Alluvial deposits from the strike-slip fault Lo River Basin (Oligocene/Miocene), Red River Fault Zone, north-western Vietnam

Alluvial deposits from the strike-slip fault Lo River Basin

(Oligocene/Miocene), Red River Fault Zone, north-western Vietnam

Anna Wysockaa,*, Anna Swierczewskab

aFaculty of Geology, University of Warsaw, Zwirki i Wigury 93, 02-089 Warszawa, PolandbInstitute of Geological Sciences, Polish Academy of Sciences, Cracow Research Centre, Senacka 1, 31-002 Krakow, Poland

Received 28 June 2002; accepted 4 October 2002

Abstract

The Lo River Basin (LRB) is one of several narrow sedimentary basins associated with the main faults of the Red River Fault Zone

separating the South China and Indochina microplates. The basin is located on the NE boundary of the high-grade metamorphic Con Voi

Massif and the sedimentary and metasedimentary Viet Bac fold zone in north-eastern Vietnam.

The LRB is filled with over 6000 m of Oligocene/Miocene alluvial deposits. The source area was probably located on the NE margin of the

basin and was composed mostly of low-grade metamorphic rocks with a minor component of sedimentary rocks. Three alluvial systems are

recognised. The oldest system was a proximal braided river system, with the minor occurrence of alluvial fans. The younger systems record

changes in clast composition and lithofacies, which suggests a transition from a distal braided river to a distal braidplain system. The LRB fill

shows a range of features characteristic of strike-slip fault basins. The origin of the LRB is correlated with the left-lateral transtensional

regime. The present shape of the basin is a result of post-sedimentation tectonic activity.

q 2002 Elsevier Ltd. All rights reserved.

Keywords: Alluvial systems; Provenance; Tectonic-sedimentation; Facies associations; Southeast Asia

1. Introduction

The Lo River Basin (LRB) is one of several sedimentary

basins associated with the main faults in the Vietnamese

segment of the Red River Fault Zone (RRFZ; Fig. 1). The

basins are filled with Eocene–Pliocene continental clastic

deposits (Yem, 1985). The origin of the basins is probably

related to tectonic activity along the RRFZ (Bat, 2000;

Leloup et al., 2001).

Sedimentary basins can be classified in terms of their

position relative to plate margins and of the type of plate

interaction taking place during sedimentation. Based on a

plate-tectonic framework, they can be divided into: (1)

divergent margin basins; (2) convergent margin basins; (3)

transform- and transcurrent-fault basins; (4) basins devel-

oped during continental collision and suturing; (5) intraplate

basins (Miall, 2000). In this study we identify depositional

patterns in the LRB, which are associated with a suture-zone

transcurrent fault. The terms transcurrent fault, strike-slip

fault and wrench fault are used more or less synonymously

(Miall, 2000). A number of studies have documented

depositional patterns within basins limited by such faults

(see, e.g. Crowell and Link, 1982; McLaughlin and Nilsen,

1982; Hempton and Dunne, 1984; Steel, 1988; Dooley and

McClay, 1997; Ryang and Chough, 1999). It is important to

realise that tectonic activity in a strike-slip setting may

generate different structural styles along different segments

of a fault, therefore creating different types of basin, such as

fault-bend basins, pull-apart basins, transrotational basins

and transpressional basins (Nilsen and Sylvester, 1995).

Our study is the first sedimentological investigation of the

LRB. It was conducted, in the north-eastern part of Vietnam,

by a Polish-Vietnamese group of geologists. In this study we

focus on the sedimentary LRB fills, and on their connection

with the tectonic setting (Wysocka et al., 2001, 2003).

2. Structural and geological setting

The RRFZ can be followed for over 1000 km from Tibet

to the South China Sea (Fig. 1(A)). Some authors refer to

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PII: S1 36 7 -9 12 0 (0 2) 00 1 71 -2

Journal of Asian Earth Sciences 21 (2003) 1097–1112

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* Corresponding author. Tel.: þ48-22-5540445.

E-mail address: [email protected] (A. Wysocka).

http://www.elsevier.com/locate/jseaes

this zone also as the Ailao Shan–Red River Shear Zone

(Leloup et al., 1995; Tapponnier et al., 1990). It is composed

of four narrow, high-grade gneiss ranges: the Day Nui Con

Voi in Vietnam, and the Ailao, Diancang and Xuelong Shan

in China (Fig. 1(A)).

Left-lateral shearing along the RRFZ is dated as

Oligocene and Miocene. At that time, this narrow zone

acted like a continental transform plate boundary (Leloup

et al., 1995). Estimates of left-lateral offsets of geological

features along the shear zone calculated by Tapponnier

et al. (1990) range between 300 and 700 km. However,

the offset for the RRFZ in the area of the Tonkin Gulf

probably does not exceed a few tens of kilometres

(Rangin et al., 1995). New 40Ar/39Ar data from the south-

eastern outcrop of the Day Nui Con Voi metamorphic

massif in Vietnam suggest that the exhumation of the

metamorphic massif along the RRFZ began at ,27 Ma BP

and lasted until ,22 Ma (Wang et al., 2000). Moreover,

the time of initiation of denudation in the Day Nui Con

Voi and subsidence away from fault occurred about

Fig. 1. (A) Tectonic sketch of SE Asia (based on Tapponnier et al. (1986)). (B) Tectonic pattern of the RRFZ and the location of the LRB in northern Vietnam.

A. Wysocka, A. Swierczewska / Journal of Asian Earth Sciences 21 (2003) 1097–11121098

28 Ma (Late Oligocene). Rapid cooling of the massif from

350 8C to below 150 8C occurred between 25 and 22 Ma

(Leloup et al., 2001). At present, this zone corresponds to

right-lateral movements which started at about 5.5 Ma

(Allen et al., 1984; Leloup et al., 1995; Tapponnier et al.,

1990). The right-lateral offset ranges from 5.5 to 30 km

(Allen et al., 1984). New data from the Lo River Fault

(one of the branches of the RRFZ in Vietnam) point to

Quaternary dextral slip rates between 1 and 2 mm a21

(Cuong and Zuchiewicz, 2001).

In Vietnam the RRFZ is about 300 km long. It trends

NW–SE and is covered by the Cenozoic sediments of

the Hanoi Trough (Fig. 1(B)). The Chay River (Song

Chay) and the Red River (Song Hong) faults are major

faults of the RRFZ, and bound the Day Nui Con Voi to

the NE and to the SW, respectively. The prominent Lo

River (Song Lo) fault cuts the NE branch of the RRFZ

(Fig. 1(B)). This branch is sub-parallel to the RRFZ.

Left-lateral motion followed by right-lateral motion is

also documented along Lo River Fault (Cuong et al.,

2001; Cuong and Zuchiewicz, 2001). At present, the

faults associated with the RRFZ in Vietnam appear to be

dextral-slip and oblique-normal-dextral-slip faults (Cuong

and Zuchiewicz, 2001). Moreover, between the Lo River

Fault and the Chay River Fault, WNW–ESE and W–E

oriented growth anticlines are noted (Lacassin et al.,

1994).

