Disang and Barail Sediments, their Contact and Palaeodepositional Environment along Tuli-Merangkong-Mokokchung Area of Mokokchung District, Nagaland, North East India with Reference to Diverse Palynofossil Assemblages

Abstract

The contact between the Barail and Disang Group in the belt of Schuppen has been remaining as a controversy amongst the scientists, because the lithologic association of the Nagoan Formation belonging to the Barail Group almost resembles the lithology of the Disang Group. The present study has attempted to establish a contact between the Barail and the Disang in the studied area based on age diagnostic palynomorphs identified and it is observed that the present contact lies about 4.2 km southwest of the established contact by the Directorate of Geology and Mining, Government of Nagaland in 2015. This investigation has documented a diverse palynofossil assemblages comprising of 58 species under 31 genera from the Disang and the Barail groups belonging to Cretaceous — Eocene — Oligocene age that is extending from Tuli -Merangkong- Mokokchung area of Mokokchung district of Nagaland, northeast India. The assemblage is comprised of angiosperm pollen (43%), fungal remains (35%), pteridophytic spores (19%) and gymnosperm pollen (one genus and one species only). The average representation of other palynotaxa are dinoflagellate cysts (1%), marine elements mainly acritarch and foraminiferal test linings (2%). Based on the presence of different palynomorphs two distinct palynozones (I and II) have been suggested. Sediments of Tuli- Merangkong -Mokokchung area are deposited in deltaic to shallow marine environment.