HR: 0800h
AN: PP11A-0217    [Abstracts]
TI: Sediment fabric types reveal Late Neogene precessional forcing in Guaymas Basin, Gulf of California
AU: * Cheshire, H
EM: h.cheshire@ucl.ac.uk
AF: University College London, Gower Street, London, Wc1e 6BT, United Kingdom
AU: Thurow, J
EM: j.thurow@ucl.ac.uk
AF: University College London, Gower Street, London, Wc1e 6BT, United Kingdom
AB: The North Pacific Subtropical High (NPSH) annual migration drives west coast seasonal upwelling and gives impetus to the Trade Winds, creating a coastal OMZ and enhancing preservation. Modern observations and palaeoclimate records show that NPSH migration varies on interannual to millennial timescales. In modern Guaymas Basin, a restricted basin situated at the wet/dry Subtropical divide, varved deposition results from dry- season diatom productivity and wet-season terrestrial flux. High-resolution logging of 75 percent laminated, 63 m, continuous piston core MD02-2515 and 6 m kasten core MD02-2517 has identified eight sediment fabric types. Based on observed climate and supported by climate proxies (discrete and continuous X-ray fluorescence, magnetic susceptibility, biogenic silica, total organic carbon), these types are interpreted as the result of climatic conditions produced by variations in NPSH migration. Measurement of varve thickness and detailed correlation with nearby radiocarbon dated core JPC-56 (Keigwin, 2002) gives an age range of 0-36kyr. Systematic variations in the predominance of one or more sediment types reveal precessional forcing, which drives a 5000-year oscillation of millennial- and centennial-scale wet/dry cycles, with significant non-laminated intervals occurring every 5000 years.
DE: 4504 Air/sea interactions (0312, 3339)
DE: 4904 Atmospheric transport and circulation
DE: 4964 Upwelling (4279)
DE: 9355 Pacific Ocean
DE: 9605 Neogene
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2007 Fall Meeting