Strain Analysis of Deformed Pebbly Horizon from the Garhwal Group, Pharsaun, District Chamoli, U. P.

A deformed pebbly horizon has been observed in the quartzitic phyllite member of the Garhwal Group rocks exposed along a ENE-WSW striking fault, south of village Pharsaun, District Chamoli, U. P. The directions and ratios of the principal strain axes of tbe finite strain ellipsoids have been determined. The strain data have been plotted on Flinn triangular and polar graphs, respectively. The strain analysis reveals tbat the mean shape of the pebbles prior to deformation was flattening type and with progressive deformation, the shape of the pebbles changed to constriction type, then to flattening type, and finally to constriction type. The deformation of the pebbles bas been related to the first tectonic movement. Shearing along the fault of later generation was responsible for the rotation and reorientation of the principal axes of tbe deformed pebbles.