No abstract

Shallow (<200 m) submarine landslides influence margin evolution and can produce devastating tsunamis, yet little is known about these processes on mixed siliciclasticcarbonate margins. We have discovered seven landslides along the shelf edge and upper slope of the central Great Barrier Reef (GBR), Australia. The largest shelf edge landslide is investigated in detail and represents a collapse of a 7 km long section of the shelf edge at 90 m water depth with coarse debris deposited up to 5.5 km away on the upper slope down to 250 m. The precise timing and triggering mechanisms are uncertain but available chronologic and seismic stratigraphic evidence suggest this event occurred during the last deglacial sea-level rise between 20 and 14 ka. Regional bathymetric data confirms that these shelf edge and upper slope slides are restricted to the central GBR between latitude 18° and 19°S, suggesting a spatial relationship between the extensive Burdekin paleo-fluvial/delta system and shallow landslide activity. This study highlights an important local mechanism for the generation of tsunamis on this margin type, and numerical simulations under present conditions confirm a 2 to 3 m tsunami wave could be produced locally. However, we consider that the risk of such slides, and their resulting tsunamis, to the modern coastline is negligible due to their relatively small size and the capacity of the GBR to dissipate the wave energy.