Lithospheric Framework of Australia

Abstract

The Australian continent comprises an amalgamation of cratonic elements onto which there has been significant Phanerozoic accretion in the east. The result is a complex lithospheric structure with a broad span of ages of material at the surface. The continent is moving rapidly to the north at c. 7 cm/yr, relative to Asia. The collisions with the Eurasian and Pacific plates to the north, coupled to the interaction with the Pacific Plate along the eastern plate boundary through Tonga and New Zealand result in a complex pattern of stresses that is reflected in a moderate rate of intra-plate earthquakes. Extensive geophysical investigations at a continental scale have revealed details of the nature of the lithosphere. The lithosphere is thick (200 km or more) and seismically fast beneath the Precambrian domains of the centre and west of Australia and thins to the east, in a series of steps, to c. 80 km in the Tasman Sea. Large gravity anomalies in the centre of the continent attest to complex deformation in the Phanerozoic that has left a residue of domains with rapid changes in crustal thickness. The development of Australia's generally thick lithosphere has exerted fundamental control on the overall tectonic stability and consequent landscape evolution, the distribution of earthquakes and associated seismic risk, the evolution of sedimentary basins, as well as heat flow and other resource endowment.