HR: 1340h
AN: U13B-1159    [Abstracts]
TI: Precessional(?) Variability in East African Aridity During the Past Few Hundred Thousand Years
AU: * Shi, J
EM: shixx067@umn.edu
AF: Large Lakes Observatory and Department of Geological Sciences, University of Minnesota Duluth, Duluth, MN 55812, United States
AU: Brown, E T
EM: etbrown@d.umn.edu
AF: Large Lakes Observatory and Department of Geological Sciences, University of Minnesota Duluth, Duluth, MN 55812, United States
AU: Johnson, T C
EM: tcj@d.umn.edu
AF: Large Lakes Observatory and Department of Geological Sciences, University of Minnesota Duluth, Duluth, MN 55812, United States
AU: Scholz, C A
EM: cascholz@syr.edu
AF: Department of Earth Sciences, 204 Heroy Geology Laboratory, Syracuse University, Syracuse, NY 13244, United States
AU: Cohen, A S
EM: acohen@arizona.edu
AF: Department of Geosciences, University of Arizona, Tucson, AZ 85721, United States
AU: King, J
EM: jking@gso.uri.edu
AF: Graduate School of Oceanography, University of Rhode Island, Narragansett, RI 02882,
AB: We used scanning X-ray fluorescence to investigate fluctuations in calcium abundance in the upper 200 m of cores MAL05-1B and 1C recovered by the Lake Malawi Drilling Project from a central lake site. Conspicuous variations in calcium concentrations reflect the abundance of endogenic calcite, which accumulates during periods of relatively dry conditions in the Malawi basin. Major calcium peaks occur at fairly regular intervals down core. The power spectrum of calcium on a depth scale reveals a large concentration of variance in the 20-meter- band. More detailed analyses were undertaken on MAL05-1C which has a well-constrained age-depth model built on radiocarbon, paleointensity, inclination, 10Be, and OSL dating [Scholz et al., in press]. We attribute the cycles of calcium fluctuation in MAL05-1C to monsoonal climate driven by variations in local insolation dominated by eccentricity-modulated precession. Scholz, C.A., T.C. Johnson, A.S. Cohen, J.W. King, J.A. Peck, J.T. Overpeck, M.K. Talbot, E.T. Brown, L. Kalindekafe, P.Y.O. Amoako, R.P. Lyons, T.M. Shanahan, I.S. Castaneda, C.W. Heil, S.L. Forman, L.R. McHargue, K. Beuning, J. Gomez, and J. Pierson, East African megadroughts between 135-75 kyr ago and implications for early human history, Proceedings of the National Academy of Sciences, in press.
DE: 1105 Quaternary geochronology
DE: 3255 Spectral analysis (3205, 3280)
DE: 4914 Continental climate records
DE: 4942 Limnology (0458, 1845, 4239)
DE: 9305 Africa
SC: Union [U]
MN: 2007 Fall Meeting