HR: 12:05h
AN: T12A-08    [Abstracts]
TI: Upwelling in the Jurassic-Cretaceous Pacific Ocean: Biota Changes and Sedimentary Evidence for Paleoequatorial Crossings of the Pacific Plate
AU: * Erba, E
EM: elisabetta.erba@unimi.it
AF: Department of Earth Sciences, Univ. of Milan, Via Mangiagalli 34, Milan, 20133, Italy
AB: The migration of the Pacific Plate during the Jurassic and Cretaceous can be traced by deciphering the lithological and paleontological composition of sediments deposited under different paleoenvironmental conditions. Several sites drilled during DSDP and ODP legs recovered Cretaceous and, partly, Jurassic sedimentary successions that have been used to reconstruct paleoceanographic changes related to paleolatitudes. In the Pacific Ocean chert, radiolarite and porcellanite are the dominant pelagic lithologies in specific intervals of the Mesozoic, more commonly represented by limestone. The siliceous lithotypes are the expression of biogenic sedimentation in the equatorial fertility belt, whereas limestones result from production of calcareous plankton under stable, oligotrophic conditions. The widespread distribution of massive chert is easily detectable on seismic profiles, where constitutes a strong reflector trough the Northwestern Pacific. Nannofossil quantitative data and sedimentary changes are combined to define the paleoequatorial upwelling belt, characterized by physico-chemico-trophic conditions favoring opportunistic taxa. The results are consistent with previous reconstructions based on shallow-water successions from the tropical Pacific, recording atoll drowning at peri-equatorial locations. The pelagic and neritic carbonate crisis zone approximately between 10° S and 10 °N paleolatidudes may be used to constrain the motions of the Pacific Plate.
DE: 4900 PALEOCEANOGRAPHY (0473, 3344)
DE: 4944 Micropaleontology (0459, 3030)
DE: 4964 Upwelling (4279)
DE: 8157 Plate motions: past (3040)
SC: Tectonophysics [T]
MN: 2007 Fall Meeting