Geoscience Australia seismic survey 310: revealing stratigraphy and structure of the outer northern Perth Basin margin

Abstract

Geoscience Australia acquired seismic survey GA 310 in 2008–09, across the southwest margin of Australia, as part of the Australian government’s Energy Security Program. Deep reflection seismic and potential field data were recorded across sparse 2D grids located on the Wallaby Plateau in the north, Mentelle Basin in the south, and the intervening Houtman and Zeewyck sub-basins of the northern Perth Basin. The offshore northern Perth Basin extends for about 700 km along the Western Australia margin, from the towns of Carnarvon in the north to Cervantes in the south. The largely Paleozoic-Mesozoic tectonostratigraphic framework is dominated by Permian and Early-Middle Jurassic rifting, followed by Late Jurassic-Early Cretaceous rifting leading to Valanginian breakup between Australia and Greater India. Underlying Precambrian Pinjarra Orogen structuring, in conjunction with rifting, has resulted in the development of several complex depocentres and basement highs. A recent re-evaluation of the offshore northern Perth Basin well-based lithostratigraphy into a new chronostratigraphic sequence framework has been carried outboard, on the GA 310 seismic lines, into the margin bounding the Zeewyck and northern Houtman sub-basins. The main sequences hosting source rocks—Kockatea and Cattamarra—are widely present in the expansive northern Houtman Sub-basin, and are likely to be present in the deep Zeewyck Sub-basin. The mapping of a thick Late Jurassic Yarragadee Sequence in the Zeewyck Sub-basin indicates a major pre-breakup locus of relatively rapid deposition. The structural interpretation across the sub-basin highlights breakup-drift unconformities and strike-slip faulting and suggests a probable along-margin sheared crustal sliver; tectonic elements commensurate with an evolving rift-shear breakup margin.