Thermal history of the southern Antarctic Peninsula during Cenozoic oblique subduction

Apatite (U-Th)/He and apatite fission track thermochronology is used to constrain the cooling and uplift history of the southern Antarctic Peninsula where easterly-directed subduction of the Phoenix Plate, including ridge-trench collisions have been taking place along its western margin since the Upper Cretaceous. Apatite ages and thermal history models are similar on eastern Palmer Land but are younger and vary across westernmost Palmer Land and Alexander Island. Transformation of thermal history models to a single plot show how cooling rates varied as a function of distance from the trench zone. Eastern Palmer Land preserves a record of uplift during the Upper Cretaceous that coincides with changes in Phoenix Plate convergence rates and direction. By contrast western Palmer Land and Alexander Island experienced a period of increased rates of cooling between c. 25-15 Ma. This younger phase of exhumation is bounded by major fault zones related to the extension and rifting that formed the present-day George VI Sound. It was likely triggered by cessation of subduction due to trench collision of a ridge segment NE of the Heezen fracture zone. No evidence was found for slab window influences as seen along the northernmost part of the Antarctic Peninsula.