Geodetic implications on block formation and geodynamic domains in the South Shetland Islands, Antarctic Peninsula

The South Shetland Islands archipelago is dynamically complex due to its tectonic surroundings. Most islands are part of a formerly active volcanic arc, although Deception, Penguin and Bridgeman Islands, as well as several submarine volcanoes, are characterized by active back-arc volcanism. Geodetic benchmarks were deployed and the movement of the lithosphere to which they were fixed measured to provide geodynamic insight for the South Shetland Islands, Bransfield Basin and Antarctic Peninsula area based on surface deformation. These benchmarks' data add spatial and temporal coverage to previous results. The results reveal two different geodynamic patterns, each confined to a distinct part of the South Shetland Islands archipelago. The inferred absolute horizontal velocity vectors for the benchmarks in the northeastern part of the archipelago are consistent with the opening of the Bransfield Basin, while benchmark vectors in the southwestern part of the archipelago are similar to those of the benchmarks on the Antarctic Peninsula. In between, Snow, Deception and Livingston Islands represent a transition zone. In this area, the horizontal velocity vectors relative to the Antarctic plate shift northeastwards from N to NW. Furthermore, the South Shetland Islands benchmarks, except for that at Gibbs (Elephant) Islands, indicate subsidence, which might be a consequence of the slab roll-back at the South Shetland Trench. In contrast, the uplift revealed by the Antarctic Peninsula benchmarks suggests glacial isostatic adjustment after the Larson B ice-shelf breakup.
This geodetic research has been carried out with the support of the Spanish Ministry of Education and Science as part of the National Antarctic Program. The following research projects contributed directly to this work: “Recognition and fast evaluation of volcanic activity on Deception Island (GEODESY) (ANT1999-1430-E/HESP)”; “Geodetic Studies on Deception Island: deformation models, geoid determination and Scientific Information System (REN2000-0551-C03-01/ANT)”; “Acquisition of scientific software for GPS data processing (REN2000-2690-E)”; “Geodetic Control of the volcanic activity of Deception Island (CGL2004-21547-E/ANT)”; “Update of the Spanish Cartography for Deception Island (CGL2004-20408-E/ANT)”; “Volcano-tectonic activity on Deception Island: geodetic, geophysical investigations and Remote Sensing on Deception Island and its surroundings (CGLl2005-07589-c03-01/ANT)”; and “Geodetic and Geothermal Researches, Time Serial Analysis and Volcanic Innovation in Antarctica (South Shetland Islands and Antarctic Peninsula (GEOTINANT) (CTM2009-07251/ANT))”.