GEOLOGY OF NAMMAL GORGE, THE SALT RANGE, PAKISTANBY MUHAMMAD HAMMAD MALIK INSTITUTE OF GEOLOGY, UNIVERSITY OF THE PUNJAB LAHORE Abstract: Area north of Punjab plains is occupied by a major Thrust known as Himalayan Frontal Thrust (HFT) along which lies Salt Range which occurs on the northern slopes of the Indian Shield. Nammal Gorge is located on the western part of Salt range. In Nammal gorge the strata from late Permian Wargal Limestone to Eocene Murree Formation are exposed. The area is structurally characterized by features like cross bedding, ripple marks; plumose structures, flute casts, burrows and some joints and fractures are present. INTRODUCTION On 28th October, 2008 a field excursion program was organized by Institute of Geology, University of the Punjab, Lahore to Nammal Gorge present in the western part of the Salt range. The Nammal Gorge is located in the western Salt range situated south of Islamabad at a distance of about 200km. from Lahore it is present northward at a distance of 300km. the exact coordinates for Nammal gorge are 3239’54” North and 7148’07” East. The area is easily accessible as it is located on the Grand Trunk Road from Peshawar to Karachi. It took about 5 hours to reach Nammal from Lahore and approximately same from Islamabad. The path in the gorge is rocky, bushy, and unsteady and is along the water channel that comes from the spill of the Nammal Dam. Climate of the area is hot and dry with very low precipitation; average rainfall is about 70-80mm per annum. Maximum rains fall in Monsoon months of July and August. In winter months of December, January and February there is minimum rainfall which makes it best time to visit the Nammal gorge. In Nammal gorge we find mix lithologies. The Late Permian Zaluch Group is mainly limestone having abundant fossils of brachiopods. The famous Permo-Triassic Boundary (P-T Boundary) separates the Chiddru Formation of Zaluch group from Mianwali Formation of Triassic. Tredian Formation is of sandstone while Kingriali Formation largely consists of Dolomitized limestone. The variegated Datta Formation underlies the Shinawari Formation above which Samana Suk Formation is present which comprises of limestone. After the unconformity Hangu Formation is present. The sandstone of Hangu Formation underlies the nodular limestone of Lockhart The Salt range is terminated by the Jhelum strike-slip fault in the east and its western boundary is marked by Kalabagh strike-slip fault. Patala Formation 11. Deformation produce horizontal shortening by folding and faulting. Lack of internal deformation of the rare part of the thrust sheet is due to decoupling of sediments from the basement along this salt layer. STRATIGRAPHY: 14. Samana Suk Formation 7. The monocline structure of the Salt range represents rocks belonging from the Cambrian to recent in age.6 to 3. The quarries of limestone present here are fulfilling the needs of cement factories as well as construction purposes. Nammal Formation 12. Hangu Formation 9. Cross-section balancing demonstrate at least 20 to 23 km of shortening across the ramp.2 million years ago. diapiric emplacement of evaporites and uplifting of the Salt range. The salt layer permitted the rapid propagation of the basal detachment frontal ramp at the southern termination of the basin. Chichali Formation 8. The frontal part of the thrust sheet was folded passively as it overrode the sub-thrust surface on a ductile layer of Eocambrain salt. The evaporites sequence is an effective zone of decoupling allowing thrusting to extend more than 100km south of MBT without involving basement. The youngest Salt range thrust appears 1. Large quantities of limestone. Shinawari Formation 6. sandstone and silica sand are being extracted from the gorge. Sakesar Limestone 13. About 1km offset of the basement normal faults acted as a buttress that caused the central Salt range-Potwar plateau thrust sheets to ramp to the surface. This collision changes the sedimentation style from shallow neritic environment to fluvial system. Kingriali Formation .Formation. The salt range is the surface expression of the leading edge of the decollement thrust that resulted from sediment decoupling from the northward drifting basement of Indian shield and essentially a complex salt anticlinorium with a series of salt anticlines. Shales of Patala Formation are present above which Nammal Formation and Sakesar Limestone are present. Economically Nammal gorge is very important. Lockhart Limestone 10. The rate of Himalayan convergence that can be attributed