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Eocene calcareous nannofossil biostratigraphy, paleoecology and biochronology of ODP leg 122 hole 762c, eastern Indian Ocean (Exmouth Plateau)

Jamie L Shamrock, University of Nebraska - Lincoln


A relatively complete section of Eocene (∼33.9-55.8 Ma) pelagic chalk from offshore northwestern Australia was used to analyze range and abundance data of ∼250 Eocene species to test the efficacy of the existing CP (Okada and Bukry 1980) and NP (Martini 1971) biostratigraphic zonation schemes. Changes in nannofossil diversity, abundance, and community structure were monitored through several Eocene paleoenvironmental events, as identified by changes in δ13C and δ18O data, to examine variations in surface water conditions. Major changes in nannofossil assemblages, as indicated by dominance crossovers, correspond to paleoenvironmental shifts such as the Paleocene-Eocene Thermal Maximum and the Early Eocene Climatic Optimum. This research also provides systematic paleontology and range data for nine new species and one new genus, and addresses several taxonomic issues in other Eocene species.^ Examination of the calcareous nannofossil biostratigraphy (Section I) showed several potential hiatuses within the stratigraphic section at Hole 762C. The presence of these hiatuses was supported by cross-correlation of planktonic foraminiferal P-zones, magnetostratigraphic reversals and δ13C and δ18O isotopic excursions. A portion of the dissertation was conducted to fulfill the need for a new, integrated age model for Hole 762C, utilizing biostratigraphic, magnetostratigraphic, and stable isotopic data published in the Leg 122 Initial Reports (Haq et al. 1990) and Scientific Results (von Rad et al. 1992) with the calcareous nannofossil data generated in Section I. This new age model allowed revision of sedimentation rates at Site 762, and these revised rates were used to estimate the ages of calcareous nannofossil bioevents, which are compared to several additional, globally distributed localities.^

Subject Area

Paleontology|Sedimentary Geology|Paleoclimate Science

Recommended Citation

Shamrock, Jamie L, "Eocene calcareous nannofossil biostratigraphy, paleoecology and biochronology of ODP leg 122 hole 762c, eastern Indian Ocean (Exmouth Plateau)" (2010). ETD collection for University of Nebraska - Lincoln. AAI3432056.