HR: 14:30h
AN: PP53A-03    [Abstracts]
TI: Relevance of Palynological Data for Reconstruction of Abrupt Climatic Change in the Neotropics Region, Based on Marine Sediments from the Cariaco Basin, Caribbean Sea
AU: * Delusina, I
EM: delusina@geolgy.ucdavis.edu
AF: University of California - Davis, Dept. of Geology One Shields Ave, Davis, CA 95616, United States
AB: Pollen analyses from a deep marine core from the anoxic Cariaco Basin, off the coast of Venezuela, encompass the Late Glacial/Bolling-Allerod transition, through the Younger Dryas and into the beginning of the Preboreal. The unique pollen assemblages indicate significant differences, as well as some basic similarities, with pollen results from continental cross-sections and lacustrine deposits of Neotropical regions. Interpretation of the pollen data from these marine sediments must address the specific challenge of distinguishing the climatic signal from preservation patterns in the marine environment. Because the Cariaco Basin acts as a natural sediment trap for rapidly accumulating sediments of marine and terrestrial origin, it provides an opportunity to compare both signals. The pollen assemblages in the basin mirror the complex altitudinal zonation of the coastal vegetation as well as its dynamics in the marine environment which went through the oxic-anoxic transition. Correlation of the pollen data with percentage of sediment lightness, oxygen isotopes, and titanium/iron concentrations in other Cariaco basin cores, as well as a comparison with vascular plant data, shows that the pollen signal is related to climatic events, rather than to a simple preservation pattern. However, an increase in pollen productivity might not be indicative of climate conditions, but of increased discharge of terrigenous material from the continent. The relative constancy in the pollen list and the gradual change in the percentage of counted palynomorphs and the diversity of pollen assemblages speaks to altitudinal reconstruction of vegetation. Thus, the Montana rain forest predominated over deciduous Montana forest or Paramo elements during Bolling-Allerod time, but didn't replace them. At the end of the Late Glacial and in the middle of Younger Dryas time, seasonally dry forest prevailed. At the end of a Heinrich Event (ca 15,500 cal B.P.), the largest shift in vegetation corresponds to an otherwise dry episode, correlated with a drop in lake-levels in northern South America and to hiatuses in terrestrial sedimentation. Thus, the pollen data reliably correspond to other available proxies, and we can conclude that the Neotropical region was not affected by dramatic cooling at the time of cold North Atlantic episodes, such as the Younger Dryas. Instead, these periods correspond to significant dryness.
DE: 4914 Continental climate records
DE: 4950 Paleoecology
DE: 4952 Palynology
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2007 Joint Assembly