Structure and development of the passive continental margin across the Princess Astrid Coast, East Antarctica

Abstract

On the basis of geological and geophysical data, a contribution is made to understanding the structure and evolution of the Earth's crust across the Princess Astrid Coast, East Antarctica, especially in the area of the Schirmacher Oasis and the Wohlthat Massif. The crustal material is mostly composed of medium- to high-grade metamorphics which underwent three important tectogenic events (close of the Archaean, within the Proterozoic and at the close of the Precambrian). The intrusive age of the Eliseev Anorthosite Massif could be determined (2,400 Ma). The dominant structural features in the Schirmacher Oasis show a strike of some 40° to 60° and indicate a NNE-SSW oriented compressional stress regime. It is probably connected with the last major thermotectonic event some 400 to 600 Ma ago. The Phanerozoic history is controlled by the younger Gondwana break-up and N-S oriented tension. The continental crust as a whole is of relatively acid composition. This is also reflected in the negative regional magnetic anomaly. Probably, its origin is linked to late Precambrian thermotectonic activation. A typical feature is the crustal thinning to the north (from some 50 to 20 km) in connection with deep-reaching E-W crustal faults indicating northward down-faulted blocks.