rift basin resume

8/12/2019 Rift Basin Resume

1/39

3.3. Tectonics of Rifting and Drifting

Pangea Breakup

3.3.1. Rift Basin Architecture and Evolution

Roy W. Schlische & Martha Oliver Withjack Department of Geological Sciences, Rutgers

niversity, !iscata"ay, #$ %'()%** .S.+.

Rift asins have een increasingly the focus of research in tectonics, structural geology,

an- asin analysis. he reasons for this interest inclu-e/

012 Rift asins are foun- on all passive 0+tlantic 3 type2 continental margins an- provi-e a

recor- of the early stages of 0super2continental reakup.

042 he architecture of these asins an- the asin fill are strongly influence- y the -isplacement

geometry on the oun-ing normal fault systems 0e.g., Gison et al., 1552. hus, aspects of the

evolution of these fault systems, inclu-ing their nucleation, propagation an- linkage, can e

e6tracte- from the se-imentary recor-.

072 Many mo-ern an- ancient e6tensional asins contain lacustrine -eposits 0e.g., 8at9, 155%2

that are sensitive recor-ers of climate. Milankovitch cycles 0e.g., Olsen an- 8ent, 15552 recor-e-

in these strata provi-e a :uantitative test of the pre-ictions of asin)filling mo-els 0e.g.,

Schlische an- Olsen, 155%2 that can, in turn, e use- to infer aspects of crustal rheology -uring

rifting 0e.g., ;ontreras et al., 155ra9ilian rift asins2.


2/39

his section provi-es a rief overvie" of the rift asins relate- to !angean reakup,

especially those along the central +tlantic margin 0e.g., Olsen, 155


3/39

Figure 3.3.1.1.Geometry of a simple half graen.

0a2 Map)vie" geometry.

02 Geometry along a cross section oriente- perpen-icular to the oun-ary fault, sho"ing "e-ge)

shape- asin in "hich synrift strata e6hiit a fanning geometry, thicken to"ar- the oun-ary

fault, an- onlap prerift rocks.

0c2 Geometry along a cross section oriente- parallel to the oun-ary fault, sho"ing syncline)

shape- asin in "hich synrift strata thin a"ay from the center of the asin an- onlap prerift

rocks.

he half)graen geometry -escrie- aove is -irectly controlle- y the -eformation

0-isplacement2 fiel- surroun-ing the oun-ary fault system 0Gison et al., 155@ Schlische, 1551,

155'@ Schlische an- +n-ers, 155*@ ;ontreras et al. 155


4/39


5/39

0a2 !erspective -iagram efore 0left2 an- after faulting sho"ing ho" normal faulting uplifts the

foot"all lock an- pro-uces susi-ence in the hanging)"all lock. he yello" -ashe- line

sho"s the outer limit of hanging)"all susi-ence an- marks the e-ge of the asin. Displacement

is a ma6imum at the center of the fault 0only the right half of the fault is sho"n2 an- -ecreases

to"ar- the fault tip.

02 raverse section efore faulting 0left2 an- after faulting an- se-imentation sho"ing

foot"all uplift an- hanging)"all susi-ence. he latter pro-uces a "e-ge)shape- asin 0half

graen2.


6/39

Figure 3.3.1.3.Simple filling mo-el for a gro"ing half)graen asin sho"n in map vie"

0stages 1)(2, longitu-inal cross section 0stages 1)'2, an- transverse cross section 0stages 1)(2.

Dashe- line represents lake level. he relationship et"een capacity an- se-iment supply

-etermines "hether se-imentation is fluvial or lacustrine. Aor lacustrine se-imentation, the

relationship et"een "ater volume an- e6cess capacity -etermines the lake -epth. Mo-ifie-

from Schlische an- +n-ers 0155*2.


7/39

he simple structural architecture -escrie- aove may e complicate- y asin

inversion, in "hich a contractional phase follo"s the e6tensional phase 0e.g., >uchanan an-

>uchanan, 155'2. ypical inversion structures inclu-e normal faults reactivate- as reverse faults,

ne"ly forme- reverse an- thrust faults, an- fol-s 0Aig. 7.7.1.(, 7.7.1.'2. >asin inversion occurs in

a variety of tectonic environments 0e.g., >uchanan an- >uchanan, 155'2, inclu-ing several

passive margins relate- to the reakup of !angea 0e.g., DorC an- un-in, 155*@ Eagnes et al.,

155@ Withjack et al., 155', 155@ Bill et al., 155'@ Withjack & Fisensta-t, 15552. he causes of

inversion on these passive margins is not "ell un-erstoo-. Section (.4.1 -escries ho" coring, in

comination "ith other metho-s, may help further our un-erstan-ing of asin inversion on

passive margins.

Figure 3.3.1.!. F6amples of positive inversion structures.

a2 ;ross section across part of Sun-a arc. During inversion, normal faults ecame reverse faults,

pro-ucing synclines an- anticlines "ith harpoon geometries 0after etou9ey, 155%2.


8/39

2 ?nterprete- line -ra"ings 0"ith 7/1 an- 1/1 vertical e6aggeration2 of +GSO ine 11%)

14 from F6mouth su)asin, #W Shelf +ustralia 0after Withjack & Fisensta-t, 15552. During

Miocene inversion, -eep)seate- normal faults ecame reverse faults. ?n response, gentle

monoclines forme- in the shallo", postrift strata.