Several Palaeogene/Neogene sedimentary basins occur

in the area between the Lo River and Chay River Faults,

close to both faults, as well as along the Red River Fault

itself (Fig. 1(B)). One of these basins is the LRB located in

Phong Chau and Lap Thach districts. Therefore, in our

previous studies we used the name ‘Phong Chau Basin’ for

the LRB (Wysocka et al., 2001). The NW–SE trending

LRB is about 40 km long and up to 5 km wide. The basin is

filled with clastic deposits over 6000 m thick. The age of the

deposits is probably the Late Oligocene/Early Miocene

(Yem, 1985) up to Late Miocene (Nhan and Danh, 1975).

The tectonic dip of the strata is ca. 208S. The present-day

shape of basin is triangular. The Chay River Fault strictly

limits this basin to the south (Fig. 2) while the Lo River

Fault, a normal fault, with oblique relations to the master

Chay River Fault, forms the northern border of the present-

day LRB.

The high-grade metamorphic Day Nui Con Voi Massif

occurs to the southwest of the LRB. It is composed of

garnet–biotite–sillimanite gneiss and garnet–biotite gneiss

as well as minor two-mica schists with garnet, amphibolite,

migmatite and marble (Tri, 1973; Nam et al., 1998).

Northeast of the basin, the Upper Proterozoic–Lower

Palaeozoic low-grade metamorphic and sedimentary rocks

of the Viet Bac fold zone form the area between the Lo

River and Chay River Faults. Several small granitoid

intrusions crop out also in this area. The rhyolitic Tam Dao

Massif of Triassic age occurs on the northeast limb of the Lo

River Fault (Fig. 2).

The present-day surface morphology of the LRB is

strongly diversified. The northern and central parts of

the area are hilly. The highest hills reach up to 250 m;

they are composed of Upper Oligocene/Lower Miocene

clastic rocks. Flat areas covered by Quaternary alluvial

deposits separate these hills. The morphology of the

southernmost part of the LRB is monotonous and covered

by Quaternary deposits. These features indicate post-

depositional uplift and pre-Quaternary erosion. Thus, it is

possible that the present basin shape is not its original

shape.

3. Materials and methods

The present research was carried out along the Lo

River banks, between Doan Hung and Viet Tri. In the

Vietnamese literature, outcrops from the Lo River have

been grouped into the following sections (from north to

south): Vu Quang, Xom Dom, Lang Giau (no outcrops

suitable for detailed sedimentological observations), Tri

Quan, Phan Luong (no outcrops suitable for detailed

sedimentological observations), Bach Luu and Tam Son

(Fig. 2(B)). The Lo River Sequence (Golovenok and

Chan, 1966, 1967; Yem, 1985) is composed of deposits

from these sections grouped in stratigraphic order (Fig.

3(A)). Detailed lithological sections were constructed

from the studied exposures (Figs. 2 and 3(B)). Palaeo-

current directions were measured in the Tri Quan ðn ¼

16Þ and Bach Luu sections ðn ¼ 39Þ; mainly from cross-

stratification and ripplemarks. Palaeocurrent rose dia-

grams were drawn and the mean vector magnitude

was calculated for each distribution (Gradzinski et al.,

1986).

Samples of medium and fine-grained sandstone and

conglomerate were collected. Sandstone point counts were

made for eight samples, following traditional methods.

Thin sections were stained for plagioclase and K-feldspar

identification using Houghton (1980) method. Analyses of

lithic clast composition were made for more than 50

clasts. Additional counts of quartz grains were made

according to the methods of Basu et al. (1975). Heavy

minerals were separated from two unaltered samples of

sandstone. The ,0.120 mm size fraction was analysed.

The composition of garnets was determined using the

microprobe. For each conglomerate clast count, more than

50 individual clasts were identified for each flat surface of

a single bed in the field. For fine-grained conglomerates,

the counts were obtained using thin sections and polished

slabs.

4. Facies associations

Nine sedimentary facies were recognised in the Lo

River Sequence (Table 1). The facies were grouped

A. Wysocka, A. Swierczewska / Journal of Asian Earth Sciences 21 (2003) 1097–1112 1099

into four facies associations representing four distinct

depositional environments (Table 2). These comprise

alluvial fan (Facies Association I), gravel-dominated

fluvial channel (Facies Association II), sand-dominated

fluvial channel (Facies Association III) and alluvial plain

(Facies Association IV).

4.1. Facies Association I: alluvial fan (F I)

This facies association is represented by decimetre to

metre thick, sand- and mud-supported disorganised

pebble- to cobble-size, occasionally boulder (Fig. 4(A))

breccia and conglomerate beds (facies Gb, Gms and Sm;

Tables 1 and 2; Fig. 4(B)). Most of the beds are massive

(Fig. 4(A)), with recognisable top and bottom surfaces.

Locally, normal grading is discernible. The conglomerate

beds are tabular, or broadly lenticular in shape. In some

cases, the contact with the underlying or overlying

deposits of other facies association is sharp and has an

erosive character.

The thick matrix-supported and disorganised conglom-

erate bodies indicate deposition by high-concentration

flows or by debris-flows (Nemec and Steel, 1984;

Nemec and Postma, 1993). The occurrence of these

conglomerate bodies inside and/or overlapping the

coarse-sand deposits of Facies Association II suggests

deposition in an alluvial fan setting associated with

active fault scarps.

Fig. 2. (A) Simplified geological map of the south-eastern part of the RRFZ in Vietnam (after Cuong and Zuchiewicz (2001)). (B) The LRB with the location of

the sections studied.


4.2. Facies Association II: gravel-dominated fluvial channel

(F II)

This facies association is composed predominantly of

sand- and clast-supported, poorly to well sorted, sub-

rounded to well-rounded pebble to cobble conglomerates

(Fig. 4(C) and (D)), and poorly sorted pebbly sandstones

(facies Gt, Glg and Sm; Tables 1 and 2). The facies Glg is

represented by centimetre to decimetre thick crudely bedded

clast-supported cobble conglomerates. They have erosive

bases and show a rapid upward fining trend in the topmost

part of the beds. This facies can be interpreted as the basal

gravel lag of a barform (Zielinski, 1997; Vincent, 2001),

particularly because it was observed below the trough-cross-

stratified (facies Gt) and/or massive pebbly sandstones

(facies Sm). Massive or poorly stratified reddish siltstones,

commonly alternating with sandy siltstones (Fig. 6(B)),

occur as a rule above facies Gt and Sm.

Facies Association II is composed of repeated fining

upward cycles, usually more than 2 m thick (Fig. 4(E)).

Fig. 3. (A) Summary logs of exposed sections of the Lo River Sequence. Oblique pattern boxes—detailed sedimentological sections presented in Fig. 3(B);

grey boxes—sections without detailed sedimentological observations. (B) Measured sections arranged in the downstream direction of palaeoflow (for locations

see Fig. 2(B); for palaeoflow directions see Fig. 7). Lithofacies codes as in Table 1.


