Basins of Pakistan

1. SEDIMENTARY BASINS
AND THEIR EVOLUTION

2. 1. In terms of genesis and different geological
histories, Pakistan comprises two main
sedimentary basins
a. INDUS BASIN
b. BALOCHISTAN BASIN,
2. This evolved through different geological
episodes and was finally welded together
during Cretaceous/Paleocene along Ornach
Nal/Chaman Strike slip faults.
3. There is yet another newly identified smaller
basin, termed as Kakar-Khorasan Basin (Fig.
4.1) also referred to as Pishin Basin, which
carries its own geological history for most of its
development.

3. 1. This basin came into existence due to the
interaction of Indian and Eurasian plates and is
classified as Median Basin.
2. The geological history of the Indus Basin goes
back to Precambrian Age.
3. The Paleotopographic features, shown on the
gravity map of Pakistan, influenced, to a large
extent, the depositional processes throughout the
basin development.
4. The ongoing tectonic processes further enhanced
and modified the configuration and gave rise to
some new ones creating an array of modern
basins is the gravity map of Southern Indus Basin.

4. 5. The main feature which controlled the
sedimentation in the proto-indus Basin up to
Jurassic was Precambrian Indian Shield whose
topographic highs exist in the form of Kirana Hills
(Sargodha High) and Nagar Parkar Ridge.
6. It is the Sargodha High which is considered to be a
divide between Upper Indus Basin and Lower
Indus Basin '(Fig. 1).
7. The Early Jurassic saw the first breakup of the
supercontinent Pangea which disturbed the
equilibrium.

5. • Following is the classification of Indus Basin:
1. Upper Indus Basin: Kohat sub-Basin
Potwar sub-Basin
2. Lower Indus Basin: Central Indus Basin
Southern Indus Basin
• In addition to these, two modem basins are also
recognised which are Peshawar Basin and
Campbellpur Basin.
• Another term, Siwaliks Basin signifies all the
trough areas in Indo-Pakistan sub-continent;
formed at the expense of Himalayan Orogeny,
they received tectonic shed of positive areas.

6. • Another major feature of basement topography,
as seen on gravity data, is Khairpur-Jacobabad
High and its associated structures which grew
through Jurassic and Cretaceous/Paleocene
ages and divided the Lower Indus Basin further
into two basins namely
a. Southern Indus basins
b. Central Indus basins (Fig.1).

7. Figure - 4.1 Sedimentary Basins of Pakistan (after Abul Farah et al, 1984)

8. UPPER INDUS BASIN
1. This basin is located in the northern Pakistan
and is separated from the Lower Indus Basin by
Sargodha High (Fig. 4.1).
2. The northern and eastern boundaries coincide
with the Main Boundary Thrust (MBT)
3. The southern most of the major Himalayan
thrusts.
4. The MBT runs through the Margala Hills, Kala
Chitta and Kohat Ranges.
5. Western boundary of the basin is marked by an
uplift of Pre-Eocene sediments and east¬ward
directed thrusting to the west of Bannu.

9. • The basin is further subdivided into
1.Potwar, to the east
2.Kohat, to the west, by river Indus (Fig. 4.6).
• Potwar sub-Basin preserves the sediments from
Precambrian to Quaternary age in the subsurface and
all of these are exposed in the Salt Range - a
southernmost thrust.
• The Trans-Indus Ranges in south of the Kohat sub-
Basin (Fig. 4.6) expose sediments from Cambrian to
Pliocene age.
• Both Kohat and Potwar sub-basins are characterized
by an unconformity between Cambrian and Permian.
• Mesozoic sediments are also exposed around the
basin rim

10. FIGURE - 4.6 STRUCTURAL MAP OF KOHAT-POTWAR DEPRESSION (AFTER
KHAN ET AL. 1986)

11. • However, their presence is governed by Pre-
Paleocene erosion which progressively cut into
the older sequence from the Trans-Indus Ranges
in the west to East Potwar through Salt Range.
• In the Kohat sub-Basin, west of the Potwar sub-
Basin, Eocene through Siwaliks strata are
involved in a complex fold and thrust belt in
which Eocene Salt occupies the cores of many of
the anticlines.
• More over, Paleocene and Eocene stratigraphy is
more complete in Kohat sub-Basin.
• The Upper Indus Basin stratigraphy is shown in
Fig. 4.4.