9/39

Figure 3.3.1.". F6perimental mo-els of inversion structures. ;ross sections through three clay

mo-els sho"ing -evelopment of inversion structures 0after Fisensta-t an- Withjack, 155'2. ?n

each mo-el, a clay layer 0"ith colore- su)layers2 covere- t"o overlapping metal plates.

Movement of the lo"er plate create- e6tension or shortening. hin clay layers are prerift@ thick

clay layers are synrift@ top)most layer is postrift an- pre)inversion. op section sho"s mo-el

"ith e6tension an- no shortening@ a half graen containing very gently -ipping synrift units is

present. he mi--le section sho"s mo-el "ith e6tension follo"e- y minor shortening@ a sutle

anticline has forme- in the half graen, an- is associate- "ith minor steepening of the -ip of

synrift layers. >ottom section sho"s mo-el "ith e6tension follo"e- y major shortening. he

anticline in the half graen is more prominent, an- is associate- "ith significant steepening of

the -ip of synrift strata. #e" reverse faults have forme- in the prerift layers. +lthough the

inversion is ovious in this mo-el, erosion of material -o"n to the level of the re- line "oul-

remove the most ovious evi-ence of inversion in the half graen. Aurthermore, the prominent

reverse faults cutting the prerift units coul- e interprete- to in-icate prerift contractional

-eformation, as is common in the rift 9ones relate- to the reakup of !angea.

Stratigraphic Architecture

#umerous non)marine rift asins of varie- geography an- geologic age share a

remarkaly similar stratigraphic architecture 0amiase, 155%@ Schlische an- Olsen, 155%@ Aig.

7.7.1.*2. 8no"n as a tripartite stratigraphy, the section egins "ith asin)"i-e fluvial -eposits

overlain y a relatively arupt -eepening)up"ar- lacustrine succession overlain y a gra-ual

shallo"ing)up"ar- lacustrine an- fluvial succession. he key to un-erstan-ing the significance

of this tripartite stratigraphy rests in the relationships among asin capacity an- se-iment an-

"ater supply 0Schlische an- Olsen, 155%@ ;arroll an- >ohacs, 15552. ectonics creates

accommo-ation space or asin capacity. Se-iment supply -etermines ho" much of that asin

capacity is fille- an- "hether or not lake systems are possile 0Aigure 7.7.1.


10/39


11/39

shallo")"ater lacustrine an- fluvial -eposits. he southern asins -o not contain S)?E. S)?

is only recogni9e- in the Aun-y asin an- may or may not e a synrift -eposit. Where S)?? is

recogni9e-, a significant unconformity 0in terms of missing time2 commonly separates it from

S)???. Mo-ifie- from Olsen 0155


12/39

transition may result from an increase in asin capacity an-Hor a -ecrease in se-iment supply.

he shallo")"ater lacustrine to -eep)"ater lacustrine transition may result from an increase in

asin capacity, a -ecrease in se-iment)supply, an-Hor increase in the availale volume of "ater.

he -eep)"ater lacustrine to shallo")"ater lacustrine transition may result from a -ecrease or an

increase in asin capacity 0-epen-ing on the geometry of the asin=s e6cess capacity2, an increase

in the se-iment supply, an-Hor -ecrease in the availale volume of "ater. Bo" -o "e go aout

choosing the more likely interpretationI ?nterestingly, all of the major stratigraphic transitions

can e e6plaine- y an increase in asin capacity, for "hich a simple asin)filling mo-el is

sho"n in Aigure 7.7.1.7. Other asin filling mo-els are -escrie- y amiase 0155%2, Smoot

015512, an- amiase an- >os"orth 0155'2. +s -iscusse- in Section 7.7.7, long cores from rift

asins, comine- "ith asin mo-eling 0e.g., ;ontreras et al., 155


13/39

Tectonostratigraphic Packages and Basin Evolution

Olsen 0155


14/39

Figure 3.3.1.+. Stages in the evolution of a rift asin.

0a2 Farly rifting associate- "ith several minor, relatively isolate- normal faults.

02 Mature rifting "ith through)going oun-ary fault 9one, "i-esprea- -eposition,

an- foot"all uplift an- erosion.

S)??? an- S)?E "ere -eposite- in much larger asins or suasins than "as S)??, an-

the unconformity et"een them is small to non)e6istent 0Olsen, 155


15/39

;oring, fiel- analysis, an- seismic)reflection profiles of synrift an- imme-iately overlying

postrift -eposits an- the structures forme- in them, are necessary to clarify the important events

occurring at the rift)-rift transition.

he inferre- -iachronous initiation of seafloor sprea-ing along the present)-ay margin of

the central #orth +merica Ocean is part of larger tren- that reflects the progressive

-ismemerment of !angea. +s the #orth +tlantic Ocean continue- to -evelop, seafloor

sprea-ing propagate- north"ar-. Aor e6ample, seafloor sprea-ing et"een the Gran- >anks an-

south"estern Furope egan -uring the Farly ;retaceous 0e.g., Srivastava an- apscott, 15*2@

seafloor sprea-ing et"een ara-or an- "estern Greenlan- egan -uring the early ertiary

0anomaly 4asin ?nversion/ Geological Society of

on-on Special !ulication , '5* p.

