An Abrupt Drowning of the Black Sea Shelf at 7.5 Kyr Bp

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W.B.F. Ryan et al. - An abruptdrowning of the BlackSea she/faf 7.5 Kyr B.P.

AN ABRUPT DROWNING OF THE BLACK SEA SHELF AT 7.5 KYR BP

WilliamB.F. Rvnru1,Walter C. Prrunrulll1, Candace O. MR.loR1, KazimierasSHrurus', Vladimir MoscRtrruro', Glenn A. JoruEsr, PetkoDrMrrRova, Naci GonURs, Mehmet SRrcruqs & Hiiseyin Ytice SEvlR6

1 Lamont-DoheityEarth Observatory of ColumbiaUniversity, Palisades, NY 10964,USA 'Southern. Branchof the P.P. ShirshovOceanology Institute, Gelendzhik-7, 353470, Russia 3 TexasA & M Universityat Galveston,Galveston, TX, USA a Bulgarian-Academyof Sciences, lnstitute of Oceanology,9000 Vama, PO Box 152,Bulgaria " l.T.U.Maden FakUltesi Jeoloji B6lUmU, 80626 Ayazga, lstanbul, Turkey 6 SeyirHidrografi ve OsinografiDairesi, 81647 gLiUuXtu, lstanbul, Turkey

Abstract: During latest Quaternaryglaciation, the BlackSea becamea giant freshwaterlake, The surface of this lake drew down to levels morethan 100mbelow its outlet.When the Mediterraneanrose to the Bosporussill at 7.5 kyr BPl, saltwaterpoured through this spiltway to refillthe and submerge,in lessthan a year,more than 100,000Km'of its exposedcontinental shelf. Key words: continentalshelf, erosion surface, climatic condition, faunal succession, radiocarbon data, Neoeuxine Lake, Black Sea

the ecology of the fossil molluscs2s' 32' INTRODUCTION ^^ tt, dinoflagellatqs33and diatoms3a' from strongly The earliestwritten accountson the Bosporus negative O'o''o isotopic ratios^^inthe carbonate and DardanellesStraits, date to the Roman era'-" component of the sediments'o, and from the and chroniclea catastrophicbreakthrough of the chemistry of pore waters drawn out of the sea. The winding course of both straits, their Neoeuxine-agestrata3T-3e. terraced cross-sections, and their dendritic Near-shorelittoral deposits2627' 40' 41, with tributarieswere interpretedby nineteenthcentury 6 radiocarbonages of the msllusc shells spanning geomorphologistss as indicative of a stream 19 to I kyr BP, have been found at depths origin.Today the channelis submerged 9eeply between -93 and -122 m. Linear steps that and pafilyfilled with sediment'-'"to a sill depthof- resemblethe profilesof beachterraces have been 33 m". lt hosts a two-way exchange of water mapped for tens of km along the outer shelf betweenthe partly marineBlack Sea and the fully between-90 to -110 m. A substantiallowering of marine MediterraneanSea11-16. In fact, the the pastlake levelto at least-110 m has also been northward-flowingundercurrentlT had long ago inferredfrom the discoveryof formerlyentrenched been known to mariners who lowered baskets rivervalleysa2-45 which are now partlyfilled in with laden with rocks into its core to tow their vessels estuarinedeposits under the bedsof modernrivers upstreamtoward the BlackSea18. as they approach the coast. Boreholes in the '' Dated fossil coral reefs in the Caribbeanle-21Kerch Strait'o have recovered coarse gravel showthat, at the time of the maximumexpansion withfluvial fauna at -62 m in the streambed of the of continentalice sheets around 20 kry BP, the ancient Don River > 200 km seaward of the surfaceof the globalocean was at -120 m. Thus presentriver mouth. Mud, silt and sand on the prior to the glaciers,the Black Sea was without basin plain dated between I to 7.5 kyr BPas (Fig.1). connectionto an externalocean ln the contain .A significant cgmponent of reworked absence of a saltwaterinlet it had transformed plan 23, molluscsae,microfossilsso and detritus33 itself into a giant freshwater body22 dwarfing washed downslope from coastal swamps. The anymodern lake in areaand volume. contaminationof former proximityof wetlandsto NEOEUXINELAKE the headsof the submarinecanyons which indent the shelf edge and act as conduitsfor sediment glacial postglacial Lacustrinedeposits of and transportto the basinplain. The inferredrelocation age, assigned to the local Neoeuxine"-'" of the coastline in the vicinity of the current stratigraphicstage of the late Quaternary,have shelfbreak is shown in Fig.2, along with the beencored at a large numberof sites on the floor ubiquitousdistribution of loessand alluvialsoils on of the Black Sea extendinofrom the continental the broadand emergedcontinental shelf south of plain26'2e-31 shelf26-28to the centerof itibasin at a Ukraineand throughoutthe Sea of Azov27. depth of 2.2 km. The fresheningis deducedfrom

