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

Montoya, Encarni, Rull, Valenti, Stansell, Nathan D., Bird, Broxton W., Nogué, Sandra, Vegas-Vilarrúbia, Teresa, Abbott, Mark B. and Díaz, Wilmer A. (2011) Vegetation changes in the Neotropical Gran Sabana (Venezuela) around the Younger Dryas chron. Journal of Quaternary Science, 26 (2), 207-218. (doi:10.1002/jqs.1445).

Abstract

The occurrence of the Younger Dryas cold reversal in northern South America midlands and lowlands remains controversial. We present a palaeoecological analysis of a Late Glacial lacustrine section from a midland lake (Lake Chonita, 4.6501°N, 61.0157°W, 884m elevation) located in the Venezuelan Gran Sabana, based on physical and biological proxies. The sediments were mostly barren from ∼15.3 to 12.7k cal a BP, probably due to poor preservation. A ligneous community with no clear modern analogues was dominant from 12.7 to 11.7k cal a BP (Younger Dryas chronozone). At present, similar shrublands are situated around 200m elevation above the lake, suggesting a cooling-driven downward shift in vegetation during that period. The interval from 11.7 to 10.6k 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 11.7k 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.

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Contributors

Author: Sandra Nogué

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