Geomorphology, Pedology and Sedimentology of the Upper Gangetic Plains (Himalayan Foreland Basin) - Extensional Tectonic Implications

B. Parkash, Satvindar Singh, A. K. Awsathi, Balaji Bhosle, Pitambar Pati, and Vivekanand Acharya
Department of Earth Sciences, Indian Institute of Technology Roorkee, Roorkee

Regional mapping of soils and faults using remote sensing and GIS techniques, followed by field checks and micromorphological studies and luminescence dating of soils between the Yamuna and Ghaghara rivers in Upper Gangetic Plains show that the rivers are incised in nature and major areas are uplands overlain by moderately to well-developed soils. Major faults are longitudinal in natures, along which the major rivers like the Yamuna, Ganga, Ramganga, Deoha and Ghaghara are flowing. The longitudinal faults trend N-S or NNE-SSW in the northern region, turn N-S in the central region and take easterly to SEE direction in the south, giving the Interfluves between rivers a curvilinear shape. Strike of a number of transverse extensional normal faults changes from approximately E-W in the northern region to NEE-SWW in the southernmost region of the Interfluves. Downthrown sides of these normal faults are to the south and to the east in northern region and western region, respectively. Due to the activity of different segments of various transverse normal faults, terminal fans were deposited on the downthrown blocks. Deposition of terminal fans seems to be a major sedimentation process, as these cover major parts of the uplands. Also, role of extensional tectonics in an overall compressional regime is significant. Also, tilting of smaller blocks leading to the shifting away of large rivers seems to be additional control on distribution of soils and sedimentation on the Interfluves.

After the Last Glacial Maxima at ~10ka, a wet and warm climate prevailed leading to increase in discharges of large rivers, which started incising their courses giving rise to uplands in the Upper Gangetic Plains.

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