GEO-ECO-MARINA,41997 Nationallnstitute of Maine Geologyand Geo-ecologyof Romania Prcc. lntern. Workshopon "Fluvial-Mainelnteractions" in Malnas,Romania, OcLl-7, 1996 W.B.F. Ryanet al. - An abruptdrowning af the Black Sea she/f af 7.5 Kyr B.P.

Fig.1 The BlackSea lake with its reconstructed9 kyr BP shoreline(blue/green boundary) at -120 m belowthe moderncoastline (bold line).The regressionportrayed here has exposedthe entirecontinental shelf and the Seaof Azov,thereby reducing the regioncovered by waterto two-thirdsof its presentextent.

Fig. 2 The arid landscapeof the Neoeuxinestage in the BlackSea deduced from the lithologiesof morethan 250 sedimentcores'u' ". The soils of the emergedshelf are dominatedby wind-blownloess (wavypattern) and the alluvialdeposits (stippled pattern) of meanderingrivers that flowedhundreds of km beyondtheir present mouths to shelf-edgedeltas. The ancientlittoral zone (brickpaftern) was exploredduring two surveysof a jointRussiai US expeditionin 1993.The linewith smallcircles extending north-west from the survey westof the Crimeaindicates a transectof newcores whose lithr.rlogies and ages are portrayed in Fig.6.

116 GEO.ECO.MARINA,41997 NationalInstitute of Marine Geologyand Geo-ecologyof Romania Proe. lntern. Workshopon "Fluvial-Mainelnteractions" in Malnas,Romania, Oct"1-7, 1996

.L-_ W.B.F.Ryan et al.- An abruptdrowning of the Blac[,Seastlerf af 7.5Kyr B.P.

1220'E 45000'N

44050',N I formerriver channel (Fig. 5) I' Oll corelocadon shelf edgewest l+\ Ii .4 of the Crimea r,#tAune fietd(Fig.5) \4' scismicline (Fig.4)

(bold dby Fig.SThe west Crimea survey, contoured in metersbelow present sea level. A beltof dunesliee between the -70 and -80 m isobath. Core14 at- 140 m containsan erosionsurface formed by emergence of thelake bottom.

ttl A 9 710

2ltr DP craages 2 ,/

of rn) ey Fig.il Interpretationof selsmic profils A-A" lllustraungan erosionsurface (bold llne) which has truncated an underlyingglaolal-age deltaicdeposit and which ie ubiquitousin the west Crimeasurvey everywh€re above the- 156 m isobath.The cores obtainedin 1993 are proJectedontg the profile (llne6 showingthe depth of penetrationare those cores close to the profile,circled numbers are those further auny). In the bottomhalf of the figurethe reflectionprofile has been proJectedInto an age-distancespace to emphaeizethe major hiatus (outlinedin bold) formed by the regr€gsionsof the lake. The diamondsymbols locate AMS radiooarton-dat€dlevels in the cor€s. Two transgressionsare apparent,one starlingabout 15 kyr BP and the secondat 7.5 yr lcyrBP. The latterdrowns the shelf from -123 to49 m in the diagramin an interval,which appearsto be instantaneousgiven the resolutionof the AMS dates.

