Sequence stratigraphy of Quaternary depositions on the land and at the contineental shelf of Vietnam

The sequence s tratigra phy units o f the Quateniary scdimcnts at Ihc C ontinental shclf o f Victnani have been compared wiUi tlie lilhofacics and depositional cyclcs in[r]

VNU Journal of Science, Earth Sciences 25 (2009) 32-39

Sequence stratigraphy o f Q uatem ary d epositions on the

land and at the Continental s h e lf o f V ietnam

Tran Nghi*, Dinh Xuan Thanh, Tran Thi Thanh Nhan, Nguyen Dinh Thai

C ollege o f Science, VNU

Rcccivcd 8 April 2009; receivcd in revised form 14 April 2009

A b stract The sequence s tratigra phy units o f the Quateniary scdimcnts at Ihc C ontinental shclf o f

Victnani have been compared wiUi tlie lilhofacics and depositional cyclcs in relation to sea level

changcs During the rcgrcssion phases corrcsponding to the lovvstand systcms tract has bciiig

formed the alluvial lithofacies, shelf dcltaic complcx and sliclf cdge fans complcx T h e maximum

regression remarkcd by crosion boundaries has correspondcd with thc lowstand sca ỉevel

charactcrizcd by llie slopc fan tiưbiditte complex The transgrcssion phase has lcađcd to form thc

ravinemcnt surfaccs and Ihc transgrcssivc systcms ưact dcposits for thc end o f cach scquencc

(depositional cycle)

Keywords: Lowstand sca lcvcl; Higlistaiid sca lcvcl; Lowstaiid system tract; Traiisgrcssivc system

Ưact; Highstand systcm ưact; Deep watcr turbidite; Progradation; Hcaling phasc

1 I n tr o d u c tio n

S o far, th e Q u a te m a ry stratigraphy,

lith o ía c ie s - p aleo g eo g rap h y , sea b o tto m

sed im en ts, d ep o sitio n al cycles in re la tio n to sea

lev el ch ang es an d tecto n ic m o v e m e n t, have

b e e n c a rrie d o u t by T ra n N ghi, T rin h T h e H ieu,

N g u y en B ieu (1991 -2 0 0 8 )7

T h e types o f d ata u sed for analysis are

b a se d o n th e follo w in g p rin cip les:

- T h e lithologic com p ositio n, thick ness o f

Q u a te m a ry form ations in the Continental s h e lf

o f V ie tn a m are re la te d w ith the sea level

ch an g es an d tecton ic m o vem ents

- T h e Q u atem ary sed im en ts h av e cyclic

co m p o sitio n (g ran u lo m etry , n iineralog y,

p etro lo g y , g eo ch em istry , env iron m ental

g eo ch e m istry , esp ecially litho íacies

asso ciatio n s) T h e b o u n d aries o f cycles have

* Corresponding author Tel.: 84-4-38542489

E-mail: ttanngbi@vnu.edu.vn

b een d iv id ed b a s e d o n ílu v ia l ero sio n su rface o f transg resssiv e s y ste m tra c t (V inh Phuc

ío rm atio n ) w as ty p ically rem ark ed b y the

sp otted yellovv - re d lateritized

- T he p rin c ip le s o f the s e a lev el ílu ctu atio n

d u ring Q u a te m a ry p e rio d are the o ld er the

sh o relin e (m a rin e te rra ces) th e hig h er it is ( if it

is o n land) a n d th e d e e p e r it is ( i f it is a t the sea bottom )

2 S e q u e n c e s t r a t i g r a p h y o f Q u a te r n a r y

s e d im e n ts

2.1 L o w er P le isto c e n e se d im e n ts ( Q / )

hì fact th e lo w e r P leisto cen e sedim ents

( Q i1) has co rre sp o n d e d w ith a sequence

b o u n d e d b y e ro s io n ílu v ia l su rface a t the base

an d m arin e A ooding su rfa c e on the top U pw ard the section o f a sequence there are 3 system s tract

L o w sta n d sy stem s tra c t (L S T ) (fig 1,2)

