GEOLOGY OF NAMMAL GORGE, THE SALT RANGE, PAKISTAN

BY

MUHAMMAD HAMMAD MALIK

INSTITUTE OF GEOLOGY, UNIVERSITY OF THE PUNJAB

LAHORE

Abstract: Area north of Punjab plains is occupied by a major Thrust known as Himalayan Frontal

Thrust (HFT) along which lies Salt Range which occurs on the northern slopes of the Indian Shield.

Nammal Gorge is located on the western part of Salt range. In Nammal gorge the strata from late

Permian Wargal Limestone to Eocene Murree Formation are exposed. The area is structurally

characterized by features like cross bedding, ripple marks; plumose structures, flute casts, burrows and

some joints and fractures are present.

INTRODUCTION

On 28th October, 2008 a field

excursion program was organized by

Institute of Geology, University of the

Punjab, Lahore to Nammal Gorge present in

the western part of the Salt range.

The Nammal Gorge is located in the

western Salt range situated south of

Islamabad at a distance of about 200km.

from Lahore it is present northward at a

distance of 300km. the exact coordinates for

Nammal gorge are 3239’54” North and

7148’07” East.

The area is easily accessible as it is

located on the Grand Trunk Road from

Peshawar to Karachi. It took about 5 hours

to reach Nammal from Lahore and

approximately same from Islamabad. The

path in the gorge is rocky, bushy, and

unsteady and is along the water channel

that comes from the spill of the Nammal

Dam.

Climate of the area is hot and dry

with very low precipitation; average rainfall

is about 70-80mm per annum. Maximum

rains fall in Monsoon months of July and

August. In winter months of December,

January and February there is minimum

rainfall which makes it best time to visit the

Nammal gorge.

In Nammal gorge we find mix

lithologies. The Late Permian Zaluch Group

is mainly limestone having abundant fossils

of brachiopods. The famous Permo-Triassic

Boundary (P-T Boundary) separates the

Chiddru Formation of Zaluch group from

Mianwali Formation of Triassic. Tredian

Formation is of sandstone while Kingriali

Formation largely consists of Dolomitized

limestone. The variegated Datta Formation

underlies the Shinawari Formation above

which Samana Suk Formation is present

which comprises of limestone. After the

unconformity Hangu Formation is present.

The sandstone of Hangu Formation

underlies the nodular limestone of Lockhart

Formation. Shales of Patala Formation are

present above which Nammal Formation

and Sakesar Limestone are present.

Economically Nammal gorge is very

important. Large quantities of limestone,

sandstone and silica sand are being

extracted from the gorge. The quarries of

limestone present here are fulfilling the

needs of cement factories as well as

construction purposes.

TECTONIC AND STRUCTURE:

The Salt range is the active frontal

thrust zone of the Himalayas in Pakistan.

About 1km offset of the basement normal

faults acted as a buttress that caused the

central Salt range-Potwar plateau thrust

sheets to ramp to the surface, exposing

Mesozoic and Paleozoic strata. The frontal

part of the thrust sheet was folded passively

as it overrode the sub-thrust surface on a

ductile layer of Eocambrain salt. Lack of

internal deformation of the rare part of the

thrust sheet is due to decoupling of

sediments from the basement along this salt

layer. Cross-section balancing demonstrate

at least 20 to 23 km of shortening across the

ramp. The rate of Himalayan convergence

that can be attributed to under-thrusting of

Indian basement beneath sediments in the

Pakistan foreland is therefore at least 9-

14mm/year about 20%-35% of the total

plate convergence rate.

The salt range is the surface

expression of the leading edge of the

decollement thrust that resulted from

sediment decoupling from the northward

drifting basement of Indian shield and

essentially a complex salt anticlinorium

with a series of salt anticlines. The youngest

Salt range thrust appears 1.6 to 3.2 million

years ago. This collision changes the

sedimentation style from shallow neritic

environment to fluvial system.

The evaporites sequence is an

effective zone of decoupling allowing

thrusting to extend more than 100km south

of MBT without involving basement. The

salt layer permitted the rapid propagation

of the basal detachment frontal ramp at the

southern termination of the basin.

Deformation produce horizontal shortening

by folding and faulting, diapiric

emplacement of evaporites and uplifting of

the Salt range. The Salt range is terminated

by the Jhelum strike-slip fault in the east

and its western boundary is marked by

Kalabagh strike-slip fault. The monocline

structure of the Salt range represents rocks

belonging from the Cambrian to recent in

age.

