Báo cáo thực địa Hòa Bình

REPORT ON EXPOSING IN KIM BOI DISTRICT , HOA BINH PROVINCE
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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
 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 (P
3
ct) 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
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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 (
1
bv) 28

3
n pb) 29
IV. Tectonic characteristics 29
4.1. Historical tectonic units 29
4.1.1 Lower tectonic stage: rift structural complex (P
3

- T
3
) 30
4.1.2 Middle tectonic stage(T
3
n-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
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6.4 Mineral Water 41
VII: Conclusions 42
VIII: 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.

Structural Geology and Geological  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 (P
3
ct), Vien Nam formation (T
1
vn), Co Noi formation (T

1
cn),Dong Giao
formation (T
2a
dg), Song Boi formation (T
32
sb) ,Suoi Bang formation (T
3
n-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
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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:


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.
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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.
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- 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: 
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
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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).

1.4 Climate characteristics
Hoa Binh Province lies in the tropical monsoon climate zone. It is cold in the
winter with less rain and hot with much rain in the summer. The mean temperature is over
23
0
C. The highest temperature is recorded in July at average of 27-29
0
C, while the lowest
temperature is reported in January in the range of 15.5 - 16.5
0
C. It receives about 1,800
mm of rainfall annually. The mean humidity is 83%.


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.
ombined 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.
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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

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
            
province
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%),
f 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)







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
and density in 2005:
Table 1: Hoa Binh’s administrative divisions, population and density, 2005
No.
City and districts
No. of
communes
No. of wards and
towns
Land area (Sq.
km)
Average
population (People)
1
Hoa Binh City
6
8
133
83,607
2
Da Bac District
20
1
820
51,800
3
Mai Chau District

21
1
519
49,670
4
Ky Son District
9
1
202
35,307
5
Luong Son District
17
1
375
82,014
6
Cao Phong District
12
1
254
41,014
7
Kim Boi District
35
2
681
142,370
8
Tan Lac District

23
1
523
78,791
9
Lac Son District
28
1
580
132,384
10
Lac Thuy District
12
1
293
50,140
11
Yen Thuy District
12
1
282
63,033
Total
195
19
4,662
810.130
(Source: Hoa Binh Department of Statistics)
1.5.2 Economy
People live mainly by agriculture. The main crops are corn, potatoes, watermelon

fruit, sugar, grapefruit. Some specialities in this area are bamboo, taro, bamboo-rice,
wine.
- 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,
            
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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 long-
term development plan as well. Deforestation is also a serious problem in here.
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
6) Mineral resources

II. Methodology
2.1 Methodology in the field.
2.1.1 Objectives
 Observations and measurements several typical features in geology in the area
survey, to clearly understand of the knowledge on the subject Structural Geology,
Tectonics and Geological Mapping
 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, 13
th
 July 18
th
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
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4. Kim Binh-Kim Boi itinerary
5. Lang Vo itinerary

6. Cau Lang- Go Che itinerary

Table 2: The location of the expose points
No
The expose
point
Location
Coordination
1
KB1
Kim Tien
20
105
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,
continue go about 300m.

5
KB5

Lang Noi
Derive from Lang Noi, go through Xom
Khoai.

6
KB6
Lang Noi
Continue go to the inside, 300m far from
KB5

7
KB7
Lang Vo
-5km far from Kim Truy to Lang Vo coal
mine.
- Outcrop lies on the left hand side on the
way to coal mine.

8
KB8
Lang Chanh
-In the northwest of the field area, extend
2km north-notheast, south-southwest,
from 12B highway to Chanh village.
-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.
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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 : The Statistic 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)
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The results:
Name: basalt- extrusive rock, small and fine grain size by nake eyes
Optical features:
ferrous minerals are predominate, but it still has light-colored minerals. porphyritic
texture, random arrangement elements. texture: Aphanitic (fine-grained)
The Compositions: plagioclase, amphibole and pyroxene , no quartz . Amphibole,
pyroxene alter to epidote and chlorite
The hand specimen: had partly secondary deformation.
plagioclase was chloritization
Hand specimen: KB2

Figure4:KB2 Under 1 nicol
Figure 5: Sample KB2 Under 2 nicol

The results:
Name: granite- felsic intrusive rock- bright gray, small to medium in grain size-
observation by nake-eyes
The compositions: quartz, feldspar K, plagioclase, biotite no hornblende
The samples were strongly secondary deformation, sericite and chloritization.
 Biotite Granite