Such features indicate deposition from bedload transport in

form of barforms with different fluid flow and sediment

discharge that is characteristic for gravel-dominated fluvial

channels. In some cases, siltstones pointing to relatively low

sedimentation rates, terminate particular cycles.

4.3. Facies Association III: sand-dominated fluvial channel

(F III)

This facies association is composed of poorly to well-

sorted, medium- to coarse-grained, occasionally fine-

grained, sandstones (facies St, Sp, Sr and Gt, Sm; Tables 1

and 2). Facies St and Sp are represented by centimetre to

decimetre thick sets (Fig. 5(B)) building metre thick cosets

(Figs. 3(B), 5(A) and (C)). Coalified flora fragments

and muddy intraclasts are commonly dispersed within

fine-grained sandstones (Figs. 5(E) and 6(E)). Occasionally,

in the Bach Luu and Tam Son sections, synsedimentary

folds also occur between undisturbed sandstone strata

(Fig. 6(F)). The alternation of sandy facies St/Sp/Sr with

coarse sediment admixtures indicate deposition from bed-

load transport in the sand-dominated fluvial channels

carrying dune scale sinuous- and straight-crested barforms

covered with ripples (Fig. 5(D)) indicating a continuous but

highly variable sediment discharge.

4.4. Facies Association IV: alluvial plain (F IV)

This facies association is dominated by reddish siltstones

(facies Fr; Tables 1 and 2; Fig. 6(B)) and grey siltstones

(facies Fg; Tables 1 and 2; Fig. 6(A)). The latter contain

clayey and coal lenses and layers (facies Fg/C; Tables 1 and

Table 1

Lithofacies identified in this study (lithofacies codes based on Miall (1977, 1978))

Facies Description Interpretation

Sand- and mud-supported

disorganised breccias (Gb)

Decimetre thick; poorly defined, discontinuous

beds; pebble- to cobble-size and angular to sub-rounded

clasts; sand to mud matrix

Deposition from debris and/or

high-concentration flow

Sand- and mud-supported disorganised

conglomerates (Gms)

Up to 2 m thick; highly amalgamated; pebble-

to cobble-size and sub-rounded to well-rounded

clasts; fining-upwards trend; sand- to mud matrix;

may be erosively based

Deposition from high-concentration

flow

Crudely bedded conglomerates (Glg) Decimetre thick; cobble-size and sub-rounded to

well-rounded clasts; clast supported; rapid finning

upwards at top; erosively based

Lag deposits; size segregation due to

winnowing at erosive surfaces or during

barform migration

Planar and trough cross-stratified

sand-supported conglomerates (Gt)

Up to several metres thick; highly amalgamated;

low angle trough cross-stratified; pebble-size and

sub-rounded to well-rounded clasts; gravel patches

with partly open-work fabric common; very coarse

to coarse sand matrix

Bedload transport; downstream migration

of sinuous-crested barforms

Massive or amalgamated beds of

sandstones (Sm)

Up to several metres thick; poorly defined beds;

poorly sorted; isolated pebbly sandstones lenticles

and layers; occasionally normally graded; often developed

above the Gt or Glg lithofacies as part of a fining upwards

trend

Upper plane bed flow

Planar and trough cross-stratified

sandstones (Sp/St)

Variable thickness of sets (up to 1 m); poor to well

sorted; medium to coarse granted; low angle bounding

surfaces; occasionally coalified flora fragments, muddy

intraclasts occur

Downstream migration of ripple and dune

scale sinuous- (St) or straight-crested (Sp)

barforms, in same cases falling to low stage

gravelly barform modifications

Ripple cross-laminated

sandstones (Sr)

Thin sets (up to 10 cm); well sorted; fine-grained;

asymmetrical ripples

Downstream migration of ripple scale barforms

Reddish siltstones (Fr) Generally thick (a few metres); massive or poorly

stratified; common alternated with sandy siltstones;

occasionally pedogenic (?) structures

Deposition of fine grains on alluvial plain;

oxidising conditions during and after deposition

Grey siltstones with clayey and

coal interbeds (Fg/C)

Up to 50 cm; stratified; coal layers up to 5 cm Deposition of fine grains and organic matter

on alluvial plain

Table 2

The Lo River Sequence characteristic facies associations and their depositional environments

Association Dominant facies Minor facies Depositional environment

I Gms, Gb Sm Alluvial fan

II Gt, Glg, Sm Fr Gravel-dominated fluvial channel

III St, Sp, Sr Gt, Sm Sand-dominated fluvial channel

IV Sp, Fr, Fg Fg/C Alluvial plain


2; Fig. 6(C)). In some cases, clayey intraclasts and mud

curls and flakes also occur in grey siltstones (Fig. 6(D)). The

reddish siltstones commonly contain fine-grained sandstone

interbeds and calcareous nodules of a probable pedogenic

origin. As a rule, the reddish siltstones terminate the fining-

upward sequences of Facies Association II from the Vu

Quang and Xom Dom sections (Fig. 3(B)).

The thick reddish siltstone capping the fining-upward

sequences indicate deposition during the lowest velocity

flow. The red colour of these siltstones may suggests

oxidising condition during or after deposition. The pedo-

genic structures are indicative for occasional subaerial

exposure. Coal and clayey lenses (Fig. 6(C)) within the grey

siltstones point to high organic influx and to deposition in

standing bodies of water. The development of reddish and

grey siltstone facies is indicative of deposition in an alluvial

plain, occasionally occupied by lakes. However, neither

freshwater fauna nor pollen were found in the collected

samples.

5. Depositional systems

The palaeoflow directions (Fig. 7) and the lateral fining

of facies (Figs. 3(B) and 7; Tables 2 and 3) indicate that the

alluvial system generally flowed from the northwest. Based

on the lateral changes of the lithofacies pattern, the Lo River

Sequence can be divided into three units: Vu Quang

Fig. 4. Alluvial fan (F I) and gravel-dominated fluvial channel (F II) facies associations. (A) Massive sand-supported disorganised breccia (facies Gb) with a

clear base and underlying massive sandstone (Sm). Xom Dom section. (B) Sharp contact between sand-supported disorganised conglomerate (facies Gms) and

massive sandstone (Sm). Xom Dom section. Hammer is 30 cm long. (C) Horizontal alternating stratified conglomerates and sandstones. Graded bedding is

clearly visible in the conglomerates. Xom Dom section. Hammer is 30 cm long. (D) Massive sand-supported conglomerate (facies Gms). Vu Quang section.

Hammer is 30 cm long. (E) Massive coarse-grained sandstone developed above planar and trough cross-stratified sand-supported granule- to pebble-sized

conglomerates. This is a part of fining-upwards trend of Facies Association II. Vu Quang section. Hammer (circled) is 30 cm long.


(,3 km thick), Tri Quan (,2 km thick) and Tam Son

(,1 km thick) units. The sedimentary characteristics of

each unit are summarised in Table 3.

