Journal - Palaeohydrological reconstruction of Siwalik Group in Surai Khola section of west Nepal Himalaya

Palaeohydrological reconstruction of Siwalik Group in Surai Khola section of west Nepal Himalaya

Prakash Das Ulak

Department of Geology, Tri–Chandra Campus,

Tribhuvan University, Kathmandu, Nepal

Jour. Nep. Geol. Soc., Vol. 31, 2005, 33-42


Abstract

About 5 km thick Neogene Siwalik Group in the Surai Khola section of west Nepal comprises many fining-upward cycles, which are from several metres to tens of metres thick. However, the Siwalik sequence as a whole reveals a coarsening upward trend. The palaeohydrological reconstruction of the Siwalik Group was based mainly on two parameters: the sediment grain size and the thickness of individual fining-upward successions. The estimated palaeoflow velocity in the Siwalik Group varies from 0.32 to 4.76 m/s, palaeochannel gradient ranges from 5.29x10-5 to 9.59x10-4 m/m, and palaeodischarge fluctuates from 1 to 104 m3/s, in the stratigraphically upward direction. These palaeohydrological parameters indicate a gradual change in fluvial system, presumably owing to the southward propagation of thrusts.

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