GROUP NO. 5

1. NITESH SUBEDI (13/072)

2. MILAN KUMAR RAI (10/072)

3. PRAKASH KHANAL (14/072)

4. SANJAY RIZAL (17/072)

This is to certify that the candidates (M.Sc. 1st

Semester, Engineering Geology) have worked

satisfactorily under my supervision and the report embodies their own work. I therefore

recommend this report for acceptance.

------------------------- -----------------------------

Date Field Incharge

CENTRAL DEPARTMENT OF GEOLOGY

TRIBHUVAN UNIVERSITY

Kirtipur, Kathmandu, Nepal

ACKNOWLEDGEMENT

We are grateful to all our respected teachers of Central Department of Geology, Tribhuvan

University for organizing the field work to Jugedi-Muglin-Besisahar area and helping us in a

great way to gain field knowledge and working methodology required in Engineering

geology.

We are also very grateful to Dr. Lalu Prasad Paudel (Head of the Central Department

Geology, Tribhuvan University), Dr. Ranjan Kumar Dahal (Co-ordinator of EGEO Program)

Dr. Kabiraj Poudel, Dr. Khum Narayan Paudyal and for all the help and guidance that they

provided with open heart in the field as well as out of field.

Similarly, we are grateful to the Riverside Hotel and Lodge family and the local people of

Aanbu Khaireni because without their help and co-operation, our fieldwork would have been

very difficult.

TABLE OF CONTENT C O N T E N T

CHAPTER-1 INTRODUCTION

1.1 Accessibility

1.2 Geomorphological Features

1.3 Climate

1.4 Vegetation

1.5 Hydrology

1.6 Limitation

CHAPTER-2 OBJECTIVES

CHAPTER -3 LITERATURE REVIEW

3.1 Previous Works

3.2 Regional Geology

3.2.1 Stratigraphy

3.2.2 Structures

3.2.3 Sedimentary Features

3.2.4 Fossils

CHAPTER-4 METHODOLOGY AND MATERIALS

CHAPTER-5 RESULTS

5.1 Geological Structures

5.1.1 Folds

5.1.2 Thrusts

5.1.3 Bedding/Foliation

5.1.4 Lineation

5.2 Metamorphism

5.3 Magmatism

CHAPTER-6 DISCUSSIONS

6.1 Discussion on Fold

6.2 Discussion on thrust and faults

6.3 Discussion in Metamorphism

6.3.1 Dumre to Besisahar

CHAPTER-7 CONCLUSIONS

CHAPTER-8 REFERENCES

List of Figures

Fig. 1 – Study Area.

Fig. 2 – Pinching and widening of trishuli river indicating quartzite and phyllite.

Fig. 3 – Generalized columnar section of rocks of the midland group in muglin bandipur.

Fig. 4 – Ripple marks.

Fig. 5 – Stromatolite.

Fig. 6 – Cross-Bedding.

Fig. 7 – Angular Unconformity Separating siwalik and lesser Himalaya.

Fig. 8 – Bone fossils.

Fig. 9- Core of Jalbire Syncline.

Fig. 10 – Z type fold observed in dadagaon phyllite(north of besisahar) at garnet zone.

Fig. 11- Schemetic crosssection along dumre besishar road.

Fig. 12- Shear zone observed along dumre bandipur section.

GEOLOGICAL STUDY OF MUNGLING-DUMRE-

BESISAHAR SECTION

1. INTRODUCTION:

A nine day geological field work was conducted in Jugedi-Muglin-Bandipur-

Besishar area from 2073/07/02 to 2073/07/11 for the partial fulfillment of

requirement in the Engineering geology, at the central department of geology,

Tribhuvan University, Kirtipur. The study area include middle part of siwalik

and the lesser Himalaya.

The lesser Himalaya is a folded and trusted belt with rugged topography. There

is great variation in the tectonic of lesser Himalayan zone of Nepal from east to

west. The study area mainly covers central and western Nepal. There are several

thrust sheets occupying the core of major synclines. The study area include the

Mahabharat synclinorium (stocklin and bhattarai 1977, stocklin 1980) in the

east and Gorkha – Kuncha Anticliorium in the north (Arita et. Al. 1973, pecher

1977).

