Unraveling Deep Structures Along A Rifted-Transform Margin: Insights From an Integrated Geophysical Study of The Northern Perth Basin

Abstract

The Houtman Sub-basin lies adjacent to the Wallaby-Zenith Transform Margin, an under-explored region of Australia’s continental margin located at the transition between the non-volcanic margin of the northern Perth Basin and volcanic province of the Wallaby Plateau. New seismic data acquired in the northern Houtman Sub-basin enables better understanding of the structural architecture and rifting development along a rifted-transform margin and provides the framework for a detailed integrated margin-scale basin evaluation. Profile modelling of potential field data, combined with 2D seismic, reveals complex along-strike and dip variability in the crustal thinning of the Houtman Sub-basin, with extreme thinning (<5 km thick) beneath the main Permian depocentre. Outboard of this hyperextended zone, along the basin margin, is a zone of volcanic SDRs. Five different structural domains have been mapped across the margin, reflecting abrupt change in crustal thinning and volcanic emplacement. These domains trend roughly NW-SE to NNW-SSW, parallel to major basement terrane boundaries. Magnetic modelling suggests that the nature of the basement underlying the proximal domain and the hyperextended domain in the central Houtman Sub-basin are different and that a major Proterozoic basement terrane boundary lies beneath the necking domain. The margin was structured during polyphase Permian and Late Jurassic rifting events which led to hyperextension prior to continental magmatic break-up and formation of oceanic crust during the Early Cretaceous. Our results suggest that the distribution of Early Permian rifts localised strain during Jurassic—Early Cretaceous rifting and strongly controlled the location and style of rifted margin during Valanginian continental break-up.