T N ghi et a i / V N U ]ourỉial o f Science, Earth Sciences 25 (2009) 32-39 33

(• 'O O O iu ■> -3S O O U ) c o i i M p o u í U v i i i i P t u i a í d a o a l

CV>Mltiu* oí Eoily I1«-is«v*.eur* n<Ị(iev\tou

( O O O O u i - > • ' S O Q m i c « » r i * n » > u « l S ’ - M i l i G u u * g lM - i iỉ

C o ỉ K i i i u r o í k U 4 d l f r ! < - n f o c < - i i i - i r a i - v ù o u

4-lf>OOui -> -I 5(Xku>C0iiM|«M»<U wiih Miudrl piMtTt

C o m i l i u r * o / M i d d i * n r i u o c t t n - M-.KIOVŨOQ

<~4 0 0 m -N - 5 0 0 m ) d M M > i | » u 1s V - I ih k m g l a t i a l

C o * k d i i i f o l L * í i 1 * t t f o c e o t f f t > g i « t u o u

4 - 2 0 G m - - u x > m j v i i i t \ V n u u l

C u m i I i o h I» f L « u * n n u i c M R i r Ị i i r k ú n a

<•100111 < 1 2 0 m ) o o u n p c tQ iK ^ » u » W u m i 2 x l.» 'c d

A < u í r o l ( ( h i s i l i o r o l P l i u h i ỉ u I d u u ^ i m ú d q ( - 5 0 m - * (f k t ù

A ư r i ^ ỉ l c ^ t r l u i í c*f F t a d n n u tiau v jin * » iả íH i i - 2 5 w -í - H)|U>

Fig 1 Schema o f aiiciait shorclines iii

Quatemary pcriod

Ancient sliorelincs at Ihe C o n tin e n ta l shelf

Ancient shoreline at the 2000m dcep (dala

estigated by Atalant ship, 1995)

34 T N ghi et al. / VNU Ịoum al o f Science, Earth Sciences 25 (2009) 32-39

The river ch ann cl co b b le layer corresponds

w ith the reg ressio n p h a se (sea level fall)

inA uenced b y G un z G lacial o v erly in g the

cobble form ation is a flood p la in silt - clay

layer In fact low stand sy stem s trac t have b een

v aried from th c m ain lan d to the C o n t i n e n t a l

s h e lf area follo w in g to m o v in g o f older

sh o relin e d urin g sea level fall ( f ig l, ta b l)

A nyw ay the g ranu lo m etric v ariatio n upvvard

fro m the b ase to the top o f L S T situ ated on land

as w ell as in the sea level is fin er g rain size

For the lo w stan d sea level, on the

Continental s h e lf o f V ietn am , the sh o relin e has

been fo u n d at the depth o f 2 0 0 0 - 2500m T he

sea b o tto m sed im en ts h av e co m p o sed o f

vo lcan ic ro ck ử a g m e n t, g ra v e ls, sand s and lim c, clay s o lic ic m u d s, w h ic h have been

co n stitu ated b y tu rb id ite c o n stru c tu re (fíg 1,2)

- T ra n sg re ssiv e sy stem s tr a c t (T ST )

T ran sg ressiv e sy stem s tra c t has com posed

o f deltaic, shallovv sea silty - clay íacies

d istrib u tin g fo llo w in g th e m o v e m e n t o f older

sh o relin e fro m 15 0 0 m d eep w ater (present deep) to Coastal p la in s In th e Continental s h e lf area it is clear to d is c o v e r th e b o u n d a ry betw een losvstand s y ste m s trac t an d transgressive system s tract [1 ,2 ] T h e b ase o f transgressive system s tract se d im e n ts co m p o sed o f coarse

g rain size c o m p o sitio n o f ro u n d e d fragm ents o f laterite, q u artzs a n d rocks

Tablc 1 Comparation o f cronosưatigrapliy, scqucnce stratigraphy lithological units, dcpositional cycles and

lithofacies o f Quatemary dcposits o f Vicữiani

T N g h i ct n i / VNU lourỉĩal o f Science, Earth Sciences 25 (2009) 32-39 35

(Alluvial cơanse

grain siz e ) E r o s io n

l o w s t a n d s u r í a c e

ỊS h e lỉ delỉa lowstancl)

