Natural History of Australia - Precambrian

Precambrian

Three areas of the Australian landmass that are made of Archaean rocks are more than 2.5 billion years old, among the oldest rocks known to man. These igneous and metamorphic rocks are found in the Yilgarn (West) and Pilbara (North) cratons in today's Western Australia and the Gawler (South) craton which makes up the Eyre Peninsula in South Australia. During the Proterozoic, 2,500 to 545 Ma, continent building took place around the existing cratons; the accretions include sedimentary deposition of the banded iron formations and the formation of Australia's major orebodies - sources of gold, copper, lead, zinc, silver and uranium. These disparate landmasses are thought to have become associated by the tectonic collisions that formed the supercontinent Rodinia, between 1300 to 1100 Ma. Geological evidence suggests that the West Australian cratons collided first, followed by collision with the South Australian craton between ~830 and 750 Ma. The Centralian Superbasin formed the junction of the North, South and West cratons.

Rodinia broke up between 830 to 745 Ma; at around 750 Ma the western side of Rodinia called Laurentia broke away from the landmass made from Australia, India and Antarctica, forming a gap that would become the Pacific Ocean.

The Archean rocks from the Pilbara craton contain some of the first evidence of life, primitive cyanobacterial mats known as stromatolites. Soft-bodied organisms from the Ediacaran collectively known as the Ediacaran biota are found in sandstone around the Flinders Ranges in South Australia, notably at a site known as Wilpena Pound.