geol- of pak-pre camb-cambrian. lect.vi 1-6

GEOLOGY OF PAKISTANLECTURE # VI 1/6

RAFIQ AHMED LASHARI

Precambrian – Cambrian of Pakistan

1

Geology of

Pakistan

2

Geology of Pakistan3

PrecambrianThe Stratigraphic sequence in Pakistan ranges from Precambrian to Recent. Precambrain metasediments cover the Archean gnesisic complex of Indian Craton and form the upper part of the basement complex.

1. Lower Indus BasinNagar Parker Igneous Complex

2. Upper Indus Basin Kirana ComplexHachi groupKirana groupSharaban group

3. Kohat – Potwar ProvinceSalt Range Formation


4. Axial Belt Attock – Cherat Range

5. HimalayanTectonostratigraphic Basin Salkhala FormationTanawal FormationSharda groupAlpurai groupBesham groupKarora groupKhaghan group


1. Lower Indus BasinNagar Parker Complex

Jan et al. (1997) named and described a sequence of acid and basic igneous rocks exposed near Nagar Parker in Sindh as “Nagar Parkar igneous complex”.

Butt et al (1994) called it as “Late Proterozoic rocks of Nagar Parkar”.



Butt et al (1994) mapped and described the rock sequence as follows. “The oldest rocks are metamorphosed basic igneous rocks. Acidic dykes have intruded these metabasites, which have the level of epidote amphibolites metamorphism.

Acid dykess range from rhyolite to quartz trachyte in composition.

Metabasites are intruded by grey granite, which contain the xenoliths of the former rock type. Pink granite intrudes the grey granite, and also carries xenoliths of mafic rocks, finally all the major rocks including both the granites are intruded by mafic dykes".


Jan et al. (1997) made detailed and critical petrographic studies and produced a geological map of the area. According to them six major magmatic episodes of intrusive and extrusive activities have been identified:

(1)Amphibolites and related dykes:

The amphibolites, apparently forming host rock for the subsequent intrusions, show low-grade metamorphism. Geophysical survey carried out by Farah and Jaffrey (1966) in the area indicates that they cover large subsurface area and evidently form the basement for the later rocks; they are metamorphosed up to amphibolite grade.


(2) Riebeckite-aegirine grey granite:

The riebeckite-aegirine grey granite is essentially composed of perthitic feldspar and quartz, with a small amount of plagioclase and presence of sodic minerals including characteristic riebeckite and aegirine. The best exposures of the grey granite are at Karunjhar Hill. It is mostly undeformed; also contain iron oxide, zircon and many other accessory minerals.

Jan et al. (1997) correlated this unit with Warsak and Sheva-Shahbaz Garhi granite in the northern Pakistan.


(3) Biotite-hornblende pink granite:

The biotite-hornblende pink granite is mostly medium to coarse-grained. Jan et al. (1997) termed it as "generally leucocratic and commonly homogeneous". It is generally made up of "light minerals" like perthitic feldspar, local micro cline, quartz, and minor plagioclase (oligoclase), with some biotite, hornblende and iron oxide. Some rocks contain sufficient plagioclase to be termed quartz monzonite or adamellite.


(4) Acid dykes:

This unit includes porphyritic microgranite dykes, rhyolitic dykes and rhyolite porphyry and with leucogranitic and equigranitic aplite dykes. This unit ranges from aplite to microgranite to quartz trachyte. It contain phenocrysts of perthite, plagioclase and quartz in an allotriomorphic matrix of these minerals and it induces in it accessory minerals, like iron oxide, blue-green amphibole (riebeckite), biotite, zircon, apatite, fluorite, sphene, allanite and secondary epidote. These rocks generally occur as small bodies but locally (as in Dhedhvero), form up to 6 m thick dykes extending for more than 2 km.


(5) Rhyolite Plugs:

The rhyolites occur in two small, domel outcrops surrounded by alluvium. They are dark grey to black, glassy looking rocks with whitish bands and consist of phenocrysts of feldspar and quartz in a very fine-grained matrix.

The rocks are fine-grained and porphyritic to sub porphyritic, contain phenocrysts of K-feldspar, mainly perthite and quartz with small amount of plagioclase and accessory minerals like zircon' and apatite


(6) Basic dykes:

All the major rock units of the complex are intruded by undeformed basic dykes, mostly less than 3 m thick.

They show considerable petrographic variation and range from hornblende micro diorite to gabbro and dolerite, some of which contain titanian augite suggestive of alkaline affinity (Jan etal., 1997).

