Báo cáo thực địa Hòa Bình

They are: Cam Thuy formation P3ct, Vien Nam formation T1 vn, Co Noi formation T1 cn,Dong Giao formation T2a dg, Song Boi formation T23 sb ,Suoi Bang formation T3n-r sb, Quaternary for

Contents

ABSTRACT 3

I Introduction 4

1.1 Geographical position 4

1.2 Natural geographical features 5

1.3 Geologic conditions 6

1.4 Climate characteristics 7

1.5 Socio-economic characteristic 8

1.5.1 Population characteristic 8

Table 1: Hoa Binh’s administrative divisions, population and density, 2005 9

1.5.2 Economy 9

1.6 Outline of report 10

II Methodology 10

2.1 Methodology in the field 10

2.1.1 Objectives 10

2.1.2 Obtained results: 10

2.2 Methodology in the laboratory 12

III Stratigraphy and Rock Units 14

3.1 Stratigraphy 14

3.1.1 Cam Thuy formation (P3ct) 15

3.1.2 Vien Nam formation (T1 vn) 16

3.1.3 Co Noi formation (T1 cn) 17

3.1.4 Dong Giao formation (T2a dg) 18

3.1.5 Song Boi formation (T2-3 sb) 19

3.1.6 Suoi Bang formation (T3n-r sb) 20

3.1.7 Quaternary sediments 22

3.2 Sedimentary units 22

3.2.1 Tuff originated sediment of Co Noi formation.(T1cn) 22

3.2.2: Terrigene sediment of Song Boi formation(T2-3sb) 23

3.2.3 Coal deposit with sandstone and siltstone in Suoi Bang formation(T3n-r sb) 23 3.3 Igneous units 26

3.3.1 Cam Thuy formation (P3ct) 26

3.3.2 Vien Nam formation 27

3.3.3 Ba Vi complex (δμT1bv) 28

3.3.4 Phia Bioc complex (γaT3n pb) 29

IV Tectonic characteristics 29

4.1 Historical tectonic units 29

4.1.1 Lower tectonic stage: rift structural complex (P3 - T3) 30

4.1.2 Middle tectonic stage(T3n-r sb) 31

4.1.4 Upper tectonic stage (Q) 32

4.2 Morpholotectonic forms 32

4.2.1 Kim Boi uplifted block 32

4.2.2 Ha Bi anticlinorium 33

4.2.3 Song Boi graben 34

4.3 Tectonic faults 34

4.3.1 The Northwest - southeast fault system 34

4.3.2 The Northeast - Southwest fault system 35

4.4 Ductile structures 36

V Geological History 38

5 1 Pre-Cenozoic period 38

5.2 Cenozoic period 39

VI: Mineral resources 39

6.1 Metallic Mineral 39

6.2 Non-metallic Minerals 40

6.3 Building Materials 40

6.4 Mineral Water 41VII: Conclusions 42VIII: REFERENCES: 42

ABSTRACT

During the short time, from July,13th to July18th 2013, K55 International Geology class of Hanoi University of Science had taken part in a field trip in Kim Boi district , Hoa Binh province This field trip is a chance for all students who studied Geology to improve and contact knowledge by researching geological phenomenon in the field trip

As well as, we were learnt how to use the necessary geologist tools: topographic map and compass and directly measure data and collect samples

The object of the field trip is help student apply knowledge learned on the subject” Structural Geology and Geological mapping” to review and evaluate the expression of them in practice Through the field trip, students can study clearly the characteristic distribution of topography, vegetation, and establishing the stratigraphic sequence, dating formations, recognizing structures, finding ore minerals in the study area Besides that due to the field trip observations and measurements data in the directly way, as well as,

to collect hand specimens to analysis After the expose point, students located in the filed map, collected information, samples, geophysical survey and measured data to write

in the fieldtrip notebook

Particularly, in the field trip , we practiced to survey 6 field itineraries crossing all the geological formations, from the oldest to youngest and all the types and elements of the region structure , which includes: Lang Chanh itinerary, Lang Noi itinerary, Kim Tien itinerary, Kim Binh-Kim Boi itinerary, Lang Vo itinerary Moreover, we went through 7 stratigraphical units, from oldest to youngest in the Kim Boi area They are: Cam Thuy formation (P3ct), Vien Nam formation (T1 vn), Co Noi formation (T1 cn),Dong Giao

formation (T2a dg), Song Boi formation (T23 sb) ,Suoi Bang formation (T3n-r sb),

Quaternary formations apQ Besides, we need to investigate on the stratigraphical units in the region and investigate on all the geological boundaries in Kim Boi region, as well as researching Kim Boi mineral resources

