Field Report of Attock Cherat Range pdf

1. 1
STRATIGRAPHIC STUDY OF ATTOCK-CHERAT RANGE
BY
Muhammad Aslam Khan
Report Submitted To Muhammad Awais Lecturer Geology
Department, University Of Swabi.

2. 2
Introduction
The Attock-Cherat Range is divided into three east-west trending blocks that are bounded
by thrust faults. From north to south these are listed as Northern Block with unfossiliferous
argillite, slate, phyllite and limestone of Precambrian age intruded by dolerite sills and dykes; the
central block comprising unfossiliferous flysch of Precambrian age and overlain by Jurassic,
Cretaceous, Paleocene, Eocene, Miocene rocks, and the Southern Block consisting of
unfossiliferous limestone, dolomite, argillite and quartzite overlain by Tertiary sequence similar
to that found in Central Block (Yeats and Hussain). The rock sequence in the southern part of the
mapped area includes an extension of the main Kala-Chitta Range.
Station # 1
In station “1”, the sequence of rocks were consist of conglomerate and slates of Manki
Formation. The conglomerate was in contact with slates and the contact was unconformable. The
conglomerate was on the top of slates. On the basis of GPS data (33°52'50.60" N and 72°13'47.20"
E) satellite image of the study area is shown in figure-1 and a field image in figure-2.
Figure-1: Satellite image of the study area.
River Indus

3. 3
Figure-2: Field image of study area (camera facing west direction and men are for scale).
These conglomerates are formed by consolidation and lithification of gravel. Conglomerate
present there was consisted of cobbles, pebbles, granules and large blocks of allochthonous
limestone. Large blocks of limestone present in the conglomerate were so near to each other which
can be seen in figure-3.
Figure-3: Limestone blocks in conglomerate (camera facing west direction, men are for scale).

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Structural Features
On the way to station “2”, there was mud cracks which is a sedimentary structure, these
are polygonal shaped cracks formed when mud was dewatered, shrink and leaves the cracks. This
tells that mud was saturated and then expose to air. They are also called as desiccation cracks. Mud
cracks are shown in figure-4. The next structural feature was Chevron fold; a fold with sharp
angular hinge and planar limbs of equal length. The inter-limb angle in chevron fold is generally
up to 60 degrees. Chevron fold is shown in figure-5.
Figure-4: Mud cracks (bottle is for scale).
Figure-5: Chevron fold (camera facing west direction, geological hammer is for scale).

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Station # 2
In station “2”, there was an anticline in Darwaza limestone in which one limb was dipping
towards the north direction and other towards the south direction. Argillites were present on top
of the limestone. Limestone was in grey color and thick bedded while argillite was yellowish-
brownish color and thin bedded. On basis of GPS data (33°51'46.60" N and 72°14'00.60" E)
satellite image of the study area is shown in figure-6 and a field in figure-7.
Figure-6: Satellite image of the study area.
Figure-7: Study area (camera facing east direction).

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Strike and Dip
The strike and dip data measured in the field is given in the following table:
Strike
095
100
170
120
135
125
130
145
135
133
Dip
70
67
44
50
85
68
70
58
66
57
Sense
S
S
SW
SW
SW
SW
SW
SW
SW
SW
The strike and dip data plotted on stereonet is shown in figure-8.
Figure-8: Picture showing strike and dip.