Palynological Study of the Eocene Kopili Shale, Assam-Arakan Basin, India

Palynological investigation was conducted to reconstruct the palaeodepositional and palaeoclimatic conditions of the late Eocene Kopili Shale of Assam-Arakan Basin (AAB), India. The palynoassemblage (PA) comprises particulate organic matters (POMs), dinoflagellate cysts (DCs), pteridophytic spores (PSs), angiospermous pollen (APs), acritarchs, fungal remains (FRs) and foraminiferal linings (FLs). Amorphous organic matter (AOM), making up 55 to 97 % of the PA, is the predominant form of organic matter (OM) among the POMs. The palynoflora is dominated by DCs comprising 5 genera (Cordosphaeridium, Hystrichosphaeridium, Heteraulacacysta, Glaphyrocysta and Thalassiphora) and 22 referable species. The PSs are assigned to 3 families (Polypodiaceae, Matoniaceae and Osmundaceae) and 8 referable species. The APs are characterised by 3 families (Arecaceae, Fabaceae and Gunneraceae) and 9 pollen species. The palynological data reveal that the Kopili Shale was deposited in a marginal-marine to shallow marine environment under suboxic-anoxic basin condition having influx of coastal elements into the depositional basin. The palaeoclimatic condition during the deposition of the Kopili Shale was tropical-subtropical and warm-humid.