VNUJournalofScience,EarthSciences23(2007)235‐243 235 Quaternarysedimentarycyclesinrelationto sealevelchangeinVietnam TranNghi*,NguyenThanhLan,DinhXuanThanh, PhamNguyenHaVu,NguyenHoangSon,TranThiThanhNhan CollegeofScience,VNU Received20November2007;receivedinrevisedform15December2007 Abstract.Vietnam has over 3200 km shoreline which extends from north to south of the country. Sealevelchangeswere principalfactorsinfluencedonsedimentaryenvironmentandcompositions. InQuaternary,cyclesofsealevelchangeandtectonicmovementweremainfactorthatcreatedRed River delta, Nam Bo plain and Central plain. There are 5 sedimentary cycles corresponding to 5 cycles of sea level change of the Red River delta and Nam Bo plain. Sedimentary cycles were characterizedbysedimentarycoefficientssuchas:grainsize,claycontent,indexofcationFe 2+ /Fe 3+ exchange,pHvariationfromthestarttotheendofcycles.Theyarerepresentedbyfluvialterraces, marine terraces, marine notches and peat layers. In central littoral plain, the relationship between sedimentary cycles and sea level is represented by five sandy cycles and distribution of coral terracesinshallowsea. There are 5 generations of ancient shoreline zones, which correlated with glacial and interglacialperiodsinVietnamesecontinentalshelf:theshorelinein30mwaterdepthiscorrelated with (Q 2 1-2 ). Up to 60 m water depth is correlated with (Q 1 3b ‐Q 2 1 ) and 100‐120 m water depth is correlated with Wurm 2 glaciation (Q 1 3b )(?). In 200‐300 m water depth correlated with Wurm 1 glaciation(Q 1 3a )(?),at400‐500mwaterdepthcorrelatedwithRissglaciation(Q 1 2b )(?),at600‐700m waterdepthcorrelatedwithMindelglaciation(Q 1 2a )(?),andat1000‐1500mwaterdepthcorrelated with Gunz glaciation (Q 1 1 )(?). As such Quaternary sea level changes in mainland and continental shelfinteractedandquitedistinctiveformeachotherbypendulumrule. Keyw ords:Quaternarysedimentarycircles;RedRiverDelt a;CuuLongRiverDelta;Sealevelchange. 1.Introduction * Vietnamhas over 3200 km shoreline which extendsfromMongCaiinthenorthtoHaTien in the south. Sea level changes had influenced _______ *Correspondingauthor.Tel.:84‐4‐5587059 E‐mail:trannghi@vnu.edu.vn onsedimentaryenvironmentandcompositions and the evolution sedimentary cycle of Red RiverDelta,CuuLongRiverDeltaandCentral Coastalplains.Thesecyclesweredistinguished by absolute age dating include: thermo‐ luminescence age, 14 C dating from wood and shells. Geomorphological characteristics and sedimentary coefficients were used together TranNghietal./VNUJournalofScience,EarthSciences23(2007)235‐243 236 with absoluteages to analyzethecause‐effect relationship between development of sedimentary cycles, sea level changes, and tectonicmovementinQuaternary. 