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Hand specimen: KB6

Figure 6: KB6 under 2nicol

The results:
Name: limestone in Lang Noi itinerary
Optical features:
 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 ( P
3
ct)
2. Vien Nam formation (T
1
vn)
3. Co Noi formation (T
1
cn)
4. Dong Giao formation (T
2a
dg)
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5. Song Boi formation (T
32
sb)
6. Suoi Bang formation (T

3
n-r sb)
7. Quaternary formations apQ
3.1.1 Cam Thuy formation (P
3
ct)
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

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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  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.
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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 tuff-
originated sediments They are distributed in narrow bands unconformable overlies Vien
Nam formation, about 120-150m thick.
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, thick-
bedded, distribute along the sediments of member 2 and distinguish from them by layers

of light purple sandstone. thickness of about 100m.
The total thickness of the formation is about 320 - 350 m
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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

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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.
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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,

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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
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3.1.7 Quaternary sediments
The Quaternary sediments in the practice area are mostly unconsolidated materials:

cobbles, pebbles, grit, various composition, brownish yellow sand, silt, clay interbeds
together bearing placer gold gravel, distributed mainly in the valleys, rivers, streams,
slopes and alluvial fan, belonging to deluvial, alluvial and provial facies. The thickness
changed complicatedly.
3.2 . Sedimentary units
During the field trip, there are different sediment units that observed on the
surface. In the study are, sedimentary unit are distributed quite commonly and diversified
with the composition and formation origin. In this part, sedimentary unit is introduced to
several sedimentary units which includes:
1. Tuff deposit of Co Noi formation (T1cn)
2. Terrigene sediment of Song Boi formation(T2-3sb)
3. Coal deposit of Suoi Bàng formation( T3n-r-sb)
3.2.1. Tuff originated sediment of Co Noi formation.(T1cn)
Co Noi formation observed in Kim Binh- Kim Boi formation. In this itinerary,
light-violet siltstone, sandstone, sometimes gray, dark gray, tuff sandstone, violet thick-
bedded tuff-originated sediments exposed on the surface. Moreover a little quart and
feldspar that is weathered to formed kaolinite.
Co Noi formation have related to Vien Nam formation.

Figure 17:Sandstone, siltstone and tuff in
Co Noi formation
Figure 18: Quartz and feldspar is weathered
into kaolinite( white= quartz)

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3.2.2: Terrigene sediment of Song Boi formation(T2-3sb)
The terrigenous sediment of Song Boi formation(T2-3sb) in Xom Khoai, Lang
Noi itinerary. In this exposed point, stratigraphy cut over the limestone of Dong Giao
Formation and terrigene sediment of Song Boi formation, with north-northeast and south-
southwest elongation. The fold is observed:
+ folds that have steep hinge line
+ fold axis slept away.
structure data
Surface 1: 230<65
Surface 2: 95<50
The plunge of fold axis: 10

Figure 19: The terrigenous sediment of Song Boi formation(t2-3sb) and a fold is
observed.
3.2.3 Coal deposit with sandstone and siltstone in Suoi Bang formation(T3n-r sb).
Suoi Bang formation (T3n-r sb) observed in Lang Vo itinerary. In this outcrop,
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Sandstone, siltstone brearing with coal exposed on the surface. At the first exposed point
in here, the composition is sandstone mixed siltstone, from thin to medium layer rock.
Beside, a fold with structure data recorded:
One surface: 210<55

Hingline: 140<31.

Figure 20: A fold in the first expose point in Lang Vo itinerary.

In the second expose point:
Sandstone mixed siltstone and bearing coal, gray coal bearing claystone, and
several coal seams. In addition, go to inside about 10m, we saw the rock which foliated
into block and dark gray coal bearing claystone. And this block was dismantle weather.

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Figure 21: Sandstone, siltstone bearing coal
in Lang Vo itinerary in the second expose
point
Figure 22: Dismantle weather of bock
which form by Coal and claystone,
sandstone and siltsone was foliated

Go to inside to the third expose point, observation of plate sandstone and siltstone.
With data recorded:
Surface:320<75

Figure 23:Dip of a plate approximately 75degree which compose by sandstone and

siltstone in composition.