The Permo-Triassic Gondwana sequence, central Transantarctic Mountains, Antarctica: Zircon geochronology, provenance, and basin evolution

Abstract

The most complete Permian-Triassic Gondwana succession in Antarctica crops out in the central Transantarctic Mountains. The lower Permian strata were deposited in an intracratonic basin that evolved into a foreland basin in late Permian time. Sedimentary petrology and paleocurrent data have been interpreted as indicating a granitic (craton) provenance and a West Antarctic volcanic provenance. To address the West Antarctic provenance and evolution of the detrital input, detrital-zircon grains from nine sandstones (plus three sandstones reported previously) representing the full extent of the Permo-Triassic succession exposed on that flank of the basin, have been analyzed by sensitive high-resolution ion microprobe. Results define three provenances: an early (early to middle Permian) provenance that is dominated by zircons having Ross orogen ages (600-480 Ma); a middle (late Permian) provenance dominated by Permian zircons with subordinate older magmatic arc grains plus lesser Ross orogen-age grains; and a late (Triassic) provenance, which is quite variable and in which the predominant Triassic arc component ranges from very minor to significant and again with a component of Ross orogen- age grains. Detrital zircons imply a more extensive Permo-Triassic arc, in time and space, on the Gondwana margin than is evident from outcrop data. The zircon data are integrated into a model for basin evolution and infilling, providing broad constraints on the timing of tectonic events and the provenance.