HR: 17:30h
AN: PP32D-07 INVITED     [PDF]
TI: Calving Bay Reentrants During the Late Pleistocene to Holocene Retreat of the Antarctic Ice Sheet: Sedimentologic and Geomorphologic Evidence
AU: * Domack, E
EM: edomack@hamilton.edu
AF: Hamilton College, 198 College Hill Road, Clinton, NY 13323 United States
AU: Leventer, A
EM: aleventer@mail.colgate.edu
AF: Colgate University, 13 Oak Drive, Hamilton, NY 13346 United States
AU: Dunbar, R
EM: dunbar@stanford.edu
AF: Stanford University, Department of Earth and Environmental Sciences, Stanford, CA 94305 United States
AU: Brachfeld, S
EM: brachfelds@montclair.edu
AF: Montclair State University, Department of Geology, Upper Montclair, NJ 07043 United States
AU: Manley, P
EM: manley@middlebury.edu
AF: Middlebury College, Department of Geology, Middlebury, VT 07654 United States
AU: McClennen, C
EM: McClennen@colgate.edu
AF: Colgate University, 13 Oak Drive, Hamilton, NY 13346 United States
AB: Swath bathymetric surveys of major paleoice stream troughs from both the West and East Antarctic continental shelf are coupled with Jumbo Piston and ODP (Sites 1098 \& 1099) sediment cores to develop a temporal and spatial model for deglaciation. Deglaciation is demonstrated to have post dated MWP-1a by at least 1000 years for several ice stream systems including those off the Antarctic Peninsula. The nature of sediment lithofacies at the transition from grounded ice to glacial marine conditions demonstrates a process of sediment focusing where by marine varves are deposited in front of calving ice fronts for several hundred years following deglaciation. The marine varves are characterized by alternating couplets of diatom ooze and siliciclastic silty, sandy clays. Sediment core sites that demonstrate this ubiquitous lithofacies are located within inner shelf basins (troughs) that mark the landward juncture of major ice drainage off the continent and initiation of ice streaming out across the continental shelves. Seven such systems are detailed within this study including the Palmer Deep, Mertz Trough, Mertz-Ninnis Trough, Svenner Channel, Nielsen Basin, and Iceberg Alley. Swath bathymetry indicates that ice receded via backstepping of grounding lines within the main axis of the ice stream troughs (i.e. Mertz Trough). This configuration of grounding lines must have led to calving bay reentrants that extended several tens to hundreds of kilometers into the interior of surrounding ice sheets. The focusing of sedimentation within the inner portions of these reentrants is explained by the concentration of iceberg rafting and the restriction of estuarine circulation and associated productivity within the calving bays. The existence of such embayed drainage for several hundred years implies that significant drawdown of ice sheet elevations could have been accommodated by the streaming and calving of glacial ice at the heads of these embayments. The timing of the recessional events is constrained by over 200 radiocarbon dates that fix recession to around 11 ka BP, a thousand years after MWP-1a but roughly coincident with the well known Younger Dryas event.
DE: 3022 Marine sediments--processes and transport
DE: 3344 Paleoclimatology
DE: 4207 Arctic and Antarctic oceanography
DE: 4540 Ice mechanics and air/sea/ice exchange processes
DE: 9310 Antarctica
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2003 Fall Meeting