An 85-ka record of climate change in lowland Central America

Drill cores obtained from Lake Peten ltza, Peten, Guatemala, contain a similar to 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 similar to 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 similar to 48 ka, signifying a shift toward drier hydrologic conditions and the onset of wet-dry oscillations. During the latter part of MIS 3, Peten 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 (similar to 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 and 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 and during the Last Glacial Maximum (LGM) chronozone (21 +/- 2 ka). At similar to 18 ka, Peten climate switched from moist to and 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 similar to 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 similar to 10.3 ka when rainfall increased markedly in the early Holocene. (C) 2008 Elsevier Ltd. All rights reserved.