field report of salt range
TRANSCRIPT
GEOLOGY
2 FIELD TRIP TO SALT RANGE
Table of ContentsTABLE OF FIGURES............................................................................................................................................................................2
ACKNOWLEDGEMENT......................................................................................................................................................................3
1. INTRODUCTION.........................................................................................................................................................................4
1.1 Objective.................................................................................................................................................................................4
1.2 Significance.............................................................................................................................................................................4
1.3 Methodology..........................................................................................................................................................................4
1.4 Accessibility............................................................................................................................................................................4
1.5 Relief.......................................................................................................................................................................................5
1.6 Vegetation..............................................................................................................................................................................5
1.7 Drainage..................................................................................................................................................................................5
1.8 Rainfall and Temperature.......................................................................................................................................................5
2. STRATIGRAPHIC DESCRIPTION AND PREVIOUS WORK..............................................................................................................7
2.1 Tectonics.................................................................................................................................................................................7
3. MAJOR FORMATIONS OBSERVED.........................................................................................................................................9
3.1 MURREE FORMATION.........................................................................................................................................................9
3.2 KAMLIAL FORMATION.........................................................................................................................................................9
3.3 SALT RANGE FORMATION.................................................................................................................................................10
3.4 KHEWRA SANDSTONE.......................................................................................................................................................11
3.5 KUSSAK FORMATION........................................................................................................................................................11
3.6 JUTANA FORMATION........................................................................................................................................................12
3.7 BAGHANWALA..................................................................................................................................................................13
3.8 TOBRA FORMATION..........................................................................................................................................................13
3.9 SAKESAR LIMESTONE........................................................................................................................................................14
4. FIELD OBSERVATIONS.............................................................................................................................................................15
4.1 DAY 1....................................................................................................................................................................................15
4.2 DAY 2.......................................................................................................................................................................................17
4.2.1 Station 1.................................................................................................................................................................................17
4.2.2 Station 2.................................................................................................................................................................................20
4.3 Day 3.........................................................................................................................................................................................23
4.3.1 Station 1.................................................................................................................................................................................23
2
3 FIELD TRIP TO SALT RANGE
4.3.2 Station 2.................................................................................................................................................................................24
4.4 Day 4.........................................................................................................................................................................................26
4.4.1 Station 1.................................................................................................................................................................................26
4.4.2 Station 2.................................................................................................................................................................................27
4.4.3 Station 3.................................................................................................................................................................................27
4.4.4 Station 4.................................................................................................................................................................................27
5. CONCLUSION..........................................................................................................................................................................29
TABLE OF FIGURES
FIGURE 1 : VIEW OF LUSH GREEN VEGETATION COVER IN SALT RANGE.........................................................................5FIGURE 2 TECTONIC MAP OF THE AREA OF STUDY..........................................................................................................8FIGURE 3: RESISTIVITY DEVICE....................................................................................................................................... 15FIGURE 4: FINELY LAMINATED BOULDER.......................................................................................................................18FIGURE 5: RIPPLE MARKS FIGURE 6: CRUZIANA ICHNOFACIES........................................19FIGURE 7: VERTICAL BIOTURBATION............................................................................................................................. 19FIGURE 8: CROSS LAMINATION......................................................................................................................................20FIGURE 9: PINK GRANITE(TOBRA FORMATION) FIGURE 10: TOBRA FORMATION(FLUVIO-GLACIAL SEDIMENTS).22FIGURE 11 FACETED CUT (OBVIOUS IN GRAVEL EMBEDDED IN BED)............................................................................22FIGURE 12: TUMBLE BLOCKS FIGURE 13: TUMBLE BLOCKS ALONG ROAD SIDE.............................23FIGURE 14: HIGHLY FAULTED AND FOLDED SEQUENCE.................................................................................................24FIGURE 15: KAMLIAL FORMATION (SPHEROIDAL WEATHERING FIGURE 16: CONTACT B/W MURREE AND
KAMLIAL................................................................................................................................................................. 24FIGURE 17: WEATHERED AND UNSORTED LITHOLOGIES FIGURE 18: CONTACTS B/W DIFFERENT FORMATIONS. .25FIGURE 19: KAS GYPSUM MEMBER FIGURE 20: GYPSUM SPECIMEN................................................25FIGURE 21: ALLUVIUM................................................................................................................................................... 26FIGURE 22: TEAR LAKE OF KATAS FORT FIGURE 23: BLUE-GRENISH WATER OF TEAR LAKE....................28
3
4 FIELD TRIP TO SALT RANGE
ACKNOWLEDGEMENTWe would like to thank Almighty Allah for giving us the sense and strength to be a part of this field trip which was organized by the Earth and Environmental Sciences Department of Bahria University.
