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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 48ka, 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 ∼48ka, 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 (∼48–23ka) closely resembles the temperature records from …