This is a significantly good chance for students of Geology faculty to study and research in the field as a first step On this occasion, we would like to sincerely thank

faculty of Geology and Hanoi University of Science for organizing this course and giving

us the great support during these days Last but not least, we would love to give special gratitude to our advisors, Prof Nguyen Van Vuong, Dr Luong Thi Thu Hoai and Dr Nguyen Thi Minh Thuyet for their guidance and advises who helped us endless to accomplish the successful course

I Introduction

1.1 Geographical position

On a map of Vietnam, Hoa Binh is a mountainous province, which borders with the Red River Delta and many roads, waterways where links to the provinces of Phu Tho,

Ha Tay, Ha Nam, Ninh Binh, Hoa Binh and is the gateway of the Northwest area and 76

km far from Hanoi as well Hoa Binh province has 10 districts: Da Bac, Mai Chau, Tan Lac, Lac Son, Kim Boi, Luong Son, Lac Thuy, Yen Thuy, Ky Son and Hoa Binh town with 214 communes In terms of geographic location, Hoa Binh is the intermediate buffer zone between a northern delta area and one side is the high mountains, dense forests of the northwest, through traffic is via Highway 6 (the road) and River The majority (waterways) in the north Peace bordering the capital Hanoi and have important positions

in the defense strategy of the region and nation This is also known for hydropower plants which have been built and gone into effective use since 1979, with a capacity of 8.16 billion KWh and the dam that is 128m in height

Kim Boi is a mountainous district of Hoa Binh province with geographic coordinates:

20 ˚ 30 'to 20 ˚ 45' North latitude

105 ˚ 30 'to 105 ˚ 37' East longitude

The total area of the district is 180 km ² , the center of the district is the Bo town, 80km southwest far from Hanoi where was chosen as place to train the courses Geological structure and mapping geology This area has favorable natural, economic, social, human conditions and as well as being an area to ensure the requirements of outdoor practice of this subject It borders with Ha Tay province to the east, Luong Son district to the north, Ky Son and Hoa Binh town to the west, Lac Son, Yen Thuy and Lac Thuy districts to the south The district includes 27 communes, in which 3 communes are

in the exploring itinerary: Nam Thuong, Kim Binh and Kim Tien Kim Boi is located along the banks of Boi river, inter-district road and 12B high way

Figure1 : The location of Kim Boi district, Hoa Binh province

1.2 Natural geographical features

Kim Boi is the mountainous which terrain is separated sharply, mostly oriented to the northwest-southeast According to the morphological and structural characteristics, terrain can be divided into the following form:

- High mountain terrain: with an average elevation of 600-800m that distribute mainly in the Southwest, the terrain is major block foundation and the main rock is granite There are some high mountain peaks with the elevation of 814m, 784 m and 611 m

- Average mountains and hills: mainly develop on carbonate rocks, which belongs to Dong Giao formation (T2a dg), distributed along the left bank of Boi river There are many steep slopes with average elevation of 400-600 m, where karst topography develops This terrain distributes mainly in the east of the Kim Boi intrusive mass, like Roc Da peak (494m)

- Low hills: this type of terrain develops in the extrusive rock of Vien Nam formation ( T1 vn) and the tuff terrigenous rocks of Co Noi formation(T1 cn) This terrain distributes mainly in the south and north of the research area and has gentle slopes which covered with vegetation

- Valley topography: This terrain type is mainly distributed along the Boi River in northwest-southeast direction, producing the Valley of Boi River This has flat surface and divided into different high levels, with 30 meters in wide, slightly inclined toward the river, which is the rice field and region where people live

+ Level I terrace: distributes along the river banks, closed to the alluvial ground and near the limestone mountain The height is about 4-6 m above the river, narrow width, however, in some places, the width of the terrace can be up to 30 meters

+ Level II terrace: elevation of about 10-15 m above the river, between level I and level II terrace; is the vegetable field and villages

+ Level III terrace is the oldest terrace of Boi river valley with more than 15m in height The left part of level III terrace is very rare due to erosion It only exists as relic hill, bowl hill

