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Himalayan Geology
(Journal)

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Abstract:

Tectono-climatic signatures in NW Himalaya during Quaternary period in Spiti valley

BINITA PHARTIYAL, ANUPAM SHARMA, PRADEEP SRIVASTAVA* Birbal Sahni Institute of Palaeobotany, 53-University Road,Lucknow - 226007, India *Wadia Institute of Himalayan Geology, 33-GMS Road, Dehra Dun - 248 001, India Email: binitaphartiyal@googlemail.com

The Spiti basin of Trans Himalaya is a tectonically active sector, where the accumulated stress of the N-S Indian Eurasian convergence is being compensated by several Nand NNE oriented normal faults (Kaurik-Chango (K-C) Fault, faults associated with Leo-Pargil Horst etc.) making it a pullapart basin. Seismic activity during Late Pleistocene and Quaternary times have also been observed in the vicinity of these normal faults which have probably offset all the earlierstructural signatures in the region. Geologically, the regionhas continuous Tethyan sedimentary record of Precambrianto Cretaceous, however, the outcrops are occasionally blanketed by the physically weathered products of the parent rocks or Quaternary sediments. The distribution of Quaternary sediments (glacial, fluvial and lacustrine) shows tectonoclimatic interplay in determining the landscape evolution of the region. In the upper reaches of the Spiti Basin, the river flows in braided channel showing aggradational regime whereas in lower reaches it starts meandering and the valley width is reduced substantially.

Thick pile of sediments of fluvial and lacustrine origin, intermittently present landslide zones, huge fanglomerates sitting near the threshold angle of failureat hill slopes in the region provide ample opportunity to document the phase of fluvial aggradation, river blocking and subsequent lake forming events and synchronous tectonic activity. In the Upper Spiti river valley fluvio-lacustrine sections at Kioto (32o26’28.4" N and 77o54’21.6" E) and Seko- Nasung were dated. The chronology (OSL) suggests that these lake phases existed between 12-6 Ka. The present study we provides an account of the climatic signatures as recorded in these lake sections as recorded in the mineral magnetic proxies. of information to trace the Quaternary geological history and palaeoclimatic records.

References

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