2. Upper Indus Basin

Kirana Complex

Hachi group

Kirana group

Sharaban group



Kirana Complex

Sedimentary and igneous rocks of Kirana hills of Late Proterozoic age are exposed in Punjab, covering the areas from Sargodha to Shahkot. Major exposures are located near the towns of Sargodha, Chiniot, Shahkot and Sangla hills. The complex is composed of metasedimentary, grey slates, red and grey quartzite, conglomerate, volcanic and metavolcanic. No plutonic rocks in the complex yet have been reported from anywhere. The complex contains some mineralized zones of hematite, copper, gold, silver and cobalt. Except hematite all other minerals are in minor quantities.


Hachi group

Hachi volcanic of Alam (1987) is described as Hachi Hill north of Sikhanwali Railway Station.

Ahmed et al. (2000) divided the Hachi volcanic into the following two units. A)Volcanic (dolerites, andesite, dacite, dacitic tuff, rhyolite and rhyolitic tuff:) Volcanogenic slates, often interbedded with rhyolite/rhyolitic tuff and dolerite.

B)More than 90 m. thick, grey, glassy lava and tuff is present with lava flows predominate.


Kirana groupThe Kirana group (mentioned before by Kazmi (1964) and Shah (1961 [unpublished] and 1973), into two units: namely 1. Taguwali formation2. Asianwala quartzites

1. Taguwali formation:The name has been assigned after a small place Taguwali. Lithology of this unit is phyllite/slate and fine-grained quartzites in the lower part. Phyllite is light silver-grey, fine-grained, thin-bedded, partly thick-bedded at places and shows cross bedding. In the upper part of the formation, phyllite is the dominant rock type with minor slate..


2. Asianwala quartzitesThis unit is named after the canal rest house Asianwala located at 11 km. on the Sargodha-Faisalabad Road.

Lithologically, the formation is predominantly quartzite with minor intercalations of slate.

The quartzite is generally coarse-grained; partly pebbly at places the quartzite is dirty white to light grey, mottled brown, thick-bedded. It is cross-bedded and ripple marked. At places, joints and fractures are filled with brown hematitic material. The interbedded slates are light grey in colour and occur as thin layers in-between the thick beds of quartzite.


Sharaban groupAccording to Alam (1987), "new Sharaban group has been proposed comprising of two units:

The upper unit is Sharaban conglomerate, which is characteristically calcareous in nature and

The lower unit is Hadda quartzite, which is also calcareous.

The rocks of these units are exposed only in isolated hills called Sharaban. These units are considered younger than the Kirana group based on regional trend/structure.


3. Kohat – Potwar ProvinceSalt Range Formation

Rock units ranging in age from Precambrian to Cambrian are exposed in the Kohat-Potwar Province of the Indus Basin, where the Salt Range Formation with salt marl, salt seams and dolomite forms the basement for the fossiliferous Cambrian sequence of the Salt Range.

The deposits of the Salt Range Formation represent an evaporite sequence similar to the Hormuz Salt Formation of lran (Shah and Quennell, 1980). Probably a large part of the Indus Basin is occupied by this formation. Although, its exposures are restricted to the Salt Range, deep drill holes have confirmed its presence to the north and south of the exposures.


Salt Range Formation

Wynne (1878) named and described the formation as 'Saline Series'. Gee (1945) called the same unit as the 'Punjab Saline Series'.

Asrarullah (1967) has given the present name 'Salt Range Formation' after the Salt Range.

Khewra Gorge in the eastern Salt Range has been designated as the type section.

Kewara Sandstone22


The lower part of the Salt Range Formation is composed of red coloured gypsferous marl with thick seams of salt, beds of gypsum, dolomite, greenish clay and low-grade oil shale are the constituents of the upper part.

A highly weathered igneous body known as "Khewra Trap" has been reported from the upper part of the formation.

The "Khewra Trap", also known as "Khewrite" by Mosebach (1956), is six (06) meters thick and is purple to green in colour.

It consists of highly decomposed radiating needles of a light-coloured mineral, probably pyroxene.


The red colored marl consists chiefly of clay, gypsum and dolomite with occasional grains and crystals of quartz of variable sizes. Thick-bedded salt shows various shades of pink color and well-developed laminations and color bandings up to a meter thick.

Minor amounts of potassium and magnesium sulphates are found in association with the shale beds.

