Rifted(?) crust at the East Antarctic Craton margin: gravity and magnetic interpretation along a traverse across the Wilkes Subglacial Basin region

Early geophysical studies hypothesized a continental rift structure beneath the Wilkes Subglacial Basin. Recent models favour a flexural origin for th e basin linked to Transantarctic Mountains uplift and to East Antarctic Cra ton lithospheric rigidity. Flexural modelling predicts crustal thickening b eneath the basin. Gravity modelling along the International Trans-Antarctic Scientific Expedition traverse (1998/99), however, reveals crustal thinnin g beneath the basin. At 75 degreesS the crust thins from 37 km beneath the Transantarctic Mountains to 31 +/- 2 km beneath the Wilkes Basin. The weste rn flank of the basin features a sharp magnetic break. This signature may a rise from a fault separating highly magnetic Precambrian craton crust from weakly magnetic Neoproterozoic(?) crust. Much later crustal extension may h ave focussed along the craton margin, The eastern flank of the Wilkes Basin exhibits a prominent aeromagnetic signature. Potential field modelling pre dicts 1-4 km thick sedimentary infill within the Wilkes extended terrane, i nterpreted mainly as Beacon Supergroup intruded by Jurassic Ferrar tholeiit es. The adjacent Adventure Subglacial Trench is a narrow rift basin with 25 +/- 5 km thick crust and a 10 +/- 4 km sedimentary infill. (C) 2001 Elsevi er Science BN. All rights reserved.