Geological Tour at Malekhu Geological Study of Malekhu, Dhading This geological field tour to Malekhu was organized to provide the practical knowledge of geology to us. Malekhu possesses wonderful geological diversities and almost all type of the rocks, structures, and geological factors like rivers, hills, slopes, sedimentation, etc., were available to study within a small area.

Group Members: Pravin Aryal (071BCE260) Prabin Sapkota (071BCE255)

Prajwal Bhusal (071BCE258) Pradip Kumar Yadav (071BCE256) Pragyan Bhattarai (071BCE257)

Supporting Teacher: Rijhu Shrestha

Prakash Chandra Yadav (071BCE259) Pravin Aryal (071BCE260)

Geological Tour, 071/BCE/C-D


OBJECTIVE      

To study the river channel morphology. To study the mass deposition. To identify the rocks and to study their properties. To measure the dip direction and dip amount of the bedding planes. To know the joints, faults, and folds. To realize the engineering significance of geological knowledge.

EQUIPMENTS REQUIRED  Brunton Compass: This compass is composed of delicate mirror and glass components which are vulnerable to shock and moisture thus, requiring care and periodic maintenance for proper application. Geologists use this as an instrument for measurement of the altitudes of structural features. This compass helps in the visualization of lines and planes in three-dimensional space.  Geological Hammer: A hammer was used to test the hardness of rock in the field. It was performed by striking the tip of hammer and the surface of the rock whose hardness was to be determined.  Measuring Tape: A measuring tape was used to measure the distances between different discontinuities such as in the outcrop of rock strata.  Topo sheet: A toposheet is a shortened name for 'Topographic sheet'. they essentially contain information about an area like roads, railways, settlements, canals, rivers, electric poles, post Pravin Aryal (071BCE260) | 1

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offices etc. According to their usage, they may be available at different scales (e.g. 1:25000, 1: 50000 etc, where the former is a larger scale as compared to the latter). They are made on a suitable projection for that area and contain lat-long information at the corners. Thus any point on it can be identified with its corresponding lat-long, depending upon the scale (i.e. if the scale is large, more accurate lat-long).  Goggles: It is used for the safety of our eye from high intensity of the sun light and reflection or refraction of light on the field and also for preventing to reach in our eye the small fragments of the rocks while striking the rocks.  Cap/hat: Cap/hat is used to save the head from dust particles as well as direct encounter of sun light.

CHEMICAL REQUIRED  Diluted HCl acid: It reacts with bases, carbonates, like marbles.

ACKNOWLEDGEMENT The geological field knowledge and field visit is very important especially for a civil engineer. The main work of a civil engineer is to study the feasibility of the construction and stability of structures in different types of land feature including rock, their slope, riverside and clayey portions. Literature alone cannot assist in producing any satisfactory results. Therefore a thorough knowledge of actual field visit counts for its credit. As the geology deals with rocks and stones along with their origin including types of soil, strike, dip-direction and other geological discontinuities such as faults, folds, joints, landslides, use of topography map for proper location of site and other activities. It is therefore very essential to make a field visit. From the field visit we came to know much about structural geology including the above mentioned features. For the basic knowledge of field work of structural geology the two days from 16th of Phalgun to 17th of Phalgun we were taken to Malekhu for geological excursion. This performance was very effective for the partial fulfillment of knowledge and experience. However the three days of tour was not sufficient to fulfill the requirement, we are very grateful for Rhiju Shrestha who helped us during the field trip and taught many important things within the limited time period.

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METHODOLOGY The common methods used in the geological excursion were the site selection and the field observations. Different places suitable for the geological study were selected and their location was determined by the map and the observation related to such structures were taken and copied such as physical appearance, orientation, geological structures. Photographs were taken at many sites. In some, sketches were also plotted to assist the better understanding. In still some cases graphs were also plotted like in rock outcrop observation. And our teacher, Rhiju Shrestha guided us and taught about different geological aspects.

GEOLOGICAL INTRODUCTION OF MALEKHU The place is situated at the Prithvi Highway, Dhading district, 70km southwest of Kathmandu valley. Latitude: 27o50‟38” – 27o45‟50” Longitude: 24o49‟5” – 84o50‟50”

Malekhu River, Malekhu

It is a small part of lesser Himalaya, Central Nepal. From East to West the central Nepal lesser Himalaya may be divided into three transverse zones – a. Chautara–Okhaldunga Metasediment Zone, b. Kathmandu Nappe and c. Gorkha–Nuwakot Metasediment Zone. The Geology of Malekhu resembles with the some part of Kathmandu Nappe and some part of Gorkha–Nuwakot Metasediment Zone. There is a significant thrust called Mahabharat Thrust (MT) which separates two geological sequences (allochthons and

