Journal of Earth Science, Vol. 27, No. 6, p. 981–988, December 2016
Printed in China
DOI: 10.1007/s12583-016-0681-9
ISSN 1674-487X
Tectonic Study of the Sub-Himalayas Based on Geophysical
Data in Azad Jammu and Kashmir and Northern Pakistan
Muhammad Rustam Khan*, Fahad Hameed, Muhammad Saleem Mughal,
Muhammad Basharat, Sohail Mustafa
Institute of Geology, University of Azad Jammu and Kashmir Muzaffarabad, Azad Kashmir 13100, Pakistan
ABSTRACT: The tectonic study based on geophysical data has been carried out in Sub-Himalayas in
Azad Jammu and Kashmir and northern Pakistan. A series of thin skinned and thick skinned faults
have been delineated in the investigated area on the basis of present study. In the study area compressional stresses caused by the collisional of Indian and Eurasian plates developed the northwestsoutheast trending faults which are Shaheed Gala thrust, Bagh basement fault, Kashmir boundary
thrust and Kawai fault or Indus Kohistan seismic zone. The crustal thickness increases towards north
due to the stacking of the thrust sheets along these faults. The Murree Formation thrusts over the Siwaliks molasse along the Shaheed Gala thrust. This fault dips at an angle of 43º northeast and joins
the thick skinned Bagh basement fault in subsurface which are penetrated up to Moho depth. In the
northeast of Bagh basement fault the northwest-southeast trending Kashmir boundary thrust has been
delineated in the sedimentary-metasedimentary wedge which joins the Indus Kohistan seismic zone in
the subsurface. The present study suggested that the Kawai fault which is running within Murree
Formation cuts 16 km thick sedimentary-metasedimentary wedge and also joins the Indus Kohistan
seismic zone in the subsurface.
KEY WORDS: tectonic study, Sub-Himalayas, Bouguer anomaly, magnetic anomaly, gravity modeling.
0 INTRODUCTION
The Himalaya formed in response to the collision of Indian and Eurasian plates. It is one of the youngest and highest
mountain ranges on the globe with many peaks as high as 7 000
m a.s.l. and above. It is about 2 400 km in length from
Afghanistan-Pakistan in the west and Namcha Barwa in the
east. It varies in width from 250 to 300 km along its length.
The mountain range is arc-shaped, convex southwards with
syntaxial bends at the western and eastern ends (Valdiya, 1980;
Wadia, 1931).
The initial continental collision took place about 50 Ma
ago (Dewey et al., 1988). The southwest and southeast oriented
stresses developed on the eastern and western limb of Hazara
Kashmir Syntaxis (HKS) respectively as a result of this continued collision. These stresses also originated a series of
northwest-southeast oriented thrust system in the core of HKS
(Fig. 1). The HKS is the region of rapid uplift and indicated by
locally increased stream gradients (Seeber and Gornitz, 1983)
and regionally anomalous topography from the recycled origin.
These sediments have been deposited in the core of HKS.
Gansser (1964) subdivided the Himalayas into higher Hima*Corresponding author: [email protected]
© China University of Geosciences and Springer-Verlag Berlin
Heidelberg 2016
Manuscript received January 16, 2016.
Manuscript accepted May 8, 2016.
layas, Lesser Himalayas and Sub-Himalayas. The elements of
Sub-Himalayas are present in the core of HKS (Fig. 1).
The Sub-Himalayan zone extends from Punjab to Assam
and these hills are composed of Siwaliks and Murree molasse.
In the south the folded Siwalik sequence is covered by alluvium. Traces of an active fault, the Himalayan frontal fault cut
the alluvium in the foot hills region. According to Nakata et al.
(1984) this fault is composed of a series of en-echelon fault
which run parallel to strike of the hills between Punjab and
Assam. In the north this sequence is terminated by the main
boundary thrust (MBT), which marks the boundary between
the Sub-Himalayas and the lesser Himalayas.
The present study based on geophysical investigation delineated the structural elements in the Sub-Himalayas which are
developed by the tectonic activities caused by the collision of
Indian and Eurasian plates.
1 GEOLOGICAL SETTING AND DENSITY ZONING
OF THE AREA
The rocks expose in the area under investigation are ranging in age from Precambrian to Pleistocene. On the basis of
geology and densities of the rock units, the area has been divided into three different zones: Siwaliks zone, Murree zone
and the carbonate zone.
1.1 Siwaliks Zone
In the south-eastern and south-western part of the area
molasse of the Siwaliks separated from the molasse of Murree
Khan, M. R., Hameed, F., Mughal, M. S., et al., 2016. Tectonic Study of the Sub-Himalayas Based on Geophysical Data in Azad
Jammu and Kashmir and Northern Pakistan. Journal of Earth Science, 27(6): 981–988. doi:10.1007/s12583-016-0681-9.
http://en.earth-science.net
982
Muhammad Rustam Khan, Fahad Hameed, Muhammad Saleem Mughal, Muhammad Basharat and Sohail Mustafa
Formation by the Riasi thrust and Rawat thrust (RT) respectively (Fig. 2). The measurements show that the average density of this zone is 2.45±0.1 gm/cc.
