UTIG RESEARCH PROJECTS ARCHIVE

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Neotectonic Evolution of Antarctic Peninsula/Scotia Sea Region

Principal Investigators: Lawrence A. Lawver

Funded by: National Science Foundation

Location of cruise (caution! large map)

Abstract
The neotectonic evolution of the Antarctic Peninsula and Scotia Sea is extremely complex. Understanding the recent evolution of the Drake-Scotia-Antarcticia-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.

A 44 day marine geophysical cruise on RVIB N.B. Palmer is planned. The cruise is scheduled to leave from Punta Arenas, Chile. Upon arrival in Bransfield Strait, after an initial SEABEAM 2200 multibeam bathymetry and sidescan sonar survey of the King George Basin, 10 days will be devoted to "vent sniffing" by Gary Klinkhammer of Oregon State University. Approximately 5 days will then be devoted to completing the sidescan sonar survey of the Bransfield Strait. Upon completion of the Bransfield Strait work, about 6 days will be devoted to a multibeam and sidescan sonar survey of the Southwest Scotia Sea in conjunction with 4 to 6 days of multichannel seismic work. The main goal of this proposal is to collect 5,000 km (assuming 10-12 kts) of multibeam and sidescan sonar surveys to map the structural character and tectonic fabric of the evolving plate boundary in Southwest Scotia Sea, Shackleton Ridge, 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 interpret the impact of their deeper structural data deduced from multichannel and single channel seismic reflection records. Upon completion of work around the Antarctic Peninsula, the ship will depart for Lyttleton, New Zealand. Enroute we will collect underway geophysical data SEABEAM 2200 multibeam bathymetry and sidescan sonar work across the South Pacific enroute to the Bransfield Strait.

Bransfield Strait is presently undergoing extension based on high heat flow, active volcanoes and 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 studying the tectonic fabric of Bransfield Strait, the multi-beam and sidescan sonar survey will identify dredge targets and DSRV Alvin dive sites.