HR: 0800h
AN: C21B-1103    [Abstracts]
TI: What Lay Beneath the Larsen B Ice Shelf: Results of the First Survey of a Large Modern Sub Ice Shelf Deposystem
AU: * Leventer, A
EM: aleventer@mail.colgate.edu
AF: Department of Geology, Colgate University, Hamilton, NY 13346 United States
AU: Domack, E
EM: edomack@hamilton.edu
AF: Department of Geosciences, Hamilton College, Clinton, NY 13323 United States
AU: Ishman, S
EM: sishman@geo.siu.edu
AF: Department of Geology, Southern Illinois University, Carbondale, IL 62901 United States
AU: Willmott, V
EM: vwillmot@hamilton.edu
AF: Department of Geosciences, Hamilton College, Clinton, NY 13323 United States
AU: Smith, J
EM: j.a.smith@durham.ac.uk
AF: Department of Geography, University of Durham, Durham, DH1 3LE United Kingdom
AU: Huber, B
EM: bhuber@ldeo.columbia.edu
AF: Lamont Doherty Earth Observatory, 61 Route 9W, Palisades, NY 10964 United States
AU: Brachfeld, S
EM: brachfelds@mail.montclair.edu
AF: Dept. Earth and Environmental Sciences, Montclair State University, Montclair, NJ 07043 United States
AU: Gilbert, R
EM: gilbert@lake.geog.queensu.ca
AF: Department of Geography, Queen's University, Kingston, ON K7L 3N6 Canada
AU: Padman, L
EM: padman@esr.org
AF: Earth and Space Research, 3350 SW Cascade Ave., Corvallis, OR 97333 United States
AB: Extraordinary weather conditions this past Austral field season in the NW Weddell Sea allowed a marine geologic expedition to enter the formerly ice shelf bound coastal regions of the Oscar II Coast located along the eastern northern side of the Antarctic Peninsula. In February to March (2005) the US Antarctic Program Research Vessel L. M Gould conducted high resolution seismic reflection (3.5 kHz Chirp), single channel echo sounding, bottom imaging and sampling in conjunction with physical and biological measurements of the ocean water column. The region has only been an open system for about 3 years following the dramatic collapse of the Larsen B Ice Shelf in 2002 and hence we were provided with an opportunity to examine the depositional character of both ice shelf and post ice shelf sediments. Several new insights were provided by our data set including: the observation of a significantly (~25 m) thick syn- to post-glacial section of unconsolidated sediment in a rift-like basin, mapping of two distinct glacial troughs that reach 850-900 m depth and lead to the Hektoria/Evans and Crane Glacial systems, observations of a chemotrophic (cold seep) ecosystem, documentation of post-break up sedimentation patterns including rapid flux of ice rafted detritus, abundant and diverse sediment laden icebergs, biogenic sediment flux to the seafloor, and a spatially varying regime of modern organic (phytoplankton) carbon and lithogenic detritus across the seafloor. In addition, a circuitous grounding line zone was mapped based upon a unique, stratal geometry of dipping and terraced reflectors. Some of these features appear to relate to the historical grounding line of the Larsen B ice shelf system and an earlier and deeper positioned system that may be related to a pause in de-glacial recession of the ice shelf/ice sheet system from the continental shelf. Large diameter jumbo piston cores and gravity cores were collected from the different depositional regimes and the results of these coring efforts will be related to the history of the Larsen Ice Shelf system.
DE: 0728 Ice shelves
DE: 1621 Cryospheric change (0776)
DE: 4811 Chemosynthesis
DE: 4900 PALEOCEANOGRAPHY (0473, 3344)
DE: 9310 Antarctica (4207)
SC: Cryosphere [C]
MN: Fall Meeting 2005