Development of High Resolution Chronostratigraphic Models for the Southern Ocean Using Quantitative Biostratigraphy

Tuzzi, Eva¹, Rosemary Dutton Cody², David M. Harwood³, Richard Levy², Diane M. Winter³ (1) Dept. of Geosciences, University of Nebraska, Lincoln, Lincoln, NE (2) ANDRILL Science Management Office, University of Nebraska, Lincoln, Lincoln, NE, (3) Department of Geosciences, University of Nebraska, Lincoln, Lincoln, NE

During the last 30 years scientific drilling expeditions in the circum-Antarctic region have recovered large amounts of paleoenvironmental data from a variety of different proxies. Yet the scientific community has been unable to produce a coherent geologic history for the Antarctic region and Southern Ocean, often generating conflicting interpretations. In particular, the temporal pattern of the evolution of Antarctic climate, ice sheet configuration, Southern Ocean circulation is currently under debate, particularly the time interval between middle Miocene and Plio-Pleistocene. A record of ice sheet fluctuations is largely inferred by interpretations of oxygen isotope data and sequence stratigraphy data from distal ocean basins. In many instances, interpretations do not agree with studies on the Antarctic margin, which provide direct evidence for the persistence of polythermal glacial environmental conditions through Miocene time and into the early Pliocene. To help resolve this debate, a robust tool for chronostratigraphic correlation is required to establish the precise relationship among different environmental proxies, and correlate paleoenvironmental events between Antarctica and Southern Ocean. This study will integrate existing diatom biostratigraphic data and new data from the upcoming ANDRILL Southern McMurdo Sound Project, 2007 (andrill.org) through the development of a high-precision chronostratigraphic database for the middle to late Miocene. Biostratigraphic ranges and events are analyzed by deterministic (CONstrained OPtimization) and probabilistic (RAnking and SCaling) quantitative techniques. This internally consistent database will realize the full potential in time resolution of all available data and will refine regional and global correlation in the assessment of environmental history.