Date of this Version
The diatom biostratigraphy and paleoceanography of Ocean Drilling Program (ODP) Site 744 on the Southern Kerguelen Plateau, southern Indian Ocean are documented for the early to middle Miocene to improve chronostratigraphic age control for the Southern Ocean and Antarctic region. Paleoenvironmental fluctuations in the Southern Ocean are inferred from changes in fossil diatom abundance, preservation, and assemblage composition. A robust, new age model for Holes 744A and 744B is constructed using Constrained Optimization (CONOP) model ages for diatom biostratigraphic datum levels and new magnetic polarity data, which enables assessment of a nearly continuous record of paleoenvironmental change from ~20.25 to 13.75 Ma, and the dating of specific paleoenvironmental events identified in the diatom record. This study spans stratigraphically from the lowest occurrence of Thalassiosria spinosa var. aspinosa (~20.26 Ma) up to the lowest occurrence of Nitzschia denticuloides (~13.73 Ma), including the interval known as the Mid-Miocene Climatic Optimum (MMCO) ~17 to 15 Ma. Two stratigraphic breaks are recognized at Site 744 during the study interval. Ages interpreted for diatom events at Site 744 confirm the utility of CONOP modeled ages and indentify that Total Range Model and Hybrid Range Model ages presented the greatest utility in age model development at this site. A total of 78 diatom taxa are reported here, more than doubling previous reports, which enables age calibration of many new biostratigraphic datum levels.
Advisor: David Harwood