TECTONIC PALEOSTRESSES FROM BRITTLE DEFORMATIONS IN BAHIA ESPERANZA (NE ANTARCTIC PENINSULA)

GALINDO-ZALDIVAR, J.; RUIZ-CONSTÁN, A; PEDRERA, A; MARENSSI, S.; MONTES, M; NOZAL, F; RODRIGUEZ FERNANDEZ, L.S; SANTILLANA, S

Buenos Aires

Conferencia; SCAR Open Science Conference; 2010

SCAR

Bahia Esperanza is located in the NE end of the Antarctic Peninsula and constitutes akey region to analyze the overprinted brittle deformations recorded in the outcroppingPaleozoic and Mesozoic detritic and volcanic series and in the Cretaceous igneous rocks.The area undergone extension associated to the opening of the Weddell Sea and bothcompression and extension linked to the southeastward directed subduction that occurredsince the Mesozoic along the Pacific margin of the Antarctic Peninsula. Moreover, theopening of the Powell Basin during the Oligocene and Early Miocene, took place by theeastward drifting of the South Orkney Microcontinent related to the opening of the DrakePassage. Finally, since the late Pliocene, the NW-SE opening of the Bransfield Basin occurs.The region is deformed by NNW-SSE metric to hectometric folds affecting Paleozoic rocksand N-S normal faults with related block tilting. Brittle deformations include a very densejointing, with several sets, highly variable in trends and attitute, locally showing plumosestructures evidencing their extensional character. Paleoestresses have been determinedfrom the analysis of 132 microfaults distributed in 8 measurement stations by the search gridmethod. The inclination of the stress axes suggest a late tilting or that deformation occurredat depth. Dominant stresses indicate N-S to NNW-SSE extension with variable axial ratios,from radial to oblate, that may be related to the Weddell or most probably to the BransfieldBasin opening. Moreover, N-S to NW-SE oblate to WNW-ESE prolate compressive stressesmay be related to the subduction processes that took place along the Pacific Margin ofAntarctic Peninsula.