Kink bands in the Chamba region, Western Himalaya, India

Abstract

The Chamba region of the western Himalaya is affected by three phases of deformation (DF 1, DF 2, and DF 3). The DF 1 phase was the most intense and regionally extensive as expressed by the development of the Chamba-Bhramaur syncline. The kink bands developed on the limbs of the syncline during the third (DF 3) phase of deformation on S 1 fabric. The kink bands are of contractional type and well developed in the slate-phyllite sequence of the Salooni and Pukhri Formations. The palaeostress analysis from conjugate kink bands indicates that the maximum compressive stress ( σ 1) was oriented N50°E–S50°W in present coordinates, which nearly coincides with the maximum compressive direction inferred from DF 1 (First phase) and DF 2 (second phase) deformation. The geometry, angular relationship between the kink band boundary and the external cleavage ( α) and the internal angle of the kink band ( β) and strain in kink bands reveal that rotation and dilation was the dominant mechanism. The morphology, kinematics and dynamics of the kink bands suggest that they formed towards the end of the last phase of deformation during emplacement of the Chamba nappe without metamorphism.