Revision of the Terrane Model of Northern Victoria Land (Antarctica)

During the joint German-Italian Antarctic expedition 1999-2000, new tectonic results triggered a revisiting of the classic terrane model for northern Victoria Land which postulated three terranes, the high-grade Wilson Terrane and the very low-grade to low-grade Bowers and Robertson Bay terranes. The brittle character of the former terrane boundaries was studied in detail and it was shown, that Meso- to Cenozoic brittle to semi-brittle tectonics has overprinted the inherited Early Palaeozoic structural pattern to a large extent. In addition to a revision of the Ross-orogenetic pattern in northern Victoria Land, the tectonic history and the arguments for a simple three-terrane model were questioned. A new model is proposed, which accepts the allochthonous character of arc volcanics and sediments, now called the Bowers Arc Terrane. These Bowers Arc rocks collided due to W-directed subduction processes with the Wilson active margin of Gondwana. As it is not yet proven that the Wilson plutonic and metamorphic rocks form a distinct terrane themselves, the term Wilson Terrane is abandoned consequently in favour of the newly suggested Wilson Mobile Belt. In addition, there are no proofs that the metasedimentary rocks of the Robertson Bay Group metasedimentary rocks docked as a separate terrane to the Bowers Arc Terrane. These turbidites were deposited after docking of the Bowers Arc and represent the continued sedimentary history in an accretionary environment at the Gondwana active margin.