Quaternary Geochronology of Antarctic Glacial Marine Sediments

The overarching goals of this project are to better constrain the chronology and temporal resolution of marine sediment cores from the Antarctic continental shelf, using the naturally-occurring radioisotopes carbon-14 and lead-210. Cores of hemipelagic sediments recovered from shelf basins and drifts on the Antarctic margin preserve high-resolution paleoenvironmental records spanning the Holocene and late Pleistocene, and such cores are currently being studied by a number research groups. An accurate interpretation of these sedimentary archives requires knowledge of (1) appropriate corrections for radiocarbon-based core chronologies, and (2) the effects of bioturbation on the temporal resolution of these sediment records. To address these issues, we undertook detailed, high-resolution downcore measurements of radiocarbon and unsupported lead-210 in the upper portion of sediment cores from two areas of the Antarctic shelf: the Mac. Robertson Shelf (East Antarctica) and the Antarctic Peninsula (West Antarctica). The core sites chosen for this work are the focus of ongoing paleoenvironmental studies, and provided us with a broad range of depositional environments and organic carbon sources, with the idea that the results of our study could be extrapolated to the locations of other studies on the Antarctic continental margin. Project PI Peter Sedwick was responsible for the analysis of cores from two sites on the Mac. Robertson Shelf (the Nielsen Basin and Iceberg Alley), while co-PI Eugene Domack was responsible for analysis of cores from two sites on the Antarctic Peninsula (the Scholleart Drift and the Vega Drift). This report focuses on the results for Antarctic Peninsula cores; detailed results for the Mac. Robertson Shelf cores are presented in co-PI Peter Sedwick's final project report. To date 63 samples from kasten cores 49 and 8 have been analyzed for (1) 14C activity at the NOSAMS facility at Woods Hole Oceanographic Institution and (2) analysis of uranium-series radionuclides (for calculation of unsupported lead-210 activity) by gamma spectrometry in 20 subsamples.