Field Report on Khewra Gorge

MY FIRST GEOLOGICAL EXPEDITION A FIELD TRIP TO KHEWRA SALT MINE, KHEWRA GORGE & NEELA WAHN GORGE

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ABDUL WAHAB KHAN SEMESTER MSc. GEOPHYSICS 4TH MAY, 2015.

TABLE OF CONTENTS CONTENT

PAG E NO

i.

PREFACE

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ii.

AKNOWLEDGEMENT

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1. INTRODUCTION 1.1INRTODUCTION TO THE AREA 1.2INTRODUCTION TO THE STUDY

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2. LOCATION OF THE AREA 2.1GEOGRAPHICAL LOCATION 2.2TECTONIC LOCATION

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3. OBJECTIVE OF THE STUDY

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4. GEOLOGY OF THE AREA 4.1IDENTIFIED LITHOLOGY 4.1.1 STRATIGRAPHIC COLUMN 4.2IDENTIFIED STRUCTURES 4.3TASKS 4.3.1 IDENTIFIYING ROCKS 4.3.2 USE OF BRUNTON COMPASS 4.3.3 CALCULATING STRIKE AND DIP

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5. REFERENCES

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PREFACE

Today's students are tomorrow's decision-makers, whether their future careers are in politics, finance, technology, medicine, geology, or other sciences. It is their decisions that collectively will decide the fate of our planet-earth. My teachers in Dept. of Earth sciences ensure that their students have the opportunity to obtain a sound understanding of the Earth so that they are equipped to make informed, environmentally responsible decisions in their future careers. I had the opportunity to visit Pakistan's unique field museum of geology and paleontology and found it a wonderful experience. I convey the message that understanding the Earth is exciting, and that it enriches and heightens our sense of awareness of the world around us. Our field trip to Eastern Salt Range was to recognize and understand various lithologies and structures in the sedimentary strata ranging from the Pre-Cambrian to recent age of the geologic time scale. If, at the end of my report, you feel the urge to have a glance over again, then I will have definitely paid due regard to all that I have learned during my field trip.

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ACKNOWLEDGEMENT

We live in amazing times. In the past few decades we have learned an enormous amount about our Earth, and new information confronts us almost daily. We can scarcely watch the news or read a newspaper without learning of some new and exciting discovery related to Earth. This information had come at such a bewildering pace, that it was difficult to assimilate it all without the help of my teachers. I feel highly obliged to the Dept. of Earth Sciences for arranging this field trip which augmented a hands-on chapter to my all my learning so far. It has greatly improved my understanding of all the theoretical knowledge that I have gained. My teachers at the field encouraged and taught me on every step of the way. Their expertise and cheerfulness kept me motivated and ensured my keen interest in learning out there. Dr. Aamir Ali, Dr. Anwar Qadir and Mr. Jamil Siddique satisfied my curiosity and made it a pleasurable experience as they navigated us through all of the members, formations and groups of the Eastern Salt Range that we observed. I am greatly indebted to Dr. Mona Lisa for opening the door to various tactics of report-writing which made substantial improvements to this text.

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1. INTRODUCTION

1.1 INTRODUCTION TO THE AREA The Salt Range contains the most important geologic and paleontologic localities in Pakistan, and is one of the outstanding field areas in the entire world. Despite its easy accessibility, it has a wealth of geological and paleontological features. In fact, it represents an open book of geology where various richly fossiliferous stratified rocks are very well exposed due to lack of vegetation. These rocks also provide an excellent opportunity for appreciation of tectonics in the field. (Sameeni, 2009)

1.2 INTRODUCTION TO THE STUDY A three-day field trip was carried out i.e. 24 th April, 2015 to 26th April, 2015. Our target location was Khewra Gorge and the Salt Mine. The focus of the study was to acquaint ourselves with the knowledge of sedimentary rocks and structural features in the Eastern Salt Range.

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2. LOCATION OF THE AREA 2.1 GEOGRAPHICAL LOCATION The Salt Range is confined between 32⁰18’N to 33⁰06’N and 71⁰50’E to 73⁰45’E.

