Geological history and stratigraphy of northern Victoria Land

Abstract

Sedimentary successions in the central Transantarctic Mountains (CTAM) and Victoria Land can be subdivided into two representative units. The first unit formed by the early Paleozoic tectonic processes of the Ross Orogeny with the Precambrian metamorphic rocks being the basement. The Beardmore and Byrd groups which consist of shallow marine sandstone, mudstone, and lesser amounts of carbonates represent the early Paleozoic units in the CTAM. On the other hand, the early Paleozoic Ross Orogeny-related successions in the Northern Victoria Land (NVL) are characterized by accretionary complexes of three terranes: Wilson, Bowers,Robertson Bay terranes, from inboard to outboard. The Wilson Terrane consists of high-grade metasedimentary rocks and granitoids. The Bowers Terrane comprises low-grade metasedimentary rocks of siliciclastics, volcanics,and carbonates. The outermost Robertson Bay Terrane consists predominantly of flysch deposits of deep-sea turbidite. No early Paleozoic succession occurs in the Southern Victoria Land (SVL). Afterwards, the late Paleozoic to Triassic Beacon Supergroup (siliciclastics including coal seams) formed over the deformed early Paleozoic strata,bounded below by a regional unconformity. There are minor unconformities within the Beacon Supergroup in the CTAM, the hiatus and resulting unconformities increase in frequency and duration toward NVL. Both the Devonian Taylor and Permian-Triassic Victoria groups occur in the SVL, but only the Victoria Group occurs in the NVL. The Victoria Group consists of shallow marine, fluvial, and volcaniclastic successions. The deposition in the Pacific margin of the Gondwana stopped after the formation of the Victoria Group. Afterwards, the geological processes in the TAM were dominated by regional development of volcanics and lava flow units of Ferrar Group. It is effusive and eruptive tholeiitic volcanics which formed thick succession of volcaniclastics, lava flow units, dykes, and sills.These volcanics are related to the rifting in the early stage of the breakup of the Gondwana.