Respected Sir, I want to know about the tectonic/structural setup of Salt Range, Pakistan. A brief note about major and minor structural styles of Salt Range. Thanks
Thank you very much for sending me this question.
My answer is as follows;
The Salt Range (SR) is a major structural element in the northern Punjab and Khyber Pakhtunkhawa provinces of Pakistan. SR is an active frontal thrust zone of the lesser Himalaya in Pakistan, the origin of thrusting is related to the Himalayan orogeny. The structural elements of NW Himalayan Pakistan include a chain of mountain belts which are known as syntaxis or re-entrants. Trans-Indus Salt Range, to the west of River Indus, southern Salt Range forming the southern boundary of the Potwar Plataeu separating Punjab plains to the physiographically uplift of the Potwar area. In the east SR thrust merges into the fault system of Jhelum –Kashmir Reentrant. The two eastern and western bounding rivers are Jhelum and Indus respectively. Two NW trending major strike slip faults, Kala Bagh Fault and fault system along Surgahr Range have physically cut and rotate the western part of the SR forming the Trans Indus Ranges to the west of the SR. The structural trend of the SR southwest-northeast in the southern Salt Range and northwest to Southeast to the western SR.
Tectonically speaking, SR is the active frontal thrust zone of the Himalya in Pakistan. Subsurface structural geometry as revealed by seismic data identified that a 1 km offset of the basement acted as a buttress that caused the central SR-Potwar Plateau thrust sheet to ramp to the surface, exposing Mesozoic and Paleozoic strata. These rocks can be visited and observed in the southern part of the Central SR in the several famous river and nala cuttings such as Nilawahan, Chiddru, Nammal gorge and Khewra Gorge
The frontal edge of the thrust sheet was folded passively as it overrode the subthrust surface on a Eocambrian salt. The southern part of the SR (Potwar Plateu) is much gentler in term of structural deformation unlike its northern part which is known as North Potwar Deformed zone (NPDZ). The lack of internal deformation of the rear part of the thrust sheet is due to decoupling of sediments from the basement along this salt layer. The age of the thrusting through the stratigraphic evidence, paleomagnetic dating of unconformities, and sediment-accumulation suggest from 2.1 to 1.6 Ma.(Plio-Pleistocene)
Based on the regional cross-section balancing methodology calculated that at least 20 to 23 km of shortening across the ramp have taken place. The rate of Himalyan collision that caused underthrusting of Indian basement beneath sediments in the Pakistan foreland is estimated to be therefore at least 9-14 mm/yr, about 20%-35% of the total plate convergence rate.
Hope, this will help.