;arroll, +.R., an- >ohacs, 8.M., 1555, Stratigraphic classification of ancient lakes/ >alancing

tectonic an- climatic controls/ Geology, v. 4


16/39

;ontreras, $., Schol9, ;. B., 8ing, G. ;. !., 155uchanan, $. G., an- >uchanan, !. G., e-s., 155', >asin ?nversion/ Geological Society of

on-on Special !ulication , p. 115)17*.

Ga"thorpe, R.., Sharp, ?., n-erhill, $.R., an- Gupta, S., 155ass asin, SF +ustralia, in >uchanan, $.G., an- >uchanan, !.G.,

e-s., 155', >asin ?nversion/ Geological Society of on-on Special !ulication , p. '4')'(.

Bin9, 8., Fl-holm, O., >lock, M., an- Skogsei-, $., 1557, Fvolution of #orth +tlantic volcanic

continental margins, in !arker, $. R., e-., !etroleum Geology of #orth"est Furope, !rocee-ings

of the (th ;onference/ Geological Society of on-on, v. 4, p. 5%1)517.


17/39

8at9, >. $., e-., 155%, acustrine asin e6ploration))case stu-ies an- mo-ern analogs/ ++!G

Memoir '%, 7(% p.

amiase, $.$., 155%, + mo-el for tectonic control of lacustrine stratigraphic se:uences in

continental rift asins, in 8at9, >.$., e-., acustrine F6ploration/ ;ase Stu-ies an- Mo-ern

+nalogues/ ++!G Memoir '%, p. 4*')4os"orth, W., 155', Structural controls on se-imentation in continental

rifts, in amiase, $.$., e-., By-rocaron haitat in rift asins/ Geological Society Special

!ulication %, p. 11ulletin, v. 7, p.

*17)*7(.

Oh, $., +ustin, $. +., $r., !hillips, $. D., ;offin, M. A., an- Stoffa, !. ., 155', Sea"ar-)-ipping

reflectors offshore the southeastern nite- States/ Seismic evi-ence for e6tensive volcanism

accompanying se:uential formation of the ;arolina trough an- >lake !lateau asin/ Geology, v.

47, p. 5)14.

Olsen, !. F., Schlische, R. W., an- Ae-osh, M. S., 155*, '% kyr -uration of the Farly $urassic

floo- asalt event in eastern #orth +merica estimate- using Milankovitch cyclostratigraphy, in

Morales, M., e-., he ;ontinental $urassic/ Museum of #orthern +ri9ona >ulletin *%, p. 11)44.

Olsen, !. F., 155


18/39

Rosen-ahl, >. R., 15ulletin, v. eratan, 8. 8., e-., Reconstructing the

Structural Bistory of >asin an- Range F6tension sing Se-imentology an- Stratigraphy/ GS+

Special !aper 7%7, p. 17)4%7.

Schlische, R. W., an- Olsen, !. F., 155%, Nuantitative filling mo-el for continental e6tensional

asins "ith applications to early Meso9oic rifts of eastern #orth +merica/ $ournal of Geology, v.

5, p. 17')1''.

Smoot, $. !., 1551, Se-imentary facies an- -epositional environments of early Meso9oic #e"ark

Supergroup asins, eastern #orth +merica/ !alaeogeography, !alaeoclimatology, !alaeoecology,

v. (, p. 7*5)(47.

Srivastava, S. !., an- apscott, ;. R., 15*, !late kinematics of the #orth +tlantic, in Eogt, !.

R., an- ucholke, >. F., e-s., he Geology of #orth +merica, v. M., he Western #orth +tlantic

Region/ Geological Society of +merica, p. 7


19/39

al"ani, M., an- Fl-holm, O., 15ulletin, v. ulletin, v. 4, p. 1


20/39

-ntroduction

he continental shelf of Eietnam comprises several major ertiary

asins, of "hich the petroleum potential has een confirme- inclu-ing Song

Bong >asin, !hu 8hanh >asin, ;uu ong >asin, #am ;on Son >asin an-

Malay)ho ;hu >asin.

Recent stu-ies in-icate- the estimate- reserves an- resources, oth

onshore an- offshore Eietnam to e 7)( illion cuic metres 0>;M2 of oil an-

gas, comprising %.5)1.4 >;M of oil an- 4.1)4. >;M of natural gas. +out '%oil an- gas prospects have een foun- "ith reserves of appro6imately 7 illions

arrels of oil an- 47 ;A of natural gas. ;ommercial oil has een -iscovere-

an- pro-uce- in ;uu ong, #am ;on Son an- Malay)ho ;hu >asins, "hile

commercial gas is eing pro-uce- in Song Bong an- -evelope- in #am ;on

Son an- Malay)ho ;hu >asins.

;uu ong >asin is no" consi-ere- to e mature, "ith greater than '%P

proaility that more than '%P of the total petroleum in the region has een

-iscovere-, generally covere- y e6tensive seismic gri- an- high -rilling

-ensity. Sumature regions such as Song Bong, #am ;on Son an- Malay)ho

;hu >asins have a greater than '%P proaility that less than '%P of the

region=s total petroleum resources has een -iscovere- "ith me-ium seismic

an- -rilling -ensity. !hu 8hanh >asin an- frontier areas are those "ithout

petroleum -iscoveries, "here seismic coverage is sparse an- "ith fe" "ells

-rille-.

