HR: 0800h
AN: PP11B-0524    [Abstracts]
TI: Holocene oceanography and climate recorded in laminated sediments of the southern Gulf of California, Mexico
AU: * Gonzalez-Yajimovich, O
EM: yajimo@uabc.mx
AF: Ciencias Marinas, Universidad A. de Baja California, Apdo Postal 453, Ensenada, BC 22800, Mexico
AU: Douglas, R G
EM: rdouglas@usc.edu
AF: University of Southern California, Earth Sciences, Zumberge Hall of Science (ZHS)3651 Trousdale Pkwy, Los Angeles, CA 90089-0740, United States
AU: Gorsline, D S
EM: gorsline@usc.edu
AF: University of Southern California, Earth Sciences, Zumberge Hall of Science (ZHS)3651 Trousdale Pkwy, Los Angeles, CA 90089-0740, United States
AB: Alfonso Basin on the western side of the Gulf of California and Pescadero Basin on the center slope of the east side are basins which have sills or shoreward slopes in the Oxygen Minimum Zone and preserve laminations whose physical and geochemical characteristics yield information on climatic and oceanographic changes. Here primary productivity and sedimentation can be considered as an imperfect proxy of climate. Cores were sampled at 1 cm intervals to produce a record of organic carbon, carbonate, opal and terrigenous content and contained laminated, hemipelagic mud, accumulating at 25-50 cm/kyr. Major changes in sedimentation began at circa 7,200 YBP with major shifts occurring at 4,200 and 3,000 YBP and smaller changes at 1500, 950, and 400 YBP in both basins. A stepwise decrease in mass accumulation rates can be correlated to northern hemisphere summer insolation, and suggests stronger NW winds and decreasing rains. Biogenic records indicate a drop in productivity and terrigenous mud records a shift from wetter to dryer conditions. At 400 YBP a recovery suggests a return to wetter less windy conditions. Three general climatic periods are recognized. Spectral analysis shows a 1-2 kyr climate rhythm in the Gulf and the data suggest that it is mediated by the migration of the Intertropical Convergence Zone (ITCZ) due to orbital precession. The records are marked by strong climate-ocean variability cycles at about 88, 150, 200 and 350 years that appear related to latitudinal shifts of the ITCZ, produced by solar cycles. The variability in all of the sediment records increases after about 2 ka.
DE: 1616 Climate variability (1635, 3305, 3309, 4215, 4513)
DE: 3344 Paleoclimatology (0473, 4900)
DE: 4934 Insolation forcing
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2007 Fall Meeting