Low temporal sampling resolution (~50-200 yrs) for pollen over this interval precludes detailed in terpretation of vegeta tion changes during this period. Average climate conditions at the beginni ng of the Preboreal were somewh at cooler and drier. But after ~10,700 cal yr BP, pine, oak, Liquidambar , and Gymnanthes begin to decline while Acalypha, Trema, and charcoal increase (Figure 3-4B). Liquidambar reflects cooler

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26 conditions and Gymnanthes prefers drier, open conditions. Acalypha and Trema are common tropical secondary or successi onal taxa. Although percentages for Brosimum don’t increase, the accumulation rate is slightly higher. During this interval, pollen changes suggest moister, and perhaps warmer, climatic conditions, in general agreement with other proxy indicators (B . Leyden, pers. comm.). An important change in La ke Petén Itzá’s hydrology occurred at ~10,350 cal yr BP, coinciding with the Prebor eal/Boreal boundary observed in northern European pollen records. At this time, an increase in effec tive moisture is inferred from sharp decreases in density and sulfur content that indicate ce ssation of gypsum precip itation (Figure 3-3C,D) concomitant with increases in carbonate and organic matter content (Figure 3-3A,B). A small increase in the abundance of Brosimum -type pollen lags this transition by ~100 yrs (Figure 3-4B). This represents the time at which Lake Petén Itzá’s water chemistry fell below gypsum saturation and sediment li thology and density became less variable. After 10,350 cal yr BP, reduced variability of sediment composition and ostracod 18O values indicate a more persistent mois t climate (Figure 5-2). This is further supported by the resumption of lacustrine de position at sites sha llower than 8 m water depth (Figure 3-1; Curtis et al ., 1998) indicating lake stage had risen to near present levels by 10,200 cal yr BP (Figure 5-1). Cent ered at 9,400 cal yr BP, small increases in density and 18O may suggest a brief (~100 yr) return to slightly drier conditions (Figure 5-2). At 8,800 cal yr BP, the abundance of aquatic algae ( Botryococcus ) increases (Figure 3-4B) concomitant with an increase in organic matter content (Figure 3-3B). This also marks the time when ostracods in deep-water cores di sappear, indicating the onset of hypolimnetic anoxia, which may also account for better preservation of organic

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27 matter. Between 8,100 and 7,800 cal yr BP, ch anges in sediment composition suggest a temporary return to drier conditions (Fi gure 3-3A-D), after which humid climate conditions prevailed again. From 10,250 to 8,300 cal yr BP, the pollen record also indicates a relatively moist, stable climate. The continued prominence of Gymnanthes , however, suggests that parts of the watershed were st ill edaphically dry or unstable, perhaps on some of the steep basin slopes. Given the limited sampling resolution (~200 yr) over this interval, the pollen record suggests drier conditions be tween 8,100 and 7,800 cal yr BP, consistent with lithologic changes. This period also marks the beginning of fundamental changes in the vegetation, that include the introduction of other secondary taxa such as Cecropia that reflect a more diverse, open forest and in creased seasonality (Figure 3-4B; (B. Leyden, pers. comm.). Comparisons with other Circum-Cari bbean and North Atlantic Records Here the Lake Petén Itzá paleoclimatic r ecord is compared with other marine and lake records from the circum-Caribbean a nd Gulf of Mexico in order to assess the regional extent of paleoclimatic changes obser ved in Lake Petén Itzá proxies. Previous studies of the last glacial-to-interglacial cycle have reported similarities between climate change in the Caribbean and the high-latitude North Atlantic on a variety of time scales (Hughen et al ., 1996; Peterson et al ., 2000). Consequently, the Petén Itzá record is also compared with proxy signals from the high latitudes of the Northern Hemisphere. There are relatively few lacustrine records of the last deglaciation in the circumCaribbean because most shallow lakes remained dry well into the early Holocene. Lake Miragoane, Haiti, and Lake Valencia, Venezu ela, are two lakes located on the northern and southern rim of the Caribbean Basin, respec tively, that were deep enough to preserve

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28 records of the latter part of the last deglaciation (Bradbury et al ., 1981; Leyden, 1985; Hodell et al ., 1991; Curtis and Hodell, 1993; Brenner et al ., 1994; Curtis et al ., 1999, 2001). Between 11,250 and 8,800 cal yr BP, oxygen isotopic records from Lakes Miragoane, Valencia, and Peté n Itzá are similar, showing large-scale fluctuations superimposed on a long-term trend of increasi ng moisture availability (Figure 5-3). A C B 0 1 2 90001000011000Lake Miragoane 18O (‰)Age (cal yr BP) 3 3.5 4 4.5Lake Petén Itzá 18O (‰) 1 2 3 4Lake Valencia 18O (‰) wet Figure 5-3. Oxygen isotopic ( 18O) records of ostracods fr om three circum-Caribbean lakes. (A) Lake Miragoane, Haiti, 18O (‰, 5-pt running average) of Candona sp. (Curtis and Hodell, 199 3), (B) Lake Petén Itzá, 18O (‰, 3-pt running average) of Limnocythere sp., and (C) Lake Valencia, Venezuela, 18O (‰, 5-pt running average) of Heterocypris sp. (Curtis et al ., 1999). Radiocarbon dates (14C yrs BP) from Lakes Mirago ane are based on carbonate microfossils (ostracods) that are suscep tible to hard-water-lake error (Deevey and Stuiver, 1964), whereas the Lakes Va lencia and Petén Itzá chronologies are based on terrestrial organic matter. Dates from the Lakes Miragoane and Valencia cores were calibrated to ca lendar years by the authors, to compare them with the Petén Itzá record. Each proxy is plotted on its own respective timescale. Several 18O maxima and minima can be correl ated among the records within the uncertainty of the chronologies. The record s from Lakes Valencia and Petén Itzá are the most reliably dated because the chronol ogies are based exclusively on radiocarbon

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29 analysis of discrete terrestr ial macrofossils. In contrast , the Lake Miragoane chronology is based on radiocarbon analys is of carbonate microfossils with the assumption of a constant hard-water lake error. Despite th e dating uncertainty in Lake Miragoane the pattern of oxygen isotope varia tion is similar to those from the other lakes indicating several abrupt shifts in mois ture availability on an othe rwise long-term trend toward wetter conditions in the early Holocene. The most detailed records of the last de glaciation and Holocene in the Caribbean come from studies of laminated sediments in the Cariaco Basin (11ºN) off the coast of northern Venezuela (Haug et al ., 2001, Peterson et al ., 2000, Hughen et al ., 1996). In general, the density record from Lake Petén Itzá Core 11A and the titanium (Ti) record from Cariaco (Haug et al ., 2001) are remarkably similar (F igure 5-4). Both sediment proxies are related to precipit ation. In Cariaco, rainfall cont rols the input of terrigenous material to the basin. Low Ti values in Cari aco sediments have been interpreted to reflect drier climate and vice-versa. In Lake Petén Itzá, detrital input and lake water chemistry control sediment composition, which is re lated indirectly to precipitation. The Petén Itzá record does not extend b ack to the time of the Bølling-Allerød or Younger Dryas events that are prominent in the Cariaco Ti signal, but rather begins in the Preboreal period when Cariaco Ti values were generally increasing but lower than those of the early Holocene. The late deglacial is marked by density variations in Core 11A that correspond to changes in Ti content of Cariaco Basin sediments. Within dating uncertainties, reductions in Cari aco Ti content correlate to intervals of increased density and gypsum content in Lake Petén Itzá (Figur e 5-4B), suggesting th at the dry Preboreal

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30 events (PBE1-4) observed in the Petén Itzá record may have been pan-Caribbean in extent. 6080100120August -February Insolation at 15oN ( W m-2 ) 4000 6000 8000 10000 12000 14000 00.150.300.45Age (cal yr BP)Cariaco Basin Ti (%) 1.2 1.4 1.6 1.8Lake Petén ItzáCore 11A Density (g cc-1) PB Y-D B-A8.2-kyr EventWet Dry PBO/ PBE1H PB/H transition 10000 10500 11000 11500 1.4 1.6 1.8Age (cal yr BP)Density (g cc-1) 0.200.250.30Cariaco Basin Ti (%)PBE1 PBE2 PBE3 PBE4 A B Lake Petén ItzáCore 11A Figure 5-4. Comparison of density measured in Petén Itzá Core 11A with percent Titanium from the Cariaco Basin (Haug et al ., 2001). (A) Density measured in Core 11A (black line; g cc-1; inverted scale) plotted versus a three-point running average of percent Titanium (gray line; Ti, %), and August minus February insolation (dashed line; W m-2) at 15ºN latitude (Berger, 1978). Major cooling events observed in the No rth Atlantic such as the 8.2-kyr Event (Alley et al ., 1997) and Preboreal Oscilla tion (PBO) at ~11,300 cal yr BP (Björck et al ., 1997) are highlighted. Major c limate intervals are denoted as the Holocene (H), Preboreal (PB), Y ounger-Dryas (Y-D), and Bølling-Allerød (B-A). Each record is plotted on its own respective timescale. (B) Petén Itzá Core 11A density smoothed with a 5pt running average and Cariaco Ti smoothed with a 15-pt running average to mute short-term variability. The Cariaco Ti record was shifted 100 yrs younger by correlating the PB/H transition. This was done to illustrate changes observed in the two records.

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31 At the end of the Preboreal period (~10,350 cal yr BP), both records show an abrupt shift that suggests increased precipitati on (Figure 5-4A). This transition is more pronounced in the Petén Itzá density record than in Cariaco Ti owing to the sudden cessation of gypsum deposition in the lake. During the early-to-middle Holocene, the two records track one another closely, and display two synchronous returns to inferred drier conditions (Figure 5-4A ). The first, centered at 9,400 cal yr BP was small and brief (~100 yrs). The second, centered at 8,000 cal yr BP, was greater in magnitude and longer in duration (~300 yrs). The latt er event is also recorded in a speleothem from lowland Costa Rica, that suggests this was a time of protracted dry conditi ons associated with a weakening of the Central American monsoon (Lachniet et al ., 2004). The Gulf of Mexico may have played an important role in regional climate during the last deglaciation because of meltwater input derived from the retreat of the Laurentide Ice Sheet. Many studies have focused on the early part of the la st deglaciation (i.e. Bølling-Allerød/Younger-Dryas transition) wh en meltwater was redirected from the Mississippi River to the St. Lawrence Ri ver into the North Atlantic (Clark et al ., 2001). A recent study, however, suggests that episodic meltwater floods to the Gulf of Mexico continued after the Younger-Dryas period. Ah aron (2003) identified four events during the Preboreal, when meltwater was rerout ed south. These are centered at 9,900, 9,700, 9,400, and 9,100 14C yr BP. When converted to calenda r years, these events are dated at 11,000, 10,700, 10,400, and 10,000 cal yr BP (Table 51; Aharon, pers. comm.). Three of these discharge events co rrespond with the Preboreal even ts (PBE1-4) observed in the Petén Itzá density and 18O records (Figure 5-2), as well as variations in Cariaco Ti (Figure 5-4B). This may suggest that epis odic meltwater discharg e into the Gulf of

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32 Mexico during the Preboreal was sufficient to cause regional changes in E/P. Alternatively, the correlation between Caribb ean drying and meltwater pulses to the Gulf of Mexico may represent responses to a comm on forcing, such as deglaciation in high northern latitudes. Table 5-1. Chronology of Preboreal events (PBE 1-4) recorded in Lake Petén Itzá Core 11A compared to periods of increased meltwater delivery (MWF-5 a,c,e,g) to the Gulf of Mexico (Aharon, 2003) a nd the Preboreal Oscillation (PBO, Björck et al ., 1997). Numbers in parentheses in dicate (a) times of peak aridity in the Petén, inferred from 18O of ostracods, and (b) maximum meltwater fluxes to the Gulf of Mexico. Preboreal Events (PBE) Intervala (cal kyr BP) GOM and NA Events Intervalb (cal kyr BP) MWF-5 g 9.75-10.07 (10.0) 4 10.31-10.46 (10.4) MWF-5 e 10.23-10.43 (10.4) 3 10.66-10.80 (10.7) MWF-5 c 10.69-10.79 (10.7) 2 10.88-11.01 (10.9) MWF-5 a 10.97-11.07 (11.0) 1 11.15->11.25 (11.2) PBO 11.15-11.30 Finally, the Lake Petén Itzá 18O and density records are compared with paleoclimate changes in the high-la titude North Atlantic. Bond et al . (2001) used fluctuations in hematite stained grains (HSG) to infer increases in drift ice associated with cool SST in the North Atlantic for the last glaciation and Holo cene. From 11,500 to 8,000 cal yr BP, they recognized four distin ct peaks in HSG abundance centered at 11,300, 10,300, 9,400, and 8,400 cal yr BP (Figure 5-5). The three older events correlate with inferred dry climate conditi ons observed in the Petén Itzá 18O record (Figure 5-5). Furthermore, three dry events that are also obs erved as density increas es in the Petén Itzá record coincide with abrupt decreases in 18O values measured in the GISP2 ice core (Figure 5-6; Stuiver et al ., 1995). The two most pronounced events, the Preboreal Oscillation (PBO) at ~11,300 cal yr BP (Björck et al ., 1997), which corresponds to PBE1 (Table 5-1), and the 8.2-kyr Event (Alley et al ., 1997) have been interpreted as periods of significant cooling in the high-lati tude North Atlantic. It is, th erefore, suggested that cool

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33 events in the high-latitude North Atlantic we re associated with dr y climate conditions in the northern lowland Neotropics. 3 3.5 4 4.5Lake Petén Itzá 18O (‰) 5 10 15 20HSG (%) -0.05 0 0.05 0.1 80009000100001100010Be Flux (105atoms cm-2yr-1)Age (cal yr BP)A C B 8 7 6 5 dry cool PBO PBE1 Figure 5-5. Comparison of ostracod 18O from Core 11A with records of sea ice extent and solar variability from the hi gh-latitude North Atlantic. (A) 10Be Flux (105 atoms cm-2 yr-1, smoothed and detrended) from the GISP2 and GRIP ice core records, after Bond et al . (2001), (B) stacked plot of percent hematite stained grains from North Atlantic cores (HSG, %; Bond et al ., 2001), and (C) oxygen isotopic composition ( 18O, ‰) of Petén Itzá ostracods, which was smoothed with a 3-pt running average to better illu strate long-term variability. Each record is plotted on its own respective timescale. dry cool 1.2 1.4 1.6 1.8Density (g cc-1) -38 -36 -34GISP2 18O (‰) 8.2-kyr Event PBO/ PBE1800090001000011000 Age (cal yr BP) A B 9.4-kyr Event Figure 5-6. Comparison of the GISP2 ice core 18O with density measured in Core 11A. (A) Oxygen isotopic composition ( 18O, ‰) of ice from the GISP2 ice core (Stuiver et al ., 1995) with (B) density (g cc-1) from Lake Petén Itzá Core 11A. Major cooling events observed in the No rth Atlantic such as the 8.2-kyr Event (Alley et al ., 1997) and Preboreal Oscilla tion (PBO) at ~11,300 cal yr BP (Björck et al ., 1997) are highlighted. Each proxy is plotted on its own respective timescale.

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34 Proposed Mechanisms for Climate Change in the Preboreal and Early Holocene Precipitation proxies in the circum-Caribbe an display a coherent response during the latter part of the last degl aciation and early Holocene. This is expected because the northern Neotropics are influenced by the sa me climate regime, where rainfall is related to the intensity of the annual cycle and associ ated displacement of the Atlantic ITCZ and Azores-Bermuda high-pressure system (Hodell et al ., 1991; Peterson et al ., 2000; Haug et al ., 2001). This mechanism has been show n to operate on short (annual) to long (millennial) timescales (Hodell et al ., 1991; Chang et al ., 1997; Peterson et al ., 2000; Haug et al ., 2001; Lea et al ., 2003; Black et al ., 2004; Chiang et al ., 2003, 2004). In turn, the mean latitudinal position of the ITCZ and Azores-Bermuda subtropical high may be influenced by numerous factors including: tropical Atlantic SST, seasonal insolation, glacial boundary conditions, ther mohaline circulation (via cro ss equatorial heat transport and sea ice extent), solar irradiance, and o cean-atmosphere interac tions such as NAO and ENSO (Hodell et al ., 1991; Chang et al ., 1997; Peterson et al ., 2000; Haug et al ., 2001; Poore et al ., 2003; Chiang et al ., 2003, 2004). Long-term (glacial-to-interg lacial) variations in Ne otropical precipitation are affected by the seasonal distri bution (Aug.-Feb.) of insolation related to variations in Earth’s orbit, especially precession (Hodell et al ., 1991; Haug et al ., 2001). Precipitation in the northern Neotropics is enhanced wh en the seasonal insolation difference is high, and reduced when seasonality is low. L ong-term changes in paleoprecipitation proxies (density and 18O) in Lake Petén Itzá cores generally follow the signal of seasonal insolation difference at 15oN (Figure 5-4A), but orbital fo rcing cannot explain the abrupt changes that occurred during th e latter part of the last degl aciation and early Holocene.