5.1. Vu Quang unit

This unit (,3 km thick) is present in the northernmost

part of the LRB (Figs. 3(B) and 7), and was identified in the

Vu Quang, Xom Dom and Lang Giau sections. Best exposed

is the Vu Quang section, which is a long scarp along the Lo

River bank, on the north-eastern slope of an unnamed hill,

about 240 m high. The Vu Quang unit is characterised by

gravel-dominated fluvial channel deposits (Facies Associ-

ation II), reddish siltstones deposited in an alluvial plain

environment (Facies Association IV) and coarse-grained

sand- and mud-supported disorganised alluvial fan breccias

and conglomerates (Facies Association I). The entire unit

consists of repetitive fining-upward cycles. A cycle starts

with a planar or trough cross-stratified sand-supported

conglomerate (facies Gt, Glg), that is overlain by massive or

amalgamated beds of coarse-grained sandstones (facies

Sm), followed by reddish siltstones (facies Fr), commonly

alternating with sandy siltstones and fine sandstones. The

sand- and mud-supported disorganised pebble- to cobble-

size breccia (facies Gb) and conglomerate (facies Gms)

bodies surrounded by cross-stratified, fine pebble-conglom-

erates and coarse-grained sandstones probably developed as

a marginal alluvial fan.

Fig. 5. Sand-dominated fluvial channel (F III) Facies Association. Hammer is 30 cm long. (A) General view of the planar and trough-cross-stratified sandstones

(facies Sp/St). Lower part of the Tri Quan section. The scale bar is ca. 1 m. (B) Set of coarse-grained planar- and trough-cross-stratified sandstones. Bach Luu

section. (C) Cosets of metre thickness built of centimetre to decimetre thick sets of planar- and trough-cross-stratified sandstone (facies Sp/St). Bach Luu

section. (D) Surfaces of fine-grained sandstones covered by three generations of ripplemarks: straight-crested small-current ripples (a), undulatory small-

current ripples (b) and linguoid-shaped small-current ripples (c). Bach Luu section. (E) Top views of the fine-grained sandstones bed with abundant flat clay

clasts. Bach Luu section.


The depositional features of the Vu Quang unit suggest

that deposition was connected with a bedload-dominated

gravel-bed braided river with a relatively well developed

alluvial plain. Such features are characteristic of the

proximal braided river systems of the Scott or Donjek

types (Miall, 1985). The great thickness and numerous

repetitive fining-up cycles within the Vu Quang unit may

reflect a relatively high rate of subsidence, where the

aggradation rate was also relatively high. The presence of

the alluvial fan deposits points to local syn-depositional

relief.

5.2. Tri Quan unit

This unit (,2 km thick) is present in the central part of

the LRB (Figs. 3(B) and 7). It is exposed in the Tri Quan,

Phan Luong and Bach Luu sections. The Tri Quan section

was assembled from two quarries. The Phan Luong and

Bach Luu sections were compiled on the basis of

observations in small natural exposures on the slopes of

hills and in a small quarry. The Tri Quan unit is

characterised by sand-dominated fluvial channel deposits

(Facies Association III) interbedded with gravel-dominated

channel fills (Facies Association IV). Planar cross-stratifica-

tion (facies Sp) prevails, whereas trough cross-stratification

(facies St) is less common. Ripple cross-laminated fine-

grained sandstones (facies Sr) are also present. The sandy

deposits of the Tri Quan unit contain gravel lenses, coalified

flora fragments and muddy intraclasts. They are occasion-

ally intercalated with fine-grained overbank deposits

containing coal layers.

The depositional features of the Tri Quan unit suggest

that deposition was connected with a bedload-dominated

sand-bed river. This was a sand-dominated system, with a

wide channel and flat, linguoid sandbars and sand waves

covered by smaller bed forms such as dunes and ripples.

Fig. 6. Alluvial plain and/or lacustrine (F IV) Facies Association. Hammer is 30 cm long. (A) Thin-bedded sandy siltstones (facies Fg). Xom Dom section.

Hammer is circled. (B) Reddish siltstones (Fr) alternated with sandy siltstones. Vu Quang section. (C) Coal lens within grey siltstones. Xom Dom section.

Pencil is 17 cm long. (D) Mud curls and flakes from fine-grained sandstones. Tam Son section. (E) Top view of a sandstone bed with abundant flat clay clasts.

Tam Son section. The pencil is 17 cm long. (F) The top view of a sandstone bed with synsedimentary folds (the surface intersects the folds). Tam Son section.


These features are characteristic of a distal braided river

system of the Platte type (Miall, 1985).

5.3. Tam Son unit

This unit (,1 km thick) is present in the southernmost

part of the LRB (Figs. 3(B) and 7) being exposed poorly

only in the Tam Son section. A few small exposures occur in

the Lo River banks. Quaternary deposits cover most of the

Neogene rocks in this part of the LRB. The grey siltstones

(facies Fg) with clayey interbeds and planar cross-stratified

sandstones (facies Sp) are the most typical rocks for this

unit. Sandy deposits contain numerous muddy intraclasts.

The Tam Son unit is built of sand-dominated fluvial channel

deposits (Facies Association III) and of alluvial plain

deposits (Facies Association IV). Abundant synsedimentary

fold deformation occurs within the sandy layers.

The Tam Son unit was deposited in a sand-dominated

river system probably characterised by a broad river plain

with very shallow channels. These features are character-

istic of the distal braidplain system of Bijou Creek type

(Miall, 1985). There are no index features for syn-

depositional relief, however abundant synsedimentary fold

deformations point to seismic activity.

Fig. 7. Sketch map of the LRB.

Table 3

Characteristics of depositional units

Unit Facies association Dominant facies Main depositional features Depositional system

Vu Quang unit (comprising

Vu Quang, Xom Dom

and Lang Giau sections)

I, II, IV Gt, Gms, Gb, Glg,

Sm, Fr

(,3.0 km thick) repetitive

fining-upward sequence;

Gt/Glb/Gb ! Sm ! Fr facies

progression

Bedload-dominated gravel

bed river with relatively well-

developed alluvial plain; with

minor marginal alluvial fan

development

Tri Quan unit (comprising

Tri Quan, Plan Luong

and Bach Luu sections)

II, III St, Sp, Gt, Sm,

Sr

(,2.0 km thick) alternation of

sandy facies St/Sp/Sr; episodic

coarse-grained material supply

Bedload-dominated sand

bed river; with minor alluvial

plain development

Tam Son unit (comprising

Tam Son section)

III, IV Sp, St, Fg (,1.0 km thick) alternative of

fine-grained sandy facies Sp/St;

abundant synsedimentary fold

deformations

Sandy river plain and/or

alluvial plain; seismic activity

marked by synsedimentary

deformations


6. Petrographic results

6.1. Conglomerates

Sedimentary and low-grade metamorphic clasts are the

main components of conglomerates from the Vu Quang and

the Tri Quan units. Sedimentary clasts include quartzite

sandstones, cherts, crystalline limestones, and mudstones.

