--> ABSTRACT: Crustal Structure of the North West Shelf (Australia) and Its Implications for Petroleum Exploration, by J. B. Colwell, H. M. J. Stagg, P. A. Symonds, J. B. Willcox, G. W. O'Brien; #91020 (1995).

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Crustal Structure of the North West Shelf (Australia) and Its Implications for Petroleum Exploration

J. B. Colwell, H. M. J. Stagg, P. A. Symonds, J. B. Willcox, G. W. O'Brien

A set of 30 000 km of deep (14 - 16 second record length) regional, seismic reflection data recorded by the Australian Geological Survey Organisation over the last four years provides a unique insight into the structural framework and development of Australia's North West Shelf hydrocarbon province. Although most of the North West Shelf has been influenced by similar tectonic events, particular areas have responded differently to the prevailing regional stress fields. These differences are well illustrated in a series of margin-wide 'strike' and 'dip' profiles.

The data indicate that basin subsidence and structuring, and hence petroleum system distribution, have been compartmentalised by a number of major crustal boundaries and accommodation zones. In the Late Devonian to Early Carboniferous, upper and lower crustal extension produced a series of intra-cratonic rift basins linked by complex accommodation zones. A major episode of extension and thinning in the mid-Carboniferous to Early Permian to the west of the intracratonic rifts produced the thick depocentres of the Westralian Superbasin; this thinning is interpreted to have taken place principally in the lower crust/upper mantle and produced sag-style Permo-Triassic deposits lacking clear syn-rift relationships.

The major tectonic event with implications for petroleum generation and entrapment took place in the Late Triassic/Early Jurassic and involved transpressional reactivation to produce the major Jurassic source-rock depocentres. Almost all of the known major hydrocarbon accumulations of the province occur over or adjacent to these depocentres.

AAPG Search and Discovery Article #91020©1995 AAPG Annual Convention, Houston, Texas, May 5-8, 1995