Australia: The Land Where Time Began

A biography of the Australian continent 

Proterozoic Australia and Cainozoic Antarctica - Association of Sulphate Evaporites, Stromatolitic Carbonates and Glacial Sediments

According to the authors¹ the occurrence of dolomite and limestone beds within and immediately overlying many glacial deposits (tillites) from the Late Proterozoic has been a source of controversy for a long time, as carbonate sediments are often considered to be diagnostic of warm water environments. It has also been usual to consider stromatolites as indications of warm water. In this study the authors¹ describe 2 examples where stromatolites occur together with barite at the top of a glacial sequence from the Late Proterozoic in the Amadeus and Ngalia Basins in central Australia. The authors¹ suggest interpretation problems may be largely resolved following examination of data that has been published on lakes in Antarctica. Highly saline lakes in Antarctica occupy enclosed glacial basins in the Vestfold Hills, and the Taylor and Wright Dry Valleys, with Lake Bonney being the example that has been the most comprehensively described. In lakes in cold arid climates it is common to find carbonate sediments, sulphate evaporites and stromatolites. The stromatolitic mats and the cyanobacteria that construct them are similar to those that have been described from warmer climates. In northern parts of Canada and Siberia, the coastal lagoons and the plains and lakes of the tundra are suggested by the authors¹ to be better geomorphic analogues for the deposits from the Proterozoic, and these also seem to contain sediments that are analogous, though there are not more than brief descriptions available. The authors¹ suggest environments such as these are modern analogues of the associations between carbonates, stromatolites and evaporites and glacial sediments of Proterozoic age.

Sources & Further reading

1. Walter, M. R., and J. Bauld. "The Association of Sulphate Evaporites, Stromatolitic Carbonates and Glacial Sediments: Examples from the Proterozoic of Australia and the Cainozoic of Antarctica." Precambrian Research 21, no. 1–2 (7// 1983): 129-48.