HR: 17:00h
AN: PP24A-05 INVITED     [Abstracts]
TI: Opal Accumulation in the Equatorial Pacific
AU: * Moore, T C
EM: tedmoore@umich.edu
AF: Department of Geological Sciences, University of Michigan 1100 N. University, Ann Arbor, MI 48109-1005
AB: Divergence of the near-surface waters along the Pacific equator has given rise to enhanced productivity and relatively high accumulation rates of biogenic opal throughout most of the Cenozoic. The radiolarian oozes of the Eocene equatorial Pacific are striking for their rich sugary texture and have led many to speculate about what special conditions might have prevailed to have provided such an abundant supply of silica to the deep sea. The detailed Eocene radiolarian stratigraphy developed by ODP Leg 199 workers has given us a much clearer picture of the temporal and spatial patterns of accumulation rates in this region. Within the Eocene average accumulation rates in the equatorial zone varied by a factor of three, with the highest rates occurring in the middle Eocene between 42-43 Ma and near 45 Ma. Variations in accumulation rates in the equatorial zone itself are not matched by similar changes in rates in the region of the NECC divergence. In the Neogene equatorial Pacific average opal accumulation rates vary temporally by a factor of 3 to 6. Not only is variation in opal accumulation higher in the Neogene than the Eocene, but also Eocene opal mass accumulation rates barely rich background Neogene levels, even during times of peak Eocene opal delivery. Thus there is no need to call upon special sources of "extra" silica to supply the Eocene oceans. Rather, the opal-rich sediments of the Eocene derive from the lack of diluents delivered to, or preserved on, the seafloor.
DE: 4900 PALEOCEANOGRAPHY (0473, 3344)
DE: 4912 Biogeochemical cycles, processes, and modeling (0412, 0414, 0793, 1615, 4805)
SC: Paleoceanography and Paleoclimatology [PP]
MN: Fall Meeting 2005