Neotectonic Evolution of Antarctic Peninsula/Scotia Sea Region: Multi-Beam, Sidescan Sonar, Seismic, Magnetics and Gravity Studies
This award supports a marine geophysical investigation of the Bransfield Strait and the Shackleton Fracture Zone and environs in the Scotia Sea in an effort to understand the neotectonic evolution of the region. Multibeam swath mapping and sidescan sonar mapping will be used along with multichannel seismic imaging. The main goal of this proposal is to collect multibeam and sidescan sonar data to map the structural character and tectonic fabric of the evolving plate boundary in Southwest Scotia Sea, Shackleton Fracture Zone, and Bransfield Strait. Follow up multichannel seismic surveys will be done in the Southwest Scotia Sea. The secondary goal is to use sidescan sonar reflectivity images to generate detailed structural maps of the seafloor of these regions and to integrate the new data with existing seismic reflection, Geosat gravity, Hydrosweep and Seabeam bathymetric data. Once the base maps are produced they can be used by other researchers to help interpret multichannel and single channel seismic reflection records. The neotectonic evolution of the Antarctic Peninsula and Scotia Sea is extremely complex. Understanding the recent evolution of the Drake-Scotia-Antarctic-South America plate intersections will provide important information as to how major plate boundaries reorganize after demise of a long-lived spreading center and the consequential reduction in the number of plates. The plate reorganization probably resulted in the uplift of the Shackleton Ridge which may have effected the sedimentary patterns in both the Scotia Sea and possibly the Weddell Sea. If the break of the Shackleton transform fault can be traced with multibeam and sidescan sonar as it intersects the southern end of South America then the orientation and geometry of the faults, fractures and deformation as the transform fault intersects the South American continent will help to interpret the structures in that complex region. Bransfield Strait is presently undergoing extensi on based on high heat flow, active volcanoes and inferences from seismic reflection work. Seismic refraction indicates thick crust similar to the East African Rift or passive volcanic margins of continents. In contrast, analysis of isotopes and rare earth elements of the recent volcanics shows seemingly no continental contamination. The active extension in Bransfield Strait must be related to the plate reorganization but it is unclear exactly what tectonic processes are occurring. Besides elucidating the tectonic fabric of Bransfield Strait, the multibeam and sidescan sonar survey will identify potential dredge targets and DSRV Alvin dive sites.
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