Rapid Ice Margin Fluctuations during the Younger Dryas in the Tropical Andes |
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| Authors: | Donald T Rodbell Geoffrey O Seltzer |
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| Institution: | a Geology Department, Union College, Schenectady, New York, 12308-2311;b Department of Earth Sciences, Syracuse University, Syracuse, New York, 13244-1070 |
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| Abstract: | Radiocarbon dated lacustrine sequences in Perú show that the chronology of glaciation during the late glacial in the tropical Andes was significantly out-of-phase with the record of climate change in the North Atlantic region. Fluvial incision of glacial-lake deposits in the Cordillera Blanca, central Perú, has exposed a glacial outwash gravel; radiocarbon dates from peat stratigraphically bounding the gravel imply that a glacier advance culminated between 11,280 and 10,990 14C yr B.P.; rapid ice recession followed. Similarly, in southern Perú, ice readvanced between 11,500 and 10,900 14C yr B.P. as shown by a basal radiocarbon date of 10,870 14C yr B.P. from a lake within 1 km of the Quelccaya Ice Cap. By 10,900 14C yr B.P. the ice front had retreated to nearly within its modern limits. Thus, glaciers in central and southern Perú advanced and retreated in near lockstep with one another. The Younger Dryas in the Peruvian Andes was apparently marked by retreating ice fronts in spite of the cool conditions that are inferred from the ∂18O record of Sajama ice. This retreat was apparently driven by reduced precipitation, which is consistent with interpretations of other paleoclimatic indicators from the region and which may have been a nonlinear response to steadily decreasing summer insolation. |
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| Keywords: | Younger Dryas late glacial tropical Andes |
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