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ABSTRACT: Geological Development and Potential Petroleum Plays of the Townsville Trough Off Northeast Australia

SYMONDS, P. A., and C. J. PIGRAM, Bureau of Mineral Resources, Canberra, Australian Capital Territory, Australia

The Townsville Trough rift basin system covers more than 55,000 sq km, is up to 100 km wide, and in places contains more than 4500 m of sediment. It appears to have formed by slightly oblique northwest-southeast extension. Tilt blocks are bounded by high and lowangle normal faults and cross-cutting lineaments (transfer faults), which segment the rift into discrete basinal elements. There is no direct information on the proposed Mesozoic rift-phase section within the trough; however, during ODP Leg 133 the Neogene section was drilled at several places on its flanks. A significant increase in salinity of the pore waters from the lower portions of these cores may indicate the presence of evaporites at depth. This is consistent with the continental, marginal-marine and restricted shallow arine environments that are expected to have occurred within the trough during the Cretaceous, Paleocene and Eocene. These sequences could also include potential source and reservoir facies.

Several play types have been recognized on seismic data in the Townsville Trough and many of these are typical of those found in unbreached rift systems around the world drapes over fault blocks and basin margins, fault traps, unconformity traps and possible ?Miocene reefal buildups. The Townsville Trough is considered to have good petroleum potential, but the absence of direct information on the nature of any source, reservoir and seal facies also makes it a very high risk frontier basin province.

 

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