Geol. Bull. Punjab Univ. 45, 2010, 1-23 1 PETROLOGY AND PROVENANCE OF THE UPPER CRETACEOUS MUGHAL KOT FORMATION AND PAB SANDSTONE, WESTERN SULAIMAN THRUST AND FOLD BELT, PAKISTAN 3MUHAMMAD AFZAL KAKAR, 1SHAHID GHAZI, 2ABDUL SALAM KHAN, 3AKHTAR MOHAMMED KASI AND 1TANZILA HANIF1 1Institute of Geology, University of the Punjab, Quaid-i-Azam Campus, Lahore-54590 Pakistan 2Centre of Excellence in Mineralogy, University of Balochistan, Quetta-Pakistan 3Department of Geology, University of Balochistan, Quetta-Pakistan Email ID: [email protected] Abstract: The Sulaiman Thrust and Fold Belt-Pakistan comprises of thick Mesozoic succession that was deposited at the northwestern passive margin of the Indo-Pakistan Plate within the Paleo-Tethys. The Mughal Kot Formation is mainly composed of mudstone with subordinate channeled sandstones and rare limestone. The Pab Sandstone is predominantly composed of sandstone with subordinate interbedded shale. The present study is based on data collected from the sandstone packages of Mughal Kot Formation from Mughal Kot and Siazgi sections, while the Pab Sandstone was studied from Mughal Kot and Gwal Haiderzai sections. In the Mughal Kot section, the Mughal Kot Formation is 650 m thick with six packages of channelized sandstone with thickness ranging from 4 to 45 m embedded within the thick mudstone. The petrology of these sandstones was studied and modal analysis carried out in order to classify and understand their detrital modes and provenance. The sandstone has been classified as sub-lithic arenite. The Q-F-L plot indicates a craton interior and recycled orogen. The detritus of sandstone of the Upper Cretaceous Mughal Kot Formation and the Pab Sandstone has been derived from the Indian Craton situated east-southeast of the study area. Keywords: Mughal Kot Formation, Pab Sandstone, Upper Cretaceous, sandstone packages, petrology, provenance INTRODUCTION section of the Mughal Kot Formation by Williams (1959). The Sulaiman Thrust and Fold Belt-Pakistan contains thousands of meters thick Mesozoic succession In the study area the Mughal Kot Formation is 650 m (Fig. 1, and Table 1), which was deposited at the thick (Figs. 2a, 2b, 2c) and comprises dominantly northwestern passive margin of the Indo-Pakistan Plate claystone / mudstone and subordinately siltstone, limestone and sandstone (Fig. 3). Color of mudstone, within the Paleo-Tethys. The succession was first mapped shale and siltstone is grey to greenish grey, which and its lithology was briefly described by the Hunting weathers light grey to dark grey. Sandstone is fine to Survey Corporation (1961). Facies within the Mesozoic medium grained, well cemented and hard. through Paleogene succession from northwest to The term “Pab Sandstone” was introduced by Vredenburg southeast shows an overall general shift from deep to (1908) from the Pab Range in the Kirthar Thrust and Fold shallow marine reflecting basin evolution of the passive Belt. Williams (1959), designated Sumalji Trail, west of margin (Abbas and Ahmed, 1979). Wirahab Nai (Lat: 25° 31’ 12” N; Long: 67° 00’ 19” E) across the Pab Range as its type section, where it is 490 m The term “Mughal Kot Formation” was thick, though its thickness ranges from 204m (Mughal Kot) proposed by Williams (1959), to the strata between the to 1000m (Pab Range). In the study area the Pab Sandstone Parh Limestone and the Pab Sandstone near the consists of dominantly sandstones with subordinate inter Mughal Kot village. The Hunting Survey Corporation bedded shale. The formation is 204m thick at Mughal Kot, (1960) did not identify it as a distinct entity, but 142m thick at Gwal Haidarzai, 48m thick at Siazgi and 7m included it within the lower part of their Pab Sandstone thick at the Spera Ragha (Fig. 1). (Shah, 1977). A section exposed along the Zhob-Dera The aim of this paper is to describe the sandstone Ismail Khan Road (Lat: 31° 26’ 52” N; Long: 70° 02’ petrology and provenance of the Upper Cretaceous Mughal 58” E), west of the Mughal Kot Post, and an adjacent Kot Formation and the Pab Sandstone by collecting data stream, (Toi Nala) has been designated as the type from the Mughal Kot, Gwal Haiderzai and Siazgi sections. 2 Fig. 1 Tectonic map of Pakistan showing location of the Mughal Kot, Gwal Haiderzai and Siazgi sections in the Thrust and Fold Belt. 3 Table 1. The Stratigraphic Succession of the Mughal Kot Area, Sulaiman Fold and Thrust Belt Age Group Formation Lithology Yellowish to greenish grey shale interbedded with Ghazij Eocene layers and lenses of claystone, mudstone, sandstone, Formation limestone and conglomerate Dunghan Medium to thick bedded, massive and nodular Paleocene to Early Eocene Formation limestone with subordinate marl and shale Very fine to fine-grained, light grey sandstone Ranikot Paleocene Interbedded with subordinate, grey arenaceous Formation limestone and siltstone/shale Upper Cretaceous (Middle Fine to medium grained quartzose sandstone and Pab Sandstone to Upper Maastrichtian) light brownish grey shale Upper Cretaceous Grey, argillaceous and highly fossilliferous Fort Munro (Campanian to Early limestone with