HR: 1330h
AN: PP22A-1193    [PDF]
TI: Atlantic Intertropical Convergence Zone Variability: a Clay Mineralogy Study of Cariaco Basin Sediments Over the Last 1000 Years
AU: * Schuch, K A
EM: kas50@uakron.edu
AF: University of Akron, 252 Buchtel Common, Akron, OH 44325 United States
AU: Black, D E
EM: dblack1@uakron.edu
AF: University of Akron, 252 Buchtel Common, Akron, OH 44325 United States
AU: Foos, A
EM: afoos@uakron.edu
AF: University of Akron, 252 Buchtel Common, Akron, OH 44325 United States
AB: The Cariaco Basin's high deposition-rate laminated sediments make it one of the best recorders of tropical Atlantic climate and Intertropical Convergence Zone (ITCZ) variability. Different drainage basins within the South American continent and the clays that are fluvially transported from them should be affected as the position of the ITCZ and its associated rainfall migrates through time. Over glacial-interglacial time scales it has been suggested that variations in the paleoposition of the ITCZ influences the suite of clay minerals deposited in Cariaco Basin sediments. Here we present results of much higher resolution clay mineralogy analyses of box and gravity core sediments deposited in the basin over the last 1000 years to examine ITCZ variability on sub-decadal to century time scales. Continuous sampling of well-dated box and gravity core sediments at consecutive 1-mm intervals provides a record with a temporal resolution of 1-3 yrs for the time period ca. A. D. 1000 to 1990. The clay and fine silt size fraction ($<$10 $\mu$m) was analyzed using x-ray diffraction for semi-quantitative and qualitative analysis. Kaolinite and illite co-vary over the length of the record suggesting that variations in these minerals are indicative of fluctuations of terrigenous input to the basin rather than changing weathering regimes. Between A. D. 1000 and 1550 variations in quartz, kaolinite, and illite positively correlate with a prior study of sediment titanium content, an inferred indicator of terrigenous input to the Cariaco Basin. However, the clay/titanium correlation becomes strongly negative between A. D. 1550 and 1990 suggesting a possible change in the source region, and hence paleoposition of the ITCZ, for either the clays or the titanium fraction over this interval. In contrast, chlorite is negatively correlated to sediment titanium percentages over the entire length of the record.
DE: 3022 Marine sediments--processes and transport
DE: 3344 Paleoclimatology
DE: 4215 Climate and interannual variability (3309)
DE: 4267 Paleoceanography
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2003 Fall Meeting