The BMR regional seismic line across the Amadeus Basin, central Australia: implications for the tectonics of the Basin and for hydrocarbon exploration

Abstract

In 1985 the Bureau of Mineral Resources undertook deep seismic reflection and refraction profiling experiments across the Early Proterozoic to Late Palaeozoic Amadeus Basin and Arunta Block in central Australia. The experiments were designed to test various models of intracratonic basin formation which involved tectonic interaction with the surrounding basement. The seismic reflection results show the thrust belt at the northern margin of the Amadeus Basin to be dominated by a major, south-directed, basement thrust feature, the Redbank Thrust Zone, which was imaged to mantle depths. Other, more southerly, basement-cored thrusts appear to splay southwards from the Redbank Thrust Zone towards the Amadeus Basin. The seismic reflection results support a 'thick-skinned' Laramide or Wind River style of overthrusting for the final compressive Late Devonian-Carboniferous event, the Alice Springs Orogeny. It was the accumulation of thick, synorogenic conglomeratic sediments in a foreland-like setting at the time of thrusting that appears to have been the dominant control on maturation of the underlying Early Ordovician source rocks. In contrast to the northern margin, in the central and southern parts of the Amadeus Basin, the seismic reflection results indicate north-directed, 'thin-skinned' overthrusting on shallow detachments that were accompanied by Jura-style box folding. The detachments sole out in a salt horizon near the base of the succession. Major repetition of part of the succession has occurred, particularly at the leading northern edge of the overthrust region. Basement involvement at the southern basin margin is enigmatic, but appears to involve both Late Proterozoic and Devonian-Carboniferous tectonism.