N. Panin - On the Geomorphologicand Geologicevolution of the Nver - lnteractionZone

ONTHE GEOMORPHOLOGIC AND GEOLOGIC EVOLUTION OF THE RIVERDANUBE . BLACKSEA INTERACTION ZONE

NicolaePRxttrt

NationalInstitute of MarineGeology and Geo-ecology- GEoEcoMAR 23-25,D. OnciulStr., 70318 Bucharest, Tel/Fax: +fi-1-252.25.94, E-mail: [email protected]

Abstract. The presentpaper aims at describingof the evolutionof the mouthzones of three main distributariesof the DanubeDelta system:the northernbranch - Chilia,a medianone - Sulinaand a southernbranch - St. George(Sf.Gheorghe). These main distributaries areresponsible for the formationand the developmentof differentstages of the DanubeDelta. The descriptionis basedon the complex studyof the.entireDanube Delta edifice by aerophotogrammetric,geomorphologic, sedimentologic-geologic, biostratigraphic means, as ''C wellas by datationof deltaicdeposits. The mainstages of developmentthrough which the DanubeDelta reached the presentday aspectinclude:(1)theDanubeGulf andthe"DanubeBlockedDelta"--12-1 1 k.yr.B.P.; (2)lnitial Letea-CaraormanSpit, 11,700-9,800 yr.B. P.; (3) St.GeorgeI Deita,9,000-7,200 yr. B. P.; (4) SulinaDelta, 7 ,2OO-2,000 yr. B P.;(5)St, George ll Deltaand ChiliaDelta, 2,800 yr.B.P.-present;(6) SecondaryCosna-Sinoie Delta, 3,550-2,500 yr B.P. Detaileddescription of the succesivephases of developmentof the mentionedstages is given. 'oC Key words: geomorphologicand geologicevolution, deltaic deposits, phases of development, datation, system.

INTRODUCTION THE "BLOCKEDDANUBE DELTA'' The river-sea interaction zones have very ln the period12-11 k.y. BP, when the level of complexdynamic, depositional, biogeo-chemical the Black Sea had reachedthe present level or, and eco-structuralcharacteristics. Geomorpho- probably,had even exceededit with few meters, logicallythese zones are representedmostly by the present area of the Danube Delta was estuariesand deltas. transformedinto a large gulf - the Danube Gulf. One of the most interestingand complexof the All the tributaryvalleys coming from the plateau Europeandeltas is the River DanubeDelta. The Bugeac-Kitai,Catlabug, lalpug, Kahul etc. had DanubeDelta is situatedin the North-westernpart been partiallyinvaded by the sea and changedin of the Black Sea, between 4425' and 45"30' limans by forming spits at their mouths. In this northernlatitude and between 28"45' and 29'46' period the Northern shore of the Danube Gulf easternlongitude, being borderedby the Bugeac presentedsome promontoriesin the presentday Plateauto the North and by the DobrogeaUnit to area of the delta, of which the most important the South. being Jebriany,Chilia and lzmail-Bugeac.There probably The main phases of development through were alsosome reliefs, exposed,situated the areas Stipoc. which the Danube Delta reachedthe presentday in Letea,Caraorman and These supporting, aspect include: (1) Initial Letea-CaraormanSpit, reliefs might have representedthe points 11,700 -9,800 yr.B.P.; (2) St.George I Delta, hanging for the spits which had started yr.B.P.;(3) forming under the action of the littoral drift of 9,000-7,200 SulinaDelta, 7,200-2,000 - yr.B.P.;(4)St.George ll Delta and Chilia Delta, sediments. "The lnitial Jebriany Letea 2,800yr.B.P.-present; (5) SecondaryCosna-Sinoie Caraorman Spr?" was formed by the sediment Delta,3,550-2,500 yr.B.P. littoral drift fed by the Ukrainian rivers at the mouth of the DanubeGulf, closingalmost entirely The Danube Delta has three main the access into the Gulf (Fig.1). The Stipoc - distributaries:a northernbranch Chilia,a median lacustrianspit formed within the gulf having the - - one Sulinaand a southernbranch St.George starting point the lzmail promontory,supporting (Sf.Gheorghe). These main distributaries are pointStipoc relief and the "tail"towards the Chilia responsiblefor the formationand the development promontory. of differentstages of the DanubeDelta. Thus, the Chilia promontorytogether with the present paper The aims at describing the Stipoc paleoreliefand the lacustrianspit Stipoc evolutionof the moulh zones of these three main have closed a large depressionaryarea - the distributariesof the Danube Delta system. The Pardina Depression, where, as it had been description is based on the complexstudy of describedby the ancientsat the beginningof our the entire Danube Delta edifice by aerophoto- era, there was the lake Thiagola.The lake might grammetric,geomorphologic, sedimentologic- have comprisedthe wholePardina Depression and geologic, biostratigraphicmeans, as well as by the presentday lakes (limans) Sofian, Catlabug toCdatation of deltaicdeposits.

