Wed 28th October @ 12 pm, Rm 312.222

Abstract

The geotectonic history of the interior of East Antarctica is poorly known due to limited bedrock exposure and patchy geophysical imaging. Outcrop of the Nimrod Group in the adjacent central Transantarctic Mountains reveals a crustal history beginning by 3.1 Ga, with significant additions at ~2.5 and ~1.7 Ga, followed by pervasive thermomechanical overprinting within the active-margin Ross Orogen at ~500 Ma. Because of the limited outcrop, valuable new evidence is provided by indirect ‘sampling’ of the ice-covered basement with airborne potential-field geophysics, detrital zircon geochronology, sampling of basement clasts from glacial moraines, and geochemical exchange between Ross-age granitoids and older basement. In particular, sampling of glacial moraine clasts at the edges of large catchments eroding the interior, and isotopic signatures from late orogenic granitoids can provide useful constraints on the otherwise covered subglacial geology. Together, these approaches provide evidence for a rich, previously unknown Archean and Proterozoic crustal history of the East Antarctic shield that has close ties to both Australia and Laurentia.