Geology and Petroleum Potential of the Clarence-Moreton Basin, New South Wales and Queensland

The Triassic to Jurassic Clarence-Moreton Basin presented many challenging problems when it was first proposed for study in the Onshore Sedimentary Basins Program of the then Bureau of Mineral Resources (since renamed Australian Geological Survey Organisation, AGSO). Covering about 27 000 km2 , and containing up to 3 km of dominantly continental sediments (see Fig. 1 of Wells &amp; O'Brien, this Bulletin, p. 4),  the basin was little understood before this study. No comprehensive basinwide synthesis had ever been undertaken, and the regional stratigraphic framework of the basin was unknown.
The predominantly fluvial sediments include important coal measures. These were considered to be a potential hydrocarbon source, although there had been no up-to-date assessment of petroleum source rocks and petroleum potential, and data on which to base a meaningful sedimentological analysis were limited. The main aim of the project was, therefore, to understand the evolution of the basin. This was to be achieved principally through sedimentological research, and by interpretation of industry seismic surveys, and an AGSO deep-crustal seismic study. Most of the objectives of the project were achieved,  and the major results are documented in the papers in this Bulletin. Other papers  reporting results of the research are listed in the references at the end of each paper.   A folio of maps, which includes isopachs, structure contours, potential fields, and locality maps,  is being produced as a separate publication. A major research interest to be addressed during the project was the interaction of tectonics, climate and sea level, and its effect on patterns of sedimentation, sediment provenance, dispersal and composition in the basin. Distinguishing the effects of eustatic sea-level change on the history of sedimentary basins from those caused by tectonic events is a major problem in many sedimentary provinces. The succession in the Clarence-Moreton Basin includes an important marker bed of ferruginous oolite, which in some sections includes acritarchs. The origin of the oolite was an enigma, and it was hoped that research into its origin would substantiate its usefulness as a marker  zone, and help in understanding the relative merits of eustatic sea level changes versus tectonic events in stratigraphic  interpretation. The geological investigations of the Clarence-Moreton Basin concentrated chiefly on the Bundamba Group,  a Late Triassic to Early Jurassic succession; the name had been originally used for the largely coal-barren sediments sandwiched between the Ipswich Coal Measures below and the Walloon Coal Measures above. The Bundamba Group covers a large area, and posed major problems in nomenclature and correlation from one end of the basin to the other, besides containing potential petroleum source rocks. Of the overlying formations, the Kangaroo Creek Sandstone and Grafton Formation were not studied in detail, as they have little petroleum potential and no particular problems of nomenclature. However, the Walloon Coal Measures, although they have almost no natural outcrop, contain petroleum source rocks, and were included in the organic geochemistry program.

Tags: AU-NSW, AU-QLD, Bulletin, Earth Sciences, GA Publication, Published_External, geology
Organization: Geoscience Australia Data