HR: 15:10h
AN: OS43C-07 INVITED    [Abstracts]
TI: Modern Climate Forcing of Terrigenous Deposition in the Tropics (Cariaco Basin, Venezuela)
AU: * Martinez, N C
EM: nahysa@bu.edu
AF: Boston University, 685 Commonwealth Avenue. Dept Earth Sciences, Boston, MA 02215, United States
AU: Murray, R W
EM: rickm@bu.edu
AF: Boston University, 685 Commonwealth Avenue. Dept Earth Sciences, Boston, MA 02215, United States
AU: Thunell, R C
EM: Thunell@geol.sc.edu
AF: University of South Carolina, 700 Sumter St. Dept Geological Sciences., Columbia, SC 29208, United States
AU: Peterson, L C
EM: lpeterson@rsmas.miami.edu
AF: University of Miami, 4600 Rickenbacker Causeway. Rosenstiel School of Marine and Atmospheric Sciences, Miami, FL 33149, United States
AU: Muller-Karger, F
EM: carib@marine.usf.edu
AF: University of South Florida, 140 7th Ave. South. Institute for Marine Remote Sensing/IMaRS. College of Marine Science, St. Petersburg, FL 33701, United States
AU: Astor, Y
EM: yastor@edimar.org
AF: Estacion de Investigaciones Marinas de Margarita., Fundacion La Salle de Ciencias Naturales. Aptdo. 144, Porlamar, 6301, Venezuela
AU: Varela, R
EM: rvarela@edimar.org
AF: Estacion de Investigaciones Marinas de Margarita., Fundacion La Salle de Ciencias Naturales. Aptdo. 144, Porlamar, 6301, Venezuela
AB: One approach to deciphering tropical Quaternary paleoclimate records has been to study the composition of terrigenous material in order to infer past changes in hydrologic and atmospheric conditions. We have analyzed the inorganic geochemistry (major and trace elements) of modern sediment traps and shelf sediments in the Cariaco Basin, Venezuela, in order to characterize seasonal variation in deposition of the terrigenous component and to document linkages within the ocean-atmosphere-climate system. Our results show that variation in the chemistry of terrigenous input to the Basin is a sensitive monitor of the annual meridional migration of the Intertropical Convergence Zone (ITCZ). Additionally, terrigenous relative abundances are decoupled from terrigenous absolute fluxes, showing that abundances are not directly related to terrigenous delivery. Changes in mixing between local fluvial sediments, fluvial and/or eolian mafic material, and Saharan dust explains the observed seasonality. The modern seasonal variations are significantly smaller than those observed in the glacial-interglacial paleorecord, indicating that climate sensitivity at the two time scales is very different. Significant contrast in the behavior of Ti/Al between the longer glacial-interglacial time scale and the modern seasonality also suggests that long-term terrigenous deposition is not linked simply to 100-kyr shifting of the ITCZ. The modern data can be reconciled with the glacial-interglacial record by invoking generally drier conditions during glacial periods, combined with intermittent wet conditions caused by precessional forcing. Results from three additional years of time-series data as well as from the continental margin surrounding the basin, will also be discussed.
DE: 1050 Marine geochemistry (4835, 4845, 4850)
DE: 4835 Marine inorganic chemistry (1050)
SC: Ocean Sciences [OS]
MN: 2007 Fall Meeting