Patagonia — Antarctica Connections before Gondwana Break-Up

The connections between the Antarctic Peninsula and Patagonia, here referred to as South America south of 44° S, are analysed in the light of new geological information and hypotheses. The previously supposed existence of a continuous belt of Late Paleozoic accretionary complexes in the western margin of both Patagonia and the Antarctic Peninsula has been repudiated in recent years, since these complexes are mainly Mesozoic in terms of deposition and metamorphism. This is consistent with paleogeographic models in which the Antarctic Peninsula lays west of Patagonia in prebreak-up times. This disposition is favoured by similarities in provenance between the late Early Permian to ?Late Triassic Duque de York Complex and Trinity Peninsula Group, which share sedimentological characteristics and U-Pb detrital zircon age patterns. After the Early Jurassic Chonide orogeny, the Antarctic Peninsula started to drift southwards, as indicated by paleomagnetic reconstructions of Weddell Sea ocean floor spreading, allowing the present-day margin of Patagonia to become progressively, from north to south, an actively subducting margin. In the Late Jurassic and Late Cretaceous, while the Antarctic Peninsula was drifting to its present position, turbiditic sedimentation took place at Hurd Peninsula, Livingston Island, previously considered to be Triassic in age, which has no equivalent in the Patagonian margin.

The new data presented here, combined with recent data and models from other authors, reveal two major geological problems to be resolved in the future: to identify a late Early Permian magmatic arc which shed detritus to both the Duque de York Complex and the Trinity Peninsula Group, and to resolve the apparent contradiction between left lateral post break-up movements in the Patagonian Andes, and right lateral displacements in the tectonic configuration of the Antarctic Peninsula.