HR: 0800h
AN: PP41B-0545    [Abstracts]
TI: Experimental Dissolution of Fine-Fraction Carbonate Sediments From the Paleocene
AU: * Schneider, L J
EM: lschneid@geosc.psu.edu
AF: Penn State University, 541 Deike Building, University Park, PA 16801,
AU: Bralower, T J
EM: bralower@geosc.psu.edu
AF: Penn State University, 541 Deike Building, University Park, PA 16801,
AB: Pelagic carbonates play a vital role in sequestering CO2 and buffering the oceans through dissolution. The dominant component of deep-sea carbonates is calcareous nannofossils, a group that plays an important role in biostratigraphy, paleoecology and paleoceanography. The composition of assemblages is readily altered by dissolution in the water column, on the seafloor, and within the sediment column. It is therefore necessary to have some understanding of changes in the assemblage composition that may have occurred as well as the dissolution processes involved. Previous studies utilized experiments to constrain the susceptibility of nannofossil taxa during dissolution. While they noted general patterns related to ultrastructure, little is known about how dissolution affects fine-fraction carbonates at the scale of individual crystals of calcite. In this study we use long-term dissolution experiments to recreate dissolution of Paleocene nannofossils from the Indian Ocean in the water through sediment column. This assemblage is diverse and has a range of delicate to robust species and several different calcite morphologies. Detailed observations of subtle changes in the calcite crystals of nannofossils in the SEM reveal information on dissolution processes in pelagic carbonates and the factors that render specific morphologies more susceptible to dissolution. The morphologic alterations of nannofossil species in the light microscope can be used to create a quantitative index for dissolution. This index is based upon etching of rims, the presence of central areas, and the relative abundance of resistant taxa. A quantitative, rather than a subjective, dissolution index will help determine the preservational state of pelagic carbonates from the Paleocene.
DE: 4900 PALEOCEANOGRAPHY (0473, 3344)
DE: 4912 Biogeochemical cycles, processes, and modeling (0412, 0414, 0793, 1615, 4805)
DE: 4944 Micropaleontology (0459, 3030)
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2007 Fall Meeting