The low-grade metasedimentary group of clasts consists of

slate, phyllite, mica-quartz schists, and quartzite. Well-

rounded marble and volcanic clasts occur occasionally.

Granitoid clasts were not found. Large feldspar grains and

vein quartz are common in fine-grained conglomerates.

There is a variability in clast composition between the

facies associations. A high content of quartz and feldspar is

characteristic of Facies Association II (gravel-dominated

fluvial channel) of the Tri Quan unit (Fig. 11(B)), where

they may be the main component of conglomerates. In

Facies Association I (alluvial fans), occurring only in the Vu

Quang unit, metamorphic rocks are more frequent, whereas

in Facies Association II (gravel-dominated fluvial channel)

occurring in both units, hard siliceous rocks are more

common.

6.2. Sandstones

The main grain constituent in all sandstone samples is

quartz, followed by lithic clasts. According to Pettijohn’s

classification (Pettijohn et al., 1972) the sandstones

are mostly lithic arenites, exceptionally sublitharenites

(Fig. 8(A)).

6.2.1. Quartz

Quartz occurs as monocrystalline (Qm) and polycrystal-

line grains (Qp). Grains are sub-angular to poorly rounded.

Only a few of them show abraded overgrowths of secondary

quartz. Most grains show undulose extinction. Four different

varieties of quartz were distinguished (Basu et al. 1975): (1)

Qu—monocrystalline grains showing undulose extinction;

(2) Qnu—monocrystalline grains with non-undulatory

extinction; (3) Qp2–3—polycrystalline grains composed

of 2–3 crystals; (4) Qp . 3—polycrystalline grains with

more than three crystals. The contents of Qp . 3 in the Vu

Quang and Tri Quan sandstones are higher then from Tam

Son sandstones (Fig. 9). The mean percentages of the four

quartz grain types are: Qnu(17), Qu(28), Qp2–3(16), and

Qp . 3(39) in the Vu Quang sandstones; Qnu(15), Qu(34),

Qp2–3(11), and Qp . 3(40) in the Tri Quan sandstones;

Qnu(29), Qu(44), Qp2–3(14), and Qp . 3(13) in the Tam

Son sandstones.

The relative percentages of the four quartz types have

been plotted on the provenance–discrimination diagram of

Basu et al. (1975) with modification of Tortosa et al. (1991)

(Fig. 10). All samples plot in the low-grade metamorphic

field of the Basu diagram. Using the modified diagram of

Tortosa et al. (1991), samples from the Tam Son unit are

located in granite field, whereas the others plot in the slate

and schist fields.

6.2.2. Lithic grains

The proportion between sedimentary and metamorphic

lithic grains shows a strong variability (Fig. 11(A)).

Among sedimentary rocks, fine-grained quartzite sand-

stones and cherts are the most common. Crystalline

limestones and mudstones are rare. Clasts of low-grade

metasedimentary rocks include slate, phyllite, mica-quartz

schist, and quartzite. Rare marble and quartz–feldspar–

biotite aggregates, having a slight preferred planar fabric,

were also identified. Volcanic lithic grains (microlithic

and felsitic textures) occur occasionally. They are very

well rounded. Clasts of sedimentary rocks are more

Fig. 8. Framework mineral composition of sandstones plotted on QFRf

diagram (Pettijohn et al., 1972); Q—total monocrystalline (Qm) and

polycrystalline (Qp) quartz grains; F—total feldspar; Rf—lithic grains.

Number of samples (n ) ¼ 7.

Fig. 9. Mean percentages of four quartz types; Qnu—non-undulatory

monocrystalline quartz, Qu—undulatory monocrystalline quartz, Qp(2–

3)—polycrystalline quartz with two to three crystals units per grain, and

Qp . 3—polycrystalline quartz with greater than three crystals units per

grain.


frequent in the lower part of sections (the Vu Quang unit),

whereas the content of metamorphic rocks increases

toward the top of the section.

6.2.3. Heavy and other minerals

Heavy minerals were studied only in the Tri Quan unit

where garnet predominates (Fig. 12(A)). The variety of

composition shown by detrital garnets is low. The ternary

diagram illustrating the compositional differences in garnet

population shows a constant content of grossular and low

variation in pyrope/almandine and spessartine content

(Fig. 12(B)). The mean composition of garnets is:

almandine 73.0%, pyrope 15.9%, spessartine 6.5% and

grossular 4.1%. Sub-angular tourmaline with blue and

brown pleochroism, staurolite, rounded zircon and iron–

titanium oxides are less common. Single grains of

hornblende, apatite, chloritoide, epidote and rutile were

recognised.

Among feldspars, K-feldspars are the most frequent.

Microcline is common. Plagioclase of albite composition is

less frequent. In unaltered samples feldspar grains are fresh,

sub-angular to sub-rounded. Only single grains are slightly

sericitized. In altered sandstones, calcitization and kaolini-

tization affect feldspar grains. The grains are either

dissolved or replaced by ferrous and kaolinite pseudo-

morphs and partially by calcite. Muscovite occurs in all

samples. Flakes of biotite are rare and altered.

7. Evidence for source rock types

7.1. Quartz evidence

The QnuQuQp diagram of Basu et al. (1975) is

recommended by Girty et al. (1988) for the discrimination

of quartz grains derived from plutonic rocks from those

derived from metasedimentary rocks. However, Tortosa

et al. (1991) suggest that the diagram must be used with

caution if plutonic and middle–upper grade metamorphic

rocks were present in the source area.

Based on both provenance–discrimination diagrams, the

studied quartz grains were derived mostly from low-grade

metamorphic rocks. The occurrence of granitic rocks can be

only documented in the source area of the Tam Son

sandstones. The results of quartz grain analysis preclude the

occurrence of middle and high-grade metamorphic rocks in

the source area.

Fig. 10. Point-count data derived from medium-grained detrital quartz

population plotted on diamond-shaped provenance–discrimination dia-

gram of Basu et al. (1975) with modification of Tortosa et al. (1991); heavy

lines indicate provenance field by Basu et al. (1975): 1—plutonic, 2—

middle and upper rank metamorphic, and 3—low-grade metamorphic;

provenance fields by Tortosa et al. (1991) in grey. Qnu—non-undulatory

monocrystalline quartz; Qu—undulatory monocrystalline quartz.

Fig. 11. Composition of total rock fragments. (A) Ternary diagrams LmLvLs showing proportion of the total rock fragments for sandstones and conglomerates;

Lm—metamorphic rocks, Lv—volcanic rocks, and Ls—sedimentary rocks. (B) Histograms showing variation in abundance of feldspar (F) and quartz (Q) in

gravels.


7.2. Lithic clast evidence

The lithic clast composition suggests that the source area

was composed of the low-grade metamorphic and clastic

sedimentary rocks. The very rare clasts of rounded volcanic

rocks imply a long distance of transport from volcanic

bodies located far from the basin. An estimation of

sedimentary to metamorphic rock ratio in the source area

is difficult. Alluvial fan conglomerates indicate the

predominance of low-grade metamorphic rocks in the

source area during sedimentation of the Vu Quang unit.

