Palynofloral diversity and palaeoenvironments of early Eocene Akri lignite succession, Kutch Basin, western India

Abstract

This study presents palynological analysis of lignite-bearing succession of Akri lignite mine, Kutch, Gujarat, and discussed the implications of the recovered palynomorphs for age, palaeovegetation and palaeoenvironments. A diverse palynological assemblage consisting of algal and fungal remains, pteridophytic spores, angiosperm pollen and dinoflagellate cysts has been recorded. The lower part of the succession (samples 1–5) is dominated by marine dinoflagellate cysts along with palm pollen belonging to family Arecaceae. The upper part of the succession (samples 6–8, 11) is dominated by terrestrial palynomorphs attributed to megathermal families (Bombacaceae, Ctenolophonaceae, Dipterocarpaceae, Meliaceae) followed by mangrove and back-mangrove elements. An early Ypresian age is inferred for the Akri lignite deposit, whereas a middle Ypresian–early Lutetian age is assigned to the post-lignite succession based on the age-diagnostic dinoflagellate cysts and spore-pollen assemblage. Furthermore, based on the distribution of marine and terrestrial palynomorphs, two palynological assemblages (A and B) have been recognised that are apparently controlled by changing depositional environment. The overall palynological assemblage points to a dense tropical rainforest that thrived in the vicinity of the depositional basin under high precipitation regime of warm and humid climate. The peat accumulation took place in a near-shore coastal swamp which was interrupted by fluctuating marine influences, followed by increased siliciclastic influx in a low-salinity coastal swamp dominated by mangroves. Moreover, the palynological comparison suggests that widespread lignite-bearing successions in the western Indian region are in part coeval and belong to the early Eocene (Ypresian) age.