Geology/structure of salt range
salam sir ....... Hopefully you will be right sir ....
sir i want to know major tectonc structure in salt range ....
i know some fault , fold etc but give me detail or related data .... thanks .....
Dear Samar Abbas,
The Salt Range-Potwar Plateau Fold and Thrust Belt (FTB) forms part of the western Himalayan
Foothills in northern Pakistan. This region is about 200 km wide and ~300 km long and belongs to the larger Alpine-Himalayan Orogenic Belt which extends ~8000 km from Europe across Asia.
The Salt Range is the southern most expression of thrust out mountainous trend of Potwar Plateu where rocks of Precambrian (Salt Range Formation) Paleozoic sequences (Cambrian and Permian) and Mesozoic (Triassic, Jurassic and Cretaceous) and Cenozoic (Paleogene-Neogene) have been present. Salt Range has been considered the museum of Phanerozoic geology due to easy accessibility and outstanding rock exposures and has been site of several academic investigations
It is bound to the north by the Main Mantle Thrust, which separates it from the volcanic and
metamorphic terranes of the Kohistan Arc. To the east and west, the north-south trending Jhelum
and Northwest-southeast trending Kalabagh strike-slip faults limit the FTB,respectively. It was formed by one of the youngest and most external deformation events associated with the Himalayan collision. The Salt Range-Potwar Plateau FTB is a decollement-type FTB,with the Potwar Plateau essentially forming a translated basin, carried southwards on the main decollement thrust, which is located in thick evaporites of the Late Precambrian-Early Cambrian Salt Range Formation.
The region is mainly an oil producer, with many fields producing from anticlinal structures with general E-W trend, changing to a more NE trend further east. Gas and gas condensate are also found in a number of fields. Most fields are located within the Potwar Plateau in a series of narrow, elongate anticlinal trends separated by broad synclines. A broad Soan Syncline which runs Northeast-southwestward almost in the the middle of FTB seperates the northern Potwar from Southern FTB. There are several surface anticlines, to the north and south where commercail oil have been discovered after exploratory drilling. Those key structures on the northern side of Soan Syncline are Khaur, Kot Sarang, Dhulian, Meyal, Toot, Ratana and Dakhni whereas Pindori,Karasal, Balkassar, Chak naurang, Joya Mair and Adhi are to the south. Soan Syncline is generally regarded is the thermally mature kitchen for source rock and site which feeds hydrocarbon to the northern and southern structural traps for accumulation.
In 1866, the first well in northern Pakistan was drilled beside an oil seep near Kundal.
The first commercial discovery in the Salt Range-Potwar Plateau FTB was drilled by the Attock Oil Company at Khaur in the central Potwar Plateau in 1914 followed by Dhulian anticline drilling which was inititaed in 1918 but first successful oil well was completed in 1936 after several drilling failures and produced commercial oil from Eocene carbonates.
Early exploration concentrated on areas around seeps and anticlines with surface expression, but advances in technology led to deeper structures being targeted. The region is immature in terms of exploration, with many anticlinal structures yet to be tested, many potential
reservoirs yet to be reached, both in undrilled areas and below existing reservoirs, and possible structural-stratigraphic plays, such as pinch-outs on anticlinal limbs yet to be investigated. However, of those fields that have been discovered, many are
close to depletion.
The largest field in the region is the Dhurnal Field, with an areal extent
of 21.85 km2 and 230 m of gross hydrocarbon column, and initial in-place reserves of ~55 MMBO.
The second largest field is Dhulian field with ~41 MMBO (discovered in 1936 and still producing) followed by Meyal field (discovered in 1968). Dhulian was also the first Jurassic Datta formation sandstone oil discovery (1959) and probably the first stratigraphic trap at Jurassic Main oil sand level in Potwar basin.
The convergence between the Indian and Eurasian plates since the Late Cretaceous resulted in crustal shortening and uplift of the Himalayan Mountain Range and caused the formation of a number of compressional structures initially in the hinterland of the FTB, before deformation was relocated adjacent to a new frontal thrust that is emergent below the Salt Range 100 km to the south. This unusually large distance between the early and later fronts is due to the presence of the Salt Range Formation,which acted as a ductile substrate and facilitated
thrust propagation. Structures typically encountered are thrust- and salt-cored anticlines, pop-ups and triangle zones, typical of a salt-related, decollement-type FTB. Out-of-sequence deformation is also seen, again typical of deformation involving salt. (This answers was prepared with the help of C&CReservoirs January 2007, AAPG publications and my own publications about the region)
Please let me know if this short answer which covers the large area with greater geological, structural and tectonic variations is sufficient to address your query.
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