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

Abstract

a b s t r a c tDrill cores obtained from Lake Peté n Itzá , Peté n, 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, Peté n 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 (2172 ka). At $18 ka, Peté n 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.

Vegetation changes in the Neotropical Gran Sabana (Venezuela) around the Younger Dryas chron

“…1), a Podocarpus peak was recorded between 15.0 and 14.5 k cal a BP, suggesting cool and moist climatic conditions . A probably wet and warm climate has been inferred in a few records containing this interval from Central America (Islebe et al, 1995;Hodell et al, 2008). Therefore, it seems that during the B/A interstadial, climates in the northern South American tropics were probably warmer than during the LGM, but cooler than today and possibly dry.…”

“…In Central America, a likely cold interval with average temperatures 2-3 8C lower than today was suggested between around 11.1 and 10.4 k 14 C a BP (13.0-12.3 k cal a BP) in Costa Rica (Islebe et al, 1995). In Guatemala, a dry phase was suggested to have been occurred between 12.8 and 10.4 k cal a BP (Hodell et al, 2008).…”

“…In the Amazon Basin, the continuity of tropical rain forests was reported for the Pleistocene/ Holocene boundary and onwards, but with changes in composition with respect to the Pleistocene forests (Bush et al, 2004). In Central America, Hodell et al (2008) proposed the occurrence of moist conditions around 10.3 k cal a BP, probably caused by a northward displacement of the ITCZ. Hence, the widespread occurrence of the EHW in the northern Neotropical region seems well supported by the existing evidence.…”

“…In Central America, there are two records from Guatemala and Costa Rica which show a clear relationship with the onset of the YD, but the transition to the Holocene remains poorly dated (van't Veer et al, 2000). For example, in a well-dated record from northern Guatemala, Hodell et al (2008) observed a gypsum deposit was formed at 12.8 k cal a BP, indicating the onset of dry conditions. In Costa Rica, a cold reversal termed the La Chonta stadial was recorded, characterized by a downward migration of mountain forest by 300-400 m, which equates to a decrease of 2-3 8C (Islebe et al, 1995).…”

The role of North Brazil Current transport in the paleoclimate of the Brazilian Nordeste margin and paleoceanography of the western tropical Atlantic during the late Quaternary

“…These events seem to have strongly impacted South and Central American paleoclimate. In the northern neotropics, for example at Lake Peten-Itzá (Hodell et al, 2008) and on the Venezuelan continental margin (Peterson et al, 2006), North Atlantic cold events (we will call them "NACE" events and refer to them as occurring at a variety of timescales), such as…”