The development of a Triassic fold-thrust belt in a synclinal depositional system, Bowen Basin (eastern Australia)

A synclinal depositional system in eastern Australia (Taroom Trough, Bowen Basin) was affected by folds and thrusts, but the structural style associated with this deformation is not fully understood. Using gridded aeromagnetic data and 2D seismic reflection data, we conducted a structural analysis that unravels the geometry and kinematics of major thrust faults in the eastern-central part of the Taroom Trough. Major structures are the east-dipping Cockatoo, Miles and Taroom faults, and west-dipping Burunga and Glebe faults. Our results show that west-dipping thrusts have a listric geometry that produced gentle hanging-wall anticlines. A north-striking gentle symmetric syncline and anticline pair is also observed to the west of the Burunga Fault. These observations indicate that the deformation in the central Taroom Trough was controlled by decollements in the basement rocks. The decollements and resultant structures were likely developed in response to mild contraction of the synclinal depositional system during the last phase of the Permian-Triassic Hunter-Bowen Orogeny (HBO). The last phase of the HBO also resulted in the reactivation of pre-existing east-dipping Cockatoo and Miles faults. The bulk longitudinal strain, however, in the eastern-central Bowen Basin was low (~2.8% shortening), with the deformation restricted to a relatively narrow zone. In contrast, deformation in the northern Bowen Basin was distributed in a wider fold-thrust belt that accommodated a higher amount of strain. This change in the pattern of deformation along the eastern part of the Bowen Basin could possibly be explained by along-strike variations in the rates of trench advance.