Fault-scarp degradation in the central Exmouth Plateau, North West Shelf, Australia

Abstract

Abstract Latest Triassic–earliest Late Jurassic domino-style extensional faulting in the central Exmouth Plateau, North West Shelf of Australia, exhibits footwall degradation scarps with up to 1.8 km of scarp retreat of the Upper Triassic Mungaroo Formation. Extensional fault-propagation folding, rotation and uplift produced gravitationally driven scarp collapse of the incompetent and mudstone-dominated uppermost Mungaroo Formation. Scarp degradation occurred along the entire extent of the footwalls of three major faults within the research area. Individual segments display listric fault surfaces in cross-section and scoop-shaped scars in three dimensions. The listric collapse faults dip towards the erosional scarp and sole out at different levels within the upper Triassic Mungaroo Formation. Footwall crestal collapse formed coalesced, scoop-shaped degradation scarps with Mungaroo Formation debris deposited as wedges within the adjacent hanging-wall synclines. Maximum scarp degradation occurred at the fault centres and decreased towards the fault tips. This study proposes new three-dimensional evolutionary structural models for the fault-scarp degradation in the central Exmouth Plateau.