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35 During the Preboreal, the general trend to ward more humid conditions in the Petén was interrupted by four dry events (PBE1-4) centered at 11,200, 10,900, 10,700, and 10,400 cal yr BP (Figure 5-2). The oldest event (PBE-1) co incides with the Preboreal Oscillation (Björck et al ., 1997; van der Plicht et al ., 2004). The three younger events appear to correspond with episodic diversions of glacial meltwater to the Gulf of Mexico (Table 5-1; Aharon, 2003) that were relate d to changes in glac ial boundary conditions (Clark et al ., 2001). A possible explanation fo r this phenomenon comes from modeling studies that impose a 6ºC cooling of the Gulf of Mexico related to the delivery of cold, fresh glacial waters to the basin (Overpeck et al ., 1989; Oglesby et al ., 1989; Maasch and Oglesby, 1990). These model sensitivity tests imply that cooling Gulf of Mexico SST results in a westward shift of the Azores -Bermuda high to a position over the IntraAmericas Sea. This would, in turn, suppre ss convection and reduce precipitation in the region (Hastenrath, 1984). Meltwater discha rge during the Preboreal, however, was significantly less than that used to infer a 6º C cooling of the entire Gulf of Mexico. Instead, meltwater fluxes were more comparable in magnitude to the largest of modern Mississippi River floods (Aharon, 2003), which probably only infl uenced part of the Gulf of Mexico. Alternatively, early Holocene de glacial events may have provided meltwater input to both the Gulf of Mexico and high-latitude No rth Atlantic, thereby causing cooling, an expansion of sea ice, and perh aps a reduction in the Atlantic meridional overturning circulation (MOC). Two of the Preboreal Events (PBE1 and PBE4) at 11,200 and 10,400 cal yr BP, respectively, and an early Holocene event at 9,4 00 cal yr BP may correlate to increases in the 18O records of Lake Miragoane and Lake Va lencia (Figure 5-3; Curtis and Hodell,

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36 1993; Curtis et al ., 1999). These dry events together with another early Holocene event centered at 8,000 cal yr BP, correspond within chronological uncertainty, to cooler temperatures inferred from low 18O values in the GISP2 ice core (Figure 5-6; Stuiver et al ., 1995) and fluctuations in the abundance of hematite stained grains (HSG) found in high-latitude North Atlantic cores (Figure 5-5; Bond et al ., 2001). Bond et al . (2001) related fluctuations in HSG abundance w ith changes in the production rates of 10Be and 14C, such that increases in HSG abundance occurred during times of decreased solar irradiance and cold temperatures in the high-l atitude North Atlantic. Increased aridity in the circum-Caribbean may have accompanied these cooling events, and may have been caused by a southward displacement of the IT CZ related to decreased solar luminosity, increased sea ice, or decreased thermohaline circulation. For example, the 8.2-kyr Event, which was the most prolonged and distinct cool ing in the Northern Hemisphere since the Younger-Dryas, may have been related to both reduced solar luminosity (Muscheler et al ., 2004) and a reduction in MOC from glacial meltwater discharge into the North Atlantic via Hudson Strait (Clark et al ., 2001). A similar mechanism has been proposed for the Preboreal Oscillation (PBO; Björck et al ., 1997; van der Plicht et al ., 2004).

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37 CHAPTER 6 SUMMARY AND CONCLUSIONS Seismic data indicate that pr ior to the last deglaciation, th e level of Lake Petén Itzá was about ~58 m below modern stage. This observation is consistent with previous studies of Petén lakes that i ndicated arid climate conditions. The last deglaciation saw an abrupt shift from arid to humi d conditions in the region. The age of the oldest deep-water core from Petén Itzá is 11,250 cal yr BP, whic h captures only the term inal part of this arid-to-humid transition. Pollen assemblages from the base of the core demonstrate that a mesic forest had been largely established by ~11,250 cal yr BP, but Petén Itzá’s level was still >35 m below modern. From 11,250 to 10,350 cal yr BP during the Preboreal Period, cores from <35 m below present water depth contain soil horizons, indicating subaerial exposure. During this period, deep-water cores from >50 m below present water depth contain gypsum sands interbedded with carbonat e-rich clays, indicat ing several dry-wet cycles. Oxygen isotopic ratios generally decrease during the Pre boreal Period indicating a trend toward more mesic conditions. Th is trend was interrupted, however, by four Preboreal dry events (PBE1-4) centered at 11,200, 10,900, 10,700, and 10,400 cal yr BP. The four events correlate to decreases in th e Cariaco Ti record, suggesting they may have been widespread throughout the circum-Caribbe an region. Three of the events coincided with episodic diversions of glacial meltwater to the Gulf of Mexico. At 10,350 cal yr BP, increased precipitation and lake level rise is documented in deep-water cores by cessation of gypsum deposition and the onset of lacustrine sedimentation at shallow wate r sites. Increased abundance of tropical mesic pollen taxa

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38 lagged this transition by ~100 yrs. This event occurred at the Preboreal-to-Boreal transition and coincided with an inferred in crease in precipitation recorded throughout the circum-Caribbean. The early Holocene was a time of generally reduced climate variability and steadily increasing moisture avai lability except for two returns to slightly drier conditions centered at, 9,400 and 8,000 cal yr BP. The prolonged dry event at 8,000 cal yr BP correlates with infe rred reductions in circum-Cari bbean precipitation as well as cooler temperatures in the hi gh-latitude North Atlantic. Comparison of the Lake Petén Itzá record w ith other lacustrine and marine records from the circum-Caribbean and Gulf of Me xico suggests that climate in this region responded coherently during th e Preboreal and early Holo cene periods. In addition, lowland Neotropical climate during this time was tightly linked to high-latitude climate change in the North Atlan tic. Although the general tr end in the northern lowland Neotropics was toward increasingly mesi c conditions from ~11,250 to 7,500 cal yr BP, climate became drier at times of cooling in the high-latitude North Atlantic. These observed changes in lowland Neotropical precipitation we re probably related to the intensity of the annual cycle and associated displacements in the mean position of the ITCZ and Azores-Bermuda subtropical high. This mechanism operated on a variety of timescales and responded sensitively to cha nges in solar radiation, glacial meltwater, North Atlantic sea ice ex tent, and Atlantic MOC.

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39 APPENDIX A CORE REFERENCE GUIDE Appendix A provides detailed explanations of proxy data measured in cores taken along a depth transect on seismic line 11 (F igure 2-1). Appendix A also provides information about sampling resolution for the various proxies (Table A-1) and explains the splicing technique used to correct each co re to its proper depth below lake floor (dblf). Depth Transect 11 included six coring stat ions (A-F) at which nine cores were collected over a 5-day period in June 2002. Core s at stations A, C, and E were replicated in an attempt to obtain longer cores after adding more weight to the Kullenberg-type piston corer. Cores along Depth Transect 11 ranged from 9.3 to 63.2 meters below lake surface (relative to 2002 lake le vel) and measured from 200 to 585 cm in length (Table A-1). A mud-water-interface (MWI) core wa s also recovered at each coring station. All cores retrieved from Lake Petén Itzá we re measured at 0.5-cm intervals using a GEOTEK multi-sensor core l ogger (see also Chapter 2) fo r gamma ray attenuation, loop magnetic susceptibility, core thickness, and p-wave velocity. These raw data were subsequently processed and calibrated to produce gamma-ray attenuation (GRA) bulk density, magnetic susceptibility, p-wave veloc ity, impedance, and porosity. Cores were split and imaged using the GEOTEK digital color line-scan camera (see Chapter 2). Images were then analyzed at 0.1-cm interv als for red, green, blue intensity between 0 and 255 nm.

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40Table A-1. Core reference table including: co re name, site, location, water depth, top of the core depth below lake floor (dblf ) and composite depth below lake floor (cdblf), sa mpling resolution, and proxy variables measured. Core Site Longitude Latitude Water Depth (m) Depth Below Lake Floor (cm-dblf) Composite Depth Below Lake Floor (cm-cdblf) Length (cm) Notes Variables measured PI 5-VI-02 11A 17o00.141 89o46.795 60.9 22 37 500 Not sampled MSCL 11A-MWI 0 64 Not sampled MSCL PI 8-VI-02 11A 17o00.120 89o46.752 58.2 50 58 500 Sampled at 1-cm interv al Elemental, Isotope, MSCL, XRF 11A-MWI 0 69 Extruded at 1-cm intervalsElemental, MSCL PI 5-VI-02 11B 16o59.870 89o46.751 51.6 15 24 500 Sampled at 5-cm interval Elemental, MSCL, XRF 11B-MWI 0 63 Extruded at 1-cm intervalsMSCL PI 6-VI-02 11C 16o59.502 89o46.795 31.8 30 30 265 Not sampled MSCL 11C-MWI 0 59 Extruded at 1-cm intervalsElemental, MSCL PI 9-VI-02 11C 16o59.476 89o46.767 30 0 25 275 Sampled at 1-cm interval Elemental, MSCL 11C-MWI 0 42 Lost MSCL PI 6-VI-02 11D 16o59.260 89o46.742 20.9 10 25 200 Sampled at 5-cm interval Elemental, MSCL 11D-MWI 0 30 Extruded at 1-cm intervalsMSCL PI 6-VI-02 11E 16o58.973 89o46.706 9.3 10 43 250 Not sampled MSCL 11E-MWI 0 42 Not sampled MSCL PI 8-VI-02 11E 16o59.013 89o46.732 9.7 30 51 225 Sampled at 5-cm interval Elemental, MSCL 11E-MWI 0 42 Extruded at 1-cm intervalsMSCL PI 9-VI-02 11F 17o00.248 89o46.802 63.2 0 ND (>53 cm) 585 Not sampled MSCL, XRF 11F-MWI 0 53 Not sampled MSCL PI 10-VI-02 8A 16o59.439 89o43.806 43.8 30 25 500 Not sampled MSCL 8A-MWI 0 72 Not sampled MSCL PI 10-VI-02 8B 16o58.949 89o44.122 27.3 0 ND (>10cm) 270 Not sampled MSCL 8B-MWI 0 10 Not sampled MSCL PI 7-VI-02 5A 17o00.236 89o47.559 70.9 0 ND (>55 cm) 590 Not sampled MSCL 5A-MWI 0 55 Not sampled MSCL PI 7-VI-02 14A 17o00.180 89o49.508 105 0 ND (>46cm) 570 Not sampled MSCL 14A-MWI 46 Not sampled MSCL MWI – Mud-water interface core NDNon-Definitive MSCL – Multi-Sensor Core Logger XRF – X-ray Fluorescence

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41 The working halves of Cores 11A, 11B, 11C , 11D, and 11E were initially sampled at 5-cm resolution over their entire respectiv e lengths. Subsequently, the remainders of Cores 11A, 11C, and 11E were sampled at 1-cm intervals. Each half-round sample was sub-sampled (~5 cc) for elemental geochemical analysis. Elemental geochemical analysis included total carbon (TC), total inorganic carbon (TIC ), total nitrogen (TN), and total sulfur (TS). For certain cores, total organic carbon (TOC) was estimated by subtracting TIC from TC. The remainder of the sample was wet sieved at 63-µm to isolate material for radiocarbon datin g and stable isotopic analysis. A MUCK corer was used to trigger the piston core and obtain samples of the uppermost sediment profile. Because the upper sediments were not completely retrieved using the Kullenberg-type pist on corer, the MUCK cores we re used to determine how deep the Kullenberg corer actually penetrated into the sediment. This is because the MUCK corer captures the mud-water interf ace (MWI), which allows for depth below lake floor (dblf), estimated in the field, to be corrected to a more accurate composite depth below lake floor (cdblf; Table A-1). Kullenberg-type cores were spliced to the MUCK cores using variations in density, verified with magnetic susceptibility and geochemical data. For most cores this process was successful, but for a few cores it was not possible to splice the MUCK and Kullenberg cores together because of a gap between the bottom of the mud-water interface (MWI) core and the top of the piston core. Deep-Water Cores Deep-water cores are defined as those re trieved from >50 m modern water depth and include Cores 11A, 11B, and 11F (Figures A-1, 2, 3). These cores are divided into four distinct lithologic units (Table A-2) usi ng sediment description techniques defined in Schnurrenberger et al . (2003). Unit I consists of greenis h-gray, organic-ri ch silty-clay.

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42 Unit II is dominated by cohesive gray clay that varies between finely laminated (mmscale) and broadly laminated (cm-scale) light -dark couplets. Unit III is comprised of broadly laminated (cm-scale), greenish-to-gray, organic-rich silty-clay, similar to Unit I. Unit IV is composed of light brown gypsum sands interbedded with very light brown, carbonate-rich silty-clay. Cores 11A and 11B contain all lithologic units, whereas Core 11F consists of an expanded ve rsion of Units I and II only. Table A-2. Lithologic description of deep -water cores (>50 m m odern water depth). Unit Lithologic Description I Greenish-gray, organic-rich silty-clay. II Broadly-to-finely (cm-to-mm-scale) laminated, gray clay. Unit II grades upwards into Unit I. III Laminated (cm), greenish-gray silty-clay. Unit III grades upwards into Unit II. IV Light Brown gypsum sands interbedded with very light brown carbonate-rich silty clays. Unit IV transitions sharply to Unit III. Core 11A Core 11A (Figure A-1) consists of four ~125-cm sections (~500 cm total length) that were sampled continuously at 1-cm inte rvals. TC and TIC were measured on every sample and TS was measured at 5-cm interv als in the three upper sections and 1-cm intervals in the bottom section (Section 4). For each interval TOC was estimated by subtracting TIC from TC. Core 11A-MWI was extruded in the lab a nd sampled at 1-cm intervals. Subsamples were taken from each 1-cm interval for elemental analysis (~5 cc) and future lead-210 dating (~10 cc). The remaining sediment was wet sieved at 63m to isolate material for isotopic analysis and radiocar bon dating. TC and TIC were measured every 1-cm, but TS was not measured. For each in terval TOC was estimated by subtracting TIC from TC.

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43 0 0714 100 200 300 400 500TS (%) 0714TC (%) 048TIC (%) 0612TOC (%) 11.52Density (g cc1) 05Mag.Susc. (cgs) 0 100 200 300 400 500Depth in Core (cm) 1 2 3 4 MWI Figure A-1. Image of Core PI 8-VI-02 11A with plots of physical and elemental geochemical properties. Section br eaks are denoted by dashed line. Core 11B Core 11B (Figure A-2) consists of four ~125-cm sections (~500 cm total length) and was sampled every 5 cm over its entire length. Each sample was analyzed for TIC and TS. Core 11B-MWI has not been extr uded. Samples for pollen analysis (~1 cc) were also taken at 2-to-20-cm intervals.

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44 11.52Density (g cc1) 05Mag.Susc. (cgs) 0 100 200 300 400 500Depth in Core (cm) 048TIC (%)0 048 100 200 300 400 500TS (%)MWI 1 2 3 4 Figure A-2. Image of Core PI 5-VI-02 11B with plots of physical and elemental geochemical properties. Section br eaks are denoted by dashed line. Core 11F Core 11F (Figure A-3) consists of four ~120-cm sections and one ~85-cm section (~585 cm total length) and has not been sample d. Core 11F-MWI has not been extruded. Core 11F has only been analyzed usi ng the GEOTEK-MSCL for various physical properties such as density a nd magnetic susceptibility.

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45 1.21.5 Density (g cc1) 036 0 100 200 300 400 500 600 Mag.Susc. (cgs) 0 100 200 300 400 500 600Depth in Core (cm) MWI 1 2 3 4 5 Figure A-3. Image of Core PI 9-VI-02 11F w ith plots of physical properties. Section breaks are denoted by dashed line. Shallow-Water Cores Shallow-water cores a re defined as th ose retrieved from <35 m modern water depth and include Cores 11C, 11D, and 11E (F igures A-4, 5, 6). The stratigraphy of shallow-water cores is divided into three broad lithologic units (Table A-3) based on

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46 sediment description technique s defined in Schnurrenberger et al . (2003). Unit I varies among the cores. In Cores 11D and 11E, it consists of alternating bands of light brown and reddish brown, shell-rich sandy-clay. In Core 11C, however, Unit I is subdivided into four sub-units: Unit Ia is a greenish-gr ay, organic-rich, siltyclay, Unit Ib is a laminated, gray clay similar to Unit II obser ved in deep-water cores. Unit Ic is a laminated, greenish-gray, organic-rich silt-cla y similar to Unit III observed in deep-water cores. Unit 1d is similar to Unit I observed in shallow-water Cores 11D and 11E. Unit II is composed of dark gray silty-clay with an abundance of charcoal fragments and what appears to be root material. Unit II is a pale osol. Unit III consists of very light gray, massive silty-clay with abundant altered she ll material. Lithologi cally these cores are similar below the sharp transition to dark gray silty-clay, which maybe be due to alteration of the underlying sediments when th ey were sub-aerially exposed during the last glaciation (see discussion in Chapter 5). Table A-3. Lithologic description of shallo w-water cores (<35 m modern water depth). Unit Lithologic Description Ia Greenish-gray, organic-rich silty-clay. Ib Laminated, gray clay. Separated from Unit Ia by a shell lag. Ic Laminated, greenish-gray, organi c-rich silty clay. Separated from Unit Ib by a shell lag. Id/I Alternating bands of light br own and reddish-brown, shellrich, sandy clay. Separated from Unit Ic by a shell lag. Similar to Unit I in Cores 11D and 11E. II Dark gray, silty-clay (paleosol). Transitions sharply to Unit Id. III Massive, very light gray silty clay. Gradational transition into Unit II.

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47 Core 11C Core 11C (Figure A-4) consists of two ~100-cm sections and one ~75-cm (~275 cm total length) that were samp led continuously at 1-cm intervals. TC and TIC were measured on every sample and TS was measured at 5-cm intervals from the top of the core to the base of Unit II (paleosol). Co re 11C-MWI was extruded in the lab at 1-cm intervals. Sub-samples were taken from each 1-cm interval for elemental analysis (~5 cc) and future 210Pb dating (~10 cc). The rest was wet sieved at 63m to isolate material for isotopic analysis and radiocarbon dating. TC and TIC were measured on every 1-cm sample from Core 11C-MWI, but TS was not measured. For all intervals in Core 11C and Core 11C-MWI, TOC was estimated by subtracting TIC from TC. 1.21.8Density (g cc1) 03Ma g .Susc. ( c g s ) 0 100 200 300Depth in Core (cm) 0816TC (%) 0612TIC ( % ) 0510TOC (%) 0120 100 200 300 TS ( % ) MWI 1 2 3 Figure A-4. Image of Core PI 9-VI-02 11C with plots of physical and elemental geochemical properties. Section br eaks are denoted by dashed line.

