THE ROLE OF NORMAL FAULT GROWTH ON SEDIMENTATION DURING BASIN FORMATION: A CASE STUDY FROM A LATE CAMBRIAN RIFT ASSOCIATED WITH THE LONG-LIVED PALAEO-PACIFIC SUBDUCTION SYSTEM IN EASTERN AUSTRALIA

Normal fault growth provide a fundamental control on the stratigraphic architecture, internal drainage patterns and basin facies distributions of evolving extensional basins. Despite recent advances in the understanding of present-day normal fault growth, quantifying the effect of normal fault evolution on the architecture of ancient sedimentary basins has been largely obscured by post-rift deformation and erosion.

The Late Cambrian Owen Conglomerate of western Tasmania was deposited during a period of crustal extension associated with the outboard palaeo-Pacific subduction system of eastern Australia. The extensional basin comprises a thick sandstone and conglomerate succession of fluvial and marine turbidite origin, which provides an excellent insight into the rift-fill history and basin formation, due to the glaciated topography and exceptional outcrops of western Tasmania, and also the typically overfilled nature of the basin, which acts to preserve the fault displacement history of the border fault system active during deposition.

Integration of lithofacies distributions, isopach maps and palaeocurrent data with a detailed structural dataset defines a stratigraphic architecture that is strongly coupled with the development of the border fault system, and offers a high resolution model for ancient fault development. While the generation of accommodation space adjacent to footwall scarps facilitated the development of a hanging-wall, dip-slope fluvial catchment and axial-through drainage networks, tectonic subsidence provided the crucial trigger for the onset of isolated marine sedimentation, where accommodation space generated by the localised accumulation of displacement on individual segments outpaced sediment supply.