Top

Regional /eological Setting
http://www.ccop.or.th/epf/vietnam/vietnam_petroleum.htmlhttp://www.ccop.or.th/epf/vietnam/vietnam_petroleum.html


21/39

Tectonic Evolution

he Eietnam continental shelf area constitutes a part of a system of

;eno9oic se-imentary asins that lies "ithin a transition 9one from the

continental crust of the ?n-ochina ;raton to the su oceanic crust of the eastern

-eep "ater asins. he asins -evelope- here are rift asins "ith multiphase

history. ectonic evolution of the Fast Eietnam Sea ;eno9oic >asins can e

-ivi-e- into the follo"ing main stages/

1. ate ;retaceous)Focene/ pre rift upliftHinitial rifting phase. he major

tectonic event is the collision of ?n-ia an- Furasia, resulte- in the southeast"ar-

e6trusion in ?n-ochina, represente- y strike)slip movements. ?n ate Focene achange in the sprea-ing -irection in the SF !acific resulte- in the -evelopment

of a ne" #F)SW su-uction 9one.

4. ate Focene)Oligocene/ main rifting phaseHinitial ocean floor

sprea-ing phase. his "as the most po"erful, resulte- in the -evelopment of

most of the main structure elements in the asins. he -ominating style of the

-eformation "as e6tension an- transtensional.

7. Farly)Mi--le Miocene/ regional susi-enceHrene"e- rifting. ?n the

majority of the asins, there happene- a shift from the rift to the thermally

controlle- high)rate susi-ence. Significant tectonic pulses occurre- at the en-

of this perio- marking a major inter asinal inversion event.

(. ate Miocene/ partial inversionHregional susi-ence. During this stage,

the "hole area ecame -ominate- y compression, "hich, in comination "ith

the -e6tral strike)slip fault system east offshore Eietnam, might e the -riving

force for the contemporary asin uplift an- partial inversion in most of the

asins. '. !liocene)!leistocene/ regional susi-enceHrene"e- rifting. he

tectonic activity at that stage "as -iverse in -ifferent asins, from lo" to

mo-erate)amplitu-e -ifferential uplift. he high)rate fault oun-e- susi-ence

in the outer area can e consi-ere- as the rifting activation phase associate-

"ith the sprea-ing of the -eep"ater asins.


22/39

Depositional Evolution

he main regular se-imentation along ?n-ochina margin "ere -efine- y

rate of susi-ence an- structure of the asement, location of large river system

of the South Fast +sia, eustatic sea level changes an- paleoclimate factor. he

asins are characterise- y high se-imentation rates, arupt facies changes,

arupt thickening of se-imentary se:uences over short ranges, numerous

unconformities an- scattere- volcanicHe6trusive activity.

1. !alaeocene)Focene/ se-iments "ith great thickness "ere -eposite- in

the fluvial)lacustrineHcoastal plainH-eltaic con-itions

4. Oligocene/ time of ma6imum -evelopment of the non)marine totransitive -eltaicHcoastal plain con-itions, inclu-ing lacustrine an- estuarine

environments, "hich posses the main source potential in the asins all over the

?n-ochina margin.

7. Farly)Mi--le Miocene/ "ithin the perio-, se-imentation "as

simultaneous "ith a sea level eustatic rise. he rifting cause- a rapi- increase in

susi-ence rate in all the asins, resulte- in the "est"ar- regression of the

-eltaHcoastal plain systems.

(. ate Miocene/ the marine transgressive -eposition continue-, ut its

rate "as re-uce-. he shelf e-ge caronate platforms "ere -eposite- in most of

southern asins.

'. !liocene)!leistocene/ se-iment input increase-, associate- "ith high)

rate of susi-ence in almost all the asins. Rapi- east"ar-s progra-ation of the

shelf e-ge of the asins "ere accompanie- y -eposition of sumarine fan

slope systems.

Location of Tertiary Basins in Vietnam


23/39

Top

Song 0ong Basin

Geological Development

Song Bong >asin, the largest ertiary asin in the continental shelf of

Eietnam, is classifie- as a pull)apart system, fille- up "ith up to 1',%%% m of

Focene to Recent se-iment, evolving in several phases throughout Oligocene to

!liocene times. he onset of the asin=s formation is relate- to the collision of

the ?n-ian su)continent "ith +sia -uring the ate Focene.

eft lateral strike)slip an- pull apart along the Song Bong Aault Qone in

"hich t"o main fault systems forme- the eastern an- "estern limits of its main

-epocentre controlle- the shape of the asin. he Focene)Oligocene marke- the

major rifting phase. Se-imentation "as primarily in fluvio)lacustrine

environment, reflecting the restricte- nature of the asin couple- "ith rapi-

se-iment filling.
http://www.ccop.or.th/epf/vietnam/vietnam_petroleum.htmlhttp://www.ccop.or.th/epf/vietnam/vietnam_petroleum.htmlhttp://www.ccop.or.th/epf/vietnam/vietnam_petroleum.html


24/39

he Farly)Mi--le Miocene "as a :uiescent marine se-imentation perio-.