2.Methodology There are many research projects have undertaken by Vietnamese scientists on Quaternary sea level change, especially in Late Pleistocene to Holocene. However, the identification of transgression and regression phases and lithofacies analysis based on quantitative approaches such as material compositions, geochemical environmental coefficients, have just applied by Tran Nghi, MaiThanhTanandotherworkersin2000,2001 [6, 8]. Therefore, in this paper, we will use the same approaches to analyze the cause‐effect relationshipbetween lithologicalcharacteristics and lithofacies associations in relation to transgressionandregressionphaseandtectonic movements: fluvial and marine terraces in mainland and in continental shelf that are distributed in different height and depth and compare them to the transgression and regressionsystemofancientshorelines. For investigating mechanism of sedimentary evolutionofRedRiverDelta,Cuu Long River Delta and Central plains, it is necessarytodefinethecause‐effectcorrelation between lithology, sea level change, and tectonic movement. The sedimentary environment has major role in governing petrological compositions in term of lithofacies ‐ paleogeography. The transgression phase is characterized by marshy, lagoonal and deltaic environments. Meanwhile, regression pha ses createdcoarse‐grainedmaterialsofproluvial‐ aluvialenvironments.Therefore,therelationship between sedimentary cycles and sea level change is determined by changing of facies associationaccordingtotimeandspace.Theend of a cycle is marked by a weathering period to form laterite‐bearing,yellowtoredsediments. Vietnam (Tran Nghi) North West Europe Archaeology Absolute age (Ka) Geological age Sedimentary cycles Regression Transgression Stratigraphy Regression Transgression British Alper (Penk) Italy Middle East Poland (Sapherlevin) Russia (Lakovlep) North of America (East) Human species Cultural periods Q 2 3 ? HOLO- CENE Holocene Flandrian Transgression Holocene Transgression Holocene Transgression Holocene Transgression “Nizza” Transgression Holocene Transgression Transgression Mogine Holocene Transgression Mesolithic and Neolithic Q 1 3b -Q 2 3 Regression Regression W 2 Regression Baltic Glaciation Astakop- vandai Viskosine (2) Modern human Upper Q 1 3b ? Weich- sebian Transgression Regression Khanstanton W 1 -W 2 ? W 1 Regression Muzur Vacsava II Deglaciation Mologo sek nhim Kalinin V 1 -V 2 Viskosine (1) Nean- dectane Middle Late Eemian Transgression Upper Ixla Khocnen R-W 1 Pantinian Tyrhenian Mazoves II Mikulin Odinsop Q 1 2b-3a ? Saalian Regression Dzippin Riss Regression Vacsava I Dnheprop Holsterian Transgression Lower Khocnen M-R ? Mazoves I Likhvin Pre Nean- dectan and pre Sapien Lower Middle Q 1 2a ? Elsterian Regression Logestophoc Glaciation Mindel Regression Krakop Acient glaciation 1,2 Cromeriam complex Transgression Cromerian G-M Cromerian Roman crotorian Sandomir Acient deglaciation Q 1 1b ? Menapian Regression Crue Gun Cassia Siciian Laroslap Acient glaciation Early Paleolithic Waal D-G PLEISTOCENE Early Q 1 1a ? Eburonian D Emilian Tiglian Practiglian 10 125 700 900 1.6 2-2.5 Ma PLIOCENE Reuverian Heidel- berg species Fig.1.Comparisonofsealevelchange‐glacial‐interglacial‐sedimentarycyclesandgeologicalage[9]. TranNghietal./VNUJournalofScience,EarthSciences23(2007)235‐243 237 Themainmethodsusedinthispaperare: ‐Petrologicalanalysismethodwascarriedout using thin sections, made