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Vegetation changes in the Neotropical Gran Sabana Venezuela around the Younger Dryas Chron






JQS. Journal of Quaternary Science 26.2

Vegetation changes in the Neotropical Gran Sabana Venezuela around the Younger Dryas Chron

The occurrence of the Younger Dryas cold reversal in northern South America midlands and lowlands remains controversial. We present a paleoecological analysis of a Late Glacial lacustrine section from a midland lake (Lake Chonita, 4.6501 degrees N, 61.0157 degrees W, 884 m elevation) located in the Venezuelan Gran Sabana, based on physical and biological proxies. The sediments were mostly barren from approximately 15.3 to 12.7 k cal a BP, probably due to poor preservation. A ligneous community with no clear modern analogs was dominant from 12.7 to 11.7 k cal a BP (Younger Dryas chronozone). At present, similar shrublands are situated around 200 m elevation above the lake, suggesting a cooling-driven downward shift in vegetation during that period. The interval from 11.7 to 10.6 k cal a BP is marked by a dramatic replacement of the shrubland by savannas and a conspicuous increase in fire incidence. The intensification of local and regional fires at this interval could have played a role in the vegetation shift. A change to wetter, and probably warmer, conditions is deduced after 11.7 k cal a BP, coinciding with the early Holocene warming. These results support the hypothesis of a mixed origin (climate and fire) of the Gran Sabana savannas, and highlight the climatic instability of the Neotropics during the Late Glacial. Abstract Copyright (2010), John Wiley & Sons, Ltd.

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Accession: 037199250

DOI: 10.1002/jqs.1445



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