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Autochthons) of lesser Himalaya. The rock of Kathmandu Nappe is divided into Bhimphedi Group and Phulchauki Group whereas Gorkha–Nuwakot Metasediment is divided into Upper Nuwakot and lower Nuwakot Group. TOPOGRAPHY  Very rugged, lesser Himalaya,  Includes hills, river Valleys, river plain, escarpments, spurs, saddies, terrace, etc.  Lowest altitude 340m at Trishuli River and highest altitude 1525m at North of Dharapani village.  Climatically subtropical zone. STRATIGRAPHY Lesser Himalayan Allochthon s

Nuwakot Complex Bhimphedi Group (Pre-Cambrian age)

Markhu Formation, 100m thick, marble, schist Kulekhani Formation, 2000m thick, quartzite, schist Chisapani Quartzite, 400m thick, white quartzite Kalitar Formation, 2000m thick, schist, quartzite Bhainsedobhan Marble, 800m thick, marble Raduwa Formation, 1000m thick, garnetiferous schist

Upper Nuwakot Group (Paleozoic age)

Erosional Unconformity

Phulchauki Group

Kathmandu Complex

Mahabharat Thrust (MT)

Kathmandu Nappe


Lower Nuwakot Group Late-Precambrian age)

Robang Formation, 200-1000m thick, phyllite, quartzite Malekhu limestone, 800m thick, limestone, dolomite Benighat slate, 500-3000m thick, slate, argillites dolomite


Dhading Dolomite, 500-1000m thick, stromatolitic dolomite Nourpul Formation, 800m thick, phyllite, metasandstone Dandagaon Phyllite, 1000m thick, phyllite Fagfog Quartzite, 400m thick, white quartzite with ripple marks Kucha Formation, >3000m thick, phyllite, quartzite

Source: Stratigraphy of lesser Himalaya, Malekhu area, Stocklin and Bhattarai (1977) and Stocklin (1980)

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DAY:- 1st, 2072/ 11/ 16, Sunday OBJECTIVE: STUDY OF RIVER CHANNEL MORPHOLOGY AT TRISHULI RIVER, MALEKHU LOCATION-1 Right bank of Trishuli River, about 200m downstream from Malekhu suspension bridge. And about 100m above the Trishuli River. SHORT INTRODUCTION ABOUT RIVER CHANNEL MORPHOLOGY The running path of water is river. River carries sediments and many more substances. The path of the river is River Channel. The flow of river is expressed in terms of Discharge. Discharge is the volume of water flowing through a point in the given time i.e. Discharge = velocity × cross-sectional area. River Channel The path of the river is known as river channel. And the region from where the river flows is river valley. The process of cutting sideways by water flow is called valley widening. In the river channel the flow of water are categorized in two types of flowlaminar flow and turbulent flow. Nature of flow of water in river is characterized by gradient and velocity. The laminar flow of water is possible where the river has flat gradient and low velocity. The movement of glacier and ground water are generally laminar in nature. Thus flow of water in turbulent is random and eddying. This occurs where the river passes through the narrow neck (path) with boulders. Also falling of water from waterfall is turbulent flow. Types of River Channel 1. Straight River This is a type of river channel in which the path of the river is straight and velocity and velocity gradient is very high. Flow of water in this river channel is turbulent flow. Topography of this type of river is steep relief. This type of channel is found on Himalaya region. Erosion due to this river is very high and occurs deeply but side cutting is low. Deposition is very low. The some portion of the river channel of the given picture of Meandering River can be considered as Straight River. 2. Meandering River This type of river channel is found on mid land and lesser Himalaya, whose velocity of discharge is moderate. Flow of water in this river channel can be laminar as well as turbulent accordingly gradient of path of river channel. Channel of this type of river is

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like snake. Topography of the river is moderate relief. Erosion and deposition occurs equally. The river cuts the side of river greater than deep scouring. 3. Braided River Point bar Concave side Topography of the river is low Deposition relief. Also velocity and gradient of river path are low. So, Convex side generally there is laminar flow of river water. The deposition is higher than erosion. And the depositions are collected along the river path. This is found at Terai region. Activity of River: 1. Erosion Either by physical processes or chemical factors with natural agencies, river wears away of the rocks, that is called as erosion. 2. Transportation The products of both fluvial erosion and weathering constitute the load of the river which are carried downstream along with the flow of running water, is called as transportation. It involves both chemical and mechanical transportation. 3. Deposition It is a collection of the sediments as well many more at the bank of river, sea, or different place form origin. Deposition takes place in small velocity and low gradient. Mass Movement The force of gravity acts to tear the mountains down causing a variety of phenomena collectively called mass wasting or mass movements, where by geological materials are move downward from one place to another. 1. Landslide Generally, it is fast falling of soil along with rocks, water and vegetation due to failure of plane of land. Downward and outward movements of slope forming minerals along surfaces of separation by falling, sliding and flowing at a faster rate, is called as land slide. Specially, land slide occurs at mountain region, tunnels, etc.

