HR: 1340h
AN: PP33B-1277    [Abstracts]
TI: A Chronology of Late-Glacial and Holocene Advances of Quelccaya Ice Cap, Peru, Based on ¹⁰Be and Radiocarbon Dating
AU: * Kelly, M A
EM: meredith@ldeo.columbia.edu
AF: Lamont-Doherty Earth Observatory, Columbia University, Geochemistry Division PO Box 1000, Palisades, NY 10964, United States
AU: Lowell, T V
EM: Thomas.Lowell@uc.edu
AF: Department of Geology, University of Cincinnati, 500 Geology/Physics Building,University of Cincinnati, Cincinnati, OH 45221, United States
AU: Schaefer, J M
EM: schaefer@ldeo.columbia.edu
AF: Lamont-Doherty Earth Observatory, Columbia University, Geochemistry Division PO Box 1000, Palisades, NY 10964, United States
AB: The Quelccaya Ice Cap region in the southeastern Peruvian Andes (~13-14°S latitude) is a key location for the development of late-glacial and Holocene terrestrial paleoclimate records in the tropics. We present a chronology of past extents of Quelccaya Ice Cap based on ~thirty internally consistent ¹⁰Be dates of boulders on moraines and bedrock as well as twenty radiocarbon dates of organic material associated with moraines. Based on results from both dating methods, we suggest that significant advances of Quelccaya Ice Cap occurred during late-glacial time, at ~12,700-11,400 yr BP, and during Late Holocene time ~400-300 yr BP. Radiocarbon dating of organic material associated with moraines provides maximum and minimum ages for ice advances and recessions, respectively, thus providing an independent check on ¹⁰Be dates of boulders on moraines. The opportunity to use both ¹⁰Be and radiocarbon dating makes the Quelccaya Ice Cap region a potentially important low-latitude calibration site for production rates of cosmogenic nuclides. Our radiocarbon chronology provides a tighter constraint on maximum ages of late-glacial and Late Holocene ice advances. Upcoming field research will obtain organic material for radiocarbon dating to improve minimum age constrains for late-glacial and Late Holocene ice recessions.
DE: 0720 Glaciers
DE: 1105 Quaternary geochronology
DE: 1150 Cosmogenic-nuclide exposure dating (4918)
DE: 1605 Abrupt/rapid climate change (4901, 8408)
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2007 Fall Meeting