The area exposes a wide section of the lesser Himalaya low-grade

metasediments along the road and river sections. It shows the complex

stratigraphy and structures. It is bordered in south by Main Boundary Thrust

(MBT) and in the north by Main Central Thrust (MCT).each of the zone is

characterized by its own lithology, tectonics structures, metamorphism and

geological history. The MBT is a low-angle reverse fault that has brought the

older lesser Himalayan rock into Siwalik while on other hand MCT brought the

higher Himalayan crystalline into lesser Himalaya. It is located in between

latitude 28o15’0’’ to 27

o45’0’’ and longitude of 84

o22’30’’ to 84

o37’30’’. The

topomaps of toposheet numbers, 2784 o3c Muglin, 2784 o2D jugedi, 2784 o2B

Dumre- Bandipur are used for the fieldwork.

1.1 ACCESSIBILITY:

The study area was easy accessible as every section was possessed by motor

road. Most of the study was done along the highway and other area were also

have been connected by roads to highway. The study area lies about 100-150

km west of Kathmandu.

1.2 GEOMORPHOLOGY:

The area covers fold-and-thrust belt with rugged topography. River cut valleys,

river terraces, gentle to steep slopes are major morphological features of this

area. The highest peak of about 2000m, spurs and some Kast topographical

features has been observed.

Figure 1. Study Area

1.3 CLIMATE:

This zone experiences hot and humid weather. It receives sufficient amount of

rain fall and considerable sunshine. It provides the ideal growing condition for

vegetation. The temperature of this area rarely exceed 35oC, a day time

maximum temperature is about 32oC is more common and minimum

temperature fall no lower than about 18oC. This temperature is maintained with

little variation throughout the year. So the area possesses tropical to sub-tropical

climatic condition.

1.4 VEGETATION:

This region receive sufficient amount of rainfall and considerable amount of

sunshine, some river valley are covered by dense to moderately dense forests.

The terrace deposits are usually used for the cultivable land and settlement. The

main crops of this zone are rice, barly, maize; wheat etc. cash crops like potato,

ginger, sweet-potato are also cultivated. The forest element consists of Shorea

robusta, Acacia Catechy, Dalbergia Sisso and Bamboo.

1.5 HYDROLOGY:

There is diversity in the topography of the study area and is mainly drained by

Trisuli,Seti, Marsyangdi, Daraudi and Chaudi khola with many other tributaries

like khudi-khola, Andhi-khola, Ludi-khola etc. The area as a whole exhibits

high drainage density. High flooding in the streams occurs during the rainy

season with high increase in water level.

1.6 LIMITATION:

The study area possesses rugged topography and has several limitations. Some

are listed belowEach and every section is not exposed and is covered by dense

vegetation.

Some sections are extremely steep and are not reachable.

Some section are highly weathered and are covered by soil.

2. OBJECTIVES:

The main objectives of the study area were described as follows:

• Field mapping.

• Identification of different types of rocks and proper attitude of bedding plane

and joint plane.

• Lithology, Stratigraphy and Structural geology of the upper part of the siwalik

group and the lesser Himalayan rocks.

• Interpretation of depositional environment with the help of fossils and other

geological structure found.

• Study of different formation of midland group of lesser Himalaya.

• Study of metamorphism of the study area.

• To prepare detailed columnar section and generalized columnar section of the

study area

• To prepare detailed cross – section of the study area.

• Geological map and its technique of its preparation.

3. LITERATURE REVIEW:-

3.1. PREVIOUS WORKS

Many authors have includedthis area in their regional geological

investigation of Central Nepal (Auden 1934; Bordet et. Al 1964; Hagen 1969;

Arita et. Al 1973; Colchen et. Al 1980). Also, very few researchers have shown

stratigraphic details of the present study area. Stocklin and Bhattarai(1977)

and Stocklin (1980) prepared a detailed geological map of Mugling-Anbu

Khaireni – Labdi area The area comprises the Kuncha Formation, Fagfog

Quartzite, Dandagaon Phyllite, Nourpul Formation, Dhading Dolomite, and

Benighat Slate from bottom to top.