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Causes of landslide: a. Geological causes: i. Extensive development of weak rocks ii. Weathering of rock mass iii. Sheared materials iv. Adversely oriented structural discontinuity as bedding, joints, foliation, cleavage, schistosity and faults. v. Seismic activity b. Morphological causes: i. High relief or Steep slopes ii. Undercutting (toe cutting) of banks by deeply incised rivers and streams. iii. Tectonic upliftment or subsidence. c. Physical causes: i. Intense rainfall (Role of water) ii. Rapid snow melt or Glacier Lake Outbrust Flood (GLOF) activation. iii. Volcanic eruption, etc. d. Human (Anthropogenic) causes: i. Deforestation ii. Improper land use iii. Construction activities iv. Water leakage Preventive Measures for Landslides: The preventive measures are based on a. Possible Damage on Human life b. Damage on public Structures like Buildings, roads, canals, bridges, hydropower, etc. c. River flooding due to river damming. Methods of Prevention: a. Drainage management b. Use of retaining Structures c. Slope Reinforcement by rock Bolting d. Slope Treatment e. Afforestation f. Bioengineering (Bio technical) stabilization g. Excavation and filling, etc.

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2. Slope failure/Rock slide Generally it occurs on steep slopes controlled by the discontinuity patterns with in the parent rock. It is composed of boulders. And Water is seldom factor in causing rock slides, although it may weaken bonding along joints and bedding planes. Freeze- thaw action, however, is an important cause. Relatively small dimension movements of weathered rock or soil layer in the slopes are called as slope failures could lead to more stable configuration may redistribute the rock material in less steep slopes and it relief the stress by reducing the high concentration of stress usually present at the valley bottoms. 3. Debris Flow Debris slides are usually restricted to the weathered zone or to surficial talus. Debris flow is a form of rapid mass movement in which loose soils, rocks and organic matter combines with entrained air and water to form slurry that then flows may down-slope. The mass movement associated with steep gullies. Factors responsible for River Channel Morphology 1. Discharge The rate of flow of volume of water of river is known as discharge and it is responsible for the determination of the river channel morphology. High discharge is found in big rivers. 2. Velocity Velocity of river water is also responsible for determination of the river channel morphology. If the velocity of the river is high then the erosion is high, and the river cuts the bank highly. 3. Lithology The nature of rocks along the channel and along the side may effect for the river channel morphology. Some types of rocks are more easily eroded by river water. The river channel, which passes through the limestone, will be straight. 4. Load The river channel may also be affected by the load condition of the river. If the river is fully loaded it will not have further capacity to erode and transport the materials of the channel. But if the river is under loaded it will erode its channel effectively.

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Land Forms developed by the River 1. Terrace (flood plains) Bench like flat surface occurring on side of the river valley is called terrace. The areas of low and relatively flat land bordering the channel on one or both sides, at the bank level are called flood plains. Terraces are of three types a) Higher Terrace b) Middle Terrace c) Lower Terrace 2. Channel Bar The land formed along the river by the deposition of sediments, is channel bar. 3. Oxbow Lake Meandering rivers are Point Bar categorized by point bars deposition developed on the concave side of its bent. When meandering joins; it forms a lake is called as oxbow lake. If the narrow landform joins in above picture then there, middle terrace will be an Oxbow Lake in near future.

Cut Bank

4. Alluvial Fans Broad, low and cone-shaped deposits are called as Alluvial Fans and slope of the land formed is less than 10o. This is mainly due to river deposition at sea, leveled land. 5. Colluvial Fans Narrow, steeped cone shaped deposits are called as Colluvial Fans and the slope of the land formed is greater than 10o. This is mainly due to landslide.

Ghumarighat, Nawalparasi Higher Terrace Middle Terrace Lower Terrace Middle Terrace

6. Natural Levees Broad, low ridges formed along the bank of river during floods are called as natural levees.

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7. Point Bars Point bars are the deposits deposited by river on its concave side at the bent of the river are known as the point bars. 8. Deltas Deltas are formed at the mouth of the rivers. Deltas are defined as alluvial deposits of roughly triangular shape that are deposited by major rivers at their mouths i.e. where the river enter a sea. Erosional Land Forms: 1. River Valley: River valleys are the outcome of the river erosion. It is low land surrounded by inclined hills and mountains. 2. Gulley: A small V-shaped valley is called gulley. 3. Gorge: Very deep and steep narrow valley is called gorge. 4. Canyon: Special gorge with layers cut down by river are essentially horizontally stratified is called as canyon. 5. Terrace: It is bench like flat structure occurring on sides of the river valley is called terrace. OBSERVATION AT FIELD The field, we were visited, is in lesser Himalaya region. And so thus, river is Meandering River. And it is like a snake, flowing towards south-west direction and making river valleys, one of those is Malekhu village. The river is originated from Himal, melting snow.

Vegetation Flood Level

Flood Level

Flood Level

Natural Levees

This area can be considered as Straight River.