GEO-ECO.MARINA,A1997 ?t Nationallnstitute of Maine Geologyand Geo-ecologyof Proc. lntern. Workshopon'Fluvial-Maine lnteractions"in Malnas,Romania, Oct.1-7, 1996

\ N. Panin - On the Geomorphologicand Geologicevolution of the River Danube- Black Sea lnteractionZone

course comes into touch with the Dobrodgean "wall"and it is reflectedNorth-eastward, and then is broughtback by the Coriolisforce to the same "wall".These points are Tulcea,Nufaru (Preslav or Periaslavet),Carasuhat, Mahmudia. After the "hit" at Preslav,the Paleo-Tulceabranch divided into Paleo-St.Georgeand Paleo-Sulinadistributaries. However, the same Coriolis force must have determinedthe Paleo-St.Georgebranch to have beenthe most importantand activedistributary for a long time, being responsiblefor the appearance of the first DanubeDelta - St. GeorgeI Delta.At a certaintime the Paleo-St.Georgedistributary was clogged and the Paleo-Sulinabranch took the main role within the deltaic system of water and sediment pathways.The Sulina distributarybuilt up the nextDanube Delta - the SulinaDelta. In the Blocked Delta phase, the Paleo-Chilia distributaryseems to have had less importance Black Sea and a smaller discharge than Paleo-Tulcea branch. On a certain distance the Chilia distributarywas flowing Northward,up to hitting the BugeacPlateau in the lzmail area, where it was changing its direction Eastward, directing probably along the approximately present day courseof Sonteachannel and joining with Paleo- Sulinadistributary in Mile 25-Mile24 areaon its so Fig.l Firststage of the DanubeDelta evolution (1 1700-7500 called Old Danube(Dun6rea Veche) section.The BP) (afterPanin, 1996a) flowing of Paleo-Chiliainto the Thiagola Lake and Kitai. (PardinaDepression) is difficultto be explainedas a hydrologicalphenomenon and to be appreciated During the existence of the Danube Gulf, flowingmight have been the resultof almost the whole solid discharge of the River in time. This level variationsof the Danubewas settledinside the gulf, formingthere a the relativewater Danube Gulf and of Thiagola Lake, variations which reafdelta, so one couldspeak about the "Blocked determinedthe Stipoc lacustrinespit breakingnot Danube Delta" phase (Fig.1). The lnitial Spit far from lzmail Promontory(at the "foot" of the representsthe limit betweertthe two main unitsof spit) and of Chilia Promontoryin the place where the DanubeDeltaic Plain: the FluvialDelta Plain, this was narrower.The breakingsplayed then a westward the spit and the Marine Delta Plain, part of natural capture: the first captured the eastwardof it. flowing of Paleo-Chiliadistributary deriving it to As regardsthe evolutionof the BlockedDelta the PardinaDepression, and the secondone had a (the fluvial one), the existingdata are limited,the part of dischargingthe whole amount of water researchesbeing still under way. That is why we which was flowing into the Depression (the shall be able to presentbelow only a hypothesis cumulated water discharges of Paleo-Chilia regardingthe genesisand the evolutionof the distributary and of the Kitai and Catlabug Danubedistributary system within the DanubeGulf tributaries). areaand the FluvialDelta- On the easternside of the Chilia Promontory, It is difficultto say for sure when and how the within the lagoon behindthe Initial Spit, which main bifurcationsappeared along the Danubeat might have been discontinueand thin enough in Ceatallzmail and CeatalSt.George. The forkingat this area, a lacustrian(lagoonal) spit was formed Ceatal lzmail (Mile 44 upstreamfrom the present (called Rosca'Suez), delimiting southward the day Sulina Distributary mouth) might have availablespace for braiding of the new branch occurredwhen the front of the Danube Blocked formed by the breakingsdescribed above. lt is Deltareached this area. difficult to precise these processesin time but The southernbranch Paleo-Tulceawas joined Chilia branch might have reached the shape with the firm land of NorthernDobrodgea under resemblingthe nowadayscourse 3000-3500 years the Coriolis force action. One can notice a BP. The distributarymight have found a way out remarkableconstancy of the distances(7-10 km) to the sea through the lnitial Spit in almost the betweenthe places rn which the southernbranch same periodof time.

GEA-ECO-MARINA,41997 National lnstituteof Maine Geologyand Geo-ecologyof Romania Proc. Intern. Workshopon "Fluvial-Mainelnteractions" in Malnas,Romania, Oct.1-7, 1996

