Stratigraphy of Jhelum group (khewra formation, khussak formation, jutana formation, baghanwala formation), its lithology, fossils, thickness, environment of deposition etc.

1. Cambrian Jhelum Group
Syed Wasim Sajjad

2. CAMBRIAN
• The Cambrian System of Pakistan has been best studied in
the Salt and Khisor ranges, where the sequence is well developed.
• The Cambrian formations recognized in these regions are as
follows:
– 4. Bhaganwala formation (lagoonal)
– 3. Jutana formation (shallow marine)
– 2. Kussak formation (shallow marine)
– 1. khewra sandstone (marine and non-marine)

4. Khewra Sandstone:
• Nomenclature:
• The name “Khewra group" was originally proposed by Noetling (1894).
• Prior to that, Wynne (1878) called the formation “Purple sandstone
series”.
• The formation was formalized as “Khewra Sandstone” by the
Stratigraphic Committee of Pakistan, Fatmi (1973).
• Type locality:
• The type locality is in Khewra Gorge near Khewra Town, Salt Range.
• Lithology:
• The formation consists predominantly of fine-grained maroon
sandstone (90%) and maroon clays.
• The lowermost part of the formation is composed of shale.
• The maroon color of clay and shale indicate oxidizing environment.

6. Sedimentary features like ripple marks; mud cracks etc. are common in the formation.
Contacts:
Lower contact: conformable with Precambrian salt range formation
Upper contact: conformable with Kussak formation
Thickness and distribution:
The Khewra Sandstone is widely distributed throughout the Salt Range. Thickness at
the type locality is about 150m. In the western Salt Range, it is 200 m and the
exposed thickness in the Khisor Range is about 60 m.
Fossils:
Traces of trilobites
Age:
Early Cambrian.
Environment of depositions:
Deltaic (on the basis of sedimentary structure)
The sandstone appears to be a good reservoir for oil, gas and water and may be exploited for
its hydrocarbon potential in the subsurface.

7. Kussak Formation:
• Nomenclature:
• Wynne (1878) applied the name 'Obolus beds' or 'Siphonotrata beds'.
• Noetling (1894) proposed the name “Kussak group”
• 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.
• Lithology:
• At the type locality, the formation is composed of greenish-grey, glauconitic
sandstone, greenish-grey siltstone, carbonaceous shale.
• Numerous layers of intraformational conglomerate are also present.

8. Thickness and distribution:
The formation is widely distributed throughout the Salt Range with its best exposures
in the eastern part. 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.
Fossils:
The formation is fossiliferous and has yielded the following fauna: Neobolus warthi,
Botsfordia granulata, Hyolithes wynnci, Redlichia noetlingi.
Age:
The age of the formation is Middle Cambrian.
Contacts:
lower : confirmable with khewra s.stone
upper: confirmable with Jutana fm.
Environment of deposition:
Glauconite (green colour mineral) is a sedimentary mineral form in shelfful marine
environment.

9. Jutana Formation:
• Nomenclature:
• Firstly this formation was named as Jutana Dolomite due to the prominent lithology of
dolomite.
• Then Stratigraphic Committee of Pakistan formalized the name as Jutana Formation.
• Type locality:
• The type locality lies near Jutana Village in the eastern Salt Range.
• Lithology:
• At the type locality, the lower part of the formation consists of light green, hard,
massive 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.

10. Contacts:
Lower contact: conformable with Kussak Formation
Upper contact: conformably overlain by the Baghanwala Formation.
Thickness:
The formation is thickest in the eastern Salt Range, whereas at the type locality it is
80 m thick. It thins westward. Its exposures in the Khisor Range have a thickness of 50 m.
Fossils:
Traces of trilobites, crinoids, echinoids.
Age:
The age of the formation is described middle to late Cambrian
Environment of deposition:
Supratidal to intratidal marine environment.
Economics importance: source for magnesium
Reservoir rock for hydrocarbon accumulation.

11. Bhaganwala Formation
• Nomenclature:
• “Pseudomorph Salt Crystal Zone” of Wynne (1878)
• Holland (1926) called these beds “Salt Pseudomorph beds”
• Later on it is named as Bhagan wala formation
• Type locality :
• Bhaganwala village (Eastern Salt Range)
• Lithology:
• Mostly composed of clay with interbedded laminated reddish sand stone
and siltstone.
• The diagnostic feature of this formation is the presence of salt
Pseudomorph.
• Thickness:
• Near Bhaganwala, thickness ranges from 100 to 116 m.

13. Bhaganwala formation
• Fossils:
• Unfossiliferous
• Environment of deposition:
• Lagoonal environment
• Contacts:
• Lower contact: confirmable with Jutana formation
• Upper contact: un confirmable with Permian Tobra formation.

16. Khisor Formation:
• Nomenclature:
• Hussain (1960) named it “Khisor gypsiferous beds”.
• The Stratigraphic Committee of Pakistan approved the name
Khisor Formation.
• Type locality: The Khisor Formation is limited only to the
Khisor Range.
• This formation is not present in the Salt Range.
• Lithology:
• The formation is predominantly composed of Gypsum,
Anhydrites, brown dolomite, white crystalline dolomites
with intercalation of shale.
• Age:
• In khisor ranges, the khisor formation is age equilent of
Bhaganwala formation of salt rage.