by cementing epoxy ofunconsolidatedsands. ‐Granulometricanalysisofsandwasusedby sets of sieve or pipet of different fractions and then granulometric parameters (Sorting‐So, Asymetric coefficient‐Sk, average grain size‐ Md)wereobtainedbyaPCsoftware. ‐ Geochemistry environmental coefficientsof sediments was measured by specialized meter andthenobtained:pH,Eh,Kt,Fe 2+ /Fe 3+ These pH‐alkaline‐acidindex,Eh‐redoxpotention index,Kt=(Na + +K + )/(K 2+ +Mg 2+ )exchanging cation coefficients were applied in lithofacies association analysis and reconstruction of paleogeographicallandscape. 3. Transgression‐regression cycles of Red River Delta, Cuu Long River Delta, Central plaininQuaternary RedRiverDelta(RRD)andCuuLongRiver Delta(CLRD)arethebiggestplainsinVietnam. Developing history and sedimentary evolution of both deltas have closely related with sea level changes in Quaternary in which regression were according Gunz, Mindel, Riss, Wurm 1 ,Wurm 2 glacialphasesandtransgressions were correlated with interglacial phases and Flandrientransgression. Five sedimentary cycles in RRD and CLRD werecorrelatedwith5stratigraphicformations: inearlyPleistocene(Q 1 1 ),Middle‐LatePleistocene (Q 1 2-3a ),LatePleistocene(Q 1 3b ),latepartofLate Pleistocene‐Middle Holocene (Q 1 3c ‐Q 2 2 ) and Late Holocene in each delta (Fig. 1‐6) [2]. The beginning of a cycle wa s related with coarse grained size pebbles, sands proluvial and alluvialfaciessedimentwhatismainlandorigin and the ending was related with fine grained sizesilt,claydeltaicandlagoonalfacies. 0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 Depth (m) BH59-64 605 BH-11 105 To Lich river Red River BH2-HN 156 BH3-HN 180 BH4-HN a.amQ 2 3 tb a.amQ 2 3 tb apQ 1 2 -3 hn a.amQ 2 3 tb am lbQ hh 2 1-2 amQ 1 3b vp amQ 1 3b vp amQ 1 3b vp aQ 1 1 lc N 2 2 vb aQ 2 3a tb ~ . ~ . ~ . ~ ~ . ~ . ~ ~ . ~ . ~ . ~ . ~ . ~ ~ . ~ . ~ . ~ ~ . ~ . ~ . ~ ~ . ~ . ~ . ~ ~ . ~ . ~ . ~ ~ . ~ . ~ . ~ ~ . ~ . ~ . ~~ . ~ . ~ . ~ ~ . ~ . ~ . ~ ~ . ~ . ~ . ~ ~ . ~ . ~ . ~ ~ . ~ . ~ . ~ ~ . ~ . ~ . ~ ~ . ~ . ~ . ~ ~ . ~ . ~ . ~ ~ . ~ . ~ . ~ ~ . ~ . ~ . ~ ~ . ~ . ~ . ~ ~ . ~ . ~ . ~ ~ . ~ . ~ . ~ ~ . ~ . ~ . ~ ~ . ~ . ~ ~ . ~ . ~ ~ . ~ . ~ . ~ ~ . ~ . ~ . ~ ~ . ~ . ~ . ~ ~ . ~ . ~ . ~ ~ . ~ . ~ . ~ ~ . ~ . ~ . ~ ~ . ~ . ~ . ~ ~ . ~ . ~ . ~ ~ . ~ . ~ . ~ ~ . ~ . ~ . ~ ~ . ~ . ~ . ~ ~ . ~ . ~ . ~ ~ . ~ . ~ . ~ ~ . ~ . ~ . ~ ~ . ~ . ~ . ~ ~ . ~ . ~ . ~ ~ . ~ . ~ . ~ ~ . ~ . ~ . ~ ~ . ~ . ~ . ~ ~ . ~ . ~ . ~ ~ . ~ . ~ . ~ ~ . ~ . ~ . ~ ~ . ~ . ~ . ~ ~ . ~ . ~ . ~ ~ . ~ . ~ . ~ ~ . ~ . ~ . ~ ~ . ~ . ~ . ~ ~ . ~ . ~ . ~ ~ . ~ . ~ . ~ . ~ . ~ . ~ . ~ . ~ . ~ . ~ . ~ . ~ . ~ . ~ . ~ . ~ . ~ . ~ . ~ . ~ . ~ . ~ . ~ . ~ . ~ . ~ . ~ . ~ . ~ . ~ . ~ . aQ 2 3 tb a.amQ 2 3 tb Fig.2.Litho‐faciescrosssection inthecenterofRedRiverDelta[3]. ha no i Thai Nguyen Viet Tri Phuc Yen Son Ta y Ha Dong Hung Yen Hai Duong Hai Phong Kien Xuong Vinh Ni nh Nam Dinh aQ 2 3a tb aQ 2 3b tb N 2 > 8 0 m Q : 6 0 - 8 0 m 1 1 l c Q 1 2 - 3 a h n Q 1 3 b v p N a m Q 2 3 t b m m b Q 2 1 - 2 h h a m Q 2 1 - 2 h h a Q 1 3 b v p a p Q 1 2 - 3 h n a p Q I