On soil: Kim Boi’s soil is quite suitable for a wide variety of crops: from industrial plants, ration plants to fruit plants Because of Topography and climate should Hoa Binh land divided into two obvious parts: alpine average, including red wine soil feralit ebony content 6-7%, due to high humidity, the temperature a low, this area is very favorable for forestry development Hills and low mountains, including land feralit red wine scholar and regions, including the soil accounted for 45-80% Most areas along rivers and streams every year due to another by a thick coating sa should be very favorable for growing rice,

in the blood

1.3 Geologic conditions

In the study area, there is mainly the presence of sedimentary formation and eruption aged from Late Permian to Quaternary Cam Thuy Formation (P3 ct) is mainly the forming eruption of magma differentiation in ultramafic, intermediate to acid Formation is relatively wide distributed in different areas The formation of the Vien Nam Formation (P3-T1 VN) also exposes a narrow band that border around the the northern edge of Kim Boi block Eruptions of this formation is continuous differentiation from mafic, intermediate to acid Dong Giao Formation contains mainly limestone alternating sandwiched layers or clay lenses and calcareous siltstone.The basement layers of Boi River Formation (T2-3 sb) covered unconformably up Anisi limestone of Dong Giao Formation Boi River Formation consists of sand granules, siltstones that contain sandwiched layers of shale and black coal- shale Suoi Bang Formation (T3n-r sb) consists of siltstone, dark gray claystone in thin bedding Alternating between the layers

are lenticular coal seams Cover a large area of research is the Quaternary sediments In addition to the sedimentary formation and eruption above, intrusive activities act strong as well Products of these activities create intrusive complexes such as Ba Vi (dP3 bv) and Phia Bioc (gaT3n pb).In tectonic characteristics, the study area lies entirely in the Northwest fold system of Indosinian stage of the SouthEast Da River structure This structure is composed of complex system - tectonic rift (P3-T2-3) and complex formation orogeny architecture (T3 nr)

mm of rainfall annually The mean humidity is 83%

Hoa Binh’s climate is divided into two distinctive seasons: the wet and the dry.The wet season lasts from May to the end of October Average rainfall in the rainy season is estimated at 1,700 – 2,500 mm, accounting for over 90% of the yearly rainfall total The high mountainous area of Mai Chau and plains alone, the wet season sets in 15

to 20 days late Especially, in the areas of Kim Boi, Chi Ne and Yen Thuy, the combined seasonal and yearly rainfall is larger To contrary, the least seasonal and yearly rainfall is recorded for the Mai Chau area

The dry season begins in November and ends in April, with annual average rainfall

of 150 to 250 mm, representing merely 10% of the yearly rainfall total In the peak months of the winter (December, January and February), total monthly rainfall is reportedly roughly 30 mm

Overall, Hoa Binh’s climate, which is cool all year round, combined with a large number of high mountains and charming natural scenery, make Hoa Binh an ideal place

to rest and visit

Besides, water courses (rivers and streams) are well distributed across the province, encompassing large rivers, namely Da River, Boi River, Buoi River and Bui River

1.5 Socio-economic characteristic

1.5.1 Population characteristic

Hoa Binh has a population by far has more than 800,000, of which working-age population totals 523,400, accounting for 64% It is estimated that 14.5 thousand employments are generated per year, exceeding an annual target of 13,000 jobs The province’s economy is seen to enjoy a year-on year growth of 8% during the 2000 - 2005 period In particular, the industrial and construction sector had an annual expansion of 16%, with an 18.5% bounce in industry and handicraft and a 12% rise in construction Meanwhile, the agriculture, forestry and fisheries sector surged by 4.9% and the service sector accelerated by 8.2% Additionally, several socio-economic targets were met at high levels with gradual improvements in people’s lives Positive changes were seen in the province’s economic structure with an increase in the shares of the industry, construction and service sectors New products have emerged as a result of the application of more advanced technologies in industry and service Some improvements have been recorded for changing the structure of agriculture

Hoa Binh is home to multi-ethnicities, including six main groups: Kinh (accounting for 27.7%), Muong (63.3%), Thai (3.99%), Tay (2.71%), Dao (1.73%), H’Mong and others (0.57%) The province had a population density of 170 people per sq

km in 2006 Its population is unevenly distributed, with roughly 80 % living in lowlands and in the city Per capita income in Hoa Binh is estimated at VND 4.3 million, higher than a target of VND 4 million