>-- N. Panin - On the Geomorphologicand Geologicevolution of the River Danube- Black Sea lnteractionZone dgean Fromthis moment on the Chiliadistributary will o phase, d then The Erenciuc materialisedby startintroducing into the littoralarea an increasing same the Erenciucset of fossilbeach ridges, having quantityof sedimentsand building up its owndelta slav a Southwardslightly divergent structure as or - theChilia Delta. re"hit" the St.George I Delta had began its progradation; d into SAINT GEORGE DISTRIBUTARYMOUTH [aries. ZONE EVOLUTION . The Caraorman-pddurepftase con- progradation have The St. George distributaryhad the most tinuedthe following up the of the have complex evolution of all the Danube Delta Paleo-St.Georgemouth zone; aryfor distributaries.Within the structureand evolution of . The Caraorman-satphase represents lrance the DanubeDelta, two phasesentirely related to the last stage of the St.GeorgeI Delta r.Ata the developmentand the activityof theSt. George developmentand progradation.Finally, the y was distributarycould be pointedout (Paninet al., overallprogradation of thisdelta was of about * the 1983;Panin,1989). These phasesare the 10km during a periodof timeof twothousand ,'rand following: years. 1 built l. Duringthe period9,000-7,200 yr.B.P., at the The CaraormanFormation consists of some moresets of fossilbeach ridges as (Fig.1):Jacob, .Chilia mouthzone of the St. Georgedistributary, the first DanubeDelta - the "St.George I Delta"had been PuiuletI and Puiuletll, LuminaI and Luminall, rtance formed. In about two thousandyears the St. Rosu,Rosulet and finally lvancea which represent fulcea GeorgeI Deltaprograded by almost10 Km, the evolutionphases of the next delta- SulinaDelta Chilia averagerate of progradationof its coastalzone and formed its southern wing. These sets hitting being of ca. 5 m/year.This phase could be correspondto the sets formingthe northernflank rereit characterisedby a very reducedDanube borne of the SulinaDelta (Letea Littoral Formation) and ecting sedimentsupply. The progradationof the delta willbe described below. t day )aleo- occurredunder the influenceof the littoraldrift of The "SaintGeorge ll Delta" sedimentsfrom the mouth zones of Ukrainian itsso - the Theformation and the developmentof the "St. rivers Dniepr,the SouthernBug and the place r.The Dniestr. Georgell Delta"took in the last2,000-2,800 Lake years. ll. Aftera periodof almostfive thousand years edas The St. George ll Delta northernwing is when the main distributarywithin the deltaic liated represented by the Littoral Accumulative systemwas the Sulinabranch, which has built up ;ultof FormationSSrSturile, while its southernwing is duringthis time its owndelta - the "SulinaDelta", tnube composedof an importantnumber of fossilbeach 7,200-2,000yr.B.P., the St. Georgedistributary which ridges and beach ridges sets, showing the reactivateditself and started to form the "St. g not successivesteps of the delta shore line rf the Georgell Delta".The developmentof this delta progradation. vhere took placein the last2,000-2,800 years and was The northernwing of the St. GeorgeI Deltais tena simultaneouswith the erosionof the SulinaDelta. a divergent(fan like) I the aswell as with the ChiliaDelta formation. characterisedby structureof it to the Sdriturilelittoral accumulative formation. The The "SaintGeorge I Delta" beach-ridgesets composingthe formation rada main As saidjust above, the St.George I Deltais the areCAsla Vddanei, lepurilor, Morilor, Lung, CAsla ilater first DanubeDelta formed in the period9,000- (the andSt. George.The divergentstructure is due to 7,200yr.B.P., at the mouthzone of the Paleo- the retreatmentof the coastline in the North,the )hilia St.Georgedistributary, at the southernend of the abug SulinaDelta being continuously eroded, while in InitialSpit whichhad closedthe DanubeGulf. At the South,the coast was progradingwith the present,one could observe only the northernwing developmentof the St. George ll Delta. The tory, of this delta.This flank is formedexclusively by SdriturileFormation is composedof sediments rhich the Ukrainianrivers sandy sediments transported erodedfrom the SulinaDelta, most of whichwere th in along the sea shore by littoraldrifting (Fig.3), suppliedby the Paleo-Sulina distributary especially med being representedby the LittoralAccumulative as bed-load. the juxtaposition FormationCaraorman, built up by of The southernwing of the "St. Georgell Delta" rnch an impressivenumber of beachridges. It is is formed,as mentionedbefore, of multiplefossil Fourphases of St.GeorgeI Deltadevelopment beachridges and beachridges sets, pointingout but couldbe evidenced(Fig.2): rape successivesteps of this delta developmentand 9ars . The Initial Spft - the oldestgeologic progradation. There are very evident out and geomorphologicelement of the Danube correspondencesbetween the northernwing beach the Delta- formed12-10 k.yr. B.P.; ridgessets and those of the southernwing,

GEO-ECO-MARINA,A1997 33 Nationallnstitute of Maine Geologyand Geo-ecologyof Romania Proc. lntern. Workshopon "Fluvial-MaineInteractions" in Malnas, Romania,Oct.l-7, 1996 N. Panin - On the Geomorphologicand Geologicevolution of the River Danube- Black Sea lnteractionZone