I - I I I 1 h n a p Q 1 1 l c a p Q I l c Red River Dam Te rr ac e Aluvial - proluvial pebbles - gravel facies Plain channel deposited facies Spotted weathering marine clay Eroided area ap a m h 2 h 1 Q 2 1-2 hh Fig.3.Blockdiagramofalluvialfacies inRedRiverDelta[11]. Thefirstsedimentarycycle(EarlyPleistocene, Le Chi Formation in RRD and Trang Bom Formation in CLRD) are characterized by coarse grained size sediment with content of pebbles‐gravel increased from 15 to 20.8% in RRD and 13.8% in CLRD [2]. The ending of cycles was correlated with interglacial phase, silty claydeltaic‐marshyfacies(Md=0.1‐0.5mm in RRD and Md=0.018‐0.439 mm in CLRD). TranNghietal./VNUJournalofScience,EarthSciences23(2007)235‐243 238 During maximum sea level rise, erosion‐ accumulationterraces of55‐70mhigh inNEof RRD were formed. Meanwhile, lit hofacies associationofsandybarriersandlagoonalfacies isthemainfeatureinCentralcoastalplainfrom Quang Binh Province to Mui Ne‐Phan Thiet, BinhThuanProvince. The second sedimentary cycle from Middle ‐ Late Pleistocene (Hanoi Formation in RRD andThuDucFormationinCLRD)iscomprised by thick pebble‐gravel layer (10‐80 m) of mountainous river and proluvial facies (Md=0.2‐1 mm in RRD and Md=2.3 mm in CLRD[2]).Bytheendofthissedimentarycycle, rock composition composes of clayish marshy and clayish silt deltaic facies in Thanh Hoa plain, RRD, CLRD, and ancient sandy bars, tombololagoonalfaciesinCentralplain. Thethird sedimentarycyclecorrespondsto Late Pleistocene (Vinh Phuc Formationin RRD and Cu Chi or Moc Hoa in CLRD), which contains coarse and medium grained sands of riverbedfaciesandpassingupwardsintosand levee facies, silty clay flood plain and clay marshy, greenish lagoonal facies. In Central plain, late Pleistocene transgression phase createdbigvolumeofwhitequartzsandybars. However,thesewhitesandhavebecameyellow sanddueto infiltrationweathering. 30 30 20 20 10 10 0 0 -10 -10 -20 -20 -30 -30 -40 -40 -50 -50 -60 -60 -70 -70 -80 -80 -90 -90 Tam G ia n g la g oon BH 407 BH 314 BH 312 Huong river Q 1 3b mQ 1 3b amQ 2 3 mQ 2 1-2 mvQ 1 2-3a mvQ 1 3b aQ 1 2-3a amQ 1 2-3a amQ 1 1 aQ 1 1 mvQ 1 1 mQ 1 1 mQ 1 3b mQ 2 1-2 mvQ 2 3 mQ 2 3 mQ 1 2-3a Fig.4.Litho‐faciescrosssection ofThuaThienHuePlain[4]. The fourth sedimentary cycle was formed duringperiodfromLatestPleistocenetoEarly‐ MiddleHolocene(HaiHungFormationinRRD and Tan Thanh or Binh Chanh Formation in CLRD). This sequence is characterized by Flandrien transgression sedimentary facies complex and composed of sandy silt of deltaic facies,claysiltrichin organicmaterialandpeat ofmarshy facies. These layers were coveredby grey‐greenishclayoflagoonalfacies.Thecoastal plains in Central Vietnam, from Nghe An to BinhThuanprovinces,composeofacombinat io n of coastal sandy bars and lagoons occuring inside sandy bars. The associations of tombolo and bay was quite typical in South Central Vietnam, especially in Khanh Hoa Province. a a a a a a m Q 2 2 - 3 a b Q 2 2 - 3 a b Q 2 2 - 3 a m Q 2 1 - 2 a m Q 2 1 - 2 a m b Q 2 1 - 2 m b Q 2 1 - 2 a m Q 2 1 - 2 0 20 -10 0 -20 0 0 20 -100 Lk17 