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Figure 1.Location Map of Khewra

2.2 TECTONIC LOCATION

Figure 2. Location of the study area with reference to regional tectonic framework

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3. OBJECTIVE OF THE STUDY       

Identifying and Differentiating Rocks Lithological Correlation Stratigraphic Relationship Observing Sedimentary Structures Marking Unconformity Understanding Environment of Deposition of Formations Measurement of Strike and Dip

4. GEOLOGY OF THE AREA 4.1 IDENTIFIED LITHOLOGY A.

Salt Range Formation:

Synonym: Wynne (1878) named and described the formation as ‘Saline Series’. Gee (1945) called the same unit as ‘Punjab Saline Series’. The present name, the Salt Range Formation has been given by Asrarullah (1967). Type Locality: Punjab, Khewra Gorge in the eastern Salt Range has been designated as its type locality. 9

Age: The age of Salt Range Formation is late Precambrian or early Cambrian. Lithology: The lower part of the Salt Range Formation is composed of red-coloured gypseous marl with thick seems of salt while the 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. It consists of highly decomposed radiating needles of a light-coloured mineral, probably pyroxene. The red-coloured marl consists chiefly of clay, gypsum and dolomite with occasional grains and crystals of quartz of variable size. Thick-bedded salt shows various shades of pink colour and well-developed laminations and colour bandings upto a metre thick. The gypsum is white to grey in colour. It is about 45m thick, massive and is associated with bluish grey, clayey gypsum. The dolomite is usually light grey in colour and flaggy. It has three members: 1. Sahwal Marl Member. 2. Bhandar Kas Gypsum Member. 3. Billianwala Salt Member. Contacts: Its upper contact is with Khewra Sandstone which is normal and conformable and lower contact with metamorphic rocks of Precambrian age.

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Figure 3. Gypsum beds of Salt Range Formation in Khewra Gorge.

B.

Khewra Sandstone Formation:

Synonym: The name was originally proposed by Noetling (1894) as ‘Khewra Group’. Prior to that Wynne (1878) called the formation “Purple Sandstone Series” and this name was continued until recently when the name of the formation was formalized as “Khewra Sandstone” by the Stratigraphic Committee of Pakistan. Type Locality: The type locality is in Khewra Gorge near Khewra Town, Salt Range. Age: The age of Khewra Sandstone is early Cambrian. Lithology: The formation consists predominantly of purple to brown and yellowish brown fine-grained sandstone. The lowermost part of the formation is red flaggy shale. The sandstone is mostly thick bedded to massive. The Khewra Sandstone is widely distributed throughout the Salt Range.

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Contacts: Upper contact is with Kussak Formation which is gradational and lower contact with Salt Range Formation.

Figure 4. Purple sandstone with honey comb weathering in Khewra Sandstone. C. Kussak Formation: Synonym: Wynne (1878) applied the name ‘Obulus beds’ or ‘Siphonotreta beds’ to a predominantly greenish grey, glauconitic, micaceous sandstone and siltstone. Waagen (1895) used the name ‘Neobolus beds’ for the same unit. Noetling (1894) proposed the name ‘Kussak Group’ and finally the Stratigraphic Committee of Pakistan named the Formation as “Kussak Formation”. Type Locality: The type locality lies near the Kussak Fort in the eastern part of the Salt Range. Age: The age of the formation is either late early or early middle Cambrian. Lithology: The formation is composed of greenish-grey, gluconitic, micaceous sandstone, greenish-grey siltstone, 12

interbedded with light grey dolomite and some oolitic, arenaceous dolomite. Numerous layers of intraformatinal conglomerate are present. Pink gypsum lenses are present near the top. The general lithology throughout the formation is uniform. However, thickness vary at different places. Contacts: Upper contact is with Jutana Formation which is conformable and lower contact with Khewra Sandstone which is gradational.

Figure 5. Shale and micaceous silt stone of Kussak Formation. D. Jutana Formation: Synonym: Fleming (1853) named this unit “Magnesian sandstone”. Noetling (1894) described it as ‘Jutana Stage’. The Stratigraphic Committee of Pakistan formalized the name as “Jutana Formation”. Type Locality: The type locality lies near Jutana Village in the eastern Salt Range. Age: It is early middle Cambrian or late early Cambrian. 13

Lithology: At the type locality the lower part of the formation consists of light green, hard massive, partly sandy dolomite and 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 consisting of same rock. Contact: The formation is conformably underlain by the Kussak Formation and conformably overlain by the Baghanwala Formation.

Figure 6. Massive dolomite of Jutana Formation.

