• SUMAN SARKAR

      Articles written in Journal of Earth System Science

    • Palaeoecological significance of a palynofloral assemblage from Surma Group (Late Miocene) of Tamenglong area, Manipur, northeast India

      Raghumani Singh Y Atamajit Singh K S H Suman Sarkar

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      A Late Miocene palynofloral assemblage is recorded for the first time from the sediments of Surma Group exposed at Tamenglong area of Manipur. The assemblage mainly consists of fungal spores and Microthyriaceous ascostromata, algal remains, pteridophytic spores, gymnospermous and angiospermous pollen. The quantitative analysis indicates the dominance of bisaccate gymnosperm pollen (61%) mainly represented by Podocarpidites and Pinuspollenites, followed by pteridophytic spores (23%), algal and fungal remains (11%) and angiosperm pollen grains (5%). Abundance of Hammenisporis spp., fungal conidia and ascostromata along with Zygnemataceous zygospores in the assemblage indicates a warm, humid climate and freshwater depositional environment for the Surma sediments in the present area of investigation. Recorded palynofloral assemblage with the characteristic fungal Microthyriaceous ascostromata suggests a pro-delta to shoreface depositional environment. Representatives of families Parkeriaceae, Cyatheaceae, Gleicheniaceae, Hymenophyllaceae, Podocarpaceae, Araceae and Malvaceae indicate the prevalence of tropical–subtropical climate. The Tamenglong palynofloral assemblage has been compared with some other assemblages known from the Mio-Pliocene sediments of India. The occurrences of abundant Pinuspollenites, Tsugaepollenites, Hibisceaepollenites and Parmathyrites in the present assemblage suggest a Late Miocene age.

    • Ecostratigraphic implications of a Late Palaeocene shallow-marine benthic community from the Jaintia Hills, Meghalaya, NE India

      SUMAN SARKAR

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      Moderately preserved shallow-marine extinct, fossil benthic community has been recovered from a sub-surface Late Palaeocene limestone cave section near Lumshnong in the Jaintia Hills, Meghalaya, NE India. The present contribution focuses on the ecostratigraphic implications of the carbonate microbiofaciesbased on the evaluated facies gradients. Precise field assessments and microscopic observations led to the identification of three microbiofacies: benthic foraminiferal–algal grainstone, coralline algal framestone and oolitic grainstone–packstone. The microbiofacies distinguished in the study suggest a general shallowing-upward trend from an inner shelf setting to a lagoonal–shoal environment depicting the distinct changes in the benthic community. Presence of coralline alga Distichoplax biserialis and benthic foraminifera Idalina sinjarica, Daviesina khatiyahi, Miscellanea primitiva, Rotalia trochidiformis and Vania anatolica assign the studied carbonates to Early Thanetian (SBZ 3) corresponding to the lower part of the Lakadong Limestone. In this study, ecostratigraphy has facilitated the classification of a single carbonate section corresponding to a solitary shallow benthic zone into multiple microbiofacies attributedto variable environmental depositional conditions. This clearly demonstrates its potential in improving the applicability of biostratigraphy worldwide.

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