Late Lower Jurassic palynomorph assemblage in the Dubrajpur sediments, Birbhum District, West Bengal, India

Abstract

This is the first palynological study of the Dubrajpur sediments exposed near the village Murgadangal within the Birbhum Coalfield of West Bengal. The grey shales and off-white sandy claystones have yielded characteristic palynomorph assemblages. At the base of the succession, which consist of coaly shales. The genus Densipollenites is prominent along with striate bisaccate pollen (Palynozone I). In the same assemblage, the first occurrence of Kremipollenites indicus, Arcuatipollenites pellucidus and Goubinispora indica, is significant. This suggests the end Permian level for the Barakar coal deposits. Subsequently, genus Callialasporites makes its first occurrence at the transition of Barakar and Dubrajpur formations and attains fair presentation in the up-section (Palynozone II) replacing Densipollenites. Definite occurrence of Callialasporites turbatus/dampieri in the presently investigated Dubrajpur strata along with Foraminisporis tribulosus, Klukisporites sp. suggest late Lower Jurassic age for Dubrajpur Formation, and the non-diversified palynomorph composition evidences shallow deposition for this outcrop section.