E.Baghanwala Formation: Synonym: The name Baghanwala Formation is now given to the rocks of the ‘Pseudomorph Salt Crystal Zone’ of the Wynne (1878) and the ‘Baghanwala Group’ of Noetling (1894). Holland (1926) called these beds “Salt Pseudomorph be ds” and Pascoe (1959) named them “Baghanwala Stage”. Type Locality: It is near Baghanwala Village in the Eastern Salt Range. Age: Early middle Cambrian Lithology: The formation is composed of red shale and clay, alternating with flaggy sandstone. The flaggy sandstone 14

exhibits several colours including pink grey or blue green, especially in the lower half of the formation. Contact: The contact of the Baghanwala Formation with the overlying Tobra Formation is unconformable, whereas the lower contact with the Jutana Formation is conformable.

Figure 7. Flaggy sandstone beds and shales in Baghanwala Formation.

F. Tobra Formation: Synonym: It was previously known in the literature as “Talchir Boulder Bed” or “Talchir Stage” of Gee and “Salt Range Boulder Bed” of Teichert (1967). Type Locality: The type locality is located near Tobra Village in the eastern Salt Range. Age: Early Permian Lithology: The Tobra Formation depicts a very mixed lithology in which the following three facies are recognized 1. Tillitic facies exposed in the eastern Salt Range. This rock unit grades into marine sandstone containing Eurydesma and Conularia fauna 15

2. Freshwater facies with few or no boulders. It is an alternating facies of siltstone and shale containing spore flora. 3. A complex facies of diamictite, sandstone and boulder bed. In the eastern Salt Range the Tobra Formation exhibits true trillite; the rock unit is composed of boulders of granite with fragments of quartz, feldspar, magnetite, garnet, clay stone, siltstone, quartzite, bituminous shale and gneiss. The matrix of the conglomerate bed is generally clayey, sandy and at some places calcareous. Contact: Upper contact with Dandot Formation which is gradational lower contact with Cambrian rocks (Baghanwala Sandstone) which is disconformable.

Figure 8. Tilatic facies of Tobra Formation.

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4.1.1 STRATIGRAPHIC COLUMN AGE

GROUP

FORMATION

Early Permian

Nilawahan Group

Sardhai Formation Warchha Formation Dondot Formation Tobra Formation

MAJOR UNCONFORMITY Middle and Early Cambrian

Jehlum Group

Baghanwala Formation (Salt Pseudomorph Beds) Jutana Formation (Magnesium Sandstone) Kussak Formation (Glauconitic Sandstone) Khewra Sandstone (Purple Sandstone)

Pre Cambrian

Salt Range Formation (Saline Series)

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4.2 INDENTIFIED STRUCTURES A.

Ripple Marks:

Ripple cross-laminae forms when deposition takes place during migration of current or wave ripples. A series of crosslaminae are produced by superimposing migrating ripples. The ripples form lateral to one another, such that the crests of vertically succeeding laminae are out of phase and appear to be advancing upslope. This process results in crossbedded units that have the general appearance of waves in outcrop sections cut normal to the wave crests. In sections with other orientations, the laminae may appear horizontal or trough-shaped, depending upon the orientation and the shape of the ripples. Ripple cross-laminae will always have a steeper dip downstream, and will always be perpendicular to paleo flow meaning the orientation of the ripples will be in a direction that is ninety degrees to the direction that current if flowing. Scientists suggest current drag, or the slowing of current velocity, during deposition is believed to be responsible for ripple cross-laminae. In the field we identified ripple marks in Khewra Sandstone .

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Figure 9. Ripple Marks

B.

Cross Bedding:

In geology, the sedimentary structures known as cross-bedding refer to (near-) horizontal units that are internally composed of inclined layers. This is a case in geology in which the original depositional layering is tilted, and the tilting is not a result of post-depositional deformation. Cross-beds or "sets" are the groups of inclined layers, and the inclined layers are known as cross strata. Cross bedding forms during deposition on the inclined surfaces of bedforms such as ripples and dunes, and indicates that the depositional environment contained a flowing medium (typically water or wind). Examples of these bedforms are ripples, dunes, anti-dunes, sand waves, hummocks, bars, and delta slopes. In the field we observed cross bedding in Khewra Sandstone.

