HR: 0800h
AN: PP11B-1468    [Abstracts]
TI: Provenance Variability Expressed by Mineralogical Composition of Cenomanian-Turonian Deposits From the Western Tethys (DSDP Site 386)
AU: * Horst, P A
EM: phors002@fiu.edu
AF: Florida International University, Department of Earth Sciences 11200 SW 8 Street PC 344, Miami, FL 33199 United States
AU: Sandler, A
EM: sandler@mail.gsi.gov.il
AF: Geological Survey of Israel, 30 Malkhe Yisrael Street, Jerusalem, 95501 Israel
AU: Maurrasse, F J
EM: maurrass@fiu.edu
AF: Florida International University, Department of Earth Sciences 11200 SW 8 Street PC 344, Miami, FL 33199 United States
AB: Cenomanian-Turonian sediments at DSDP Site 386, Core 39, 43, 44, and 47, (Bermuda Rise) are essentially mudstones of predominately grayish to nearly black in color in the Cenomanian, becoming predominately red in the Turonian. They are typically laminated and consist mainly of fine silt- and clay-size quartz and phyllosilicates. The gray sediments contain phyllosilicates (25-40% of the bulk composition) that include mostly illite-smectite (60-75%) with less than 2% kaolinite within the clay fraction. The illite-smectite component can be further characterized into discrete smectite and illite-smectite (60-70% expandability). The gray sediments in the lower part (Core 47) of the studied interval are low in organic matter (up to 5.5%) and low in illite-smectite, whereas those at higher levels (Cores 43-44) are rich in organic matter (up to 30%), and have higher illite-smectite content. Quartz content is 40-45% of the bulk mineralogy of sediments low in organic matter (up to 5.5%) and 60-70% of the bulk mineralogy of sediments high in organic matter (up to 30%). Quartz content is high even in the clay fraction (<2μm) (10% or higher). The carbonate values are usually nil, but increase intermittently from 3.5, 12, 17, 55, up to 71%. In contrast, the red sediments (Core 39) contain more phyllosilicates (50-55%) predominately composed of one-type illite-smectite (70%) of high expandability. They also have kaolinite (15%) and clinoptilolite (5-10%). Quartz content in these sediments is 20-25% of the bulk mineralogy, and they are characteristically poor in organic matter (0-0.2%), whereas quartz content in the clay fraction (<2μm) is negligible. The carbonate values are consistently close to zero throughout. The clay mineralogy of the sediments implies both oceanic and continental provenances. The oceanic component of the gray sediments is discrete smectite, whereas the associated illite-smectite indicates a continental origin. The highly expandable illite-smectite and the kaolinite of the red sediments indicate a continental origin from subtropical soils, while the clinoptilolite is of marine origin. These mineralogical variations reflect both the relative proximity of Site 386 to the mid-oceanic ridge, as well as the effect of complex paleophysiographic changes related to the opening of the North Atlantic that affected oceanic circulation and sediment fluxes within the basin during that time interval. Further mineralogical data will clarify the nature of these changes.
DE: 4558 Sediment transport (1862)
DE: 4802 Anoxic environments (0404, 1803, 4834, 4902)
DE: 4825 Geochemistry
DE: 4999 General or miscellaneous
DE: 9610 Cretaceous
SC: Paleoceanography and Paleoclimatology [PP]
MN: Fall Meeting 2005