The main sets of beach ridge within the ing with the distributarymouth section where a southern wing are (from the oldest to the very slow progradationcould be pointed out youngest)(Fig.2): the set Crasnicol,the set Frasin, (averagerate of progradation1.0-1.5 m/year). To the beach ridge Grindac,the set Plopilor,the set be noticed the heterochronous age of the Uncu and Strajina,the set Palade-Cretu,the set Crasnicolset. Chiruscova-Cruhlic, the set TigEnus-Crucea- The Frasin - Sterepova phase representsthe C6lug5ru,the set Buhaz and the arcuatedlateral first phase of a faster advancing of the Sf. mouth beach ridge Sakhalin (lsland Sakhalin). Gheorghe ll Delta, being contemporaryto the These sets are evidencingthe main phasesof the beginningof the ChiliaDelta progradation and of St. George ll Delta developmentduring the last the SulinaDelta erosion. ca.2,800yr.B.P., the ages of differentphases ''C. The Grindac and Plopilor phases are beingdetermined by successivephases when the Sf. Gheorghell Delta Apparently,the progradationof the St. George frontprograded about 6 km. ll Deltawas not uniformin time. The oldestbeach phases ridges set within this delta is the set Crasnicol, During the Plopilor and Uncu that formedabout 2,800 yr.B.P.. At the beginningthe followed,the front of the St. George ll Delta prograded progradationwas very slow:1.0-1.5 Km in ca.800 ca. 3.0 more km. The Plopilorset has a years. Then, the progradationbecame faster - structurediverging to the SW , directionin which, about6 Km in ca. 1,000years, after what the delta afier a lower area of an insufficientsupply of front advancementwent on even faster - more detriticmaterial for forming an entirelydeveloped juxtaposes than 10 Km in the last800 years.The averagerate beach ridges,the set rises and to the - (Uncu of progradationis of 8-9 m/year. Crasnicolset. Three subsets 1, Uncu 2 and Uncu 3) are to be distinguishedin the Uncu The beach ridgesand the sets of beachridges set. The last sub-set(Uncu 3) is continuedby the makingup the southernwing of the St.Georgell Starpulucbeach ridge and farther on by Strajina Delta and showing the steps of development of set. which.in its final end intersectsthe Crasnicol thisdelta, had a very similargenesis and evolution set cuttingit off. The Strajinaset is made up of 4-5 to the Sakhalin lsland arcuate lateral bar. The beachstrands, of which the most recent ones cut ends of these fossil beach ridges were floatingto successivelyoff the olderones. their joiningwith a former alreadystabilised shore - line.The same evolutionwill havethe end of the The Palade Cretu phase is represented by Sakhalinlsland, which is advancingtowards WSW an importantbeach ridges set ; Paladenear by the and will join the presentday coast line in the Sf. Gheorghe branch, continuing farther South- ZStoanesection. westwardby some GAscdbeach ridgesand then, by Greturidge. Corresponding to this set withinthe St.Georqe evolution phases The ll Delta Sir5turile accumulativeformation (the northern The Crasnicol phase. As alreadymentioned, flankof Sf. Gheorghell Delta)is Morilorset. the oldest beach ridges set in the St.Georgell Chiruscova - Cruhlic phase is represen-tedby a Delta is the Crasnicolset, which was markingthe very complexand structurallycomplicated beach coastalline at 2,800yr.B.P. (Fig.2). ridgesset, the main one being Chiruscova.This The Crasnicol set has a complex structure, phase preceded a period of time when Sf. beingmade up of numerousfossil beach ridges. In Gheorghe distributary has divided in several the primary period of its evolution,the set was distributaries(at least two) and created a small correspondingto the lvancea set marking the lobated secondary delta (which we called maximaldevelopment of the SulinaDelta. During "St.Georgesecondary delta A"), resemblingthe this phase,the St.Georgedistributary had a very secondarydelta existing nowadays at the mouth of reduced water and sediment discharge,so the the river branch. According to C1adating, the progradationof the distributarymouth zone was Chiruscova-Cruhlic set corresponds to the slow. This progradationis evidencedby the sub- beginningof our era, being contemporarywith the sets Crasnicol-Belciug(1), Crasnicol-Popilor(2) time when the ancientsgave their geographical I and Crasnicol-Plopilor(3). The sub-setCrasnicol- descriptionsof the Pontus Euxinusand the River Danube. n Belciug is made up of 4-5 fossil beach ridges d converging south-westward,joining themselves Tigdnus phasq with the beach ridges set (9 into one singlefascicle cut by the followingsub-set having the same name, corresponds to the = Crasnicol-Popilor.In its turn, this sub-setis also maximum development of the first lobated cut by the next sub-setCrasnicol-Plopilor. In this secondary delta *A'of the St.Georgedistributary way the Crasnicolset has a complexstructure and (Fig.2).Towards the west the Tigdnusset joins the $ was correspondingto a quite long period of time previousChiruscova-Cruhlic set. s (about800 years),when the shore line remained o There followsBuhaz phase representingthe almost unchanged,except the closelyneighbour- oE lll GEO.ECO.MAR]N A, 2/1997 (9 Nationailnstitute of Marine Geologyand Geo-ecologyof Romania Proc. lntern. Workshopon "Fluvial-Mainelnteractions" in Malnas,Romania, Oct.1-7, 1996

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ABBREVIATIONS PHASTS.AILTAS c:1a6rtS (10)Y;ARs )-l - - e. {PPf0xltlA\E f1 Morcu CI Belc'ug Inrtiois Rll-R6duculel ll C2- [rosnrcol::. Sf.GheorgheI R'S-Rolco -Suet C3 - Plrrp,lor(ro gn,col Sutino Pll-Purulel ll 8r .l Sf.Gheorghe It L ll-Lumrnoll Bll Butroz| ,ll cndll I Chitio Rll-Rin ec ll 8il1 Co5no-Sinoie 02 468 10Km

Fig' 2 The Dan ube Derta geomorp h or ogicar -sed ir,rentoroE lcar structu re Themap outlines he main setsof beaihnoges and ue phasesof dellaevotutjon during Holocene - N. panin - An the Geomorphologicand Qeotogicevotutian of the River Danube Black Sea lnteractionZone

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littoraldeposits: type Fig.3 Areatdistribution of the maintypes of littoraldeposits withrn the DanubeDelta territory. Legend: l.Marine "b", of Danubianorigin, type "b1", of ,,a,,,for"meo by the litoraldrift from tne North,from the riveisDniestr, Dnieper and southernBug; type ';a" a-meanderbelt deposits;b- littoraldiffusion, marked by mixingtypes and "b"; 2. Lacustrinelittoral deposits; 3. Fluvialdeposits: - supplies interdistributariesdepression oepoiits,' 4. Loesslike deposits; L - Directionof the littoralsediment drift; D Mainsediment

