Abstract

Fault geometry exerts a dominant structural control on the deformation of hanging wall sequences during extension and contraction. Numeric, kinematic and sandbox modelling demonstrates characteristic anticline-syncline pairs are produced during extension of ramp-flat faults. These features are commonly recognised in smaller fault-scale structures, but remain underappreciated at larger, basin scale settings. The Lewis Trough, situated within the Northern Carnarvon Basin, is a basin scale, largely unfaulted syncline with an associated anticline along its western flank rather than a fault-related graben, typical of the region. In this study, we present kinematic models that demonstrate a SE-dipping ramp-flat fault geometry can produce relative highs and lows in Jurassic strata as well as honouring the asymmetric onlap pattern within the Lewis Trough. This study indicates that the Lewis Trough formed during the Early Jurassic, a period typically associated with high rates of extension and not during the Late Triassic Fitzroy Compression event. This study also highlights the importance of the Locker Shale in partitioning deformation of the Permian and Mesozoic fault systems and as a diffuse zone which variably partitions displacement between stacked Permian and Mesozoic fault systems.

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