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48 Core 11D Core 11D (Figure A-5) consists of two ~100-cm sections (~200 cm total length) and was sampled at 5-cm intervals. TC a nd TIC were measured on every sample and TS was measured from the top of the core to th e base of Unit II (paleosol). Core 11D-MWI has not been extruded. For all intervals in Core 11D, TOC was estimated by subtracting TIC from TC. Samples for pollen analysis (~ 1 cc) were collected at 5-cm intervals. Pollen results are reported in Hillesheim et al . (in press). 11.52Density (g cc1) 020Mag.Susc. (cgs) 0 100 200Depth in Core (cm) 0714TC (%) 0612TIC (%) 036TOC (%) 00.51 0 100 200TS (%)MWI 1 2 Figure A-5. Image of Core PI 6-VI-02 11D with plots of physical and elemental geochemical properties. Section br eaks are denoted by dashed line. Core 11E Core 11E (Figure A-6) consists of one ~100-cm section and one ~125-cm section (~225 cm total length), that were sampled at 1-cm intervals. TC and TIC at 5-cm intervals over the entire length of the core a nd TS was measured from the top of the core to the base of Unit II (paleosol). Core 11E-M WI has not been extruded. For all intervals in Core 11E, TOC was estimated by subtracting TIC from TC.

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49 11.52Density (g cc1) 030Mag.Susc. (cgs) 0 100 200Depth in Core (cm) 0714TC (%) 0612TIC (%) 036TOC (%) 00.51 0 100 200TS (%)60 MWI 1 2 Figure A-6. Image of Core PI 8-VI-02 11E with plots of physical and elemental geochemical properties. Section br eaks are denoted by dashed line.

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50 APPENDIX B ELEMENTAL GEOCHEMISTRY DATA FOR CORES 11A-11E Appendix B presents tabular elemental geoc hemistry data from Lake Petén Itzá Cores 11A, 11B, 11C, 11D, and 11E as well as Cores 11A-MWI (m ud-water interface) and 11C-MWI. Each variable was sampled at various resolutions and has been assigned a core depth in centimeters below lake floor (cm-dblf). In the case of Cores 11A and 11C, a composite depth below lake floor (c m-cdblf) was also assigned based on the alignment of density variations observed in the Kullenberg-type piston core and the MWI core (see discussion in Appendix A). Each de pth interval in Core 11A was assigned an age (in cal yr BP) by applying the age model di scussed in Chapter 3. Depth in Core 11B was correlated to depth in Core 11A by matc hing variations in color (RGB) intensity (correlation coefficient, r = 0.84) using Analyseries 1.1 (Paillard et al ., 1996). This was done so that the Core 11A age model could be applied to Core 11B. Table abbreviations are as follows: total nitrogen (TN), tota l carbon (TC), total inorganic carbon (TIC), total organic carbon (T OC), total sulfur (TS), weight percent calcium carbonate (CaCO3; %), weight percent organic ma tter (OM; %), weight percent gypsum (CaSO4·2H2O; %), weight percent clay (Cla y; %). Weight percent calcium carbonate was calculated by multiplying TIC by 8.33. Weight percent organic matter was calculated by subtracting TIC from TC to get TOC, and multiplying TOC by 2.2. Weight percent gypsum was calculated by mu ltiplying TS by 5.38. Weight percent clay was estimated by subtracting the sum of CaCO3, OM, and CaSO4·2H2O (%) from 100.

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51 Table B-1. Elemental geochemistry data for Core PI 8-VI-02 11A retrieved from 58.2 m modern (2002) water dept h at 17.000ºN and 89.779ºW. Depth in Core (cm) Composite Depth in Core (cm) Age (cal yr BP) TN TC TICTOCTS CaCO3 (%) OM (%) CaSO4 ·2H2O (%) Clay (%) 52.0 58.5 1478.9 0.29 7.74 3.20 4.51 1.02 26.88 9.92 5.50 57.69 53.0 59.5 1483.3 0.32 7.76 3. 09 4.65 25.92 10.23 54.0 60.5 1487.8 0.27 7.65 3. 81 3.81 32.02 8.37 55.0 61.5 1492.3 0.30 8.00 3. 68 4.29 30.92 9.44 56.0 62.5 1496.8 0.30 8.02 3. 78 4.21 31.72 9.26 57.0 63.5 1501.3 0.31 8.18 3.78 4.37 0.62 31.76 9.61 3.36 55.27 58.0 64.5 1505.7 0.27 7.95 4. 25 3.67 35.65 8.07 59.0 65.5 1510.2 0.31 8.60 4. 08 4.49 34.26 9.88 60.0 66.5 1514.7 0.22 8.30 4. 28 3.99 35.91 8.78 61.0 67.5 1519.2 0.23 8.11 4. 18 3.89 35.13 8.56 62.0 68.5 1523.7 0.21 8.03 4.59 3.40 0.54 38.56 7.49 2.88 51.08 63.0 69.5 1528.1 0.27 8.00 4. 77 3.20 40.04 7.04 64.0 70.5 1532.6 0.27 7.77 4. 37 3.37 36.68 7.42 65.0 71.5 1537.1 0.20 7.70 4. 67 3.00 39.19 6.59 66.0 72.5 1541.6 0.20 7.62 4. 59 3.00 38.51 6.61 67.0 73.5 1546.0 0.19 7.61 4.71 2.86 0.58 39.57 6.29 3.11 51.03 68.0 74.5 1550.5 0.22 7.61 4. 80 2.78 40.30 6.11 69.0 75.5 1555.0 0.21 7.74 4. 39 3.33 36.82 7.32 70.0 76.5 1559.5 0.21 7.95 5. 05 2.87 42.37 6.31 71.0 77.5 1564.0 0.19 7.55 5. 00 2.52 41.95 5.54 72.0 78.5 1568.4 0.14 6.45 4.97 1.45 0.51 41.71 3.19 2.76 52.35 73.0 79.5 1572.9 0.19 7.52 4. 44 3.05 37.25 6.71 74.0 80.5 1577.4 0.21 7.31 4. 18 3.10 35.09 6.81 75.0 81.5 1581.9 0.23 7.54 4. 25 3.23 35.94 7.11 76.0 82.5 1586.3 0.20 7.49 4. 37 3.05 36.97 6.71 77.0 83.5 1590.8 0.16 6.83 4.37 2.39 0.44 36.95 5.26 2.39 55.40 78.0 84.5 1595.3 0.16 6.48 4. 07 2.35 34.42 5.16 79.0 85.5 1599.8 0.18 6.50 4. 12 2.33 34.79 5.12 80.0 86.5 1604.3 0.16 6.67 4. 39 2.22 37.09 4.87 81.0 87.5 1608.7 0.19 6.78 4. 56 2.15 38.57 4.72 82.0 88.5 1613.2 0.16 7.36 5.22 2.07 0.55 44.10 4.55 2.97 48.38 83.0 89.5 1617.7 0.16 6.92 4. 46 2.40 37.68 5.29 84.0 90.5 1622.2 0.16 6.77 4. 49 2.22 37.95 4.88 85.0 91.5 1626.7 0.17 6.29 4. 17 2.06 35.25 4.54 86.0 92.5 1631.1 0.14 5.92 4. 04 1.82 34.14 4.00 87.0 93.5 1635.6 0.15 5.39 3.91 1.42 0.49 33.08 3.12 2.62 61.19 88.0 94.5 1640.1 0.14 5.58 4. 09 1.43 34.57 3.14 89.0 95.5 1644.6 0.14 5.17 3. 62 1.51 30.55 3.31 90.0 96.5 1649.0 0.14 4.58 3. 05 1.49 25.75 3.27 91.0 97.5 1653.5 0.14 4.36 2. 73 1.59 23.08 3.50 92.0 98.5 1658.0 0.13 4.55 2.90 1.61 0.42 24.50 3.53 2.28 69.69

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52 Table B-1. Continued. Depth in Core (cm) Composite Depth in Core (cm) Age (cal yr BP) TN TC TICTOCTS CaCO3 (%) OM (%) CaSO4 ·2H2O (%) Clay (%) 93.0 99.5 1662.5 0.13 4.37 2. 90 1.42 24.51 3.13 94.0 100.5 1667.0 0.14 4.77 3. 16 1.57 26.74 3.44 95.0 101.5 1671.4 0.15 5.23 3. 50 1.68 29.57 3.70 96.0 102.5 1675.9 0.15 5.39 3. 59 1.75 30.33 3.85 97.0 103.5 1680.4 0.14 6.07 3.98 2.03 0.30 33.64 4.48 1.60 60.29 98.0 104.5 1684.9 0.14 6.36 4. 83 1.53 40.28 3.36 99.0 105.5 1689.3 0.15 6.79 4. 12 2.66 34.40 5.86 100.0 106.5 1693.8 0.14 7.01 5. 19 1.81 43.34 3.97 101.0 107.5 1698.3 0.13 7.28 5. 63 1.63 47.01 3.60 102.0 108.5 1702.8 0.13 7.28 5. 54 1.73 46.27 3.80 103.0 109.5 1707.3 0.14 6.78 4. 01 2.76 33.50 6.07 104.0 110.5 1711.7 0.15 6.15 4. 38 1.76 36.58 3.86 105.0 111.5 1716.2 0.13 6.31 4. 50 1.80 37.59 3.95 106.0 112.5 1720.7 0.16 5.35 3. 54 1.80 29.57 3.96 107.0 113.5 1725.2 0.15 5.83 3.22 2.61 0.58 26.85 5.74 3.10 64.31 108.0 114.5 1729.7 0.15 6.33 4. 03 2.30 33.63 5.05 109.0 115.5 1734.1 0.17 6.84 4. 60 2.23 38.36 4.91 110.0 116.5 1738.6 0.15 6.84 3. 72 3.11 31.05 6.85 111.0 117.5 1743.1 0.17 6.73 3. 86 2.86 32.19 6.30 112.0 118.5 1747.6 0.17 6.92 4.23 2.69 0.45 35.30 5.91 2.44 56.35 113.0 119.5 1752.0 0.16 6.89 4. 27 2.61 35.63 5.74 114.0 120.5 1756.5 0.18 6.81 4. 02 2.79 33.54 6.13 115.0 121.5 1761.0 0.17 7.04 4. 48 2.55 37.42 5.61 116.0 122.5 1765.5 0.16 7.19 4. 15 3.03 34.65 6.67 117.0 123.5 1770.0 0.13 8.08 4.97 3.10 0.44 41.50 6.82 2.34 49.34 118.0 124.5 1774.4 0.17 6.78 4. 23 2.54 35.30 5.59 119.0 125.5 1778.9 0.18 6.71 3. 41 3.29 28.49 7.25 120.0 126.5 1783.4 0.17 6.78 4. 69 2.05 39.42 4.52 121.0 127.5 1787.9 0.16 6.57 3. 78 2.74 31.90 6.03 122.0 128.5 1792.3 0.16 6.73 4.33 2.35 0.52 36.55 5.17 2.81 55.47 123.0 129.5 1796.8 0.16 6.86 4. 43 2.38 37.37 5.23 124.0 130.5 1801.3 0.17 6.55 4. 29 2.21 36.14 4.87 125.0 131.5 1805.8 0.15 6.82 4. 27 2.51 35.98 5.51 126.0 132.5 1810.3 0.15 6.74 4. 66 2.02 39.33 4.45 127.0 133.5 1814.7 0.15 6.57 3.76 2.77 0.30 31.72 6.09 1.60 60.59 128.0 134.5 1819.2 0.14 5.58 3. 34 2.20 28.20 4.83 129.0 135.5 1823.7 0.13 4.81 2. 55 2.22 21.52 4.89 130.0 136.5 1828.2 0.15 5.13 3. 31 1.77 27.93 3.90 131.0 137.5 1832.7 0.14 4.72 3. 02 1.59 26.05 3.50 132.0 138.5 1837.1 0.13 4.51 3.10 1.31 0.59 26.69 2.87 3.15 67.28 133.0 139.5 1841.6 0.15 4.36 2. 93 1.33 25.25 2.92 134.0 140.5 1846.1 0.13 4.16 2. 63 1.44 22.69 3.16

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53 Table B-1. Continued. Depth in Core (cm) Composite Depth in Core (cm) Age (cal yr BP) TN TC TICTOCTS CaCO3 (%) OM (%) CaSO4 ·2H2O (%) Clay (%) 135.0 141.5 1850.6 0.13 4.56 2. 95 1.51 25.42 3.33 136.0 142.5 1855.0 0.14 5.80 4. 06 1.60 34.99 3.53 137.0 143.5 1859.5 0.15 6.06 4.16 1.76 0.60 35.83 3.86 3.24 57.07 138.0 144.5 1864.0 0.16 6.37 4. 45 1.76 38.37 3.88 139.0 145.5 1868.5 0.15 6.50 4. 59 1.75 39.60 3.85 140.0 146.5 1873.0 0.17 6.00 3. 62 2.26 31.21 4.97 141.0 147.5 1877.4 0.15 6.16 3. 96 2.06 34.15 4.53 142.0 148.5 1881.9 0.17 6.25 4.08 2.04 0.55 35.13 4.48 2.96 57.44 143.0 149.5 1886.4 0.18 6.58 4. 07 2.37 35.08 5.22 144.0 150.5 1890.9 0.17 6.06 3. 82 2.10 32.97 4.63 145.0 151.5 1895.3 0.18 5.78 3. 60 2.06 31.00 4.54 146.0 152.5 1899.8 0.15 6.24 4. 10 1.99 35.38 4.39 147.0 153.5 1904.3 0.14 6.46 4.60 1.71 0.41 39.62 3.76 2.19 54.43 148.0 154.5 1908.8 0.16 5.57 3. 78 1.66 32.56 3.65 149.0 155.5 1913.3 0.18 5.63 3. 75 1.75 32.29 3.85 150.0 156.5 1917.7 0.18 5.63 3.80 1.70 0.51 32.78 3.74 2.73 60.75 151.0 157.5 1922.2 0.16 5.86 3. 95 1.78 34.02 3.91 152.0 158.5 1926.7 0.12 4.40 3. 36 0.93 28.95 2.04 153.0 159.5 1931.2 0.11 4.52 3. 82 0.67 32.10 1.47 154.0 160.5 1935.7 0.17 5.93 4. 40 1.49 37.02 3.28 155.0 161.5 1940.1 0.17 5.43 3.95 1.44 0.50 33.21 3.17 2.70 60.92 156.0 162.5 1944.6 0.15 4.98 3. 57 1.37 30.03 3.02 157.0 163.5 1949.1 0.14 4.81 3. 61 1.18 30.31 2.59 158.0 164.5 1953.6 0.14 4.95 3. 71 1.21 31.17 2.66 159.0 165.5 1958.0 0.13 4.53 3. 29 1.20 27.69 2.65 160.0 166.5 1962.5 0.13 4.00 2.86 1.11 0.62 24.05 2.44 3.35 70.16 161.0 167.5 1967.0 0.13 3.44 2. 35 1.07 19.76 2.36 162.0 168.5 1971.5 0.13 3.62 2. 70 0.90 22.67 1.97 163.0 169.5 1976.0 0.12 3.69 2. 54 1.12 21.36 2.47 164.0 170.5 1980.4 0.13 4.07 2. 83 1.21 23.82 2.66 165.0 171.5 1984.9 0.15 3.86 2.56 1.28 0.63 21.56 2.81 3.36 72.27 166.0 172.5 1989.4 0.14 3.99 2. 81 1.15 23.65 2.54 167.0 173.5 1993.9 0.14 4.40 3. 12 1.25 26.24 2.75 168.0 174.5 1998.3 0.14 4.21 2. 95 1.23 24.83 2.70 169.0 175.5 2002.8 0.15 4.57 3. 28 1.25 27.62 2.75 170.0 176.5 2007.3 0.15 4.39 3.12 1.24 0.55 26.30 2.72 2.97 68.01 171.0 177.5 2011.8 0.14 4.28 2. 89 1.36 24.38 2.98 172.0 178.5 2016.3 0.13 3.99 2. 61 1.36 21.96 2.99 173.0 179.5 2020.7 0.13 3.91 2. 49 1.40 20.94 3.08 174.0 180.5 2025.2 0.16 4.36 2. 42 1.92 20.38 4.21 175.0 181.5 2029.7 0.16 3.73 2.03 1.65 0.65 17.30 3.64 3.48 75.58 176.0 182.5 2034.2 0.14 3.51 2. 07 1.39 17.62 3.07

