Structural Evolution of the Permian-Triassic Cooper Basin, Australia: Relation to Hydrocarbon Trap Styles

Abstract

The structural and depositional history of the Cooper basin in eastern central Australia has revealed that the basin is a mildly compressional structural depression controlled by northwest-trending and northeast-trending pre-Permian basement features. Pronounced pre-Permian compressions are indicated by northeast-trending major structures, the Gidgealpa-Merrimelia-Innamincka and Murteree-Nappacoongee trends. Detailed chronostratigraphic facies analysis, with closely spaced palynological control, of the Patchawarra Formation revealed that two pronounced phases of uplift occurred during the Sakmarian. The major intrabasin highs were rejuvenated during these tectonic events, as documented by crestal unconformities (middle and upper Patchawarra unconformities). Evidence of each event is dominantly tectonic in character, with similar depositional patterns over these highs related to each event. These events are also recognizable in midflank areas and basin margins with contemporaneous deposition in deeper parts of the basin. Results from this research show potential for future hydrocarbon discoveries within structural, stratigraphic, and structural/stratigraphic traps in the Cooper basin. Various trap styles are closely associated with faults, unconformities, and lateral facies changes. Lowside fault closures, onlap plays, and unconformity traps are expected to be well ©Copyright 1997. The American Association of Petroleum Geologists. All rights reserved.1Manuscript received February 22, 1995; revised manuscript received August 6, 1996; final acceptance November 12, 1996. 2Geological Survey of Western Australia, 100 Plain Street, East Perth, WA, Australia 6004 (E-mail: n.apak@dme.wa.gov.au). 3National Centre for Petroleum Geology and Geophysics (NCPGG), University of Adelaide, Thebarton Campus, University of Adelaide, SA 5005, Australia. 4Santos Ltd., 101 Grenfell Street, Adelaide, SA 7000, Australia. The authors wish to thank the Cooper Basin Consortium Group of Companies for permission to publish this paper. The drafting staffs at Santos Ltd. and Geological Survey of Western Australia (GSWA) are sincerely thanked for their efforts in preparing figures.This paper is dedicated to the memory of Bill Stuart.