ABSTRACT: Mesozoic Evolution and Exploration Potential of the Western Exmouth Plateau, Australia

BUFFLER, RICHARD T., University of Texas Institute for Geophysics, Austin, TX, and NEVILLE F. EXON, Bureau of Mineral Resources, Canberra, Australian Capital Territory, Australia

A regional grid of seismic data across the western Exmouth Plateau combined with recent ODP drilling results (Sites 762, 763, and 766) provide new ideas about the sedimentary history, tectonic evolution and exploration potential of the area. The outer plateau is underlain by a thick section of regionally tilted, block-faulted, largely fluvial-deltaic, late Paleozoic-Triassic sediments. These sediments grade westward into an acoustically transparent basement interpreted to be Late Triassic-Early Jurassic intermediate volcanics. The western plateau is flanked on the northwest and southwest by the Gascoyne and Cuvier ocean basins, respectively, formed during the Lower Cretaceous when "Greater India" separated from Australia. Thermal doming of the margins in earliest Cretaceous just prior to initial rifting provided a southerly source area for the Barrow delta, as well as local source areas for a thick, Barrow-equivalent sandstone unit along the western margin. Continued local uplift of the western margin during initial rifting (late Valanginian-Hauterivian) provided shallow-water source areas for local clastic wedges that prograded both eastward onto the plateau as well as westward into newly formed deepwater rift basins. This was followed by rapid subsidence of the plateau and deposition of deep-water shales and carbonates during the remainder of the Cretaceous and Cenozoic. Inferred source rocks (gas?) in the Triassic section, abundant reservoir rocks in the Triassic and overlying Lower Cretaceous, an overlying Cretaceous and Cenozoic seal, plus several episodes of the mal activity make the regional high along the western margin of the Exmouth Plateau a possible target for future deep-water exploration.

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