Evidence of Late Quaternary seismicity from Yunam

Authors: Archna Bohra B S Kotlia Amzad H Laskar M G Yadava

Publish Date: 2014/04/30

Volume: 123, Issue: 3, Pages: 603-616

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Abstract

A relict fluviolacustrine sediment of an 8 m thick section exposed at Kilang Sarai along Yunam river near Baralacha La shows presence of cycloids or pseudonodules ball and pillow structures flamelike and pocket structures sand dyke injections bed dislocation/faulting and flow folds Within this section four deformed levels of soft sediment structures have been identified which were dated ca 25 ka BP at level 1 ∼04 m from the modern river level mrl 201 ka BP at level 2 ∼18 m mrl 177 ka BP at level 3 ∼256 m mrl and 122 ka BP at level 4 ∼425 m mrl Detailed study of these soft sediment structures allow us to demonstrate that deformation level 3 is not related to seismic trigger but remaining three deformation levels 1 2 and 4 are ascribed to seismic origin From compilation of earlier palaeoseismological studies using soft sediment deformational structures SSDS in the palaeolake deposits in the adjoining area suggest that the deformational events identified in the present study are regional in nature and thus tectonic process plays an important role in the evolution of landform in the Spiti regionThe authors thank the two anonymous reviewers and the Editor Dr R K Mangalampally for their critical comments and constructive suggestions which greatly benefitted this paper Dr Archna Bohra gratefully acknowledges Dr R Ramesh PRL Ahmedabad for his kind support during radiocarbon laboratory analysis

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