Geological Field Work in an around Maithon
Department of Geology, Asutosh College
B. Sc. HONOURS
|
4th SEMESTER
NAME: SOHEL RAHAMAN SARKAR
CU ROLL NO. : 193012-21-0473
CU REGISTRATION NO. : 012-1115-1835-19
COLLEGE ROLL NO. : 1131
Introduction
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Geologic Setting
Basic Methodology
Lithology
Primary Structures
Deformational Structures
Observation of OCP coal
mine (Ramnagore colliery)
Paleontological
observations
Conclusion
Introduction
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The geological field work was conducted at Maithon, Kalyaneshwari in West Burdwan , was arranged for the 1st Year Geology Honours students
of Asutosh College as a part of University syllabus. The measured latitude and longitude of the place is 23°46.919’ and 86°49.710’
respectively. It is situated at the border of West Bengal and Jharkhand towards North East side of G.T. Road, which is at the left side of river
Barakar. The area falls under the Survey of India Toposheet no- 73/I/13.
Purpose of the Field Work:
1. To learn the fundamental methods like measurement of attitude of beds and foliation of rocks ,map orientation ,plotting locations on map etc
which are essential for geological field work.
2. To study the different exposures of sedimentary rocks with fossil bearing units, igneous and metamorphic rocks.
3. To study the litho units in terms of their location, hand specimens, petrography along with the measurement of structural data (attitude of linear
and planar structures, true bed thickness) and understanding the modes of occurrence of the different litho units and their inter relationships.
4. Also to learn about the use of the geological instruments (clinometer, chiesel, hammer etc)and to collect of samples for future references.
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Geographical details of the study area
Elevation: The regional areas of Maithon have an average height elevation of 50 meters
from MSL.
Soil type : The area is mostly covered by Intra-zonal type of soil. Mainly sandy clay loam
and gravelly sandy loam with very low organic carbon cover the area.
Topography: The overall topography is uneven and undulating, characterised by the
presence of the Barakar River and the Maithon reservoir. Metamorphic rocks are exposed
along the region along with some igneous intrusions as well.
Climate: The climate of Maithon during the time of field was mainly hot & sub-humid
tropical. In summer the average temperature is 22-25° C. and in winter temperature falls
to 14-17° C. Occasional rain can be expected.
Drainage Pattern: Due to the prolonged denudation to which this regio has been
subjected, there is not much correspondence between the structural features and the
directions of drainage in case of rivers other than the Damodar. The general slope of the
country is towards south and south-east, so that most of the tributaries of the Damodar
River flow in these directions. The main river of Maithon is Barakar flowing from to NE to
SW.
Geologic Setting
Geologically, Maithon and its surrounding area belong to the south eastern
Chotanagpur Gneissic Complex, northern part of the East Indian Shield Region.
Comprised mainly of metamorphosed basement rock, experimentally
Precambrian in age.
It consists mainly of Precambrian granite gneisses of different varieties, with
some sporadic intrusions of basic to ultramafic rocks. However, in this terrain
younger Gondowana rocks are also present in isolated linear belts, having
a regional east-west trend.
The Chota Nagpur Gneissic Complex terrain is bordered by Singhbhum tectonic belt
at the north and the Gangetic alluvium in the south-east. Due to exposure of
both older (Precambrian) and younger (Gondowana) rocks in this region, it was
possible for us to study both metamorphic and sedimentary rocks at the same
time, from their respective time periods.
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Stratigraphic Succession of visited area:
Our fieldwork has been carried out in and around Damodar Basin. As we
know, Damodar basin is mainly enriched with Lower Gondwana
sediments. Here is the Lower Gondwana succession of Damodar basin.
Lithological details of the encountered formations from the basin will
be discussed below.
