Australia: The Land Where Time Began

A biography of the Australian continent 

Jurassic Sedimentary and fossil successions in Australia¹ - Current and future prospects for marine and non-marine correlation.

Jurassic age deposits are widespread across the Australian continent, mostly of terrestrial origin. The known marine strata from the Jurassic exposed on land in northwestern and central-western Australia are of limited area, though there are thick offshore marine sequences on the North West Shelf. The dingo Claystone at the southern end of the shelf is an important source rock for oil and gas, and it is here that the richest petroleum province in Australia is situated. Non-marine deposits, that include economic coals, are, by and large, distributed in the eastern states. Regarding the Australian sedimentary succession Jurassic stage boundaries are mainly constrained poorly. According to the authors¹ improved correlation across the basins of Australia, with overseas successions has been improved on the basis of new studies of microfossils, plants, fish, and zircon dating, and recent IUGS timescales.

In several basins Australian basins there are extensive deposits of Jurassic age. The Jurassic deposits in the west are in the Bonaparte Basin, Canning Basin, Carnarvon Basin and Perth Basin, all onshore basins, and in the Westralian Superbasin that includes The northern section of the Bonaparte Basin, Browse Basin, Roebuck Basin and the northern section of the Carnarvon Basin. Deposits of Jurassic age in eastern and central eastern Australia have been found in the Laura Basin, the Carpentaria Basin, Eromanga Basin, Surat Basin, Mulgildie Basin, Clarence-Moreton Basin and Nambour Basin. In South Australia they have been found in the Polda Basin and Bight Basin and isolated deposits on the Leigh Creek Coal Measures of Rhaeto-Liassic age. The oldest deposits of the Otway and Gippsland basins in southern Australia, are suggested to be from the latest Jurassic (Burger & Shafik, 1996).The successions have mostly been deposited in fluvial sedimentary systems.

At the beginning of the period, largely during the Hettangian, there were widespread hiatuses in the deposition, occurring again in the latest Middle Jurassic-early Late Jurassic. In the western part of the Clarence-Moreton Basin of eastern Australia, as well as basins further west, the unconformity is present, but a complete section across the system-period boundary appears to be present in the eastern part of the Clarence Moreton Basin (McKellar, in press). The geographic and stratigraphic extent of these hiatuses is not well defined. The Upper Jurassic is also represented by a hiatus in places such as the Surat and Eromanga basins. There are no Upper Jurassic strata in basinal areas on or near the margin of the continent. In the northern part of the Clarence-Moreton Basin and the northern part of the Nambour Basin the hiatus extends to the Middle to Late Jurassic and in the southern part of the Nambour Basin  to the late Early Jurassic (e.g. McKellar, in press).

During the Early to Middle Jurassic coal measures formed in forest mires that developed into coal deposits. The Walloon Coal Measures, an important source of thermal coal, deposited in the Clarence-Moreton and Surat basins and coal seam gas in the Surat Basin, exploited since 2006.

Sources & Further reading

  1. Turner, S., Bean, L.B., Dettmann, M., McKellar, J. L., McLoughlin, S. & Thulborn, 2009; Australian Jurassic sedimentary and fossil successions: current work and future prospects for marine and non-marine correlation, GFF, Vol. 31, (Pt 1-2, June), pp 49-70. Stockholm, ISSN 1103-5897

 

Author: M. H. Monroe
Email:  admin@austhrutime.com
Last updated 04/08/2012
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                                                                                           Author: M.H.Monroe  Email: admin@austhrutime.com     Sources & Further reading