We would like to thank Mr. Anwar Qadir and Mr. Hamad for accompanying us to the field and sharing their knowledge with us. Mr. Mohsin Munir, who despite having other commitments joined us in the field and last but not the least Dr. Zafar who made all this possible and arranged a trip that was recreational and knowledgeable at the same time.
4
5 FIELD TRIP TO SALT RANGE
1. INTRODUCTION
1.1 ObjectiveA field trip was arranged by Bahria University, Department of Earth and Environmental Sciences on 21 July, 2010. It was a four day field trip to eastern salt range which is approximately120-130 km from Islamabad. We left for trip on Friday 22 octuber, 2010 at 8:30 am and arrived back to Islamabad on Monday 25 Octuber, 2010 at 6:30 pm. The main objectives of the trip was to study the tectonics, regional geology and geomorphological features of the area.
1.2 Significance
The basic purpose of the field was to complete the degree requirement of three credit hours field work. This was our second field, first we did in the Abbotabad,Hazara region. In this field the main objectives were to get familier ourselves with the faults, folded areas, thrusted shields and complex lithologies due to deformation and to get some idea about the complex paleotectonic mechanisms and salt diapirs which acted in the area, making complex structures and lithologic contacts.
1.3 Methodology
We applied different methods in our field to recognize the lithlogy , dipping directions and our position etc. so these methods are given below:
i. Global Positioning System (GPS) was used for finding the geographical locations of different stations where we worked.
ii. Brunton Compass was used for measuring the dip and strike of the rocks.
iii. Geological Hammer was used for collecting samples and differentiating between fresh and weathered surface of rocks. It is also used a scale.
iv. Hand lens was used for study of fossils and grain sizes.
v. Measuring tape was used to measure different lithologic sections.
vi. Acid was used to easily recognize the lithologies like limestone , dolomites and Weathered surfaces.
1.4 Accessibility
The area is well accessible through a well carpeted road and the Motorway. The drive to the area is approximately 1:30-2:00 hours from Islamabad.
5
6 FIELD TRIP TO SALT RANGE
1.5 ReliefCentral salt range area has a moderate relief. Sakesar peak is the highest peak in the area. While eastern salt range has a high relief.
1.6 Vegetation
The area is vegetated and contains many types of crops for both the summer and also in the winter seasons. The vegetation of salt range comprises both legumes and non legumes. Legumes have the capacity to capture nitrogen from the soil atmosphere; this allows pastures and crops to maintain productivity without depletion of soil nitrogen and some times can grow under situations where soil nitrogen levels are very low and where growth of other plant would not be possible. Further more, when legume plants die, its organic matter is broken down; there is usually a net gain in organic nitrogen to the soil.
Figure 1 : View of lush green vegetation cover in salt range.
1.7 Drainage
The drainage is mostly dendritic to parallel and generally controlled by structure. These run along the conjugate
shear features that strike N300W to N600W and N400E to N500E.
1.8 Rainfall and TemperatureThe average yearly rainfall is 70-80mm for salt range. This area lies within limits of monsoons and receive maximum rainfall in July and August. In December, January and February there is little rainfall month of April, November and
6
7 FIELD TRIP TO SALT RANGE
October are almost show the dryer season of that area.
The climate of area is semi humid and sub tropical with hot to moderate summers and severe winters. Due to the higher altitude and presence of Sakesar peak to the west temperature is usually less in summers as compare to adjoining plain areas and rarely exceeds 440C. During winters temperature usually remains between 00C to 230C.