The gypsum is white to light grey in color. It is about 5 m thick, massive and is associated with bluish grey, clayey gypsum and earthy, friable gypseferous clay. The dolomite is usually light color, it is flaggy and cherty. It is associated with dolomitic shale, bituminous shale and low-grade oil shale


4. Axial Belt Attock – Cherat Range

Hussain et al. (1989) divided the Attock-Cherat Range into northern, central and southern blocks bounded by thrust faults, for the convenience of the description of stratigraphy. They described the Precambrian rocks from the Attock-Cherat Range as following.

1.Manki Formation 2.Shahkot Formation3.Uch Khattak Formation4.Shekhai Formation5.Dakhner Formation6.Hazara Formation


5. HimalayanTectonostratigraphic Basin

Originally, in this area only Salkhala, Tanawal and little igneous rock were described about three decades ago. This situation was due to inaccessibility and lack of mapping in this area and only roadside reconnaissance work was available. Detailed research work began in late seventies and subsequently, a large number of formations have now been described. This basin is delineated by Panjal Thrust in the south and Main Mantle Thrust (MMT) in the north, and includes Lesser and Higher Himalayas with the Main Central Thrust (MCT) in between them. This basin comprises of :


5. HimalayanTectonostratigraphic Basin

1. Salkhala Formation2. Tanawal Formation3. Sharda group4. Alpurai group5. Besham group6. Karora group7. Khaghan group


CambrianUpper Indus Basin (Kohat-Potwar Province)

5. Khisor Formation 4. BaghanwalaFormation 3. JutanaFormation 2. KussakFormation 1. Khewra Sandstone


AxialBelt

Attock-Cherat Range

Darwaza formation

Hazara Area

Hazira Formation ( Cambrian) Abbottabad Formation (Cambrian) Tanawal Formation (Precambrian to Cambrian)


Himalayan Tectonostratigraphic Basin

Peshawar - Swabi area Ambar formationBampokha groupGirarai formationTursak formation


Hindukush – Karakoram Tectonostratigraphic Basin

Northern Sedimentary Province

Chikar quartziteAghost formation


CambrianThe Cambrian System of Pakistan has been best studied in the Salt and Khisor ranges, where the sequence is well developed.

Although in northern areas, some rocks have been assigned Cambrian age.

However, in Lesser Himalaya, a division of Himalayan Tectonostratigraphic Basin, the presence of the Cambrian rocks in the Kashmir and Hazara areas has been undoubtedly recognized.


Lithology The Salt Range, is composed of sandstone, shale and dolomite beds with Early to Middle Cambrian fauna.

The Cambrian of Kashmir is mainly composed of foliated clay, slate, greywacke and limestone containing Late to Middle Cambrian fauna.

The sediments of the Hazara area have some lithological similarity with Salt Range, especially on evaporative style of deposition but scanty Cambrian fauna which is found in the Hazara area has not yet been reported either from the Salt Range or from Kashmir.


Upper Indus Basin (Kohat-Potwar Province)

1. Khewra Sandstone The name "Khewra group" was originally proposed by Noetling (1894). Prior to that, Wynne (1878) called the formation "Purple sandstone series". The latter name continued until recently, when the name of the formation was formalized as "Khewra Sandstone" by the Stratigraphic Committee of Pakistan, Fatmi (1973).

The type locality is in Khewra Gorge near Khewra Town, Salt Range.

Mosque in Khewra Salt Mine35


1. Khewra Sandstone

The formation consists predominantly of purple to brown, yellowish-brown, fine-grained sandstone. The lower most part of the formation is red, flaggy shale. The sandstone is mostly thick bedded to massive. Sedimentary features like ripple marks; mud cracks etc. are common in the formation. The contact of the Khewra Sandstone with the underlying Salt Range Formation has long been the subject of controversy, which arose because of age dispute of the Salt Range Formation.


Thickness at the type locality is about 150 m. In the western Salt Range, it is 200 m and the exposed thickness in the Khisor Range is about 60 m.

The formation contains only a few trace fossils in the Salt Range, which have been interpreted as trilobite trails by Schindewolf and Seilacher (1955) and are not indicative of any particular age.

the Khewra Sandstone is almost certainly Early Cambrian.



2. KussakFormation

Wynne (1878) applied the name 'Obolus beds' or 'Siphonotrata beds' to a predominantly greenish-grey, glauconitic, micaceous sandstone and siltstone. Waagen and Wynne (1895) used the name "Neobolus beds" for the same unit. Noetling (1894) proposed the name "Kussak group" and finally the Stratigraphic Committee of Pakistan formalized the name of the unit as Kussak Formation (Fatmi, 1973). The type locality lies near Kussak Fort in the eastern part of the Salt Range.


