Tectonic origin of the Wilkes Subglacial Basin unveiled

The Wilkes Subglacial Basin (WSB) is a largely unexplored, ~1400 km-long and up to 600 km-wide depression underlying the East Antarctic Ice Sheet. An extensive aerogeophysical survey was recently flown in the hinterland of northern Victoria Land to explore the WSB, and included collection of new airborne radar, aeromagnetic and aerogravity data. Previous models for the origin of the basin suggested Cenozoic flexure linked to uplift of the Transantarctic Mountains, distributed crustal extension of unknown age (possibly Mesozoic and or Cenozoic), and Ross-age(?) compression. Our aerogeophysical data reveal that the eastern margin of the basin is imposed upon major thrust faults of the Ross Orogen, which may have been partially reactivated in the Cenozoic, as an intraplate strike-slip fault belt. Aeromagnetic patterns indicate that the western margin of the basin is also structurally controlled and appears to be imposed upon a Proterozoic-age shear zone, mapped in the Mertz Glacier. A prominent gravity anomaly along the western margin of the basin is modelled as caused by thick mafic intrusions that were emplaced along the leading edge of the craton, perhaps in response to later Neoproterozoic rifting. A linear aeromagnetic low corresponds to this gravity high, and is interpreted to reflect the overlying sediments deposited along the rifted margin of the craton. As observed in southern Australia, the WSB region evolved from a rifted margin in the Neoproterozoic to an active margin in the Cambrian. Magnetic intrusions within the WSB are interpreted as Ross-age back-arc plutons that formed during westward subduction along the active margin of Gondwana. The hypothesis for a Ross-age back-arc basin in the WSB is supported by the occurrence of low-grade metasediments of back-arc affinity in Oates Land, and by the similarity in magnetic anomaly signatures over the WSB and the back-arc mobile belt of the North American Cordillera.