HR: 14:25h
AN: OS43C-04 INVITED    [Abstracts]
TI: The History and Dynamics of Anoxia in Cariaco Basin
AU: * Peterson, L C
EM: lpeterson@rsmas.miami.edu
AF: RSMAS - University of Miami, 4600 Rickenbacker Causeway, Miami, FL 33149, United States
AU: Gibson, K A
EM: kgibson@rsmas.miami.edu
AF: RSMAS - University of Miami, 4600 Rickenbacker Causeway, Miami, FL 33149, United States
AU: Black, D E
EM: dblack@notes.cc.sunysb.edu
AF: School of Marine and Atmospheric Science, Stony Brook University, Stony Brook, NY 11794, United States
AU: Thunell, R C
EM: thunell@geol.sc.edu
AF: Dept. of Geological Sciences, University of South Carolina, Columbia, SC 29208, United States
AU: Lea, D W
EM: lea@geol.ucsb.edu
AF: Dept. of Earth Sciences, University of California, Santa Barbara, CA 93106, United States
AU: Haug, G H
EM: gerald.haug@erdw.ethz.ch
AF: ETH Zurich, Universitatsstrasse 6, Zurich, CH-8092, Switzerland
AB: The Cariaco Basin is the largest modern anoxic marine basin in the world after the Black Sea. Although anoxia involves complex interactions between biological, chemical, and physical processes, the presence or absence of anoxic conditions in the marine environment ultimately reflects a balance between oxygen consumption and supply. A history of this balance in Cariaco Basin, and clues to the climatic and oceanographic controls, is preserved in the underlying sediment record. Much of the late Quaternary sequence in Cariaco Basin is laminated, indicating deposition under anoxic conditions that preclude biological mixing. However, the existence of significant bioturbated intervals indicate past oscillations between oxic and anoxic conditions in the deep basin. To a first-order, glacioeustatic sea level changes appear to play a key role in whether or not anoxic conditions in Cariaco Basin develop, with the effects of sea level on sill depth controlling the availability of nutrients and hence surface productivity. During glacial lowstands, reduced input of nutrients to the basin results in low productivity and oxygenated conditions, while interglacial times of high sea level are linked to strong upwelling, an increased supply of sinking organic detritus and sea floor anoxia. Superimposed on this pattern are millennial-scale oscillations in oxygen levels, best revealed by high-resolution scanning XRF analyses of redox-sensitive elements such as Mo and Cd. During the last glacial, intervals of anoxic deposition coincide one for one with warm interstadials as recorded in Greenland ice cores and require a different explanation. At such times, high productivity may be stimulated by riverine delivery of nutrients rather than by upwelling.
DE: 0404 Anoxic and hypoxic environments (4802, 4834)
DE: 1051 Sedimentary geochemistry
DE: 1620 Climate dynamics (0429, 3309)
DE: 4900 PALEOCEANOGRAPHY (0473, 3344)
DE: 4964 Upwelling (4279)
SC: Ocean Sciences [OS]
MN: 2007 Fall Meeting