Trishuli River

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At first, we observed the river channel cutting and deposition, which is shown in the picture. The deposition is in the form of point bar deposition towards concave position of the river. And there is no deposition towards tangential direction of the river path which is cut bank. While taking some range/part of river, the character of river is found to be straight where the velocity of the water flow is relatively greater than some other parts‟. The velocity of the river is slow, where the river is broadened. While seeing from our location towards next bank of river, we noted to the flood level at the corner of bank. In which we can observe the vegetation above the flood level and the bed rock is exposed below the vegetation. There is a join of stream of water, called Thopal Khola, near the cut bank. And there is a type deposition like alluvial deposition.

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OBJECTIVE: IDENTIFICATION OF ROCK ALONG THE TRISHULI RIVER AT MALEKHU LOCATION-2 Right bank of Trishuli River, about 150m downstream from Malekhu suspension bridge. And about 100m above the Trishuli River. SHORT INTRODUCTION ABOUT ROCK / PETROLOGY The branch of geology that deals with the study of rock is known as petrology. Petrographic classification 1. Igneous Rock 2. Metamorphic Rock 3. Sedimentary Rock 1. Igneous Rock The rock formed by the solidification of magma either below or above earth surface. The rocks which are formed below the earth surface are called intrusive bodies or plutonic rocks whereas those which are formed by consolidation of Magma (called lava at surface) on or above the earth surface are called extrusive bodies or volcanic rocks. There is another classification of igneous rock called hypabyssal rocks which are formed at shallow depth and included in intrusive rocks. Magma: This is naturally occurring high temperature solution of silicates; water and gases which are generated deep with the earth crust of upper mantle. It is the source of igneous rocks. Since the volatile components of a magma are usually lost during consolidation, the igneous rocks formed cannot be said to entirely represent the original magma. Lava: Molten rock or magma ejected from opening at the weak surface of earth is called as Lava. Such opening may be located in craters or along flanks of volcanoes. Measurements of lava temperatures range from 105oC to 1190oC for tholeitic basalt (rock) to 725oC to 850oC for dacite (rock). The viscosity of lava depends mainly on the chemical, composition, temperature and pressure and the dissolved volatile content. Basic lavas are less viscous than acidic lavas at the same temperature. Viscosity generally decreases with decreasing SiO2 content. Features of Igneous rock:  Generally hard massive and compact with interlocking grains  Absence of fossils  Absence of bedding or foliation plane. Pravin Aryal (071BCE260) | 12

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 Enclosing rocks are backed  Usually contain much feldspar etc.


Igneous Rock

Classification of Igneous rock Based on texture: a) Intrusive i. Plutonic: These have cooled deeper below the earth‟s crust, deep seated, coarse grained are called plutonic rocks. Example: Granite, diorite, gabbro etc. ii.

Hyperbassal: shallow seated, porphyritic. These are formed by the solidification of magma at shallow depth. They possess inequigranular size of minerals ranging from coarse to fine. This type of texture is called as porphyriric texture, e.g. granodiorite, tonalite, syenite etc.

b) Extrusive: volcanic rock found on earth surface, fine grained.

Based on composition: a. Acidic Igneous Rock: Abundant felsic (light colored) minerals like feldspar, quartz. eg: Granite. b. Basic Igneous Rock: Abundant mafic (dark colored) minerals like biotite, tourmaline. eg: Gabbra, Ambolite. c. Ultra-mafic Rock: >90% mafic mineral. eg: Dunite, Pyroxinite. d. Intermediate Rock: 52% - 66% SiO2. eg. Granodiorite e. Ultra-basic Rock: <45% Sio2. eg. Peridotite. Pravin Aryal (071BCE260) | 13

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2. Metamorphic Rock The rocks that are formed by the action of temperature and pressure on pre-existing sedimentary or igneous rocks are called metamorphic rocks. The metamorphic rocks which are derived from igneous rocks are called as ortho-metamorphic rock and those derived from sedimentary rocks are called para-metamorphic rocks. Features of Metamorphic Rocks:  Generally hard with interlocking grains,  Foliated, gneissose, slaty structures, Classification of Metamorphic Rock: According to Texture: a. Foliated: platy minerals, eg: slate, phyllite, gneiss, granulite, schist. b. Non-foliated: non-platy minerals, eg: amphibolites, marble, quartzite. According to Crystal size: a. Aphanitic: small grains, no crystal, eg: slate, phyllite. b. Phaneritic: large grains, crystal eg: gneiss, marble, schist. c. Porphyroblastic: larger grains surrounded by finer mass (ground mass) d. Poikiloblastic: Grains containing inclusions of other minerals e. Grnoblastic: Having equidimensional mineral grains f. Lepidobalstic: Abundance of platy mineral grains (micas, talc, chlorite, etc) 3. Sedimentary Rock The rocks formed by the compaction, cementation and sedimentation of sediments in depositional basin are called as Sedimentary Rock. Features of Sedimentary rock:  Generally soft and stratified.  Presence of fossils.  Presence of sedimentary structures eg. Mud cracks, ripple marks. Classification of Sedimentary Rock: Based on mode of Deposition: 1. Ortho-chemical sedimentary rock: eg. Evaporite, Cherts. 2. Allo-chemical sedimentary rock: Lime stone, Dolomite. 3. Terrigeneous Sedimentary rock: a. Rudaceous Rock: Boulder eg: Conglomerate b. Arenaceous Rock: Sand size, eg: Sand Stone c. Argillaceous Rock: Silt or Clay, eg: Mud stone, Shale. Pravin Aryal (071BCE260) | 14

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S.N. 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12.