;aronate -evelopment along shelf oun-ary prolonge- an- acksteppe- in

areas -uring the Mi--le Miocene sea level transgression. hroughout the ate

Miocene to !lio)!leistocene, aun-ant clastic se-iment continue- as a result of

thermal contraction an- susi-ence.

Petroleum System

"o potential source rocks have een i-entifie- in the asin/ Oligocene

lacustrine oil prone shales an- Oligo)Miocene -eltaicHparalic gas)prone

coalsHcoaly shales. Mo-eling results in-icate that most of the asin is mature for

gas 08erogen type ???H??2. !aleogene se-iments are mature for oil only in the

north"estern part an- in some of the half)graen area in the "estern margin of

the asin.

Reservoirs in the asin comprise- pre-ominantly of MioceneHOligocene

clastic se-iments associate- "ith rifting an- suse:uent thermal contraction an-

sag. he caronates inclu-ing caronate uil-)ups an- reefs can e foun- in theasin=s central parts or margins "here uplift has occurre- cause- y listric

faulting. Aracture- asement coul- also e an e6ploration target.

he major trap types in Song Bong asin are rollover fol-s, tilte- fault

locks, asement high an- caronates uil-ups. he -ominant seal in the Song


25/39

Bong >asin is the ertiary seal an- although there is very little regionally

correlatale shale across the asin, local shales forming intraformational seals

are numerous an- appear to e very competent.

Prospectivity

Song Bong >asin is assesse- to contain 1'P of the total hy-rocaron

resources of Eietnam. he major petroleum plays in the Song Bong >asin

inclu-e/

!re)ertiary fracture- granite -rape across asement high locks

OligoceneHMiocene san-stones structure associate- "ith tilte- fault

locks, asement locks or inversion

OligoceneHMiocene san-stones stratigraphic plays 0especially turi-ites2

Mi--le Miocene caronates reef platforms

here are ( petroleum contracts that remaine- in active in the Song Bong

>asin. here is one small pro-ucing fiel-, an- another is eing -evelope- at the

onshore north"estern part of the asin. ?n the southern area, a numer of

significant gas -iscoveries "ere ma-e, ut unfortunately contaminate- y high

;O4 content.

Top

Phu hanh Basin


!hu 8hanh >asin is a present -eep"ater asin. ?t sho"s characteristic rift

structures, "hich elong to the transtensional system -evelope- along the mega

shear 9one at the oun-ary et"een the relatively rigi- continental lock an-

the more moile sprea-ing 9one of the Fast Sea.

he >asin "as forme- -uring the Oligocene to Farly Miocene main


26/39

rifting phase. he -ominant styles of -eformation "ere e6tension an-

transtension. During the Mi--le Miocene, a regional susi-ence took place "ith

a tilting to"ar-s the east that affecte- the entire asin, an- a me-ium rate of

susi-ence "as maintaine-. "o significant transpressional tectonic events

took place -uring the Mi--le Miocene, forming large)si9e flo"er structures in

se-imentary succession an- partial inversion of the asement locks.

During the ate Miocene)Nuaternary, the tectonic activity "as a rifting

phase "ith high rate of susi-ence. he -eepening of the asin "as

accompanie- y minor events of sumarine erosion an- non)-eposition in the

shelf areas. he final susi-ence along the inherite- fault 9ones at the shelf

margin an- a relatively lo" amplitu-e uplift of the "estern part of the inner

shelf gave the asin its present -ay morphostructures.

Petroleum System and Prospectivity

Since there have een no e6ploratory "ells -rille- in the area,

hy-rocaron systems as "ell as characteristics of source rocks, reservoirs an-

cap rocks in the asin have een assesse- on the asis of analogue from

a-jacent asins 0Song Bong, ;uu ong an- #am ;on Son2.

he main source rock is elieve- to e Oligocene an- possile o"er

Miocene an- Focene organic rich shale. here are several types of reservoirs,


27/39

inclu-ing OligoceneHMiocene -eltaic to shallo" marine san-stones@

!aleogeneHMiocene caronates platforms an- reefs, an- possile fracture-

granite. he major trap types are relate- to fault locks associate- "ith

transtensional an- transpressional movements@ ut caronates)in)situ an-

asement are prospective e6ploration targets. !otential seals are Oligocene an-

Miocene claystones an- claystones intercalate- "ith siltstones.

!hu 8hanh >asin is forecaste- to contain 1%P of the total hy-rocaron

resources of Eietnam. he major petroleum plays in the !hu 8hanh >asin

inclu-e/

OligoceneHMiocene shallo" marine san-stones fault locks structures

MioceneH!aleogene caronates reefsHuil-)ups

Miocene stratigraphic plays relate- to pinch)out, sumarine fan,

turi-ites

Aracture-H"eathere- granite pre)ertiary asement locks

Top

2uu &ong Basin


;uu ong >asin, a #F)SW tren-ing e6tensional asin, is forme- "ithin

the Sun-alan- craton at the ate Focene. During the first phase of e6tension,

narro" graens "ere create-. During Farly Oligocene, a roa-er -o"n "arping

pro-uce- a shallo" sag asin. he a6ial 9one of the asin susi-e- rapi-ly

again in the ate Oligocene. + regional unconformity at the en- of the

Oligocene marke- a perio- of uplift.

