Structure and Tectonic development of the Southern margin of the Scotia Sea East of the Sout Orkney microcontinent

TASSONE, A; LODOLO, E; CIVILE, D.; VUAN, A.

Buenos Aires

Conferencia; SCAR XXXI. .4 th Open Science Conference; 2010

Dirección Nacional del Antártico

The southern margin of the Scotia Sea corresponds to the Scotia-Antarctica plate boundary, along which the relative motion is mostly left-lateral. Available multichannel seismic reflection profiles, combined with literature information, have allowed to define the general structural architecture of the margin to the east of the South Orkney microcontinent, and propose a tectonic evolution for this sector of the plate boundary. Along the margin, which is composed of several bathymetric highs separated by deep troughs and restricted oceanic basins, three main tectonic segments have been identified. These are separated by NNW–SSE-trending release zones, disposed in an en-echelon geometry. The western segment corresponds to the northern margin of the South Orkney microcontinent, where a subduction zone seems to be present. The segment further to the east corresponds to an ENE-oriented basin (the Bruce Deep). To the south of the Bruce Deep, a wide deformation zone with N-verging folds and thrusts (the Jane Thrust Belt) has been identified. The eastern segment of the plate boundary is structurally the less constrained, and may be composed of a series of tectonic lineaments of different lengths. In the western sector of the margin, the Scotia plate seems to have subducted beneath the Antarctic plate, whereas the Weddell Sea subducted beneath Scotia plate, in the eastern sector. The activation of left-lateral transtensional strike–slip lineaments generated narrow pull-apart basins in the fore-arc sectors of the convergent zones. The southern Scotia margin may represent an example of an opposite subduction polarity environment.