Evolution of the Antarctic Peninsula continental margin from Late Eocene to present: Seismic stratigraphic analysis related to the development of the Antarctic Peninsula Ice Sheet (APIS)
Smith, Russell Tyler
Anderson, John B.
Doctor of Philosophy
This investigation into Antarctic Peninsula Ice Sheet (APIS) development represents research from the stratigraphic record of three geographic areas: The James Ross Basin (northwestern Weddell Sea), the Pacific continental margin of the Antarctic Peninsula, and the Joinville Slope (northwestern Weddell Sea). The stratigraphic architecture of the James Ross Basin, NW Weddell Sea continental shelf, shows three major phases of deposition: pre-glacial, ice sheet growth, and ice sheet dominated. Each stratigraphic unit is characterized based upon seismic facies and stratigraphic architecture, and the ages are inferred from a seismic stratigraphic age model. A total of 34 grounding events of the Antarctic Peninsula Ice Sheet (APIS) are recorded on the continental shelf. The seven oldest glacial unconformities are believed to pre-date all previously identified unconformities on the peninsula continental shelf. An expanded section of Late Pliocene/Pleistocene deposits show a minimum of 10 grounding events. Isopachs of sedimentary sequences on the Antarctic Peninsula Pacific continental margin show shifting depocenters through time. Chronostratigraphic and seismic depth-converted data from ODP 178 cores allow the calculation of sediment flux for shelf units S3-S1 and rise units M6-M1. Sediment flux to the margin increases from the Late Eocene until the Late Pliocene and then decreases slightly from Late Pliocene to present. Significant increases in sediment flux coincide with early development of the APIS and during the early Pliocene warming period (Barker and Camerlenghi, 2002). Minimum glacial denudation rates for the Antarctic Peninsula are in the range of 0.06 to 0.13 mm yr -1. The Joinville Slope sediment wedge located in the northwestern Weddell Sea shows seismic stratigraphic evidence of mixed turbidite/contourite/hemipelagic deposition. A prominent seafloor unconformity and the exposed and eroded basement of the adjacent continental shelf indicate erosion by grounded ice during the Plio-Pleistocene. SHALDRIL recovered core at three drill sites, 12A, 5C, and 6D, and sampled sediments from the upper Oligocene, middle Miocene, and lower and upper Pliocene which are constrained by diatom and calcareous nannofossil assemblages. The sediment wedge shows no apparent hiatuses or large unconformities from Late Oligocene to the Lower Pliocene. Regional sedimentation rates show continuous sedimentation throughout the Late Paleogene and Neogene.