We applied a new method to reconstruct paleotemperature in the tropics during the last deglaciation by measuring oxygen isotopes of co-occurring gypsum hydration water and biogenic carbonate in sediment cores from two lakes on the Yucatan Peninsula. Oxygen and hydrogen isotope values of interstitial and gypsum hydration water indicate that the crystallization water preserves the isotopic signal of the lake water, and has not undergone post-depositional isotopic exchange with sediment pore water. The estimated lake water δ 18O is combined with carbonate δ 18O to calculate paleotemperature. Three paired measurements of 1200-yr-old gypsum and gastropod aragonite from Lake Chichancanab, Mexico, yielded a mean temperature of 26°C (range 23-29.5°C), which is consistent with the mean and range of mean annual temperatures (MAT) in the region today. Paired measurements of ostracods, gastropods, and gypsum hydration water samples were measured in cores from Lake Petén Itzá, Guatemala, spanning the Late Glacial and early Holocene period (18.5-10.4ka). The lowest recorded temperatures occurred at the start of Heinrich Stadial (HS) 1 at 18.5ka. Inferred temperatures from benthic ostracods ranged from 16 to 20°C during HS 1, which is 6-10°C cooler than MAT in the region today, whereas temperatures derived from shallow-water gastropods were generally warmer (20-25°C), reflecting epilimnetic temperatures. The derived temperatures support previous findings of greater tropical cooling on land in Central America during the Late Glacial than indicated by nearby marine records. Temperature increased in two steps during the last deglaciation. The first occurred during the Bolling-Allerod (B-A; from 14.7 to 13ka) when temperature rose to 20-24°C towards the end of this period. The second step occurred at 10.4ka near the beginning of the Holocene when ostracod-inferred temperature rose to 26°C, reflecting modern hypolimnetic temperature set during winter, whereas gastropod-derived temperature attained 30°C, reflecting modern summer epilimnetic temperature.
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We thank Associate Editor B. Luz, Y. Kolodny and two anonymous reviewers for their insightful comments that improved the quality of the manuscript. We thank the many agencies and individuals in Guatemala who assisted this project. They include: 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, Julian Tesucún, Melisa Orozco, Silja Ramirez, Gabriela Alfaro, and Jacobo Blijdenstein. We also thank the personnel of DOSECC (Drilling, Observation and Sampling of the Earth’s Continental Crust) who were instrumental in obtaining the cores. We are indebted to Anders Noren, Kristina Brady and Amy Myrbo of LacCore (National Lacustrine Core Facility), Department of Earth Sciences, University of Minnesota-Twin Cities for their expertise in core acquisition, curation and sampling. We thank Gianna Browne and Briony Bowe for sample preparation and Mike Hall and James Rolfe for technical assistance with stable isotope measurements and John Higgins and Gilad Antler for help with the pore fluid modeling. AVT was supported by the Canadian Institute for Advanced Research. This project was funded by grants from the National Environmental Research Council (Award NE/I016716/1 ) and US National Science Foundation ( ATM-0502030 ). Cores were collected with support from NSF, the International Continental Scientific Drilling Program, the Swiss Federal Institute of Technology, and the Swiss National Science Foundation. Radiocarbon analyses were performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under contract DE-AC52-07NA27344.