The higher maturity of fluvial channel conglomerates and

their absence in upper part of the Lo River Sequence,

suggest that the compositional variation is related to

differences in clast resistance to transportation.

Any vertical trend in sandstone composition has not been

determined clearly. However, low-grade metamorphic

clasts become more abundant in the upper part of the

section. These changes can be related to the uplift and

progressive erosion of the metamorphic massif cover.

Systematic erosion could gradually expose low-grade

metamorphic rocks underlying the sedimentary cover.

Consequently, the documented distribution of lithic clasts

shows the evolution of the same source through time. Other

possibilities are that the increase in metamorphic lithic

fragments may be related either to a change in the relative

proportions of different source rock types, or to differences

in resistance during transportation. The latter is confirmed

by the succession of the fluvial facies.

7.3. Heavy mineral evidence

The consistent composition of detrital garnets (Fig. 12(B))

shows that they were derived from only one source.

Almandine, which is most common, is the typical garnet of

schists resulting from the regional metamorphism of

argillaceous sediments. Staurolite, which was found in both

samples, is also common in this type of rocks. Almandine

may occur locally as a product of thermal or contact

metamorphism and in plutonic rocks due to contamination

of granitic material by argillaceous impurities (Deer et al.,

1962). Biotite schists are the most likely source for the

garnets (Morton, 1991) the more so, as garnets from the Con

Voi gneisses are richer in pyrope (Nam et al., 1998). Other

common minerals, e.g. tourmaline and zircon grains, may be

secondary cycle grains in the studied materials.

8. Discussion

Common elements for the strike-slip fault basins are: (1)

relatively small size (a few tens of kilometres across); (2)

very rapid sedimentation rates (.1 m/103 years); (3)

marked facies variability; (4) evidence of local syn-

depositional relief, such as fault-flank conglomeratic

wedges; (5) signs of syn-depositional tectonism, such as

intraformational folds and local unconformities; (6) lateral

offset of the basin fill from its source area; (7) different

stratigraphies in adjacent basins; (8) distinctive shear

structures with predictable orientations; (9) the common

dissection of the basin fill by later strike-slip faults (after

Miall (2000)). The LRB exhibits most of the above features.

At present, the LRB is only 5 km across and is filled with

over 6000 m of Oligocene/Miocene deposits. Because of

multistage structural development of the Vietnamese

segment of the RRFZ, it is difficult to reconstruct the

original shape and size of the basin. In an early stage of

the LRB development, the Vu Quang unit was deposited in

the north-western area in a proximal braided river system.

The great thickness and numerous repetitive river cycles

within this unit may reflect a relatively high rate of

subsidence, where the aggradation rate was also high. The

presence of minor alluvial fan deposits points to local syn-

depositional relief in the form of fault-flank conglomeratic

wedges. These features suggest that the Vu Quang unit was

formed in the vicinity of a fault-controlled scarp margin.

Neither the Tri Quan nor the Tam Son units show features

indicative of significant syn-depositional relief. In the three

Fig. 12. Pie-diagrams of the heavy mineral composition. (A) Heavy mineral assemblages of Tri Quan unit. (B) Composition of garnets; P—pyrope, AS—

almandine and spessartine, and G—grossular. Number of measurements (N ) ¼ 78.


alluvial deposition systems, consistent N–S palaeocurrent

directions are observed. Moreover downstream changes in

clast size and sedimentary facies document a transition from

a coarse-grained proximal braided river system, through a

distal braided river system, to a distal braidplain system.

Furthermore, the presence of intraformational folds points

to syn-depositional tectonism.

The composition of sandstones and conglomerates, as

well as the directions of fluvial transport, indicate that the

source area lay to the northeast of the basin. At the present

time low-grade metamorphic rocks and sedimentary rocks

occur along the north-eastern margin of the basin and in the

Day Nui Con Voi Massif. During filling of the basin, low-

grade metamorphic rocks may also have occurred in the

cover of the Day Nui Con Voi Massif.

Small granitic bodies can be used as an indication of the

amount of offset along the faults. At present the Tam Son unit

is exposed in vicinity of granite intrusions (Tri, 1973). This

relationship suggests that there was only a small offset of the

source area during or after sedimentation of the youngest part

of the section. The studies of conglomerates from basins

located along the Lo River Fault do not provide clear

evidence of the possible offset of the source area. The

absence in the basin fill of rhyolitic clasts attributable to the

Tam Dao Massif, which lies only a short distance to the north

of the basin, can be interpreted either as evidence of lack of

tectonic relief along the Lo River Fault or that considerable

strike-slip offset took place after deposition of the conglom-

erates along the Lo River Fault (Cuong et al., 2001).

Sedimentary basins from the Vietnamese segment of the

RRFZ (Fig. 1(B)) are filled with a thick series of Palaeogene

and Neogene clastic deposits that are different in type and

origin. In the lower part of basin fill, coarse-grained deposits

predominate. In the upper part, different types of sandstone,

siltstone and brown coal occur (Yem, 1985). There are no

sediments of Upper Pliocene age. Quaternary deposits are

sands and gravels. Unfortunately, because biostratigraphic

data are very poor (Nhan and Danh, 1975), the stratigraphy

is based on the lithological succession (Yem, 1985). Thus, it

is possible that deposits in adjacent basins associated with

the RRFZ have a different stratigraphic age and that the

basins have a different history.

An open question is the Palaeogene/Neogene tectonic

history of the Vietnamese segment of the RRFZ, particularly

with regards to the synsedimentary and post-sedimentary

tectonic evolution of areas adjacent to the LRB. The only

seismic and drilling data from the Vietnamese part of RRFZ

comes from the Tonkin Gulf (Rangin et al., 1995; Tham,

1998; Bat, 2000), about 300 km to the south-east of the study

area. For this region, the data suggest four main stages of

structural evolution: (I) before the 30 Ma unconformity

connected with active extension during the rift opening; (II)

between 30 and 15.5 Ma unconformities connected with left-

lateral transtensional regime; (III) between 15.5 and 5.5 Ma

unconformities connected with left-lateral transpressional

regime after cessation of the sea-floor spreading within

the South China Sea; (IV) after 5.5 Ma unconformity related

to recent right-lateral movement (after Rangin et al. (1995)).

Even though the LRB lies at a distance of about 300 km from

the Tonkin Gulf, it is probable that its structural evolution has

a great deal in common with other parts of the Vietnamese

segment of the RRFZ.

