Australia: The Land Where Time Began

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Adelaidean (Late Proterozoic) Basins in Australia - Stratigraphy, Correlation and Sedimentary History

The Precambrian part of the thick sequence in the Adelaide Geosyncline (its stratotype basin),South Australia, represents the Adelaidean (Late Proterozoic) time. Other intracratonic and epicratonic basins that extend northwards across Australia record comparable Adelaidean sedimentation, that included glaciogenic sediments.

To the east of the Gawler Craton and its cratonic platform cover (the Stuart Shelf), the Adelaide Geosyncline, up to 15 km of sediments accumulated, that were mainly of shallow-water origin, part of which were in intracratonic troughs and possibly partly on a miogeoclinal continental shelf. The earliest sedimentation that was associated with rifting and basic volcanism, has an estimated age of 1,100 Ma. Beginning with basal blanket sands, shelf carbonates and basic volcanics that were followed by mixed carbonates, clastic and evaporitic beds, (callanna beds). The overlying Burra Group, consisting of a number of west-derived, possibly deltaic cycles and platform carbonates bearing magnesite. The Umberatana Group, of late Adelaidean age, that overlies it unconformably, contain the lower glacial beds (that includes the Sturt Tillite), interglacial siltstone that has been dated to about 750 Ma, and carbonate, and the upper glacial beds. Wilpena Pound, that is post-glacial, begins with a distinctive 'cap' dolomite above the upper glacials and contains clastics, that are mainly fine to medium, and the Ediacaran metazoan assemblage.

In the Officer, Amadeus, Ngalia and Georgina Basins of central Australia and in the Kimberley Region, Western Australia, sedimentation patterns of Late Adelaidean age are similar enough to suggest a link between them and the Adelaide Geosyncline in the south. The early Adelaidean sequence is younger than about 1.5 Ga in the Amadeus Basin, though it cannot be correlated directly with formation of the Adelaidean Geosyncline of early Adelaidean age. The late Adelaidean and younger sequences are however, easily correlated. These include the Areyonga Formation, of lower glacial age, and the Arumbera Sandstone I that contains elements of the Ediacaran assemblage. Mainly sequences of late Adelaidean age are present in the Georgina and Ngalia Basins, that include thick glacials, can be mostly correlated with the Amadeus basin.

Clastics of earliest Adelaidean age in the Kimberley Region are suggested by the authors1 to possibly be represented, but only the glaciogenic and associated sediments of late Adelaidean age can be correlated with confidence, the tillites commonly overlying glacial pavements. A graben is the only place where the lower glacials are represented, while the upper glacials and succeeding sequences have been found to be more widespread. A date of about 670-640 Ma has been found for the post-glacial shales.

In the Bangemall Basin, Western Australia, the dominantly carbonate and clastic sequences cannot be directly correlated with any type Adelaidean, though an earliest Adelaidean age of 1050 Ma is suggested by geochronology.

Sources & Further reading

  1. Preiss, W. V., and B. G. Forbes. "Stratigraphy, Correlation and Sedimentary History of Adelaidean (Late Proterozoic) Basins in Australia." Precambrian Research 15, no. 34 (10// 1981): 255-304.
Author: M. H. Monroe
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Last updated 04/08/2013
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                                                                                           Author: M.H.Monroe  Email: admin@austhrutime.com     Sources & Further reading