Properties Location Color Texture Structure Grain Size Sp. Gravity Mineral Composition Typical Feature Identification Occurrence Engineering Significance Remarks

Rock-1 Description location-2 Silver and yellow Aphanitic well-developed foliation plane Fine Low Clay minerals Soapy in touch, well developed foliation plane PHYLLITE Mudstone, shale None Metamorphic rock

Note: quartz vein found, crystalline and hard Short Description of Phyllite: Phyllites are the metamorphic rock upgrade of slate. Comppositionally, they are more or less similar to slate but the grain size is somehow larger. These are the most perfectly foliated metamorphic rocks. It differs from slate by a shiny lustre imparted by mica flakes. They create swelling problem during tunnel excavation, very limited bridging capacity are found in phyllites. High pressure may create small folds in these rocks called crenulation cleavage.


Quartz Vein Rock-1

Quartz Vein: It is crystalline and hard rock found between phyllite. Quartz is often found in veins that cut through rocks. Although the term "vein" suggests this, the veins of quartz and other minerals are usually not thin tubes, but rather thin sheets. The veins can form under various conditions, and depending on the conditions, may or may not bear quartz crystals in them.

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S.N. 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12.

Properties Location Color Texture Structure Grain Size Sp. Gravity Mineral Composition Typical Feature Identification Occurrence Engineering Significance Remarks

Rock-2 Description about 50m upstream of location-2 White phaneritic fine structure Fine Medium Calcite White in color and radially reacts with dil. HCl MARBLE limestone, dolomite Cement manufacture, flooring, construction, decoration Metamorphic rock

Short Description of Marble: It is a non-foliated metamorphic rock, and is the metamorphic equivalent of calcite, limestone or dolomite. When pure marble is white, but varous impurities may create a wide range of color. It reacts with acids easily. It is widely used in flooring and making concrete.


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OBJECTIVE: TO MEASURE THE DIP DIRECTION AND DIP AMOUNT OF THE BEDDING PLANES LOCATION-3 Right bank of Trishuli River, about 100m downstream from Malekhu suspension bridge. And about 1m altitude from the Trishuli River. SHORT INTRODUCTION ABOUT DIP DIRECTION AND DIP AMOUNT Strike: Strike is the horizontal direction of slope. It may be defined as the direction of a line formed by the intersection of the bedding plane with horizontal plane. Dip amount: It is a acute angle between the bedding and a horizontal plane. Dip line represents the maximum inclination of bed or foliation plane. Dip direction: It is the direction of inclination of a bed or slope of mountain or foliation plane.

Fig: Measurement of Dip Direction and Dip Amount using Brunton Compass


Dip direction/dip amount


Dip direction/dip amount


1. 6. 11. 16. 21. 26.

352o/76o 352o/82o 355o/81o 358o/81o 354o/90o 347o/79o

2. 7. 12. 17. 22. 27.

354o/71o 351o/71o 356o/84o 357o/83o 359o/84o 345o/84o

3. 8. 13. 18. 23. 28.

Mean Dip direction/ Dip amount =

Dip direction/dip amount


Dip direction/dip amount


Dip direction/dip amount

356o/80o 4. 354o/79o 5. 353o/73o 354o/66o 9. 353o/84o 10. 349o/86o o o o o 354 /90 14. 357 /85 15. 354o/77o 347o/84o 19. 346o/81o 20. 359o/86o 357o/77o 24. 353o/78o 25. 351o/82o 360o/86o 29. 358o/85o 30. 356o/82o Observed by: Pravin Aryal (071BCE260)

= 353.7o/80.9o

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Some knowledge before 2nd Day observation about Structural Geology: Fold: It is undulation on the earth surface. Folds results due to ductile deformation of rocks. The bending of rock strata is due to compressional forces acting from opposite direction. Parts of Fold: 1. Hinge: The hinge of a fold is the line of maximum curvature. 2. Axial Plane: It is imaginary plane made by joining all the hinge lines which divides the fold as symmetrically as possible. 3. Axis: The axis is a line parallel to the hinge or it is the line of intersection of the axial plane and ground plane. 4. Limbs: The sides of a fold are called limbs or flanks. Every limb is mutually shared by two adjacent folds. 5. Height: It is the vertical distance between the hinge of the adjacent anticline and syncline. 6. Length: It is a distance between axial planes of same folds (syncline to syncline or anticline to anticline). 7. Angle of Fold: It is a angle made by the angle made by the intersection of the two tangents drawn through the adjacent limbs.