GEO-ECO- MARINA, 2/1 997 Nationallnstitute of Maine Geologyand Geo-acologyof Romanla Proc. Intern. Workshapon "Fluvial-Mainglnteractions" in Malnas.Romania. Oct.1-7. 1996 W.B.F. Ryan ei al. - An abruptdrowning of tha BlackSea shelf al 7.5 Kyr B.P

NEW DATA It truncates strata with a clinoform geometry The submerged shorelines on the northern diagnostic of an alluvial fan, flood plains, shelfof the BlackSea were revisited in June,1993 meandenngriver beds,and deltas.The surfaceis by a joint Russian/Us expedition.Two regions locallycovered with dunes(Fig.5) attributed to the were surveyedwith more than 1,000 km of high- wind drift of beach sands.The erosionsurface is resofutionsub-bottom reflection profiling and 24 widelystrewn with a shellygravel having a sharp new gravitycores (Fig.1). One surveylies southof top contact and gradational base. The gravel -45 the Kerch Strait in depthsbeyond the present component is comprised almost entirely of m isobathin a regionwhere the ancientDon River bleached and abraded fragments of a freshwater would have flowed to reach the freshwaterlake. molfusc (Dreissenarostiformis distincta). The most The other (Fig.3)is situatedwest of the Cfimea at common fragment is the robust hinge portionof -65 depthsbelow the m isobathwhere the ancient the valve.At depthsbelow -95 m the shellygravel Dneiperand DneisterRivers might have followed overliesa mud with sand-richlayers containing the routeslo the lake'sedge. same mollusc as found pulverisedin the shelly Widespreaderosion surface gravel.However, here the fragilemollusc has both valves attached shows An erosionsurface (Fig.4) reachesacross ihe still and no sing of abrasion or transport.The exteriorof the shell sholf to a depth of -'156 m. This unconformilyis is coatedwith a brown of what mappable without interruption throughout both hairy scum appears to be fossilisedalgae, which can be easily survey areas and along the track of the survey removedwith a fingernail In five cores (Fig.6) -95 vesselto and from the port of Gelendzhik. below the m isobath this shell-bearing er osion suf face sand restson a firm, dry clay in which one could identify river desiccationcracks filled with plant detritus and sur- chan:rel rounded by the preserved roots of plants and shrubs. The sand, rnud and clay layers contain gastropods (Viviparus viviparus) indicative of fluvial environ- ments. The fauna in the gravel, sand and mud are characteristicof the fresh- dunes waterNeoeuxine stage of the late Pleistocene Black sea25'5t.Mud cracks at -99 m, algaeremains at -110m, roots of shrubs in olace at - 123 m, and pebble gravel \,'i"' with neriticspecies to -140 m *.Jf1;:'; ' r are all indicatorsof a former 3:'' ;; 7m alluvial to coastal €f, oslon suriaCE,-, environment during the $, ',i 450 m Neoeuxineinterval in regions now deeply submergeo underwater.

erosion zurface Fig.5 Seismic profilesiliustrating examplesof a burled river channel incisedinto the erosionsurface (top), asymmetricalsand dunes on the erosion surface (middle) and the marked truncation of steeply incline delta toreset deposits (bottom). In everycase, there is a uniform drapeal Holooene mud with no evidence of reworkingby surf zone of a gradually transgressingshoreline.

