ABSTRACT: Triassic Depositional Environments in the Southeast Bowen Basin

KASSAN, JOCHEN, and CHRISTOPHER R. FIELDING, Department of Geology and Mineralogy, University of Queensland, Australia

The Permian-Triassic Bowen basin is a north-south elongate foreland basin to the New England foldbelt and forms part of the Sydney-Gunnedah-Bowen foreland complex. The Bowen basin is of significant economic importance as a major coal and hydrocarbon province. Parts of the Triassic succession form primary exploration targets for hydrocarbon reservoirs.

During the Triassic the Bowen basin evolved as a classical retroarc foreland basin, with the depocenter offset from the basin axis and in close proximity to a largely inactive volcanic arc (Camboon Volcanic Arc). Deposition along the eastern basin margin was influenced by the development of westward propagating thrusts, and uplift and erosion of the volcanic arc.

Detailed facies analysis of drill core and adjacent outcrop sections provides an insight in mechanisms of sediment accumulation in the area. Analysis of paleocurrent directions and isopach maps suggests a delicate interplay between detritus derived transversely from the orogen and axial drainage systems. Dispersal patterns are documented by the stratigraphic distribution of paleocurrent directions and by pebble counts of subsurface conglomerate sections penetrated in drill core. Differences in sediment provenance and depositional style between the northern and southern part of the study area are evident. In particular the predominance of thick conglomerate sequences and the much more lithic composition in the southern part of the area are conspicuous. This is interpreted to reflect th direct influence of contemporaneous structuring on sediment accumulation.

AAPG Search and Discovery Article #91015©1992 AAPG International Conference, Sydney, N.S.W., Australia, August 2-5, 1992 (2009)