1.2 Murree Zone
In the western limb of HKS, MBT separated the Murree
Formation from carbonate rocks whereas near the apex and
eastern of HKS, MBT separated the Murree Formation from
Panjal volcanics (Fig. 2). The estimated average density of this
zone is 2.55±0.11 gm/cc.
1.3 Carbonate Zone
Carbonate zone is mainly consisting of limestone and
dolomite. In the north and south-eastern part of the area, the
carbonates are exposed on the surface along the Kashmir
boundary thrust (KBT), MBT and Kotli thrust system. In the
western side Nathia Gali thrust (NT) separated the carbonate
rocks from the Hazara slates (Fig. 2). The average density of
this zone is 2.67±0.08 gm/cc.
2 INTERPRETATION
2.1 Bouguer Anomaly Map
The Bouguer anomaly map (Fig. 3) shows a variation of
-325 mGal in the north and -160 mGal in the south. The contours follow a general trend of northwest-southeast direction in
the northern periphery of the area from Muzaffarabad to
Davelian. In this view the gravity gradient is -2.2 mGal/km.
This abrupt change in the gravity confirms the presence of
Figure 1. Regional tectonic map of the northwest Himalayas in Pakistan (Basharat et al., 2012; Avouac et al., 2006; Greco, 1991; Baig and Lawrence, 1987;
Calkins et al., 1975; Wadia, 1931).
Tectonic Study of the Sub-Himalayas Based on Geophysical Data in Azad Jammu and Kashmir and Northern Pakistan
983
Figure 2. Structural and geological map of Hazara Kashmir syntaxis after Wadia (1928) and Rustam and Ali (1994).
KBT and Kawai fault (KF) or Indus Kohistan seismic zone
(IKSZ) which are also trending in the northwest-southeast direction. In the central part of the area between Rawalakot and
Sudhan Gali, the contours trend is also in the northwestsoutheast direction. In this area the gravity gradient is -3.05
mGal/km. This northwest-southeast trend with abrupt gravity
change demarcates the Bagh basement fault (BBF) of Rustam
and Ali (1994) and Shaheed Gala thrust (SGT). In the area
between Pallandri and Rawalakot and further south near Kotli
region, the negative contours closures have been developed
which converges towards the center indicating the presence of
low density material. The contours follow the trend of Jhelum
fault (JF) in the south-western part of the study area whereas in
the south-eastern part of the area the contours trend change in
northeast-southwest direction in Kotli area. This contours trend
demarcated the Tatta Pani fault (TPF) which cut the Kotli
thrust system.
2.2 Magnetic Anomaly Profiles
The magnetic survey has been carried out after the 2005
Kashmir Earthquake along the profile B–B' and C–C' (Fig. 4).
Rustam et al. (2005) carried out the magnetic survey from
Ghari Habibullah to Naran before the 2005 Kashmir Earthquake (Fig. 5). On the basis of this magnetic study demarcated
the active fault under Kawai area in Kaghan valley. In the present study after the 2005 Kashmir Earthquake the magnetic
data have been carried out along the profile B–B' from Ghari
Habibullah to Kawai in Kaghan valley as shown in Fig. 6a and
along the profile C–C' from Muzaffarabad to Davelian in Neelum valley as shown in Fig. 6b. The abrupt magnetic changes
along these profiles in Kawai and Davelian areas demarcated
KF or IKSZ.
2.3 Gravity Modeling
The gravity modeling has been carried out in the core of
HKS (Fig. 7) by Talwani et al. (1959) technique using software
of Malinconico Jr. (1986) in constrained with the previously
known structural and geological information of Rustam et al.
(2012), Rustam and Khan (2003), Rustam and Ali (1994),
Chaudhry and Ghazanfar (1992), Greco (1989), Valdiya (1984),
Seeber et al. (1981) and Wadia (1931, 1928).
The geological bodies in the area are approximated as
horizontal prisms with finite length and polygonal cross sections. In case of gravity modeling the density contrasts assigned
to geological bodies are relative to the average density of the
crystalline crust taken as 2.95 gm/cc after Rustam and Ali
(1994). The densities assign for Tanol Formation and Hazara
Formation are 2.51±0.08 and 2.53±0.04 gm/cc respectively
after Rustam and Ali (1994).
Modeling has been carried out along northeast-southwest
oriented profile A–A' (Fig. 3) across the major tectonic features
such as the SGT, BBF, KBT and KF or IKSZ. This model is
the outcome of several attempts which were made to have a
best compromise among geology observed gravity and calcu-
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Muhammad Rustam Khan, Fahad Hameed, Muhammad Saleem Mughal, Muhammad Basharat and Sohail Mustafa
Figure 3. Bouguer anomaly map of the study area.
lated gravity. The model demonstrated that the Murree Formation thrust over the Siwaliks along SGT that dips at an angle of
43ºNE. This thrust joins the northwest-southeast oriented BBF
in subsurface that dips at an angle of 75ºNE and penetrated to
the Moho depth. The crystalline crust of Indian Plate is broken
into blocks by this basement fault (Fig. 7).
