Tectonic reactivation of the Pacific margin of the South Shetland Islands, Antarctic Peninsula

The Pacific margin of the Antarctic Peninsula is shaped by inactive subduction systems and regional transfer zones, yet their relationships remain poorly constrained. New bathymetric and seismic data reveal previously unrecognized tectonic reactivation of the South Shetland’s Pacific margin (SSPM), inactive since subduction ceased ca. 3 Ma. Reactivation occurs along sinistral strike-slip faults across the shelf and upper slope between Elephant and King George islands, partitioning the margin and explaining contrasting GPS patterns. Related deformation includes normal and reverse faults, half-grabens, and pull-apart basins, all linked to this strike-slip regime. This tectonic reactivation that initiated ca. 1.7 Ma reorganizes gullies, deforms trench deposits, promotes mud volcanism, and drives upper-plate deformation. It originates at the junction between the South Scotia Ridge (SSR) and the western Bransfield Basin, implying westward propagation of the SSR into the SSPM. These results provide new constraints on Antarctic geodynamics and show how inactive tectonic systems can be overprinted by adjacent active ones.