Late Pennsylvanian and Early Cisuralian palynofloras from the Rajmahal Basin, eastern India, and their chronological significance

ABSTRACT

This work documents for the first time a palynological assemblage in the Rajmahal Basin, tentatively considered probable youngest Late Pennsylvanian assemblage, which was hitherto considered early Permian. The palynocomposition consists of 39 species (5 spores, 25 monosaccate, 5 bisaccate- 3 non striate and 2 striate grains, scarce Navifusa sp., scolecodont, algae and fungal hyphae). Two assemblages are described based on the first appearance of taxa, Assemblage I (608.90–599.00 m) dominated by monosaccates and absence of bisaccates and spores. Assemblage II (592.0–590.80 m) also dominated by monosaccates but with the inception of spores, bisaccates and marine palynomorphs. The Assemblage I is correlated to the oldest Potonieisporites neglectus Assemblage Zone of Tiwari and Tripathi based on their similarities and the absence of species recorded in the Assemblage II which is correlated to their overlying Plicatipollenites gondwanensis Assemblage Zone. Palynoassemblages similar to the Assemblage I, radiometrically constrained to the Late Pennsylvanian across Gondwana, along with the lack of diagnostic Permian pollen grains as well as marine Eurydesma fauna and terrestrial glossopterids, tentatively support an older age at least for the lower interval of the Talchir Formation. The latter fossils associated to Assemblage II confirm an early Permian age.

KEYWORDS:

• Palynostratigraphy
• Talchir Formation
• Carboniferous-Permian boundary
• Global correlation
• Brahmani-Birbhum coalfield
• Salbadhra-Gomarpahari region
• Rajmahal Basin

Acknowledgments

The authors express their sincere gratitude to the Director of the Birbal Sahni Institute of Palaeosciences, Dr. Sunil Bajpai for his kind permission to publish this work (RDCC Permission Number: 5/2018-19) and the Geological Survey of India, Kolkata for providing the samples. We are grateful to the anonymous reviewers for their constructive suggestions which has improved the quality of this research article.

Disclosure statement

No potential conflict of interest was reported by the authors.