Palynological studies of the Barail Group (Oligocene) in the Type Area, Assam

Abstract

The surface samples from Disang (Eocene), Laisong (Lower Oligocene), Jenam (Middle Oligocene), Renji (Upper Oligocene) and Bhuban (Lower  Miocene) formations exposed along Silchar-Halflong road in the type area in Assam were palynologically investigated. Six samples studied from Disang are placed into Striatriletes microverrucosus Cenozone. Laisong palynological assemblage comprises 30 genera and 28 identifiable species and the entire assemblage is placed into Osmundacidites wellmanii Cenozone. The Jenam assemblage has 49 genera and 42 identifiable species and the assemblage is divisible into: (i) Malayaeaspora costata Cenozoe and (ii) Striatriletes susannae Cenozone. The Renji assemblage constitutes Cyathidites minor Cenozone. The Bhuban assemblage is placed into Pinuispollenites crestus Cenozone. The Disang palynological assemblage is distinguished from Laisong by the high representation of Phragmothyrites eocaenicus and Striatriletes susannae. Laisong is differentiated from Jenam by the dominance of Cyathidites minor, Lygodiumsporites lakiensis, Striatriletes susannae and Striatriletes multicostatus. In Renji Formation, Cyathidites minor reappears in a good percentage but frequency of Polypodiaceaesporites tertiartis, Striatriletes susannae, Striatriletes multicostatus and Osmundacidites wellmanii is considerably reduced. The Bhuban assemblage is distinguished from Renji by the abundance of Pinuspollenites crestus and Podocarpidites kbasiensis.