SUBMARINE MASS-WASTING DEPOSITS AS AN INDICATOR OF THE ONSET OF FORELAND THRUST LOADING - LATE PERMIAN BOWEN BASIN, QUEENSLAND, AUSTRALIA

In the eastern part of the Permo-Triassic Bowen Basin of Queensland, A ustralia, a transition from passive, thermal subsidence to flexural (f oreland basin) subsidence is recorded within the Upper Permian stratig raphy. Two coarse-grained intervals containing deposits of mass-wastin g processes occur within an otherwise siltstone-dominated succession o ver 1500 m thick (the Moah Creek Beds and equivalents). These interval s can be traced over at least 350 km north-south, along the structural eastern margin of the basin. The lower of the coarse-grained interval s is spectacularly exposed in the banks of the Fitzroy River, west of Rockhampton. Here, interbedded sandstones and siltstones of marine she lf origin are abruptly truncated by a mudrock succession containing ev idence of slumping and contemporaneous magmatic activity. This unit pa sses up-section into packages of mass-flow conglomerates and diamictit es, interpreted to have formed on an unstable submarine slope. The cha racter of the mass-flow deposits, their stratigraphic position and lat eral extent are interpreted in terms of destabilization of a sloping m arine surface by pulsed, subsurface thrust propagation.