• Depositional environment and provenance of Middle Siwalik sediments in Tista valley, Darjiling District, Eastern Himalaya, India

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    • Keywords

       

      Eastern Himalaya; Middle Siwalik; foreland basin; facies; alluvial fan.

    • Abstract

       

      The frontal part of the active, wedge-shaped Indo-Eurasian collision boundary is defined by the Himalayan fold-and-thrust belt whose foreland basin accumulated sediments that eventually became part of the thrust belt and is presently exposed as the sedimentary rocks of the Siwalik Group. The rocks of the Siwalik Group have been extensively studied in the western and Nepal Himalaya and have been divided into the Lower, Middle and Upper Subgroups. In the Darjiling–Sikkim Himalaya, the Upper Siwalik sequence is not exposed and the Middle Siwalik Subgroup exposed in the Tista river valley of Darjiling Himalaya preserves a ∼325 m thick sequence of sandstone, conglomerate and shale. The Middle Siwalik section has been repeated by a number of north dipping thrusts. The sedimentary facies and facies associations within the lithostratigraphic column of the Middle Siwalik rocks show temporal repetition of sedimentary facies associations suggesting oscillation between proximal-, mid- and distal fan setups within a palaeo-alluvial fan depositional environment similar to the depositional setup of the Siwalik sediments in other parts of the Himalaya. These oscillations are probably due to a combination of foreland-ward movement of Himalayan thrusts, climatic variations and mountain-ward shift of fanapex due to erosion. The Middle Siwalik sediments were derived from Higher- and Lesser Himalayan rocks. Mineral characteristics and modal analysis suggest that sedimentation occurred in humid climatic conditions similar to the moist humid climate of the present day Eastern Himalaya.

    • Author Affiliations

       

      Abhik Kundu1 Abdul Matin2 Malay Mukul3

      1. Department of Geology, Asutosh College, 92, S.P. Mukherjee Road, Kolkata 700 026, India.
      2. Department of Geology, University of Calcutta, 35, Ballygunge Circular Road, Kolkata 700 029, India.
      3. Department of Earth Sciences, Indian Institute of Technology Bombay, Powai, Mumbai 400 076, India.
    • Dates

       
  • Journal of Earth System Science | News

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