Lk209 Lk214a Lk31MT Lk325 500 400 479.6 501.7 396.2 Lk812 339.6 Lk819 203.9 Vam C o Dong River Sai Gon River Lk816 169 Co Chien River Ham Luong River Vam C o Tay River Dong Nai River + + + + +++ + + U U U U U U UU U U U U Lk817 75 Lk818 396 Bk11 80 Hau River Tien River Fig.5.SedimentarycrosssectioninCuuLongRiverDelta[9]. TranNghietal./VNUJournalofScience,EarthSciences23(2007)235‐243 239 Geological Age Age of Sedimentary Cycles TL age (Ka) No samples and place name Sandy cycles Lithology Lithology Envi. Envi. Cycles of lagoonal plain Detrital minerals of sandy barrier Q (%) F(%) R(%) Sorting Rounding Sea level (Reg - Trans) So Ro H O L O C E N E Early - Middle Late P L E I S T O C E N E Early Middle Late Late Holocene Late Pleistocene Middle Holocene Late Pleistocene Middle - Late Pleistocene Late part of. Early Pleis 10 6 125 700 1.6 Ma Q 2 3 Q-Q 12 3c 1-2 Q 1 3b Q 1 2-3a Q 1 1 14+2 14+2 28+4 48+6 52+7 62+6 85+9 99+19 101+17 103+11 122 >181 >204 108+49 VN44 VN12 VN45 VN37 VN18 VN30 VN15 VN12b VN31 VN20 VN29 VN32 VN14b VN14 Bau Trang Tuy Phong P. T Airport Suoi Tien Chi Cong S. Song Luy Suoi Tien Tuy Phong Hon Rom Chi Cong S. Song Luy H. Rom Suoi Tien Suoi Tien mv m mv m. mv? m mv m mv am, m am m mb a, am m am a m am a m am a 98-100 95-9892-98 92-98 90-98 0-1.00.5-2.01-3.01.0-2.01.0-3.0 0-1.0 0.5-3.0 1.0-8.0 1.0-7.01.0-7.0 1.2-1.51.3-1.71.3-1.81.5-1.81.5-1.8 0.6-1.0 0.6-0.9 0.5-0.9 0.6-0.9 0.6-0.8 W2 W1-W2 W1 R-W1 R M-R M G-M G Fig.6.Comparisonofthermoluminescenceagesofquartzsandybarrier andsedimentarycyclesinBinhThuanProvince,Vietnam[9]. The fifth sedimentary cycle was formed in Late Holocene regression phase (Thai Binh Formation in RRD and Can Gio Formation in CCRD).Thiscycleisdominatedby sands,silts, clay alluvial facies in upper part and silt, clay deltaic plain, grey clay marshy and sand silt clay deltaic front facies in lower part. Besides, Late Holocene eolian sediments have been formedbywindreworkingoldsandyformation. In addition, the fifth cycle was also eolian sedimentinsandybarsandsandydunesin CLRD. 4.Thermoluminescenceageofredsandycycles inPhanThiet‐BinhThuanprovinces The coastline of South Central Vietnam is dominated by extensive sandy coastal barrier successions of Early Pleistocene, Middle‐Late Pleistocene, LatePleistoceneandLatePleistocene toEarly‐MiddleHoloceneandLateHolocene. The first cycle: an angular tektite layer coveredalternativeredandwhite‐yellowsand barrier of Early Pleistocene. Probably, this red sandsuccession shouldhaveageolderthanthe age of tektites (i.e. before 700 Ka) [1]. The comparison of these successions with glacial and interglacial in the world (Fig. 1) correspondstointerglacialGunz‐Mindel. Fig.7.Thesequenceofredsandandlightgreysand, ChiCong,BinhThuanProvince,Vietnam[7]. The second cycle, composing of 2 rhythms, was possibly equivalent to older grey‐white, wellcementedsandbarrierofMiddlePleistocene age (Q 1 2a ) (TL age of >204 Ka [1]). Moderate cemented red sand barrier of Middle‐Late Pleistocenearedominatedbyinnerbarriers.The TranNghietal./VNUJournalofScience,EarthSciences23(2007)235‐243 