Oligocene flora from Makum Coalfield, Assam, India

Abstract

The coal-bearing Oligocene sediments exposed in the Makum Coalfield, Assam contain rich assemblage of mega-plant remains. Out of a large number of leaves and fruits collected from the associated sediments at Baragolai, Ledo-Tirap and Tipongpani collieries of the Makum Coalfield, 24 species of dicotyledonous taxa have been identified. Of these, 22 are represented by leaves belonging to the genera Saccopetalum (Anonaceae); Calophyllum, Garcinia, Kayea (Clusiaceae); Pterygota (Sterculiaceae); Santiria (Burseraceae); Heynea (Meliaceac); Nephelium (Sapindaceae); Lannea, Mangifera, Parishia (Anacardiaceae); Rhizophora (Rhizophoraceae); Terminalia (Combretaceae); Memecylon (Memecylaceae); Avicennia (Avicenniaceae); Alstonia (Apocynaceae); Myristica (Myristicaceae), Apollonias (Lauraceae) and Bridelia (Euphorbiaceae). The remaining two taxa are based on fruit/seed comparable to those of Dalbergia and Entada of Fabaceae. The distribution pallem of comparable modern taxa of fossils and keeping in view the great amount and variety of plants preserved in the sediments, it is inferred that thick tropical evergreen to moist deciduous forest existed in this part of northeast India during Oligocene. Occurrence of Avicennia, Rhizophora and Terminalia catappa suggests deltaic, mangrove or lagoonal deposition of coalseams and associated sediments in the Makum Coalfield.