CHAPTER 1 - The Precambrian Systems

Abstract

This chapter provides an overview of the Precambrian systems. Rocks of Precambrian age outcrop over large areas of Australia, principally in Western Australia, South Australia, and the Northern Territory, and are known from all States except Victoria. A wide variety of lithologies is represented, including essentially unmetamorphosed sandstones, shales, and dolomites, acid to basic volcanics and intrusives, and highly deformed schists and gneisses of sedimentary and igneous derivation. Probably, the most striking feature of the Australian Precambrian is the widespread occurrence of thick sequences of sedimentary and volcanic rocks, up to about 2300 m.y. old, in a state of preservation comparable to that typical of Phanerozoic shelf sequences. The oldest subdivision of the Precambrian, the Archean, in Australia has not yet been subdivided into time-rock units. Of the Proterozoic systems, the two youngest have been named and defined; however, there has been no formal definition or local name published for the oldest. Only the youngest system has been formally subdivided into series.