3D fault growth and linkage during multiphase rifting in the northern Perth Basin

The northern Perth Basin is one in a series of north–south-trending graben and half-graben, formed through multiple phases of rifting with variable extension directions from the Paleozoic to Mesozoic, resulting in complex fault patterns as new faults formed, older faults reactivated and individual fault segments linked both along-strike and along dip. Despite decades of exploration and the importance of faults for controlling the size of energy resources, the timing of fault initiation and propagation histories of key faults have not been investigated. This study utilises new 3D seismic reflection data to analyse the propagation histories of two north–south-striking normal faults and characterise how they accumulated displacement to test models of fault growth. Results reveal that these faults initiated as short segments at different times during the Permian, Triassic and Jurassic. Subsequent linkage, both along-strike and vertically along dip, occurred via several styles through successive extensional events, forming long faults by the Middle Jurassic to Early Cretaceous. Dip-linkage style was controlled by the offset between fault segments above and below a zone of distributed (ductile) deformation within the Lower Triassic Kockatea Shale. The study highlights variability in fault histories, with some faults showing no evidence of early Permian activity, contrasting with findings elsewhere in the basin. Furthermore, there is no evidence for a throughgoing structure in the 3D seismic data near the purported Abrolhos Transfer Fault. Instead, fault geometries are better explained by linkage between en échelon segments rather than basin-scale strike-slip displacement. These findings challenge the prevailing view that all north–south-trending faults in the northern Perth Basin initiated in the late Carboniferous to early Permian and support both propagating and constant-length modes of fault growth, emphasising the complexity of fault development within the northern Perth Basin.