R a v i n e m e n t

t r a n s g e s s i v e

s u r í a c e

(D e e p w oter

tưrbỉơiỉeì

Fig 2 Scqucncc stratigraphy units

The u pper p a rt o f the tran sg ressiv e system s

tract is lagoonal greenish g rey clay lay er at the

Red river plain, C u u L o n g riv er p lain and

Central p la in s c o rr e s p o n d in g w ith th e h ig h s ta n d

sea level stage

2.2 M iddle P leistocen e se d im e n ts (Q i 2)

- L ow stan d sy stem s tra c t: D uring th e sea

level fall m ay be in ílu e n c e d b y the M inđel -

Riss glaciations O n th e Coastal plain s o ccurred

a regression p h a se m a k in g a n ílu v ia l erosion

su ría c e w ith riv er chann el fĩlle d b y co a rse grain

size sedim ents T h is lu ico n ío rm ity co n tin u es to

develop as lon g as rela tiv e s e a level continues

to fall a n d th e C oastal o n la p re m a in s a z o n e o f

non-depo sition [4] (fig 1,2,3)

- T h e M id dle P leisto cen e cobbles and

gravels o f allu v ial facies b e lo n g in g to lo w stan d

sea level o v erlie w ith u n co n fo rn iity the

highstand system s trac t dep osits o f low er

Pleistocene sequence

- T ran sg ressiv e sy stem s tra c t deposits w ere

characterized b y th e c e m e n t grey silty clay o f

estuary facies a t the R ed rivcr, C u u Long river plain s an d sa n d y b a rs íòrm ation A ccording to the results o f q u a rtz th erm o lu m in ecen t dating o f

th e sam p le c o lle c te d at Suoi T ien, M ui Ne, Phan T h iet sh o w s th at the ab solu te age o f

M iddle P leisto cen e re d s a n d is o f m ore than

204 K a (T ran N g hi, 1997, 1999)

- H ig h stan d sy stem s trac t d q ỉo sits havc

b een fo u n d th e m argine p la in terrace at the 2 0 -

2 5 m high a b o v e p re se n t sea lcvcl w hich

co m p o sed o f d eltaic grey silty san d íacies

2.3 U pper P leisto ce n e seclim ents (Q iiữ)

- Lovvstand sy stem s ư a c t dqDosits:

T h e b eg in n in g o f th e la te P leistocene epoch

w as co rresp o n d ed w ith reg ressive phases

in ílu cn ced b y thc g laciatio n s o f W iirm 1 T he ero d ed allu v ial su ría c e filled b y coarse grain size seđ im en t has b een c o ư e sp o n d e d w ith

lo w stan d sea lev el sh o w in g a t the depth o f 2 00 -

3 0 0 ra T h is is an an cien t sh o relin e zone

ch aracterized b y lith ofacies an d g eo m orphology (fig 1,3)

36 T N ghi ct nỉ. / V N U Ịournal o f Science, Enrtlì Sciences 25 (2009) 32-39

•s? * > <> G c n e r a i / c d siratig rap hv ( T r a n N g h i , 2 0 (W )

c y $ ệ L l J L _

IIYD RO GK O LO íiY

Pluodpbin pcatã Mlt.N and clny DiMnkiiOẠ Aquicluiỉe clntnncl

Sand* w ỉih pcbblcs at ba>c Aquitier

C‘ Ia> MltN

.inj \jital' Yliinnc '

d a y loycr S.»n«!s itihl silts

Ku-h m TOt Aquictudc Ai|uit«cr p.inlco MÚI M aj»t •K't|uicliuli‘

? M aim e cU \

Sands Aquilicr

1 h ai Binh

F oinciiion

11.111 lominium

í PPFR

IU HíKTl-.Nl.

I PPUR

Pl I l s r < M '|- \ f

I ()W h R -HOI (K FNI

V inh Phnc Ponnatum

l PPFR

Pl i ISTO C! \ F

0,

Siuid* Jiid

u tih

t T M uioruqutncr coniains

tecviie clasi

H a Noi

I ưriiutm n

M ID D I.r

IM I ivroa NI Ọ

SaiHỈs and

gn » c ụ « i * A i r Iltin clay

lcn*c«

Prc - Ọ u aicm an hcdrock

Aquicliiik'

Lc Chi I.OWHR

P IIIS T O C I NI

Fig 3 Sequence stratigraphy units ofQ uatem ary deposits at the Red river

- T ran sg ressiv e sy stem s tract deposits:

