Reworked carboniferous palynomorphs in the panna formation (paleocene-early eocene)‎ of the Mumbai offshore basin, India : possible role of mega-Tsunami transport from the Arabian peninsula

الملخص EN

Mehrotra et al.

[1] reported the presence of reworked Carboniferous terrestrial palynomorphs (spores and pollen) in the Panna Formation (Paleocene-Early Eocene) of the Mumbai Offshore Basin.

This was a puzzling discovery because Carboniferous sediments are not known to occur in peninsular India.

Although Carboniferous sediments are present in the Himalayas, they are predominantly of marine origin.

The Himalayan sediments have yielded extremely poor palynomorphs and have little in common with the reworked assemblage of Carboniferous palynomorphs from the Panna Formation.

Mehrotra et al.

[1] offered two possibilities for this occurrence.

Firstly, they speculated on the existence of Carboniferous sediments under the widespread flood basalts of central India known as the Deccan Traps, and hypothesized their erosion and re-deposition in the Panna Formation.

Secondly, they speculated that the reworked palynomorphs might have been derived from Carboniferous sediments of the Africa–Arabia regions by waves.

However, to date there is no proof of the presence of Carboniferous sediments under the Deccan Traps.

Furthermore, the authors did not propose any explanation regarding the kind of wave action that might have been responsible for transporting Carboniferous palynomorphs from the vast regions of Africa- Arabia to the Mumbai Offshore Basin.

This paper offers a hypothesis that may explain the presence of reworked Carboniferous palynomorphs in the Panna Formation of the Mumbai Offshore Basin, India.

About 65 Ma ago, at a time roughly coincident with the Cretaceous–Tertiary (K-T) boundary, a bolide approximately 40 km in diameter struck the western shelf of India a few hundred kilometers off the coast of present day Mumbai, India.

The impact created a giant and complex muttering crater with several roughly concentric highs and lows, known today as the Shiva Crater (Chatterjee et al.

[2].

This catastrophic event likely generated mega-tsunamis that traveled in all directions and severely impacted the coastlines of western India and eastern Africa, as well as the southern and eastern coasts of the Arabian Peninsula.

The northwestward moving mega-tsunami waves impacted the Arabian continental shelf and coastal regions.

These giant waves traveled across the lowlands of the Arabian Peninsula until they encountered the eastern and southern margins of the Arabian Shield.

The mega-tsunami waves then reflected and refracted back in the northeastern, eastern, and southeastern directions after impacting the Arabian Shield.

These waves severely scoured and eroded the exposed Carboniferous strata of the Arabian Peninsula.

All these Carboniferous stratigraphic units are known to contain rich terrestrial palynomorphs assemblages.

In addition, all reworked Carboniferous palynomorphs found in the Panna Formation occur also in the Carboniferous sediments of the Arabian Peninsula.

It is suggested that the mega-tsunami triggered turbidity currents, which carried with them eroded Carboniferous fine sediments and associated palynomorphs from the Arabian Peninsula and deposited them in the sediments that formed the Panna Formation upon reaching the Mumbai Offshore Basin.

It is also possible that turbidity currents may have continued to transport these Arabian palynomorphs into the Shiva marine low for centuries following the bolide event, explaining the occurrence of Carboniferous palynomorphs at multiple levels in the Panna Formation.