We report the results of downhole stable isotopic (ẟ13Corg [organic carbon] and ẟ15N) and elemental measurements (total organic carbon [TOC], total nitrogen [TN], and carbon/nitrogen [C/N]) of sedimentary organic matter (SOM) along with stable isotopic measurements (ẟ18O and ẟ13C) of left-coiling Neogloboquadrina pachyderma planktonic foraminifers from Ocean Drilling Program Site 1166. TOC and TN measurements indicate a large change from organic-rich preglacial sediments with primary organic matter to organic-poor early glacial and glacial sediments, with mainly recycled organic matter. Results of the stable isotopic measurements of SOM show a range of values that are typical of both marine and terrestrial organic matter, probably reflecting a mixture of the two. However, C/N values are mostly high (>15), suggesting greater input and/or preservation of terrestrial organic matter. Foraminifers are only present in glacial/glaciomarine sediments of latest Pliocene to Pleistocene age at Site 1166 (lithostratigraphic Unit I). The majority of this unit has ẟ13Corg and TOC values that are similar to those of glacial sediments recovered at Site 1167 (lithostratigraphic Unit II) on the slope and may have the same source(s). Although the low resolution of the N. pachyderma (s.) ẟ18O and ẟ13C data set precludes any specific paleoclimatic interpretation, downcore variations in foraminifer ẟ18O and ẟ13C values of 0.5 to 1 amplitude may indicate glacial-interglacial changes in ice volume/temperature in the Prydz Bay region.