GEO- ECO.M A RINA,2/1 597 J5 NationalInstitute af Maine Geologyand Geo-ecologyof Romania Proc. lntern.workshap on "Fluviat-Mainelnteractions" in Malnas,Ramania, oct.1-7, 1996

\ N. Panin - On the Geomorphc'logicanC Geologic evolution ol the River Danube- Black Sea lnteractionZone

end of the secondarydelta "A". The Buhazset has The northernflank of St. George ll Delta is a very complex structure being made up of a representedas mentioned before, by the numberof subsets.Among these, mention should S5rdturilelittoral accumulative formation, The be rnade of : Buhaz | (Vasile),Buhaz ll (Crasotki)- divergent, fan-like structure of this formation Ddnild, Buhaz lll-Ciotic and Fldm1nda. To the demonstratesthe evolution of the coastal area West the subsetsjoin one by one to the previous betweenSulina and St. George in the last 2000 setsTig5nus, Crucea, CSlugdru. years.In the North,the shoreregresses, ihe Sulina Buhaz set representedthe shore line ca. 200 delta beingeroded while in the South,the shore years beforepresent, preceding the secondperiod advancesinto the sea with the St. George ll Delta of forminga lobatedsecondary delta of St. George progradation. lt could be evidenced the distributary (the Sf.George secondary "8" correspondence,as already seen, between the delta),whose evolution continues to our days. main beachridges sets in the SSr6turileFormation Three distinct periods in the evolutionof the and the sets in the southernwing of St. George ll secondary"8" delta couldbe evidenced: Delta. e the first one (*81), very short,coming During the evolution of St. George ll Delta phases right after the Buhaz phase, when the St. there are some when the shore had a greater process Georgeriver branchwas still undivided: stability,the of redistributingthe river sandy sedimentdischarge along the coast o the secondone ("B2"), whichstarted beingmore active.These momentsare: Crasnicol aboutthe middleof the XVlll century(about phase,within the period when the shore did not 1840-1857)when the St.Georgedistributary prograde almost at all due to the smaller dividedin two distributaries:Kedrilles (the contributionin sedimentsof St. George branch continuationof the mainbranch) and Olinca, and Frasin-Sterepova,Palade-Cretu, Chiruscova- whichwe recogniseon the mapsdrawn up in Cruhlicand Buhazphases in the periodwhen the this period.The numberof the distributaries advancementof St. GeorgeDelta was very quick. increased:the Olincabranch split into Turcului and Serednebranches; SULINA DI$TRIBUTARY MOUTH ZONE EVOLUTION r the third one ("Bs'), after the exceptionallyhigh flood which took place in As mentioned before, the initial bifurcation 1897,when a lateralbar began to develop point of the Paleo-Tulcea branch into Paleo- and then to transformitself into an arcuated St.Georgeand Paleo-Sulinadistributaries was lateralbeach ridge - the Sakhalinlsland, locatedimmediately after the impingementagainst the "Dobrodgeanwall" at Preslav (Km.104 The period of forming and developing the upstream the mouth zone of St.George island correspondsto the presentday phase or distributary). After bifurcating, Paleo-Sulina Sakhalin phase of the St. George ll Delta branchwas directedto the East, into a 12-13 Km evolution.The numberof distributariesincreased: long, almost rectilinear,reach. Farther on the a small distributary flowing NE formed from Paleo-Sulinadistributary meander system was Serednedistributary - Rupturabranch, which in a composed by the Maliuc meander bend, the not very long time was almost entirelyclogged. upstreampad of the "BigM" meander,with a small Both secondarybranches, Turcului and Seredne, secondaryloop calledthe "LittleM" locatedwithin whenflowing intothe sea,behind Sakhalin lsland, the pointbar zone of the main meanderand not dichotomise, fork successively forming small far from the confluencewith Paleo-Chiliaarm, frictiondeltas with severalchannels through which and, finally, the downstream part of "Big M' the river water and sedimentsare dischargedinto meanderbend. the sea. Towards 7,204 yr.B.P, the Paleo-Sulina Sakhalin phase began,as alreadymentioned, distributaryreached and broke the Initial Spit, after the exceptionallyhigh flood in 1897. The being since that moment the main branch of the Sakhalin lateral arcuatedbeach ridge developed entire Danube Delta hydrographicsystem. The during a century reaching nowadaysa length of predominanceof Paleo-Sulinabranch lasted ca. ca. 17 km. Dueto over - washingthe beachshifted 5,000 years. During this period of time the inward,while the front of the secondary"8" delta distributarybuilt up a very large delta - the $ulina of St. George distributary prograded being '80's Delta,which progradedmore than 30 Km passing shelteredby the island,so that in the the from a cuspateto a lobate delta as the Sulina islandjoined the front of the secondarydelta near sediment supply overpassed the wave power by the mouth of Seredne branch. The south- regimeof the deltacoastal zone. westernend of the islandis stillfloating having the tendency of approachingthe shore in the area Ciotic-ZStoaneof the DanubeDelta coast.

