La fracturación en el Cabo Shirreff, Isía Livingston, Antártida Occidental

Abstract

The Cape Shirreff, located in the northern part of Livingston Island, South Shetland Islands, represents one of the points of this island arc adjacent to the related trench. Here outcrop a volcanic succession with, probably, an Upper-Cretaceous age. A fault tectonic analysis was performed here in order to decipher the deformation processes that take place in an island arc close to a subduction zone. The measured faults show dip-slip and normal-oblique slip senses of movement, and they have four different trends (N120°E,

N20°E, NT50°E and N80°E). These directions are subparallel with the main linear landforms (valleys and scarps) and with the coastal line geometry. Seventy-nine fault slickensides measured in the volcanic materials have been analyzed by means of fault population analysis methods to deduce the stress tensor actives during the fault movements. Five of the calculated stress tensors are extensional, with a regional NE-SO main extension direction (i.e., <y}). The analysis also shows one extensional tensor with NO-SE extension direction. The first stress tensor was probably related with the dyke injection episode, and is compatible with the stresses transmitted from the subduction zone. And the second can be related with the extension associated with the opening of the back-arc basins located towards the south (Bransfield Basin). The precise age of these tensors and the evidences of two different episodes of faulting remain undetermined