to under-thrusting of Indian basement beneath sediments in the Pakistan foreland is therefore at least 914mm/year about 20%-35% of the total plate convergence rate. Datta Formation 5. exposing Mesozoic and Paleozoic strata. TECTONIC AND STRUCTURE: The Salt range is the active frontal thrust zone of the Himalayas in Pakistan. siltstone and dolomite which is thickest in the west and wedges out towards the east. These members are not recognized in Kala Chitta area. The formation is 121m thick in Zaluch nala while in Tappan Wahan section it ranges from 135m to 187m. Mianwali Formation 2. The formation is 183m thick in Zaluch nala while in Marwat and Khisor ranges it is about 174m. limestone and dolomite. The formation has a transitional contact with underlying Wargal formation while its upper contact is marked by a major unconformity the P-T boundary above which is the Mianwali formation of Triassic age. brownish grey and olive green colors. The formation at the base is composed of shale unit of yellowish grey to medium dark grey color with small phosphatic nodules. Lithologicaly the formation is composed of limestone and dolomite of light grey to medium grey. The contact of Wargal limestone with underlying Amb formation is confirmable while upper contact with Chiddru formation is transitional. Chiddru Formation: The name Chiddru formation was introduced by Dunbar (1932) to the “Chiddru beds of Waagen (1891) and “Chiddru group” of Noetling (1901). The top most part is a white sandstone bed which is medium to fine grained with subordinate shale partings and contains abundant fossils. The formation was divided into three members in the Salt range and Trans Indus ranges by Waagen which were also recognized by Kummel (1966). Its type section is Wargal village in the central salt range. Wargal Limestone Wargal Limestone: The name “Wargal limestone” was approved by the Stratigraphic Committee of Pakistan proposed by Teichert (1966) to the unit formerly known as “Middle Products limestone” of Waagen (1879) and “Wargal group of Noetling (1901). Tridian Formation 3. In Zaluch nala the formations lithology is divided into 10 parts which shows alternate beds of sandstone. sandstone. Lower contact of the formation is marked by the P-T boundary wile its upper contact with Tredian formation is sharp and well defined. . Mianwali Formation: Gee (in Pascoe. 1959) used the name” Mianwali Series” which was later modified by Kummel (1966) into “Mianwali Formation”. Chiddru Formation 1. The formation represents a great wedge of varied facies consisting of marl. limestone.4. Above shale beds of calcareous sandstone with few sandy limestones are present. The formation is mainly of continental origin and consists of variegated colored sandstone. reddish grey to greenish grey and is thin to medium bedded. Shinawari Formation: The term “Shinawari formation” was introduced by Fatmi and Khan (1966) . Trans Indus ranges. The formation consists of two members the lower “Landa member” and the upper” Khatkiara member”. The contact with underlying Mianwali formation is sharp while with overlying Kingriali formation is gradational. The formation is widely developed in the Salt range. Datta Formation: The name Datta formation was introduced by Danilchick and Shah (1967) for the “variegated stage” of Gee (1945). At type locality the formation is 212m thick but increases to 230m in Punnu nala to the west and over 400m in Sheikh Badin Hills. fine to coarse textured. Kingriali Formation: The name “Kingriali formation” was given to the “Kingriali Dolomite” of Gee (1945). part of Kala Chitta. The formation consists of thin to thick bedded. massive. Kohat and southern Hazara. The upper contact with Shinawari formation is gradational. ferruginous glass sand and fireclay horizons. The formation overlies unconfirmably on the Kingriali formation in Salt range and Trans Indus ranges while in Hazara it rests unconfirmably over the Precambrian Hazara formation. The lower contact with Tridian formation is confirmable. light grey to brown dolomite and dolomitic limestone with interbeds of greenish dolomitic shale and marl in the upper part. The sandstone is micaceous and varies in color from pinkish. The upper contact with Datta formation is disconfirmable and shows development of Ferruginous dolomite and uneven surface at the contact. The formation is 1560m in Tappan Wahan section of the Khisor range and 76m in Zaluch sections of salt range. The name originates from the Kingriali Peak of the Khisor range. thick bedded white sandstone with inclusions of some dolomite in the upper part. The Khatkiara member is massive. The fireclay is present mainly in the lower part.Tredian Formation: The name “Tridian formation” was introduced by Gee (in Kummel. carbonaceous. In Nammal gorge area the thickness is 150m which reduces further as we move towards east. The Landa member consists of sandstone and shale. shale. siltstone and mudstone with irregularly distributed calcareous dolomitic. 