A fter W iirm 1 (Q i 'a) th e re vvas a period o f

very stro n g tran sg ressio n o f g lo b al ch ara cter

th at vvas n am ed “V in h Plìuc” tran sg ressio n

T hese sedim ents w ere clìaracterized by the

deltaic svvamp m ud facies (lo w p art) and the

lagoonal shallow sea silty clay facies ex ten d in g

from the Continental s h e lf to th e m ainland

Coastal plains [3] (fig.4)

II : ;

Fig 4 Seismic profiỉe showing íluvial eroded suríầce (lowstand sea level) and transgressive

systems tract

T N ghi et n i ì V N U ịournal o f Science, Earth Sciences 25 (2009) 32-39 37

C o rresp o n d in g to the ab o ve m ention ed form the san d y bars and T o m b o lo associated lith o ia cies at the C entral V ietnam o ccu rred to vvith b ay -lag o o n al m ud facies [4] (fĩg.5)

V ietnam highland

TuyPJiong

Sample site for TL đating

Fig 5 The section o f sandy sequences

38 T N $ h i ct a i / V N U Ịournaì o f Science, Earth Sciences 25 (2009) 32-39

H ig h stan d sy ste m s trac t d cp o sits o v erly in g

o n the top o f th e m a rin e ílo o d in g su rface

co m p o se d o f th e d eltaic s a n d - silty c la y \vhich

has b e e n d ep o site d to g e th e r w ith se a level fall

2.4 The u p p e r P le ỉs to c e n e to L o \ver-M ỉd d le

H o lo cen e d e p o s its ( Q ? b - Q : 2)

T h is ep o ch w as s u b je c te d to 2 s e a level

ch an g e s ph ases: rc g re ssio n in ílu e n c e d b y W ủ rm

2 g laciatio n a n d F la d ria n T ra n sg re ssio n

- L o w stan d sy stem s tra c t d e p o site s (Q i3b)

A t th e C ontinental s h e lf o f V ie tn a m m ay be

íò u n d o ld sh o re lin e z o n e a t th e d e p th o f 100 -

2 0 0 m (e q u iv a le n t to the la st g la c ia tio n s - W ủ rm

2) T h is p erio d th e m a in la n d h a s b e e n ex p an d ed

to th e m a in s u ría c e o f m o d e rn C ontinental s h e lf

o f V ie tn a m T h e co a rse g ra in s iz e sed im e n ts o f

alluvial lo w sta n d sy stem s trac t w e rc d istrib u ted

alo n g the riv e r valley s M c a n w h ilc , the others

sid cs it o c c u rre d th e Nvcathering fo r the

in íiltra tio n m e c h a n ism o f th e g ro u n d w ater

actio n cau sin g th c m o tlcy c o lo r o f “V in h P h uc”

tran sg ressiv e sy stem s tract

- T ra n sg re ssiv c s y ste m s tra c t o f lo w er -

m id d le H o lo c e n e (Q2 )

T h e tra n sg re ssiv e p h a se ‘T la n d r ia n ”

elo n g ated fro m th e lovvstand s e a lc v e l o f 100 -

120m deep to th e h ig h sta n d s e a lev el o f 4.5 -

5 Om h ig h is c h a ra c te riz e d b y tw o m ain

lith o ía c ie s c o m p le x e s a s s o c ia tin g \vith each

o th er in tim e a n d s p a c e Coastal svvamp m u d

facies (lo w er p a r t) a n d lim a n g re e n ish g re y clay

facies (u p p e r p art)

D u rin g th e h ig h sta n d s e a lev el w h ic h m ay

b e ío u n d sea lev el n o tc h e s a t th e lim e sto n e

k liffs fro m N in h B inh, Q u a n g B inh, H a Long

b ay areas C o rre sp o n d in g to th e m id d le

H o lo cen e h ig h sta n d se a le v c l in Coastal z o n c o f

C e n tra l V ietn am has d c v e lo p e d th e w h ite sandy

b a rs asso c ia te d \vith th e la g o o n a l n iu d facies as

w ell as the w hite san d y T o m b o lo s associated

w ith the b ay clay m ud facies

- H igh stan d sy stem s tract o f upper

H o locene (Q :3)

