Collaborative Research: (GRGC) High Resolution Glacial Geologic and Palynologic Records of the Last Deglaciation in the Tropical Andes

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9422423 Young The primary objective of the proposed project is to obtain continuous, high-resolution, AMS 14C datable proxy records of glaciation and vegetation change from lacustrine sediment cores that span the last deglaciation and Holocene from four regions in the tropical Andes where evidence for abrupt climatic reversals during the last glacial-to-interglacial transition have already been documented. The PIs seek to improve not only the chronology of late-glacial climatic oscillations in the tropical Andes but also to improve the basis for interpreting the sedimentologic and palynologic records. Specifically, the PIs propose: i) to couple glacial geology and glacial-lacustrine sedimentology to provide estimates for the timing , rate, and magnitude of changes in glacier equilibrium -line altitudes during the last deglaciation, ii) to couple modern vegetation studies with palynological analyses of sediment cores from the western Amazon Basin to estimate the timing of and paleoclimatic factors responsible for the abrupt changes in vegetation that marked the last glacial-to-interglacial transition in this region, iii) to collaborate with Ecuadorian geologists to date and characterize geochemically conspicuous tephra units that were deposited during the last deglaciation so that these important isochrons may be used to correlate precisely among proxy records of paleoclimate preserved in sediment and ice cores from different sites in the tropical Andes, and iv) to provide closer age constraints for specific moraines, which, based on both preliminary and published radiocarbon ages, were deposited at about the same time as the YD and H1 Events.