minor calcareous shale. Formation Maastrichtian) Upper Cretaceous Grey calcareous mudstone and shale with sandstone Mughal Kot (Companion to Early packages. Formation Maastrichtian) Middle Cretaceous Bio-micritic limestone, medium to thick bedded and (Barremian to Parh Limestone light grey to cream colored Santomanian) Parh Group Arenaceous limestone, light grey colored with Early Cretaceous Goru Formation occasional bio-micritic beds Late Jurassic to Early Sembar Belemnitic shale of dark, brownish grey and light Cretaceous (Neocomian) Formation greenish grey color Disconformity Middle Jurassic Chiltan Medium to thick bedded, light to medium grey Limestone colored limestone 4 Fig. 2a Legend showing various geological features observed and shown in subsequent figures 5 Fig. 2b Sedimentary logs (A, B, C, D, E, F, G, H, I, J, K and L) of the Mughal Kot Section, which have been enlarged in Figs. 2c, 2d and 2e. 6 Fig. 2c (See Fig. 2a for symbols) 7 Fig. 2d (See Fig. 2a for symbols) 8 Fig. 2e (See Fig. 2a for symbo 9 Fig. 3 Field photograph showing mudstone dominated sequence of the Mughal Kot Formation with beds of sandstones GEOLOGICAL SETTING OF SULAIMAN region into tectonic-stratigraphic belts such as the THRUST AND FOLD BELT West Pakistan Fold-Thrust Belt (Sulaiman and Kirthar Fold-Thrust Belt), the Bela-Waziristan The study area (Fig. 1) is located within the Ophiolite Belt, the Makran-Khojak-Pishin Flysch Western Sulaiman Thrust and Fold Belt (Bender and Zone, the Indus Basin, the Tethyan Belt and Chaghi Raza, 1995, Bennert, et al., 1992, Jadoon, 1991, and Raskoh Belts. Sarwar and Dejong, 1979 and Wadia, 1953). It includes sedimentary succession from Jurassic to The West Pakistan Fold and Thrust Belt and Eocene age (Table 1), which was deposited on the the associated syntaxial belts (Bender and Raza, northwestern margin of the Indo-Pakistan Plate. The 1995; Jadoon, 1991 and Powell, 1979), like the succession reflects depositional environments and Sulaiman Lobe, are the most distinctive features of volcanic events before, during and after its collision the geology of Pakistan, which developed during the with Eurasian Plate, (Bender and Raza, 1995, Jadoon, collision process when the Indo-Pakistan Plate, also, 1991, Otsuki, et al., 1989, Tepponier, et al., 1981 and underwent basement segmentation. The Sulaiman Powell, 1979). The Paleozoic-Mesozoic succession Lobe (Powell, 1979), about 250km wide, is a festoon- was intensely deformed during the northward shaped belt. It has been established now that the West migration of Indo-Pakistan Plate and is now present Pakistan Fold and Thrust Belt formed in the response in the region of the Sulaiman Thrust and Fold Belt to the collision of Indo-Pakistan continent with the with fragments of oceanic crust, island arcs and Eurasia (Bender and Raza, 1995 and Powell, 1979). ophiolites. This thrust and fold belt consists of a thin-skinned wedge of material, as shallow seismicity is associated Bender and Raza (1995) and Bennert, et al. with it (Molnar and Powell, 1979, Seeber and Jacob, (1992) have systematically subdivided the 1977 and Tepponier, 1975). It indicates that little of northwestern margin of Indo-Pakistan Plate into the the underlying Indo-Pakistan Shield is deformed Sulaiman and Kirthar blocks based on their structural along with the cover sediments. It has been suggested style on satellite images. Also they have divided the by Bender and Raza, 1995, Bennert, et al., 1992 and 10 Powell, 1979 that Pre-Cenozoic basement structures portion, where it is interbedded with arenaceous like basement faults and associated blocks, like the limestone. This portion contains three sandstone Kirthar, Sulaiman and Jehlum blocks, have controlled packages too. The silty shale is of yellowish to the shape of many of the younger ones. greenish color and parallel laminated. The arenaceous limestone is of grey color, nodular with The Bela-Waziristan Ophiolite (Asrarullah, et wavy upper surfaces and obvious parallel and al., 1979, Gansser, 1979, Alleman, 1979 and Abbas cross-stratification. Also small shell fragments and and Ahmad, 1979) shows fragments of oceanic crust intraclasts observed in almost all beds. The abducted on to the Indo-Pakistan Plate during the sandstone is yellowish grey, thin to thick bedded Late Cretaceous, just before the Palaeocene. The (5-60cm) and medium to coarse grained. The classic concept of the Tethys (Deitz and Holden, sandstone beds of every package are amalgamated 1970) is taken as a Mesozoic ocean that existed south and preserve well developed cross-bedding and of the Eurasian Plate. The closure of this ocean gave parallel lamination. Cross bedding is of low to rise to the Alpine Himalayan Ranges (Sengor and high angle (10-27o). Thickening upward trend is Hsu, 1984, Sengor, 1981, Hsu and Benroulli, 1978). common feature of sandstone packages. The The India-Eurasia suture zone in the northern uppermost sandstone package contains mud Pakistan is represented by the Kohistan succession of intraclasts, bioturbation and very thin interbeds of amphibolites, meta-gabbros and associated volcanics silty shale.