HR: 1340h
AN: PP43B-1248    [Abstracts]
TI: Temporal and spatial paleoproductivity patterns associated with Eastern Mediterranean sapropels: paleoceanographic significance.
AU: Gallego-Torres, D
EM: davidgt@ugr.es
AF: Instituto Andaluz de Ciencias de la Tierra (CSIC-UGR), Facultad de Ciencias, Campus Fuentenueva, Universidad de Granada, Granada, 18002, Spain
AU: Gallego-Torres, D
EM: davidgt@ugr.es
AF: Departamento de Mineralogía y Petrología, Universidad de Granada, Facultad de Ciencias, Campus Fuentenueva, Universidad de Granada, Granada, 18002, Spain
AU: Martinez-Ruiz, F
EM: fmruiz@ugr.es
AF: Instituto Andaluz de Ciencias de la Tierra (CSIC-UGR), Facultad de Ciencias, Campus Fuentenueva, Universidad de Granada, Granada, 18002, Spain
AU: * Meyers, P A
EM: pameyers@umich.edu
AF: Department of Geological Sciences, The University of Michigan, 2534 CC Little Bldg 1100 North University Ave, Anne Arbor, MI 48109-1005, United States
AU: Paytan, A
EM: apaytan@ucsc.edu
AF: University of California, Santa Cruz, Earth and Marine Sciences Building Rooms C453 and C474 Santa Cruz 1156 High Street, Santa Cruz, CA 95064, United States
AU: Jimenez-Espejo, F J
EM: fjjspejo@ugr.es
AF: Instituto Andaluz de Ciencias de la Tierra (CSIC-UGR), Facultad de Ciencias, Campus Fuentenueva, Universidad de Granada, Granada, 18002, Spain
AU: Jimenez-Espejo, F J
EM: fjjspejo@ugr.es
AF: Departamento de Mineralogía y Petrología, Universidad de Granada, Facultad de Ciencias, Campus Fuentenueva, Universidad de Granada, Granada, 18002, Spain
AU: Ortega-Huertas, M
EM: mortega@ugr.es
AF: Departamento de Mineralogía y Petrología, Universidad de Granada, Facultad de Ciencias, Campus Fuentenueva, Universidad de Granada, Granada, 18002, Spain
AB: Deposition of Eastern Mediterranean sapropels has been discussed in terms of enhanced primary productivity and/or preferential preservation due to anoxic conditions in the deep basin. However, formation of these organic enriched layers is not homogeneous across the basin and through time, and temporal and spatial patterns can be observed in organic carbon concentrations and depositional conditions. We used a transect of ODP sites in the Eastern Mediterranean for the study of such variations, covering the area of major influence of the European continent and incoming waters from the Western Mediterranean basin (Ionian basin, Site 964), a region of influence of the Nile River (Levantine basin, Site 967), the central region of the basin with minor continental influence (Mediterranean Ridge, Site 969), and shallower bathymetries (Eratosthenes Seamount, Site 966). A set of paleoproductivity related proxies has been applied in order to reconstruct the paleoceanographic conditions that led to the formation of sapropels. As a whole, sapropel formation corresponds to wetter periods occurring during precessional minima and appears associated to increased productivity, evidenced by Ba/Al, and TOC-Ba mass accumulation rates maxima. δ13C data indicate intensified carbon fixation during organic carbon entrapment in sediment, where as low δ15N values provide evidence of nitrogen fixation through cyanobacteria activity as a source of increased primary and export productivity. This overwhelming export productivity led to the depletion of deep water dissolved oxygen, thus improving organic matter preservation. The above mentioned proxies show that sapropels represent periods of high productivity in an otherwise oligotrophic basin. This productivity was initiated and sustained by a change in bacterial community to nitrogen-fixing organism favored by intensified continental drainage and nutrient input. In agreement to this observation, sapropel onset generally occurred earlier in the Levantine basin, directly influenced by variations in the Nile River discharge, and progressively spread toward the western part of the basin. Thus, this change in paleoceanographic conditions is ultimately climatically driven and the evolution of the regional climate affects the intensity of the sapropel formation for the last 3 My. Intensified productivity and enhanced preservation is observed during sapropel deposition from the middle Pliocene until the lower Pleistocene. Productivity maxima occur during the late Pleistocene, coinciding with highest recorded sedimentary rate, and a relatively weak increase is observed during the deposition of the Holocene sapropel. This pattern implies that the rates of deep-water ventilation and of continental erosion generally increased in the eastern Mediterranean region as climate cooled since the mid-Pliocene.
DE: 4900 PALEOCEANOGRAPHY (0473, 3344)
DE: 4912 Biogeochemical cycles, processes, and modeling (0412, 0414, 0793, 1615, 4805)
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2007 Fall Meeting