GEO-ECO-M ARINA, 2/1 997 Nationallnstitute of Maine Geologyand Geo-ecologyof Romania Proc. lntern. Workshopon "Fluvial-Mainelnteractions" in Malnas.Ramania, Oct.1-7, 1996

> N. Panin - On the Geomorphologicand Geologicevolution of the Nver Danube- Black Sea lnteractionZone elta is The Sulina Delta evolution phases duringthis phase, branch which, later on was 1e The Sulina Delta consistsof two very distinct to be calledNaracu Stoma by theancienls. n,The flanks: (1) the northernone, representedby the . The Lefea-Soutfi Megaset represents mation LeteaAccumulative Formation, built up of a very a phaseof a very quick advancingof the I area large number of fossil beach ridges and sets of SulinaDelta. In that time the flux of shore t 2000 beach ridges, most of which are composed by sedimentscoming from the mouthsareas of Sulina Ukrainian rivers born sandy sediments drifted the Ukrainianrivers was very important.In shore along the shore, with a small contributionof this phasethe Magearubranch continued its I Delta Danubiansediments brought about the delta front existence.South-eastward of the Magearu the zone by Sulina Delta distributariesflowing on the therewere formed the beachridges lfim and rn the left side of the main Paleo-Sulinabranch (Fig.3), Pocora-Sinehradca,made up of Danubeborn nation and {2) the southern wing, composed by fossil sedimentbrought by the mentionedabove rrgell beachridges, a numberof whichtaking part of the branch. During the sub-phase Pocora- Caraorman Formationstructure and built up Sinehradcatwo more secondarybranches (Fig.3). appearon the left side of Sulina main Delta exclusivelyof Danube born material So, phases distributary,branches we calledMovilS and hada for describingthe evolution of SulinaDelta present Sinedrahca(Boreion Stoma and Pseudo- rg the it is necessaryto the structureof the two stomosrespectively in the descriptionsof the c0asl main LittoralAccumulative Formations Letea and ancients); snicol Caraorman, representing the northern and, id not respectively the southern wings of the delta . The Letea-NorthMegaset represents maller (Fig.2). the continuationof the Sulina Delta ranch The structure of the Letea Littoral development,with the materialfrom the icova- Acc u mu lative F ormati on littoraldrift from the Ukrainianrivers and with rnthe In the building up of the Letea Formationwe Danubiancontributions introduced in the luick. can distinguishthe following fossil beach ridges shorearea through the secondarybranches onthe leftof Sulina,contributions which could IONE sets which represent,at the same time, phasesin the Sulina Delta evolution"To these phases are be recognisedin the Schiopu,Cherhanoi, Uje addeda numberof beach ridgessets representing andSulina beach ridges. These beach ridges :ation - representsub-phases of the Letea North taleo- steps in the developmentof the next delta Delta Chilia,which will be describedbelow (Fig.2). phase.After the Sulina sub-phase the number was of secondarybranches on the left side of o phase, Iainst The Rdducu set or constituted Sulinareduce from three to two- the Magearu n.104 in the western part of some beach ridges branchwas clogged and its mouthis blocked belongingto the InitialSpit and corresponding "!orge by new beach ridges (Fig.z) made up of iulina to Erenciuc, Caraorman-pidure and Ukrainiansedimentary material. On the right 3Km Caraorman-sat sets in the Caraorman (southern)side of the Sulinadistributary there t the Formation structure, which representsthe isstill lmputita branch. flank of St. George I Delta, and in was northern . the eastern part a number of ridges The Rosefff West and Roseffi Easf the Magasets correspond to the maximum small representingalready the beginning of the SulinaDelta advancing; developmentof the Sulina Delta, when its end vithin exceededwith morethan 10 Km the preseni I not t The Hudacova Sef presentstrough the day shoreline of the DanubeDelta. These arm, orientationof the constitutivebeach ridges setsare alsomade up of Ukrainianmaterial. IM" the beginningof the quite quick advanceof Afterthe EastRosetti phase, the SulinaDelta the SulinaDelta; startedto be eroded and in the North the ulina . Rdduculet l, Rdduculet ll and developmentofthe Chilia Delta began. Spit, Rdduculet lil Sets represent successive The structure of the CaraormanLittoral f the phases of the Sulina Delta progradation.In Accumu lative Formation The phase first this of developingthe secondary parts I ca. distributaryof Sulina-Magearubranch was As shownabove, the westernand central the formed. To the east of Magearu branch, of the CaraormanFormation representthe ulina betweenit and the main courseof Sulina,the nodhernflank of the St.GeorgeI Deltaand the (western) (the ;srng CdpdtAnS-ChirilSbeach ridge was formed of four first sets sets belongingto the ulina Danubiansedimentary material discharged in InitialSpit, Erenciucset, Caraorman-pddureand phases ower the shore area by the mentioned branch. Caraorman-satsets) are evidencingthe of part Southward the main distributaryof Sulina,a developmentof thisdelta. The eastern of the secondary branch - imputita - was formed CaraormanFormation consists of somemore sets of fossil beachridges as: lacob, PuiuletI and

GEO-ECO.MARINA,41997 Nationallnstitute of Maine Geologyand Gea-ecologyof Romania Proc. Intern. Workshopon "Fluvial-Mainelnteractions" in Malnas, Romania,Ad.L7, 1996 N. Panin - On the Geamorphologicand Geolagicevolution of the River Danube - Black Sea lnteractionZone