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Types of Folds: 1. Antiform: Any upwardly convex structure is termed as antiform. Here the age relationship between the upper and lower set of beds is of complex type i.e. stratigraphy is known. 2. Syncform: Any upwardly concave structure is termed as syncform. 3. Anticline: It is generally convex upward; the two limbs dip away from each other or in the same direction at same or different angles. The older rocks are found in the core.

4. Syncline: It is convex downward; where the younger rocks are found in center. 5. Anticlinorium: It is a large, composite anticline composed of several small folds. 6. Synclinorium: It is a large, composite syncline composed of several minor folds. 7. Symmetrical fold: This is the fold in which the axial plane is vertical and both the limbs have the same amount of dip. 8. Asymmetrical fold: This is the fold in which the axial plane is inclined and both limbs have different dip amount.

9. Recumbent fold: It is an over turned fold in which the axial plane is horizontal or more nearly so.

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10. Isoclinal fold: It is a fold in which two limbs dip is at equal angle in the same direction. 11. Overturned fold: It is a fold in which the axial plane is inclined and both the limbs dip at the same direction usually at different angles. 12. Parallel fold: Concentric folds with uniform thickness are called parallel folds. 13. Open or Gentle fold: It is a fold having interlimbed angle is greater than 70o. 14. Closed fold: It is a fold having interlimbed angle lie between 30o to 70o. 15. Tight fold: It is a fold having interlimbed angle is below 30o. 16. Plunging fold: If the axis of fold is not horizontal, then the fold is Plunging fold. Faults: Faults are welldefined cracks along which the rock masses on either side have relative displacement. The altitude of fault is defined in terms of their Fault line strike and dip. The block above the fault plane is called as hanging wall whereas the block below the fault plane is called as foot wall. The term slip is used to indicate relative displacement on the opposite side of the faults. The „net slip‟ is the total displacement between two opposite blocks. Types of faults: 1. Normal fault: In this fault the hanging wall goes down relative to the foot wall. 2. Reverse: In this fault the hanging wall appears to have gone upward relative to the foot wall.

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3. Thrust fault: In this fault the hanging wall goes up having dips between 45o to 10o. 4. Over-thrust fault: In this fault the hanging wall goes up having dips below 10o. In this case net slip is larger than in other faults. 5. Detachment fault: It is low angled normal fault. 6. Strike slip fault: When the movement is parallel to the strike of the fault plane such faults are called strike slip fault. Joints: A joint is a fracture in a rock in which there is no relative displacement between the sides. Joints are relatively smooth fracture. A series of parallel joint is called joint set. Joints are formed due to the result of either diastrophism (tension) or contraction. Based upon their orientation to the axial planes and axes of folds, the types of systematic joints are:  Longitudinal joints – Joints which are roughly parallel to fold axes and often fan around the fold.  Cross-joints – Joints which are approximately perpendicular to fold axes.  Diagonal joints – Joints which typically occur as conjugate joint sets that trend oblique to the fold axes.  Strike joints – Joints which trend parallel to the strike of the axial plane of a fold.  Cross-strike joints – Joints which cut across the axial plane of a fold. Cleavage: Property of rock by which they break along parallel surface of secondary origin. Schistosity is term applied to rock cleavage especially in schist, a metamorphic rock. Commonly used terms for the cleavage are 1. Slaty cleavage: due to parallel arrangement of platy minerals. 2. Fracture cleavage: due to closely spaced joints. 3. Shear cleavage: due to closely spaced fractures, along which there has been some displacement 4. Slip cleavage: due to crinkle or caused by small folds. 5. Bedding cleavage: parallel to the bedding planes similar to slip cleavage. 6. Axial plane cleavage: parallel to the axial plane. Unconformity: A surface of erosion or non-deposition that separates younger strata from older rocks. Formation of an unconformity involves three main processes: erosion of old strata, deposition of new strata above older and tectonic activity (not necessary in all cases).

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Classification of unconformity: 1. Angular unconformity: If the overlying and underlying rocks are not parallel, such unconformity is called angular unconformity. The altitude of the rocks above and below the plane of discontinuity differs. 2. Disconformity: In a disconformity, the formations (beds) on opposite sides of the unconformity are parallel. 3. Local Unconformity: It is similar to the disconformity but it is local in extent, the time involved is short. 4. Non-Conformity: Structures in which the older rocks are made up of plutonic origin and younger rocks of sedimentary origin, is called non-conformity.

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DAY:- 2nd, 2072/ 11/ 17, Monday OBJECTIVE: TO IDENTIFY THE ROCK AND STUDY OF GEOLOGICAL STRUCTURE ALONG THE MALEKHU RIVER AT MALEKHU LOCATION-3 Banks of Malekhu River, upstream from Highway. OBSERVATION AT FIELD S.N. Properties 1. Location 2. 3. 4. 5. 6. 7. 8.

Color Texture Structure Grain Size Sp. Gravity Mineral Composition Typical Feature

9. 10. 11. 12.

