An important objective of Ocean Drilling Program (ODP) Leg 188 was to penetrate glacial sediments and recover evidence of the timing for the onset of glacial conditions and ice sheet formation in Prydz Bay (O'Brien, Cooper, Richter, et al., 2001). With this in mind, Site 1166 was selected to obtain sediments below those reached at Site 742 during ODP Leg 119 and to provide a stratigraphic record that spans and includes the transition from preglacial to glacial conditions (O'Brien, Cooper, Richter, et al., 2001). Although recovery was low (16%), this objective was accomplished. The Site 1166 sedimentary section includes glacial, early glacial, and preglacial sediments that record the evolution of Prydz Bay since the late Cretaceous and the development of the adjacent Lambert Glacier-Amery Ice Shelf system (O'Brien, Cooper, Richter, et al., 2001).
Stable isotopic and elemental measurements of sedimentary organic matter (SOM) can provide valuable source and paleoenvironmental information (Meyers, 1994; Popp et al., 1997). Shipboard analysis of a small number of samples from Site 1166 for total organic carbon (TOC) and total nitrogen (TN) elemental abundances revealed significant downcore changes from glacial sediments with little organic carbon and nitrogen (<0.5 and <0.05 wt%, respectively) to preglacial sediments with more significant TOC and TN content (up to 9.27 and 0.27 wt%, respectively) (Shipboard Scientific Party, 2001). Rock-Eval analysis of the organic matter (OM) indicated that preglacial sediments at the base of lithostratigraphic Unit III and in Unit IV are mainly primary OM, whereas the younger glacial/glaciomarine sediments are mainly higher-maturity recycled OM with smaller, variable amounts of primary OM (Shipboard Scientific Party, 2001).
Oxygen stable isotopic measurements of foraminiferal calcite are an established proxy for paleoclimatic and paleoceanographic information (Emiliani, 1955). Foraminifers are rarely found in Site 1166 sediments and are confined to the glacial and glaciomarine sediments of lithostratigraphic Unit I. The majority are the left-coiling variety of the planktonic species Neogloboquadrina pachyderma (s.) that are commonly used for stable isotopic studies in the polar regions (e.g., Mackensen et al., 1989; Hodell, 1993). The purpose of this study is to derive further source, paleoenvironmental, and paleoclimatic information for the Cenozoic evolution of Prydz Bay, using stable isotopic and elemental measurements of SOM and N. pachyderma (s.) foraminifers from Site 1166 sediments.