Weather data for salt range, Pakistan
Month Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Year
Average high °C (°F) 20 22 27 33 38 40 36 34 35 33 28 21 31
(68) (72) (81) (91) (100) (104) (97) (93) (95) (91) (82) (70) (87)
Average low °C (°F) 5 8 12 18 22 26 26 25 23 17 10 6 16
Precipitation in(mm)
(41) (46) (54) (64) (72) (79) (79) (77) (73) (63) (50) (43) (62)
34 50 60 36 32 52 237 221 78 12 10 30 71
In (inches) (1.3) (2) (2.4) (1.4) (1.3) (2) (9.3) (8.7) (3.1) (0.5) (0.4) (1.2) (32.2)
7
8 FIELD TRIP TO SALT RANGE
2. STRATIGRAPHIC DESCRIPTION AND PREVIOUS WORK
In the past, the Salt Range has attracted geologists from all over the world to study Cambrian Stratigraphy, the Permian-Triassic boundary, and Lower Tertiary foraminifera biostratigraphy. Of particular note is the pioneering work of E.R. GEE (1935, 1945), who dedicated almost his entire geological career to the study of the Salt Range. His initial work related to solving the controversy regarding the age of the "Saline Series", a burning topic of that time, and he made a great contribution by producing a geological map (more recently six sheets on a scale 1:50,000 have been published by the Geological Survey of Pakistan excluding the Trans-Indus Surghar Range). DAVIES and PINFOLD (1937) completed a comprehensive study of Lower Tertiary larger foraminifera of the Salt Range. WAAGEN (1882- 1885, 1895) worked on the brachiopods of the Permian of the Salt Range and FATIMI (1973) studied the ceratitids of the Triassic of the Salt Range and Trans-Indus Surghar Range. He also worked on Stratigraphic nomenclature on the Salt Range as did SHAH (1977).
KUMMEL and TEICHERT (1966, 1970) illustrated Permian brachiopods and described the detailed staratigraphy of the Permian rocks while GRANT (1966) described trilobites. HAQUE (1956) described the smaller foraminifera from the Tertiary formations of the western Nammal Gorge, Salt Range. AFZAL (1997) completed his doctoral thesis on the planktonic foraminifera of the Paleogene and established a planktonic biostratigraphy for the Patala Formation of the Salt Range and Surghar Range (AFZAL & von DANIELS, 1991; AFZAL & BUTT, 2000). SAMEENI (1997) completed his doctoral thesis on the Paleogene biostratigraphy of the Salt Range under UNESCO IGCP-286, headed by Prof. Lukas HOTTINGER of Basel University, Switzerland, and established an alveolinid biostratigraphy for the Eocene succession of the Salt Range (SAMEENI & BUTT, 1996, 2004; SAMEENI & HOTTINGER, 2003). ASHRAF and BHATTI
2.1 TectonicsThe Salt Range forms the southern border of the hydrocarbon-bearing Potowar Basin in northern Pakistan, along the northwestern margin of the Indo-Pakistani Plate. It derives its name from the occurrence of gigantic deposits of rock salt embedded in the Precambrian bright red marls of the Salt Range Formation (formerly known as the "Punjab Saline Series"). Strata in the Salt Range dip northwards into the Potowar Basin where non-marine Tertiary sediments, collectively known as the Siwaliks, are exposed with a wealth of vertebrate fossils.
The southern face of the Salt Range is an escarpment that rises abruptly from the Punjab Plains with a junction marked by the Frontal Thrust. Block faulting is the most characteristic tectonic style within the Salt Range. The Salt Range is essentially an East-West trending elongated narrow trough bounded on the east by the River Jhelum and on the west by the River Indus. Beyond the River Indus at Kalabagh, it takes a sharp turn to run almost in a North-South direction. The entire mountainous belt has, therefore, previously been differentiated into the Cis-Indus Salt Range and Trans-Indus Salt Range now known as The Salt Range and Trans-Indus Surghar Range, respectively.
8
9 FIELD TRIP TO SALT RANGE
The Salt Range is one of the most important geological regions in Pakistan. It is easily accessible and displays a wide variety of geological features and paleontological remains. It has, therefore, been rightly called a field museum of geology and paleontology. It represents an open book of geology with richly fossiliferous stratified rocks that include a Permian carbonate succession with brachiopods, Lower Triassic ammonite bearing beds (the Mianwali Formation, formerly known as "Ceratite Beds") and Lower Tertiary marine strata composed of age diagnostic foraminifera. All the strata are excellently exposed due to lack of vegetation. The quality of the exposure also provides excellent opportunities to appreciate tectonic features in the field. The Salt Range is, therefore, of international scientific and educational value, and is highly worthy of conservation and preservation.
Figure 2 Tectonic Map of the area of study
9
10 FIELD TRIP TO SALT RANGE
3. MAJOR FORMATIONS OBSERVED
3.1 MURREE FORMATION
The “Mar Group” of Wyne (1874) and “Murree series” of Pilgrim (1910) have been formally named as” Murree Formation” by Stratigraphic committee of Pakistan. The name is derived from murree hills in Rawalpindi district.