240 sandy samples yielded an age of 103±11 Ka , 101±17Ka[1],possiblyequivalenttostage5oflast interglacialsensulatooftheOxygenIsotoperecord . Thethirdcyclecomprisesbyaseriesofred and yellow sand successions of barriers dominated in coastal zone of South Central Vietnam from Phan Thiet to Tuy Phong. This cycle over lies of Middle‐Late Pleistocene sandy barrier successions the boundary between second cycle is exposed and third cycle in Hon Rom, Chi Cong, Suoi Tien and Song Luy. The alternation of red sand and yellowsandrhythmsrelatedtosealevelchange andinfiltrationweatheringinlatePleistocene. SampleVN31yieldedanage101±17Ka[1]. Sample VN31 yieldedan age of 101±17 Ka, andVN32‐anageof108±49Ka(HonRom)[1]. ThisagerangebelongstoLatePleistocenecycle whicharesuggestiveofdepositionduringstage 5(sensulato)oftheOxygenIsotoperecord. Thefourthcyclecomposedoftworhythms: an eolian red sand dunes of Late Pleistocene (sampleat Phan Thiet airport yieldeda TL age of 28±4 Ka) correlated with stage 2 and 3, and white sand barriers oxygen isotope to be equivalent with last glacial maximum (W 2 ) of Early‐MiddleHolocene. The fifth sandy cycle reworked Holocene quartzsandybarriertoformsand duneduring 3Katopresent.TheSouthCentralcoastalzone betweenPhanThietandTuyPhongisdominated on surface by light yellow active dune fields due to reacting of wind, possibly correlated withHoloceneregressionandsealevelrise. 5. Cycles of coral reef in relation to sea level change in coastal zone and shallow sea of CentralVietnamarea Coral reefs occur in 3 locations in shallow seaofSouthCentralVietnam(Fig.8). Middle‐LatePleistocenecoralreefs,which were calcified,occur in Hon Do‐Ninh Thuan. This layer is covered by red sand. Late Pleistocene coral reef terrace is distributed in 20‐25 m water depth. Middle Holocene coral reef terraces are located in 1‐2 m water deep yieldandageof5000yearBPbyC 14 dating. Distribution of calcified coral reefs in comparisonwithredsand(19Ka)showedthat: this layer could have been formed in Middle‐ Late Pleistocene transgression and Vinh Phuc transgression that created red sand and coral reefin20‐25mwaterdepth.Theredsandlayer coversthecoral. Fig.8.DevelopmentperiodsofcoralinSouthCentral area(HonGomPeninsula). Thecoralterracein20‐25mwaterdepthwas formedinFlandriantransgression.Thiswasthe second sea level stands in Holocene and it is correlative to ancient shorelines. The coral reef at 1‐2m water depth, formed in Early‐Middle Holocene,iscorrelatedwithwhitesandinCam RanhandHonGom. Q 2 1-2 Q 1 3b 20-25m Q 2 2 Q 2 3 Q 2 2 Q 1 3b m v Q 2 3 Red-Yellow sand White sand 5 K a a c b TranNghietal./VNUJournalofScience,EarthSciences23(2007)235‐243 241 Fig.9.LateritegravelinbottomsedimentinSW EasternSea. Fig.10.Foraminifera,diatomea,quaczitefragments andfragmentsofdaciterockinbottomsedimentsin SWofEasternSea. Fig.11.WeatheringspottedclayinLatePleistocene sedimentinSWofEasternSea. 