118 GEO.ECO.MARINA,41997 Nationsllnstitute of Maine Geolagyand Geo-ecologyof Romania Proc.lntern. Wotkshop on "Fluvial-Mainelnteractions" in Mahas, Romania,Oct.1-7, 1996

^\-_ W.B.F. Ryan et al. - An abruptdrowning of the Black Sea she/f al 7.5 Kyr B.P

to -8 %o).This shift from older and more negative 2r12611810 leometry 0 to youngerand more positivevalues is coincident ptains, with the first appearanceof marine molluscs.A [rface is -50 similarshift occursin coresfrom the basin plain52 d to the where an offset of the same magnitudeslis again lrface is -100 abruptand accompaniedby the appearanceof the a sharp marine microfossils (inclyding coccolithssO, -9- -rru. -^ gravel t diatoms3aand dinoflagellates33). rety of o The detritus in the shelly gravel can be shwater .s -200 artificially produced in the laboratory by a ]e datedat 7.5 kyr BP most moderately-agitatedwashing of the underlying rtion € -zso Holocene of coquina-bearingNeoeuxine mud and sand, a / gravel shellygravel -300 Sl process which easily pulverised the delicate ring Neoeuxine the ! molluscs.The shellygravel is everywheredraped shelly dry clay and sand -350 ffi with a low-energymud deposit as evidenced by as both 0 shells that are intact. Previous workers have brasion invariably associatedthe manufacturingof the edwith -100 shellygravel with a slowly advancingshoreline of to be the Late-Pleistocene- Holocene transgression. $ with Nonhwest Southeast -95 However, it's desiccated nature and abundant m plant debris is not indicative of a subaqueous rearing Fig.6 The transectof newcores whose locations are shownin origin and instead suggests a regressive lag ry cray Fig.2,and which extendfrom -49 to -160 m belowpresent sea lentify level.The base of the marineHolocene Black mud, where dated, deposit. is everyltrhere7.5 kyr BP" The freshwaterNeoeuxine sediments d with onlapthe erosionsurface and the underlyingstiff clay and have AMS radiocarbondating sur- beenpartly preserved from erosionbelow -90 m in the surveyare. The timlng of the onset of the Holocene ierved The shelly gravel is the subaerialweathering product of the depositionhas been determinedwith Accelerator Neoeuxinecoquina-rich sands and mud. 1rubs. Mass Spectrometer (AMS) radiocarbon dating clay Faunalsuccessions methods.Ages have been obtainedin a suite of lpods The sedimentoverlying the erosionsurface is a coresby samplingonly single intact molluscs (both indi- dark organic rich mud with abundant brackish valves still articulated)which were removedfrom viron- (Monodacna caspia, Dreissena polymorpha) to the initial0.5 cm of the black mud on top of the the more marine(Cardium edule), molluscs. The latter shellygravel. I are emigrantfrom the Mediterranean.A resh- speciesis an few cm above the shelly gravel, the briefly rf the flourishingbrackish-water molluscs disappear and 2.0 llack o years by , -99 are replaced with a few hundred prefer 0m, additionalmarine species that still higher at- salinity, e.9., Mytilaster lineatus, Mytilus t.6I avel galloprovinaalis.The first appearance of marine f0m species directly above the shelly gravel defines 'mer the stratigraphicdatum in the Black Sea for the lstal baseof the Holocene2s.Thq last appearanceof D. the rostiformisin the gravel indicatesthe end of the depth in corc (cm) ions Neoeuxinestage of the Late Pleistocene2a'46 geo Physical and chemical shifts Fig.7 Variationsin moistureand wet bulkdensity in core AK24-93 Moistureand bulk densitymeasurements made fromthe Kerchsurvey area. The Holocenemarine mud has a high shipboard on the fresh cores (Fig.7) show an water content and low density indicative of a subaqueous change from high-water-contentand low- sediment,whereas the Neoeuxineshelly gravel and stiff clay has rBng abrupt beendewatered through subaerial exposure. The watercontent is nnel density Holocene dark mud above the shelly measuredby a nuclearresonance method and its units are the lop), gravelto significantlymore-desiccated and higher- periodof vibration. the valuesfor the underlyingNeoeuxine-age the density Thecalibrateds3 radiocarbon ages (Table 1) are t,ne gravel,sand, mud and clay layers.The dry clay is indistinguishablefrom each other (7.5-7.6 kyr BP) ln stiff and can be cut only with difficulty using a to withinthe tabulatederror ranges (* 45 y) over eol knife. The stable isotopicratios of O'o"o measure waterdepth range from -49 to -123 m. Thus,the of the Holoceneblack ally on individualmollusc valves in apparentmarine intrusion across the continental mud are significantlymore positive(-1 to 0 %o) shelfis virtuallyidentical in tjnlingto the onsetof 'o. thanthose from the Neoeuxinesand and mud C4 anoxiathroughout the basin*o Thedates in the

