23. UPPER QUATERNARY VEGETATION AND CLIMATE HISTORY OF THE AMAZON BASIN: CORRELATING MARINE AND TERRESTRIAL POLLEN RECORDS1Simon Haberle2 |
ABSTRACTPollen analysis of 37 samples from the Amazon Fan (Sites 930, 931, 932, 936, 938, and 946) show changes in pollen frequencies that may reflect vegetational changes in the Amazon Basin through at least the last 105 k.y. Through most of the records, the relative percentages of pollen and spores exhibit fluctuations that correspond to cyclic changes in climate and sea level. Comparisons with modern Amazon River pollen assemblages suggest that the increase in cold-adapted arboreal taxa such as Podocarpus, Alnus, and Hedyosmum, throughout the last glacial, peaking between 21,000 and 17,000 BP, may represent an expanded distribution of these taxa within the basin in response to a colder climate. Between 36,000 and 28,000 BP, cold-adapted taxa show reduced percentage representations, comparable to levels found in postglacial samples, suggesting a contraction of these taxa in response to a warmer climate. The pollen record suggests that there are only moderate changes in the extent of savanna at times of fluctuating temperature during the last glacial period. This highlights the complex interaction of controlling factors such as precipitation, temperature, and atmospheric CO2 for historical plant distribution in the lowland Amazon Basin as well as in the Andes. |
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