The Mesozoic Geological Evolution And Regional Hydrocarbon Potential Of The North-West Shelf of Australia.
O'Clery, Mark D.H.
Honours Degree, 1986
University of Adelaide
The Triassic to Recent geological history of the North-West Shelf of Australia can be considered in terms of three major transgressive - regressive cycles of deposition. The cycles span the following intervals;
- Entire Triassic period,
- Early Jurassic to Middle Neocomian period,
- Middle Neocomian to Recent period.
Each cycle is initiated by a widespread transgression, and deposition of marine shales. The transgressive phase in each of the first two cycles is terminated by progradation of a fluvio-deltaic complex in a N - NW direction from S and E clastic source terrains. In the case of the final supercycle, the transgressive phase is terminated by the progradation of the present-day carbonate shelf and slope complex.
The main episode of structuring of the North-West Shelf, associated with the breakup of eastern Gondwanaland, commenced in the Early Jurassic and culminated in the Callovian with the abortion of active rifting in the Barrow - Dampier system. The Late Jurassic to Recent period was characterized by thermal subsidence and adjustment (a response to changes in the stress fields between the Australian and Indian plates).
Within this structural and sedimentological framework, there is the potential for the development of economic accumulations of hydrocarbons within structural, stratigraphic and combination structural - stratigraphic traps. These potential plays include;
- Downflank Early Jurassic bar sands,
- Downflank Jurassic alluvial fans,
- Late Jurassic to Middle Neocomian submarine fans.