STRATIGRAPHY:

14. Sakesar Limestone

13. Nammal Formation

12. Patala Formation

11. Lockhart Limestone

10. Hangu Formation

9. Chichali Formation

8. Samana Suk Formation

7. Shinawari Formation

6. Datta Formation

5. Kingriali Formation

4. Tridian Formation

3. Mianwali Formation

2. Chiddru Formation

1. Wargal Limestone

Wargal Limestone:

The name “Wargal limestone” was

approved by the Stratigraphic Committee of

Pakistan proposed by Teichert (1966) to the

unit formerly known as “Middle Products

limestone” of Waagen (1879) and “Wargal

group of Noetling (1901). Its type section is

Wargal village in the central salt range.

Lithologicaly the formation is

composed of limestone and dolomite of

light grey to medium grey, brownish grey

and olive green colors. In Zaluch nala the

formations lithology is divided into 10 parts

which shows alternate beds of sandstone,

limestone and dolomite.

The formation is 183m thick in

Zaluch nala while in Marwat and Khisor

ranges it is about 174m.

The contact of Wargal limestone

with underlying Amb formation is

confirmable while upper contact with

Chiddru formation is transitional.

Chiddru Formation:

The name Chiddru formation was

introduced by Dunbar (1932) to the

“Chiddru beds of Waagen (1891) and

“Chiddru group” of Noetling (1901).

The formation at the base is

composed of shale unit of yellowish grey to

medium dark grey color with small

phosphatic nodules. Above shale beds of

calcareous sandstone with few sandy

limestones are present. The top most part is

a white sandstone bed which is medium to

fine grained with subordinate shale

partings and contains abundant fossils.

The formation has a transitional

contact with underlying Wargal formation

while its upper contact is marked by a

major unconformity the P-T boundary

above which is the Mianwali formation of

Triassic age.

Mianwali Formation:

Gee (in Pascoe, 1959) used the

name” Mianwali Series” which was later

modified by Kummel (1966) into “Mianwali

Formation”.

The formation represents a great

wedge of varied facies consisting of marl,

limestone, sandstone, siltstone and dolomite

which is thickest in the west and wedges

out towards the east. The formation was

divided into three members in the Salt

range and Trans Indus ranges by Waagen

which were also recognized by Kummel

(1966). These members are not recognized

in Kala Chitta area.

The formation is 121m thick in

Zaluch nala while in Tappan Wahan section

it ranges from 135m to 187m.

Lower contact of the formation is

marked by the P-T boundary wile its upper

contact with Tredian formation is sharp and

well defined.

Tredian Formation:

The name “Tridian formation” was

introduced by Gee (in Kummel, 1966) to

replace his earlier name “Kingriali

sandstones”. The Tredian formation is

generally non-marine unit that succeeds the

Mianwali formation.

The formation consists of two

members the lower “Landa member” and

the upper” Khatkiara member”. The Landa

member consists of sandstone and shale.

The sandstone is micaceous and varies in

color from pinkish, reddish grey to greenish

grey and is thin to medium bedded. The

Khatkiara member is massive, thick bedded

white sandstone with inclusions of some

dolomite in the upper part.

The formation is 1560m in Tappan

Wahan section of the Khisor range and 76m

in Zaluch sections of salt range.

The contact with underlying

Mianwali formation is sharp while with

overlying Kingriali formation is

gradational.

Kingriali Formation:

The name “Kingriali formation” was

given to the “Kingriali Dolomite” of Gee

(1945). The name originates from the

Kingriali Peak of the Khisor range.

The formation consists of thin to

thick bedded, massive, fine to coarse

textured, light grey to brown dolomite and

dolomitic limestone with interbeds of

greenish dolomitic shale and marl in the

upper part. The formation is widely

developed in the Salt range, Trans Indus

ranges, part of Kala Chitta, Kohat and

southern Hazara.

The upper contact with Datta

formation is disconfirmable and shows

development of Ferruginous dolomite and

uneven surface at the contact. The lower

contact with Tridian formation is

confirmable.

Datta Formation:

The name Datta formation was

introduced by Danilchick and Shah (1967)

for the “variegated stage” of Gee (1945).

The formation is mainly of

continental origin and consists of variegated

colored sandstone, shale, siltstone and

mudstone with irregularly distributed

calcareous dolomitic, carbonaceous,

ferruginous glass sand and fireclay

horizons. The fireclay is present mainly in

the lower part.

