Proterozoic geology of Australia and palaeomagnetism

Abstract

The significance of palaeomagnetism, to correlation and tectonic analysis of the Proterozoic of Australia, is discussed in terms of the integrity of the Australian Proterozoic apparent polar wander path (APWP). About half of the poles which presently define the Australian Proterozoic APWP come from a study of the McArthur Basin. This study defines a 100 Myr APWP segment, comprising a loop and a switchback, that spans about one-sixth of the total angular length of the 1250 Myr Proterozoic APWP. The McArthur segment contrasts with the sparsity of data elsewhere in the Proterozoic, where the APWP is defined from only a few small studies through stratigraphic sequences and from studies of widely scattered, isolated mafic intrusions. While the McArthur study demonstrates the potential for quite precise correlation, it highlights the need to derive the Proterozoic APWP from detailed studies through continuous stratigraphically-controlled sequences. Correlation elsewhere is presently possible only within the broadest of limits. Although only a single APWP, and therefore a unified Australian Precambrian Shield throughout the Proterozoic, can be inferred from the present APWP alone, inadequacies in the database do not preclude significant departures from this idealised path. Significant relative movements between individual component blocks of the Precambrian Shield cannot yet be entirely excluded. The best potential for refining the Australian Proterozoic APWP lies in further detailed stratigraphically-controlled studies of the Kimberley, Victoria River, Birrindudu, Amadeus, Nabberu, and Bangemall Basins, the Gawler Craton and Adelaide Geosyncline, and still-to-be sampled parts of the McArthur Basin.