Abstract. Various Eocene hyperthermal events have been recorded from lignite sections
of western India in the past decade. To infer the paleoenvironment, during a
warm paleotropical climate of India, we have assessed multiple microfossil
groups like pollen/spores, dinoflagellates and foraminifera from Early Eocene
lignite mine sections from the Cambay (Surkha) and Barmer (Giral) basins and
Middle Eocene sections from the Kutch Basin (Matanomadh and Panandhro mines) of
western India. The Surkha and Giral sections exhibit a dominance of
rainforest elements (Arengapollenites achinatus, Longapertites retipilatus), thermophilic mangrove palm Nypa and (sub)tropical
dinoflagellate cyst Apectodinium, Cordosphaeridium and
Kenleyia. This palynomorph assemblage is indicative of a marginal
marine setting within a hot and humid climate. During the Middle Eocene, the
diversity of dinocyst assemblage increased and a decrease in percentage of
mangrove elements was observed in the Matanomadh and Panandhro mine sections of
the Kutch Basin as compared to the Early Eocene sections of western India.
Bloom of triserial planktic (Jenkinsina columbiana) and rectilinear
benthic (Brizalina sp., Trifarina advena rajasthanensis) foraminifera indicates eutrophic conditions of deposition during the Late
Lutetian–Early Bartonian in the lignite sections of the Kutch Basin which later changed
to oligotrophic, open marine conditions towards the Bartonian (planktic E12
zone). This change to oligotrophic conditions coincides with a drastic
increase in diversity of planktic foraminifera in the top portion of lignite
mines of the Kutch Basin which may be correlated with the Kirthar–Wilson Bluff
transgression event in the Bartonian observed across basins in India, Pakistan and
Australia potentially linked to sea level rise around the Middle
Eocene Climatic Optimum.
Palynostratigraphy and depositional environment of Vastan Lignite Mine (Early Eocene), Gujarat, western India
