MEGA-TSUNAMI HYPOTHESIS TO EXPLAIN PRESENCE OF REWORKED ARABIAN CARBONIFEROUS PALYNOMORPHS IN THE PANNA FORMATION (PALEOCENE-EARLY EOCENE) OF THE MUMBAI OFFSHORE BASIN, INDIA

Reworked Carboniferous spores and pollen occur in the Panna Formation (Paleocene-Early Eocene) of the Mumbai Offshore Basin (Mehrotra et al., 2001). This is an enigma because Carboniferous sediments are not known from the peninsular India and Himalayan Carboniferous is marine and without any common Carboniferous palynomorph reported from the Panna Formation. Two ideas for this puzzle were suggested. Firstly, presence of Carboniferous sediments under the Deccan Traps, and secondly these reworked palynomorphs probably were derived from the Carboniferous sediments of Africa-Arabia by waves. But there is no proof of Carboniferous sediments under the Deccan Traps and mechanism of wave transport of palynomorphs from Africa-Arabia to Mumbai Offshore Basin was not explained.

This paper proposes a hypothesis to explain this puzzle. About 65 Ma ago, a ~ 40 km diameter Shiva Bolide hit the western shelf of India creating a giant and complex multi ring crater with highs and basins named Shiva Crater (Chatterjee et al. 2006). This catastrophic event generated giant tsunamis that traveled in all directions severely impacting coastlines. Northwestward moving mega-tsunamis impacted the Arabian continental shelf, coastal regions and the Arabian Shield. Mega-tsunamis were reflected and refracted back in northeastern, eastern and southeastern direction. The effect of these waves on land severely eroded and scoured outcropping Carboniferous strata. Arabian Carboniferous stratigraphic units are known to contain rich terrestrial palynomorph assemblages and all reworked Carboniferous palynomorphs from the Panna Formation occur in the Carboniferous sediments of the Arabian Peninsuala. It is hypothesized that mega-tsunamis triggered turbidity currents carried eroded Carboniferous palynomorphs from the Arabian Peninsula to the Mumbai Offshore Basin.