GEO-ECO-MARINA,41997 I tY Nationallnstitute of Maine Geologyand Geo-ecologyof Romania Proc. lntern. Workshopon "Fluvial-Mainelnteractions" in Malnas,Romania, Oct.1-7, 1996

) W.B.F. Ryan et al. - An abruptdrowning of the Black Sea shelf af 7.5 Kyr B.P.

Neoeuxinesands and mud (Table2) rangefrom 10.8to 8.3 kyr BP as mightbe expectedin a lag 14.7to 10.0kyr BP. Thosein the shellygravel deposit. havestratigraphically inverted ages in the rangeof

Table 1 AMS radiocarbondatesl of Holocenefauna directly above the shellygravel. Core Water Depthin Species Conventional CalenderAge Accession Depth(m) Core(cm) Analysed Ase (yr.BP) (yr.BP) Number AK3-2-93 49 49 M.caspia 7,13Q* 40 7,500+ 115 os-2321 AKl-93 68 134 M"caspia 7,224+ 40 7 580+ 115 os-2357 AK12-93 78 144 C.edule 7,140+ 40 7,510* 115 os-2325 AK8-93 99 104 C.edule 7,140* 40 7,510+ 115 as-2322 AK9-93 1?3 92 C.edule 7JjAL40 7,474* 115 os-2323

Tabte 2 AMS radiocarbondatesi from fauna in the Neoeuxineshell gravel*, the underlying Neoeuxinesand and mud lavers*and the stiffclav truncated bv the erosionalsurface=. Core Water Depthin Species Conventional CalenderAge Access. m Core(cm \ge (yl€!) .BP Number AK10-93 '106 145 D.rostriformis 11,350 * 45 12,800+ 50 os-2324 AK7-93 'l0B 95-97* D.rostriformis 10,400r 55 11,400* 160 os-2357 AK7-93 '108 100-1 04" D.rostriformis 8,250+ 35 8,617+ 80 os-2358 AK7-93 108 140-145- D.rostriformis 10800 * 65 12,20A* 120 os-2359 AK14-93 tau D.rostriformis 10,000* 50 10,800+ 100 os-2326 AK'14-93 140 215= D.rostriformis 14,700+ 65 17,100* 95 os-2360

