Coastal boulders as evidences of high-energy marine events from Diu Island, west coast of India: storm or palaeotsunami?

The coastal segment of Diu Island from west coast of India has been studied for its boulder deposits. The dimensions, morphology and characteristics of these boulders were studied to elucidate the type of wave responsible for their detachment from jointed shore platform and transport them to their present final position. The generated data were compared with wave height decay curves of strongest storm that has hit the Gujarat coastline (May 2001 storm). It was concluded that even the strongest storm ever recorded in Arabian Sea (Gonu 2007) cannot detach and initiate the transport of these boulders to their final position. However, a tsunami wave of 3.5-m wave height can easily detach and mobilize these boulders to their final position. On the basis of imbrication direction, we postulate that the direction of source of tsunami wave is southwesterly. Owing to the strike-slip nature of Owen Fracture Zone and earlier documented large landslides along the Southern Owen Ridge, we postulate the most likely source of this tsunami wave could be a mega submarine landslide along the Southern Owen Ridge.