During the earliest rifting phase 0!alaeocene or Focene2, narro" graens

susi-e- rapi-ly an- "ere fille- "ith great thickness of the non)marine clastics.


28/39

he asin susi-e- roa-ly -uring the Oligocene, an- the fluvial lacustrine

formations "ere -eposite-, containing coarse clastics in its lo"er part an-

gra-es up"ar- into san-, silts an- mu-stones.

During the Mi--le Miocene, a "i-esprea- marine incursion floo-e- the

;uu ong >asin, -epositing the Rotalia mu-stones, a thick shale section, "hich

act as a regional seal. his formation comprises a progra-ing -elta se:uences,

from pro-elta to -elta plain. he pper Miocene an- the overlying !liocene)

Nuaternary se-iments "ere -eposite- -uring transgressiveHregressive cycles of

the mo-ern ;uu ong -elta. hey appear to e controlle- y changes in eustatic

sea level.

Petroleum System

he common source rocks in ;uu ong >asin are Oligocene lacustrine

mu-stones "ith high O;. 8erogen is mainly of type ?H?? 0oil prone2.

he most important reservoir rocks in ;uu ong >asin are "eathere- an-

fracture- granite an- grano-iorite asement "ith more than 1,%%% m thickness.


29/39

Aractures in the asement are -evelope- into vertically -ifferent 9ones "ith

porosity of 1)'P. Oil test rate is greater than 1%,%%% op-. he remaining

proven reservoirs are Oligocene an- Miocene san-stones.

he Oligocene an- Miocene Rotalia shale provi-es oth vertical an-

lateral seals. ocal caprocks are o"er Oligocene lacustrine clay an- o"er

Miocene mu-stones. rap types encountere- are/ asement highs, rollover

fol-s, tilte- fault locks, -rape anticlines an- stratigraphic pinchouts.

Prospectivity

;uu ong >asin is assesse- to contain 4%P of the total hy-rocaron

resources of Eietnam. he major petroleum plays in the ;uu ong >asininclu-e/

!re)ertiary granite)fracture- asement on horst or tilte- fault locks,

Oligocene an- o"er Miocene clastics associate- "ith four)"ay -ip

structures, -rape aove asement fault locks, locally y inversion.

;uu ong >asin is the major source for Eietnam oil pro-uction.

;urrently, oil is pro-uce- from four fiel-s "ith average of 77%,%%% op-, 5%P

of "hich is from fracture- asement. With the recent significant oil fiel-

-iscovery, the pro-uction is e6pecte- to increase %,%%%)14%,%%% op- y 4%%(.

+lso, the asin is presently supplying all the associate- gas "ith pro-uction of

appro6. 1*' mmcf- through the first pipeline system. Fight petroleum contracts

have een signe- since 15 an- < of them are still effective. he success rate

for e6ploration "ells in the asin is greater than '%P.

Top

a4 2on Son Basin


Development of the #am ;on Son >asin situate- at the intersection of


30/39

t"o major tectonic systems relate- to ?n-ochina e6trusion an- Fast Sea floor

sprea-ing, "as initiate- -uring the !aleogene.

During the Focene)Oligocene, e6tension relate- to the early opening of

the Fast Sea resulte- in the -evelopment of #F)SW tren-ing half)graen@ rift

se:uences fill of these half)graen are continental. +s thermal susi-ence set in

an- the in-ivi-ual -iscrete half)graen fille-, the se-iment provenance ecame

more regional resulting in the asin)"i-e -eposition of high net to gross fluvial

se-iments from the "est. Sag se:uences ecame more non)marine up"ar- an-

more marine "est to east, -ue to overall transgression an- ackstepping of

-eltas -uring the earliest Miocene.

o"ar- the en- of Farly Miocene, #W)SF e6tension associate- "ith a

change in sprea-ing -irection of the Fast Sea le- to enhance- topographic relief

"ithin the asin centre an- structurally controlle- facies pattern, in "hich

caronate systems "ere restricte- to platform or foot"all locations "hilst

-eeper shelf an- slope facies "ere -eposite- "ithin the graen. ?n the ate

Miocene, the asin "as again tectonically restructure- y a mil- inversion,

follo"e- y thermal susi-ence, resulting in large caronate reefal uil-ups an-

infille- san-y turi-ites, asin floor. he process "as interrupte- -uring the

early !liocene -ue to a major transgression.


31/39

Petroleum System

he o"er Miocene paralic mu-stones of the upper post)rift are

estalishe- as the major, oil prone source rocks. pper Oligocene coals

08erogen type ?? an- ??, gas prone2 an- Oligocene syn)rift lacustrine oil)prone

shales are also of importance.

hree major types of reservoirs i-entifie- in the #am ;on Son >asin are,

pre);eno9oic "eathere- fracture- asement, Oligocene an- Miocene clastics,

ranging from continental -eltas to -eep marine turi-ites in origin, an- high

:uality Miocene caronates.

here are a variety of trap types recognise- in the #am ;on Son, the

major ones are rollover fol-s, e6tensional tilte- fault locks, asement highs

an- caronate uil-ups. Develope- throughout the asin, pper Miocene)

!liocene mu-stones are consi-ere- as a regional seal. Oligocene, Miocene

intere--e- mu-stones are local seals.