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54 Table B-1. Continued. Depth in Core (cm) Composite Depth in Core (cm) Age (cal yr BP) TN TC TICTOCTS CaCO3 (%) OM (%) CaSO4 ·2H2O (%) Clay (%) 177.0 183.5 2038.7 0.14 3.52 1. 76 1.72 14.98 3.79 178.0 184.5 2043.1 0.19 3.79 1. 87 1.88 15.88 4.14 179.0 185.5 2047.6 0.17 3.58 1. 87 1.67 15.88 3.68 180.0 186.5 2052.1 0.19 3.73 1.74 1.96 0.64 14.77 4.31 3.46 77.45 181.0 187.5 2056.6 0.17 3.23 1. 52 1.67 12.96 3.68 182.0 188.5 2061.0 0.17 3.35 1. 68 1.63 14.32 3.58 183.0 189.5 2065.5 0.20 3.76 2. 04 1.67 17.36 3.68 184.0 190.5 2070.0 0.18 3.67 2. 03 1.60 17.29 3.51 185.0 191.5 2079.4 0.15 3.71 2.06 1.60 0.60 17.53 3.53 3.24 75.70 186.0 192.5 2088.8 0.20 3.46 1. 73 1.69 14.69 3.73 187.0 193.5 2098.2 0.19 3.57 1. 79 1.73 15.26 3.82 188.0 194.5 2107.5 0.16 3.55 1. 88 1.64 15.96 3.61 189.0 195.5 2116.9 0.21 3.93 1. 95 1.94 16.60 4.26 190.0 196.5 2126.3 0.20 3.46 1.59 1.84 0.61 13.56 4.04 3.26 79.14 191.0 197.5 2135.7 0.18 3.91 2. 05 1.81 17.43 3.99 192.0 198.5 2145.1 0.20 3.31 1. 73 1.54 14.73 3.39 193.0 199.5 2154.5 0.22 3.33 1. 57 1.73 13.34 3.81 194.0 200.5 2163.9 0.27 2.93 1. 41 1.50 11.95 3.29 195.0 201.5 2173.2 0.21 3.41 1.81 1.56 0.75 15.39 3.43 4.05 77.13 196.0 202.5 2182.6 0.21 3.54 1. 92 1.59 16.27 3.49 197.0 203.5 2192.0 0.15 4.10 2. 56 1.49 21.73 3.28 198.0 204.5 2201.4 0.13 4.40 2. 85 1.50 24.19 3.29 199.0 205.5 2210.8 0.30 4.26 2. 69 1.52 22.84 3.34 200.0 206.5 2220.2 0.27 4.10 2.61 1.44 0.64 22.15 3.17 3.46 71.22 201.0 207.5 2229.6 0.32 4.58 2. 97 1.55 25.24 3.41 202.0 208.5 2238.9 0.49 4.85 3. 22 1.57 27.31 3.46 203.0 209.5 2248.3 0.35 4.94 3. 13 1.75 26.61 3.84 204.0 210.5 2257.7 0.31 4.73 2. 93 1.74 24.90 3.84 205.0 211.5 2267.1 0.43 4.96 2.93 1.97 0.61 24.89 4.34 3.26 67.51 206.0 212.5 2276.5 0.62 4.53 2. 56 1.92 21.74 4.22 207.0 213.5 2285.9 0.58 4.37 2. 62 1.69 22.28 3.72 208.0 214.5 2295.3 0.62 4.46 2. 80 1.61 23.78 3.53 209.0 215.5 2304.6 0.39 4.18 2. 58 1.55 21.94 3.41 210.0 216.5 2314.0 0.47 3.82 2.16 1.63 0.60 18.30 3.58 3.24 74.88 211.0 217.5 2323.4 0.63 3.94 2. 14 1.77 18.14 3.89 212.0 218.5 2332.8 0.59 4.25 2. 49 1.71 21.18 3.77 213.0 219.5 2342.2 0.70 4.21 2. 52 1.64 21.41 3.60 214.0 220.5 2351.6 0.75 4.39 2. 72 1.61 23.14 3.54 215.0 221.5 2361.0 0.93 4.34 2.66 1.62 0.54 22.68 3.55 2.90 70.87 216.0 222.5 2370.4 0.55 4.32 2. 68 1.59 22.83 3.49 217.0 223.5 2379.7 0.56 4.69 3. 19 1.43 27.13 3.15 218.0 224.5 2389.1 0.67 4.97 3. 32 1.58 28.27 3.47

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55 Table B-1. Continued. Depth in Core (cm) Composite Depth in Core (cm) Age (cal yr BP) TN TC TICTOCTS CaCO3 (%) OM (%) CaSO4 ·2H2O (%) Clay (%) 219.0 225.5 2398.5 0.96 4.94 3. 22 1.65 27.39 3.63 220.0 226.5 2407.9 1.02 5.59 3.85 1.65 0.56 32.77 3.64 2.99 60.60 221.0 227.5 2417.3 0.67 5.46 3. 67 1.71 31.28 3.76 222.0 228.5 2426.7 0.62 5.13 3. 76 1.30 31.84 2.87 223.0 229.5 2436.1 1.06 5.69 4. 00 1.60 34.07 3.53 224.0 230.5 2445.4 0.87 5.39 3. 72 1.60 31.65 3.51 225.0 231.5 2454.8 0.47 4.79 3.08 1.64 0.63 26.26 3.60 3.36 66.77 226.0 232.5 2464.2 0.77 4.18 2. 60 1.53 22.16 3.36 227.0 233.5 2473.6 1.18 4.25 2. 45 1.75 20.83 3.84 228.0 234.5 2483.0 1.49 4.43 2. 42 1.96 20.61 4.31 229.0 235.5 2492.4 1.58 4.92 2. 99 1.86 25.48 4.09 230.0 236.5 2501.8 1.10 4.96 3.06 1.83 0.63 26.04 4.03 3.38 66.55 231.0 237.5 2511.1 0.82 4.59 2. 77 1.76 23.63 3.87 232.0 238.5 2520.5 1.42 4.52 2. 66 1.80 22.65 3.96 233.0 239.5 2529.9 0.91 4.51 2. 64 1.81 22.51 3.99 234.0 240.5 2539.3 0.94 4.45 2. 41 1.99 20.49 4.38 235.0 241.5 2548.7 2.08 4.08 2.10 1.94 0.60 17.84 4.26 3.21 74.69 236.0 242.5 2558.1 0.96 4.10 2. 02 2.04 17.22 4.48 237.0 243.5 2567.5 1.26 4.13 2. 30 1.77 19.58 3.90 238.0 244.5 2576.8 1.85 4.58 2. 76 1.76 23.48 3.88 239.0 245.5 2586.2 1.31 4.89 3. 09 1.74 26.25 3.83 240.0 246.5 2595.6 0.96 4.70 2.95 1.69 0.58 25.12 3.71 3.11 68.06 241.0 247.5 2605.0 1.07 4.89 3. 23 1.59 27.50 3.51 242.0 248.5 2606.1 0.09 4.79 3. 37 1.42 28.68 3.12 243.0 249.5 2607.2 0.09 4.51 3. 07 1.44 26.11 3.17 244.0 250.5 2608.3 0.12 4.37 3. 06 1.32 26.01 2.90 245.0 251.5 2609.4 0.10 4.80 3.40 1.41 0.51 28.90 3.10 2.74 65.26 246.0 252.5 2610.5 0.11 5.00 3. 53 1.47 30.00 3.24 247.0 253.5 2611.6 0.10 4.91 3. 43 1.48 29.15 3.27 248.0 254.5 2612.7 0.11 4.88 3. 40 1.48 28.92 3.26 249.0 255.5 2613.8 0.10 5.09 3. 54 1.55 30.10 3.42 250.0 256.5 2614.9 0.09 5.37 3.82 1.54 0.50 32.54 3.40 2.69 61.37 251.0 257.5 2616.0 0.10 5.57 4. 03 1.54 34.30 3.38 252.0 258.5 2617.1 0.10 5.94 4. 31 1.63 36.67 3.58 253.0 259.5 2618.2 0.10 6.20 4. 41 1.78 37.54 3.92 254.0 260.5 2619.3 0.12 5.79 4. 33 1.46 36.45 3.21 255.0 261.5 2620.4 0.12 6.05 4.47 1.59 0.27 37.62 3.49 1.45 57.43 256.0 262.5 2621.5 0.12 5.88 4. 19 1.69 35.28 3.72 257.0 263.5 2622.6 0.13 5.81 4. 17 1.64 35.15 3.60 258.0 264.5 2623.7 0.12 6.07 4. 43 1.64 37.29 3.61 259.0 265.5 2624.8 0.15 6.46 4. 72 1.74 39.79 3.82 260.0 266.5 2625.9 0.11 6.92 5.18 1.75 0.48 43.60 3.84 2.57 50.00

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56 Table B-1. Continued. Depth in Core (cm) Composite Depth in Core (cm) Age (cal yr BP) TN TC TICTOCTS CaCO3 (%) OM (%) CaSO4 ·2H2O (%) Clay (%) 261.0 267.5 2627.0 0.12 7.06 5. 38 1.67 45.33 3.68 262.0 268.5 2628.1 0.12 7.07 5. 46 1.61 45.96 3.55 263.0 269.5 2629.2 0.11 6.58 5. 12 1.46 43.13 3.21 264.0 270.5 2630.3 0.14 6.86 5. 07 1.78 42.73 3.92 265.0 271.5 2631.4 0.12 6.95 5.16 1.79 0.27 43.46 3.94 1.45 51.14 266.0 272.5 2632.5 0.12 7.01 5. 19 1.83 43.68 4.02 267.0 273.5 2633.6 0.14 6.74 5. 00 1.74 42.14 3.83 268.0 274.5 2634.7 0.12 6.44 4. 67 1.78 39.31 3.91 269.0 275.5 2635.8 0.12 6.39 4. 62 1.77 38.93 3.89 270.0 276.5 2636.9 0.17 7.93 4.39 3.54 0.58 36.97 7.80 3.12 52.11 271.0 277.5 2638.0 0.12 5.71 4. 39 1.32 36.96 2.91 272.0 278.5 2639.1 0.13 6.67 4. 70 1.98 39.55 4.35 273.0 279.5 2640.2 0.14 6.59 4. 57 2.03 38.48 4.46 274.0 280.5 2641.3 0.13 6.16 4. 09 2.07 34.67 4.55 275.0 281.5 2642.4 0.14 5.85 3.88 1.97 0.58 32.85 4.33 3.09 59.73 276.0 282.5 2643.5 0.13 5.71 3. 62 2.09 30.69 4.60 277.0 283.5 2644.6 0.13 5.73 3. 68 2.05 31.18 4.50 278.0 284.5 2645.7 0.13 5.69 3. 72 1.97 31.51 4.33 279.0 285.5 2646.8 0.12 5.47 3. 49 1.98 29.57 4.36 280.0 286.5 2647.9 0.14 5.27 3.74 1.53 0.66 31.64 3.37 3.53 61.46 281.0 287.5 2649.0 0.13 5.57 3. 68 1.89 31.19 4.15 282.0 288.5 2650.1 0.14 5.85 4. 04 1.81 34.21 3.98 283.0 289.5 2651.2 0.09 6.06 4. 54 1.52 38.44 3.35 284.0 290.5 2652.3 0.11 6.00 4. 43 1.58 37.51 3.47 285.0 291.5 2653.4 0.12 5.75 4.05 1.70 0.45 34.29 3.74 2.40 59.57 286.0 292.5 2654.5 0.11 5.27 3. 65 1.62 30.96 3.55 287.0 293.5 2655.6 0.14 5.62 3. 79 1.83 32.11 4.02 288.0 294.5 2656.7 0.12 5.43 3. 63 1.81 30.73 3.97 289.0 295.5 2657.8 0.12 4.84 3. 10 1.75 26.22 3.84 290.0 296.5 2658.9 0.11 4.63 2.86 1.77 0.67 24.27 3.89 3.60 68.25 291.0 297.5 2660.0 0.11 4.00 2. 30 1.70 19.50 3.74 292.0 298.5 2673.8 0.14 4.87 2. 89 1.98 24.51 4.36 293.0 299.5 2687.7 0.13 5.00 3. 22 1.78 27.28 3.91 294.0 300.5 2701.5 0.15 5.34 3. 59 1.75 30.25 3.86 295.0 301.5 2715.4 0.14 5.64 3.82 1.82 0.51 32.21 4.01 2.72 61.06 296.0 302.5 2729.2 0.16 5.65 3. 73 1.92 31.46 4.22 297.0 303.5 2743.0 0.15 5.69 3. 64 2.05 30.68 4.51 298.0 304.5 2756.9 0.16 5.94 3. 90 2.04 32.85 4.48 299.0 305.5 2770.7 0.14 5.95 4. 01 1.94 33.80 4.26 300.0 306.5 2784.6 0.16 5.33 2.71 2.62 0.59 22.80 5.77 3.18 68.25 301.0 307.5 2798.4 0.20 4.86 2. 82 2.03 23.79 4.48 302.0 308.5 2812.2 0.19 4.61 2. 41 2.20 20.33 4.84

PAGE 68

57 Table B-1 Continued. Depth in Core (cm) Composite Depth in Core (cm) Age (cal yr BP) TN TC TICTOCTS CaCO3 (%) OM (%) CaSO4 ·2H2O (%) Clay (%) 303.0 309.5 2826.1 0.18 4.50 2. 17 2.33 18.28 5.13 304.0 310.5 2839.9 0.18 4.63 2. 09 2.53 17.62 5.57 305.0 311.5 2853.8 0.18 4.72 2.21 2.50 0.59 18.64 5.51 3.15 72.70 306.0 312.5 2867.6 0.16 4.47 2. 39 2.08 20.12 4.58 307.0 313.5 2881.4 0.17 4.74 2. 74 2.01 23.04 4.41 308.0 314.5 2895.3 0.20 6.75 2. 97 3.78 25.03 8.32 309.0 315.5 2909.1 0.11 3.73 3. 08 0.65 25.95 1.42 310.0 316.5 2922.9 0.16 4.71 2.67 2.05 0.59 22.45 4.50 3.18 69.87 311.0 317.5 2936.8 0.17 5.06 2. 73 2.33 23.04 5.12 312.0 318.5 2950.6 0.18 5.26 3. 00 2.25 25.29 4.96 313.0 319.5 2964.5 0.18 5.10 2. 76 2.34 23.23 5.15 314.0 320.5 2978.3 0.19 5.36 2. 81 2.55 23.69 5.61 315.0 321.5 2992.1 0.23 5.58 2.47 3.10 0.75 20.89 6.82 4.04 68.25 316.0 322.5 3006.0 0.21 5.48 2. 31 3.17 19.52 6.97 317.0 323.5 3019.8 0.18 6.29 3. 51 2.78 29.66 6.11 318.0 324.5 3033.7 0.20 6.30 3. 90 2.40 32.96 5.27 319.0 325.5 3047.5 0.17 7.46 5. 15 2.31 43.53 5.08 320.0 326.5 3061.3 0.17 7.71 5.55 2.16 0.83 46.89 4.76 4.47 43.88 321.0 327.5 3075.2 0.13 8.00 5. 53 2.47 46.73 5.42 322.0 328.5 3089.0 0.18 8.27 5. 45 2.82 46.06 6.20 323.0 329.5 3102.9 0.17 8.23 5. 52 2.71 46.66 5.96 324.0 330.5 3116.7 0.17 8.38 5. 69 2.68 48.09 5.90 325.0 331.5 3130.5 0.18 8.34 5.65 2.69 0.42 47.72 5.92 2.25 44.10 326.0 332.5 3144.4 0.16 8.26 5. 52 2.75 46.60 6.04 327.0 333.5 3158.2 0.17 8.31 5. 45 2.86 46.01 6.30 328.0 334.5 3172.1 0.17 8.64 5. 59 3.05 47.18 6.72 329.0 335.5 3185.9 0.15 8.55 5. 70 2.85 48.15 6.27 330.0 336.5 3199.7 0.15 8.37 5.37 3.00 0.49 45.35 6.60 2.62 45.43 331.0 337.5 3213.6 0.17 8.10 5. 39 2.71 45.53 5.96 332.0 338.5 3227.4 0.19 7.95 5. 19 2.76 43.80 6.07 333.0 339.5 3241.3 0.16 8.06 5. 38 2.69 45.43 5.91 334.0 340.5 3255.1 0.17 8.14 5. 57 2.57 47.03 5.65 335.0 341.5 3268.9 0.16 8.36 5.64 2.72 0.42 47.63 5.99 2.25 44.14 336.0 342.5 3282.8 0.19 8.54 5. 77 2.77 48.50 6.09 337.0 343.5 3296.6 0.69 5.82 48.96 0.00 338.0 344.5 3310.4 0.17 8.74 5. 83 2.91 49.03 6.40 339.0 345.5 3324.3 0.17 8.53 5. 74 2.78 48.30 6.12 340.0 346.5 3338.1 0.16 8.28 5.59 2.69 0.84 47.61 5.91 4.51 41.97 341.0 347.5 3352.0 0.16 8.22 5. 97 2.25 50.20 4.94 342.0 348.5 3365.8 0.18 8.55 5. 83 2.72 49.03 5.98 343.0 349.5 3379.6 0.16 8.37 5. 72 2.66 48.06 5.85 344.0 350.5 3393.5 0.16 8.40 5. 74 2.66 48.30 5.85