The detail columnar section of lithostratigraphy of Nuwakot Complex proposed

by Stocklin and Bhattarai(1977) and Stocklin(1980) is given below:

3.2. REGIONAL GEOLOGY

3.2.1. STRATIGRAPHY

The study area from Jugedi to Besi shahar mainly consists of the rocks of lesser

Himalaya.Lesser Himalaya is separated by Main Boundary Thrust (MBT) in

South and by Main Central Thrust (MCT) in North and is divided into Nuwakot

Complex and Kathmandu Complex.

In our study area we can observe different rocks of Nuwakot Complex.

The formations occur here are Kuncha Formation, Fagfog Quartzite,

Dandagaon Phyllite, Nourpul Formation, Dhading Dolomite and Benighat Slate.

Among these six formations, Kuncha Formation is the oldest formation whose

lower part is not defined and Benighat Slate is the youngest one.

a) KUNCHA FORMATION

This formation is well distributed in Mugling-Manakamana-Anbu

Khaireni area.

In study area, only upper part of Kuncha formation is exposed.

This formation mainly consists of green-grey, medium to coarse grained

metasandstone, quartzite and phyllite.

Elongated quartzite, muscovite, sericiteand chlorite are also found.

In southward part, from Mugling, amphibolites and greenschist layers

were observed.

The thickness of this formation is more than 1000m.

b) FAGFOG QUARTZITE

A complete sequence of Fagfog Quartziteis observed along the road

section about 2 km south of Muglin and is the marker unit in the area.

It consists of thi to thick bedded white quartzite with thin partings of

phyllite.

The beds are usually parallel and continuous to several meters.

Graded beddings, parallel and cross laminae and ripple marks was

observed.

The phyllite alternating with quartzite shows silky luster and soapy

weathering surface due to the presence of chlorite and sericite.

The Fagfog Quartzite is followed up section by the Dandagaon Phyllite

with very sharp contact.

The thickness of the unit is about 400m.

Figure 2. Pinching and widening of Trishuli River indicating quartzite and phyllite.

c) DANDAGAON PHYLLITE

The Dandagaon Phyllite is extensively distributed to south and south-

west of Mugling along the Mugling-Narayanghat road section and

around the villages of Loprang.

The lower part of this formation comprises black phyllite, gritty,

calcareous phyllite and dirty grey quartzite.

The upper part of this formation comprises of alternating bands of finely

foliated black phyllite and grey gritty phyllite.

Stocklin and Bhattarai(1977) and Stocklin(1980) mapped this phyllite as

a member of Kuncha Formation.

This formation is exposed in Chipleti.

The Dandagaon Phyllite is followed up section by the Purebesi

Quartzite(Nourpul Formation) with a sharp and conformable contact.

The thickness of this formation is about 200m.

d) NOURPUL FORMATION

The Nourpul Formation is exposed extensively in the study area.

Based on lithological characteristics, the Nourpul Formation is divided

into three members from bottom to top as the Purebensi Quartzite,

Amdanda Phyllite, and Labdi Khola Carbonate, respectively.

They have unique lithology and the boundaries between them are

clearly discernible in the field.

e) PUREBENSI QUARTZITE

The Dandagaon Phyllite is sharply followed up section by the Purebensi

Quartzite.

It is observed along the road section and continues westward to

Banspani.

This unit is dominated by green-grey to light grey, parallel and cross

laminated quartzite.

The formation is coarsed grained, medium to thick bedded with

abundant wave and current ripples.

Along the road section from Mugling to Narayangarh it is about 5m and

near to Loprang it is up to 45m. Laterally, some bands are continuous

and some bands pinch out at places.

The total thickness of Purebesi Quartzite is about 440m in road section.

It is sharply followed up section by a monotonous phyllite sequence of

the Amdanda Phyllite.

f) AMDANDA PHYLLITE

The Amdanda Phyllite represents the middle part of the Nourpul

Formation and is well exposed in the Amdanda village about 9 km

southwest of Mugling.

It consists of finely laminated, grey, psammatic and variegated phyllite.

Quartz veins are frequent and show the cross cutting relation with

laminae.

Total thickness of this this unit is about 450m and it passes transitionally

into Labdi Khola Carbonate.

g) LABDI KHOLA CARBONATE

The Labdi Khola Carbonate is well exposed along the Labdi Khola,

Mugling-Narayangarh road section at Jalbire and along the Trishuli River

at 9kmsouthwards from Mugling.

The member is the mixed lithology of dominantly carbonates with

subordinate amount of variegated gritty phyllite and metasandstone.