(Source: Hoa Binh Province’s Socio-Economic Development Plan for the 2006 – 2010 period)

The following table gives data on Hoa Binh’s administrative divisions, population and density in 2005:

Table 1: Hoa Binh’s administrative divisions, population and density, 2005

No City and districts No of

- Agriculture and forestry are the main source of income

- Industry: there were very few plants, factories and industrial production in the past With the development of industrialization, however, there are now small and medium-scale factories in the areas such as cement, brick, sugar, building material factories

- Commercial and services: With the participation of many economic sectors, commercial and services are developing rapidly Kim Boi’s mineral water is a famous

trademark of the area However, the facilities for tourism and resort is still not good enough to satisfy national and foreign customers

In short, agricultural production in Kim Boi is not specialized and there is no term development plan as well Deforestation is also a serious problem in here

long-Particularly, Kim Boi has potential in gold mining and building material , but it is not developed in the area The coal mine in the area is small and used for local needs

1.6 Outline of report

We have fulfilled the final report which includes:

1) Introduction to natural, physic-economical conditions

2) Methodology

3) Stratigraphy and rock units

4) Tectonics and geological structures

5) History of geological evolution

 The equipment was used to collect data that includes :area photographs, topographic maps, geological map(1:50000 scale) and soil surveys, as well as types of equipment survey compass, altimeter, GPS device, geological hammer…

2.1.2 Obtained results:

 During the short time(July, 13th – July 18th 2013) we practiced to survey 6 field itineraries crossing all the geological formations, from the oldest to youngest and all the types and elements of the region structure , which includes:

1 Lang Chanh itinerary

2 Lang Noi itinerary

3 Kim Tien itinerary

4 Kim Binh-Kim Boi itinerary

5 Lang Vo itinerary

6 Cau Lang- Go Che itinerary

Table 2: The location of the expose points

2 KB2 Kim Tien 320m far from KB1

3 KB3 Cau Lang Under Cau Lang- rightside of Boi river

compared to the flow direction

4 KB4 Go Che From KB3, go straight, turn left,

-Derive from Xom Song following the southwest

9 KB9 Kim Binh-Kim

Bôi

-Go through Kim Binh and kim Boi commune following northwest- southeast along the highway from Bo town to Cuoi

Ha

 The collection hand specimens

Practically, the hand specimens were collected in fresh condition along the rivers, stream and spring which maintain all features and typical characteristic of this hand specimens

The table following show some data: nation of samples, where we collected those hand specimen and several generally describe about those hand specimens

Table3 : TheStatistic table of samples

No Notation

of

samples

Location of samples

General description

1 KB1 Kim Tien Basalts – mafic extrusive rock, green gray color

2 KB2 Kim Tien Granite extrusive rock, felsic intrusive rock, bright

gray, small to intermediate in grain size

3 KB3 Cau Lang Limestone

4 KB6 Lang Noi Limestone with hydrothermal zone

5 KB8-1 Lang Chanh Granite bright color, intermediate in grain size

6 KB8-2 Lang Chanh 1km far from where collected KB8-1 samples,

Limestone with original hydrothermal

7 Kb9-2 Kim Binh Rock was related to Vien Nam formation

2.2 Methodology in the laboratory

We practiced petrology analysis under micro optical to observe and define the composition of samples and their optical properties All in all, the hand specimen was secondary deformation process

Hand specimen: KB1:

Figure 2: Sample KB1Under 2 nicol

(interferential color)

Figure3:sampleKB1 Under 1 nicol

(absorptive color)

The hand specimen: had partly secondary deformation

plagioclase was chloritization

The compositions: quartz, feldspar K, plagioclase, biotite no hornblende

The samples were strongly secondary deformation, sericite and chloritization

 Biotite Granite

 Interference colors in thin section are high order white (pearly luster)

 Twin lamellae may show as bands of pastel pink or green, and zones of overlap of inclined twin lamellae may not go entirely extinct with stage rotation

 No orientation unaltered

 Limestone is cut by hydrothermal lode horizontally and vertically

III Stratigraphy and Rock Units

3.1 Stratigraphy

There are 7 stratigraphical units , from oldest to youngest, from Permian to Quaternary in Kim Boi area The following formations can be found in this area:

1 Cam Thuy formation ( P3ct)

2 Vien Nam formation (T1 vn)

3 Co Noi formation (T1 cn)

4 Dong Giao formation (T2a dg)

5 Song Boi formation (T23 sb)

6 Suoi Bang formation (T3n-r sb)

7 Quaternary formations apQ

3.1.1 Cam Thuy formation (P 3ct)

Cam Thuy formation is distributed associated with Yen Duyet formation The sections of the formation are widely distributed in the southeast of Ma river anticlinorium

in Thanh Hoa, Ninh Binh, Hoa Binh, Son La and Lao Cai

According to Phan Cu Tien et al (1977), the section is divided into 2 parts:

+ Lower part: greenish dark gray porphyritic basalt, fine - grained, uneven amygdaloidal and spherical structure, containing tuff, tuff agglomerate, 300m thick

+ Upper part: porphyritic basalt containing tuff, tuff sandstone and siltstone, 150 - 200 m thick

Cam Thuy formation unconformable overlies limestone of Da Mai formation and conformably underlies Yen Duyet formation

In the study area, Cam Thuy formation exposed around the east border of Kim Boi intrusive block and is metamorphosed by this The component of Cam Thuy formation includes: diabase, amygdaloidal diabase, porphyritic basalt, andesite-basalt In the Kim Boi area, basalt with green gray in color and block structure and intermediate grain size

in texture belong to in Song commune, Chanh village and Kim Tien

Figure7: Basalt extrusive rock belong to

Cam Thuy formation (P3ct) in Kim Tien

Figure8: Basalt of Cam Thuy formation in

Chanh village

In Kim Tien outcrop, observation the contact between granite ( Phiabioc complex (T3pb)) and basalt ( Cam Thuy formation (P3ct)), rock in this outcrop is keratinization and Kaolini ation of feldspar

In general, the cross section of Cam Thuy formation is principally the extrusive rock

Figure9: The outcrop observe the boundary granite ( Phiabioc complex (T3pb)) and

basalt ( Cam Thuy formation (P3ct))

3.1.2 Vien Nam formation (T1 vn)

Vien Nam formation has a wide distribution from Vien Nam - Ba Vi to Kim Boi,

to the northwest, in Van Yen, Nam Ta Khoa, Nam So and south of Ha Tay, Ninh Son coal mine

The typical section described by Ho Trong Ty included 4 members:

Member 1: basalt, greenish dark gray porphyritic basalt and their tuff Basalt has amygdaloidal structure containing chlorite, calcite and quartz, 250 m thick

Member 2: porphyritic basalt and greenish light gray tuff agglomerate, 150 - 200 m thick Tuff in agglomerate, which has different size, cemented together by fine-grained tuff Member 3: olivine basalt, porphyritic basalt interbeds green, greenish gray tuff with uneven amygdaloidal structure, 150m thick

Member 4: greenish dark gray basalt interbed of dark gray, thick-layered tuff bearing sandstone, 200m thick

The total thickness of the formation is about 770 - 800 m

In the study area, Vien Nam formation exposed in a wide range in the north - southeast direction (Roc village - Ha Bi - Lot village - Kim Truy) and a small area in the northeast (Ba Ra mountain) According to the surveys and the results obtained of geologists group (307) , we is divided into 2 phases:

Phase 1: dacite, rhyodacite, felsite, porphyritic trachyte, volcanic materials

Phase 2: dense, massive basalt, amygdaloidal basalt, porphyritic basalt, and andesite

The rocks of Vien Nam formation is strongly weathered and well covered by vegetation, so it is very rare to observe fresh rocks of Vien Nam formation in the study area

3.1.3 Co Noi formation (T1 cn)

Co Noi formation is distributed very widely into discontinuous band in northwest plateau Lan Nhi Thang, Ta Phin, Son La, Moc Chau to Hoa Binh, Vu Ban In the study area, Co Noi formation is distributed into narrow band along the Northwest - Southeast direction

The formation is divided into 3subformations:

Lower subformation : conglomerate, sandstone, tuff sandstone, violet thick-bedded originated sediments They are distributed in narrow bands unconformable overlies Vien Nam formation, about 120-150m thick

tuff-Middle subformation 2: : marl, thin-bedded marly limestone, sometimes vermicular structure, interbeds of clay shale , distribute into parallel bands with member 1 and separated from member 1 by clay limestone layer lithological composition includes thin layered calcareous clay, shale bearing sandstone, 100m thick