Age
Lower Cretaceous
Formation
Rocks
Intrusive Bodies
Dikes
UNCONFORMITY
Barakar Formation
Coarse and fine
grained sandstone,
carbonaceous shale,
coal seam
Kaharbari Formation
Siltstone, coarse
grained sandstone,
khaki shale
Talchir formation
Tillite, greenish
sandstone, needle
shaped shale,
conglomerate
Lower Permian
Upper carboniferous to
lower Permian
UNCONFORMITY
Precambrian
Granitic & amphibolite
gneiss, granite,
amphibole, mica schist
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Formations:
During the fieldwork we mainly encountered Talchir and Barakar formation. Lithological description, age,
depositional environments of the encountered formations are as follows.
1. Talchir formation: The Talchir formation, named after the Talchir area of
Orissa, forms the basal most member of the lower gondwana sedimentary
sequence of Damodar Basin. The typical facies of Talchir is wholly continental.
The basal member is a boulder bed, which is up to 30 m thick but usually less than
half this thickness. The boulder beds are set in ill-sorted matrix, often containing
angular clastics and which are usually unstratified and greenish or khaki colour
when fresh. This is followed by greenish shale which on weathering breaks up
into needle like pieces/splinters and is referred to as splinter shale. The sequence
is usually coarsens upward through silty shale and sandstone. The sandstone may
be purple, brown and white in colour and is usually peebly and cross-bedded.
2. Barakar formation: The lower part of Barakar formation
consists of pebbly and gritty sandstone, overlain by coarse sandstone
then fine sandstone followed by fine sandstone intermixing with shale
preceded by siltstone, carbonaceous siltstone and coal. At the Nala section
behind Kalyaneshwari Temple, a massive Gondwana sandstone shale
sequence was present. In Barakar formation, the entire basin was become a
stagnant swamps where plant material grew. They are stagnant water coal
bearing deposit.
There are almost 22 coal seams present in Barakar formation. They occur as
blanket covering the basin.
Basic Methodology
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Use of different instruments:
•
Clinometer compass: The basic instrument used in this field is the clinometer compass. A
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Hammer & Chisel: Another important tool for us was the hammer. A hammer for
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Diagonal Scale: For measuring both the length (of small dimensions) and the angle
clinometer compass is basically a magnetic needle fitted into a circular metal case with a
graduated circular dial beneath it. The graduations are marked 0-360 in two concentric rows
from the periphery. Also attached to it by a pivot, is a flattened pendulum. This pendulum
points at a scale of 0-90 and along with the help of the straight handle, it helps to measure the
dip and plunge of planar and linear bodies. Hence, with the magnetic needle acting as the
compass and the pendulum, we can measure the strike and dip of structural features. The
needle has another function, i.e. to measure the bearing of objects from the user’s location.
This is done by carefully noting down the value to which the needle points after looking
through the vertical slit.
geological purpose must have a chisel opposite to the flat end. The chisel is helpful in breaking
rocks for taking samples.
between two linear elements, a diagonal scale is used. It is a simple 15cm scale with markings
of degrees like a protractor from 0°-90°.
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Pocket Lens: Last but not the least is the simple 10x pocket lens. It has
optical magnification of 10x and is indispensable while identifying the
mineral composition of a rock.
Measuring attitudes of planar and linear elements:

➢
The strike of a planar feature (bedding plane, foliation plane, joint plane
etc.) is measured with the help of a clinometer. The flattened handle of the
clinometer is placed on the plane and rotated such that the pendulum
points 0°. At this position the clinometer lies on a horizontal plane
intersecting the plane under observation. The direction towards which the
needle points now is the strike of the plane. The planar handle when placed
perpendicularly on the plane, the reading on the pendulum gives the dip of
the bed.
➢
To measure the plunge and the plunge direction of a lineation (mineral
lineation, slicken lines, hinge etc.) the clinometer handle is placed on the
linear element plunging with it. The reading on the pendulum in this
situation gives the measure of the plunge. To measure the plunge direction,
a paper is held such that it passes through the linear element. When the
vertical slits of the clinometer are aligned with this paper, the reading of the
needle (front bearing) gives the plunge direction of the linear element.
➢
A diagonal scale is used to measure the rake of a linear element on a planar
body just by measuring the angle between the strike line (drawn with the
help of a marker pen) and the linear element.
