Fracturacion y campos de esfuerzos recientes en el entorno del Estrecho de Bransfield, Antártida Occidental

Abstract

In several outcrops around the central part of the Bransfield Basin, between the Drake and the Antarctic plates, the fracturation main characteristics have been established. A large number of faults, more than 800, were measured in 7 sites (6 in the South Shetland Islands and 1 in the Antarctic Peninsula), showing a wide range of orientations. However, most of the measured faults show a main trend N125°E and a subvertical dip. The strike-slip and normal faults amount about 88% of all the measurements, been the reverse and related faults very scarce in the region. As other previous papers had pointed out (e.g., SANTANACH et al, 1992 and WILLAN, 1994), from the fault cross-cut and movement relationships, together with the regional dyke and vein orientations, several normal and strike-slip stress episodes could be inferred. The analysis of the normal fault set, probably the younger one, through the right dihedra method (ANGELIER and MECHLER, 1977) show two different maximum horizontal stretching orientations, that probably represents two different stress episodes. In the first one, the extension direction is orientated NW-SE, is Quaternary in age and is observed in the sites located in the north and south margins of the central Bransfield Basin, and in Deception Island. The second episode shows a NE-SW extension direction, was probably developed during the interval Paleogene to Cretaceous, and it is showed in the outcrops located far away from the Bransfield Basin margins.