Pakistan is located in Indian plate. Before collision of Indian plate with Eurasian plate this plate was a part of Gondwanaland land (South Pole). About 135MY ago India started drifting, along drifting it also rotated. There were three phases of drifting. i.In first phase about 108 MY ago drift speed was slow. It was 4-6 cm per year. ii.In middle phase about 80-55 MY ago speed was high which was 17-25 cm per year. iii.In last phase 50-55 MY ago the speed was 3-5 cm per year. About 135-100 MY ago there was bulging in Indian Ocean formation of Kohistan island arc. Then there formed shear zone. Thrust faulting occurred at MKT. Fractures and cracks formed. The MBT Main Boundary Thrust formed about 11-20 MY ago.
Salt range thrust is the youngest thrust. It formed about 4-5 MY ago. At north of MBT the metamorphism occurred. There is no metamorphism in south of MBT. That is known to be foreland basin.
1.2 HISTORY OF SALT RANGE
The name “Salt Range” was first used by Mounstaurt Elphinstone, a British envoy to the Court of Kabul, who traveled from 1808 to 1815 across the territory. He noted the extraction of Salt in the area and hence named it as “Salt Range”. The Salt Range is a 175 km east-northeast trending rampart that juts out over fluvial plain of the Jhelum River. The Range is a broad U-shaped belt of Pre-Cambrian to Eocene strata south of Potwar Plateau and largely east of the Indus River and North West of River Jhelum, (FIGURE 1).
FIGURE 1: MAP SHOWING THE SALT RANGE, EAST OF RIVER INDUS AND NORTH WEST OF RIVER JHELUM REPRODUCED AFTER GEE, 1980. Due to the excellent exposures and a more or less complete stratigraphic sequence of Phanerozoic rocks, the area is rightly called as “Field Museum of Geology”. Internationally it has generated interest among the scientists for its Permian / Triassic boundary, Pre-Cambrian – Cambrian sequence and abundance of Permian, Mesozoic and Tertiary fauna. In addition a number of Sedimentary minerals occur in the area at different places, the most important are salt, gypsum, anhydrite, coal, silica sand and fire clay.
1.3 LOCATION AND TOPOGRAPHY
The world famous Salt Range is located between latitude 32º-33º North and longitude 70º-72º East (FIGURE 2). It is delineated in the East by River Jhelum and in the West by the Indus River. In the south it rises from the plains of Punjab and in the north it is underlain by the Potwar Plateau. The highest altitude of the Salt Range is the Sakesar Peak, attaining maximum height of 1525 meters. The average altitude varies between 700 and 900 meters.
The Salt Range is divided into two main parts:
i.Cis-Indus Salt Range
ii.Trans-Indus Salt Range
The Cis-Indus Salt Range is situated to the east of River Indus, while the Trans-Indus Salt Range stretches across the Indus in the west, which is also called as the Surghar Range. Geographically the Salt Range is divided into three geographical distributed parts:
i.Eastern Salt Range
ii.Central Salt Range
iii.Western Salt Range
FIGURE 2: MAPS SHOWING LOCATION OF SALT RANGE IN TERMS OF LATITUDE AND LONGITUDE COORDINATES REPRODUCED AFTER KAZMI, 1982.
The Salt Range is connected to major cities of Pakistan through National Highway and Motorway. The Western Salt Range is accessible from Kallar Kahar and Mianwali. The route undertaken for this field trip, starting from Islamabad via Motorway to Kallar Kahar and finally to Mianwali can be seen in (FIGURE 3).
FIGURE 3: MAP SHOWING THE ROUTE UNDERTAKEN FOR THE FIELD TRIP STARTING FROM ISLAMABAD TO MIANWALI.
2.GEOLOGY AND TECTONIC OF SALT RANGE
2.1 TECTONIC SETTINGS OF THE REGION
The Himalayan Orogenic Belt is the youngest mountain chain in the world, which came into existence as a result of collision between the Indian Plate in the South and the Eurasian Plate in the north. The north western Himalayas in Pakistan can be divided into four...