Tracking crustal thickness at the sediment inundated edge of the Gawler Craton, South Australia

Abstract

In this study, using two recent passive seismic deployments across the Gawler Craton and Lake Eyre Basin, South Australia, we aim to examine the nature and extent of a perceived Moho offset (∼15 km) between the two regions using receiver functions. Together the two arrays straddle the edge of the Gawler Craton and present a unique opportunity to understand the crustal thickness variations in a hitherto under-explored region. The task is complicated however by many stations situated atop low-velocity sedimentary rocks, inducing high-amplitude low-frequency reverberations in the receiver function signal, and masking the signal from crust to mantle conversions. We, therefore, employed a resonance removal filter to dampen the sediment reverberation effect which aided the detection of the P-to-S conversion from the Moho. The obtained Moho depths dramatically increased the coverage in observations, particularly in areas inundated by Phanerozoic sediments. We detect the presence of thicker crust beneath the Lake Eyre region than previously imaged (∼40 km), that hints towards a shared Proterozoic provenance with building blocks of the South Australian Craton, such as the Curnamona Province. The Moho phase is consistent (∼46 km) and clear beneath the Gawler Craton, indicating a contrast with stations in the Lake Eyre region, although the difference with respect to previously reported crustal thickness is now substantially reduced. Our results thus illuminate the crustal structure of an important junction within continental Australia and provide valuable constraints for models of the tectonic evolution of eastern Gondwana and the assembly of Proterozoic Australia.