Provenance of the Coastal Sands of the Western Scotia Plate: Tierra del Fuego and Antarctic Peninsula

Abstract

The Scotia Plate is interacting between the South American and the Antarctic plates. The original plate has been subdivided in relation to new studies that recognized an active oceanic ridge that separate it from the Sandwich Plate. At the same time, the Shackleton Fracture Zone separates it into two other small plates: the Drake and the South Shetland plates. All these plates are mostly of oceanic composition with a small portion of continental crust emerging at the northwestern corner, at the south of the Fuegian Archipelago. Most of the emergent areas of these plates have been repeatedly glaciated during the Quaternary, although the last glaciation was not so extended as in the Northern Hemisphere. In order to get light about rock provenance, beach and coastal sands were collected and analyzed in their mineral composition, assuming that they are indicating the geotectonic setting. Quartz, lithic fragments and plagioclases are dominant at the Atlantic coast of the Isla Grande de Tierra del Fuego. These sediments have been transported by piedmont glaciers from the Darwin Cordillera. On the other hand, and due to their volcanic origin, opaque minerals are dominant at the beaches of the South Shetland Islands, and less common at the Antarctic Peninsula. To the north and south of the Scotia Plate, there is an important contribution of metamorphic minerals (garnets). These contributions are related to the Patagonian Batholith at Beagle Channel, and to those rocks outcropping at the South Orkney Islands and the Antarctic Peninsula.