HR: 0830h
AN: PP31B-0256    [PDF]
TI: Depositional Architecture and Seafloor Mapping of the Vega Drift, Erebus and Terror Gulf, Antarctic Peninsula
AU: * Backman, E
EM: ebackman@hamilton.edu
AF: Hamilton College, Department of Geology, Clinton, NY 13323 United States
AU: Domack, E
EM: edomack@hamilton.edu
AF: Hamilton College, Department of Geology, Clinton, NY 13323 United States
AB: High resolution sediment archives on the Antarctic continental shelf are providing detailed paleoenvironmental records with unprecedented resolution (for example the Palmer Deep). Yet we are only beginning to discover the true extent and nature of these sediment deposits. Geophysical data collected in 2000, on the Nathaniel B. Palmer (NBP) in the northern Prince Gustav Channel, discovered the presence of the Vega Drift. The drift was originally believed to be restricted to the northern Prince Gustav Channel, however additional swath bathymetric data gathered on the NBP 01-07 cruise in the Erebus and Terror Gulf revealed that the Vega Drift extends much farther that once believed, with an estimated area of approximately 6,140 km2, making the Vega Drift is the largest sediment drift on the Antarctic continental shelf. Drifts are areas where thick sequences of sediment have been deposited by deep-water bottom currents, which result from thermohaline and tidal circulation. High resolution acoustic Chirp profiles allowed us to develop a detailed isopach of the deposit that revealed four distinct centers of drift accretion and surfaces of active sediment erosion. This shows that the Vega Drift is a channel-related drift with the depositional centers located just outside the channels on basement highs while a more broad sediment apron tapers off into the Erebus and Terror Gulf. It is the confinement and then deceleration of currents in both the Prince Gustav Channel and the Antarctic Sound (as they enter the Erebus and Terror Gulf) that provides the focus for deposition across a relict glacially sculpted surface. Complementing the subsurface view of the drift are bottom video surveys that reveal distinct contrasts in sediment transport and erosion across the drift surface, consistent with the deposit's complex architecture. Drift accretion began in the early Holocene, perhaps Late Pleistocene as revealed by jumbo piston cores in excess of 23 m in length. Sedimentation was marked by several episodes of laminated diatom ooze and siliciclastic mud deposition. Diatom ooze laminations are unique within the Vega Drift, in regards to their species composition when compared to other drift accumulations. Radiocarbon dating of in situ molluscs provides a temporal framework along with preservation of key laminations of volcanic ash. The dynamic sediment history preserved within the drift deposits along with the preservation of a diverse foraminifera assemblage makes the Vega Drift an attractive target for paleoenvironmental study, as planned for the first SHALLDRILL initiative.
DE: 3022 Marine sediments--processes and transport
DE: 3045 Seafloor morphology and bottom photography
DE: 4267 Paleoceanography
DE: 9310 Antarctica
DE: 9604 Cenozoic
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2003 Fall Meeting