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Lithology
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Recognition of rock types:
All the three types of rocks (Igneous, Sedimentary and Metamorphic) are found in Maithon. The
recognition of these different types of rocks during field work was done basically by
distinguishing their mineral content, dominant texture and a lot of help from the teachers.
▪ Igneous rocks: In Maithon, the igneous rocks are mostly of mafic composition,
hence dark in colour (melanocratic). Dominant mineralogy is biotite, hornblende, and pyroxene
with plagioclase feldspar. Interlocking textures are common.
▪ Sedimentary rocks: They are easily recognized due to their clastic texture,
presence of framework, matrix and cement. The dominant mineralogy is rounded quartz and
feldspar grains within siliceous matrix.
▪ Metamorphic rocks: They are dominantly composed of biotite, amphibole,
quartz and feldspar. The mineralogy is not much distinctive from igneous rocks, but
their texture is very different from the latter. The mafic and felsic parts of the rocks are generally
compositionally segregated into thin or thick bands known as schistosity or gneissosity of the rocks.
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IGNEOUS ROCK TYPES AND THE FEATURES ASSOCIATED WITH IT:
In Maithon, the igneous rocks are mostly of mafic composition, hence dark in colour (melanocratic). Dominant
mineralogy is biotite, hornblende, and pyroxene with plagioclase feldspar. Interlocking textures are common.
DOLERITE:
PEGMATITE:
QUARTZ VEINS:
Dolerite is a mafic, holocrystalline, hypabyssal
equivalent to volcanic basalt or plutonic gabbros.
Dolerite dykes are typically shallow intrusive
body. They show discordant relation with
respect to country rock. On the bank of Ajay
River, Jitpur a dolerite dyke intruding through a
migmatite complex could be seen.
It is an intrusive igneous rock with
interlocking texture usually larger than
2.5cm in size. The above pegmatite was
seen in Jitpur.
A vein is a distinct sheet like body of
crystallised minerals within a rock. Veins
form when mineral constituents carried by
an aqueous solution within the rock mass are
deposited through precipitation. Quartz veins
have been observed in Jitpur. These veins are
composed of very coarse grain quartz along
with some mica.
Dolerite owing to the presence of magnetite has
strong magnetic property.Olivine, pyroxene,
quartz are also present.
It is mainly composed of quartz,
orthoclase feldspar, plagioclase feldspar
with some amount of mica.
They have been folded and deformed to a
large extent.
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METAMORPHIC ROCK TYPES AND FEATURES ASSOCIATED WITH IT:
They are dominantly composed of biotite, amphibole, quartz and feldspar. The mineralogy is
not much distinctive from igneous rocks, but their texture is very different from the latter. The mafic and felsic parts
of the rocks are generally compositionally segregated into thin or thick bands known as schistosity or gneissosity of
the rocks.
GRANITE GNEISS:
AMPHIBOLITE GNEISS:
AUGEN GNEISS:
To the North of Kalyaneshwari temple , on the way to
Maithon dam the following gneiss was seen. Granitic
gneiss is a type of high grade metamorphic rock which is
metamorphosed from pre-existing igneous rock granite
under high temperature and pressure.
From the Y-shaped road towards maithon
dam rocks of amphibolite nature is observed.
Amphibolites gneiss is a metamorphic rock
with amphibole present as a major mineral.
Augen are large, lenticular eye-shape
mineral grains or mineral aggregates
visible in some foliated metamorphic
rocks. Augen forms in rocks which
have undergone metamorphism in
shearing.
Mineralogy & Texture : The rocks show a
banded texture characterised by alternating lighter and
darker bands. Darker bands are formed by minerals like
pyroxene, amphibole and biotite, whereas lighter bands
are formed by minerals like quartz, feldspar. It is
medium to coarse grained rock, overall it is a light
colored rock.
Mineralogy & Texture: Composed of
amphibole as major amount and minor
amount of quartz, feldspar, biotite And
muscovite is also present. A special structure
called pinch and swell was observed near the
kalyaneshwari temple near the basement
rock.