Puiuletll, LurninaI and Luminall, Rosu,Rosulet the Puiuletll ridgesand the Luminall set is and finally lvancea and represents evolution cutting,at its turn, the sets Lumina l, Puiulet phasesof the next delta- SulinaDelta, forming, at ll, Caraorman-satand partially Caraorman- the same time, its southernwing (Fig.2).These p5duresets. phases sets and will be describedbelow. . Rosu and Rosulef sets evidence the . lacob set and phase correspondsto continuationof the rapid progradationof the the beginningof SulinaDelta formation and Sulina Delta, The Rosu phase could be progradation.The set has a slightlyNorthward dividedin two subphasesA and B. The Rosu divergentstructure, consisting of three sub- set, at its southernend is cuttingthe ridgesof sets; lacobA, lacob B and lacob C separated Lumina ll set, while the Rosuletset cuts off one from the other by elongated lakes the Rosu, Luminall and Caraorman-pidure occupyingthe inter-ridgedepressions; sets. t Puiulet I and Puiulet l/ sets are t lvancea sef represents the maximal successive phases of Sulina Delta front progradationphase of the SulinaDelta, which progradation.As at that time the preceding occurred approximately3,000-2,800 yr.B.P. deltaSt.George I becameeroded, the Puiulet The lvanceaset is cuttingoff the Rosuletand I sets are cutting off the ridges constituting Caraorman-pdduresets. The followingtable the lacob set, and the Puiuletll are cutting showsthe Sulina Delta developmentphases the ridges of Puiulet l, lacob and the last and characteristics as they could be ridgesof Caraorman-satsets. evidencedby makingthe correspondenceof the two . Lumina I and Lumina ll sefs are delta wings main beach ridges sets describedabove. showing a very rapid progradationof the SulinaDelta. The erosionof the St.GeorgeI Delta continued:the Lumina I set is cutting

Table 1. SulinaDelta evolution phases and geomorphologiccharacteristics t*c Evol. Mainsets 0f fossilbea6h ridoes Age Geomorphologic ohases Northernwino Southernwinq Vr.B,P. characteristics Rdducu lacob 7,200 cuspatedelta. 1 distributarv tl Hudacova PuiuletI cuspatedelta, 1 distributary Il RiduculetI Puiuletll cuspatedelta. 1 distributarv IV Rdduculetlll + Cip6tini- LuminaI 6,000 lobatedelta, 3 distributaries Chiril6 LeteaSouth + Pocora- RosuA lobatedelta, 5 distributaries Sinehradca VI LeteaNorth + Schiopu- RosuB 4,900 lobatedelta, 5 distributaries Movild vlt LeteaNorth + Sulina Rosulet lobatedelta. 5 distributaries vill RosettiEast lvancea 2,800-2,500 cuspatedelta, 4 distributaries

CHILIA DISTRIBUTARYMOUTH ZONE . The Sfisfofca West I set has a slightly EVOLUTION divergentstructure to the North, the beach ridgesmaking it up followingthe beginnings The Chilia Delta of the Chilia Delta progradation.The beach Since the period of time when the Chilia ridges are made especially of Danubian distributaryreached and brokethe lnitialSpit (see material and, subordinatelly,of Ukrainian Chapter 2 of the present paper), a new delta material brought about by the littoral drift beganto form andgrow - the ChiliaDelta (Fig.2). from NE (Fig.3).The phase could be placed in the period3000-2500 years BP; The Chilia Delta is situatedNorth and East of the LeteaLittoral Accumulative Formation. whose . The Sfisfofca West Il set follows on west side represents,as described above, the the progradation of the Chilia Delta, northernwing of the Sulina Deltaand the eastern correspondingto its developmentin between part correspondsto the ChiliaDelta formation and 2500-1000years B.P. In this periodthe delta developing. got a lobatedshape, which demonstratesthe fact that the Chilia distributarybecame the The phases Slfthe Chilia Deltaevglution:

GEO.ECO-MARI N A, 2/1997 Nationallnstitute of Maine Geologyand Geo-ecologyof Romania Proc. lntern. Workshopon "Fluvial-Marinelnteractions" in Malnas,Romania, Ad.1-7, 1996

Er N. Panin * An the Geomorphologicand Geologicevolution of the River Danube- Black Sea lnteractionZone