At type locality the formation is

212m thick but increases to 230m in Punnu

nala to the west and over 400m in Sheikh

Badin Hills. In Nammal gorge area the

thickness is 150m which reduces further as

we move towards east.

The formation overlies

unconfirmably on the Kingriali formation in

Salt range and Trans Indus ranges while in

Hazara it rests unconfirmably over the

Precambrian Hazara formation. The upper

contact with Shinawari formation is

gradational.

Shinawari Formation:

The term “Shinawari formation”

was introduced by Fatmi and Khan (1966)

to the “Lowest Samana Beds” of Davies

(1930), and “lower part of Kioto limestone”

of Cotter (1933) after the village of this

name in western part of Samana Range in

Kohat.

At the type locality the formation

consists of thin to well bedded limestone

with nodular marl, calcareous and non-

calcareous shale and quartzose, ferruginous

sandstone. The limestone is grey, brownish

grey, fine to coarse textured and contains

sandy, oolitic and ferruginous beds. The

shale is grey to dark grey, splintery,

calcareous and non-calcareous.

The formation has a transitional

contact with the underlying Datta formation

and overlying Samana Suk formation.

Samana Suk Formation:

Davies (1930) introduced name

“Samana Suk” for the Jurassic limestone in

Samana range formerly named as “kioto

Limestone” of Middle miss (1896) and

Cotter (1933) and “Daulatmar Limestone”

of Calkins and Matin (1968). The name

Samana Suk is derived from the peak of this

name in Samana Range.

In the type locality the formation

consists of grey, medium to thick bedded

limestone with subordinate marl and shale

intercalations. The limestone is oolitic and

in Hazara and Kala Chitta it includes some

dolomitic and ferruginous sandy, oolitic

beds but these are absent here in Nammal

area.

The formation is widely distributed

in western salt range, Kohat, Trans Indus

ranges, Hazara and Kala Chitta. At the type

locality thickness is 186m while in Bagnotar

section Hazara it is 366m.

The lower contact is transitional

with Shinawari formation while upper

contact with Chichali formation is

disconfirmable.

Chichali formation:

This formation was established by

Danilchick and Shah (1967) for rocks

previously described as the “Belemnite

beds” from the salt range and Trans Indus

ranges. The type section is Chichali pass in

Surgar range.

At the type locality the formation

consists of dark green, grey, weathering

rusty brown glauconitic sandstone with

dark grey sandy, silty glauconitic shale in

the lower part. In western salt range it has

three members. Lower member with

glauconitic shale with some phosphatic

nodules passing upward into dark green

glauconitic sandstone with abundant

Belemnites. The upper member is

glauconitic chamositic, generally

unfossiliferous sandstone.

In Chichali area the thickness is 55m

to 70m while in southern Hazara on Haro

River it is 33m.

The lower contact with the Samana

Suk formation is disconfirmable. The upper

contact with Lumshiwal formation appears

gradational.

Hangu formation:

The “Hangu Shale” and “Hangu

sandstone” of Davies (1930) from Kohat

area have been formalized by the

Stratigraphic Committee of Pakistan. A

section south of Fort Lockhart is designated

as its type section.

The Hangu formation consists of

sandstone with grey shale intercalations in

upper part. The sandstone is white, light

grey and reddish brown, weathers dark

rusty brown, fine to coarse grained and

medium to thick bedded. In Nammal area

the sandstone is dark colored and

variegated rarely, shale, carbonaceous shale

and some nodular argillaceous limestone.

The formation is 90m thick at the

type section, 50m at Hangu and about 35m

in Mandeha Banni in Hazara.

There is an unconformity and is

underlain by Chichali formation in Nammal

while is conformably overlain by Lockhart

Limestone.

Lockhart Limestone:

Davies (1930a) introduced the term

“Lockhart Limestone” for Paleocene

limestone unit in Kohat area formerly

known as ”Nummulitic Series” of Middle

miss (1896). A section near Fort Lockhart in

Samana range is designated as a type

section.

At type locality the limestone is

grey, medium to thick bedded, massive,

rubbly and brecciated at places and flaggy

at basal part. In salt range Nammal area the

limestone is grey to light grey, medium to

thick bedded, nodular with minor amounts

of grey marl and dark bluish grey

calcareous shale in he lower part.

The limestone is well developed and

60m thick at type locality. It is about 70m

thick in Nammal gorge and 242m in Hazara

area.