32/39

Prospectivity

#am ;on Son >asin is assesse- to contain 4%P of the total hy-rocaron

resources of Eietnam. he major petroleum plays in the asin inclu-e/

!re)ertiary fracture- granite at asement highs

Oligocene clastics on four)"ay -ip structures, -rape across asement

faults

Miocene clastics on rollover fault locks, four)"ay -ip or anticline

pper Miocene san-stones associate- "ith turi-ites

pper Miocene caronate platforms

;urrently, operations are performe- on contracts in the #am ;on Son

>asin. +lthough oil is pro-ucing in Dai Bung fiel-, the asin is consi-ere- to

have mainly natural gas potential "ith proven reserves estimate- at aroun- 1%

cf. >esi-es the an ay)an Do fiel- "ith first gas in the en- of 4%%4, other

fiel-s such as Rong Doi, Bai hach)Moc inh, etc., are sche-ule- to e rought

on pro-uction -uring the perio- of 4%%')4%%asin. his can e -escrie- as an intra)cratonic asin, "hich "as create- in

Farly ertiary as a result of the collision et"een the ?n-ia plate an- the

Furasian plate, involving three main phases of structural -eformation.

he first phase "as relate- to rifting, "hich commence- in ate


33/39

FoceneHFarly Oligocene resulting in the formation of numerous Fast)West

orientate- half graens, some cut y #orth)South tren-ing faults. his rift phase

"as connecte- to the -rift of the ?n-ochina lock relative to the +sia mainlan-,

"hich move- along the main left)lateral strike)slip faults. he se-imentation in

the early part of rift phase "as -ominate- y alluvial)fluvial facies -eposite- in

narro", half)graen)like area, an- follo"e- y -eposition of a possile lake

facies at the late stage in "i-er asin.

he secon- phase "as a sag phase, "hich laste- until the ate Miocene.

During the ate Miocene, the transtensional stress change- to transpressional

movement, "here the graen fills "ere inverte-, asically along Fast)West

orientate- anticline an- associate- "ith "rench relate- fol-s. he inversion

phase en-e- "ith an eustatic -rop in sea level, causing the erosion of most

anticlines. + "eak e6tensional phase prevaile- in this area -uring most of the

!liocene)!leistocene time, "hich is referre- to as the thir- phase.

Petroleum System

he pper Oligocene an- o"er Miocene coalHclaystones se:uence is the

primary source rocks in the Malay)ho ;hu >asin. he Oligocene lacustrine

claystones are proven to e "orl- class oil source rock "ithin the asin

08erogen type ? an- ??2, "hile the o"er Miocene -eltaic an- lagoonal liptic

coals an- claystones are goo- source for oth oil an- gas. he organic matter


34/39


35/39

complete in 4%%'.

Plate Tectonics, Stress, and Unconformities: Evolution of the African Rift

System and Atlantic Continental Margins

J. Derek Fairhead1,2,C.M. Green1,2,S.M. Masterton1andR. Guiraud1

1GETECH, Leeds, LS8 2LJ, UK,[email protected];[email protected];[email protected]

2School of Earth Environment, University of Leeds, Leeds, UK, [email protected]

This webpage is a summary of: airhead, !."., #.M. $reen, S.M. Masterton, %. $uiraud, 2&1', The ro(e thatp(ate tectonics, inferred stress changes and stratigraphic unconformities ha)e on the e)o(ution of the*est and #entra( +frican %ift System and the +t (antic continenta( margins, Tectonohysics, 594, 11-12.

The Mug(ad rift basin of Sudan, is a good e/amp(e of po(yphase rifting, with at (east three major phases of basin

de)e(opment. 0ach phase resu(ted in the generation of source roc, reser)oir and sea( geo(ogy with structura( traps

often c(ose(y (ined to basement highs. !airhead et al"2&1'3 in)estigate on a regiona( sca(e the tectonic processesthat contributed to rift basin de)e(opment.

4n a regiona( sca(e, the e)o(ution of the +frica-wide Meso5oic rift system is intimate(y (ined to re(ati)e mo)ements of

+frican sub-p(ates and to g(oba( p(ate tectonic processes and p(ate interactions. #hanges in p(ate interactions are

obser)ed in the oceanic crust as a5imuth changes of fracture 5one geometries igure 13. 6y inference, these ha)e

caused significant modifications to both the orientation and magnitude of the motions of the +frican sub-p(ates. Such

p(ate motion processes ha)e contro((ed the po(yphase de)e(opment of the *est and #entra( +frican %ift System

