Structural analysis of Rulmi and adjoining areas of Islamabad, Pakistan (T-1448) (MFN 8620)

Abstract

The study area covers the Margalla Hill ranges in the Hazara Basin, which lies in west of Hazara Kashmir Syntaxis. The geological character of rocks are ranging in age between Jurassic to Miocene. The current field investigations have acknowledged that at least three thrust faults runs through area. The cross-sections revealed the subsurface folds geometries and kinematics of thrusts which represents the deformational history of the study area. Main Boundary Thrust (MBT) is structurally linked to Rumli and Ghokina faults in the sub-surface. Rumli and Ghokina faults act as splays or imbrication to Main Boundary Thrust (MBT) with east-north-east trending. All these thrusts are portrayed by east-north-east trending local anticlinal and synclinal folds detached at the level of Precambrian. The Rumli Overturned Anticline, Pir-Sohawa Syncline and Talhaar Anticline are formed as detachment folds cut by thrust faults. These folds are asymmetrical, tight and plunging folds. The restoration of structural cross sections demonstrates that the deformation on the hanging wall of Main Boundary Thrust have average shortening of 4.25 km and its average percentage is 48%. The study area was highly fractured and sheared as near to thrust zone. The macroscopic fracture analysis has been done by inventory circle method on finely grown fracture sets. The fracture implies that the principal stress direction (Õ1) in the study area is NNE-SSW, whereas the minimum stress direction (Õ3) is NNW-SSE