The documentationof Neoeuxine shorelines evaporation,the lake'scontent of bi-carbonatewill alongthe shelf edge of the BlackSea bringsinto increase.The mollusc Didacna moribunda, lound doubt the scenario, proposed by many in the Neoeuxinedeposits is thought to be an researchers55-5e,of a flow-through giacial-age indicatorof such increasingalkalinity"'. A negative freshwater lake with a continuous outlet. For waterbalance could occur if the riversupply to the steadydischarge the floor of this outletis required Black Sea had diminishedfor reasonsother than to have been as far belowtlp presentsea surface local precipitation.Radiometric dates of moraines as the ancient shorelines"".However a major of the Barentsand Scandinaviancontinental ice problemgenerated by hypothesisinga deep sill is sheetsrecord their retreatbetween 15 and 10 kyr the observed long delay betlueen the rise of BP62'63.Their peri-glaciallakes did not maintain eustaticsea level of the externalocean above - drainageto the south. Beginning12-13 kyr BP 120 m isobathat 18 kyr BP and the first entry of these lakes found alternateoutlets, either to the marine fauna from the Mediterraneansome ten west where they fed a large lake in the Baltic thousandyears later when the outlet would have regionwith a spillwayto the North Sea, or to the been a hundredmeter deep channel.Furthermore Arctic via gaps between the ice sheets. The a Black Sea with a deep outlet should have YoungerDryas (12-11kyr BP) is an intervalin experienced a post-glacialtransgression of its Europe.ard the Near East of marked coolingand margins in synchroneitywith the externalocean, aridityo"-o'.Elevated levels of wind blowndust from therebyleaving the sedimentaryand faunalrecord Asia and Europe are^foundas far away as the of a progressivelandward advance of its coastline Greenlandice capoo-'u.In the CaspianSea the acrossthe shelf. lnstead,one observesonly the Younger Dryas coincides with the Mangyshlak regressionto -133 m during which the Caspian abruptappearance 7.5 kyr BP age black mud on ' ) top of the severely desiccatedNeoeuxine shelly shrank to 3Ao/oits present surface area""' gravel. transformingthe exposed northern shelf into a desert landscapewith wind-blownsand dunes. A Arid ClimaticConditions belt of semi-deseftterrain extendedto the west However, if one considersthat the lake level along the northern and southern sides of the might..have dropped upon occasion below its Crimea, blanketing the exposed Caspian and o outlet"'rv . the riseand fall of itsshoreline would Black Sea shelves with loess deposits. The not need to be coupledwith the externalocean. parchedconditions reached into Romania where Such a drawdownrequires a negativehydrologic fossilsand dunes qre still preservedon terracesof balance comparableto neighbouringpresent-day the DanubeRiver''. In Syria,the materialremains CaspianSea. Given adequatetime and sufficient of humansedentary occupation during the

120 GEO-ECO-MARINA,21997 NationalInstitute of Maine Geologyand Geo-ecologyof Romania Proc. lntern Workshopon "Fluvial-Mainelnteractions" in Malnas,Romania, act.1-7, 1996