A section exposed to Dhok Maiki in the Attock district has been designated as type section. The formation is composed of monotonous sequence of dark red and purple clay and purple grey and greenish grey sandstone with subordinate intraformational conglomerates. The basal Strata of formation consist of light greenish grey sandstone and conglomerates with abundant derived larger foraminifers of Eocene age. The horizon has been designated as fatehjang member after the “Fatehjang zone” of Pilgrim (1918). In kohat area the formation has greater number of sandstone which is brown, greenish grey in places purple and is medium to coarse grained.
The Formation is widely developed in the Kohat-potwar province, also been recognized in Kashmir. It is up to 3030m thick in northern potwar but thins only to 9m at Banda Daud shah in western kohat. The formation ranges in thickness from 180 to 600m in northern salt range.
The main body of formation is poorly fossiliferous and only few plant remains, silicified wood, fish remains, frog and mammalian bones have been recorded. However, the fatehjang member has yielded identifiable mammals indicating Anthracotherium bugtienses, Brachyodus giganteus, Palaeochoerus pascoei, Hemimeryx sp., Teleoceras fatehjangesis etc. The fauna indicates and early Miocene age for Murree formation.
3.2 KAMLIAL FORMATION
The “Kamlial beds” of Pinfold (1918) have been formally established as “Kamlial formation” by Stratigraphic committee of Pakistan. The formation is equivalent to “Kamlial stage” of Pascoe (1963). A section southwest of Kamlial attock district has been recognized as type section.
The formation consist of purple grey and dark brick red sandstone which is medium to coarse grained and contains interbeds of hard purple shale and yellow and purple intraformational
10
11 FIELD TRIP TO SALT RANGE
conglomerate. It is distinguished by under lying Murree formation by its spheroidal weathering and heavy mineral content in which the tourmaline is dominant over epidote.
The formation is widely distributed in kohat and potwar areas and has also been recognized in the disputed territory of Jammu and Kashmir. It is 90m thick at Kamlial, 580m at Khaur, 650m at Soan gorge and 60m at Ling River near Rawalpindi. In the subsurface, it is about 100m at Balkasar, 150m at Pamal Domeili and 180m at Jhatla and varies between 120 and 300m in western potwar, as drilled in oil wells.
A number of fossils have been recorded in formation. Some of the important as recorded included Trilophodon cf. angustidens, Dinotherium indicum, Anthracotherium sp., Hemimeryx blanfordi, Listriodon cf. guptai, Conphyus cf. sindiensis. The fossils indicate Middle to late Miocene age of formation.
3.3 SALT RANGE FORMATION
Wynne (1878) named and describe the formation as “Saline Series”. Gee (1945) called the same unit as “Punjab saline series”. The name “salt range formation” was given by Asrarullah (1967). Khewra gorge in eastern salt range is designated as its type section.
Formation is divided into three members by Asrarullah.
3.3.1 Billianwala salt member Dull red marl beds with some salt seem and 10m thick gypsum bed on top. Bright red marl with irregular gypsum, dolomite beds and Khewra trap: (3-100m)
3.3.2 Bhander kas gypsum member 1. Massive gypsum with minor beds of dolomite and clay; (more than 80 m)
3.3.3 Sahwal marl member 2. Ferruginous red marl with thick seems of salt; (more than 650 m)
The thickness of the formation in the Khewra gorge is more than 830 m. The upper contact of the formation with Khewra sand stone is normal and conformable. The base of the formation is almost unknown and is only known from karampur well where the formation overlies metamorphic rocks.
The age of the formation has long been a controversial topic. The overlying Khewra
11
12 FIELD TRIP TO SALT RANGE
sandstone is of early Cambrian age, therefore the salt range formation is assigned an Early Cambrian to Late Precambrian age
3.4 KHEWRA SANDSTONE
Wynne (1878) uses the name “Purple sandstone series” and Noetling (1894) called “Khewra group” to the rocks of this formation. Now the name “Khewra sandstone” is formalized by stratigraphic Committee of Pakistan.