The model demarcated that the KBT is running within the
Murree Formation on the surface and dips at an angle of 45ºNE
in the subsurface. The KBT joins the IKSZ in the north-east of
Muzaffarabad and penetrated up to Moho depth.
The KF has also been delineated within the Murree Formation on the surface and joins the IKSZ in the subsurface.
This fault dips at angle of 80ºNE and penetrates up to the Moho
depth. The model computed the 38 km thick crystalline crust of
Indian Plate between Kotli and Muzaffarabad area. The total
thickness of crust in Pallandri area is 50 km and in Davelian
Tectonic Study of the Sub-Himalayas Based on Geophysical Data in Azad Jammu and Kashmir and Northern Pakistan
985
Figure 4. Location map of the study area showing the selected profiles.
area the thickness extended up to 54 km. The model also com
puted 12 km thick sedimentary wedge in Kotli area and 16 km
thick in Muzaffarabad area.
2.4 The Integrated Geological and Geophysical Study
The rupture has been observed after the 8th October, 2005
Kashmir Earthquake from Kawai to Davelian area. The 26 km
deep focus of 8th October, 2005 Kashmir Earthquake between
Kawai-Davelian area, magnetic and gravity variations across
the rupture suggested that KF which is running in the sedimentary and meta-sedimentary wedge is upward extension of the
IKSZ. The northwest-southeast trending contours in the
Bouguer anomaly map (Fig. 3) follow the trend of SGT, BBF
and KBT which are running in the Sub-Himalayan zone.
3 DISCUSSION
Rustam and Ali (1994) marked the blind BBF in the core
of HKS between Muzaffarabad and Bagh. The present study
986
Muhammad Rustam Khan, Fahad Hameed, Muhammad Saleem Mughal, Muhammad Basharat and Sohail Mustafa
Figure 5. Magnetic profile from Ghari Habibullah to Naran Pakistan (before 2005 Kashmir Earthquake, Rustam et al., 2005).
Figure 6. (a) Magnetic profile B–B' from Ghari Habibullah to Kawai (after 2005 Kashmir Earthquake). (b) Magnetic profile C–C' from Chella Bandi Muzaffarabad to Davelian (after 2005 Kashmir Earthquake).
Figure 7. Gravity model shows the combined sediments and Moho effects along the profile A–A'.
Tectonic Study of the Sub-Himalayas Based on Geophysical Data in Azad Jammu and Kashmir and Northern Pakistan
indicates that BBF also exists in the sedimentary wedge and
exposed on the surface between Shaheed Gala Rawalakot to
Chatter Muzaffarabad (Fig. 3). The fault breccia has been observed along this fault between Shaheed Gala Rawalakot to
Chatter Muzaffarabad. A series of thrust and strike slip faults
have been developed in the Sub-Himalayan zone (Fig. 3). The
KBT and BBF are trending in the northwest-southeast direction.
The thickness of the sedimentary wedge increases towards
northeast by the stacking of the thrust sheets along these faults.
The folding, faulting and landslides along these faults and tilting of river terraces along the River Jhelum suggested that
thearea is tectonically active. Rustam and Ali (1994) suggested
that the Jhelum strike-slip fault cuts the western limb of HKS
near the apex. The present study suggested that the KBT cuts
the Jhelum strike-slip fault and the Hazara thrust system near
the apex of HKS. The folded and faulted Murree Formation
and Siwaliks molasse are present in the core of HKS. In this
area Siwaliks (sandstone) dips from 70ºNE–80ºNE. These
northwest-southeast trending beds are extended from Kohala to
Tain and Kotli Azad Kashmir. In this area the dip of Murree
Formation is comparatively gentle and is mainly in the northeast direction along Riasi fault and KBT. Verma (1985) suggested that Riasi thrust is extended up to Pallandri Azad Pattan,
20 km south of Tain. Chaudhry and Ghazanfar (1992) suggested that KBT is an extension of Riasi thrust and they extend
Kotli fault up to northeast of Muzaffarabad. The present study
based on gravity data envisaged that KBT is not an extension
of Riasi thrust. It is a thick skin fault and located in Bagh area
30 km northeast of Azad Pattan.
4 CONCLUSIONS
(1) The four northwest-southeast trending thrust faults, i.e.,
SGT, BBF, KBT and KF or IKSZ have been demarcated in the
study area.
(2) The SGT joins the BBF and KBT joins the KF or
IKSZ in the subsurface, and these faults penetrate up to Moho
depth.
(3) The thrust sheet between KBT and MBT in the core of
HKS extending from Kawai to Muzaffarabad and Bagh is
highly imbricated. The short term secondary effects of earthquake like floods, landsliding and liquefaction are expected in
the study area.
(4) The total thickness of crust calculated in Pallandri area
is 50 km and in Davelian area the thickness extends up to 54
km.
ACKNOWLEDGMENT
We are thankful to Prof. Muhammad Sabir Khan, ExDirector, Institute of Geology, University of Azad Jammu and
Kashmir, Muzaffarabad, who provide us every type of facility
in the field and laboratory. The final publication is available at
Springer via http://dx.doi.org/10.1007/s12583-016-0681-9.
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