In general, d u rin g late H olocene perio d after the M iddle H o lo cen e m axim um transg ressio n th e d eltaic p la in s w ere expanded tog ether w ith th e sea lev cl fall

In Coastal o f Central V ie tn a m a t the sam e tim e w ere fo rm ed the san d d u n e s d cposited by the w ave activities

In the p re se n t tra n sg re ssio n phase (from 1500a B-P to present) w ith a rate o f 1 - 2 m m a the Q u atem ary sed im en ts in th e Coastal zone have b een co n tin u o u sly c h a n g e d in tw o ways:

p ro g radatio nal sedim en ts a n d erosion M ost o f the co ast line o f V ietn am is b c in g eroded except the co ast o f the R ed river, C u u long river and

W e s te m co ast o f C a M au pcninsula vvhere strong sed im en tatio n is g o in g on Meanvvhile, the B ach D an g an d S oai Rap cstuaries are being destroy ed b y the risin g sca level, deficit o f sedim ents an d tcctonic su bsidence

3 C o n c lu sio n s a n d d is c u s s io n s

litho stratig raplìic data interpretation, sedim entary cy cle an aly sis a n d other m ethods have allovved to delin eate seq u e n c e stratigraphy units o f th e Q u a te m a ry sed im en ts o f the Continental s h e lf o f V ie tn a m vvhich co m posed

o f 5 seq u en ces and 15 p a ra se q u e n c e sets

T he lo w er P leisto cen e ( Q |l)

T he low cr p a rt o f M id dle P leistocene (Q i2a)

T he u p p er p a rt o f M id dle P leistocene (Q i: í )

T he lovver p a rt o f U pper Pleistocene (Q i3a)

T he u p p er p a rt o f U p p er Pleistocene to upper H olocene (Q i3b - Q :3)

/' N g h i et a i / V N U Ịoum aỉ o f Science, Earth Sciences 25 (2009) 32-39 39

T h e E arth sequence co rresp o n d in g to a

sed im en tary cy cle has co m p o sed o f 3

p arasequ ence sets and 25 p arascq u en ces in w ith

a p araseq uen ce w as b e in g equ ivalent to a

lithofacies group

2 T h ere are o f 7 o lđ cr sh o relin es a t the

d iffere n t depths: 2 0 0 0 - 2 5 0 0 m ( Q |') ; 1000 -

(Q ,3a); 100 - 12 0 m ( Q ,,b); 50 - 6 0 m ( Q :') ; 25 -

3 0 m ( Q ;i : )

3 T he lo\vstand sy stem s tract coinp rise the

in c ised valley fill o f th e riv er channel,

Continental s h e lf ed g c lo \v stan d dclta com plex

and deep - vvater tu rb id ite o f 1500 - 2000m

deep a t the C en tral V ie tn a n i

4 T he p ro cess o f fo rced regression and

tran sg ressio n phase d q )o s its th at đeveloped

se a w a rd o f the last c lin o íb rm o f the lovvstand

p ro g rad atio n al units

R e fe re n c e s

[1] G.p Allen, H w Posamentier, Sequence

Síraíigraphy and facies modeỉ o f an incised

Sequence stratigraphy workshop-concepts and applications - January 18-20, 1995, Hanoi, Vietnam, 1995

[2] H.w Posamcntier, D.p James, An overview o f

sequence - stratigraphy concepts: uses and

a b u se s, S p c c p u b ls int A ss S eđ im en t, 1993

18.3-18

[3] D.M Duc, T Nghi et al., Sediment distribution

a n d tra n sp o rl a t th e n e a rsh o re zo n e o f th e Red

riv c r d e lta N o rth e rn V ie ln a m , J o u m a l o f A sia n

Earth Sciences 29 (2007) 558-565.

[4] Colin V Murray-WallaCL\ Bnan G Jones, Tran Nghi, David M Price, Vu Van Vinh, Trinh Nguycn Tinh, Gcrald c Nanson,

T h c m io lu n iin c s c c n c e a g e s for a rew o rk ed Coastal barricr, soulheastem Vietnam: a

prcliminary report, Journal o f Asian Earih

Sciences 20 (2002) 535-548.