12.  The Central and Southern
Indus basins are separated by
Jacobabad and Mari-Kandhkot
highs (Fig. 4.1) together termed
as the Sukkur Rift (Raza et al,
1989).
 The latter has acted as a basin
divide since Jurassic times.
 On gravity and magnetic
anomaly data these Highs
represent a very deep subsurface
wedge of upper mantle or
oceanic crust.
 The Highs have been active since
Jurassic times and at least up to
Paleocene, as Paleocene strata
are missing along the crest and
its surrounding areas.
Central
Indus
Basin:
(Sulaiman
sub-Basin),
a. Punjab Platform
b. Sulaiman Depression
East Sulaiman Depression
Zindapir Inner Folded
Zone
Mari Bugti Inner Folded
Zone
c. Sulaiman Fold Belt
Southern
Indus
Basin
a. Thar Platform (Sindh
Monocline)
b. Karachi Trough
c. Kirthar Foredeep
d. Kirthar Fold Belt
e. Offshore Indus
LOWER INDUS BASIN (SOUTHERN AND CENTRAL INDUS
BASINS)

13. CENTRAL INDUS BASIN
• The basin is separated from Upper Indus Basin by
the Sargodha High and Pezu uplift in the north.
• It is bounded by Indian Shield in the east, marginal
zone of Indian Plate in the west, and Sukkur Rift in
the south (Fig. 4.7).
• The oldest rocks exposed in this basin are of
Triassic age (Wulgai Formation) while the oldest
rocks penetrated through drilling are of
Precambrian Salt Range Formation on Punjab
Platform.

14. • The depth to the basement is about 15,000
meters in the trough areas.
• Pre-Himalayan non- urogenic movements
have resulted in prolonged uplifts/sea
regression causing unconformities which
have led to the large gaps in succession.
• Precambrian rocks are largely missing
from the basin, although Precambrian shield
rocks are evident along the rim of the Indian
Plate.
• Cambrian aged shallow marine rocks are
recorded in Karampur well (Shell -1958).

15. FIGURE:
Central Indus
Basin and
the
subdivisions
Into
Petroleum
zones(after
Raza etal.
1989)

16. • In the Lower Indus Basin the oldest rocks
(Triassic Wulgai Formation) are exposed
in this region.
• The most important lithostratigraphic varia-
tions observed in Sulaiman Depression and
the Fold Belt is in Paleocene/Eocene.
• This period marks the facies changes from
north to south and east to west.
• The reason for this variation is believed to
be the presence of a number of new
basins at that time, created due to the
collision of plates and their irregular and
non-uniform coalescence

17. • The basin comprises, from east to west,
three main units (Fig. ) on the basis of the
topography of Indian Shield and later
development
1. Punjab Platform
2. Sulaiman Depression
3. Sulaiman Fold Belt

18. . PUNJAB PLATFORM
1. Shows no surface outcrops of sedimentary rocks.
2. Tectonically, it is a broad monocline dipping
gently towards the Sulaiman Depression.
3. The Pre-Cretaceous non-orogenic movements
tilted the area eastward during the Paleozoic and
westward since Mesozoic resulting from the
collision of Indian and Eurasian plates.
4. Punjab Platform is tectonically the least affected
area because of its greater distance from collision
zone.
5. A number of wells have been drilled on this
platform.

19. SULAIMAN DEPRESSION
1. This depression was formed as a result of the
collision between two plates.
2. The western flank of the depression includes
Zindapir Inner Folded Zone
3. while Mari Bugti Inner Folded Zone lies in the
south;
4. To the east it merges into Punjab Platform.
5. On seismic evidence the area shows some buried
anticlines (e.g. Ramak) which may have been
formed at the expense of flow of Eocene shales.