The type locality is near Khewra village in Khewra Gorge in eastern Salt Range. The formation consists predominantly of purple to brown, yellowish brown, fine grained sandstone. The lower most part of the formation contains red flaggy shale. Sedimentary features such as ripple marks and mud cracks are common in the formation. The thickness at the type locality is 150 meters and in western salt range its thickness is 200 meters. It is distributed throughout salt range. The contact of Khewra Sandstone with underlying Salt Range formation is controversial due to which problem of age aroused. Sahni (1947) regarded age of formation Tertiary and postulated a thrust at the contact between Salt Range formation and Khewra sandstone. Gee (1945) mapped the entire salt range and concluded that the contact between Khewra sandstone with underlying formation is sedimentary. The upper contact with Kussak formation is conformable.
Khewra Sandstone has been observed in Khewra Gorge during our field work. Sand grains of medium size have been observed at the type locality. Sedimentary features such as cross bedding are observed in Khewra gorge. The lower contacts with sahwal marl member of salt range formation have been observed gradational.
The formation contains only few trace fossils which has been interpreted as trilobite trails by Schindewolf and Seilacher (1955) and are not indicative of particular age. Sahni (1947) regarded age of the formation Tertiary but the age of Khewra sandstone is early Cambrian because overlying Kussak formation is not older than late early Cambrian.
3.5 KUSSAK FORMATION
Wynee (1878) applied the name “Obolus beds” or “Siphonotreta beds” to predominantly greenish grey, glauconitic, micaceous sandstone and siltstone. Waagen (1895) called the same beds “Neobolus beds”. Noetling (1894) proposed the name “Kussak group” and finally the Stratigraphic Committee of Pakistan formalized the name of unit “Kussak formation”. The type locality is near Kussak fort in eastern part of Salt Range.
12
13 FIELD TRIP TO SALT RANGE
At the type locality formation is composed of greenish grey, glauconitic, micaceous sandstone, greenish grey siltstone inter-bedded with light grey dolostone and some oolitic, arenaceous dolomite. Numerous layers of intraformational conglomerate are present. Pink gypsum lenses are present near the top. The formation contains 5 to 25 cm long thin lenses of fossil asphalt (gilstone) observed by present author. The thickness of Kussak formation is different at different places. The formation is widely distributed throughout the salt range, with the best exposures in eastern part. The thickness at type locality is 70 meters but varies from 6 to 53 meter at other places. The upper and lower contacts of the formation are conformable.
The formation contains following fauna: Neobolus warthi, Botsfordla granulate, Lingulella wanniecki, Lfuhsi, Hyolithes wynnei, Redlichta noetlingi. The age of the formation is therefore either late Early or early Middle Cambrian.
3.6 JUTANA FORMATION
Fleming (1853) named this unit “magnesium sandstone”. Noetling (1894) called it as “Jutana stage” The Stratigraphic committee of Pakistan formalized the name of this unit as “Jutana Formation”. The type locality is near Jutana village in eastern Salt Range. At the type locality the lower part of the formation consists of light green, hard, massive partly sandy dolomite and 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 the same rock.
The thickness at type locality is 80 meters. It is not present in western salt range. However in farther west, in Khisor range, the formation is conformably overlain by Khisor formation which is equivalent to Baghanwala Formation of the Eastern Salt Range. In eastern salt range the lower contact with Kussak formation and upper contact with Baghanwala formation are conformable. Jutana formation was observed along Chua Saidan shah road during our field work. It was creamish dolomite. Schindewolf and Seilacher (1964) collected some fossils including Botsfordia granulate, Redlichia noetlingi and also a gastropod identified as Pseudotheca cf. subrugosa.
The age of formation is described as late Early Cambrian to early Middle Cambrian
13
14 FIELD TRIP TO SALT RANGE
3.7 BAGHANWALA
The name Baghanwala Formation is now given to the rocks of the “Pseudomorph Salt Crystal zone” of Wynee (1878) and the “Baghanwala Group” of Noetling (1894) Holland (1926) called these beds salt “Pseudomorph beds” and Pascoe (1959) named them “Baghanwala Stage”. The type locality is near Baghanwala Village in the eastern Salt Range.
The formation is composed of red shale and clay, alternating with flaggy sandstone exhibits several colors including pink grey or blue green, especially in the lower half of the formation. Numerous pseudo morph casts of salt crystals which are found along he bedding planes are the diagnostic feature of the formation. The thickness at eastern salt range is 40 meters. The contact of the Baghanwala formation with overlying Tobra Formation is unconformable, whereas the lower contact with the Jutana Formation is conformable.
The section observed in salt range at Chua Sadden shah road. We observed salt pseudo morph at bedding planes, which is a distinguishable criterion of the formation.
