Australia: The Land Where Time Began

A biography of the Australian continent 

The Archaean Era (Archaeozoic) 4.5-2.8 Ga   

The Archaean has been divided into the following 3 stages by Shopf (1983), the time periods being set arbitrarily.

Early Archaean 4.5-3.3 Ga

The atmosphere and hydrosphere are believed to have formed, and the earliest rocks that have been preserved formed.

The Archaean was the time when the very first simple life forms are believed to have arisen. Throughout the Archaean all life was bacterial, the next stage in evolution not being reached until the Proterozoic.

By 3.5 Ga, in the Early Archaean, there were stromatolites growing, so there must have been living organisms that gave rise to the cyanobacteria of that time, and recently what are believed to be fossils of bacteria that metabolised sulphur, producing pyrite as a by-product, have been found in Western Australia. Throughout the Archaean stromatolites became increasingly abundant, declining in the Proterozoic.

Middle Archaean 3.3-2.9 Ga

Greenstone belts

Oxygen-poor atmosphere.

Late Archaean 2.9-2.5 Ga

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Sources & Further reading

1. Introduction to the Archaean

Neoarchaean Sulphate Concentrations in Seawater from Sulphur Isotopes in Massive Sulphide Ores