Morphotectonic Evolution of Parduni Basin: An Intradun PiggybackBasin in Western Doon Valley, NW Outer Himalaya

摘要

During the course of mapping of active faults in the northwestern Outer Himalaya (using CORONA photographs,multispectral satellite data of Indian Remote Sensing satellite (IRS) and aerial photographs) we have identified anisolated basin of Quaternary and Holocene sediments resting unconformably on Siwaliks, around Parduni, in thenorthwestern Dehra Dun (Doon) valley. The region around Parduni is tectonically very complex and is traversed byactive thrust faults to its north and south and strike slip faults to its east and west. The uplift and southward shift alongthe strike slip faults on both sides and the Markanda thrust edging to its south, the Parduni has developed as anintradun basin and now remains isolated from the main Doon valley. Based on the OSL age data widespread depositionof Quaternary alluvial fan sediments, the dun gravels, is inferred to have initiated around 34 ka BP in the western part ofthe Doon valley, while the sedimentation in the Parduni Basin started only around 27 ka BP, which more or lessceased around 20 ka. The southward movement of the Parduni Basin as a piggyback basin is ongoing with recentalluvial deposits covering the dun gravels tectonically overlain by the Siwalik sandstone and mudstones in the hangingwall of the Markanda thrust. The present communication discusses the development and evolution of the ParduniBasin vis-a-vis the configuration of the Doon valley in the northwestern Outer Himalaya and the prevalence of tectonicsexpressed or demonstrated in the active Himalayan Front.