The formation contains trace fossils. The age of formation is early middle Cambrian because of it is conformably overlain by Jutana formation which is of the same age.
3.8 TOBRA FORMATION
The name “Tobra formation” was previously known as “Talchir Boulder Bed” or “Talchir Stage” of Gee (1959) and “salt range boulder bed” of Teichert (1967).
The type locality is near Tobra village in eastern salt range. Tobra formation consists of three facies Tillitic facies, Freshwater facies and complex facies.
1. Tillitic facies are exposed in eastern salt range. The rock unit grades into marine sandstone which is containing Eurydesma and Conularia fauna.
2. Freshwater facies have few or no boulders. It is an alternating facies of siltstone and shale containing spore flora. This facies is characteristics of the Central salt range.
3. A complex facies of diamictite, sandstone and boulder bed which increases in thickness in western salt range and Khisor Range is also present.
The Tobra formation is true tillitic; the rock unit is composed of boulders of granite with fragments of Quartz, feldspar, magnetite, garnet, clay stone, siltstone, quartzite, bituminous shale, diabase and gneiss. Some boulders are polished and scratched. According
14
15 FIELD TRIP TO SALT RANGE
to Teichert (1967) ice sheet that formed tillitic deposits is not a part of extensive inland sheet but it was result of local glaciations. The ice sheet did not extend in the area now occupied by central and western salt range. In the central range the Tobra formation is mainly composed of freshwater facies comprising siltstone and shale. The thickness of formation at type locality is 20 meters, but different at different localities. The contact of Tobra Formation with underlying Baghanwala is unconformable while the upper contact with Dondot formation is gradational.
The section was observed along Chua Saidan Shah Road in eastern salt range. It was observed that Tobra formation composed of tillitic facies. Gravels, boulders, grits, of different sizes mixed in clay matrix.
The flora and fauna reported in central salt range containing Glossopteris, Gangamopteris and several species of fresh water bivalves and Ostracoda. The lower part of formation in Zuluch nala contains pollen and spores of which the following have been identified: Punctatisporities. The age of formation on the basis of Stratiopodocarpites and Protohaploxypinus is considered to be Early Permian.
3.9 SAKESAR LIMESTONE
The term “Sakesar Limestone” was introduced by Gee for the most prominent Eocene limestone unit in Salt range and Trans Indus ranges.
Type locality of formation is Sakesar Peak in Salt range. The unit consists dominantly of limestone with subordinate marl. The limestone throughout its extent is cream color to grey color, nodular, usually massive, with considerable development of chert in upper part. The marl is cream colored to light grey and forms a persistent horizon near the top.
The thickness of the formation is 70m to 150m in salt range. The lower contact with the Nammal Formation is conformable. In eastern salt range, the upper contact with Chorgali formation is conformable, whereas in central and western salt range, the Rawalpindi or Siwalik groups unconformably overlie the formation. Sakesar formation was observed in Eastern salt range along Choa Sadden Shah road during our field work. Creamish colored, massive nodular limestone with nodules of chert in upper part was observed.
It contains rich assemblage of Foraminiferas, mollusks and echinoids. The age of formation is regarded as Early Eocene on the basis of foraminifers reported.
15
16 FIELD TRIP TO SALT RANGE
4. FIELD OBSERVATIONS
4.1 DAY 1
On the first day we carried out resistivity survey near the place where we were staying. The basic assembly of resistivity equipment consists of a battery, two multimeters and 4 electrodes (2 current and 2 potential). The device we used is shown below.
Figure 3: Resistivity device
Resistivity is a physical property of materials related to how well current can pass through the material. Most materials are insulators so the resistivity is normally controlled by the water content of the subsurface material. Materials with high water content have a lower resistivity because the ions in the water allow current to flow more easily. This method basically divides the subsurface into different layers on the basis of resistivity.
Resistivity can be measured by passing a current into the ground and measuring the potential difference. Separate pairs of electrodes need to be used for both functions because of high contact resistances at the probes. There are several different geometrical arrangements of electrodes to pass the current into the ground and to measure the voltage. One of the most common arrays used is called the Schlumberger array and this configuration was used in our experiment. The Schlumberger array is more complex as compared to the Wenner array with the spacing between the current electrodes not equal to the spacing between the potential electrodes. The Schlumberger array is shown below. In general, the potential electrode spacing is negligible compared to the current electrode spacing for this type of array.
