Reconstruction Of Eocene To Miocene Antarctic Surface Temperature And Aridity From Bulk Sediment Geochemistry Of Continental Margin Drillholes

Documenting the Cenozoic evolution of Antarctic continental climate and glaciation has been a primary objective of drilling efforts on the Antarctic margin. Here we evaluate the major element geochemistry of detrital sediment from three drilling projects to reconstruct Antarctica's continental surface conditions. The dataset includes analyses of mudstone samples from IODP Site U1356 on the Wilkes Land margin, ODP Site 1166 in Prydz Bay, and three drillholes of the Cape Roberts Drilling Project in the Ross Sea; taken together, these drillcores provide a record of sediments shed from the East Antarctic craton from the early Eocene to the late Miocene. In our conceptual model of erosion and sediment transport, pre-glacial and interglacial mudstones are primarily derived from erosion of soils under transport limited conditions (weathering exceeds erosion), whereas glacial mudstones are derived from continental surfaces that are weathering-limited (erosion exceeds weathering). Within this framework, we interpret the oxide molar ratio of K+Na/Al for pre-glacial and interglacial mudstones on the continental margin as an indicator of paleo surface temperatures and the chemical index of alteration (CIA) as an aridity indicator. Using transfer functions derived for B horizons of modern, active, soils in a range of climate conditions, we are able to show that Antarctica continuously cooled and became progressively more arid from the Early Eocene to the late Miocene with large shifts in continental conditions at the Eocene-Oligocene boundary and the Miocene climate transition. These results will be discussed in the context of other proxies for terrestrial paleoclimates, including paleosols, pollen, clay mineralogy, and organic geochemical proxies.