Geometry of Permian to Mesozoic Sedimentary Basins in Eastern Australia and their Relationship to the New England Orogen

Abstract

Sedimentary basins adjacent to the New England Orogen in eastern Australia contain a record of events from the Early Permian to the Late Jurassic that provide information on the later history of the orogen. The basins have complex geometries, as seen in BMR and company seismic data. The halfgrabens of the Permian Taroom Trough (southem, sub-surface extension of the Bowen Basin) and Triassic Esk Trough formed by oblique extension, with the steep bounding faults having a significant strike-slip component. Localised thrusts, folds and positive flower structures in Jurassic sedimentary rocks resulted from transpression associated with reactivation of the strike-slip faults. Some previous workers postulated that the Bowen Basin, and also the Sydney Basin to the south, were initiated during aperiod of ENE-WSW oriented extension in the latest Carboniferous or earliest Permian. Nevertheless, these basins were separated by a zone in the southem Bowen and Gunnedah basins that was dominated by oblique extension and strikeslip. During subsidence of the basins, strike-slip fault movements also played a significant role in the adjacent basement, controlling the transport and accretion of displaced terranes and oroclinal bending of an accretionary wedge sequence. Hence the New England Orogen, as well as the adjacent basins, was greatly influenced by strike-slip faulting for a considerable part of its history.