Bransfield Strait and South Shetland Islands sedimentary basement and upper crustal structure: An analysis of gravity and magnetic data at the northwestern area of the Antarctic Peninsula

Abstract

The northwestern region of the Antarctic Peninsula is of main interest to the geosciences. Complex tectonic activity in this area is evidenced by the presence of the sinistral South Scotia ridge system and Shackleton plate contacts; As well as the opening of the Bransfield Strait leading to the formation of the Shetland Block, where the last remnant of the Phoenix convergent margin is located. Potential fields such as gravity and magnetism can be used to study crustal structure in these remote regions, where sedimentary basins are located. In this study, we utilized gravity data from the EIGEN-6C4 combined field model and magnetic data from the ADMAP2 magnetic anomaly model. We employed the Spectral decomposition of gravity anomalies to analyze sedimentary basement depth and directional derivatives of gravity and magnetic anomalies to derive structural features and magmatic activity. The gravimetric basement model was compared with previous interpretations of the acoustic basement and provides a new interpretation of basement morphology in regions that have not been studied previously in detail. The gravity/magnetic derivatives highlight evidence for ongoing magmatic activity in the Central Bransfield Basin which correlates with seismic catalogs, and crustal segmentation between King George and Gibbs Islands related to the unstable intersection of the South Scotia Ridge system and Shackleton Fracture Zone.