Enhanced magnetic and gravity imaging of the crustal basement beneath the northern Wilkes Subglacial Basin in East Antarctica

The Wilkes Subglacial Basin (WSB) is one of the largest tectonic features in East Antarctica as it stretches for almost 1600 km from the Southern Ocean towards South Pole. Significant research has focussed on the tectonic origin of the basin with competing models ranging from Paleozoic, Mesozoic and Cenozoic extensional models to flexural models related to the Cenozoic uplift of the Transantarctic Mountains. Comparatively little effort has however been placed on investigating the cryptic basement of the WSB despite its key location at the transition between the exposures of the Archean-Mesoproterozoic Terre Adelie Craton and the late Neoproterozoic to Ordovician age Ross Orogen.

Here we present enhanced aeromagnetic and airborne gravity imaging augmented by satellite magnetic and satellite gravity data and comparisons with formerly adjacent southeastern Australia to redefine key features of the basement in the northern WSB region.

We show that a prominent magnetic low located beneath the Western Basins within the WSB is not caused by a ca 3 km thick Cambrian rift basin as previously proposed (Ferraccioli et al., 2009, Tectonophysics) but images instead a linear Archean crustal ribbon extending further north to exposures of Archean rocks in the Terre Adelie craton and in the Gawler Craton. Cambrian sedimentary basins are confirmed further east beneath the northern Central Basins. Prominent magnetic highs along the eastern flank of the WSB and at the edge of the southern Central Basins were previously interpreted to reveal Ross age igneous basement associated with an arc-back arc system. However, the occurrence of longer wavelength satellite magnetic anomalies both in the WSB and at the edge of the Gawler Craton and in the Curnamona Craton in Australia lead us to propose an alternative hypothesis that predicts the occurrence of more extensive Paleo to Mesoproterozoic basement than previously inferred. Furthermore, a prominent linear residual gravity anomaly along the western flank of the WSB is interpreted here as reflecting uplifted mafic lower crust associated with Paleoproterozoic rifting. High amplitude aeromagnetic anomalies may reflect coeval banded iron formations associated at shallower crustal levels with such Paleoproterozoic rifting processes.

By comparing gravity signatures over the WSB and southern Australia and by incorporating recent seismic constraints at the transition between the Gawler Craton and the Delamerian Orogen we reassess the extent and architecture of both the Precambrian and Cambrian basement.

Overall, our results and models have significant implications for tectonic studies of the basement of the WSB, including better defining the role of inherited tectonics structures on the more recent  Paleozoic, Mesozoic to Cenozoic evolution of the WSB. Furthermore, the larger degree of heterogeneity in the crustal basement identified here will help inform next generation models of intracrustal contributions to geothermal heat flow  beneath this key sector of the East Antarctic Ice Sheet.