HR: 1340h
AN: PP23B-1413    [Abstracts]
TI: High resolution paleoceanography of the central Gulf of California during the past 15,000 years
AU: * Barron, J A
EM: jbarron@usgs.gov
AF: U.S. Geological Survey, 345 Middlefield Rd. (MS910), Menlo Park, CA 94025 United States
AU: Bukry, D
EM: dbukry@usgs.gov
AF: U.S. Geological Survey, 345 Middlefield Rd. (MS910), Menlo Park, CA 94025 United States
AU: Dean, W E
EM: dean@usgs.gov
AF: U.S. Geological Survey, PO Box 25046 (MS980), Denver, CO 80225 United States
AB: A high resolution paleoceanographic history of the central Gulf of California during the past 15,000 years has been assembled using microfossil (diatom and silicoflagellate) and geochemical proxy data from a composite section of gravity core GGC55 and giant piston core JPC56 in the western Guaymas Basin (27.5 deg. N, 112.1 deg. W, water depth 818 m) and from DSDP Site 480 (27.9 deg. N, 111.7 deg. W, 655 m water depth) in the eastern Guaymas Basin. These data argue for abrupt, basin-wide changes during the Bolling-Allerod, Younger Dryas, and earliest part of the Holocene that mirror changes documented in cores from the Pacific margins of both Baja and Alta California. Between about 10 ka and 6 ka, these central Gulf of California records became more regionally distinctive, as surface and intermediate waters resembling those of the modern-day northern Gulf became dominant and virtually no calcium carbonate or tropical microfossils were preserved in the underlying sediments. Beginning at about 6 ka, tropical microfossils returned to the central Gulf, possibly signaling enhanced El Nino-like conditions. Proxy data suggest that late winter-early spring coastal upwelling was abruptly strengthened on the mainland (eastern) side at about 5.4 ka and again at about 3.0 ka, whereas sediments from the western side of the central Gulf became increasingly diatom poor and calcium carbonate rich. An intensification of northwest winds during the late winter to early spring likely occurred in the central Gulf at about 5.4 ka. Interestingly, this proposed wind shift in the Gulf of California coincides with an abrupt 5.4 ka change to drier conditions in the Cariaco Basin off Venezuela that has been proposed to reflect a southward shift in the mean position of the Intertropical Convergence Zone in response to increasing El Nino-like conditions.
DE: 9355 Pacific Ocean
DE: 4825 Geochemistry
DE: 4267 Paleoceanography
DE: 4279 Upwelling and convergences
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2004 AGU Fall Meeting