PAGE 69

58 Table B-1 Continued. Depth in Core (cm) Composite Depth in Core (cm) Age (cal yr BP) TN TC TICTOCTS CaCO3 (%) OM (%) CaSO4 ·2H2O (%) Clay (%) 345.0 351.5 3407.3 0.17 8.39 5.71 2.68 0.50 48.03 5.89 2.71 43.37 346.0 352.5 3421.2 0.17 8.39 5. 73 2.66 48.22 5.85 347.0 353.5 3435.0 0.18 8.83 6. 08 2.74 51.14 6.04 348.0 354.5 3462.8 0.18 8.44 5. 90 2.54 49.58 5.59 349.0 355.5 3490.6 0.20 8.04 5. 65 2.39 47.53 5.25 350.0 356.5 3518.4 0.16 7.84 5.40 2.44 0.49 45.44 5.36 2.66 46.54 351.0 357.5 3546.3 0.15 7.87 5. 67 2.20 47.65 4.85 352.0 358.5 3574.1 0.15 8.19 5. 73 2.46 48.21 5.40 353.0 359.5 3601.9 0.16 7.92 5. 31 2.61 44.67 5.74 354.0 360.5 3629.7 0.17 8.23 5. 38 2.85 45.21 6.27 355.0 361.5 3657.5 0.19 8.15 5.15 2.99 0.58 43.34 6.58 3.12 46.97 356.0 362.5 3685.3 0.20 7.79 4. 87 2.92 40.93 6.43 357.0 363.5 3713.1 0.20 7.92 4. 84 3.08 40.90 6.78 358.0 364.5 3740.9 0.18 7.57 4. 68 2.88 39.61 6.34 359.0 365.5 3768.8 0.20 7.37 4. 37 3.00 36.92 6.60 360.0 366.5 3796.6 0.20 7.38 4.14 3.24 0.56 35.00 7.12 3.00 54.88 361.0 367.5 3824.4 0.22 7.06 3. 64 3.42 30.81 7.53 362.0 368.5 3852.2 0.20 7.47 4. 31 3.16 36.47 6.94 363.0 369.5 3880.0 0.18 7.89 4. 78 3.11 40.42 6.84 364.0 370.5 3921.0 0.20 7.84 4. 47 3.38 37.77 7.43 365.0 371.5 3961.9 0.19 7.46 4.38 3.09 0.71 37.01 6.79 3.84 52.35 366.0 372.5 4002.9 0.17 7.06 4. 31 2.74 36.48 6.04 367.0 373.5 4043.8 0.18 6.86 4. 09 2.76 34.62 6.08 368.0 374.5 4084.8 0.18 7.04 4. 38 2.66 37.05 5.85 369.0 375.5 4125.8 0.20 7.45 4. 36 3.10 36.86 6.81 370.0 376.5 4166.7 0.25 7.70 3.92 3.78 0.66 33.14 8.31 3.55 54.99 371.0 377.5 4207.7 0.24 7.61 3. 59 4.03 30.33 8.86 372.0 378.5 4248.7 0.21 7.63 4. 08 3.56 34.46 7.83 373.0 379.5 4289.6 0.24 7.58 3. 92 3.66 33.17 8.05 374.0 380.5 4330.6 0.29 7.01 2. 45 4.56 20.73 10.04 375.0 381.5 4371.5 0.27 7.45 2.99 4.46 1.28 25.29 9.81 6.91 57.99 376.0 382.5 4412.5 0.27 7.42 2. 89 4.53 24.45 9.97 377.0 383.5 4453.5 0.27 7.77 3. 33 4.44 28.18 9.76 378.0 384.5 4494.4 0.29 8.25 3. 33 4.91 28.18 10.81 379.0 385.5 4535.4 0.32 8.08 3. 09 4.99 26.11 10.98 380.0 386.5 4576.3 0.29 7.46 2.91 4.55 0.82 24.62 10.01 4.43 60.95 381.0 387.5 4617.3 0.30 7.80 2. 55 5.25 21.56 11.54 382.0 388.5 4658.3 0.34 8.21 2. 36 5.85 19.95 12.86 383.0 389.5 4699.2 0.37 8.58 2. 31 6.27 19.53 13.80 384.0 390.5 4740.2 0.38 8.58 2. 21 6.37 18.66 14.01 385.0 391.5 4781.2 0.27 7.57 2.71 4.85 0.95 22.95 10.68 5.10 61.27 386.0 392.5 4822.1 0.26 7.80 3. 17 4.63 26.80 10.19

PAGE 70

59 Table B-1. Continued. Depth in Core (cm) Composite Depth in Core (cm) Age (cal yr BP) TN TC TICTOCTS CaCO3 (%) OM (%) CaSO4 ·2H2O (%) Clay (%) 387.0 393.5 4863.1 0.31 7.47 2. 19 5.27 18.54 11.60 388.0 394.5 4904.0 0.33 7.53 2. 02 5.51 17.24 12.12 389.0 395.5 4945.0 0.32 8.61 2. 86 5.76 24.33 12.67 390.0 396.5 4986.0 0.35 7.67 1.54 6.12 1.02 13.14 13.47 5.50 67.89 391.0 397.5 5026.9 0.32 7.35 1. 68 5.67 14.33 12.48 392.0 398.5 5067.9 0.26 6.95 2. 29 4.66 19.52 10.26 393.0 399.5 5108.8 0.26 6.96 2. 58 4.39 21.96 9.65 394.0 400.5 5149.8 0.27 6.99 2. 01 4.98 17.13 10.96 395.0 401.5 5190.8 0.28 6.61 1.63 4.98 0.81 13.87 10.95 4.33 70.84 396.0 402.5 5231.7 0.27 6.96 2. 06 4.90 17.53 10.79 397.0 403.5 5272.7 0.32 7.34 1. 73 5.61 14.74 12.34 398.0 404.5 5313.7 0.31 7.01 2. 03 4.98 17.25 10.95 399.0 405.5 5354.6 0.30 6.86 2. 05 4.82 17.36 10.60 400.0 406.5 5395.6 0.28 6.85 2.23 4.62 1.06 18.88 10.17 5.72 65.23 401.0 407.5 5436.5 0.29 6.95 2. 18 4.77 18.51 10.49 402.0 408.5 5477.5 0.31 7.69 2. 67 5.02 22.63 11.05 403.0 409.5 5518.5 0.26 7.55 3. 29 4.27 27.87 9.38 404.0 410.5 5559.4 0.27 7.01 2. 67 4.35 22.63 9.56 405.0 411.5 5600.4 0.29 7.39 2.33 5.07 0.95 19.72 11.15 5.09 64.04 406.0 412.5 5641.3 0.28 7.28 2. 57 4.71 21.81 10.36 407.0 413.5 5682.3 0.26 7.24 2. 93 4.31 24.87 9.48 408.0 414.5 5723.3 0.24 7.51 3. 49 4.02 29.61 8.84 409.0 415.5 5764.2 0.27 7.55 2. 82 4.72 23.95 10.39 410.0 416.5 5805.2 0.29 7.28 2.90 4.38 0.93 24.57 9.65 5.02 60.76 411.0 417.5 5846.2 0.27 7.33 2. 97 4.37 25.16 9.61 412.0 418.5 5887.1 0.28 7.04 2. 29 4.76 19.38 10.46 413.0 419.5 5928.1 0.27 7.15 2. 71 4.43 23.00 9.76 414.0 420.5 5969.0 0.29 7.24 2. 39 4.85 20.28 10.67 415.0 421.5 6010.0 0.33 7.31 1.89 5.43 0.97 16.00 11.94 5.22 66.84 416.0 422.5 6051.0 0.31 7.04 1. 61 5.43 13.65 11.95 417.0 423.5 6091.9 0.32 6.76 1. 76 5.00 14.92 11.01 418.0 424.5 6132.9 0.29 6.81 2. 26 4.55 19.20 10.00 419.0 425.5 6173.8 0.33 7.57 2. 04 5.53 17.29 12.16 420.0 426.5 6214.8 0.41 8.03 1.37 6.66 1.31 11.61 14.65 7.03 66.70 421.0 427.5 6255.8 0.36 7.96 1. 87 6.10 15.82 13.41 422.0 428.5 6296.7 0.30 7.71 2. 60 5.11 22.01 11.25 423.0 429.5 6337.7 0.31 8.04 2. 41 5.62 20.45 12.37 424.0 430.5 6378.7 0.40 8.29 1. 60 6.69 13.59 14.71 425-3 431.5 6419.6 0.37 8.64 2. 01 6.64 17.01 14.60 425-4 432.5 6460.6 0.36 8.52 2.66 5.86 1.09 22.56 12.89 5.87 58.68 426.0 433.5 6501.5 0.37 8.56 1.84 6.72 1.23 15.59 14.77 6.60 63.03 427.0 434.5 6542.5 0.38 8.38 1.77 6.61 1.15 15.03 14.53 6.19 64.25

PAGE 71

60 Table B-1. Continued. Depth in Core (cm) Composite Depth in Core (cm) Age (cal yr BP) TN TC TICTOCTS CaCO3 (%) OM (%) CaSO4 ·2H2O (%) Clay (%) 428.0 435.5 6583.5 0.36 8.02 1.57 6.45 1.24 13.33 14.18 6.65 65.85 429.0 436.5 6624.4 0.41 8.80 1.81 6.98 1.23 15.37 15.36 6.64 62.63 430.0 437.5 6665.4 0.37 8.55 2.01 6.54 1.21 17.02 14.40 6.54 62.04 431.0 438.5 6706.3 0.28 7.73 2.89 4.84 0.93 24.51 10.65 5.02 59.82 432.0 439.5 6747.3 0.33 8.44 2.94 5.50 0.97 24.92 12.11 5.23 57.74 433.0 440.5 6788.3 0.37 8.49 1.73 6.76 1.15 14.66 14.87 6.20 64.27 434.0 441.5 6829.2 0.49 9.16 0.61 8.54 1.36 5.19 18.80 7.34 68.68 435.0 442.5 6870.2 0.43 7.91 0.70 7.21 1.22 5.94 15.87 6.58 71.62 436.0 443.5 6911.2 0.43 7.98 0.88 7.09 1.29 7.48 15.61 6.93 69.98 437.0 444.5 6952.1 0.36 6.76 0.66 6.10 1.43 5.60 13.42 7.70 73.28 438.0 445.5 6993.1 0.45 8.74 0. 87 7.87 7.37 17.32 439.0 446.5 7034.0 0.44 8.75 1.07 7.68 1.34 9.06 16.90 7.21 66.82 440.0 447.5 7075.0 0.42 8.35 1.67 6.68 1.14 14.09 14.70 6.16 65.05 441.0 448.5 7099.7 0.37 8.33 2.27 6.06 1.18 19.11 13.34 6.33 61.23 442.0 449.5 7124.4 0.46 9.27 1.43 7.84 1.24 12.09 17.25 6.66 64.01 443.0 450.5 7149.1 0.48 9.71 1.36 8.35 1.36 11.48 18.37 7.31 62.84 444.0 451.5 7173.8 0.54 9.98 1.14 8.84 1.40 9.61 19.45 7.52 63.42 445.0 452.5 7198.4 0.49 9.63 1.22 8.41 1.27 10.28 18.50 6.85 64.37 446.0 453.5 7223.1 0.45 8.70 1.01 7.69 1.42 8.53 16.91 7.63 66.92 447.0 454.5 7247.8 0.45 8.76 0.90 7.85 1.37 7.60 17.28 7.37 67.75 448.0 455.5 7272.5 0.46 9.58 1.16 8.43 1.36 9.74 18.54 7.30 64.42 449.0 456.5 7297.2 0.50 9.29 1.08 8.21 1.40 9.13 18.05 7.55 65.27 450.0 457.5 7321.9 0.46 8.48 0.96 7.52 1.25 8.09 16.55 6.74 68.62 451.0 458.5 7346.6 0.44 8.02 0.81 7.21 1.33 6.84 15.85 7.16 70.14 452.0 459.5 7371.3 0.38 7.50 0.80 6.70 1.41 6.74 14.75 7.57 70.94 453.0 460.5 7395.9 0.38 7.31 0.80 6.51 1.35 6.73 14.33 7.27 71.67 454.0 461.5 7420.6 0.42 7.88 0.82 7.06 1.63 6.95 15.52 8.76 68.76 455.0 462.5 7445.3 0.38 6.99 0.90 6.09 1.59 7.55 13.40 8.56 70.50 456.0 463.5 7470.0 0.31 6.23 1.05 5.18 1.55 8.85 11.39 8.33 71.43 457.0 464.5 7518.1 0.37 6.95 1.20 5.75 1.58 10.07 12.66 8.49 68.78 458.0 465.5 7566.2 0.39 7.72 1.32 6.40 1.69 11.10 14.09 9.09 65.73 459.0 466.5 7614.2 0.48 9.28 1.06 8.22 1.68 8.96 18.08 9.05 63.92 460.0 467.5 7662.3 0.43 8.43 1.06 7.37 1.78 8.97 16.21 9.56 65.26 461.0 468.5 7710.4 0.35 7.36 1.14 6.22 1.59 9.58 13.68 8.56 68.18 462.0 469.5 7758.5 0.30 6.61 2.24 4.36 1.32 18.89 9.60 7.08 64.43 463.0 470.5 7806.5 0.31 7.54 2.82 4.73 1.29 23.75 10.40 6.93 58.92 464.0 471.5 7854.6 0.39 7.95 1.67 6.28 1.57 14.11 13.82 8.44 63.64 465.0 472.5 7902.7 0.32 7.64 2.41 5.23 1.63 20.31 11.50 8.77 59.42 466.0 473.5 7950.8 0.33 7.32 2.13 5.19 1.60 17.93 11.43 8.63 62.02 467.0 474.5 7998.8 0.31 7.86 2.83 5.02 1.41 23.88 11.05 7.56 57.51 468.0 475.5 8046.9 0.35 8.63 2.70 5.93 1.45 22.78 13.04 7.80 56.38 469.0 476.5 8095.0 0.35 8.94 3.16 5.78 1.59 26.63 12.72 8.55 52.10

PAGE 72

61 Table B-1. Continued. Depth in Core (cm) Composite Depth in Core (cm) Age (cal yr BP) TN TC TICTOCTS CaCO3 (%) OM (%) CaSO4 ·2H2O (%) Clay (%) 470.0 477.5 8143.1 0.51 11.602.71 8.89 1.82 22.84 19.55 9.80 47.81 471.0 478.5 8191.2 0.47 11.242.08 9.16 1.71 17.53 20.16 9.22 53.10 472.0 479.5 8239.2 0.41 10.022.40 7.62 1.71 20.23 16.77 9.22 53.77 473.0 480.5 8287.3 0.41 9.98 1.85 8.13 1.75 15.61 17.88 9.43 57.08 474.0 481.5 8335.4 0.47 11.392.15 9.25 2.13 18.09 20.34 11.47 50.10 475.0 482.5 8383.5 0.44 10.772.46 8.31 1.80 20.73 18.28 9.69 51.30 476.0 483.5 8431.5 0.42 9.81 2.79 7.03 1.63 23.50 15.46 8.76 52.28 477.0 484.5 8479.6 0.43 9.80 2.93 6.87 1.67 24.71 15.12 8.97 51.20 478.0 485.5 8527.7 0.39 10.253.36 6.89 1.60 28.31 15.15 8.60 47.93 479.0 486.5 8575.8 0.46 11.143.17 7.97 1.83 26.69 17.54 9.85 45.92 480.0 487.5 8623.8 0.43 10.873.20 7.67 1.65 26.95 16.88 8.89 47.28 481.0 488.5 8671.9 0.37 9.79 3.44 6.35 1.43 29.01 13.98 7.70 49.32 482.0 489.5 8720.0 0.37 9.79 3.22 6.57 1.79 27.16 14.46 9.65 48.73 483.0 490.5 8772.0 0.38 9.39 3.18 6.21 1.58 26.77 13.66 8.48 51.09 484.0 491.5 8824.0 0.32 8.72 3.59 5.13 1.18 30.40 11.29 6.34 51.97 485.0 492.5 8876.0 0.34 9.25 3.65 5.60 1.46 30.96 12.33 7.84 48.87 486.0 493.5 8928.0 0.33 9.26 3.66 5.61 1.54 31.00 12.34 8.28 48.38 487.0 494.5 8980.0 0.38 9.56 3.48 6.08 1.44 29.51 13.37 7.74 49.38 488.0 495.5 9032.0 0.37 9.54 3.41 6.13 1.52 28.91 13.48 8.18 49.42 489.0 496.5 9084.0 0.29 8.79 3.72 5.07 1.34 31.51 11.15 7.22 50.11 490.0 497.5 9136.0 0.35 9.44 3.78 5.66 1.43 32.07 12.45 7.71 47.77 491.0 498.5 9188.0 0.34 9.42 3.67 5.75 1.51 31.13 12.65 8.13 48.08 492.0 499.5 9240.0 0.36 9.86 3.46 6.40 1.48 29.34 14.09 7.94 48.63 493.0 500.5 9292.0 0.37 10.043.38 6.66 1.63 28.64 14.65 8.74 47.97 494.0 501.5 9344.0 0.35 9.69 3.54 6.16 1.60 29.98 13.55 8.61 47.86 495.0 502.5 9396.0 0.30 9.26 3.88 5.38 1.26 32.92 11.84 6.76 48.48 496.0 503.5 9448.0 0.27 8.94 3.38 5.56 1.45 28.66 12.24 7.82 51.29 497.0 504.5 9500.0 0.36 9.54 3.77 5.76 1.60 31.99 12.68 8.62 46.71 498.0 505.5 9530.9 0.37 9.41 3.87 5.54 1.47 32.79 12.20 7.91 47.11 499.0 506.5 9561.9 0.33 9.10 3.59 5.51 1.45 30.47 12.11 7.82 49.59 500.0 507.5 9592.8 0.35 9.19 3. 59 5.60 30.43 12.32 501.0 508.5 9623.7 0.36 9.94 3.60 6.34 1.70 30.57 13.95 9.12 46.36 502.0 509.5 9654.7 0.39 10.463.51 6.95 2.16 29.76 15.28 11.60 43.36 503.0 510.5 9685.6 0.37 9.97 3.84 6.13 1.73 32.57 13.48 9.32 44.64 504.0 511.5 9716.5 0.35 9.63 3.70 5.94 1.74 31.34 13.06 9.39 46.21 505.0 512.5 9747.4 0.38 11.054.44 6.61 1.76 37.68 14.54 9.47 38.32 506.0 513.5 9778.4 0.40 12.735.06 7.67 1.58 42.90 16.87 8.50 31.73 507.0 514.5 9809.3 0.34 11.325.68 5.64 1.67 47.88 12.40 8.97 30.75 508.0 515.5 9840.2 0.33 10.955.62 5.33 1.44 47.36 11.73 7.77 33.13 509.0 516.5 9871.2 0.30 9.78 5.22 4.56 1.49 43.97 10.03 8.03 37.97 510.0 517.5 9902.1 0.32 10.255.05 5.21 1.36 42.53 11.45 7.31 38.71 511.0 518.5 9933.0 0.37 12.456.17 6.29 1.55 51.97 13.83 8.33 25.87

