Evolution and structuring of the Joseph Bonaparte Gulf as delineated by aeromagnetic data

Abstract

A large portion of the southern Joseph Bonaparte Gulf area, northwestern Australia, was originally underlain by extensive contiguous Proterozoic sills and volcanic rocks. Subsequent extension and basin formation in this area during the Palaeozoic fractured this horizontal basic magnetic sheet. Evidence of this fracture patten and the extensional movements are obvious in images of the magnetic field over the basin. A series of transfer fault accommodation zones trending at 035 degrees and an associated series of perpendicular normal faults have been mapped. Onshore geology, gravity and seismic data support the transfer fault model. An underexplored graben, 75 kilometres long and 50 kilometres wide, which formed as a result of the extension process, has been mapped on the western edge of the Joseph Bonaparte Gulf adjacent to the Proterozoic Kimberley Basin.