PLIO-PLEISTOCENE HISTORY OF THE ANTARCTIC CONTINENTAL MARGIN IN THE WEDDELL SEA, ADJACENT TO DRONNING MAUD LAND

With global climate change and sea level rise, the stability of high latitude ice sheets is being increasingly scrutinized. An historical prospective of their stability is possible through analysis of marginal sediment cores, which provide a record of glacial dynamics. More information about the Pliocene, when ppm atmospheric CO₂may have been as high as today, is needed to understand Pliocene climate dynamics, especially of the mid-Pliocene Warm Period (mPWP, 3.264-3.025 m.y).

This study focuses on the Antarctic continental slope analyzing deep-sea cores taken from the margin of the East Antarctica Ice Sheet (EAIS) within the Weddell Sea at ODP Site 693. Site 693 is in 2359 m of water on the edge of Wegener Canyon. The Plio-Pleistocene section consists of a single, rotary-drilled hole with 44% recovery. With the exception of a few foraminifers in the upper two Pleistocene cores, carbonate microfossils are absent. The result is that chronostratigraphy, based on diatom and radiolarian biostratigraphy and poor to moderate magnetic stratigraphy, is not very good. However, even the poor chronostratigraphy, suggests changes in accumulation rates, higher in the lower Pliocene (>40 m/my), decreasing in the upper Pliocene. Pleistocene sedimentation rates are lowest of all (~10-13 m/my). Recovery is not sufficient to distinguish erosion, non-deposition and low deposition. Nevertheless, by analyzing well-recovered sediments from different Plio-Pleistocene cores we can improve our understanding of this very important continental margin and time.

Our objectives are to determine the glacial history of the EAIS, adjacent to Dronning Maud Land during the Plio-Pleistocene using 1) wt. % abundance of the sand fraction, 2) coarse-fraction mineralogy, and 3) fine fraction elemental changes. The study area is adjacent to a region that modeling simulations suggest was the first to develop continental ice sheets, but the ice sheet did not expand for a considerable length of time (Deconto and Pollard, 2003).

Our analysis includes major and trace element identification, using XRF core-scanning, with discrete XRF sediment analyses to convert elemental counts to elemental wt.%. Coarse and fine fractions were separated by wet sieving and mineral identification is done with a light microscope and a SEM with an EDAX system.