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62 Table B-1. Continued. Depth in Core (cm) Composite Depth in Core (cm) Age (cal yr BP) TN TC TICTOCTS CaCO3 (%) OM (%) CaSO4 ·2H2O (%) Clay (%) 512.0 519.5 9964.0 0.32 11.855.94 5.92 1.04 50.03 13.02 5.60 31.35 513.0 520.5 9994.9 0.39 12.185.69 6.50 1.42 47.93 14.29 7.62 30.15 514.0 521.5 10025.8 0.39 12.835.77 7.07 1.58 48.62 15.54 8.49 27.35 515.0 522.5 10056.7 0.41 12.865.92 6.94 1.65 49.89 15.27 8.86 25.99 516.0 523.5 10087.7 0.38 12.835.80 7.03 1.66 48.91 15.46 8.96 26.68 517.0 524.5 10118.6 0.38 11.905.53 6.36 1.30 46.65 14.00 6.98 32.36 518.0 525.5 10149.5 0.36 12.515.99 6.52 1.13 50.50 14.35 6.07 29.08 519.0 526.5 10180.5 0.21 7.45 6.44 1.02 1.29 54.25 2.24 6.93 36.59 520.0 527.5 10211.4 0.35 12.356.49 5.86 1.24 54.68 12.89 6.67 25.76 521.0 528.5 10242.3 0.34 12.306.53 5.77 1.06 55.08 12.69 5.71 26.53 522.0 529.5 10273.3 0.31 12.076.63 5.45 1.43 55.85 11.99 7.69 24.48 523.0 530.5 10304.2 0.29 12.137.07 5.06 1.01 59.63 11.13 5.43 23.82 524.0 531.5 10335.1 0.29 12.136.97 5.16 1.00 58.77 11.34 5.38 24.50 525.0 532.5 10366.0 0.25 9.70 5.91 3.79 1.66 49.85 8.33 8.90 32.91 526.0 533.5 10397.0 0.12 5.92 3.55 2.37 6.46 29.95 5.21 34.73 30.11 527.0 534.5 10427.9 0.10 4.30 2.27 2.03 4.39 19.13 4.47 23.61 52.79 528.0 535.5 10458.8 0.12 4.68 2.91 1.77 3.31 24.55 3.89 17.79 53.77 529.0 536.5 10489.8 0.17 7.86 6.55 1.30 3.60 55.24 2.87 19.38 22.50 530.0 537.5 10520.7 0.18 10.107.05 3.05 0.57 59.23 6.71 3.08 30.98 531.0 538.5 10551.6 0.16 10.577.43 3.14 2.51 62.48 6.91 13.53 17.08 532.0 539.5 10582.6 0.13 7.08 5.01 2.07 3.73 42.12 4.54 20.08 33.25 533.0 540.5 10613.5 0.12 6.16 3.34 2.82 9.11 28.05 6.21 49.00 16.74 534.0 541.5 10644.4 0.00 1.80 1.17 0.62 11.149.90 1.37 59.95 28.78 535.0 542.5 10675.3 0.06 1.97 1.78 0.19 13.3914.93 0.41 72.05 12.60 536.0 543.5 10706.3 0.08 3.65 2.19 1.45 8.60 18.45 3.19 46.24 32.12 537.0 544.5 10737.2 0.12 4.42 3.43 0.99 5.85 28.85 2.17 31.48 37.50 538.0 545.5 10768.1 0.22 8.38 3.69 4.69 6.28 30.97 10.32 33.81 24.90 539.0 546.5 10799.1 0.12 4.17 2.34 1.82 8.08 19.71 4.01 43.45 32.83 540.0 547.5 10830.0 0.07 2.09 1.10 0.98 13.599.27 2.17 73.14 15.43 541.0 548.5 10867.0 0.09 2.70 1.32 1.38 10.4111.07 3.04 56.01 29.88 542.0 549.5 10904.0 0.09 3.05 1.70 1.35 11.2714.28 2.97 60.61 22.15 543.0 550.5 10941.0 0.15 5.67 3.59 2.09 5.16 30.16 4.59 27.75 37.50 544.0 551.5 10978.0 0.24 9.38 4.98 4.40 5.96 41.87 9.67 32.05 16.41 545.0 552.5 11015.0 0.20 6.48 3.26 3.21 6.81 27.44 7.07 36.65 28.84 546.0 553.5 11052.0 0.11 3.33 1.79 1.53 10.8315.07 3.37 58.27 23.29 547.0 554.5 11089.0 0.07 1.90 1.10 0.80 13.009.21 1.76 69.94 19.09 548.0 555.5 11126.0 0.10 2.57 1.21 1.37 11.3810.15 3.01 61.22 25.63 549.0 556.5 11163.0 0.08 1.92 0.76 1.16 12.326.36 2.55 66.26 24.83 550.0 557.5 11200.0 0.10 1.74 0.80 0.94 12.956.75 2.06 69.69 21.49

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63 Table B-2. Elemental geochemistry data for Core PI 8-VI-02 11A-MWI retrieved from 58.2 m modern (2002) water de pth at 17.000ºN and 89.779ºW. Depth in MWI (cm) TC TIC TOC CaCO3 (%) OM (%) 0.0 13.39 2.38 11.01 19.80 24.23 1.0 13.47 2.47 11.00 20.56 24.21 2.0 13.38 2.59 10.79 21.58 23.74 3.0 12.81 2.66 10.15 22.17 22.33 4.0 12.99 2.71 10.28 22.59 22.61 5.0 12.37 3.05 9.32 25.39 20.51 6.0 12.42 3.15 9.27 26.23 20.40 7.0 12.57 3.14 9.43 26.15 20.75 8.0 12.51 2.80 9.71 23.35 21.36 9.0 12.17 2.86 9.31 23.86 20.47 10.0 11.84 3.29 8.55 27.42 18.81 11.0 11.72 3.39 8.33 28.26 18.32 12.0 11.69 3.29 8.40 27.42 18.48 13.0 11.73 3.30 8.43 27.50 18.55 14.0 11.42 3.02 8.40 25.16 18.48 15.0 11.42 2.86 8.56 23.81 18.84 16.0 11.53 2.97 8.56 24.74 18.83 17.0 11.18 3.15 8.03 26.26 17.66 18.0 11.03 3.16 7.87 26.35 17.31 19.0 11.01 3.37 7.64 28.04 16.82 20.0 10.94 3.47 7.47 28.89 16.44 21.0 10.92 3.16 7.76 26.35 17.07 22.0 10.89 2.85 8.04 23.72 17.70 23.0 10.81 2.65 8.16 22.11 17.94 24.0 10.33 2.44 7.89 20.33 17.36 25.0 10.51 2.47 8.04 20.59 17.69 26.0 10.37 2.34 8.03 19.49 17.67 27.0 10.05 2.42 7.63 20.16 16.79 28.0 10.38 2.79 7.59 23.21 16.71 29.0 10.52 2.58 7.94 21.52 17.46 30.0 10.44 2.62 7.82 21.86 17.20 31.0 10.77 2.94 7.83 24.49 17.23 32.0 10.75 2.95 7.80 24.57 17.16 33.0 10.86 2.99 7.87 24.91 17.32 34.0 11.09 3.18 7.91 26.52 17.40 35.0 10.79 3.44 7.35 28.64 16.18 36.0 10.43 3.01 7.42 25.08 16.33 37.0 10.33 2.82 7.51 23.48 16.53 38.0 10.23 2.75 7.48 22.89 16.46 39.0 10.36 3.04 7.32 25.34 16.10 40.0 10.11 2.30 7.81 19.17 17.18 41.0 10.01 1.72 8.29 14.36 18.23 42.0 9.37 1.37 8.00 11.40 17.60 43.0 9.63 1.54 8.09 12.84 17.80 44.0 8.95 1.70 7.25 14.19 15.94

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64 Table B-2. Continued. Depth in MWI (cm) TC TIC TOC CaCO3 (%) OM (%) 45.0 8.70 2.20 6.50 18.33 14.30 46.0 8.00 2.94 5.06 24.49 11.13 47.0 8.04 2.92 5.12 24.32 11.27 48.0 7.82 2.85 4.97 23.73 10.94 49.0 7.45 2.99 4.46 24.92 9.81 50.0 7.74 3.53 4.21 29.39 9.27 51.0 7.74 3.82 3.92 31.84 8.62 52.0 7.89 4.50 3.39 37.50 7.46 53.0 7.75 4.79 2.96 39.95 6.50 54.0 7.80 4.37 3.43 36.40 7.55 55.0 7.73 4.92 2.81 40.96 6.19 Table B-3. Elemental geochemistry data for Core PI 8-VI-02 11B retrieved from 51.6 m modern (2002) water dept h at 16.998ºN and 89.779ºW. Depth in Core (cm) TIC TS CaCO3 (%) CaSO4 ·2H2O (%) 15.0 3.69 0.64 30.79 3.45 20.0 3.85 0.63 32.05 3.41 25.0 3.40 0.57 28.30 3.06 30.0 2.63 0.59 21.90 3.19 35.0 3.27 0.57 27.24 3.06 40.0 5.66 0.43 47.19 2.29 45.0 5.76 0.44 47.98 2.34 50.0 5.34 0.42 44.48 2.27 55.0 4.14 0.49 34.46 2.65 60.0 5.24 0.40 43.63 2.15 65.0 3.35 0.38 27.91 2.04 70.0 3.41 0.14 28.45 0.74 75.0 5.90 0.30 49.18 1.63 80.0 5.93 0.36 49.43 1.91 85.0 4.28 0.34 35.68 1.81 90.0 4.79 0.44 39.95 2.38 95.0 4.98 0.40 41.51 2.15 100.0 5.04 0.32 42.02 1.74 105.0 3.77 0.54 31.42 2.92 110.0 2.94 0.37 24.50 1.97 115.0 4.77 0.34 39.75 1.84 120.0 4.16 0.36 34.63 1.96 125.0 3.91 0.32 32.59 1.70 130.0 3.92 0.35 32.68 1.89 135.0 3.38 0.40 28.21 2.13 140.0 2.76 0.40 22.97 2.15 145.0 3.07 0.39 25.61 2.09 150.0 3.29 0.32 27.41 1.70

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65 Table B-3. Continued. Depth in Core (cm) TIC TS CaCO3 (%) CaSO4 ·2H2O (%) 155.0 2.29 0.41 19.08 2.22 160.0 2.02 0.38 16.82 2.03 165.0 2.16 0.29 17.98 1.58 170.0 2.16 0.30 18.01 1.63 175.0 1.80 0.31 15.02 1.67 180.0 2.63 0.27 21.94 1.45 185.0 2.34 0.33 19.53 1.79 190.0 3.30 0.33 27.52 1.75 195.0 3.52 0.26 29.31 1.40 200.0 2.80 0.33 23.33 1.76 205.0 3.39 0.27 28.22 1.47 210.0 3.47 0.25 28.92 1.34 215.0 4.11 0.23 34.22 1.22 220.0 4.54 0.21 37.84 1.11 225.0 5.27 0.46 43.96 2.45 230.0 4.28 0.39 35.67 2.07 235.0 4.17 0.26 34.78 1.41 240.0 2.67 0.27 22.25 1.44 245.0 3.21 0.40 26.74 2.16 250.0 3.66 0.30 30.51 1.60 255.0 5.43 0.26 45.23 1.41 260.0 6.12 0.29 51.00 1.57 265.0 5.46 0.56 45.51 3.02 270.0 6.48 0.50 53.97 2.67 275.0 6.18 0.45 51.48 2.42 280.0 5.64 0.42 47.03 2.27 285.0 5.27 0.48 43.93 2.60 290.0 4.33 0.54 36.08 2.93 295.0 4.75 0.46 39.56 2.49 300.0 4.16 0.46 34.66 2.48 305.0 3.56 0.55 29.68 2.97 310.0 2.17 0.69 18.09 3.70 315.0 2.33 0.66 19.38 3.56 320.0 0.96 0.64 7.96 3.42 325.0 2.28 0.65 18.99 3.48 330.0 1.22 0.64 10.18 3.42 335.0 0.99 0.62 8.25 3.32 340.0 0.83 0.71 6.88 3.81 345.0 1.39 0.63 11.57 3.38 350.0 1.00 0.70 8.31 3.76 355.0 1.30 0.62 10.82 3.36 360.0 1.55 0.57 12.90 3.08 365.0 0.99 0.42 8.23 2.23

PAGE 77

66 Table B-3. Continued. Depth in Core (cm) TIC TS CaCO3 (%) CaSO4 ·2H2O (%) 370.0 0.81 0.72 6.72 3.85 375.0 1.04 0.59 8.67 3.17 380.0 0.82 0.05 6.83 0.26 385.0 1.65 0.37 13.78 1.98 390.0 0.57 0.69 4.76 3.70 395.0 0.83 0.61 6.89 3.27 400.0 0.86 0.63 7.18 3.40 405.0 0.57 0.53 4.79 2.83 410.0 0.37 0.56 3.07 3.01 415.0 0.57 0.50 4.72 2.68 420.0 0.59 0.54 4.90 2.91 425.0 0.69 0.53 5.76 2.87 430.0 1.76 0.43 14.64 2.34 435.0 2.55 0.43 21.28 2.32 440.0 2.50 0.56 20.87 3.04 445.0 2.83 0.51 23.62 2.72 450.0 3.10 0.53 25.83 2.87 455.0 3.50 0.34 29.18 1.83 460.0 3.74 0.41 31.17 2.20 465.0 3.70 0.37 30.82 1.98 470.0 4.02 0.50 33.47 2.67 475.0 5.91 0.51 49.24 2.76 480.0 6.80 0.40 56.66 2.13 485.0 5.87 0.49 48.90 2.63 490.0 6.65 0.34 55.42 1.82 495.0 2.87 2.82 23.90 15.14 500.0 5.52 0.94 45.98 5.05 505.0 1.59 2.92 13.28 15.68 510.0 1.11 6.67 9.22 35.84 Table B-4. Elemental geochemistry data for Core PI 9-VI-02 11C retrieved from 30.0 m modern (2002) water dept h at 16.991ºN and 89.780ºW. Depth in Core (cm) Composite in Depth (cm) TC TIC TOC TS CaCO3 (%) OM (%) CaSO4 ·2H2O (%) 0.0 25.0 5.25 4.04 1. 21 0.57 33.71 2.65 3.09 1.0 26.0 4.84 4.01 0.83 33.46 1.82 2.0 27.0 4.42 3.68 0.74 30.67 1.63 3.0 28.0 4.84 4.07 0.77 33.88 1.70 4.0 29.0 5.06 4.33 0.73 36.07 1.61 5.0 30.0 4.68 3.42 1. 26 0.53 28.47 2.78 2.85 6.0 31.0 4.06 3.03 1.03 25.26 2.26 7.0 32.0 4.10 3.06 1.04 25.51 2.28 8.0 33.0 3.47 2.68 0.79 22.30 1.75

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67 Table B-4. Continued. Depth in Core (cm) Composite in Depth (cm) TC TIC TOC TS CaCO3 (%) OM (%) CaSO4 ·2H2O (%) 10.0 35.0 3.80 2.68 1. 12 0.47 22.30 2.47 2.55 11.0 36.0 3.41 2.51 0.90 20.95 1.97 12.0 37.0 3.79 2.81 0.98 23.40 2.16 13.0 38.0 3.72 2.88 0.84 23.99 1.85 14.0 39.0 4.44 3.19 1.25 26.61 2.74 15.0 40.0 4.53 3.19 1. 34 0.55 26.61 2.94 2.97 16.0 41.0 4.48 3.44 1.04 28.64 2.30 17.0 42.0 5.07 4.10 0.97 34.13 2.14 18.0 43.0 5.62 4.69 0.93 39.12 2.04 19.0 44.0 5.13 4.19 0.94 34.89 2.07 20.0 45.0 4.90 3.53 1. 37 0.55 29.40 3.02 2.96 21.0 46.0 4.79 3.81 0.98 31.77 2.15 22.0 47.0 4.90 3.72 1.18 31.01 2.59 23.0 48.0 4.60 3.82 0.78 31.85 1.71 24.0 49.0 5.18 4.15 1.03 34.55 2.27 25.0 50.0 5.02 4.23 0. 79 0.44 35.23 1.74 2.34 26.0 51.0 5.99 5.14 0.85 42.83 1.87 27.0 52.0 6.37 5.37 1.00 44.79 2.19 28.0 53.0 6.51 5.48 1.03 45.70 2.26 29.0 54.0 7.45 6.24 1.21 52.03 2.65 30.0 55.0 7.52 6.23 1. 29 0.43 51.95 2.83 2.29 31.0 56.0 6.91 5.46 1.45 45.46 3.20 32.0 57.0 6.90 5.55 1.35 46.22 2.98 33.0 58.0 6.18 5.21 0.97 43.44 2.13 34.0 59.0 5.64 4.84 0.80 40.33 1.76 35.0 60.0 5.80 4.66 1. 14 0.50 38.82 2.51 2.66 36.0 61.0 6.46 5.03 1.43 41.93 3.14 37.0 62.0 5.84 4.63 1.21 38.56 2.67 38.0 63.0 5.60 4.24 1.36 35.37 2.98 39.0 64.0 6.25 4.67 1.58 38.90 3.48 40.0 65.0 6.78 5.21 1. 57 0.63 43.42 3.45 3.40 41.0 66.0 8.97 7.10 1.87 59.19 4.11 42.0 67.0 8.79 7.30 1.49 60.87 3.27 43.0 68.0 9.11 7.56 1.55 62.98 3.42 44.0 69.0 10.20 9.05 1.15 75.44 2.52 45.0 70.0 10.40 8.86 1. 54 0.20 73.85 3.38 1.06 46.0 71.0 10.51 8.95 1.56 74.59 3.43 47.0 72.0 11.37 8.97 2.40 74.78 5.27 48.0 73.0 10.67 9.20 1.47 76.70 3.23 49.0 74.0 9.93 8.27 1.66 68.95 3.64 50.0 75.0 10.50 8.94 1. 56 0.19 74.51 3.43 1.00 51.0 76.0 9.93 7.23 2.70 60.28 5.93 52.0 77.0 10.53 8.03 2.50 66.93 5.50 53.0 78.0 9.74 7.20 2.54 60.03 5.58