16
17 FIELD TRIP TO SALT RANGE
We took various readings and plotted a graph at the end which are as follows.
MN/2 m
AB/2 m
Voltage mV
Voltage mV
(Corrected)
Current mA
Resistivity m-ohm
1 5 8.3 8.1 41.7 7.627967774
1 10 20.3 20.1 41.1 76.81996635
2 10 20.1 19.9 48.1 32.49360385
2 15 17.8 17.6 26.1 119.1638593
2 20 17.7 17.5 73.4 74.9017322
2 25 17.5 17.3 55.4 153.2873221
5 25 7 6.8 9.8 136.2425385
5 30 21 20.8 27.1 217.0133375
AB is the distance between current electrodes and MN is the distance between the potential electrodes.
17
18 FIELD TRIP TO SALT RANGE
1 10 1001
10
100
1000
The experiment showed that rocks at shallow depths contained water. As we went deeper there was less water content present as indicated by high resistivity values.
4.2 DAY 2
4.2.1 Station 1
Latitude : 32° 42´ 35” N
Longitude : 73° 03´ 52” E
our first stop was on the type locality of Kussak formation where we obsereved different
structural, lithological and stratigraphical features. We examined the typical feature of kussak
formation which was glauconitic, bioturbated sandstone(at some places the sanstone was
calcareous sandstone). Glauconite indicates deep shelfal environment. We also examined
ripples marks which were symmetric in nature and also there were micro-fractures which might
have hydrocarbon accumulations.
18
19 FIELD TRIP TO SALT RANGE
At certain places we examined thin laminae. The thinness indicated that their process of
formation was very slow. Laminations are an indicator of low flow regimes.
Figure 4: Finely laminated boulder
We observed laminated pits in the ripple marks. This showed that at one time
the flow of water was fast but then it slowed down. The water was saturated
with mud and consequently the mud was deposited as thin laminations.
Ripples indicate the top of a bed. But in this case they were at the base indicating
overturning of the bed. We observed trilobite fossils that indicated Cruziana
ichnofacies.
19
20 FIELD TRIP TO SALT RANGE
Figure 5: Ripple marks Figure 6: Cruziana Ichnofacies.
We observed the surface of solution weathering. In sandstone there was no
vertical bioturbation (burrows) rather it was predominantly horizontal.
Figure 7: Vertical Bioturbation
20
21 FIELD TRIP TO SALT RANGE
We also observed salt psuedomorphs which are the characteristic features
Baghanawala formation.
Figure 8: Cross Lamination
4.2.2 Station 2
Latitude : 32° 42´ 37” N
Longitude : 73° 03´ 53” E
Our next stop was village Watli. At this stop we observed an unconformity between the eocene
and cambrian sequences. Another unconformity was noted between Kussak and Baghanwala
(Jutana was missing) of the Cambrian age. The strike and dip of the beds is
N 700 E and 120NW respectively.
21
22 FIELD TRIP TO SALT RANGE
We observed sedimentary structures such as ripple marks, cross bedding. Bedding was fine-
medium. We also measured the section at the lower part of Baghanwala formation which is
described below.
Thickness of Beds Lithology Description
3’5” Sandstone Reddish
Friable
1.2” Sandstone Dark grey in color
9” Calcareous-micaceous
sandstone
Medium bedded
Weathered surface
was red
Fresh surface was
grey
1’2” Sandstone Blood-red in color, thinly
bedded
9” Micaceous sandstone Thinly bedded
From the base we hiked towards the top which was Tobra formation. Its composition varied drastically within the outcrop. Different compositions observed included pink granites, sandstones, limestone, dolomite etc. Pink granite are in Nagar Parkar area which is in the south
22
23 FIELD TRIP TO SALT RANGE
of Pakistan. This indicates that in the past geological time the flow of water was from south to north.
Figure 9: Pink granite(Tobra formation) Figure 10: Tobra formation(Fluvio-glacial sediments)
Faceted cuts are the characteristic features of glacial deposits.
Figure 11 Faceted cut (Obvious in gravel embedded in bed)
We concluded at the top two phenomena played an important role in the formation of that specific area. One was tectonism and the other was salt diapirs.
23
24 FIELD TRIP TO SALT RANGE
4.3 Day 3
4.3.1 Station 1
On the 3rd day our first stop was Pir Makhdom Jahani.
