Stratigraphic Architecture of the Lopingian Succession in the Bowen Basin of Eastern Australia

To investigate the stratigraphic architecture of the Lopingian succession in the Bowen Basin of eastern Australia, the major stratigraphic units have been reviewed using wireline logs from 700 drillholes. The Lopingian succession comprises the Peawaddy Formation, Black Alley Shale, and Bandanna Formation (in ascending order) and their equivalents. All three formations were deposited in a retroarc foreland basin setting that formed during the Hunter-Bowen contraction directed from the east–northeast. Spatial variations in thickness and sediment dispersal patterns were analyzed. The Peawaddy Formation comprises a series of digitate, fluvially-dominated deltas that were sourced from the north and east of the basin, and extended southwards in the northern part of the basin, and westwards in the central and southern part of the basin, into a shallow sea. In the Black Alley Shale, similar patterns are evident. The Bandanna Formation is entirely fluvial and fluvio-estuarine across the basin because by this time the marine basin had been filled. The thickness of the Peawaddy Formation, Black Alley Shale, and Bandanna Formation vary across the basin with a gradual eastward thickening trend that continues to the present eastern margin of the basin. This suggests that the original depocenter is only partially preserved in the Taroom Trough, while the original foredeep extended further to the east. Tectonic shortening of the Taroom Trough depocenter and of the northeastern margin of the basin during the Hunter-Bowen contractional event have significantly modified the original plan shape of the basin.