PAGE 79

68 Table B-4. Continued. Depth in Core (cm) Composite in Depth (cm) TC TIC TOC TS CaCO3 (%) OM (%) CaSO4 ·2H2O (%) 55.0 80.0 9.92 4.47 5. 45 0.64 37.25 11.99 3.43 56.0 81.0 8.87 2.60 6.27 21.63 13.80 57.0 82.0 8.61 1.51 7.10 12.55 15.63 58.0 83.0 8.95 0.90 8.05 7.46 17.72 59.0 84.0 9.71 0.97 8.74 8.05 19.24 60.0 85.0 10.89 3.07 7. 82 1.10 25.60 17.20 5.89 61.0 86.0 10.57 6.75 3.82 56.21 8.41 62.0 87.0 8.77 5.77 3.00 48.06 6.61 63.0 88.0 7.57 0.86 6.71 7.21 14.75 64.0 89.0 8.11 0.80 7.31 6.70 16.07 65.0 90.0 7.52 0.91 6. 61 1.05 7.60 14.54 5.66 66.0 91.0 6.85 0.75 6.10 6.27 13.41 67.0 92.0 5.98 0.62 5.36 5.17 11.79 68.0 93.0 6.64 0.82 5.82 6.87 12.79 69.0 94.0 7.14 0.71 6.43 5.93 14.14 70.0 95.0 8.76 0.76 8. 00 1.19 6.34 17.60 6.40 71.0 96.0 8.92 0.57 8.35 4.75 18.37 72.0 97.0 8.62 0.63 7.99 5.26 17.58 73.0 98.0 8.24 0.67 7.57 5.60 16.65 74.0 99.0 8.51 1.67 6.84 13.90 15.05 75.0 100.0 9.18 1.57 7. 61 1.16 13.09 16.74 6.22 76.0 101.0 8.76 1.00 7.76 8.36 17.06 77.0 102.0 8.97 0.99 7.98 8.28 17.55 78.0 103.0 8.19 1.08 7.11 9.04 15.63 79.0 104.0 8.33 1.62 6.71 13.52 14.76 80.0 105.0 8.73 1.92 6.81 15.97 14.99 81.0 106.0 9.53 2.54 6. 99 1.04 21.20 15.37 5.62 82.0 107.0 9.90 4.36 5.54 36.32 12.19 83.0 108.0 11.62 8.00 3.62 66.67 7.96 84.0 109.0 11.78 9.24 2.54 77.02 5.58 85.0 110.0 11.64 10.24 1.40 85.35 3.07 86.0 111.0 11.64 10.03 1. 61 0.31 83.59 3.54 1.64 87.0 112.0 11.10 6.24 4.86 52.02 10.69 88.0 113.0 10.08 4.39 5.69 36.62 12.51 89.0 114.0 10.36 4.46 5.90 37.21 12.97 90.0 115.0 10.80 4.41 6.39 36.78 14.05 91.0 116.0 10.36 4.23 6. 13 0.78 35.27 13.48 4.20 92.0 117.0 10.52 7.37 3.15 61.45 6.92 93.0 118.0 9.51 4.86 4.65 40.49 10.23 94.0 119.0 9.32 5.70 3.62 47.47 7.97 95.0 120.0 11.15 9.74 1.41 81.14 3.11 96.0 121.0 11.46 10.54 0. 92 0.10 87.79 2.03 0.51 97.0 122.0 12.09 10.74 1.35 89.48 2.98 98.0 123.0 12.23 10.62 1.61 88.47 3.55

PAGE 80

69 Table B-4. Continued. Depth in Core (cm) Composite in Depth (cm) TC TIC TOC TS CaCO3 (%) OM (%) CaSO4 ·2H2O (%) 100.0 125.0 11.96 10.13 1.83 84.43 4.02 101.0 126.0 12.14 10.65 1.49 88.72 3.29 102.0 127.0 11.98 11.07 0.91 92.26 2.00 103.0 128.0 11.88 11.25 0.63 93.77 1.38 104.0 129.0 11.95 11.10 0.85 92.51 1.87 105.0 130.0 11.93 10.42 1.51 86.87 3.31 106.0 131.0 11.47 10.16 1. 31 0.23 84.64 2.89 1.24 107.0 132.0 11.67 10.18 1.49 84.80 3.29 108.0 133.0 11.20 9.79 1.41 81.54 3.11 109.0 134.0 11.98 10.54 1.44 87.81 3.17 110.0 135.0 12.08 10.58 1.50 88.15 3.30 111.0 136.0 12.08 10.58 1. 50 0.19 88.17 3.30 1.05 112.0 137.0 12.23 10.64 1.59 88.65 3.50 113.0 138.0 11.99 10.73 1.26 89.40 2.78 114.0 139.0 12.09 10.96 1.13 91.33 2.49 115.0 140.0 12.07 10.99 1.08 91.58 2.38 116.0 141.0 12.08 10.66 1. 42 0.21 88.82 3.13 1.11 117.0 142.0 12.03 10.79 1.24 89.91 2.73 118.0 143.0 11.97 10.68 1.29 88.99 2.84 119.0 144.0 11.98 10.94 1.04 91.16 2.29 120.0 145.0 11.79 10.74 1.05 89.49 2.31 121.0 146.0 11.44 10.69 0. 75 0.19 89.07 1.65 1.01 122.0 147.0 11.70 10.82 0.88 90.16 1.94 123.0 148.0 11.28 10.57 0.71 88.07 1.57 124.0 149.0 11.45 10.58 0.87 88.15 1.92 125.0 150.0 11.80 10.37 1.43 86.39 3.15 126.0 151.0 11.60 10.25 1. 35 0.21 85.39 2.98 1.11 127.0 152.0 11.78 10.35 1.43 86.23 3.15 128.0 153.0 12.20 10.52 1.68 87.65 3.70 129.0 154.0 12.10 10.37 1.73 86.45 3.80 130.0 155.0 12.31 10.74 1.57 89.47 3.46 131.0 156.0 12.42 10.77 1. 65 0.17 89.72 3.64 0.91 132.0 157.0 12.51 10.22 2.29 85.16 5.04 133.0 158.0 12.32 10.40 1.92 86.68 4.22 134.0 159.0 12.56 10.37 2.19 86.45 4.81 135.0 160.0 12.12 10.51 1.61 87.57 3.54 136.0 161.0 11.74 10.67 1. 07 0.19 88.95 2.35 1.03 137.0 162.0 11.62 10.22 1.40 85.16 3.08 138.0 163.0 11.65 9.89 1. 76 0.16 82.41 3.87 0.86 139.0 164.0 11.55 9.71 1.84 80.95 4.04 140.0 165.0 11.15 9.26 1. 89 0.17 77.16 4.16 0.93 141.0 166.0 10.55 8.30 2.25 69.16 4.95 142.0 167.0 10.50 8.32 2.18 69.34 4.80 143.0 168.0 9.68 8.50 1.18 70.80 2.61

PAGE 81

70 Table B-4. Continued. Depth in Core (cm) Composite in Depth (cm) TC TIC TOC TS CaCO3 (%) OM (%) CaSO4 ·2H2O (%) 145.0 170.0 9.65 8.19 1.46 68.22 3.22 146.0 171.0 10.11 8.50 1.61 70.80 3.55 147.0 172.0 9.77 8.20 1.57 68.30 3.46 148.0 173.0 9.74 8.55 1.19 71.23 2.62 149.0 174.0 9.66 8.36 1.30 69.68 2.86 150.0 175.0 9.78 8.27 1. 51 0.15 68.91 3.32 0.81 151.0 176.0 9.45 8.46 0. 99 0.13 70.54 2.17 0.68 156.0 181.0 9.14 8.62 0. 52 0.10 71.80 1.15 0.56 161.0 186.0 9.54 8.74 0. 80 0.13 72.82 1.76 0.70 166.0 191.0 9.47 8.87 0.60 73.92 1.32 171.0 196.0 9.59 9.03 0.56 75.27 1.23 176.0 201.0 9.37 8.95 0.42 74.59 0.92 181.0 206.0 9.71 9.09 0.62 75.77 1.36 186.0 211.0 9.59 9.15 0.44 76.28 0.96 188.0 213.0 9.28 77.32 191.0 216.0 9.74 9.30 0.44 77.46 0.98 196.0 221.0 10.37 10.09 0.28 84.12 0.61 201.0 226.0 10.38 10.09 0.29 84.05 0.65 206.0 231.0 10.52 10.26 0.26 85.49 0.57 211.0 236.0 9.32 6.91 2.41 57.61 5.29 216.0 241.0 8.53 8.50 0.03 70.87 0.06 221.0 246.0 7.61 7.33 0.28 61.08 0.62 226.0 251.0 6.80 6.41 0.39 53.39 0.87 231.0 256.0 7.91 7.90 0.01 65.81 0.03 236.0 261.0 6.20 5.99 0.21 49.92 0.46 240.0 265.0 6.10 50.83 241.0 266.0 6.00 5.96 0.04 49.67 0.09 246.0 271.0 4.53 3.99 0.54 33.28 1.18 251.0 276.0 3.17 3.04 0.13 25.34 0.28 256.0 281.0 3.81 3.64 0.17 30.33 0.38 261.0 286.0 4.38 4.26 0.12 35.48 0.27 266.0 291.0 3.58 3.39 0.19 28.21 0.43 271.0 296.0 3.33 3.39 28.23 275.0 300.0 3.47 2.71 0.76 22.55 1.68 Table B-5. Elemental geochemistry data for Core PI 9-VI-02 11C-MWI retrieved from 30.0 m modern (2002) water de pth at 16.991ºN and 89.780ºW. Depth in MWI (cm) TC TIC TOC CaCO3 (%) OM (%) 0.0 15.24 5.73 9.51 47.77 20.92 1.0 15.20 5.74 9.46 47.85 20.81 2.0 15.30 6.22 9.08 51.85 19.97 3.0 14.73 6.40 8.33 53.35 18.32

PAGE 82

71 Table B-5. Continued. Depth in MWI (cm) TC TIC TOC CaCO3 (%) OM (%) 5.0 14.15 6.72 7.43 56.02 16.34 6.0 13.64 7.33 6.31 61.11 13.88 7.0 13.46 7.58 5.88 63.19 12.93 8.0 13.39 7.53 5.86 62.78 12.89 9.0 13.02 7.78 5.24 64.86 11.52 10.0 12.91 8.08 4.83 67.36 10.62 11.0 12.62 7.73 4.89 64.44 10.75 12.0 12.39 7.72 4.67 64.36 10.27 13.0 12.08 8.11 3.97 67.61 8.73 14.0 12.14 7.47 4.67 62.27 10.27 15.0 12.08 7.76 4.32 64.69 9.50 16.0 12.02 7.88 4.14 65.69 9.10 17.0 12.29 8.26 4.03 68.86 8.86 18.0 12.32 8.10 4.22 67.53 9.28 19.0 12.50 8.10 4.40 67.53 9.67 20.0 12.33 8.38 3.95 69.85 8.69 21.0 12.07 7.97 4.10 66.38 9.03 22.0 12.04 7.75 4.29 64.59 9.44 23.0 12.07 7.98 4.09 66.53 8.99 24.0 12.06 7.75 4.31 64.59 9.48 25.0 11.87 7.73 4.14 64.42 9.11 26.0 12.04 7.48 4.56 62.31 10.04 27.0 12.15 7.03 5.12 58.60 11.26 28.0 11.91 6.65 5.26 55.39 11.58 29.0 11.71 5.97 5.74 49.73 12.63 30.0 11.61 4.95 6.66 41.29 14.64 31.0 10.55 4.77 5.78 39.77 12.71 32.0 9.96 5.58 4.38 46.52 9.63 33.0 9.26 5.48 3.78 45.68 8.31 34.0 8.97 5.44 3.53 45.34 7.76 35.0 9.04 6.12 2.92 51.00 6.42 36.0 7.86 6.10 1.76 50.83 3.87 37.0 8.14 6.30 1.84 52.52 4.04 38.0 6.64 5.46 1.18 45.51 2.59 39.0 6.10 5.42 0.68 45.17 1.49 40.0 6.57 5.25 1.32 43.74 2.91 41.0 5.75 4.50 1.25 37.49 2.75 42.0 5.49 4.32 1.17 35.97 2.58 43.0 5.62 4.47 1.15 37.24 2.53 44.0 5.06 4.44 0.62 36.98 1.37 45.0 6.52 5.24 1.28 43.65 2.82 46.0 5.52 4.57 0.95 38.08 2.09 47.0 5.10 3.96 1.14 33.00 2.51 48.0 5.48 4.44 1.04 36.98 2.29

PAGE 83

72 Table B-5. Continued. Depth in MWI (cm) TC TIC TOC CaCO3 (%) OM (%) 50.0 6.81 5.44 1.37 45.35 3.01 51.0 7.67 6.38 1.29 53.14 2.85 52.0 8.21 6.96 1.25 57.96 2.76 53.0 7.74 6.56 1.18 54.66 2.60 54.0 7.92 6.55 1.37 54.58 3.02 Table B-6. Elemental geochemistry data for Core PI 6-VI-02 11D retrieved from 20.9 m modern (2002) water dept h at 16.988ºN and 89.779ºW. Depth in Core (cm) TC TIC TOC TS CaCO3 (%) OM (%) CaSO4 ·2H2O (%) 10.0 12.79 9.87 2.92 0.46 82.22 6.43 2.48 15.0 12.68 10.59 2.09 0.14 88.27 4.60 0.74 20.0 11.85 9.10 2.75 0.30 75.86 6.05 1.63 25.0 12.38 8.51 3.86 0.10 70.96 8.50 0.53 30.0 12.25 8.79 3.46 0.27 73.26 7.61 1.46 35.0 12.22 10.71 1.51 89.28 3.31 40.0 12.00 9.38 2.63 0.27 78.13 5.78 1.44 45.0 12.51 9.35 3.16 0.33 77.89 6.96 1.77 50.0 12.12 8.94 3.19 74.46 7.02 55.0 12.13 10.24 1.89 0.16 85.33 4.15 0.85 60.0 12.54 10.39 2.15 0.18 86.59 4.73 0.94 65.0 12.13 8.27 3.86 0.19 68.89 8.49 1.00 70.0 11.90 7.73 4.17 0.34 64.41 9.17 1.82 75.0 11.17 7.40 3.77 0.21 61.69 8.29 1.11 80.0 9.82 6.79 3.04 0.06 56.55 6.68 0.30 85.0 8.85 8.05 0.79 0.14 67.12 1.74 0.78 90.0 8.98 8.29 0.69 0.14 69.07 1.52 0.74 95.0 9.19 6.73 2.46 56.10 5.41 100.0 9.27 8.34 0.93 0.13 69.47 2.06 0.69 105.0 9.42 8.46 0.96 70.51 2.11 110.0 9.57 8.27 1.30 68.95 2.86 115.0 9.18 7.51 1.67 62.58 3.67 120.0 9.70 9.17 0.54 76.38 1.18 125.0 9.19 9.19 0.00 76.62 0.00 130.0 8.65 8.39 0.26 69.93 0.58 135.0 9.22 8.88 0.34 73.97 0.75 140.0 9.47 8.99 0.48 74.91 1.07 145.0 9.26 9.28 0.00 77.35 0.00 150.0 7.90 7.62 0.28 63.50 0.63 155.0 8.72 8.60 0.12 71.67 0.26 160.0 8.39 8.00 0.39 66.69 0.85 165.0 9.03 8.90 0.13 74.18 0.28 170.0 8.69 8.45 0.25 70.39 0.54 175.0 9.76 9.56 0.20 79.69 0.43 180.0 7.53 7.33 0.20 61.07 0.44

