Probabilistic Cover‐Basement Interface Map in Cloncurry, Australia, Using Magnetotelluric Soundings

Abstract

A great interest has been shown by the Australian geoscience community to define the depth to crystalline basement. With the Australian continent being covered by sedimentary sequences in 80% of its surface (e.g., Kennett et al., 2019), the characterization of the cover-basement interface is essential to mineral, energy, and groundwater exploration. Drilling provides the most reliable source of information to estimate the depth to basement and gives first-order information on the nature of the geological formations, in terms of lithology and petrophysics. However, drilling dataset can have an irregular and/or sparse coverage, generally biased toward certain types of geology according to past exploration strategies. Geophysics, by contrast, is generally regularly sampled, covers wide areas and provide continuous images of the subsurface, making it less influenced by sampling bias. Its limitation is that it has less resolution and the models derived through inversion are non-unique and interpretations are subject to ambiguity.The contact between the unweathered basement and cover sequences often presents a clear contrast in the petrophysical properties of the rocks, in particular for the electrical conductivity, or its inverse, the electrical