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Integrated Ocean Drilling Program (IODP) Expedition 318 Hole U1361A (64.2457ºS, 143.5320ºE) is located on the George V Land continental rise (3466 meters below sea level]) ~280 km from the coast (Fig. F1). The purpose of drilling this site was to refine the history of climatic and oceanic changes from the middle Miocene to the Pleistocene and to determine the relative stability of the East Antarctic Ice Sheet (EAIS), especially during warm intervals (e.g., Pliocene) (see the “Site U1361” chapter [Expedition 318 Scientists, 2011b]).

The state of the EAIS after the middle Miocene is a topic of controversy that created two schools of thought among paleoclimate researchers (Miller and Mabin, 1998). “Stabilists” cite evidence that a polar Antarctic ice sheet was established by 14 Ma. In contrast, a considerable amount of evidence suggests a polythermal ice sheet existed from ~33 to 2.5 Ma (Wilson et al., 2002). Current research indicates that the thermal regime of the EAIS varied by location during the Miocene, with a polar EAIS grounded in the Dry Valleys (Marchant et al., 1996; Sugden, 1996) and a polythermal EAIS occupying Wilkes Land and Prydz Bay (Whitehead et al., 2006). These differences in thermal regimes are likely due to the EAIS being grounded below sea level at George V Land and Prydz Bay, making them more susceptible to climactic warming (see the “Site U1361” chapter [Expedition 318 Scientists, 2011b]); Whitehead et al., 2006).

In this study, moderately high resolution stable isotopic ratio (from planktonic and benthic foraminifers) and CaCO3 content records were developed from samples taken from Cores 318-U1361A-34X through 37X (311.60–349.99 meters below seafloor [mbsf]). The purpose of these data were to evaluate cryospheric and Southern Ocean changes during the middle to late Miocene. The CaCO3 content helped identify a new carbonate preservation event (CPE) in the Southern Ocean (DeCesare, 2014). However, diagenesis affected the stable isotope records, limiting our interpretation of cryospheric and oceanographic changes during this study interval.