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      https://www.ias.ac.in/article/fulltext/jess/131/0103

    • Keywords

       

      Tide-dominated delta; amalgamated bar; sand–mud couplets; proximal delta front lobe; Laisong Formation.

    • Abstract

       

      In western Manipur, India, a ${\sim}$765 m thick dominantly fine-grained succession of the Late Eocene–Early Oligocene Laisong Formation, constituted of siltstone-silty-shale heterolithic units at its lower part and thickly bedded sandstones in the upper part, allowed documentation of subaqueous part of a tidal delta.The abundant incidence of features including lenticular, wavy bedding, starved ripple trains, syn-sedimentary deformation, reactivation and erosional surfaces, double-mud drapes, tangential bottom setcontact, rip-up mud clasts bear tell-tale evidence in favour of tidal modulations. Furthermore, a prominent thickening- and coarsening-up progradational facies stacking motif is correlated as signature for tide-dominated delta. From process-based facies and facies succession analysis, five different subaqueous environments of delta were delineated which include prodelta, terminal distributary channel, distal delta front, proximal delta front sheet and proximal delta front lobe in order of stratigraphic superposition. The river-fed sediments were extensively reworked by accentuated tidal currents in an embayed coastline, developed along a narrow, elongated ocean basin bordered by the Indian plate on its west and Burmese micro-plate in the east. A local-scale subsidence and sea-level rise is inferred as trigger for the Laisong tidal delta development in the backdrop of its Late Eocene–Early Oligocene time frame that otherwise witnessed large-scale growth of east Antarctic ice sheet and regional scale fall in sea-level.

    • Author Affiliations

       

      PRAMOD KUMAR1 KSHETRIMAYUM LAKSHMIRANI DEVI1 PARTHA PRATIM CHAKRABORTY1 HEMANTA SINGH RAJKUMAR2

      1. Department of Geology, Center for Advanced Studies, University of Delhi, Delhi 110 007, India
      2. Department of Geology, United College, Chandel, Manipur 795 127, India.
    • Dates

       
  • Journal of Earth System Science | News

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