At the type locality, the formation is composed of greenish-grey, glauconitie micaceous sandstone, greenish-grey siltstone, interbedded with light grey dolomite and some oolitic, arenaceous dolomite. Numerous layers of intraformational conglomerate are also present. Pink gypsum lenses are present near the top. Thickness at the type locality is 70 m. but varies from 6 to 53 m. at other places. In the Khisor Range the formation is 55 m. thick.


The formation is fossiliferous and has yielded the following fauna:

Neobolus warthi, Botsfordia granulata, Lingulella wanniecki, L. fuchsi, Hyolithes wynnei, Redlichia noetlingi.

Schindewolf and Seilaeher (1955) regarded the age as Early Cambrian. However, the age of the formation is, therefore, either late early or early Middle Cambrian.



3. JutanaFormation

Fleming (1853) named this unit "Magnesian sandstone".

Noetling (1894) described it as Jutana stage.

The Stratigraphic Committee of Pakistan formalized the name as JutanaFormation.

The type locality lies near Jutana Village in the eastern Salt Range


At the type locality, the lower part of the formation consists of light green, hard, massive partly sandy dolomite, while the upper part is composed of light green to dirty white massive dolomite.

In the upper part, brecciated dolomite is also present with matrix and fragments of the same rock. The formation is fossiliferous including Lingulella fuchsi, Botsfordia granulata, Redlichia noetlingi and also a gastropod identified as Pseudo theca cf. subrugosa.

The age of the formation is described as late Early Cambrian to Early Middle Cambrian.



4. Baghanwala Formation

The name Baghanwala Formation is now given to the rocks of the "Pseudomorph Salt Crystal Zone" of Wynne (1878) and the "Baghanwala Group" of Noetling (1894), which overlies the Jutana Formation. Holland (1926) called these beds "Salt Pseudomorph beds" and Pascoe (1959) named them "Baghanwala Stage".

The type section is located near Baghanwala Village in the eastern Salt Range.

Pseudomorph Salt Crystal of BaghanwalaFormation

44


The formation is composed of red shale and clay with alternate beds of flaggy sandstone. The flaggy sandstone exhibits several colours including pink grey or blue green, especially in the lower half of the formation. Sedimentary structures such as ripple marks and mud cracks are common. Numerous pseudomorphic casts of salt crystals, which are found along the bedding planes, are the diagnostic feature of this formation. Presence of casts of salt pseudomorphs coupled with the absence of fossils indicates lagoonal environment and arid climatic conditions for the deposition of the formation.

It is considered as Early Middle Cambrian in age.



5. Khisor Formation Gee (1945) described a unit of rocks composed of gypsiferous dolomitic shale and dolomite lying between the Jutana Formation and the Tobra Formation in the Khisor Range as "Gypsiferous Series".

Hussain (1960) undertook a detailed study of the unit and named it "Khisor gypsiferous beds".

The Stratigraphic Committee of Pakistan approved the name Khisor Formation.


The Khisor Formation is limited only to the Khisor Range, where it is exposed only at one place near Saiyiduwali. This formation is not present in the Salt Range. However, its stratigraphic equivalent, the Baghanwala Formation, is fully developed in the Eastern Salt Range. At the type locality Hussain (1960) divided the rock unit into two parts. The lower part consists of massive white gypsum, with few thin beds of fine, grey, crystalline dolomite. The upper part is composed of light coloured, bedded shale, with finely crystalline dolomite and white gypsum. The shale is light grey in colour and is thin- to medium-bedded. The dolomite is medium to thick -bedded and the gypsum is massive.


The formation is devoid of mega-fossils.

However, the rocks have not been examined for micro fauna.

Since the formation occupies the same stratigraphic position as

the Baghanwala Formation of the Salt Range, it is assumed that it

represents Early Middle Cambrian age.


AxialBelt

Attock-Cherat Range

Darwaza formation

HazaraArea

Hazira Formation ( Cambrian) Abbottabad Formation (Cambrian) Tanawal Formation (Precambrian to Cambrian)


Himalayan Tectonostratigraphic Basin

Peshawar -Swabi area Ambar formationBampokha groupGirarai formationTursak formation


Hindukush – Karakoram Tectonostratigraphic Basin

Northern Sedimentary Province

Chikar quartziteAghost formation


Allah Hafiz

geol- of pak-pre camb-cambrian. lect.vi 1-6

Documents

pakistan ranges

northern pakistan

geology of pakistanlecture

major rocks

basic igneous rocks

oldest rocks

later rocks

xenoliths of mafic rocks