The formation conformably and

transitionally overlies and underlies the

Hangu formation and the Patala formation

respectively.

Patala Formation:

The term “Patala formation” was

formalized by the Stratigraphic Committee

of Pakistan for the Patala shale of Davies

and Pinfold (1937) and “Nummulitic

formation” of Waagen and Wynne (1872).

Patala nala in Salt range is its type section.

In salt range the formation consists

of shale and marl with subordinate

limestone and sandstone. The shale is dark

greenish grey, selenite bearing., in places

carbonaceous and calcareous acd also

contains marcasite nodules. The limestone

is white to grey and nodular and occurs as

interbeds. Subordinate interbeds of

yellowish brown sandstone are present in

the upper part. Coal seams of economic

importance are present locally.

Thickness of Patala formation at

type locality is 90m while at Khewra it is

27m thick.

Patala formation conformably

overlies the Lockhart limestone and is

conformably and transitionally overlain by

Nammal formation in Salt range.

Nammal Formation:

The term “Nammal formation” has

been formally accepted by the Stratigraphic

Committee of Pakistan for the “Nammal

limestone and shale” of Gee (1935) and

“Nammal Marl” of Danilchick and Shah

(1967). The section exposed in Nammal

gorge is its type section.

The formation comprises of shale,

marl and limestone. In salt range these

rocks occurs as alternations. The shale is

grey to olive green while the limestone is

light grey to bluish grey. The limestone Is

argillaceous in places. The marl is also light

grey to bluish grey. In Surgar range lower

part consists of marl and shale with minor

limestone. The upper part has dominantly

limestone.

The formation is 100m thick at

Nammal gorge and thins out westward to

60m at Khairabad. It is 30m thick in

Khewra-Choa Saiden Shah road section in

eastern Salt range.

The lower contact with Patala

formation and upper with Sakesar

limestone are transitional.

Sakesar Limestone:

The term Sakesar limestone was

introduced by Gee (in Fermor, 1935) for the

most prominent Eocene limestone in the salt

range and Trans indus ranges. Sakesar peak

in the Salt range has been designated as its

type locality.

The unit consists dominantly of

limestone with subordinate marl. The

limestone throughout its extent is cream

colored to light grey, nodular, usually

massive with considerable development of

chert in the upper part. The marl is cream

colored and forms a persistent horizon near

the top. Near Daud Khail in western salt

range the limestone grades into white to

grey massive gypsum.

The formation is widely distributed

in salt range where the thickness ranges

from 70m to 150m.

The lower contact with Nammal

formation is confirmable. In eastern salt

range upper contact with Chorgali

formation is confirmable while in central

and western part, Rawalpindi group

overlies it conformably.

Economic Importance:

The Nammal area in the western Salt

range is important for economic point of

view. It acts as a source for various

economically important minerals which are

used in different industries.

As we enter the gorge we see big

quarries where limestone is being extracted

from Wargal Limestone and Chiddru

formation. This limestone not only feeds the

cement and construction industries but also

has very important use as aggregate in

roads and highways. Silica sand from Datta

formation is widely used in glass and

ceramic industry.

The Eocene succession also has its

own significance as it fulfills all the basic

requirements of a complete Petroleum Play

system. Shale, marl and limestone may act

as source, reservoir and seal within the

formation. Shale and marl of Nammal

formation is used in cement industry but its

limestone is not good. So Sakesar limestone

is used for this purpose.

“REFERENCES”

Cotter.G.de P., 1933, The geology of the part of Attock District, west of Longitude 7245’ E: India

Geol. Surv., Mem.,v.55,pp.63.

Danilchik, W., 1961, The Iron formation of the Surgar and western Salt Range, Mianwali Distt,

West Pakistan: U.S Geol. Surv., Prof. Paper 424-D, pp.228-231.

Davies, 1930a, The fossil fauna of the Samana Range and some neighbouring areas: Part 6, The

Paleocene Foraminifera, An Introductory note: India Geol. Surv., Mem., Paleont. Indica, New

Series, v.15, 15p.

Davies, and Pinfold, E.S., 1937, The Eocene beds of the Punjab Salt range: India Geol. Surv.,

Mem., Paleont. Indica, New Series, v.24, no.1, 79p.

Gee, E.R., 1935, Recent observations on the Cambrian sequence of the Punjab Salt Range: India

Geol. Surv., Ress., v. 68, pt.1, pp.115-120.