• A M Bhola

      Articles written in Journal of Earth System Science

    • Folds in multilayered rocks of Proterozoic age, Rajasthan, India

      A M Bhola B K Sharma S K Ghosh

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      First phase folds F1 developed in polydeformed Ajabgarh Group rocks of Proterozoic age are studied using various geometrical methods of analysis for compatibility of homogeneous strain in both class 1–3 pairs by correlatingt′ga/α plots with existing curves for competent layers and matchingtga/α plots with the flattening curves for the incompetent layers.

      F1 folds were initiated by the process of buckling but underwent [(λ21) = 0.2 to 0.7] for competent layers andR- values of 1.1 to 5 for incompetent layers. The varying flattening is also revealed by the geometry of folds. The apparent buckle shortening of folds which ranges between 49 and 67 per cent with a majority of the folds having shortening values between 50% and 55% (exclusive of layer parallel strain) and inverse thickness method strain up to 50%. Besides flattening, the fold geometry was also modified by the pressure solution. This is borne by the presence of dark seams rich in phyllosilicates and disseminated carbonaceous material offsetting limbs of buckled quartz veins in slates

    • Kink bands in thrust regime: Examples from Srinagar—Garhwal area, Uttarakhand, India

      Shashank Shekhar A M Bhola P S Saklani

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      This paper deciphers the late stress systems involved in the development of kink bands in the perspective of thrust regime. In kink bands, the correlation coefficient for 𝛼-𝛽 plots is positive near thrusts and negative away from thrusts. The plots show nearly linear relationship near thrusts and non-linear relationship away from thrusts. The rotation was prominent mechanism of kink band formation near thrusts and rotation coupled with shearing, along the kink planes away from thrusts. Along thrusts 𝜎1 is horizontal E–W trend and it rotates to horizontal N–S trend away from the thrust. The proposed model establishes that (1) the shearing along kink planes led to angular relationship, 𝛽 > 𝛼 and (2) the kink planes of conjugate kinks could be used for paleostress analysis even in those cases where shearing along these planes has occurred.

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