The sequence sharply passes into the Dhading Dolomite at the

southeastern part of the study area (at Jalbire).

The thickness of this unit is about 450m

h) DHADING DOLOMITE

Dhading Dolomite is exposed approximately 4km southeast of Jalbire.

It forms a small outlier in the ridge, west of Jalbire.

The formation consists of grey, medium to thick bedded, massive

dolomite with frequent partings of grey chloritic phyllite.

The laminae are from 1mm to 1 cm thick, continuous, parallel to sub

parallel, grey to dark grey in color.

Calcite veins of various generation, columnar stromatolite pointing right

side up and several leaching features, crustification on outcrops,

stalactites and stalagmites are observed in well developed in this unit.

Figure 3. Generalized Columnar Section of the Rocks of the Midland Group in the Muglin- Bandipur Area.

3.2.2.STRUCTURES

There are four E-W trending major folds in the area. The axial trace of

the Jalbire Syncline passes about 1km south of Jalbire. The core of the syncline

is occupied by the Dhading Dolomite. The fold plunges 7 degree to the ESE

with trend of 98 degrees. The Nourpul Formation is repeated along the road by

this fold. The axis of the Mugling Anticline passes from about 4km north of

Mugling. The anticline plunges to the 6 degrees with the trend of 260

degrees(WSW). The Aklang Syncline is an overturned fold with both of its limbs

dipping towards north. The axis of the fold passes from just north of the

Marsyangdi Hydropower station. The axis of the fold is trending WNW-ESE. The

Anbu anticline passes from north of Anbu Khaireni. This is also an overturned

syncline both of its limb dipping to the north.

3.2.3. SEDIMENTARY FEATURES

PRIMARY STRUCTURES

a) RIPPLE MARKS

Oscillationripple marks are observed in Purebesi Quartzite and

metasandstone of Nourpul Formation. Some linguoid ripple marks are also

observed on the sandy phyllite of the upper part of the Nourpul Formation.

Sharp crest of oscillation ripples was used for the younging direction of strata.

Figure 4. Ripple Marks

b) MUD CRACKS

Well preserved mud cracks are observed in the psammatic shales of the

Nourpul Formation. These structures indicate the sediment aerial exposure

from the shallow water. The convex surface of the mud crack wedge was used

for the younging direction.

c) STROMATOLITES

Columnar stromatolites are found in the massive beds of the Dhading

Dolomite. The convex part of the stromatolites indicates the younging

direction.

d) GRADED BEDDING

Gradded bedding is observed within the Bandipur Slate at the lower

reaches of Bandipur indicating normal stratigraphic position of the area. This

clearly indicates that the dolomite sequence of Bandipur area is younger than

the Bandipur Slate and is interrupted as the Dhading Dolomite.

Figure 5. Stromatolites

e) CROSS BEDDING

Well developed cross beddings are found in metasandstone beds of

Bandipur Slate. The cross beddings show the overturned beds which is due to

the locally folding of the rocks.

f) OTHER STRUCTURES

The area is highly stressed as indicated by numerous folded quartz veins,

boudinage structures and shear zones in addition to major folds and thrusts

Upper part of Nourpul formation and Benighat Slate consists of numerous

folded quartz, calcite and gypsum veins and boudinage structures.

Figure 6. Cross bedding

Figure 7. Angular Unconformity separating the Siwalik and the Lesser Himalaya

3.2.4. FOSSILS:-

Most of our study section has covered by lesser Himalayan successions. Fossils

are generally not common in lesser Himalayan rocks.

A perfect columnar stromatolite trace fossil of Precambrian has been found in

Dhading Dolomite rocks. But various vertebrate (Bone fossils) and plants fossils

has been found in siwalik sections.

4. METHODOLOGY AND MATERIALS:-

Different methods and practical works were done to fullfill the abovementioned

objectives of the study area. Different equipments and tools used during the

field work were Bruntun compass, Geological hammer, Measuring tap , Clip

board,Hand lens, Dill HCL, Altimeter , Power tape, Map holder , Tracing

papers, Graph papers and Topographical maps viz;

278403C Muglin

278403A Anbukhaireni

278402D Jugedi

Figure 8. Bone Fossils

278402B Bandipur

Topomap from Dumre to Besi-Sahar-Bhoteodhar road,

Geological map of Stocklin and bhattarai 1977,

Geological map of DMG of Muglin-jugedi section and

Geological map of Paudyal and Paudel (2013).

