Active tectonics and morphostructure at the northern margin of central Bransfield Basin, Hurd Peninsula, Livingston Island (South Shetland Islands)

Abstract

Geophysical, structural, geomorphological, topographical and bathymetric data from the Hurd Peninsula area, Livingston Island, South Shetland archipelago, suggest that an extensional fault system, orientated NW–SE, together with a conjugate group of NE–SW normal oblique-slip faults, control the landforms in this area. These structures separate fault-bounded blocks of different heights, giving rise to a horstgraben structure. The depressed blocks were filled by glaciers and flooded in part by the sea. The recent movement of these faults can be established from the calculated isopachs of a small Quaternary sedimentary basin, related to this extensional fault system, which shows that sedimentary bed thickness is controlled mainly by the NE–SW fault system. Geomorphological analysis also shows that the NW–SE faults control the main morphostructures of this region. The character of the recent stress tensor has been established from fault-slip data, taking into account only those faults that are related to morphostructures. The calculated palaeostress tensor is extensional, with a N46°E main extension direction, and an average stress ratio of 0.17.