Antarctic shelf-slope dynamics: an innovative geophysical approach

• Main Authors: De Batist, M., Henriet, J.P.
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2003
• Subjects: Geophysical surveys; Ice caps; Sediments; Shelf dynamics; PSW; Antarctica; Antarctic Peninsula; Antarctic; Pacific; The Antarctic; Trinity Peninsula; Antarc*; Ice Shelves
• Online Access: http://www.vliz.be/nl/open-marien-archief?module=ref&refid=55840

We investigated a large sub-marine slide – the Gebra Slide – on the continental margin of Trinity Peninsula, Central Bransfield Basin, Antarctic Peninsula. The slide scar is clearly expressed in the bathymetry, over an area of 230 km 2 . The associated debris-flow deposit extends over a total surface of about 280 km 2 . The total volume of sediment involved in the mass movement is about 20 km 3 . The Gebra slide took place in two phases. Indirect dating, using seismis stratigraphic criteria, suggests that both phases occurred at the transition between the last glacial period that affected the area and the present-day interglacial (between 13500 and 6500 yrs. B.P.). Large slope failures like this may be an important factor controlling slope-to-basin sediment transport in periods other than glacial maxima.Integration of swath-bathymetry data and high-resolution seismic reflection profiles on the scale of the whole Trinity Peninsula margin has also allowed us to portray with unprecedented detail the sub-glacial sedimentary system of the Last Glacial Maximum in this part of the Antarctic Peninsula. The studied sedimentary system over extends 250 km, from about 1000 m above sea level to about 2000 m water depth. We propose a model for sub-glacial sedimentary systems during glacial periods that consists of (1) an upper ice-catchment or erosional zone on the innermost continental shelf, extending onshore; (2) a transitional erosional-depositional zone on the inner shelf with drumlins on the sea floor; (3) a depositional outer-shelf zone with mega-scale glacial lineations or “bundle structures”; and (4) a debris apron on the continental slope and base of slop formed under floating ice shelves but with debris delivery linked to grounding lines along the shelf break. The data clearly outline the dramatic shift of oce cover and depositional conditions off the northern Antarctic Peninsula between the LGM and the present day.We also developed a new multi-functional deep-tow reflection seismic acquisition system for collecting good-quality high-resolution seismic data in Antarctic waters. The system is characterised by a modular design, including a surface seismic source, an umbilical cable, a winch with slip-ring units, a MC or SC streamer sub- or deep-tow streamer, a streamer-depth monitor and a deep-water digital acquisition system. The system can be operated in various different configurations: e.g. the sub-tow profiling mode, the full deep-tow profiling mode, the “Jumbo” profiling mode using two receivers, and the “touch-and-go” mode including stationary measurements on the sea floor. The system has been successfully deployed in the Antarctic and in the northeastern Pacific. The system remains under continuous development and new applications are currently being implemented and tested.