20. SULAIMAN FOLD BELT
• This is a major tectonic feature in the nearness of collision
zone and, therefore, contains a large number of disturbed
anti¬clinal features.
• Unlike the Upper Indus Ba¬sin, the decollement zone in this
part was possibly provided by shales.

21. SOUTHERN INDUS BASIN
• This basin (Fig.) is located just south of Sukkur
Rift - a divide between Central and Southern
Indus basins. It comprises the following four
main units:
1. Thar Platform
2. Karachi Trough
3. Kirthar Foredeep
4. Kirthar Fold Belt
5. Offshore Indus
• The platform and trough extend into the
offshore Indus.
• The Southern Indus Basin is bounded by the
Indian Shield to the east and the marginal zone
of Indian Plate to the west.

22. • Its southward extension is confined by off-shore Murray
Ridge-Oven Fracture plate boundary.
• The oldest rocks encountered in the area are of
Triassic age (Jhat Pat and Nabisar wells).
• Central and Southern Indus basins were undivided
until Lower/Middle Cretaceous when Khairpur-
Jacobabad High became a prominent positive feature.
• This is indicated by homogeneous lithologies of
Chiltian Limestone (Jurassic) and Sembar Formation
(Lower Cretaceous) across the High.
• Sand facies of Goru Formation (Lower-Middle
Cretaceous) are also extending up to Kandhkot and
Giandari area.
• Paleocene facies south of the High are quite different
from those in norths and are dominated by clastic
sediments derived from the positive areas (Khairpur-
Jacobabad High and Nabisar Arc).

23. Figure - 4.9
Structural Setting
of Southern Indus
Basin (Modified
after Quadri &
Shoaib, 1986)

24. 1. THAR PLATFORM
1. It is a gently sloping monocline analogous to Punjab
Platform controlled by basement topography.
2. The sedimentary wedge thins towards the Indian Shield
whose surface expressions are present in the form of
Nagar Parkar High.
3. It is bounded in the east by Indian Shield, merges into
Kirthar and Karachi Trough in the west and is bounded in
the north by Mari-Bugti Inner Folded Zone.
4. The Platform marks very good development of
Early/Middle Cretaceous Sands (Goru) which are the
reservoirs for all the oil/gas fields of British Petroleum
(BP) and Oil Gas Development Corpo¬ration in this
region.

25. 2. KARACHI TROUGH
• It is an embayment opening up into the Arabian Sea.
• The Trough is characterised by thick Early Cretaceous
sediments and also marks the last stages of marine
sedimentation.
• It contains a large number of narrow chains like anticlines,
some of which contain gas fields (Sari, Hundi & Kothar).
• It has been a trough throughout the geological history.
• The most interesting feature of Karachi Trough is the
reportedly continued deposition across the Cretaceous /
Tertiary (K/T) boundary where in Korara Shales were
deposited, the basal part of which represents Danian
sediments.
• This localized phenomenon probably represents a unique
example where no hiatus(break) in sedimentation

26. 3. KIRTHAR FOREDEEP
 Kirthar Foredeep trends north-south which has received
the sediments aggregating a thickness of over 15,000 meters
 It has a faulted eastern boundary with Thar Platform. It is
inferred that the sedimentation had been continuous in this
depression.
 However, from the correlation of Mari, Khairpur and
Mazarani wells it appears that the Upper Cretaceous
would be missing in the area.
 Paleocene seems to be very well developed in the
depression but is missing from Khairpur-Jacobabad High
area.
 This depression, like Sulaiman Depression, is the area of
great potential for the maturation of source rocks.