L-_ W.B.F. Ryan et al. - An abrupt drowningof the Black Seashelf at 7.5 Kyr B.P

lag and in the formationof a densitystratification in the water column that quickly tume_dthe sea anoxic everywhere below -200 m"4. A fast submergenceof the landscapewould explainthe preservationof shelf-edgeriver channelsand sand dunes from the destructive processes of the surf zone. The migrationof the coast far inlandwould also have caused the observed simultaneous shutdownin the deliveryof detritalcarbonate and reworkedmaterials to the shelf and the basin plain at the time of the marineinvasion and for the, That the inundationwas by water with an already increasedsalinity is corroboratedby the fact that, unlikethe deep-basinsediments, there is only a very slight depletion of interstitialchloride with depth in the subsurfaceof the shelf76.Apparently the transgressingsea percolateddirectly into the open pore spaceof the highly permeableand dry Neoeuxineshelly gravel and sands". A catastrophicdeluge through the cataractsof a narrowinlet is fully capable of cutting into the bedrockof the Bosporusand DardanellesStraits (Fig.8). Where drilled and sampled in the Bosporus Strait, the initial fill on the eroded bedrockin the bottomof this gorge containslarge vill blocksand bouldersof the adjacentDevonian and gravel nd Carbotrjferousbedrock'" floating in a an matrix" with Holocene-ageeuryhaline benthic foraminifera (Ammonia ve beccarii, Elphidium 'le crispum)'" and brackish water molluscs (Corbula an Fig,8 Interpretedseismic reflection profiles across the gibba, Cerithidea insulaemaris;7edated at 7.4+1.9 Dardanellesand B.osporus.Straits showing the erosionof the kyr BP in ageo'. 3S Paleozoicbedrock'" and its subsequent cover with inferred Suddeninundation of depressed,enclosed basins ]e Holocenedeposits as calibratedbv drillins in the axis of the Tssos6. yr Bosporusnear lstanbule Th; base-ofthe bedrockgorge are rare but real events.At the beginningof the -110 the drasticallydesiccated in deepensin the directionofthe BlackSea and reaches m in Pliocene Mediterranean the BosporusStrait. gigantic P Sea81filled via a Gibraltar waterfall. re Natufian stage of the late Palaeolithiccarry a Commonto oceanicwaterfalls is the fixed head of ic recordof a severe impoverishmentin diet leading the supplyingwater body.As erosiondeepens the re to an abandoned of sedentary villages on the upstreamcataract, the flow throughthe conduitis positive e banksof the EuphratesRiveroo. Pollen studiesin amplified through feedback. A n cares from Lake Huleh in the Levant indicatean conservative calculation based on turbulent d episodeof post YoungerDryas aridity lasting to at fluidss2with boundaryconditionss3 adapted to the n least 10 kyr BP''. Loess accumulatedin the Bosporus-Marmara-Dardanellesflume system yields e southernUkraine to 9.0 kyr BP7a.Cores from the an inflow of water of 50 to 100 km"/day. greater e Black Sea shelf east of Bulgaria have an This flux rate,several hundred times than K abundance of herbaceous pollen of steppe the world'slargest waterfall and a thousandtimes exceedingthe presentundercurrent, is sufficientto tl communities with Chenopodiaceqg and the 1 sagebrush Artemisain proliferation''right up to have raisedthe level of the Black Sea 30 to 60 cm eachday or to have toppedup the basin a year t the first appearance of marine molluscs. The in (Fig.9).On flat regionsof the shelf and in the river t synchronousdeposition of mud with marinefauna t directly on top of the low-moistureshelly gravel valleysthe sea might have advancedlandward at per overa documentedminimum elevation change 74 almost1 to 2 km day. The roar of the waterfall, ground i m impliesa rapid submergenceof the type which radiated by air and waves, would have ) wouldhave occurredif the MediterraneanSea had broadcastthe enormity of its cascade to any ) brokenits way intothe BlackSea via the Bosporus humanssettled or wanderingwithin 100 km of the I at 7.5 kyr BP. A massive input of saltwateris inlet. expressedin the abruptshift positiveshift with q magnitudeof 4 to 6 7ooin the oxygen isotopes"'

GEA-ECO- M AR|NA.,A1 997 Nationallnstitute of Maine Geologyand Geo-ecologyof Romania Prcc. lntern. Workshopon "Fluvial-Mainelnteractions" in Malnas,Romania, OcL1-7. 1996 W.B,F of the Black Sea shelfat 7.5