6.Quaternaryshorelinesinbottomofcontin ental shelfofVietnam 6.1.Ancientshorelines The well‐sorted and well‐round ancient sandy bars distributed parallel to modern shoreline. Well‐round laterite gravels are situated in sea bottoms far from modern coastline. This layer is covered by spotted clay la yer which containedlaterite curdles. Concentrationofcoarse‐grainedterrigeneous sediment and moderate to well‐roundness bioclasts[9]. Location of ancient shoreline in continental shelf[8]: ‐In30mwaterdepthcorrelatedwith(Q 2 1-2 ). ‐In60mwaterdepthcorrelatedwith(Q 1 3b ‐Q 2 1 ). ‐ In 100‐120 m water depth correlated with Wurm 2 glaciation(Q 1 3b ). ‐ In 200‐300 m water depth correlated with Wurm 1 glaciation(Q 1 3a ). ‐ In 400‐500 m water depth correlated with Rissglaciation(Q 1 2b ). ‐ In 600‐700 m water depth correlated with Mindelglaciation(Q 1 2a ). ‐In1000‐1500mwaterdepthcorrelatedwith Gunzglaciation(Q 1 1 ). 6.2. Relationship between marine terraces and sedimentarycyclesintheseabottom In Quaternary, appearance of fluvial and marine terraces in mainland and continental shelf are the results of uplift‐subsidence movements and transgression‐regression phases. Five ancient marine terraces on mainland and 6 on continental shelf [9] from Pleistocene toHoloceneagescanbeidentified. These terraces have symmetric relation, it means that the oldest marine terrace on mainlandisathighestelevation(highestpoint) and the oldest marine terrace on continental shelfisatlowestelevation(deepestpoint)(Fig. 12). The marine terraces on mainland and continental shelf of the same age were formed in the same sedimentary cycle. These periods extended from Pleistocene to Holocene. Thus, sea level changes combined with uplift activities on mainland and subsidence in sea bottom characteristic marine terraces systems hadproduced. TranNghietal./VNUJournalofScience,EarthSciences23(2007)235‐243 242 Height (m) Terraces Sea terraces on mainland Age of Continental shelf sediment 100 80 60 40 20 10 0 -50 -100 -200 -400 -500 -600 -2000 -2500 Qb I VI V V IV III II I I II III IV V VI Qa I Qa I Qa II Qa II Q-Q a II III 1 Qa III 1 Q III 2 Q III 2 Q-Q III IV 21 Q IV 3 Q IV 3 Q IV 3 Q IV 2 Qb II-III 1 Qb III 2 Q I Q III Q IIIB 2 Q IIIA 2 Q IIIb 2 Q II 1 Q I 1 Q IV 2 Q IV 3 Q IV 3 Q-Q III IV 21 Q-Q III IV 21 Q IIIa 1 1 120 7 7 6 6 5 5 4 4 3 3 22 2 1 1 Glacier phases Wurm (W) Riss (R) Mindel (M) Gunz (G) Dunai (D) Fig.12.RelationshipbetweenseaterracesandPliocene‐Quaternarysedimentarycycles incontinentalshelfofVietnam[10]. 7.Conclusions In Quaternary, cycles of sea level change and tectonic movement cycles are the main reasons, which create Red River Delta, Cuu LongRiverDeltaandCentralplain.Thereare5 sedimentarycyclescorrespondingto5cyclesof sea level change in Red River Delta, Cuu Long River Delta, and Central plain. In Central littoral plain, the relationship between sedimentary cycles and sea level change is characterized by 5 sandy cycles and distributionofcoralterracesinshallowsea. Thereare5generationsofancientshoreline zones,whichcanbecorrelatedwithglacialand interglacial phases in Vietnamese continental shelf: at30mwaterdepthcorrelatedwithQ 2 1-2 ; at60mwaterdepthcorrelatedwithQ 1 3b ‐Q 2 1 ;at 100‐120 m water depth correlated with Wurm 