New study targets modelling crust and lithosphere heterogeneity in the Wilkes Subglacial Basin of East Antarctica

Abstract:

The Wilkes Subglacial Basin (WSB) stretches for ca 1600 km from the George V Coast towards South Pole. Understanding the heterogeneity in subglacial geology and deeper crustal and lithosphere structure beneath the WSB is critical to advance our understanding of the boundary between the Archean to Mesoproterozoic Mawson Craton and the ca 550-500 Ma Ross Orogen. Quantifying geological boundary conditions is also pivotal to better constrain geological influences on the long-term stability of the East Antarctic Ice Sheet (EAIS) in the WSB- one of its largest marine-based and hence potentially more unstable sectors.

A wide basin formed in the WSB region in response to far-field subduction along the retreating Paleo-Pacific margin of West Antarctica in Permo-Triassic times; Jurassic extension followed, leading to emplacement of huge volumes of Jurassic tholeiites. The region was then affected by intraplate Mesozoic to Cenozoic(?) extension and formation of narrow graben features. Cenozoic flexure in response to Transantarctic Mountains uplift and glacial erosion then shaped the modern landscape of the WSB.

Within the 4D Antarctica project of ESA that aims to quantify the spatial variability in subglacial geothermal heat flux, we present the first results of 3D geophysical modelling aimed at quantifying geological heterogeneity in the WSB. New aerogeophysical data compilations and crustal and lithosphere thickness estimates from 3D satellite gravity modelling provide the starting point.

We model a major lithospheric-scale boundary along the eastern margin of the WSB, separating the Ross Orogen from a composite Precambrian Wilkes Terrane. Precambrian basement is modelled as both shallower and of more felsic bulk composition along our second crustal model further south. Although the lack of drilling precludes direct sampling of this crustal basement, aeromagnetic anomalies suggest it may be akin to late Paleoproterozoic to Mesoproterozoic igneous basement exposed in South Australia.

Collectively, first order differences in basement depth, bulk composition and metasediment/sediment cover likely give rise to significant heterogeneity in geothermal heat flux beneath different sectors of the WSB- an hypothesis that will test further with the development of new thermal models for the region.