|
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
Banerjee, P., Bürgmann, R., Nagarajan, B., Apel, E., 2008. Intraplate
deformation of the Indian subcontinent. Geophysical Research Letters
(in press). Bilham, R., England, P. 2001. Plateau “pop-up” in the great 1897
Assam earthquake. Nature, 410(6830), 806-809. Biswas, S., Coutand, I.,
Grujic, D., Hager, C., Stöckli, D., Grasemann, B. 2007. Exhumation and
uplift of the Shillong plateau and its influence on the eastern Himalayas:
new constraints from apatite and zircon (U-Th-[Sm])/He and apatite fission
track analyses. Tectonics, 26, doi: 10.1029/2007TC002125. Bookhagen, B.,
Burbank, D.W. 2006. Topography, relief, and TRMMderived rainfall variations
along the Himalaya. Geophysical Research Letters, 33, L08405,
doi:10.1029/2006GL026037. Grujic, D. et al. 2006. Climatic forcing of
erosion, landscape and tectonics in the Bhutan Himalayas. Geology, 34,
801–804; doi: 10.1130/G22648.1. |
