Bransfield Strait Development In The Tectonic Framework Of Ne Antarctic Peninsula

Abstract

Bransfield Strait is an incipient oceanic back-arc basin developed between the South Shetland Block and the Antarctic Peninsula. The combined analysis of multichannel seismic profiles acquired during several oceanographic cruises and the satellite free air gravity anomaly map allow to establish the development of this basin. The structures show an alongstrike evolution and they are heterochronous. The occurrence of an axial volcanism and the presence of a break-up unconformity reveal that the Central Bransfield Basin is an incipient oceanic basin. Continental extension was asymmetrical and developed a typical lower-plate passive margin in the Antarctic Peninsula and a starved upper plate margin along the South Shetland Block. This structure evolved from a low angle normal fault initiated in the continental margin of the Antarctic Peninsula with top-to-the- NW displacement. The hanging wall of this fault is the South Shetland Block, which moved northwestward from the Antarctic Peninsula margin. Thinning of the continental crust is also presently active in the Western and Eastern Bransfield basins, with formation of half-grabens and associate wedge structures generally opening northwestward. The initiation of Bransfield Strait and its present activity is as a combined consequence of the end of spreading in the Phoenix-Antarctic ridge (3.3