Miocene Glacio-eustasy and Carbonate Sequences on the Marion Plateau, Northeastern Australia: Inferences from Distal Slope Records

Understanding the timing and magnitude of eustatic changes (global sea-level) is key to improving sequence stratigraphic and sedimentologic models, with wide implications for environmental changes and future exploration of fossil fuels. In the Oligo-Miocene, the magnitude of eustatic changes also provides a clue on Antarctic ice volume. The current best eustatic curve is largely based on records from the New Jersey margin, which needs to be checked against independent records to insure for accuracy of the results. One such independent record is the carbonate sequences of the Marion Plateau (drilled during ODP Leg 194), which have been critical in reconstructing the amplitude of the middle Miocene sea-level fall. However, core recovery during Leg 194 was generally poor, thus hindering a detailed stratigraphic correlation needed for the interpretation of orbital scale sea-level changes. In this paper, we identify 3rd order sea-level sequences in distal slope carbonates by integrating sedimentological observations, downhole logging data, and new biostratigraphic age models between two distal carbonate slope sites. The two sites integrated into a common splice give an almost continuous and well-dated record that yield a sequence stratigraphic framework for this system. Sequences are then compared to glacio-eustatic events seen in the oxygen isotope records. We identified sedimentary sequences linked to glacio-eustatic events Mi3, Mi4, Mi5 and potentially Mi6. From this work we can constrain the timing of platform exposure and of the eventual platform demise, with implications for the quantification of middle Miocene sea-level changes and Antarctic ice volume.