Crustal architecture of central Australia based on deep seismic reflection profiling

Abstract

The crustal architecture of central Australia is interpreted from deep seismic reflection profiling conducted by the Australian Geological Survey Organisation in two surveys in 1985 and 1993. The seismic traverses, oriented normal to the main surface structures, ran north-south in central Australia, and crossed parts of the Arunta Block, Amadeus Basin, Musgrave Block and Officer Basin. The present crustal fabric was set in place by the end of the Mesoproterozoic (by about 1100 Ma). Reactivation of the structures took place in a continental intraplate setting mainly during the Middle-Late Palaeozoic Alice Springs Orogeny, but also during other orogenic events. In the Arunta Block. the crust is dominated by major north-dipping planar structures, interpreted as thick-skinned thrusts. Many of these thrusts cut deep into the crust, and at least one, the Redbank Thrust Zone, appears to cut and offset the Moho. In contrast, in the northern Musgrave Block, limited field mapping and teleseismic data suggest that the major crustal-scale planar structures are south-dipping. In the central to southern Amadeus Basin, deformation is essentially thin-skinned, with north-directed thrusting confined to the sedimentary succession. Thus, the deep seismic profiles in central Australia show a present day crustal architecture that is the response of the crust to Mesoproterozoic terrane amalgamation and to later reactivation by intraplate deformational events. Therefore. central Australia is a model for intraplate cratonic deformation that occurs in continental crust that is cold. thick and strong.