Drill cores obtained from Lake Petén Itzá, Petén, Guatemala, contain a ∼85-kyr record of terrestrial climate from lowland Central America that was used to reconstruct hydrologic changes in the northern Neotropics during the last glaciation. Sediments are composed of alternating clay and gypsum reflecting relatively wet and dry climate conditions, respectively. From ∼85 to 48 ka, sediments were dominated by carbonate clay indicating moist conditions during Marine Isotope Stages (MIS) 5a, 4, and early 3. The first gypsum layer was deposited at ∼48 ka, signifying a shift toward drier hydrologic conditions and the onset of wet-dry oscillations. During the latter part of MIS 3, Petén climate varied between wetter conditions during interstadials and drier states during stadials. The pattern of clay-gypsum (wet-dry) oscillations during the latter part of MIS 3 (∼48-23 ka) closely resembles the temperature records from Greenland ice cores and North Atlantic marine sediment cores and precipitation proxies from the Cariaco Basin. The most arid periods coincided with Heinrich Events when cold sea surface temperatures prevailed in the North Atlantic, meridional overturning circulation was reduced, and the Intertropical Convergence Zone (ITCZ) was displaced southward. A thick clay unit was deposited from 23 to 18 ka suggesting deposition in a deep lake, and pollen accumulated during the same period indicates vegetation consisted of a temperate pine-oak forest. This finding contradicts previous inferences that climate was arid during the Last Glacial Maximum (LGM) chronozone (21±2 ka). At ∼18 ka, Petén climate switched from moist to arid conditions and remained dry from 18 to 14.7 ka during the early deglaciation. Moister conditions prevailed during the warmer Bolling-Allerod (14.7-12.8 ka) with the exception of a brief return to dry conditions at ∼13.8 ka that coincides with the Older Dryas and meltwater pulse 1A. The onset of the Younger Dryas at 12.8 ka marked the return of gypsum and hence dry conditions. The lake continued to precipitate gypsum until ∼10.3 ka when rainfall increased markedly in the early Holocene.
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We thank all individuals who participated in the field and laboratory work of the Lake Petén Itzá Scientific Drilling Project: Gabriela Alfaro, Jacobo Blijdenstein, Cornelia Brönnimann, Kristina Brady, Emmanuel Chapron, Erin Endsley, Christina Gallup, Valerie Gamble, Stephanie Girardclos, Robert Hofmann, Gerald Islebe, Jennifer Mays, Melisa Orozco, Anders Noren Liseth Perez, Silja Ramirez, and Florian Thévenon. We are also grateful to the numerous agencies and individuals in Guatemala who provided assistance to the project including: Universidad del Valle, Universidad San Carlos, Ministerio de Ambiente y Recursos Naturales, Consejo Nacional de Areas Protegidas, Instituto de Antropología e Historia, Autoridad Para el Manejo y Desarrollo Sostenible de la Cuenca del Lago Petén-Itzá, Wildlife Conservation Society, Alex Arrivillaga, Cathy Lopez, Margaret Dix, Michael Dix, Margarita Palmieri, David, Rosita, & Kelsey Kuhn, and the staff at La Casa de Don David, Lico Godoy, Tony Ortiz, Franz Sperisen, Luis Toruño, and Julian Tesucún. We also thank our many collaborators from University of Florida, University of Minnesota (Minneapolis/Duluth), Geoforschungszentrum (Potsdam), Swiss Federal Institute of Technology (Zurich), Université de Genève, as well as the personnel of DOSECC. The cores are archived at LacCore (National Lacustrine Core Repository), Department of Geology and Geophysics, University of Minnesota-Twin Cities and we thank Kristina Brady, Amy Myrbo and Anders Noren for their assistance in core description and curation. This project was funded by grants from the US National Science Foundation (ATM-0502030), the International Continental Scientific Drilling Program, the Swiss Federal Institute of Technology, and the Swiss National Science Foundation.
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