Generally, the NW–SE trending LRB is situated in the

area between two, almost parallel master strike-slip faults:

the Chay River and the Lo River Faults (Fig. 1(B)). During

the sedimentation of the Oligocene/Miocene deposits that

fill the LRB, master strike-slip faults corresponded to left-

lateral movements were active (Tapponnier et al., 1990;

Leloup et al., 1995, 2001; Rangin et al., 1995). The recent,

triangular shape of the LRB is strictly limited by faults; one

of them is the master Chay River strike-slip fault, and the

second is probably a normal fault. The angle between the

potential normal faults from the area between the Lo River

and Chay River master strike-slip faults is 208 or less (Fig.

2(A)). The angle between the normal faults and the strike-

slip faults is strongly dependent on the overall boundary

conditions and, in transtensional conditions, this angle can

vary from 10 to 658 (Bertoluzza and Perotti, 1997). These

relationships and the position of the LRB suggest that

during its formation, sinistral strike-slip movements along

the RRFZ were accompanied by the separation of two

crustal blocks which formed an overstep. Thus, during

sedimentation the LRB appears to have been a typical pull-

apart basin. The resultant transtensional regime might have

been connected with the exhumation of the Day Nui Con

Voi metamorphic massif that began ,27 Ma and lasted

until ,22 Ma (Wang et al., 2000; Leloup et al., 2001). The

exhumation should probably be correlated with the second

stage of structural evolution of the Tonkin Gulf area (left-

lateral transtensional regime according to Rangin et al.

(1995)). This history is consistent with results from the Lo

River Fault (Cuong et al., 2001). Along the Lo River Fault,

Palaeogene strata, probably Oligocene in age, were

deposited during a N–S oriented extension (possibly

correlative with the first and second structural stage after

Rangin et al. (1995)) and subsequently deformed during two

successive phases of compression, oriented, respectively,

W–E and NE–SW (Cuong et al., 2001). These phases

corresponded to sinistral (the third structural stage of

Rangin et al. (1995)) and dextral strike-movements (the

fourth structural stage of Rangin et al. (1995)). Moreover,

the post-depositional uplift and pre-Quaternary erosion in

the investigated area might be correlated with the third stage

of the Tonkin Gulf evolution (left-lateral transpressional

regime, according to Rangin et al. (1995)). These sugges-

tions, however, obviously need further investigation.

9. Conclusions

1. Three alluvial systems are recognised in the Lo River

Sequence on the basis of lithofacies changes. Each


system shows a downstream change in clast size and

sedimentary facies. The Vu Quang unit is connected with

the development of a proximal braided river system with

the minor influence of alluvial fans. The Tri Quan and

Tam Son units record changes in clast composition and

lithofacies, which suggest a transition from a distal

braided river to a distal braidplain system.

2. The source area was composed mostly of low-grade

metamorphic rocks with a minor proportion of sedimen-

tary rocks. During sedimentation of the youngest unit, a

minor influx took place from a granitic source. There is

no evidence for the exhumation of a high-grade

metamorphic massif, in particular the Day Nui Con

Voi metamorphic massif, during the infilling of the LRB.

3. The LRB fill shows a range of features indicative of

deposition in a strike-slip fault basin originating in a left-

lateral transtensional regime.

Acknowledgements

We gratefully acknowledge the support of Professor

Szczepan Porebski (Polish Academy of Sciences) in

reviewing the manuscript, constructive comments, and

linguistic help. Many thanks for helpful discussions to

Prof. N.T. Yem (National Center for Natural Science &

Technology, Hanoi) and N.Q. Cuong (Polish Academy of

Sciences), and for extensive field assistance to Ph. D. Pha,

Dr L.T. Nghinh, Dr D.D. Lam and Dr N.V. Huyen (National

Center for Natural Science & Technology, Hanoi). The

research was supported by the Polish Academy of Sciences,

Warsaw University, Polish Committee for Scientific

Research (Grant No. 6PO4E 02618) and by a grant of the

Polish Science Foundation. Drs G.D. Nichols and A.J.

Barber made suggestions for the improvement of the

presentation.

References

Allen, C.R., Gillespie, A.R., Han, Y., Sieh, K.E., Zhun, B., Zhu, Ch.N.,

1984. Red River and associated faults Yunnan Province, China:

Quaternary geology, slip rates, and seismic hazard. Geological Society

of America Bulletin 95, 686–700.

Basu, A., Young, S.W., Suttner, L.J., James, W.C., Mack, G.H., 1975. Re-

evaluation of the use of undulatory extinction and polycrystallinity in

detrital quartz for provenance interpretation. Journal of Sedimentary

Petrology 45, 873–882.

Bat, D., 2000. Stratigraphy and development of Tertiary sediments on the

Vietnam continental shelf. Petrovietnam Review 3, 9–17.

Bertoluzza, L., Perotti, C.R., 1997. A finite-element model of the stress field

in strike-slip basins: implications for the Permian tectonics of the

Southern Alps (Italy). Tectonophysics 280, 185–197.

Crowell, J.C., Link, M.H., 1982. Geologic History of Ridge Basin,

Southern California. Society of Economic Paleontologists and Miner-

alogists, Dallas, TX, Pacific Section, Field Trip Guidebook, p. 304.

Cuong, N.Q., Zuchiewicz, W., 2001. Morphotectonics of the Lo River Fault

near Tam Dao (northern Vietnam): an attempt at seismic prognosis.

Przeglad Geologiczny 49, 885–893. (in Polish with English abstract).

Cuong, N.Q., Tokarski, A.K., Swierczewska, A., Oliwkiewicz-Mikla-

sinska, M., 2001. An approach to the structural history during Cenozoic

of the Lo River Fault (North Vietnam). Journal of Geology, Series B 17/

18, 45–53.

Deer, W.A., Howie, R.A., Zussman, M.A., 1962. Rock-Forming Minerals.

Ortho- and Ring Silicates, Longmans, London, p. 333.

Dooley, T., McClay, K., 1997. Analog modeling of pull-apart basins.

AAPG Bulletin 81, 1804–1843.

Girty, G.H., Mossman, B.J., Pincus, S.D., 1988. Petrology of Holocene

sand, Peninsular Ranges, California and Baja Norte, Mexico:

implications for provenance–discrimination models. Journal of Sedi-

mentary Petrology 58, 881–887.

Golovenok, V.K., Chan, L.V., 1966. Litologia i uslovia obrazovania

neogen-Tchetvertitchnie otlojenii Hanoiskogo progiba. Petrovietnam,

Hanoi (Unpublished; in Russian & Vietnamese).

Golovenok, V.K., Chan, L.V., 1967. Novui dannie po Neogen-Tchetver-

titchnym otlojenimi Hanoiskogo progiba. Petrovietnam, Hanoi (Unpub-

lished; in Russian & Vietnamese).

Gradzinski, R., Kostecka, A., Radomski, A., Unrug, R., 1986. Zarys

sedymentologii. Wydawnictwa Geologiczne, Warszawa, p. 624 (in

Polish).

Hempton, M.R., Dunne, L.A., 1984. Sedimentation in pull-apart basins,

active examples in Eastern Turkey. Journal of Geology 92, 513–530.

Houghton, H.F., 1980. Refined techniques for staining plagioclase and

alkali feldspars in thin sections. Journal of Sedimentary Petrology 50,

629–631.