igure 23.
http://www.see.leeds.ac.uk/people/d.fairheadhttp://www.see.leeds.ac.uk/people/c.greenhttp://www.see.leeds.ac.uk/people/c.greenhttp://www.getech.com/http://www.getech.com/http://www.getech.com/http://www.getech.com/mailto:[email protected]:[email protected]:[email protected]:[email protected]:[email protected]:[email protected]:[email protected]://www.mantleplumes.org/WebDocuments/Fairhead_etal2013.pdfhttp://www.mantleplumes.org/WebDocuments/Fairhead_etal2013.pdfhttp://www.mantleplumes.org/WebDocuments/Fairhead_etal2013.pdfhttp://www.mantleplumes.org/WebDocuments/Fairhead_etal2013.pdfhttp://www.mantleplumes.org/WebDocuments/Fairhead_etal2013.pdfhttp://www.mantleplumes.org/WebDocuments/Fairhead_etal2013.pdfhttp://www.mantleplumes.org/WebDocuments/Fairhead_etal2013.pdfhttp://www.mantleplumes.org/WebDocuments/Fairhead_etal2013.pdfhttp://www.mantleplumes.org/WebDocuments/Fairhead_etal2013.pdfhttp://www.mantleplumes.org/WebDocuments/Fairhead_etal2013.pdfhttp://www.mantleplumes.org/WebDocuments/Fairhead_etal2013.pdfhttp://www.mantleplumes.org/WebDocuments/Fairhead_etal2013.pdfhttp://www.mantleplumes.org/WebDocuments/Fairhead_etal2013.pdfhttp://www.mantleplumes.org/WebDocuments/Fairhead_etal2013.pdfhttp://www.mantleplumes.org/WebDocuments/Fairhead_etal2013.pdfhttp://www.mantleplumes.org/WebDocuments/Fairhead_etal2013.pdfhttp://www.see.leeds.ac.uk/people/d.fairheadhttp://www.see.leeds.ac.uk/people/c.greenhttp://www.getech.com/http://www.getech.com/mailto:[email protected]:[email protected]:[email protected]:[email protected]://www.mantleplumes.org/WebDocuments/Fairhead_etal2013.pdfhttp://www.mantleplumes.org/WebDocuments/Fairhead_etal2013.pdfhttp://www.mantleplumes.org/WebDocuments/Fairhead_etal2013.pdfhttp://www.mantleplumes.org/WebDocuments/Fairhead_etal2013.pdfhttp://www.mantleplumes.org/WebDocuments/Fairhead_etal2013.pdfhttp://www.mantleplumes.org/WebDocuments/Fairhead_etal2013.pdfhttp://www.mantleplumes.org/WebDocuments/Fairhead_etal2013.pdf


36/39

!i#$re 1% &'im$th chan#e of fract$re 'ones for the Central, E($atorial and So$th &tlantic" Clic)hereor on !i#$re forenlar#ement"
http://www.mantleplumes.org/images3/EvAfricPlateFig1_800.jpghttp://www.mantleplumes.org/images3/EvAfricPlateFig1_800.jpghttp://www.mantleplumes.org/images3/EvAfricPlateFig1_800.jpghttp://www.mantleplumes.org/images3/EvAfricPlateFig1_800.jpghttp://www.mantleplumes.org/images3/EvAfricPlateFig1_800.jpg


37/39

!i#$re 2% *est and Central &frican +ift system" Clic) hereor on !i#$re for enlar#ement"

4n the basina( sca(e, changes of sub-p(ate motions ha)e resu(ted in changes in the stress fie(d. These ha)e had a

c(ear impact on the deformation and fau(t geometries of rift basins and on the resu(ting stratigraphy. The unified

stratigraphy of the *est and #entra( +frican %ift System igure '3 shows c(ose corre(ation in time between the major

unconformities and re(ati)e p(ate motion as shown by changes in the a5imutha( geometry of the oceanic fracture

5ones in the #entra( +t(antic red dots, igure 13. Since simi(ar(y timed unconformities e/ist a(ong the continenta(

margins of +frica and South +merica, we propose that the causati)e mechanism is change in re(ati)e p(ate motion,

(eading to increase or decrease in tension in the p(ate in the region of the continenta( margin. This contro(s thestrength or effecti)e e(astic thicness, Te, of the crust7p(ate beneath the margins. 8n turn, this resu(ts in a focused

change in isostatic response of the margin during short-period changes in re(ati)e p(ate motion, i"e"more tension wi((

mean that (oads are not compensated (oca((y resu(ting in (oca( up(ift of the margin.
http://www.mantleplumes.org/images3/EvAfricPlateFig2_800.jpghttp://www.mantleplumes.org/images3/EvAfricPlateFig2_800.jpghttp://www.mantleplumes.org/images3/EvAfricPlateFig2_800.jpg


38/39

!i#$re % Unified strati#rahy chart for the *est and Central &frican +ift System" #(ic hereor on igure foren(argement.

The continenta( margins thus comprise an effecti)e wea 5one within an e)o()ing p(ate due to the sedimentary

(oading effect. #hanges in p(ate stress, at times of p(ate motion change, are recorded in the form of sedimentary

unconformities as the margin is isostatica((y up(ifted or subsides. This study thus ca((s into 9uestion the idea thateustatic sea-(e)e( changes are the principa( cause of the unconformities. 8nstead, it suggests that the principa( cause

is a p(ate-tectonic dri)en mechanism.
http://www.mantleplumes.org/images3/EvAfricPlateFig3_1000.jpghttp://www.mantleplumes.org/images3/EvAfricPlateFig3_1000.jpghttp://www.mantleplumes.org/images3/EvAfricPlateFig3_1000.jpg


39/39

!i#$re -% Continental mar#ins act as .ea) 'ones to chan#es in late stress

/i0lio#rahy of references for the *est and Central &frican +ift Systems

6rown, S.0., airhead, !."., 1'. $ra)ity study of the #entra( +frican rift system: a mode( of

continenta( disruption. 1: the gaoundere and +bu $abra rifts. Tectonohysics,94, 1