Tuesday, 28 August 2007
2.PS-57
Tectonic evolution of northern Antarctic Peninsula from brittle mesostructures and earthquakes focal mechanisms
Adolfo Maestro1, Jerónimo López-Martínez2, and Fernando Bohoyo1. (1) Servicio de Geología Marina, Instituto Geológico y Minero de España, Ríos Rosas 23, Madrid, 28003, Spain, (2) Geología y Geoquímica, Facultad de Ciencias, Universidad Autónoma de Madrid, Carretera de Colmenar km 15, Madrid, 28049, Spain
Paleostress results derived from brittle mesoscopic structures at locations on the South Shetland Islands, Antarctic Peninsula and Seymour Island and from focal mechanism analysis show a stress field characterized by both extensional and compressional regimes. The scattering of orientations of maximum horizontal stress (σ1) about NW–SE to N–S and NE–SW trends and of minimum horizontal stress (σ3) with two main NE–SW and NW–SE modes suggests that two stress sources have been responsible for the dominant directions of maximum and minimum horizontal stress in this area. Compresional structures are related to former Phoenix Plate subduction under the Antarctic Plate in Jurassic to present time and to Quaternary isostatic uplift. Stress states with NW–SE trends of σ3 are compatible with subduction-related back-arc extension in the eastern Antarctic Peninsula. NE–SW σ3 orientations are associated with continental fragmentation of the northern Antarctic Peninsula during the Cenozoic.