Lacassin, R., Tapponnier, P., Leloup, P.H., Trinh, P.T., Yem, N.T., 1994.

Morphotectonic evidence for active movements along the Red River

Fualt Zone. Actes du Colloque, Colloque Internationale. Sur la

seismotectonique et le risque sismique en Asie du Sud Est, Hanoi, pp.

66–71.

Leloup, P.H., Lacassin, R., Tapponnier, P., Scharer, U., Dalai, Z., Xiaohan,

L., Liangshang, Z., Scharer, U., Dalai, Z., Xiaohan, L., Trinh, P.T.,

1995. The Ailao Shan–Red River Shear Zone (Yunnan, China),

Tertiary transform boundary of Indochina. Tectonophysics 251, 3–84.

Leloup, P.H., Arnaud, N., Lacassin, R., Kienast, J.-R., Harrison, T.M., Phan

Trong, T.T., Replumaz, A., Tapponnier, P., 2001. New constraints on

the structure, thermochronology, and timing of the Ailao Shan–Red

River Shear Zone, SE Asian. Journal of Geophysical Research 106,

6683–6732.

Miall, A.D., 1977. A review of the braided river depositional environment.

Earth Sciences Review 13, 1–62.

Miall, A.D., 1978. Lithofacies types and vertical profile models in braided

river deposits: a summary. Canadian Society of Petroleum Geologists,

Memoir 5, 597–604.

Miall, A.D., 1985. Architectural-element analysis: a new method of facies

analysis applied to fluvial deposits. Earth Sciences Review 22,

261–308.

Miall, A.D., 2000. Principles of Sedimentary Basin Analysis, Springer,

Berlin, p. 616.

McLaughlin, R.J., Nilsen, T.H., 1982. Neogene non-marine sedimentation

and tectonics in small pull-apart basins of the San Andreas fault system,

Sonoma County, California. Sedimentology 29, 865–877.

Morton, A.C., 1991. Geochemical studies of detrital heavy minerals and

their application to provenance research. Geological Society of London

Special Publication 57, 31–45.

Nam, T.N., Toriumi, M., Itaya, T., 1998. P-T-t paths and post-metamorphic

exhumation of the Day Nui Con Voi shear zone in Vietnam.

Tectonophysics 290, 299–318.

Nemec, W., Steel, R.J., 1984. Alluvial and coastal conglomerates: their

significant features and some comments on gravelly mass-flow deposits.

Canadian Society of Petroleum Geologists, Memoir 10, 1–31.

Nemec, W., Postma, G., 1993. Quaternary alluvial fans in southwestern

Crete: sedimentation processes and geomorphic evolution. Inter-

national Association of Sedimentologists, Special Publications 17,

235–276.

Nhan, T.D., Danh, T., 1975. New results of study on biostratigraphy of


Neogene sediments in East Bac Bo. Research Work on Stratigraphy of

North Viet Nam, Sciences & Technology Publication House Ha Noi,

244–285.

Nilsen, T.H., Sylvester, A.G., 1995. Strike-slip basins. In: Busby, C.J.,

Ingersoll, R.V. (Eds.), Tectonics of Sedimentary Basins, Blackwell,

Cambridge, pp. 425–457.

Pettijohn, F.J., Potter, P.E., Siever, R., 1972. Sand and Sandstone, Springer,

New York, p. 618.

Rangin, C., Klein, M., Roques, D., Le Pichon, X., Trong, L.V., 1995. The

Red River fault system in the Tonkin Gulf, Vietnam. Tectonophysics

243, 209–222.

Ryang, W.H., Chough, S.K., 1999. Alluvial-to-lacustrine systems in a pull-

apart margin: southwestern Eumsung Basin (Cretaceous), Korea.

Sedimentary Geology 127, 31–47.

Steel, R.J., 1988. Coarsening-upward and skewed fan bodies: symptoms of

strike-slip and transfer fault movement in sedimentary basins. In:

Nemec, W., Steel, R.J. (Eds.), Fan Deltas: Sedimentology and Tectonic

Settings, Blackie, Glasgow, pp. 75–83.

Tapponnier, P., Peltzer, G., Armijo, R., 1986. On the mechanics of the

collision between India and Asia. Geological Society. Special

Publication, London 19, 115–157.

Tapponnier, P., Lacassin, R., Leloup, P.H., Scharer, U., Dalai, Z.,

Xiaohan, L., Scharer, U., Dalai, Z., Xiaohan, L., Liangshang, Z.,

Jiayou, Z., 1990. The Ailao Shan/Red River metamorphic belt:

Tertiary left-lateral shear between Indochina and South China.

Nature 343, 431–437.

Tham, L.D., 1998. Stratigraphy in the south of Red River Basin and its

hydrocarbon indications. Petrovietnam Review 1, 24–41.

Tortosa, A., Palomares, M., Arribas, J., 1991. Quartz grain types in

Holocene deposits from the Spanish Central System: some problems in

provenance analysis. Geological Society of London. Special Publi-

cation 57, 47–54.

Tri, T.V. (Ed.), 1973. Geological Map of Vietnam (the North Part). 1:1,000,

000. Geological Research Expedition No. 45, Hanoi.

Vincent, S.J., 2001. The Sis palaeovalley: a record of proximal fluvial

sedimentation and drainage basin development in response to Pyrenean

mountain building. Sedimentology 48, 1235–1276.

Wang, P.L., Lo, Ch.H., Chung, T.Y., Lee, Ch.Y., Thang, T.V., 2000. Onset

timing of left-lateral movement along the Ailao Shan–Red River Shear

Zone: 40Ar/39Ar dating constraint from the Nam Dinh Area, north-

eastern Vietnam. Journal of Asian Earth Sciences 18, 281–292.

Wysocka, A., Cuong, N.C., Swierczewska, A., Pha, P.D., Huyen, V.N.,

2001. Neogene alluvial deposits from the strike-slip Lo River Basin

(Red River Fault Zone), northern Vietnam. In: Wortmann, U.G., Funk,

H. (Eds.), Abstracts and Programme of IAS 2001, 21st Meeting, Davos,

pp. 43–43.

Wysocka, A., Swierczewska, A., Cuong, N.C., Phan, P.D., Huyen, V.N.,

2003. Some remarks on the Neogene alluvial deposits from the Lo River

Basin (northern Vietnam). Petrovietnam Review 4, in press.

Yem, N.T., 1985. Recent movements and recent fissures of the Red River

trough and neighbouring regions. Final Report of National Scientific

Project No.: 48.02.03. Institute of Earth Sciences, National Center for

Natural Science & Technology, Hanoi (in Vietnamese).

Zielinski, T., 1997. Cyclicity of braided river alluvium. Prace Naukowe

Uniwersytetu Slaskiego 1644, 68–119.in Polish with English summary.


Alluvial deposits from the strike-slip fault Lo River Basin (Oligocene/Miocene), Red River Fault Zone, north-western Vietnam

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