HR: 15:25h
AN: OS22C-08    [PDF]
TI: Late Quaternary History of the Tropical Pacific: THe Gulf of Tehuantepec Foraminiferal Record
AU: * Machain-Castillo, M L
EM: machain@mar.icmyl.unam.mx
AF: Instituto de Ciencias del Mar y LimnologĦa, Universidad Nacional Aut˘noma de M‚xico, Ciudad Universitaria, A. P. 70-305, Mexico City, 04510 Mexico
AU: Arellano-Torres, E
EM: arellano@mar.icmyl.unam.mx
AF: Instituto de Ciencias del Mar y LimnologĦa, Universidad Nacional Aut˘noma de M‚xico, Ciudad Universitaria, A. P. 70-305, Mexico City, 04510 Mexico
AU: Thunell, R
EM: Thunell@geol.sc.edu
AF: Department of Geological Sciences, University of South Carolina, 700 Sumter Street, Columbia, SC 29208 United States
AU: Lyle, M
EM: mlyle@cgiss.boisestate.edu
AF: Center for Geophysical Investigation of the Shallow Subsurface, Boise State University, Center for Geophysical Investigation of the Shallow Subsurface, Boise, ID 83725 United States
AU: Mix, A C
EM: mix@coas.oregonstate.edu
AF: College of Oceanic and Atmospheric Science, Oregon State University, 104 Ocean Admin Bldg, Corvalis, OR 97331-5503 United States
AU: Pisias, N G
EM: pisias@coas.oregonstate.esu
AF: College of Oceanic and Atmospheric Science, Oregon State University, 104 Ocean Admin Bldg, Corvalis, OR 97331-5503 United States
AB: The geographic location of the Gulf of Tehuantepec makes it sensitive to climatic changes. It is influenced by latitudinal shifts of the Trade Wind System and the Intertropical Convergence Zone which make for a complex oceanographic pattern. Today, two prominent features in the region are: 1) wind induced upwelling during the winter, and 2) a well developed oxygen minimum zone (OMZ) resulting from low oxygen Pacific Intermediate Water and high biological productivity in surface waters. We present the variation of these two features during the Late Quaternary as indicated by planktic and benthic foraminiferal records in a core from the OMZ (740m water depth). The benthic foraminiferal record indicates bottom waters were more oxygenated during the last glacial and a progresive strengthening of the OMZ during the interglacial. Planktic foraminiferal records show the presence of warm stratified waters during late Pleistocene, and increased influence of upwelling during Holocene, probably due to a latitudinal shift of the Trade Wind System. The coupling of these records could suggest that during times of upwelling, increased productivity strenghtened the OMZ. In contrast, in the absence of upwelling, bottom waters would be more oxygenated. However, high biological productivity in the area today is due to both, fertilization induced by upwelling during winter, and the presence of high-nutrient surface water carried out by the Costa Rica Coastal Current (CRCC) during summer and fall. Planktic foraminifera suggests a stronger presence of tropical water (CRCC) in the Gulf of Tehunatepec during Pleistocene, but not necessarily a significant drop in biological productivity. This scenario would require the supply of higher oxygenated bottom waters to the Gulf during glacial times. Ongoing research with other cores and paleoceanographic proxys will aid to elucidate these questions.
DE: 3030 Micropaleontology
DE: 4267 Paleoceanography
DE: 4279 Upwelling and convergences
DE: 4802 Anoxic environments
DE: 4855 Plankton
SC: Ocean Sciences [OS]
MN: 2003 Fall Meeting