Compass traverse of the study area was made.The study of the rocks and other

different aspects like rock identification were performed in the field and the

contact between different formations of the study area were identified and

drawn in the map on the basis of lithological and petrological changes in the

field.

The fine grained rocks were studied with the help of hand lens while

calcwereous rocks

were distinguished with the help of dil. HCL. The attitude and thickness of the

beds were also measured .Other information like presence of fossils, geological

structure (fold, fault, ripple marks, lamina, cross-bedding etc were also

observed. These all information collected was simply filled in the maps. We

recognized fold in the field by the study of various geological properties such as

attitude of beds, older and younger beds, repetition of same formations. The

thrust fault can be detected if :

• Older rock overlied younger rock.

• Topography changes

• Breakage of river pattern

• Presence of fault gauge and breccias.

The attitude of beds ( strike, dip amount, dip direction ) were measured by

brunton compass in the field. The imaginary line formed by the intersection of

bedding plane and horizontal plane is called strike. The angle of inclination of a

bed is dip amount. It is always less than 90 degree. Similarly, the direction

which is perpendicular to the strike is dip direction. Anticline fold is a convex

up fold in which older rock lies in the core whereas syncline fold is a concave

up fold in which older rock lies outer part of the core or younger rock lies in the

core.

5. RESULTS:-

5.1. Geological structures:-

5.1.1. Folds:-

a) Jalbire Syncline: As we move northward from chaudakilo bazaar, beds are

dipping northward(i.e. towards stratigraphically upward). Initially beds were

found to be dipping steeply by 85◦ which goes on decreasing northward and

attains its minimum up to sub horizontal nearby Jalbire(fig1 below).Now beds

start dipping southward and amount of dipping gradually increasing

northward. Stereographic plot of these data gives its axis extending NW to SE.

Trend and plunge of axis was found to be 104◦ and 18 ◦.

b) Muglin Anticline:- South dipping trend(attitude,60/80/150) at about

1500m southward from muglin) of beds continues towards Muglin,

northward but again north dipping beds get started while going further

northward towards Abukhaireni area( attitude,31/30/295). Beds are near

vertical around Muglin area.

Figure 9. Core of Jalbire Syncline

c) Gorkha-kunchha Anticlinorium :-On the way towards Besisahar at

Batasedanda, near horizontal biotite grade schist was encountered.

Southern part of his site has south dipping beds with grade of

metamorphism increasing towards north and inclination increasing

gradually towards south. We observed north dipping higher grade

metamorphic rocks towards its northern side. Stereographic plot of these

data provides a fold with its trend and plunge of axis as 331/8 .

5.1.2. Thrusts:-

a) MBT: - We started our observation form jugedi. Firstly sedimentary

rocks of siwalik were observed. As we proceeded further

northward(stratigraphiclly upward), we encountered slightly

metamorphosed, more crystalline and having relatively high reflectance

rock dolomite. Here conspicuous break in metamorphism observed. A

index fossil of Precambrian i.e. columnar stromatolite was also observed

on the boulder of dolomite, which also indicated a sharp contrast in age.

Sharply truncated river course and sharp change in topography were

also observed.

Above results supports MBT.

b) Dewachuli Fault:-During our geological mapping we observed beds from

khor khola towards its dip direction(towards younging direction). Initially

stromatolitic, crystalline rock dolomite of Dhading Dolomite observed

which in turns followed by rocks of Nourpul Formation upsection. Here a

distinct break in stratigraphy was observed.

c) Lower MCT:- We conducted a geological observation form Abukhaireni

to Besisahar. While proceeding northward, progressively change in

grade of metamorphism from chlorite to garnet was observed. Schist

was highly undulated. At Besisahar area rock were in garnet zone and

were highly deformed forming asymmetrical budin, Z type

fold.anastomosing foliation etc. This zone imparted a higly sheared zone.

