Bedrock-sculpturing by Tsunami, South Coast New South Wales, Australia

Bedrock-sculpturing resulting in s-forms is associated with catastrophic flooding in near- and subglacial environments produced by flow velocities approximating 10 m s-1. These velocities can also be produced by extreme tsunami generated by submarine landslides or comet impacts with oceans. Repetitive tsunami events during the late Holocene have overwashed headlands along the New South Wales south coast and produced two suites of bedrock-sculptured terrain. At the smaller scale, s-forms similar to muschelbrüche, v-shaped grooves and sichelwannen have developed on upslopes while broad potholes, flutes and transverse troughs have formed on headland crests. Cavitation features consisting of sinuous grooves, impact marks, drill holes and cavettos appear more ubiquitously. At the larger scale stripped ramps, large potholes, cascade channels and canyon-like features have been generated. Six flow phenomena: Mach-stem waves, jetting, vortex impingement, horseshoe vortices, helical flow, and multiple vortex formation are all involved, either singly or in combination with each other, in the creation of bedrock-sculptured features and terrain. Tsunami-sculptured terrain undoubtedly has a global distribution whose extent requires further investigation.