PAGE 84

73 Table B-6. Continued. Depth in Core (cm) TC TIC TOC TS CaCO3 (%) OM (%) CaSO4 ·2H2O (%) 185.0 8.34 8.11 0.23 67.60 0.50 195.0 7.44 7.20 0.24 59.97 0.53 200.0 6.59 6.40 0.19 53.32 0.42 205.0 5.13 42.76 Table B-7. Elemental geochemistry data for Core PI 8-VI-02 11E retrieved from 9.7 m modern (2002) water dept h at 16.984ºN and 89.779ºW. Depth in Core (cm) TC TIC TOC TS CaCO3 (%) OM (%) CaSO4 •2H2O (%) 30.0 11.23 9.77 1.46 81.42 3.21 35.0 11.86 9.72 2.14 0.05 80.98 4.71 0.27 40.0 12.81 9.36 3.45 0.06 78.02 7.58 0.33 45.0 12.92 9.42 3.50 78.53 7.69 50.0 12.71 9.62 3.09 80.13 6.81 55.0 12.79 9.60 3.19 79.97 7.03 60.0 13.03 9.83 3.20 81.91 7.04 65.0 12.33 9.83 2.50 0.03 81.91 5.50 0.17 70.0 12.96 9.05 3.91 75.41 8.60 75.0 12.73 7.85 4.88 0.04 65.44 10.73 0.22 80.0 13.17 9.27 3.90 77.26 8.58 85.0 12.65 10.41 2.24 86.72 4.94 90.0 13.17 9.84 3.33 81.99 7.33 95.0 13.14 9.78 3.36 81.49 7.40 100.0 12.30 9.43 2.87 78.61 6.31 105.0 12.28 9.03 3.25 75.24 7.15 110.0 12.02 8.79 3.23 73.25 7.11 115.0 12.12 9.40 2.72 78.36 5.98 120.0 12.08 10.52 1.56 87.65 3.44 125.0 12.21 10.02 2.19 83.51 4.81 130.0 12.41 9.36 3.05 0.07 78.02 6.70 0.36 135.0 12.36 9.65 2.71 0.07 80.39 5.97 0.39 140.0 11.80 9.94 1.86 82.84 4.09 145.0 12.26 9.53 2.73 79.45 6.00 150.0 12.44 10.12 2.32 84.31 5.11 155.0 11.71 9.49 2.22 79.11 4.88 160.0 11.79 9.75 2.04 0.11 81.21 4.50 0.60 165.0 6.01 3.75 2.26 31.26 4.97 170.0 3.97 3.02 0.95 0.06 25.14 2.10 0.33 175.0 4.27 3.13 1.14 26.06 2.51 180.0 3.87 3.56 0.31 0.28 29.67 0.68 1.51 185.0 3.95 3.55 0.40 0.26 29.58 0.88 1.39 190.0 4.39 3.82 0.57 0.30 31.85 1.25 1.60 195.0 4.90 4.47 0.43 0.32 37.21 0.96 1.69 200.0 5.35 5.04 0.31 0.23 41.99 0.69 1.25

PAGE 85

74 Table B-7. Continued. Depth in Core (cm) TC TIC TOC TS CaCO3 (%) OM (%) CaSO4 •2H2O (%) 205.0 5.66 5.01 0.65 41.74 1.43 215.0 4.61 4.23 0.38 35.28 0.83 220.0 4.48 4.07 0.41 33.94 0.90 225.0 4.62 4.38 0.24 36.54 0.52 230.0 4.51 4.10 0.41 34.19 0.89 235.0 4.46 3.76 0.70 31.34 1.54 240.0 4.50 4.31 0.19 35.95 0.41 245.0 3.63 4.04 33.69 250.0 3.63 3.28 0.35 27.32 0.77

PAGE 86

75 APPENDIX C ISOTOPIC DATA FROM CORE 11A Appendix C provides tabular and graphical isotopic data measured on both bulk sediment and the ostracod Limnocythere sp. from Core 11A (Table C-1; Figure C-1; Figure C-2). Samples were measured for the ratios of 13C-to-12C and 18O-to-16O and are expressed in standard delta ( ) notation relative to the VPDB standard. Bulk sediment isotopic compositi on was measured on a VG Prism II mass spectrometer. Samples were analyzed at 20-cm intervals over the en tire length of Core 11A with the exception of the basal 75 cm, which were analyzed at 1-cm intervals. Ostracod carapaces of Limnocythere sp. were picked at 1-cm intervals from the base of Core 11A at 558 cm to 490 cm, a bove which ostracod abundance dropped to zero. Ostracod aggregates of 15-20 cleaned valves from each 1-cm sample were measured on a ThermoFinnigan 252 mass spectrometer coupled to a ThermoFinnigan Kiel III automated preparation system (see also Chapter 2). Table C-1. Isotopic data from Core PI 8VI-02 11A retrieved at 58.2 m modern (2002) water depth at 17.000ºN and 89.779ºW. Depth in Core (cm) Composite Depth in Core (cm) Calibrated Age (cal yr BP) Bulk Carbonate 13C (‰) Bulk Carbonate 18O (‰) Ostracod 18O (‰) Ostracod 13C (‰) 55 61.5 1492.3-3.58-2.10 70 76.5 1559.5-2.18-1.24 90 96.5 1649.0-1.50-0.58 91 97.5 1653.5-1.83-0.97 92 98.5 1658.0-1.53-0.94 93 99.5 1662.5-1.40-0.77 94 100.5 1667.0-1.29-0.80 95 101.5 1671.4-1.16-0.66 96 102.5 1675.9-0.68-0.32 97 103.5 1680.4-0.73-0.24

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76 Table C-1. Continued. Depth in Core (cm) Composite Depth in Core (cm) Calibrated Age (cal yr BP) Bulk Carbonate 13C (‰) Bulk Carbonate 18O (‰) Ostracod 18O (‰) Ostracod 13C (‰) 98 104.5 1684.9-0.78-0.37 99 105.5 1689.3-0.67-0.25 100 106.5 1693.8-0.89-0.38 101 107.5 1698.3-1.16-0.47 102 108.5 1702.8-1.38-0.56 103 109.5 1707.3-2.34-1.24 104 110.5 1711.7-1.91-0.83 110 116.5 1738.6-2.17-1.18 130 136.5 1828.2-2.49-1.04 150 156.5 1917.7-5.99-3.58 170 176.5 2007.3-3.28-1.99 190 196.5 2126.3-3.82-2.30 210 216.5 2314.0-3.03-1.58 230 236.5 2501.8-2.09-1.46 250 256.5 2614.9-2.04-1.12 270 276.5 2636.9-1.83-1.15 290 296.5 2658.9-1.93-1.10 310 316.5 2922.9-1.87-1.00 330 336.5 3199.7-2.81-1.57 350 356.5 3518.4-2.16-1.09 370 376.5 4166.7-3.18-1.44 390 396.5 4986.0-0.67-1.05 410 416.5 5805.2-0.46-1.11 431 437.5 6665.40.47-0.65 451 457.5 7321.90.47-1.75 470 476.5 8095.0-2.36-0.28 471 477.5 8143.1-3.60-0.56 472 478.5 8191.2-3.32-0.46 473 479.5 8239.2-3.90-0.63 474 480.5 8287.3-3.35-0.56 475 481.5 8335.4-2.85-0.50 476 482.5 8383.5-3.30-1.25 477 483.5 8431.5-3.95-1.29 478 484.5 8479.6-3.76-1.31 479 485.5 8527.7-4.19-1.31 480 486.5 8575.8-4.68-1.04 481 487.5 8623.8-4.79-1.33 482 488.5 8671.9-4.49-0.97 483 489.5 8720.0-4.10-1.29 484 490.5 8772.0-4.28-1.39 485 491.5 8824.0-4.61-1.383.05-6.34 486 492.5 8876.0-4.57-1.09 487 493.5 8928.0-4.40-1.19 488 494.5 8980.0-4.35-1.043.22-7.31 489 495.5 9032.0-4.39-1.13 490 496.5 9084.0-4.45-1.193.40-7.37

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77 Table C-1. Continued. Depth in Core (cm) Composite Depth in Core (cm) Calibrated Age (cal yr BP) Bulk Carbonate 13C (‰) Bulk Carbonate 18O (‰) Ostracod 18O (‰) Ostracod 13C (‰) 491 497.5 9136.0-4.21-0.99 492 498.5 9188.0-4.22-0.993.61-6.69 493 499.5 9240.0-4.08-0.96 494 500.5 9292.0-4.10-0.833.78-6.33 495 501.5 9344.0 3.40-6.79 496 502.5 9396.0 497 503.5 9448.0 3.52-6.76 498 504.5 9500.0-4.31-0.01 499 505.5 9530.9-5.570.173.57-8.77 500 506.5 9561.9-4.52-0.533.46-7.11 501 507.5 9592.8-4.16-0.36 502 508.5 9623.7-3.50-0.143.32-5.23 503 509.5 9654.7-3.29-0.183.42-5.50 504 510.5 9685.6-2.890.503.36-5.39 505 511.5 9716.5-3.59-0.383.43-5.76 506 512.5 9747.4-3.300.383.69-4.97 507 513.5 9778.4-3.731.043.48-5.18 508 514.5 9809.3-3.971.213.45-5.56 509 515.5 9840.2-3.611.023.69-5.81 510 516.5 9871.2-2.641.043.51-5.41 511 517.5 9902.1-2.691.393.68-5.07 512 518.5 9933.0-4.141.503.60-5.71 513 519.5 9964.0-3.761.293.62-5.84 514 520.5 9994.9-2.792.153.65-5.27 515 521.5 10025.8-2.841.553.73-4.58 516 522.5 10056.7-2.791.583.83-4.94 517 523.5 10087.7-2.811.423.86-6.25 518 524.5 10118.6-2.431.153.78-5.76 519 525.5 10149.5-2.851.503.61-4.39 520 526.5 10180.5-3.551.884.05-5.37 521 527.5 10211.4-3.821.964.02-5.77 522 528.5 10242.3-4.412.133.67-6.67 523 529.5 10273.3-4.791.843.53-6.18 524 530.5 10304.2-5.252.023.76-6.97 525 531.5 10335.1-5.151.913.81-7.36 526 532.5 10366.0-4.651.963.59-6.08 527 533.5 10397.0-6.022.293.43-7.67 528 534.5 10427.9-7.062.093.46-7.78 529 535.5 10458.8-7.351.903.30-8.73 530 536.5 10489.8-8.552.002.91-8.67 531 537.5 10520.7-8.911.913.04-8.60 532 538.5 10551.6-9.161.843.46-8.10 533 539.5 10582.6-10.141.773.61-8.14 534 540.5 10613.5-9.411.873.46-7.96 535 541.5 10644.4-7.572.023.82-6.91 536 542.5 10675.3-7.472.123.82-6.84

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78 Table C-1. Continued. Depth in Core (cm) Composite Depth in Core (cm) Calibrated Age (cal yr BP) Bulk Carbonate 13C (‰) Bulk Carbonate 18O (‰) Ostracod 18O (‰) Ostracod 13C (‰) 537 543.5 10706.3-6.212.113.69-7.04 538 544.5 10737.2-4.592.054.25-6.86 539 545.5 10768.1-3.512.213.81-6.00 540 546.5 10799.1-3.872.073.96-5.01 541 547.5 10830.0-4.962.054.07-5.83 542 548.5 10867.0-4.251.984.10-5.77 543 549.5 10904.0-3.662.134.38-5.31 544 550.5 10941.0-3.322.054.08-5.46 545 551.5 10978.0-2.931.893.75-3.88 546 552.5 11015.0-3.401.773.31-4.80 547 553.5 11052.0-4.641.75 548 554.5 11089.0-4.461.794.21-3.93 549 555.5 11126.0-4.681.754.72-3.89 550 556.5 11163.0-3.441.554.32-4.18 551 557.5 11200.0-3.332.01 -11 -9 -7 -5 -3 -9 -8 -7 -6 -5 -4 -3 48050052054056013C bulk carbonate (‰)13C ostracod (‰)Composite Depth in Core (cm) -2 -1 0 1 2 2.5 3 3.5 4 4.5 5 48050052054056018O bulk carbonate (‰)18O ostracod (‰)Composite Depth in Core (cm) LG/H Transition Figure C-1. Comparison of bulk carbonate with ostracod oxygen isotopic and carbon isotopic values. (A) oxygen isotopic ( 18O; ‰-VPDB) values of bulk carbonate (open circles) and ostrac ods (closed diamonds). (B) Carbon isotopic ( 13C; ‰-VPDB) values of bulk carbonate (open circles) and ostracods (closed diamonds). The La te Glacial/Holocene transition is highlighted in gray.

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79 APPENDIX D SCANNING X-RAY FLUORESCENCE PILOT STUDY Introduction In April 2004, a pilot study was conducted utilizing an X-Ray Fluorescence (XRF) Core Scanner to measure the chemical composition of sediments retrieved from Lake Petén Itzá. This study was undertaken to determine if the scanning XRF method was capable of producing high-resolution, elemental data from Petén Itzá sediments, thereby documenting compositional changes on sub-centennial scales. The XRF Core Scanner is housed at th e Ocean Drilling Program (ODP) Core Repository in Bremen, Germany and is manufactured by AVAA Tech (Figure D-2). Figure D-1. Pictures of the AVAA Tech XRF Core Scanner housed at the ODP Core Repository in Bremen, Germany. The XRF Core Scanner uses an x-ray source di rected onto the surface of a given medium causing excitation of the elements within the material. An x-ray detector measures the excitation as a function of time from the exci tation to the return to background levels. This generates an elemental spectrum that is statistically manipulated (i.e. processed) to

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80 obtain the abundance of each element in counts per second (cts). The XRF Core Scanner is capable of measuring a suite of elements with masses ranging from Aluminum (Al) to Barium (Ba), but not all elements in betwee n. During a given scan, however, it can only measure a smaller range due voltage limitations of the machine. This is because the x-ray strength, and therefore the excitation state of elements, are determined by the voltage applied to the source. For example, the XR F Core Scanner can only measure Al to Iron (Fe) when set at 10 kilovolts (kV), Potassium (K) to Strontium at 20 kV, and Yttrium (Y) to Ba at 50 kV. The XRF Core Scanner is also capable of measuring elemental composition of sediments at a variety of re solutions ranging from 0.1to 5.0-cm. Once again, this is limited by voltage constraints of th e machine in such a way that as voltage is increased, to detect heavier elements, re solution decreases due to x-ray excitation feedbacks (i.e. smearing of the signal over a gi ven area). These effects are variable and largely dependent upon the sediment lithologi c composition with fine-grained, carbonatepoor sediments providing the best results. Methods The XRF Core Scanner requires flat, horizon tal surfaces that are constant volume. Split cores are ideal but difficult to transpor t, therefore, Cores 11A-Section 4, 11B, and 11F were u-channeled and transported to Br emen, Germany. Prior to scanning, core surfaces were cleaned and covered with a clear polycarbonate foil to protect the instrument. Air bubbles between the foil a nd sediment surface were removed using a roller to reduce measurement error. A calib ration blank was run at the beginning and end of each day to quantify machine drift. Trial scans were conducted by varying vo ltage, amperage, and filter type to optimize measurement conditions. This proce ss consisted of four scans of Core 11A-

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81 Section 4 that resulted in an optimized configuration for 10 kV at 0.2-cm resolution when amperage was set at 1.0 mA (Table D-1). Table D-1. Log of trial scans used to optimize quality of data and resolution. Run Voltage (kV) Amperage (mA) Resolution (cm) 1 10 0.35 0.5 2 10 0.70 0.5 3 10 0.70 0.2 4 10 1.00 0.2 Data consisted of elemental composition of core material scanned at a variety of resolutions. Core 11A-Section 4 was scanne d at 10, 20, and 50 kV and at resolutions from 2.0to 0.2-cm. Both Cores 11B and 11F were scanned at 10 kV and 0.2-cm resolution for their entire lengths. The sediments lithology was a limiting factor, which precluded higher resolution (<0.2cm) analysis and elements above Fe were considered unimportant in this pilot study. Results Elemental data collected from Core 11A-Section 4 are the most detailed from all the cores scanned. At high re solution (2-mm)m the elements Aluminum (Al), Silica (Si), Phosphorus (P), Sulfur (S), Potassium (K), Calcium (Ca), Titanium (Ti), Manganese (Mn), and Iron (Fe) were measured. There is a strong correlati on between Ca data measured using the XRF Core Scanner and %CaCO3 measured using coulometric titration (Figure D-2). This suggests that the XRF Core Scanner may be capable of accurately measuring %CaCO3 at very high resolution in a non-destructive manner. This could be achieved using a re gression equation that relate s coulometrically measured carbonate values with XRF measured Ca content.

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82 0 10 20 30 40 50 60 70 0 10000 20000 30000 40000 50000 60000 70000 80000 420440460480500520540560CaCO3 (%)Calcium (cts)Depth in Core (cm) Figure D-2. Comparison of percent calcium carb onate (CaCO3, %; bold dashed line) with calcium (Ca, counts) measured using the XRF Core Scanner. Clay content was estimated by subtracti ng carbonate, gypsum, and organic matter content from 100%. The possibility, howev er, exists that the remainder may not completely reflect clay content, but may be clay plus other material. A good correlation between percent clay and elements associated with locally derived montmorillinite clays, such as Fe or Ti, would suggest that the re mainder of the bulk sediment, after subtraction of the other measured constituents, is indeed indicative of clay content and not clay plus other material. An excellent correlation betw een Ti and estimated clay content (Figure D-3) indicates that the initial assumption is va lid and that clay conten t is the remainder of the bulk sediment minus the other constituents . This suggests that the XRF Core Scanner is capable of producing hi gh-resolution records of Petén Itzá clay content 10 20 30 40 50 60 70 80 0 300 600 900 1200 1500 420440460480500520540560Clay (%)Titanium (cts)De p th in Core ( cm ) Figure D-3. Comparison of percent clay (Clay, %; bold dashed line) with titanium (Ti, counts) measured using the XRF Core Scanner.

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83 Data from the pilot study indicate that the XRF Core Scanner is capable of rapid, non-destructive analysis of Petén Itzá se diments. Providing a potentially powerful analytical tool for paleoclimatic and sedimentological studies.

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89 BIOGRAPHICAL SKETCH Michael Brendan Hillesheim was born to Dominic and Sandra Hillesheim on 10 November 1978 in Rochester, MN. He grew up in Dodge Center, MN where he graduated from Triton High School in June 1997. In Fall 1997, Michael enrolled at Michigan Technological University and subseq uently transferred to the University of Minnesota in August 1999. In May 2001, Michael graduated with a Bachelor of Science degree in geophysics. From graduation to August 2002, Michael worked as a Junior Research Scientist at the Limnological Research Center at the Univer sity of Minnesota. In Fall 2002, Michael enrolled at the University of Florid a in pursuit of a Master of Science degree in geology. Michael is currently seeking employment in the environmental consulting field.