Figure 10. Z-type fold observed in Dandagaon Phyllite (N-of Besisahar) at garnet zone

d) 5.1.3. Bedding/ Foliation:- Most of the rocks in our study section were

foliated. Beddings were observed around subhimalaya zone towards

Jugedi area and dolomite beds in lesser Himalaya. Most of the foliation

in lesser Himalayan (metamorphic) rocks were found to be parallel to

beddings and bedding were indicated by lamination. Even the

granoblastic rock ‘quartzite’ was found to possess foliation defined by

partings of grey phyllite.

A special kind of foliation, anstomosing foliation, was discovered around

Besisahar area.

5.1.4. Lineation:- lineations were prominently observed in our study sections.

Mostly it was found abundantly on kuncha rock, phyllite, as a axis of

crenulation. An outstanding example of stretching lineation was found on the

bed of fagfog quartzite at chepleti khola. An archetype of mineral lineation was

observed in Ramadi Bazar. Pockets of chlorites oriented in one direction w as

noticed there.

5.2. METAMORPHISM

During geological mapping we took several routes. Our objective was to study

the metamorphism of the werea. We started our journey from Jugidi to Dumre

up to Besisahar section.

Around jugedi we encounter very low grade Benighat slate with less visible

chlorite mineral.

At Kuncha Formation , around Muglin, chlorite was seen clear and is continue

upto Abuekhaireni . Chlorite was found vesicular, braided, prismatic type.

a) EXCURSION FROM DUMRE TO BESISAHAR

Rocks were dipping towards north however moving towards the younger

directions .At dumre section, there found pelitic, pssimatic, phyllitic,

metasandstones and chlorite is so distinct. Number of chlorite bundle

suddenly increase while comparing to Muglin section moving towards

north.

Next section..Biotite isograde rock was observed about 300m from Batase

Danda towards Besisahar.

Further moving towards north at Bhoteodar we encounter the garnet

isograde.

Further Besisahar, garnet size increases, crenulation cleavage observed,

deformation increases, quartz buddin seen. Around the garnet there found

retrograde metamorphism of biotite rock which is also bounded by chlorite.

The inverse metamorphism observed in this section is due to the presence

of shear zone near the area (MCT).

Figure 11. Schematic Cross-Section along Dumre-Besisahar Road

b) EXCURSION FROM DUMRI TO BANDIPUR

In this section we encounter dolomite rock.Nourpul formation is clearly

observed.Clear metamorphic mineral were observed in this section

Figure 12. Shear Zone observed along the Dumre-Bandipur Section

5.3. MAGMATISM OF STUDY AREA

Evidence of paleomagmatism were recorded in the form of metabasic rock

unit associated different rock in the study area. Study area comprises

metabasic rock mainly in Kunchha Formation, Fagfog Formation and Nourpul

Formation. These metabasic rocks was mainly green schist and amphibolites.

Lineation and foliation was well developed in such metabasic rocks in this area.

Green schist consists mainly of acicular mineral actinolite and chlorite and

amphibolites consist of mainly amphibole minerals with accessory quartz and

feldspar mineral.

5.3.1. Kunchha metabasic rocks

These rocks was exposed along the Muglin-Narayanghad road section on the

way to Muglin on the uphill section of road which was nearly 500 meter far

from the confluence of Marsyandhi and Trishuli River.

5.3.2. Nourpul metabasic Rocks

Metabasic rocks of Nourpul formation was well exposed in the purebesi

Quartzite member along the road section and lower part of Labdikhola

carbonate member along the Labdikhola approximately 200m upward from

the junction of Labdikhola and seti river.

6. DISCUSSION:-

6.1. DISCUSSION ON FOLD:-

Various folds were observed in our study section. A synclinal fold named jalbire

syncline was observed as we proceeded northward from chauda kilo towards

muglin. Beds were initially north dipping with high dip amount. Values of dip

were kept on decreasing towards upsection and became subhorizontal at its

core near jalbire. Beds were then dipping south while proceeding further

northward from jalbire.

Similarly a corresponding antilcline was observed in between Muglin and

Dumre. South dipping limb of jalbire syncline was common for both jalbire and

mugline anticline.

A regional scale gorkha-kunchha anticlinrium was observed along the way

towards besisashar with its core at………………………. Beds were south dipping

and are steep initially, became gentle and finally subhorizontal at its core.

Besides, beds were observed dipping towards northward while moving further

northward upto Besisahar.