1966) to replace his earlier name “Kingriali sandstones”. The Tredian formation is generally non-marine unit that succeeds the Mianwali formation. At the type locality the formation consists of thin to well bedded limestone with nodular marl. Hangu formation: The “Hangu Shale” and “Hangu sandstone” of Davies (1930) from Kohat area have been formalized by the . generally unfossiliferous sandstone. The limestone is oolitic and in Hazara and Kala Chitta it includes some dolomitic and ferruginous sandy. splintery. The name Samana Suk is derived from the peak of this name in Samana Range. calcareous and noncalcareous shale and quartzose. The shale is grey to dark grey. In western salt range it has three members. Chichali formation: This formation was established by Danilchick and Shah (1967) for rocks previously described as the “Belemnite beds” from the salt range and Trans Indus ranges. The lower contact with the Samana Suk formation is disconfirmable. The limestone is grey. The upper member is glauconitic chamositic. medium to thick bedded limestone with subordinate marl and shale intercalations. In Chichali area the thickness is 55m to 70m while in southern Hazara on Haro River it is 33m. and “lower part of Kioto limestone” of Cotter (1933) after the village of this name in western part of Samana Range in Kohat. fine to coarse textured and contains sandy. The type section is Chichali pass in Surgar range. calcareous and non-calcareous. Samana Suk Formation: Davies (1930) introduced name “Samana Suk” for the Jurassic limestone in Samana range formerly named as “kioto Limestone” of Middle miss (1896) and Cotter (1933) and “Daulatmar Limestone” of Calkins and Matin (1968). Lower member with glauconitic shale with some phosphatic nodules passing upward into dark green glauconitic sandstone with abundant Belemnites. At the type locality the formation consists of dark green. oolitic beds but these are absent here in Nammal area. The formation has a transitional contact with the underlying Datta formation and overlying Samana Suk formation. weathering rusty brown glauconitic sandstone with dark grey sandy. The lower contact is transitional with Shinawari formation while upper contact with Chichali formation is disconfirmable. In the type locality the formation consists of grey. Trans Indus ranges. Kohat. ferruginous sandstone. Hazara and Kala Chitta.to the “Lowest Samana Beds” of Davies (1930). At the type locality thickness is 186m while in Bagnotar section Hazara it is 366m. The formation is widely distributed in western salt range. oolitic and ferruginous beds. silty glauconitic shale in the lower part. The upper contact with Lumshiwal formation appears gradational. brownish grey. grey. shale.Stratigraphic Committee of Pakistan. The limestone is well developed and 60m thick at type locality. massive. rubbly and brecciated at places and flaggy at basal part. in places carbonaceous and calcareous acd also contains marcasite nodules. The formation is 90m thick at the type section. The formation conformably and transitionally overlies and underlies the Hangu formation and the Patala formation respectively. Nammal Formation: The term “Nammal formation” has been formally accepted by the Stratigraphic . In Nammal area the sandstone is dark colored and variegated rarely. In salt range Nammal area the limestone is grey to light grey. Patala Formation: The term “Patala formation” was formalized by the Stratigraphic Committee of Pakistan for the Patala shale of Davies and Pinfold (1937) and “Nummulitic formation” of Waagen and Wynne (1872). Coal seams of economic importance are present locally. In salt range the formation consists of shale and marl with subordinate limestone and sandstone. carbonaceous shale and some nodular argillaceous limestone. Thickness of Patala formation at type locality is 90m while at Khewra it is 27m thick. At type locality the limestone is grey. Patala nala in Salt range is its type section. It is about 70m thick in Nammal gorge and 242m in Hazara area. There is an unconformity and is underlain by Chichali formation in Nammal while is