2 glaciation Q 1 3b ; at 200‐300 m water depth correlatedwithWurm 1 glaciation(Q 1 3a );at400‐ 500 m water depth correlated with Riss glaciation Q 1 2b ; at 600‐700 m water depth correlated with Mindel glaciation Q 1 2a ; and at 1000‐1500 mwaterdepthcorrelatedwithGunz glaciationQ 1 1 .Theseanc ientshorel inescorrelated with marine terraces and 6 sedimentary cycles incontinentalshelf. References [1] V.M.W. Colin, G.J. Brian, Tran Nghi, M.P. David, et al., Thermoluminescence ages for a reworkedcoastalbarrier,southeasternVietnam: a preliminary report, Journal of Asian Earth Sciences20(2002)535. [2] Nguyen Huy Dung et al., Neogene‐Quaternary stratigraphicaldivision andNamBo plainstructure research, Department of Geology and Mineral Resource,Hanoi,2003(inVietnamese). [3] TranNghi,NgoQuangToan, Characteristics of sedimentary circles and history of Quaternary geology of Red River Delta, Journal of Geology 206‐207(1991)31(inVietnamese). [4] Tran Nghi, Circles of marine transgression, regression, and formation history of Central plains in Quaternary, New discoveries in archeology in 1995 year, Hanoi, 1996 (in Vietnamese). [5] Tran Nghi, Evolution of coastal sandy formations in Central Vietnam in relationship TranNghietal./VNUJournalofScience,EarthSciences23(2007)235‐243 243 with the oscillation of sea level in Quaternary. Project Marine geological research and Geophysics (II),InstituteofOceanography,Hanoi,1996. [6] Tran Nghi, Nguyen Dich Dy, Dinh Van Thuan, VuVanVinh,MaKongCo,TrinhNguyenTinh, Phan Thiet red sands‐material composition, provenance, mechanism of formation and evolutionin relationwithsealevelchangesand neotectonics, Proceedings of The first scientific conference, Hanoi UniversityofScience,1998(in Vietnamese). [7] Tran Nghi et al., Environment and mechanism of red sand formation in Phan Thiet Province, JournalofGeology245A(1998)31(inVietnamese). [8] TranNghi,MaiThanhTan, DoanDinhLam,La The Phuc, Dinh Xuan Thanh, Nguyen Dinh Nguyen,Characterist icsofPliocene‐Quaternary lithofacies‐paleogeographyinshelfof Vietnam, Journal of Sciences of the Earth, 23 (2001) 35 (in Vietnamese). [9] Tran Nghi, Mai Thanh Tan, Dinh Xuan Thanh, Nguyen Thanh Lan, The sea level change problem in Quaternary based on sedimentary research in littoral and shallow sea from Nha Trang to Bac Lieu, Proceedings of Scientific conference Geotechnics and Marine Geology, Da Lat,2003(inVietnamese). [10] Tran Nghi, Textbook on sedimentology, VNU PublishingHouse,Hanoi,2003(inVietnamese). [11] Tran Nghi, Textbook on marine geology, VNU PublishingHouse,Hanoi,2005(inVietnamese). . VNUJournalofScience,EarthSciences23(2007)235‐243 235 Quaternary sedimentary cycles in relation to sea level change in Vietnam TranNghi*,NguyenThanhLan,DinhXuanThanh, PhamNguyenHaVu,NguyenHoangSon,TranThiThanhNhan CollegeofScience,VNU Received20November2007;received in revisedform15December2007 . country. Sea level changeswere principalfactorsinfluencedon sedimentary environmentandcompositions. In Quaternary, cycles of sea level change andtectonicmovementweremainfactorthatcreatedRed River