The core of the augen consists of
hard minerals such as olivine
serpentine and garnet and it is
highly fractured. it also contains
quartz and feldspar.
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UNAKITE: Unakites have been observed from bank of Ajay River. It’s a metamorphic rock that forms when
granite (an igneous rock) is altered by hydrothermal activity. During metamorphism, plagioclase in the
granite is altered by epidote to produce a rock composed primarily of green epidote, pink orthoclase, and clear to
bluish-gray quartz.
Mineralogy: In jitpur area widespread distribution of unakite could be seen. It is an altered form of
granite composed of pink feldspar ,green epidote and colourless quartz. its colour varies
between various shades of green and pink.
Texture and Structure: It has an interlocking structure. The green epidote which is the dominant mineral
was the indicator of the rock type.
MIGMATITE(meta-igneous rock): To the North–west of hotel Diya ,on the sides of the road leading to
the Maithon dam high grade metamorphosed migmatites are found.Migmatite is a mixture of metamorphic and
igneous rock. Forms under extreme temperature and pressure condition during prograde metamorphism during
partial melting of pre-existing rocks.
Mineralogy: Quartz, feldspar as light coloured mineral and amphibole as dark coloured mineral.
Texture and structure: Due to the pressure applied on the both side of the pre-existing amphibolites
gneiss, certain parts of the rock melt partially and recrystallise in a haphazard manner.
Light and dark coloured patches are known as leucosome and melanosome respectively.
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SEDIMENTARY ROCK TYPES AND FEATURES ASSOCIATED WITH IT:
They are easily recognised due to their clastic texture, presence of
framework, matrix and cement. The dominant mineralogy is rounded quartz and feldspar grains
within siliceous matrix.
SANDSTONE: Sandstone is a clastic sedimentary rock composed mainly of sand-sized silicate
grains. On the way to Kalyaneshwari temple, an exposure of drifted sandstones is present. They
have parallel bedding planes and have cross bedding structures. The cement is whitish,
indicating quartzitic or calcitic composition.
CONGLOMERATE: Conglomerate is a clastic sedimentary rock that is composed of a substantial
fraction of rounded to subangular gravel-size clasts. e.g. - gravels, pebbles, cobbles and boulders
larger than 2mm in diameter. It is usually formed by the consolidation and lithification of gravel.
It was found near Ajay river which indicates glacial deposits.
DROPSTONE: Dropstones are a glacial feature that occur when a stone that is incorporated into an
iceberg or ice sheet falls out as it melts, the block settles through the water column and lands on
the sediment beneath. The sediment continues to deposit and covers the stone. Several
dropstones were observed areas around the Ajay River.
Primary Structures
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Any structure, that develops prior to or during deformation of rocks are called primary structures. These are non-tectonic, meaning they for
during sedimentary deposition or in case of metamorphic rock, during crystallization.
1. CROSS BEDDING: They are a set of parallel inclined bedding surfaces, bound
by two planar surfaces. The truncated top is the erosional surface and indicates the
stratigraphic top. The lower surface merges asymptotically. The drifted sandstones
on the exposure on the way to Kalyaneshwari temple had poorly developed cross
beddings.
2. SOLE MARKS : Sole marks are features that are preserved when a coarse
sand or silt layer deposits onto mud. Typically during deposition of the sand/silt
the flow of the water erodes pits and scars into the mud layer and then these
depressions are later in-filled with the more coarse material. It was observed in
Gondwana section.
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3. PLANAR LAMINA: They are a set of parallel surfaces found in
sandstones, siltstones and shales and represent a short period of nondeposition. In some places near Ajay river really good planar bedding was
obseved. The sandstones present behind the Kalyaneshwari temple showed
excellent planar lamina as well as planar cross stratification.
4. RIPPLE MARKS: Ripple marks come in two forms, symmetric or wave
formed ripples and asymmetric or current ripples. Wave-formed ripple result
from the to-and-fro motion of waves and have symmetric profiles. Current
ripple marks form in response to water or wind currents flowing in one
direction and have asymmetric profiles. Ripple marks were observed on the
bank of Barakar river.