6.2. DISCUSSION ON THRUSTS/FAULTS:-

During the field observation form jugedi to muglin secion, initially the middle

siwalik were observed with salt and pepper appearance. Observing the

lithological setting towarda north (stratigaphically upsection), nearby kalikhola,

sharp change in lithology was observed. Presence of precambrian stromatolite

on dolomite indicate the older rock laying over younger siwalik rock, which

directly indicates the presence of MBT in the area. Here, sharply truncated

river course and sharp change in topography with conspicuous contrast in

vegetation strongly supports the presence of MBT. The MBT zone is not seen

there because of coverage by boulders.

While proceeding further towards north, older sequence of Nourpol Formation

was encountered overlaying the youger Dhading Dolomite, which again

indicate the presence of thrust named Dewachuli Thrust.

Also, the local thrust fault was observed along the road towards Bsndipur

Bazar from Dumre, where presence of older Nourpul phyllite was observed

over relatively younger Dhading Dolomite towards stratigraphically up section.

Black coloured coarsed fault gauge was observed (fig. below) on the section

uphill side, which also supports the presence of a shear zone.

Along the way towards Besisahar, initially cholorite grade rocks were observed

which then followed by biotite and garnet grade rocks respectively towards

northward at Bhotewodar area. Similarly, grade of metamorphism kept on

increasing towards besisahar, where highly sheared garnetifeorous rocks were

observed. Which pointed out that, we were approaching towards the lower

boundary of lower MCT zone. Discovery of Z-type folds, assymetrical budins

and anastomosing foliation (fig needed) further supports the presence of

Lower MCT.

6.3. DISCUSSION IN METAMORPHISM

Sothern part in metamorphism found in that section was metamorphism from

older to younger which can clearly result there is normal metamorphism

6.3.1. DUMRE TO BESISAHAR

Dumre to Besisahar towards younger direction metamorphism grade was

increased this was inverted metamorphism. Crenulation cleavage , folding ,

deformation with low grade rock were found in this section which show there

is inverted metamorphism. Muglin area is found chlorite zone. Lubdi khola

was encountered chlorite zone at sharp turning point 5oom far from lubdi

khola towards northern part along the highway.

7. CONCLUSION:-

Geological field work was carried out in the siwalik and lesser Himalaya of

Ghumaune-Mugling-Dumre-Besisahar section of central Nepal. The study area

comprises of sedimentary and low grade metamorphic rocks of Siwalik and

Nuwakot Group,Nawakot complex of lesser Himalaya respectively towards the

North. Mapping was done on the basis of previous work carried out by K.R

Paudyal and L.P Paudel (2011).

In the lower part i.e in Jugedi-Muglin section the boundary between Siwalik

and the lesser himalaya with angular unconformity and each unit of lesser

himalaya with different rock unit and structure( Jalbire Syncline;MBT)was

observed and mapped. In middle section i.e Muglin-Bandipur section the major

structure Gorkha-Kunchha anticlonorium with different rock unit was observed

and mapped. In the upper section i.e Dumre- Besisahar section, the schematic

cross section showing different metamorphic zone with different rock unit was

drawn showing inverted metamorphism.

Rocks form of six lithological units namely; Benighat Slate, Dhading Dolomite,

Nourpul Formation with its basal member Purebensi Quartzite, Dandagaon

Phyllite, Fagfog Quartzite and Kunchha Formation belonging to the rocks of the

Midland Group of the Lesser Himalaya were distinguished and separated by

major thrusts zone namely MBT(Main Boundary Thrust) in the south and

MCT(Main Central Thrust) in the North of the study area.

On the basis of observation of primary structures like bedding plane,

stromatolite, ripple mark and other structures and successive rock unit,the

general stratigraphic column for the overall area was made and this indicates

the ongoing metamorphism in low grade metamorphic terrain i.e. study area.

Different orders of river terrace deposit in the study area indicate the

continuous upliftment of that area.

8. REFERENCES:-

i. Paudyal,K.R. and Paudel, L.P.,2011. Re-interpretation of the stratigraphy

of the Nawakot Complex in the Mugling area between Dasdhunga and

Ghumaune, Central Nepal.

ii. Paudyal, K.R., 2012. Depositional environment of the Lesser Himalayan

rocks in the Muglin- Bandipur area, central Nepal.

iii. Billings,M.P , (2010). Structural Geology, 3rd Edition.