HR: 0800h
AN: U21A-0704    [Abstracts]
TI: Late Pleistocene Paleoclimate Record From the SW African Margin
AU: * Shackford, J K
EM: jshackford1@student.gsu.edu
AF: Georgia State University, Geology 24 Peachtree Center Ave 340 Kell Hall, Atlanta, GA 30303
AU: Christensen, B A
EM: bchristensen@gsu.edu
AF: Georgia State University, Geology 24 Peachtree Center Ave 340 Kell Hall, Atlanta, GA 30303
AU: Elliott, W C
EM: geowce@panther.gsu.edu
AF: Georgia State University, Geology 24 Peachtree Center Ave 340 Kell Hall, Atlanta, GA 30303
AU: Murray, R W
EM: rickm@bu.edu
AF: Boston University, Department of Earth Sciences 685 Commonwealth Ave, Boston, MA 02215
AU: Tappa, E
EM: ejt@geol.sc.edu
AF: University of South Carolina, Department of Geological Sciences, Columbia, SC 29208
AB: Late Pleistocene sediments recovered from ODP Leg 175, Site 1085 are used to generate a high-resolution (500 yr) record of continental climate change in Southern Africa. Sedimentological, geochemical, and clay mineralogical variations of the Cape Basin sediments for the last 200 k.y. are used to determine transport pathways of terrigenous load and continental climate change in southern Africa. The location of Site 1085, the SW African continental slope, provides a continuous hemipelagic section with a significant terrigenous component. Terrigenous sediments are either fluvial or eolian, with fluvial load possibly being controlled by monsoonal circulation and insolation (Christensen et al., 2002; Murray et al., 2002) and eolian by glacial intensification of trade winds. Analyses, including grain size (transport), color reflectance (terrigenous input), biogenic sediment geochemistry including %CaCO3, % organic carbon, and C:N (terrigenous input, productivity), bulk sediment geochemistry (continental climate, terrigenous sediment source, and productivity), benthic foraminiferal stable isotopes (chronology), and clay mineralogy (source, continental climate, transport pathways), are used to identify continental climate conditions in southern Africa, and to address possible forcing mechanisms of climate change in the region during the last 200 k.y. Analyses indicate significant glacial and interglacial variation. Color reflectance and %CaCO3 covary down section, with highest values during MIS1, while there is an inverse correlation between color reflectance, median grain size and C:N ratios, with greatest terrigenous carbon during MIS 1. Peaks in median grain size are associated with boundaries between MIS 1 and 2 as well as MIS 2 and 3. Our results differ from Stuut et al. (2002), who find increased eolian sediments from grain size within glacial stages on the Walvis Ridge, north of the Cape Basin, rather than at the boundaries. Clay mineralogy, determined after removal of calcite, indicates the presence of smectite, different from the modern regional maps of Petschick et al. (1996). Presence of smectite downcore may attest to increased continental weathering and possibly a more humid climate in Southern Africa.
DE: 9305 Africa
DE: 3344 Paleoclimatology
DE: 4267 Paleoceanography
DE: 1000 GEOCHEMISTRY (New field, replaces Rock Chemistry)
SC: Union [U]
MN: 2004 AGU Fall Meeting