5.FOLIATION PLANES (SCHISTOSITY): Foliation planes (schistosity) were
present in metamorphic rock like amphibolites on the north of the reservoir, with
high muscovite and biotite content. Planar orientation defined by these minerals,
are separated from each other by alternating layers of K-feldspar and quartz.
Deformational Structures
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These structures show deformation that occurred during or after deposition..
1. FOLDS: Folds are formed when maximum principal stress (σ1)act on a planar body parallel to
it and minimum principal stress (σ3) acts perpendicular to it. Such deformation has produced
spectacular folds in the quartzite bearing the magmatic intrusion. These folds are mostly
asymmetric in nature.
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2. S-C FABRIC: S-C fabric is a metamorphic fabric formed by the
intersection of shear surfaces within rocks affected by dynamic
metamorphism. These shear bands are called C (French cisaillement for
shear, which relates to the movement of scissors) and the foliation is
named S (for schistosity or schistosité). It has been observed at Hadlah
Forest.
3. PINCH AND SWELL STRUCTURES: When magmatic
intrusions are accompanied by layer parallel stretching, the
planar intrusion forms alternate swelling and pinching
structures.
4. MULLIONS: Mullions are linear fluted structures developed
within a rock or at lithologic interfaces. They are rod like structures
characterised in cross section by convex surfaces with interveining
cusps or by alternating convex and concave surfaces. Several mullions
have been observed around burning ghat area of Maithon.
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5.SIGMA & DELTA STRUCTURE : Upon shearing, zones of pressure shadows and zones of pressure concentration
develop around these clasts. As fluids and their solutes migrate from high pressure to low pressure zones, crystallisations
develop in pressure shadows. The asymmetry of pressure shadows around a clast with respect to the shear plane depends
on the sense of shear and as such can be use as kinematic criteria. So due to shearing depending on pressure zones Sigma
and delta structures develop with the shape of greek letter Sigma and Delta respectively. During the field work around
Hadlah forest some delta and sigma structures were observed indicating presence of local shearing.
6.LINEATION: Lineations were present in gneissic rocks found behind the Kalyaneshwari
temple. The lineation containing rock was granite gneiss. There was conspicuous banding of
melanosomes and leucosomes.
Observation of OCP coal mine
(Ramnagore Colliery)
GENERAL DESCRIPTION : Ramnagar (also spelt Ramnagore ) is a locality of Asansol
Municipal Corporation in Asansol of Paschim Bardhaman District in the Indian state of West
Bengal. It has come up with the Ramnagar colliery, once a captive mine of IISCOThis is a captive
coal mine, started from 1905 and mining plant was started from 1939. Though both
underground and opencast mining are active here, major production comes from the opencast
mines. The Ramnagar Colliery has 16 coal seams up to a depth of about 650 m. Among them 16
seams are mined. This colliery is now under the company SAIL (Steel Authority of India
Limited).
Coordinates : 23.74485°N 86.831375°E
Coal Mine : The Ramnagar coal mine is captive opencast mine,
operated by Stell Authority of India (SAIL), producing 0.37 million tonnes per annum.
Parent company : SAIL India
Status : Operating
Producing capacity : 0.37 MTPA
Total resource :
Coal type: Non-cooking
Mine type : Opencast
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1. COAL: It is an organic sedimentary rock that forms from the accumulation and preservation of plant
materials, usually in a swamp environment. Coal is a combustible rock. When a plant dies and falls into the
swamp, the standing water of the swamp protects it from decay. Swamp waters are usually deficient in
oxygen, which would react with the plant debris and cause it to decay. This lack of oxygen allows the plant
debris to persist.
2. COAL SEAM: A coal seam is a dark brown or black banded deposit of coal that is visible within layers
of rock. These seams are located underground and can be mined using either deep mining or strip-mining
techniques depending on their proximity to the surface. These seams undergo normal coal formation and
serve as a conventional coal resource. The reserves of coal are immense, and are the largest of all of the
fossil fuels.
