Polyphase Brittle Tectonics in North Victoria Land and Gondwana Fragmentation

Antarctica was at a centre position within Gondwana and holds a key position for any plate tectonic reconstruction related to its break-up history. North Victoria Land (NVL) is located at the Pacific end of the Transantarctic Mountains (TAM), which represent the uplifted western shoulder of the West Antarctic Rift System. The basement of the TAM formed during subduction of the Palaeopacific Ocean under E Gondwana during the Ross Orogeny. Major uplift of the TAM commenced around the Eocene-Oligocene boundary following sediment accumulation within the wide “Mesozoic Victoria Basin”. This long-lasting geological history led to highly anisotropic crust that is susceptible to repeated reactivation. We present evidence for a polyphase structural evolution of NVL after initial break-up of Gondwana at ca. 180 Ma coeval with the Ferrar volcanic event. Mainly Neogene NW-SE striking dextral strike-slip tectonics with local transtension and transpression controls the present structural architecture of NVL. It may be interpreted as dynamic response to intra-oceanic fracture zones between Australia and Antarctica extending into NVL and the Ross Sea. Dextral strike-slip overprints two older increments: (i) WNW-ESE striking sinistral tectonics of possibly late Mesozoic-early Paleogene age within a transform margin setting between Australia and Antarctica, (ii) ENE-WSW directed extension of NVL continental crust possibly coeval to Adare Trough spreading in Eocene-Oligocene times.