DETRITAL ZIRCON ANALYSIS OF PERMIAN VICTORIA GROUP SANDSTONES, CENTRAL TRANSANTARCTIC MOUNTAINS, ANTARCTICA

The Beacon Supergroup in the central Transantarctic Mountains represents the Gondwana sequence of Antarctica. It comprises inferred Devonian and Permian-Triassic strata. The latter were deposited in an intracratonic basin which evolved into a foreland basin in mid Permian time. Sedimentary petrology and paleocurrent data indicate that this basin had two major detrital sources, a granitic source inferred to be cratonic in origin and a volcaniclastic source that characterizes the upper Buckley Formation and younger Triassic beds. In order to investigate the sedimentary provenance further, detrital zircons have been examined from either flank of the basin. At Clarkson Peak, samples were collected from the lower (quartzose) and upper (volcaniclastic) Buckley Formation. At Mt. Bowers the complete Permian section, from pre-glacial to upper Buckley strata was collected. Results so far show varied zircon age provenance, reflecting multiple source regions. In all pre-upper Buckley samples there is a major age province in the 750-550 Ma range, corresponding to the overlapping Ross and Pan African orogenic events, and a subsidiary province of “Grenvillian” (1000 Ma range) age. There are minor additions from older Proterozoic sources. A major shift in paleoflow directions between the lower and upper Buckley at both localities is accompanied by a significant input of igneous zircon grains of Permian age, documenting contemporaneous magmatism and flooding of the basin with detritus from an active magmatic arc. This study seeks to define the Permian detrital zircon source regions and to relate them to outcrop geology and/or infer subglacial age provinces in East and West Antarctica.