Latitude : 32° 44´ 52” N
Longitude : 73° 01´ 27” E
The place where we stopped had mainly alluvial deposits where we observed pink granites with faceted cuts which was an indication that these fans originated from the Tobra formation. Other sediments were calcareous sandstones, siltstones, tumbled blocks etc.
Figure 12: Tumble Blocks Figure 13: Tumble blocks along road side
Then we proceeded towards the west of the area where we came across medium bedded, highly jointed dolomite. The composition indicated that it was remanant of the Jutana formation. Here we also observed small scale bioturbation. The beds were highly faulted and there was also an overturned fold.
24
25 FIELD TRIP TO SALT RANGE
Figure 14: Highly faulted and folded sequence
The strike and dip of these beds as observed was, N50E and 370NW respectively.
4.3.2 Station 2
Latitude : 32° 45´ 27” N
Longitude : 73° 01´ 13” E
From there we moved further west and came across some exposure of Murree and Kamlial formation. Kamlia formation had a gritty appearance and the composition was friable sandstone.
Figure 15: Kamlial formation (Spheroidal weathering Figure 16: Contact b/w murree and Kamlial
25
26 FIELD TRIP TO SALT RANGE
Then we hiked up the mountain through a very perilous passage where we came across mostly boulders, cobbles, gravel of Murree, Jutana, Kussuk, Khewra and gyspsiferous claystones of salt range formation.
Figure 17: weathered and unsorted lithologies Figure 18: Contacts b/w different formations
On our way up we observed a member of salt range formation which was recognized as Bandar Kas gypsum member.
Figure 19: Kas Gypsum Member Figure 20: Gypsum Specimen
26
27 FIELD TRIP TO SALT RANGE
At the top, we came across Khewra sandstone. Its typical characteristics include parting lineation. Pinchouts, lenses (indicators of deltaic environment) were also observed in the Khewra sandstone. Dip and strike of the bed was 200NE and N130W respectively. The GPS location at this point was noted as,
Latitude : 32° 45´ 44” N
Longitude : 73° 01´ 41” E
It was concluded that there was a major thrust fault lying in the region between miocene and cambrian age sequences. The main reason for faulting was salt diapirs.
4.4 Day 4
4.4.1 Station 1This study was done just behind the place where we were staying. Here the exposure comprised of alluvium. There was a lot of color variation even at small distances. We also examined certain channel cuts which are very important with respect to well logging and seiesmic. These were the incised valleys.
Figure 21: Alluvium
27
28 FIELD TRIP TO SALT RANGE
4.4.2 Station 2
Here we came across a mystery but our dedicated faculty had solved that problem. We saw red coloured bed which was overlain by alluvium. The red colored bed was later confirmed to be gypsiferous clays of salt range formation. This identification was done on the basis of hardness scale, effervescance property and well developed crystals in the bed. All these factors confirmed the presence of gypsum.
4.4.3 Station 3
We moved further up the exposure and came across certain lithologies which contained fossils namely nummulities, assilina etc. These fossils are the index fossils of middle Eocene age. Thus confirming the lithology as Sakesar limestone. In the vicinity there was also a lake, so the water found nearby had high salt content thus confirming the presence of salt range formation beneath the lake.
4.4.4 Station 4
Katas Fort
This was not a part of our study trip. We stopped there to look at the ancient place and were briefed about its interesting and unique history. It was built in 300 B.C. by Hindus and was the second temple built in the sub continen
Construction material used was calcareous tufa and the cementing material was lime, pulses and gypsum.
There was lake named ‘tear lake’ which was 250-300 feet deep. Its color was greenish blue. This fort was also used as a prison in the 1920s by the British.
28
29 FIELD TRIP TO SALT RANGE
Figure 22: Tear lake of Katas Fort Figure 23: Blue-grenish water of tear lake
Fig: Tear lake of Katas Fort Fig: Blue-grenish water of tear lake
Alberuni university was once located close to the fort. Alberuni measured the circumference of the Earth for the first time at a locality called Pind Dadan Khan, a few kilometers from the fort.
29
30 FIELD TRIP TO SALT RANGE
5. CONCLUSION
We seek a alot from the field trip, we learn many methods helpful in study the geology and geophysics of an area. We learn about resistivity method and techniques. We study many formation of eastern salt range and observed different lithologies, index features mark unconformities and contacts. We also gather a lot of samples of fossils and rocks from different formations. We learn and enjoy aot in this field and are very thankful to our teachers.
30