Identification Occurrence Engineering Significance Remarks

Rock-3 Description about 70m upstream, left bank of Malekhu River from highway Light Gray Phaneritic Foliation plane Medium Grain Medium CaMg(CO3)2 presence of lichen on surface of rock and reacts with dil. HCl in powder form DOLOMITE limestone, dolomite Used as foundation material Metamorphic rock

Short Description of Dolomite: It is similar to limestone. It can be distinguished by chemical test which reacts with acids only in powder form. It is formed by the alteration of limestone in which part of the calcium is replaced by magnesium. This process is called as dolomitization. Generally dolomite is a good foundation material unless it is cavernous. The dolomite foundation of the dam may be strong if it is cavity free otherwise a serous leakage hazard may occur. Lichens NOTE: If lichens are present on the rock surface then it may be either limestone or Dolomite or Marble.

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Rocks Surface like Elephant skin (Elephant skin weathering): Many massive carbonate rocks like limestone, marble and dolomite show elephant skin weathering, so Cleavage called because of its resemblance to the rough, weathered hide of elephants. This weathering starts out as minute, random cracks in the rock that are exposed to rainwater. Rainwater is slightly acidic because atmospheric carbon dioxide (CO2) Rock surface Like dissolves in water (H2O) to form Elephant Skin carbonic acid (H2CO3). This slightly acidic rainwater then seeps into the cracks and dissolves a thin layer of limestone, converting it to calcium bicarbonate. The bicarbonate remains in solution and runs off, thereby leaving an enlarged crack. Over many years, the cracks deepen and widen, resulting in the aptly named surface. Elephant skin weathering in found almost exclusively on fine-grained carbonate rocks. Weathering (Weakness of rocks): It is physical and chemical breakdown of the rock material and a major process in the formation of soil. Weathering process can be divided into three types: 1. Physical Weathering: In this weathering the mineralogical composition is not affected. And the factors responsible for the physical weathering are: a. Temperature fluctuation: It is also called thermal weathering. The continuous periodic expansion and contraction of rocks due to diurnal fluctuation of temperature which leads to the formation of cracks parallel to the heated surface and later to the flacking off the upper layer. The process of temperature breakdown in rocks is called exfoliation. Due to volumetric expansion of rocks leads for cracks. b. Variation in pressure: Most of the igneous and metamorphic rocks are formed at depth under high pressure and temperature. The formed rocks have closely spaced joint system and fractures parallel to the surface topography.

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c. Growth of crystals: The fractures and joints of rocks may be filled with water containing soluble salts of rocks and minerals. With the evaporation of water, salts start to crystallize and grow. They exert ultimately leading to fragmentation. d. Freezing of water: Water trapped in pores, fissures, and crevaces of rocks, when freezes, exert enormous pressure on the wall of pores or fissures, leading to fragmentation. 2. Chemical Weathering: It is mineralogical and chemical changes that occur to the rocks at the earth atmosphere interface. As minerals in igneous and metamorphic rocks are formed under high temperature and pressure at depth when come to earth surface then they become unstable due to lower temperature and pressure. And then chemical weathering occurs by hydration, oxidation, dissolution, hydrolysis and carbonation. For example: 1. Oxidation: FeS2 + nH2O + mO2 → FeSO4 → Fe2(SO4)3 → Fe2O3. nH2O. Pyrite






2. Hydration: CaSO4 + 2H2O → CaSO4.2H2O Anhydride



Fe2O3 + nH2O → Fe2O3.nH2O Hematite



3. Hydrolysis: K2Al2SiO16 + nH2O + CO2 → H4Al2Si2O9 + K2CO3 + SiO2.nH2O Feldspar


MgFeSiO4 + 2H2O → Mg(OH)2 Olivine



Magnesium Hydroxide

H2SiO3 silicic Acid

+ FeO Ferrous Oxide

4. Carbonation: CaCO3 + H2O + CO2 → Ca(HCO3)2 2KAlSi3O8 + H2CO3 + H2O → K2CO3 + Al2Si2O5(OH)4 + 4SiO2 Orthoclase


3. Biological Weathering: The process of weathering which are mainly related to the activities of plants, animals, and organism like bacteria lichens, etc. are known as biological weathering. Plant roots, growing between jointed rocks exert an expansive force tending to widen and existing opening and sometime creates new fractures. Bird dropping may be capable of weathering limestone. With the decay of dead parts of plants and animals, chemically active fluids are produced like carbon-dioxide, humic acid, nitric acid, Pravin Aryal (071BCE260) | 25

Geological Tour, 071/BCE/C-D

ammonia, etc. These substances are capable of bringing about rock weathering. Human beings themselves are important agent of destruction. Mass Weathering Grades used in Engineering: Grade Type Characteristics I Clear Weathered Fresh original rock without weathering. II Slightly Weathered Discolored along opening only. III Moderately Weathered Rock Mostly discolored less than half decomposed. IV Highly Weathered Discolored rock with openings; up to half of the rock mass is decomposed. V Completely Weathered Mostly soil fragments of original rock (but discolored) or rock structure may be present. VI Residual Soil Soil with characteristic horizon development.

