Stratigraphy of the area
(Bossart et al. 1984) subdivided the apex of Hazara-Kashmir Syntaxis in to three distinct lithological and structural components by associating the Precambrian and Cambrian Formations with its outer rim, Upper Paleozoic and Mesozoic Formations within Murree and Panjal Thrust and the Tertiary Formations at the core of apex. The Hazara Formation (Precambrian), Tanawal Formation, Abbottabad Formations and Manshera granite (Cambrian) forms the outer rim or the western limb of the syntaxis (Fig. 1; Fig. 2).
Slates and phyllites as a dominant constituent of the Hazara Formation (Fig. 2). They are light gray to black on fresh outcrops but show colour variations such as rusty brown and dark green on the weathered outcrops. Shale, minor limestone and graphite layers are another lithological assemblage within formation. The drags folds and small-scale folding in shale is also developed. The shearing and crushing was observed in slates of Hazara Formation (Fig. 3a). The contact with overlying formation is unconformable and covered with alluvium in the area. The age of this rock formation falls in Precambrian.
In project area the Tanawal Formation is mapped towards west of Panjal Thrust (Fig. 2). The formation includes the metamorphosed argillaceous and arenaceous sequence with the metamorphic grade increasing towards north of the area. The quartzites and phyllites are well exposed in the area. In Garhi Habibullah region the medium grained quartzite and quartz mica schists are well exposed which further grades into the garnet mica schist towards south of Balakot (Bossart et al. 1984). The snowball structures in garnet mica schists were reported by early workers (Bossart et al. 1984). The granitic intrusions within metasediments are common. The shear zone in the area was marked by the alignment of quartzite vein. Drag folds and brecciated beds in the area represents deformed zone due to thrust fault. The Formation has faulted contact with Abbottabad Formation that is concealed with well sorted alluvium. The late Precambrian to early Cambrian age was assigned to this formation.
The Abbottabad Formation was described within core of Muzaffarabad anticline extending from Muzaffarabad to Balakot area (Bossart et al. 1986). The Formation was mapped in Garhi Habibullah and Balakot area (Fig. 2). The dolomite is the dominant constituent of the rocks. The chopboard weathering on dolomite is a diagnostic feature of the formation (Fig. 3b). The dolomite is medium to coarse grained having few calcite veins and forms syn-sedimentary breccia in a highly deformed zone (Fig. 3c). The dolomite also contains chert and organo-sedimentary structures such as stromatolites. Early workers have utilized these stromatolites as an important natural geological field tool in determining the rock facing (Bossart et al. 1986). The alluvium covers most part of formation in study area. The rock units of this Formation are of Cambrian age.
The Tanawal Formation having meta-pelites (Fig. 3d) and meta-psammites of the Pre-Cambrian age is intruded by 516 − 16 my old Mansehra granite (Fig. 2) (Le Fort, 1980), a leucocratic granite with large porphyritic crystals of feldspar. These rock bodies are assumed to represent the southern peripheries of the widespread granitic invasions in the axial regions of Himalaya (Kazmi and Jan, 1997). The age of Manshera granite is lower Paleozoic (Le fort et al. 1980).
The Kuldana Formation is wide-open from Balakot (Fig. 2; Fig. 3e). The formation is mainly composed of shales (Fig. 3f), sandstone, siltstone with quartzite veins and marl with the occasional beds of limestone, and conglomerates. The drag folding, shearing, crushing and breccia also originate in the Formation due to active tectonics. The formation is early to middle Eocene in age.
In project area the alluvial material is most extensively develop in the lower part of the course of the river and contains silt, sand, clay, gravels and a good deal of organic matter. These are Quaternary deposits (Fig. 2).
Structural Style
The main deformations mapped in the area includes folds and regional faults.
Folds
In study area different folds are existing. These folds are either northwest-southeast trending or northeast-southwest trending, northeast or southwest vergent and close to tight in nature (Table 1). These folds include, Garhi Habibullah Syncline, Garhi Habibullah overturned Anticline, Bisian Overturned Anticline and Balakot Overturned Anticline (Table 1) (Fig. 4).
Table 1. Structural details of folds in study area.
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Attitude of bedding
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Axial Plane
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Fold axis
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Inter limb angle
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Fold type
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Folds
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North-eastern limb
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South-western limb
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Ghari Habibullah Syncline
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N25°E/66°SE
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N60°E/54°NW
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N41°E/84°SE
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038°/27°
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69°
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Close
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Ghari Habibullah Overturned Anticline
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N22°W/82°NE
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N30°W/55°NE
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N26°W/77°NE
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157°/10°
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44°
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Close
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Bisian Overturned Anticline
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N22°W/82°NE
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N25°W/45°NE
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N23°W/64°SW
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338°/03°
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37°
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Close
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Balakot Overturned Anticline
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N40°W/75°NE
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N20°W/45°NE
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N32°W/60°SW
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133°/24°
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34°
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Close
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Ghari Habibullah Syncline
The Ghari syncline is exposed near the Ghari area within Abbottabad Formation. The attitude of north-eastern and south-western limbs is N25°E/66°SE and N60°E/54°NW, respectively. The trend - plunge of fold axis, attitude of axial plane besides interlimb angle are 38o/27o, N41°E/84°SE, 69o respectively. The interlimb angle (Table 1) (Fig. 4a) of Ghari Habibullah syncline indicates the close nature of fold.
