HR: 09:30h
AN: PP21A-07    [PDF]
TI: Late Quaternary Paleoclimatic History of Tropical South America From Drilling Lake Titicaca and the Salar de Uyuni
AU: * Baker, P A
EM: pbaker@duke.edu
AF: Duke University, Earth and Ocean Sciences, Durham, NC 27708-0227 United States
AU: Fritz, S C
EM: sfritz2@unl.edu
AF: University of Nebraska, Departement of Geosciences, Lincoln, NE 68588 United States
AU: Seltzer, G O
EM: goseltze@syr.edu
AF: Syracuse University, Department of Earth Sciences, Syracuse, NY 13244 United States
AU: Rigsby, C A
EM: rigsbyc@mail.ecu.edu
AF: East Carolina University, Department of Geology, Greenville, NC 27858 United States
AU: Lowenstein, T K
EM: lowenst@binghamton.edu
AF: State University of New York at Binghamton, Department of Geological Sciences, Binghamton, NY 13902 United States
AU: Ku, R
EM: rku@usc.edu
AF: Department of Earth Sciences, University of Southern California, Los Angeles, CA 90089 United States
AB: Seven drill cores were recovered from Lake Titicaca during the NSF/ICDP/DOSECC drilling expedition of 2001. Sub-lake floor drilling depths ranged from 53 to 139 m; water depths ranged from 40 to 232 m; recoveries ranged from 75 to 112 percent. Our most detailed multi-proxy analyses to date have been done on Core 2B raised from the central basin of the lake from 232 m water depth, drilled to 139.26 m sub-lakefloor with 140.61 m of total sediment recovered (101 percent). A basal age of 200 Ka is estimated by linear extrapolation from radiocarbon measurements in the upper 25 m of core; Ar-Ar dating of interbedded ashes and U/Th dating of abiogenic aragonites are underway. The volume and lake level of Lake Titicaca have undergone large changes several times during the late Quaternary. Proxies for these water level changes (each of different fidelity) include the ratio of planktonic-to-benthic diatoms, sedimentary carbonate content, and stable isotopic content of organic carbon. The most recent of these changes, has been described previously from earlier piston cores. In the early and middle Holocene the lake fell below its outlet to 85 m below modern level, lake salinity increased several-fold, and the Salar de Uyuni, which receives overflow from Titicaca, dessicated. In contrast, Lake Titicaca was deep, fresh, and overflowing (southward to the Salar de Uyuni) throughout the last glacial maximum from prior to 25,000 BP to at least 15,000 BP. According to extrapolated ages, the penultimate major lowstand of Lake Titicaca occurred prior to 60,000 BP, when seismic evidence indicates that lake level was about 200 m lower than present. Near the end of this lowstand, the lake also became quite saline. There are at least three, and possibly more, older lowstands, each separated temporally by periods in which the lake freshened dramatically and overflowed. These results will be compared with results from previous drilling in the Salar de Uyuni.
DE: 3344 Paleoclimatology
DE: 3374 Tropical meteorology
DE: 9360 South America
DE: 9604 Cenozoic
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2003 Fall Meeting