Structural analysis and geologic mapping of Khawri Khwar section and adjacent area, part of Kala Chitta Range, Nizampur, Khyber Pakhtunkhwa, Pakistan (T-1432) (MFN 6237)

Abstract

The study area is the part of Kala-Chitta Range lying in the Himalayan foothills of northern Pakistan. This range is bounded to the south by Main boundary thrust while the northern extremity is demarcated by Hissartang thrust. The area is highly complex and intensely deformed. The detailed mapping has established eight litho-stratigraphic units ranging in age from Late Jurassic to Paleocene. These litostratigraphic units falls in three distinct groups that are Baroach, Surghar and Makarwal Group from bottom to top. The undifferentiated Jurassic Baroach Group marks the base of stratigraphic sequence. The Cretaceous sequence is represented by Chichali, Lumshiwal and Kawagarh Formations from bottom to top whereas the Paleocene sequence exposed are Lockhart and Patala Formations. The Early Cretaceous Hangu Formation is missing in the study area. Structural analysis is carried out by the help of field mapping. The outcropping rocks have well recorded imprints of Himalayan deformation, and is represented by common east-west trending series of parallel synclines and anticlines. In addition, several parallel thrust faults with east-west trend are present as well. The structural fabric clearly demonstrate that this part of Kala-Chitta Range has undergone through north-south compressional stresses. The structures clearly suggest two distinct deformational phases. The earlier phase is responsible for the formation of several forethrusts while the second deformational phase is responsible for several folds and back thrusts. Some thrust faults were also folded later in the second phase. The intricate structural geometry of the study area produces different east-west trending close anticlinal structures and close-open synclinal folds with common east-west trend. These folds are mostly asymmetrical. Several thrust faults have been mapped in the study area. Most of the thrusts are northward dipping fore thrusts. The study area is highly fractured. The mesoscopic fracture analysis has been done in different parts of study area where fracture sets were nicely developed. The results of this analysis reveal that most of the fractures are generally NW-SE oriented. The fractures indicate that the principal stress direction (Õ1) is NNW-SSE whereas the minimum stress direction (Õ3) is NEESWW.