Grade-V: Completely Weathered rocks.

S.N. Properties 1. Location 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12.

Color Texture Structure Grain Size Sp. Gravity Mineral Composition Typical Feature Identification Occurrence Engineering Significance Remarks

Rock-4 Description About 300m upstream, right bank of Malekhu River from highway Black and white Hollow crystalline Crystalline Coarse High dark minerals, feldspar, Quartz light minerals with dark minerals (Genolith) GRANITE Plutonic Construction material Igneous rock

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Short Description of Granite: It is granular plutonic rock. Granite may be defined as the Plutonic light colored Genolith igneous rock. These are among the most common igneous rock. Two most common and essential mineral constitutes of granite are Quartz and Feldspar. The first is always recognized by its vitreous luster, with MHN 7 and cleavage less wide translucent appearance. Feldspar, forming Granite may be of two types: K-Feldspar, commonly Orthoclase and the soda bearing Plagioclase Feldspar like Albite and Oligoclase. Feldspar microcline may occur in some granite. Agra Granite was found in the right bank of Malekhu Khola south west of "Chhapan Danda". The study of metamorphic rocks (now exposed at the Earth's surface following erosion and uplift) provides us with very valuable information about the temperatures and pressures that occur at great depths within the Earth's crust.

S.N. Properties 1. Location 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12.

Color Texture Structure Grain Size Sp. Gravity Mineral Composition Typical Feature Identification Occurrence Engineering Significance Remarks

Rock-5 Description About 500m upstream, middle of Malekhu River from highway Dirty brown Aphaniritic Rudaceous Fine to coarse Medium various rock fragments boulders, cobbles, pebbles, sand CONGLOMERATE various rocks None Sedimentary rock

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Short Description of Conglomerate: Conglomerate may be considered as the consolidation of the gravels. Particle size varies from boulder to granule. Mostly the fragments are rounded in nature, but, if the fragments are not rounded then, the rick is classified as a „breccia‟. If there is a scattering of large rounded pebbles or boulders are embedded in clay, the resulting formation is fanglomerate. If the large fragments have resulted from volcanic ejection and are cemented with small fragments, the resultant mass is agglomerate. Only well cemented conglomerates are considered suitable for engineering purposes.

S.N. Properties 1. Location 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12.

Color Texture Structure Grain Size Sp. Gravity Mineral Composition Typical Feature Identification Occurrence Engineering Significance Remarks

Rock-6 Description About 1500m upstream, right bank of Malekhu River from highway radish brown Phaniritic Hollow crystalline Fine grain High SiO2 Scratches the Geological Hammer QUARTZITE sand stone Construction materials Metamorphic Rock

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Short Description of Quartzite: It is the metamorphic equivalent of quartz or sandstone. The principal constitute is quartz. It is a very compact rock and high grade metamorphic rock with interlocking quartz-grains. It is a very sound rock for engineering foundation, excavation and concretion. Garnetiferrous Schist: Foliation/schistose with grain size fine to coarse with reddish gray with clay and garnate minerals. It is used as stones in jwellery. Garnetiferous mica schist: Aluminous muscovite-biotite schist, locally having subordinate amphibolite layers. Garnet Biotite: Biotite is a name used for a large group of black mica minerals that are commonly found in igneous and metamorphic rocks. These include: annite, phlogopite, siderophyllite, fluorophlogopite, fluorannite, eastonite and many others. These micas vary in chemical composition but are all sheet silicate minerals with very similar physical properties. A generalized chemical composition for the biotite group is: K(Mg,Fe)2-3Al1-2Si2-3O10(OH,F)2 The name "biotite" is used in the field and in entry-level geology courses because these minerals generally cannot be distinguished without optical, chemical or x-ray analysis. CONCLUSION This geological field tour to Malekhu was organized to provide the practical knowledge of geology to us. The geological field tour to Malekhu aimed to provide the acquaintance and knowledge of geological element and their properties as well as features. The scope of field study outlined before were fully met with the co-operation of the faculty member and Malekhu possesses wonderful geological diversities and almost all type of the rocks, structures, and geological factors like rivers, hills, slopes, sedimentation, etc., were available to study within a small area. Our Malekhu tour was very interesting, informative, subjective and practical with engineering scope of our future carrier. This tour was organized according to our syllabus and we are thankful to the department. And at last specially thank you, Geologist Rijhu Shrestha, Sir.

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Reference:  “Geology for Civil Engineers” by Kabiraj Paudyal, Oxford International Publication.  Stratigraphy of lesser Himalaya, Malekhu area by Stocklin and Bhattarai (1977) and Stocklin (1980)

 Google

Pravin Aryal (071BCE260) | 30

Geological Tour Report.pdf

Pravin Aryal (071BCE260). Prabin Sapkota (071BCE255). Prajwal Bhusal (071BCE258). Pradip Kumar Yadav (071BCE256). Pragyan Bhattarai (071BCE257).

3MB Sizes 5 Downloads 232 Views

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