Upper subformation 3: light-violet siltstone, sandstone, sometimes gray, dark gray, bedded, distribute along the sediments of member 2 and distinguish from them by layers

thick-of light purple sandstone thickness thick-of about 100m

The total thickness of the formation is about 320 - 350 m

Figure 10: violet sandsone, siltstones contains tuff of Co Noi formation ( T1 cn) in a

wall of the hill

Co Noi formation unconformably overlies Vien Nam formation and has transfer relationship with Dong Giao limestone

3.1.4 Dong Giao formation (T2a dg)

Dong Giao formation is distributed into wide band in Lan Nhi Thang plateau, in Son La, Moc Chau to Hoa Binh, Kim Boi, Cuc Phuong and Tam Diep In the studying area, Dong Giao formation distributed into a wide range running along northwest - southeast direction and was moved by 2 strike-slip faults (northeast - southwest orientation) and can be divided into 3 parts:

+ The lower part consists of dark gray limestone, layered thin to very thin, usually on the surface of clay minerals, gray gold sericite , gold, medium thickness layered silica limestone This part conformably overlies Co Noi formation, 400 thick

+ The middle part is mainly composed of thick layers of limestone, sometimes with gray blocks, dark gray, gray and white, about 300 meters thick

+ The upper part contains light gray uniformed limestone blocks, about 150 m thick

The total thickness of Dong Giao formation is about 850m

All in all, Dong Giao formation is a homogenous stratigraphic with almost pure limestone in different regions, cross section only different by color, the layering degree

of rock and sandwiched level of clay or siltstone, silica are not significantly different from each other

In the study area,Dong giao limestone was exposed in Cau Lang itinerary and Noi Village Dong Giao limestone conformably overlies Co Noi formation

Figure 11: Limestone in Noi Village belong

to Dong Giao Formation

Figure 12: A tectonic breccia zone is formed by breaking and cementing of original limestone (Dong Giao Formation

T2)

3.1.5 Song Boi formation (T2-3 sb)

Song Boi formation is distributed mainly along Song Boi valley, Luong Son (Hoa Binh) and Chi Ne area This formation is divided into 2 subformations:

Upper subformation: clay shale, banded calcareous shale interbeds of sandstone, siltstone Lower subformation: banded sandstone, siltstone, black-color clay shale

In the studying area, it exposed only in a small area in the northwest

It consists of sandstone, gray banded siltstone, light gray, gray shale, black coal bearing claystone The thickness of the formation is about 200 - 300m In Noi village itinerary, this expose point cut-over the limestone belong Dong Giao formation (T2adg) and terrigenous sediment of Song Boi Formation (T2l-T3s sb) Song Boi formation unconfomably overlies Dong Giao formation

Figure13: the terrigenous sediment of Song Boi Formation (T2l-T3s sb) in Noi Village

3.1.6 Suoi Bang formation (T3n-r sb)

The typical cross section of the formation is selected in Bang stream area, along Lao stream and can be divided into 3 parts:

+ The lower part : siltstone, shale dark gray, thin layering, sometimes alternating layers of gray limestone, clay, small sandstone layers interbed bright over limestone, 210m thick + The middle part: light gray sandstone, under are quartz sandstone medium to coarse grained size, medium layered, containing mica flakes alternating dark gray siltstone, on which there is light gray poly-mineral sandstone, medium grain, alternating some layers

of sandstone containing pieces of plants and the large mica flakes on the surface layer, then sandstone containing conglomerate, conglomerate, gravel, 420 m thick

+ The upper part : gray siltstone, dark gray, layered from thin to medium, usually containing plant debris mixed gray sandstone, granule to medium, medium layered, dark gray coal bearing claystone, and several coal seams, at the top the sand is essential, 270m thick

The total thickness of section is about 940m Suoi Bang formation unconformable overlies other formation with different ages

In the study area, the Suoi Bang formation only expose a narrow and short band in the southwest corner- Lang Vo outcrop The typical component here is gray siltstone,

mixed gray sandstones , with granule to medium in grain size, layered from thin to medium Beside, dark gray coal bearing clays tone, and several coal seams

Figure14: siltstone mixed sandstone , the

layer from thin to medium of Suoi Bang

formation in Vo village

Figure 15: Sandstones, siltstones bearing coal of Suoi Bang formation in Vo village

Figure16 : Coal seams associated siltstone and sandstone in Lang Vo itinerary