orifice. The Black Sea flood took place when farming villageshad already been establishedin Greece and southern Bulgariao",in lower oo,^lhe 17kyr BP feachesof the modernDanube Rivero" nearthe coast of the Sea of MarmarasTand in the Fertile Crescentss.At 7.5 kyr BP advancedfarming, with the possible use of the light plow and simple irrigationtechniques, blossomed in the Trans 14kvr BP Causasusits suddenintrojuction interpreted as an intrusionfrom the outside"". Ar^o-und7.4 kyr BP and within the span of 100 yearso"farming villages spread along the major rivervalleys of Germany,Austriq^ Czechoslovakia, o' Poland and the Low Countrieso'' Due to the remarkable homogeneity of these cultural deposits,archaeologists have considereda "wave. of-advance"model for the assumed population movementsn'.The immigrants had an obvious preference for the flood plains of rivers and lakes"' They settled throughoutmost of south- eastern Europe amo^qg^-a mysteriously sparse o" indigenouspcpulation'" Althoughthe migration model has been challengedand replacedby one one year latter of diffusion of skills rather than peopleo', the permanentflooding of the expansiveshelf of the Black Sea could have been and impetusto expel into Europe and the Near East communitiesof farmers which had adapted to the natural Fig.9 Reconstructedlake and sea levelsin ihe Aegean(A), resoufcesof the late NeoeuxineBlack Sea, i.e.,its Sea of Marmara (M), and Black Seas (BS), and their connections/isolatiorrsvia the Dardanelles(D) and Bosporus(B) arable loess soils, the seasonal irrigationof its Straits. An entrenchedsiream bed of the ancient Don River entrenchingrivers, and the fresh moist loam along Passes though the Kerch Strait (K$) Sea level in the Aegean the retreatingshoreline of its vast freshwaterlake tracksthe rise of ihe globaiocean''"'. The sedimentaryrecord of potentiallyexploitable for the springtimegrowing the BlackSea reveals two intervalsof isolation,during which much of its vast continentalshelf r,vasemerged land. A brief Neoeuxine of domesticatedfood crops. transgressiontakes place between 15 and 12 kyr BP, triggeredby Acknowledgements largeflux of melt.water,.gupplied frcrm the retreatingEarents and Scanclinavianice sheets"'and deliveredbv the Don and Dneiper The 1993 expeditionmaterialized though the 50'71 Riversand by an overflowfrom the CaspianSea3!' This tinre generousassistance of the officersand crew of the RA/ of high lake levelcoinodes with lt/elt-WaterPulse'l of ref (18). Aquanaut,the DatasonicsCorporation, Falmouth, MA, The floodingof marinewater into the Black Sea at 7.5 kyr BP is and R, Kosyanand E Kontarof the P.P Shirshov catastrophic,and is accompanledby the erosionof a gorgealong OceanologyInstitute M, Bruckner,R, Fairbanks,T. the inlet.ln the spanof a year,the EiackSee is toppedup the level of the Aegeanand is launchedon its wayfrom a freshwateriake to Guilderson,B. Hatau,W. Haxby,B. lfina, S. Klimley, an anoxicbrackish sea. W. Menke,L. Nevesskaya,and J Weisselprovided crucialtechnical and analyticalhelp, D. Harris,l. Possiblehuman response . Hodder,J. Mellaaft,A Moore,J. Oates,C. Renfrew,J. The geological evidence of an injection of Renfrewand A Sherratthave substantially contributed to understandrng possible saltwaterinto a depressedNeoeuxine lake via a our of archaeological implicationsof the Black Sea connectionswith the Bosporuscataract lends credenceto the ancient Mediterranean accounts of a bursting of the sea though this

REFERENCESAND NOTES anclby the u-Th calibrationof Bard et al. (1990) 1. All radiocarbondates are nonnalisedto a C-13 for ages> 10 kyrBP. valueof -25 per mil. The conventionalages have 2. Pliny.Book lV andVl (70AD). been reservoir corrected by 460 years based on 3. Strabo.Book l, Chapter3 (19AD) . measurementof rnolluscscollected in 1931.The 4. Sicily,D. o. . ages reportedas kyr BP have been convertedto 5. AtrtoRusov,N.1., Akad. Nauk St.Petersburg Bull,, -448 calendar years using the calibrationprogram of N.S.,3, 437 (1893). Stuiverand Braziunas(1993) for ages< 10 kyr BP 6. SoKoLov, N., Geol. Komitet St.Petersburg Trudy10 (1895). 122 GEO.ECO.MARINA,41997 Nationallnstltute of Maine Geologyand Geo-ecologyof Romania Proc. lntefn. Workshopan "Fluvial-Mainelnteractions" in Malnas,Romania, Oct-1-7, 1996

^\- W.B.F.Ryan et al.- An oftheBlack Sea she/faf 7.5

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GEO.ECO-MARINA,24597 125 NationatInstitute of Maine Geologyand Geo-ecologyof Romania Proc. lntem. Workshopon "Ftuvia!^Mainelnteracfions" in Malnas, Romania,Oct.1-7' 1996