HR: 17:00h
AN: U14A-04    [Abstracts]
TI: LGM to Holocene African climate variability and the Sr, Nd, and Pb isotope ratios of eolian deposits off northwest Africa
AU: * Cole, J M
EM: jcole@ldeo.columbia.edu
AF: Lamont-Doherty Earth Observatory of Columbia University, 61 Rt. 9W, Palisades, NY 10964-8000 United States
AU: deMenocal, P B
EM: peter@ldeo.columbia.edu
AF: Lamont-Doherty Earth Observatory of Columbia University, 61 Rt. 9W, Palisades, NY 10964-8000 United States
AU: Goldstein, S L
EM: steveg@ldeo.columbia.edu
AF: Lamont-Doherty Earth Observatory of Columbia University, 61 Rt. 9W, Palisades, NY 10964-8000 United States
AU: Adkins, J F
EM: jess@gps.caltech.edu
AF: California Institute of Technology, MS 100-23 1200 California Blvd., Pasadena, CA 91125 United States
AB: Abrupt changes in African climate from the last glacial period through the Holocene have been documented in a core located off Cap Blanc, northwest Africa, ODP Hole 658C (deMenocal et al, 2000). Large changes in terrigenous sedimentation to the ocean, due in large part to humid-arid shifts in terrestrial vegetation, are observed in the percent terrignous and Th-230 normalized terrigenous flux measurements. While there is overall high biogenic and eolian terrigenous sedimentation, terrigenous input decreased during the African Humid Period (AHP, 14.8-5.5 kyr). Additionally sea surface temperatures were lower during that time compared to the later Holocene. Others have shown that radiogenic isotope isotope ratios of terrigenous deposits from marine and ice cores vary over time and provide provenance information. Alternatively, it has been suggested that changes in Sr isotope ratios of dust may relate to the degree of chemical weathering. We sampled the <63 micron detrital fraction to measure the Sr, Nd and Pb isotope ratios in order to quantify the eolian dust proportion and potential source regions. Nd and Pb measurements record source area contributions. However, Sr isotope data indicate a clear shift toward less radiogenic values during the African Humid Period, where as there is no corresponding change in Nb and Pb values. Additionally, we observe an abrupt termination of the AHP and other rapid events. This research seeks to enhance our understanding of African and low-latitude responses to global climate forcings over the last deglaciation.
DE: 9305 Africa
DE: 9604 Cenozoic
DE: 3344 Paleoclimatology
DE: 3022 Marine sediments--processes and transport
DE: 1040 Isotopic composition/chemistry
SC: Union [U]
MN: 2004 AGU Fall Meeting