Resolving multiple rift phases by strain-rate inversion in the Petrel Sub-basin, northwest Australia

Abstract

The Petrel Sub-basin, located in the larger Bonaparte Basin, preserves >25 km of continuous sedimentary succession from Devonian to Holocene. It is an example of a deeply subsided, highly extended, sedimentary basin, which is characterised by stretching factors of 2-6. These high stretching factors are consistent with crustal thickness estimates obtained by gravity modelling. There is also excellent evidence for large amounts of syn-rift normal faulting particularly along the fringes of the basin. Here we use a strain-rate inversion method to extract information from exploration and synthetic wells to define the number, duration and magnitude of rift events in this basin. Our analyses show that the Petrel Sub-basin has recorded a minimum of three separate extension events that can be independently corroborated with periods of syn-rift faulting observed on seismic data. Our results suggest that the uniform stretching model can account for the large-scale observations in this basin. There is no obvious requirement to appeal to lithospheric simple shear or to significant depth-dependent stretching.