27. 4. KIRTHAR FOLD BELT
• This north-south trending tectonic fea¬ture is similar
to Sulaiman fold belt in struc-tural style and
stratigraphic equivalence.
• Rocks from Triassic to Recent was depos¬ited in this
region.
• The configuration of the Kirthar fold belt also marks
the closing of Oligocene-Miocene seas.
• The western part of the Kirthar fold belt adjoining the
Balochistan basin, which marks the western edge of
the Indus basin, is severely disturbed.
• This western margin is associated with hydrothermal
activities which resulted in the formation of economic
mineral deposits of Baryte, Fluorite, Lead, Zinc and
Manganese.

28. 5. OFFSHORE INDUS
• The part of passive continental margin and appears to
have gone through two distinct phases of geological
history (Cretaceous-Eocene and Oligocene-Recent).
• Sedimentation in offshore Indus region started from
Cretaceous time.
• However, deltaic and submarine fan sedimenta¬tion
has occurred since middle Oligocene time with the
inception of Proto-Indus System.
• Offshore Indus is divided into Platform and Depression
along a Hinge Line in close proximity and parallel to
67°E Longitude (Fig. 4.11).
• Offshore Platform is divided into Karachi Trough and
the Thar Platform's deltaic area by a line which divides
Karachi Trough from Thar Slope onshore (Fig.).

30. KAKAR KHORASAN BASIN (PISHIN BASIN)
• This basin (Fig. 4.1) has been recently recognized as
separate entity from Indus and Balochistan basins in that
it has evolved through different geological processes and
has an independent tectonic style.
• The basin is located between Chaman Fault in the north
and northwest and obducted ophiolitic margin of Indian
Plate in the south.
• In the north it extends (about 50%.) into Afghanistan and
is known as Kundar-Urgun Basin.
• Tertiary sedimentary fill is probably underlain by oceanic
crust or very thin continental crust.
• This is confirmed by the presence of ophiolites at its
southern margin and presence of Precambrian basement
in the north in Helmund and Kabul blocks.

31. 6. BALOCHISTAN BASIN
• This Basin onshore-offshore basin, covers an area of
about 300,000 sq. km, is the least explored in Pakistan.
• Only six wells have been drilled in the region to date.
• What is more, these were abandoned either due to
operational difficulties or geological complexities.
• No commercial hydrocarbons have so far been proven in
the basin.
• In the east, Basin (Fig. 17.1) by Chaman Transform Zone
whereas the western part extends into Iran.
• This basin presents a different geological history
compared to the Indus Basin; that of an arc-trench
system from north to south where Arabian Oceanic Plate
is subducting beneath the continental margin of Eurasian
Plate (Lut and Afghan blocks).

32. Figure -17.1
Balochistan
Basin (after
Farah et al,
1984)

33. • From south to north this arc-trench system is divided into
Makran Trench, Coastal Makran Depression, Makran (Panjgur)
Accretionary Prism, Hamun-i-Mashkel (Kharan) Fore-Arc Basin,
Ras Koh Arc, Mirjawa-Dalbandin Trough (Inter Arc region) and
Chagai Arc.
• Makran Coast is a great festoon of folded and faulted Tertiary
sediments ex¬tending 800 km from Las Bela axial fold belt on
the east to the Oman line on the west.
• The subduction of oceanic crust under the Makran region of
eastern Iran and western Pakistan started in Late Cretaceous and
is continuing through modern times.
• This led to the generation of Arc-Trench system which is known
to be widest in the world.
• The Arc-Trench gap is of the order of 500 km, far wider than
most systems.
• The examples with unusually large arc-trench gaps are found in
northern New Zealand and the Gulf of Alaska.

34. • This Arc-Trench system is unique in a number of ways:
1. Fore-Arc Basin and most of the Accretionary Prism are
emergent, thus making surface geological
investigation possible,
2. Even intense deformation has not created structural
incoherence in the exposed strata.
• The sedimentary rocks exposed in Balochistan Basin range
in age from Cretaceous to Recent with older rocks exposed
in the north and younger to the south.
• The deposition of younger sedimentary rocks is controlled
by the subduction of Arabian Oceanic Plate under the
Makran Continental Plate.
• The stratigraphy of this basin is complex and shows a great
deal of variation from one end to the other.