Palynological data from a deep marine sediment core from the anoxic Cariaco Basin, off the coast of Venezuela contains unique pollen assemblages which mirror the complex altitudinal zonation of coastal vegetation and its dynamics. The Cariaco Basin acts as a natural sediment trap for rapidly accumulating sediments of marine and terrestrial origin and provides an opportunity to compare both signals. Our pollen analyses encompass the interval from 3 to 12 m in core MD03-2620, covering the Late Glacial/Bolling-Allerod transition, Younger Dryas and the beginning of the Preboreal. The data provide evidence for abrupt changes in climatic conditions, however only dryness/wetness changes can be demonstrated, but not cooling/warming. The correlation of the pollen data with sediment lightness, oxygen isotopes, and titanium/iron concentrations of other Cariaco Basin cores, as well as comparison of our data with vascular plant signals, shows that increases in pollen productivity may be dictated not by warming, but by increases in the discharge of terrigenous material from the continent. The relative constancy in the pollen assemblages and the gradual change of percentage of counted palynomorphs, speaks to altitudinal reconstruction of vegetation. Thus, the evergreen rain forest prevailed over the deciduous montane forest and Paramo elements during Bolling-Allerod time, but didn't replace them. At the end of the LGM and in the middle of the Younger Dryas, it became seasonally dry forest. At the end of Heinrich event (ca 15,500 cal B.P.) the deepest decrease in pollen productivity corresponds to another dry episode, which correlates with a drop in lake-levels in northern South America and hiatuses in terrestrial sedimentation. Overall, the Neotropical region was not affected by dramatic cooling at the time of cold North-Atlantic episodes such as the Younger Dryas, but it did experience significant dryness.

[ return to abstract list ]