conformably overlain by Lockhart Limestone.. medium to thick bedded. The limestone is white to grey and nodular and occurs as interbeds. fine to coarse grained and medium to thick bedded. A section near Fort Lockhart in Samana range is designated as a type section. nodular with minor amounts of grey marl and dark bluish grey calcareous shale in he lower part. Patala formation conformably overlies the Lockhart limestone and is conformably and transitionally overlain by Nammal formation in Salt range. Lockhart Limestone: Davies (1930a) introduced the term “Lockhart Limestone” for Paleocene limestone unit in Kohat area formerly known as ”Nummulitic Series” of Middle miss (1896). A section south of Fort Lockhart is designated as its type section. The Hangu formation consists of sandstone with grey shale intercalations in upper part. The shale is dark greenish grey. weathers dark rusty brown. Subordinate interbeds of yellowish brown sandstone are present in the upper part. light grey and reddish brown. 50m at Hangu and about 35m in Mandeha Banni in Hazara. The sandstone is white. medium to thick bedded. selenite bearing. It is 30m thick in Khewra-Choa Saiden Shah road section in eastern Salt range. nodular. As we enter the gorge we see big quarries where limestone is being extracted from Wargal Limestone and Chiddru formation. The lower contact with Patala formation and upper with Sakesar limestone are transitional. The lower contact with Nammal formation is confirmable. marl and limestone may act as source. The formation comprises of shale. The shale is grey to olive green while the limestone is light grey to bluish grey. The upper part has dominantly limestone. In eastern salt range upper contact with Chorgali formation is confirmable while in central and western part. Near Daud Khail in western salt range the limestone grades into white to grey massive gypsum. reservoir and seal within the formation. The marl is also light grey to bluish grey. Silica sand from Datta formation is widely used in glass and ceramic industry.Committee of Pakistan for the “Nammal limestone and shale” of Gee (1935) and “Nammal Marl” of Danilchick and Shah (1967). The formation is 100m thick at Nammal gorge and thins out westward to 60m at Khairabad. This limestone not only feeds the cement and construction industries but also has very important use as aggregate in roads and highways. Economic Importance: The Nammal area in the western Salt range is important for economic point of view. Rawalpindi group overlies it conformably. The marl is cream colored and forms a persistent horizon near the top. The section exposed in Nammal gorge is its type section. It acts as a source for various economically important minerals which are used in different industries. The formation is widely distributed in salt range where the thickness ranges from 70m to 150m. The limestone throughout its extent is cream colored to light grey. Sakesar Limestone: The term Sakesar limestone was introduced by Gee (in Fermor. The limestone Is argillaceous in places. So Sakesar limestone is used for this purpose. The Eocene succession also has its own significance as it fulfills all the basic requirements of a complete Petroleum Play system. The unit consists dominantly of limestone with subordinate marl. Shale and marl of Nammal formation is used in cement industry but its limestone is not good. Sakesar peak in the Salt range has been designated as its type locality. marl and limestone. In salt range these rocks occurs as alternations. usually massive with considerable development of chert in the upper part. In Surgar range lower part consists of marl and shale with minor limestone. . 1935) for the most prominent Eocene limestone in the salt range and Trans indus ranges. Shale. pp.. and Pinfold.R. E. Davies. 1935. The Eocene beds of the Punjab Salt range: India Geol. Recent observations on the Cambrian sequence of the Punjab Salt Range: India Geol. .228-231. 15p. The Paleocene Foraminifera.24. E.S. Paper 424-D. Mem... Davies. 1937... Indica. New Series.. pt. 68. 1930a. 1961.de P. Mianwali Distt.. Prof. v.63. Mem. New Series.G.1. Surv.. v.. west of Longitude 7245’ E: India Geol. Paleont. Indica. The fossil fauna of the Samana Range and some neighbouring areas: Part 6.v.. 79p. Surv. pp. Surv.15.“REFERENCES” Cotter.115-120. 1933.. An Introductory note: India Geol. Surv. The geology of the part of Attock District. The Iron formation of the Surgar and western Salt Range.pp. Mem. Ress. Paleont. W.55. West Pakistan: U.. Gee. v.1. Surv. no.S Geol. Danilchik..