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Figure 10.Cross Bedding

C.Mud Cracks: Mud cracks (also known as desiccation cracks or mud cracks) are sedimentary structures formed as muddy sediment dries and contracts. Naturally forming mud cracks start as wet, muddy sediments desiccates, causing contraction. A strain is developed because the top layer tries to shrink while the material below stays the same size. When this strain becomes large enough, channel cracks form in the desiccated surface material, relieving the strain. Individual cracks spread and join up forming a polygonal, interconnected network. These cracks may later be filled with sediment and form casts on the base of the overlying bed.

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Figure 11. Mud Cracks

D.

Honey Comb Weathering:

Honeycomb weathering, also known as fretting, cavernous weathering, alveoli/alveolar weathering, stone lattice, stone lace is a type of salt weathering common on coastal and semi-arid granites, sandstones and limestone. Honeycomb weathering is not limited to natural settings and can be seen to develop on buildings where a rate of development can be established. This rate can be as fast as several centimeters in 100 years.

Cause For honeycomb weathering to occur, a source of salt is needed because the basic mechanism for this kind of weathering is salt heaving. Salt is deposited on the surface of the rock by saltwater spray or by wind. Moisture must be present to allow for the salt to settle on the rocks so that as the salt solution evaporates the salt begins to crystallize within the pore-spaces of the rock. Porous rock is also needed so that there are pore-spaces for the salt to crystallize within. These salt crystals pry apart the mineral grains, leaving them vulnerable to other forms of weathering. It takes prolonged periods for this weathering to become visible, as 21

the rock goes through cycles of wetting and drying. We observed the honey comb weathering in Khewra Sandstone.

Figure 12. Honey Comb Weathering

E. Convolute Bedding:

Convolute bedding forms when complex folding and crumpling of beds or laminations occur. This type of deformation is found in fine or silty sands, and is usually confined to one rock layer. Convolute laminations are found in flood plain, delta, point-bar, and intertidal-flat deposits. They generally range in size from 3 22

to 25 cm, but there have been larger formations recorded as several meters thick. We also observed it in Khewra sandstone.

Figure 13. Convolute Bedding

F. Pseudo morph Salt Crystals: In mineralogy, a pseudo morph is a mineral or mineral compound that appears in an atypical form (crystal system), resulting from a substitution process in which the appearance and dimensions remain constant, but the original mineral is 23

replaced by another. The name literally means "false form". We observed it in Baghanwala Formation.

Figure 14. Pseudo morph Salt Crystals

G.

Load Casts:

Load casts or Sole marks are sedimentary structures found on the bases of certain strata that indicate small-scale (usually on the order of centimeters) grooves or irregularities. This usually occurs at the interface of two differing lithologies and/or grain sizes. They are commonly preserved as casts of these indents on the bottom of the overlying bed (like flute casts). This is similar to casts and molds in fossil preservation. Occurring as they do only at the bottom of beds.

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Figure 15. Load Casts H. Hollow Structures:

Figure 16.These are Hollow structures which are found in Salt Range Formation. I. Chopboard Weathering: We observed chopboard weathering in Jutana Dolomite. 25

Figure 17. Chopboard Weathering J. STALACTITES

Figure 18. Stalactites

K.

Burrows: 26

Figure 20. Burrows

4.3TASKS 4.3.1 IDENTIFYING SEDIMENTARY ROCKS 27

We identified sedimentary rocks on the basis of their     

Colour Clast Size Hardness Texture Effervescence

4.3.2 USE OF BRUNTON COMPASS The Brunton® compass is used by more geologists for field mapping of geological objects than other brands. This preference, especially in North America, is because Brunton provides a precise sighting-clinometer and hand level capability, and can be used at both waist and eye levels; advantages that are absent in other brands such as Silva which lacks a leveling system for sighting bearings (Compton, 1985).

Figure 21. A Brunton Compass

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4.3.3 CALCULATING STRIKE AND DIP WITH BRUNTON COMPASS

A bed was assigned to each group to find out its strike and dip by employing Brunton Compass, I obtained the readings stated below  Strike  Dip

N 76⁰ E 11⁰ NW

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5. REFERENCES 1. Compton, R. R., 1985. Geology in the Field. John Wiley & Sons, New York, 398p. 2. SAMEENI S.J. (2009). - The Salt Range: Pakistan's unique field museum of geology and paleontology. - In: LIPPS J.H. & GRANIER B.R.C. (eds.), PaleoParks - The protection and conservation of fossil sites worldwide.- Carnets de Géologie / Notebooks on Geology, Brest, Book 2009/03, Chapter 6

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