3. TYPES OF COAL: There are mainly 4 types of coal on
basis of percentage of carbon. In Ramnagore colliery we
found the Bituminous type of coal
Types
Percentage of carbon
1. Peat
45-60
2. Lignite
60-70
3. Bituminous
70-85
4. Anthrasite
85-95
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4. ROCK TYPES: In Ramnagar Colliery we mainly observed medium to coarse grained carboniferous shale.
The rock layers are highly felsic. It is mainly composed of sedimentary rocks of Barakar formation.
5. PRIMARY SEDIMENTARY STRUCTURE:
▪
Flaser bedding : Flaser bedding is a type of ripple bedding in which
thin sticks of mud occur between sets of cross laminated or ripple
laminated sandy or silty sediment. Mud is concentrated mainly in the
ripple troughs but may also partly cover the crest Flaser bedding
suggests deposition under fluctuating hydraulic conditions. Periods of
current activity, when traction transport and deposition of rippled sand
take place, alternate with periods of quiescence, when mud is
deposited
6. MAGMATIC INTRUSION:
▪
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Lamprophyre Dyke : Dykes are intrusive igneous bodies found cutting across the layers of pre-existing sedimentary layers. In
the Ramnagore colliery we founda long Lamprophyre Dyke cutting across the country rocks.
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▪
Jhama coal: When the magmatic intrusion passes through the sedimentary layers the
surrounding coal gets burnt and transforms into Jhama coal. Unlike normal coal jhama
breaks into pieces. Jhama coal is different in colour than normal coal because volatile
substances escape from them during burning. Jhama coal is used in ferro alloys and brick
manufacturing units.
7. SULPHUR PRECIPITATE: Sparse sulphur precipitates were also observed.
8. BALL COAL:
A type of coal which has taken the shape of a ball. It generally
forms from the nodes of trees. It was observed in the colliery.
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Paleontological Observations
During our fieldwork we didn’t encounter too much fossils, overall the studied area is
unfossiliferous. Although there were some important Lower Gondwana plant fossils and
some Ichnofossils.
1. GANGAMOPTERIS SP. : Gangamopteris is one the important fossils of the
lower gondwana. We have been observed some Gangamopteris plant fossils from
the Ramnagore colliery during our fieldwork.
2. ICHNOFOSSILS : We also have observed some ichnofossils (crawling activity,
resting impression etc) during the fieldwork besides Kalyaneswari temple at the
Nalah section.
Conclusion
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The fieldwork of first year was aimed at providing a basic knowledge of a geological field. Starting from pin-pointing our location on
a topographic map, we trudged our way into hands on experience on what are the structural and petrological associations of a
region. In our field location (Maithon), all the three major types of rock are present. The sedimentary rocks are found along the
banks of Barakar River. They are of Gondowana age. These sedimentary rocks are mostly composed of sandstones and shales.
However, these are intruded by basic igneous bodies and have been metamorphosed to quartzites. Igneous intrusions are also
present on the road towards the reservoir. These intrusions are huge dikes which have metamorphosed the surrounding rocks to
migmatites.
Further towards north, along the Maithon dam and reservoir, we find metamorphic rocks like amphibolite gneisses. These are
medium grade metamorphic rocks and show metamorphic textures like schistosity and gneissosity. Dominant mineralogy of these
rocks includes hornblende and other amphiboles along with quartz, feldspar, and muscovite.
Thus, by observing the continuous and systematic variation of mineralogy and textures of rock from south to north, we can conclude
that the region has developed under the influence of a common tectonic-deformational event.
Acknowledgement
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For the field report a great thanks goes to Dr. Ashis Kumar Das, Dr. Dipanjan Majumdar, and Sri. Shankar Prasad Singh and the
experiences gathered during the six days of field work and a first-year student’s excitement. One cannot thank our teachers
enough for organizing such a learning curve for us.
I am thankful to my fellow classmates for their help in collecting detailed photographs.
“
THANK YOU VERY MUCH
”