Structure of the South Powell Ridge (NE Antarctic Peninsula): new clues for changing tectonic regimes near the Scotia/Antarctica Plate boundary

The structure of the South Powell Ridge (SPR), separating the Late Cenozoic ocean-floored Powell Basin and the Mesozoic Weddell Sea domain, is revealed by multichannel seismic data. The SPR appears as a basement high, bounded northward by transtensional faults and by normal and major reverse faults to the south. These margin features seem to be linked to the Powell Basin southern strike-slip margin and to the Jane Arc paleotrench, respectively. We suggest the ridge evolved from the Antarctic Peninsula passive margin to become the deformational front of the Scotia/Antarctica Plate boundary, later being welded to the Antarctic Plate. Received: 18 August 1997 / Revision received: 4 May 1998     

Structure of the South Powell Ridge (NE Antarctic Peninsula): new clues for changing tectonic regimes near the Scotia/Antarctica Plate boundary

The structure of the South Powell Ridge (SPR), separating the Late Cenozoic ocean-floored Powell Basin and the Mesozoic Weddell Sea domain, is revealed by multichannel seismic data. The SPR appears as a basement high, bounded northward by transtensional faults and by normal and major reverse faults to the south. These margin features seem to be linked to the Powell Basin southern strike-slip margin and to the Jane Arc paleotrench, respectively. We suggest the ridge evolved from the Antarctic Peninsula passive margin to become the deformational front of the Scotia/Antarctica Plate boundary, later being welded to the Antarctic Plate.

     

Seismic stratigraphy and tectonics of the northwestern Weddell Sea (Antarctica) inferred from marine geophysical surveys

Marine geophysical studies of the northwestern Weddell Sea show several interesting stratigraphic and tectonic features. Synthesis of the ODP drilling results on the South Orkney Microcontinent with the Circum-Antarctic depositional model allows identification of the main reflectors within the Cretaceous-Cenozoic sedimentary cover.

The age and composition of pre-rift, syn-rift and post-rift units probably vary throughout the region. The observed seismic pattern of the Jane Bank suggests a young asymmetric zone of extension. A seismic record across the South Orkney Trough and Central Scotia Basin indicates an association with an accretion zone and spreading centre.