set is distributaryof the deltaicsystem, with a between1000-500 years B.P. The southern ruiulet main very important water and sediment part of this set cuts off successivelythe )rman- discharge.Starting with the SfistofcaWest ll beach ridges of the Sfistofca West ll, Phase,the constitutivematerial of the beach SfistofcaWest l, Rosetti East sets as well ce the ridges making up the following sets is as the last ridgesof the RosettiWest set; of the exclusivelyDanube borne, the materialfrom . The Cardon Wesf set follows on the rld be the Ukrainian rivers stopping North of the ever quicker progradation of the Chilia r Rosu ChiliaDelta, forming the beachridges of the lobated delta. The set cuts off the beach gesof JebrianyFormation. In the South,the Sulina ridges of the Sfistofca East, Rosetti West its off Delta is eroded on and this fact is and Leteasets; lEdure materialisedby the cuttingoff the previously formed Rosetti East and Sfistofca West I . The Cardon East set developed sets by the SfistofcaWest ll set of beach probablyin the 16th-17thcenturies. lt cut off aximal ridges; the beach ridges of the Cardon West and which Leteasets. After the formationof the Cardon . /f.B.P. The Sfistofca East sef is strongly East set, the Chilia Delta prograded so et and divergentto the nodh-east,corresponding to quicklythat coveredentirely the beachridges table a quick advancementof the ChiliaDelta in whichhad beenpreviously formed. rhases lbe rce of REFERENCES cAsrEscu,P.,Dnrcn,8., 1985, Delta DunSrii.Harta s sets turistic6.Ed. Sport-Turism, Bucuresti. Auuazov, A.A., BoruonRC., DrAcoNU,C , GHEDERTM, GRUMAZESc,H., SrArucescu,CoRruelrn, Neori-cu, E., VETURTA,MrHArLov, A.N., Mrn, P., NrcnrroRov,1.D., 1963, Unit6tilefizico-geografice ale Deltei Dunirii. RAr,LA., Rooror'rov,N.A., Srnrurscu,S., Srnrurscu, Hidrobiologia,lV, 129-162,Bucuresti. V., VAGHTN,N.F., 1963,Zona de virsare a Dundrii. MorfografiehidrologicS, 396 p Ed TehnicS, Lepsr,1., 1942, Materialepentru studiul Deltei Dundrii. Bucuresti. Parteal-a. Bul.Muz.RegionalBassarabia, 10, 94- 325,Chisin6u. ANrpA, GR., 1915, Wissenschaftliche und wirtschaftlicheProbleme des Donaudeltas.Ann. LITEANU,E., PRIoAIAN A, BnIrAc G,1961- '1 lnst.Geol. Rom., Vll, , BBp . Bucuresti. Transgresiunilecuaternare ale MSrii Negre pe teritoriulDeltei Dundrii. St. Cerc.Geol., 6, 4,743- Bnnu,A.C., 1965,Contributii la cunoastereavdrstei si 762,Bucuresti. evolutieiDeltei Dundrii. Hidrobiologia, 1.6, 259-278, Ed.Acad. RPR, Bucuresti. LrreRnu,E., PRTcAJAN,A, 1963,Alcdtuirea geologici a DelteiDundrii Hidrobiologia, lV, 57-82,Bucurestr. BnNu,A.C., Ruoescu,L., 1965 DeltaDundrii, 295 p., Ed St.,Bucuresti. MRRroNrue,Euru. de, 1931, Europe Centrale. ll-dme partie,786-787, Paris. Bnrrs, C., 1953, Rotationaltheory of deltaformation. Bull AAPG,37, 9,2119-2162. Pnxrx, N., 1972, HistoireQuaternaire du Delta du Danube. Essai d'interpr6tationdes facids des Boruonn,C., 1973, Date noi cu privirela scurgereade deltaiques. IRCM,4, 5-15, aluviunigrosiere pe bratulSulina. St. Hidrol.lMH, dep6ts Cercet6rimarine Constanta. XXXV|l,67-89, Bucuresti PANfN,N , 1974, Evolutra Deltei Dun6rii in timpul BoruoaR,C., SrerE l , RovENrA,V, 1973,Marea Neagrd Holocenului,Inst.Geol St. Tehn Econom.,Seria H, in zona Iitoralului romdnesc. Monoqrafie , Geol.Cuaternar., 5, 147421, Bucuresti. hidrologic6.lMH, 516 p., Bucuresti. Pnrutru,N., 1976,Some aspectsof fluvialand marine ightly Blrnxu, M., 1963 Observatiiasupra evolutierzonei processesin the Danube Delta. An. Inst, Geol. each Histriain ultimiletrei milenii.Prob. Geogr., lX, 45- Geophys,50, 149-165,Bucuresti. nings 56, Bucuresti. PnrurruN., 1983,Black Sea coast line changesin the each BRarescu,C., 1922, Delta Dun5rii.Geneza si evolutia last 10,000years, A new attempt at identifyingthe rbian sa morfologicdsi cronologicd.Bul. Soc Reg Danubemouth as describedby the ancients.Dacia, inian Geogr, 41, 3-39,Bucuresti. N.S, XXV|l,1-2, 175-184, Bucuresti. drift Bnnrescu,C , 1942,Oscilatiile de nivelale apelorsi 1989, Delta. evolutionand aced bazinuiuiMdrii Negre. Bul. Soc. Reg. Geogr, LXl, 1- Pnrurru,N,, Danube Genesis, 112, Bucuresti. sedimentologyRev. Roum. G6ol. G6ophys. G6ogr., Ser,G6ographie,33, 25-36, Bucuresti. ColeunN,J M., 1982, Deltas.Processes of deposition son Perurru,N., 1992, lmpacts of expectedclimate change relta, and models for exploration.Second Ed., 124 p., Boston. and sea-levelrise on RomanianBlack Sea shore, t/een especiallyon the Danube Delta area. UNEP lelta CorEr, P., 1960, Evolutiamorfohidrografic6 a Deltei (OCA)WG19, Inf B, 11p., lstanbul ; the Dundrii(O sintezSa studiilorexistente si o nou6 the interpretare).Probl Geogr.,Vll, 53-81,Bucuresti.

GEO.ECO-MARINA,/1997 ?o Nationallnstitute of Maine Geologyand Geo-ecologyof Romania Proc. lntern. Workshopon "Fluvial-MaineInteractions" in Malnas,Romania, Oct.1-7, 1996

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