Cenozoic stress field in the southwestern Antarctic Peninsula from brittle mesostructures in Wright Peninsula, Adelaide Island

Palaeostresses inferred from brittle mesostructures in the southern Wright Peninsula show a stress field characterized by compressional, strike-slip and extensional regime stress states. The compressional stress (sigma(1)) shows a main NW-SE direction and the extensional stress (sigma(3)) shows a relative scattering with two main modes: NE-SW to E-W and NW-SE. The maximum horizontal stress (sigma(y)) has a bimodal distribution with NW-SE and NE-SW direction. The compressional orientation is related to subduction of the former Phoenix Plate under the Antarctic Plate from the Early Jurassic to the Early Miocene. Extensional structures within a broad-scale compressional stress field can be related to both the decrease in relative stress magnitudes from active margins to intraplate regions and stretching processes occurring in eastern Adelaide Island, which develop a fore-arc or intra-arc basin from the Early Miocene. Stress states with NW-SE-trending sigma(1) are compatible with the dominant pattern established for the western Antarctic Peninsula. NW-SE orientations of sigma(3) suggest the occurrence of tectonic forces coming from fore-arc extension along the western Antarctic Peninsula.