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

The Beacon Supergroup in the central Transantarctic Mountains, the Gondwana sequence of Antarctica, comprises Devonian(inferred) 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 cratonic source and a volcaniclastic source that characterizes the upper Buckley Fm and younger Triassic beds. In order to investigate the sedimentary provenance further, detrital zircons have been examined from both flanks of the basin. At Clarkson Peak, samples were collected from the lower (quartzose) and upper (volcaniclastic) Buckley Fm. At Mt. Bowers the complete Permian section, from pre-glacial to upper Buckley strata was collected. Results show varied zircon age provenance, reflecting multiple source regions. In all pre-upper Buckley samples the major zircon province is in the 750-550 Ma age range, corresponding to overlapping Ross and Pan African orogenic events, with a subsidiary province of Grenville-age, ~1000 Ma. These age range variations reflect the influence of multiple sub-provinces. There are also minor contributions from older Proterozoic sources, including a ~1500 Ma source that waned in Fairchild time and is nearly absent in the Buckley Fm. These older Proterozoic zircons are likely sourced from the coast of East Antarctica. A major shift in paleoflow directions between the lower and upper Buckley at both localities is accompanied by a significant input of Permian-age igneous zircons, documenting contemporaneous magmatism and flooding of the basin with detritus from an active magmatic arc. There is also a minor input of ~370 Ma grains which were most likely sourced from Devonian granitoids in West Antarctica.