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.