Ghari Habibullah overturned anticline
The Ghari overturned Anticline is exposed near the Ghari area inside Abbottabad Formation. The attitude of north-eastern and south-western limb are N22°W/ 82°NE and N30°W/55°NE. The trend - plunge of fold axis, attitude of the axial plane in addition interlimb angle is around 157o/10o, N26°W/77°NE, 44orespectively. The interlimb angle the Ghari Habibullah Overturned Anticline places the fold into a closed type (Table 1) (Fig. 4b).
Besian overturned anticline
The Bisian overturned Anticline is exposed near the Bisian area in Tanawal Formation. Mansehra Granite has also intruded the Tanawal Formation in the Project area. The north-eastern and south-western limbs show attitude, N22°W/82°NE-N25°W/45°NE respectively. The fold axis with trend and plunge of 338o/03o and the axial plane with attitude of N23°W/64°NE were analysed. The interlimb angle of 37o places the Bisian Overturned Anticline in to a close type of fold (Table 1) (Fig. 4c).
Balakot overturned anticline
The Balakot overturned Anticline is exposed near the Balakot area in Kuldana Formation. The Kuldana Formation dwells the core whereas Tanawal and Abbottabad Formation cover the limbs. The attitude of north-eastern and south-western limb is N40°W/75°SW- N20°W/48°SW, respectively. The fold axis has trend and plunge equal to 133o/24o while the axial plane has attitude of N32°W/60°NE. The interlimb angle of 34o shows that the Balakot Overturned Anticline is of close fold (Table 1) (Fig. 4d).
Faults
The following faults of regional extent traverse through the rocks in the project area.
Panjal Thrust (PT)
The Panjal Thrust is one of the regional thrust mapped between Abbottabad Formation and Tanawal Formation as the Tanawal Formation was thrusted over the Abbottabad Formation (Fig. 2). The Abbottabad Formation exists in footwall wall while the Tanawal Formation persists in hanging wall. The fault is northeast to southwest trending with the change in altitude of fault plane from north to southwest (Fig. 2). The fault plane’s attitude in south-western part of the project area is up to N53°E/44°NW.
Main Boundary Thrust (MBT)
The Main Boundary Thrust is exposed in Balakot areas (Fig. 2). The Main Boundary Thrust another geological structure of regional significance mapped in the area in which the Tanawal Formation has thrusted contact with the Kuldana Formation in north-eastern part of the project area. The Kuldana Formation subsists as the footwall while the Tanawal Formation exists in the hanging wall (Fig. 2). The MBT is a northeast to southwest trending with the change in fault plane’s attitude from northeast to southwest (Fig. 2). The attitude of fault plane is N21°E/41°NW in north-eastern part and N75°E/62°SE in the south-western part of the area.
Balakot Bagh Fault (B-B Fault)
The Balakot Bagh Fault is the major fault running through the project area (Fig. 2). B-B Fault is mapped between the Cambrian Abbottabad Formation and Eocene Kuldana Formation in the area in which the Abbottabad Formation has a thrusted contact with the Kuldana Formation (Fig. 2). The Kuldana Formation lies within the footwall while Abbottabad Formation lies within the hanging wall of the fault (Fig. 2). The fault plane has attitude of N33°W/55°NE in north-eastern part and N76°W/45°SE in the south-western part of the project area.
The project area forms the sub-Himalayan and lesser Himalayan sequence in outer rim of Northwestern Himalayan Syntaxis that was formed by the deformation of thrust sheets of Himalayas (Bossart et al. 1984; Bilal et al. 2017). The Himalayan orogeny and pre-Himalayan orogenies are the main reason behind these deformations.
The study deals with the stratigraphy and structure of Garhi Habibullah, to Balakot area of Khyber Pakhtunkhwa Pakistan. The Precambrian, Cambrian and Eocene rock sequence is exposed in the project area. The rock formation includes Hazara and Tanawal Formations of Precambrian age, Abbottabad Formation of Cambrian age, Manshera granite of Paleozoic age (Le Fort et al. 1980) Kuldana Formation of middle to late Eocene age which is covered with Alluvium deposits of Quaternary age.
The area is highly distorted by faulting due to Himalayan tectonics. The MBT, PT and Balakot -Bagh (B-B) fault are the regional faults in area.
The project area is highly deformed into a series of folds as a result of Himalayan compression. The major folds are Garhi syncline, Garhi overturned anticline, Bisian syncline and Balakot overturned anticline. The folds are plunging to non-plunging, northwest or southeast vergent and close to tight in nature.
The Kuladana Formation exists in the core of Balakot Overturned Anticline and the Tanawal and Abbottabad Formations forms the limb. Meanwhile, the Abbottabad Formation occupies the core of the Garhi Habibullah syncline and Muzaffarabad anticline (Antonio, 1991).
The Main Boundary Thrust truncates the northwestern and southeastern structural trend of folds and faults in the area. The MBT is responsible for the deformation in lesser Himalayas while the PT has key role in tectonic evolution of lesser Himalayan sequence (Umar et al. 2014). Bossart et al. 1984 related folding and imbricate faulting with the southerly directed movement of Hazara Formation along MBT. The thrusts of external zones toward south were deformed by Hazara Kashmir Syntaxis. The sedimentary deposits of foreland basin within core were tectonically uplifted on the footwall of MBT (Bossart et al. 1988).