HR: 1340h
AN: PP23A-1388    [Abstracts]
TI: 10Be dating of late-glacial moraines near the Cordillera Vilcanota and the Quelccaya Ice Cap, Peru
AU: * Kelly, M A
EM: meredith@ldeo.columbia.edu
AF: Lamont-Doherty Earth Observatory, Geochemistry P.O. Box 1000/61 Rte 9W, Palisades, NY 10964 United States
AU: Thompson, L G
EM: thompson.3@osu.edu
AF: The Byrd Polar Research Center, The Ohio State University 1090 Carmack Road 108 Scott Hall, Columbus, OH 43210 United States
AB: The surface exposure method, based on the measurement of cosmogenic 10Be produced in quartz, is applied to determine the age of deposition of glacial moraines near the Cordillera Vilcanota and the Quelccaya Ice Cap (about 13ø S, 70ø W) in southeastern Peru. These data are useful for examining the timing of past glaciation in the tropical Andes and for comparison with chronologies of glaciation at higher latitudes. The preliminary data set consists of more than ten surface exposure ages. Samples used for dating are from the surfaces of boulders on a set of prominent moraines about four kilometers away from the present ice margins. The age of the moraine set was previously bracketed by radiocarbon dating of peat associated with the glacial deposits. Based on radiocarbon ages, these moraines were formed during the late-glacial period, just prior to the last glacial-interglacial transition. The surface exposure dating method enables the direct dating of the moraines. Surface exposure dates are cross-checked with the previously existing radiocarbon dates and provide a means to improve the chronology of past glaciation in the tropical Andes.
DE: 1035 Geochronology
DE: 1040 Isotopic composition/chemistry
DE: 1625 Geomorphology and weathering (1824, 1886)
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2004 AGU Fall Meeting