2019 | 72/3 | 195–203 | 12 Figs. | www.geologia-croatica.hr Journal of the Croatian Geological Survey and the Croatian Geological Society

On the origin of both a recent and submerged tombolo on Prvić Island in the Kvarner area (Adriatic Sea, Croatia) Čedomir Benac1, Neven Bočić2 and Igor Ružić1

1 University of Rijeka, Faculty of Civil Engineering, Department of Hydrotechnics and Geotechnics, Radmile Matejčić 3, 51 000 Rijeka, Croatia; ([email protected]; [email protected]) 2 University of Zagreb, Faculty of Science, Department of Geography, Marulićev trg 19/II, 10 000 Zagreb, Croatia; ([email protected]) doi: 10.4154/gc.2019.14

Abstract Article history: This paper analyzes the origins of two tombolos (one recent and another fossil/submerged) on Manuscript received September 20, 2018 the southwestern coast of Prvić Island, which is located in the Kvarner area in the northeastern Revised manuscript accepted June 21, 2019 part of the Adriatic Sea. Available online October 31, 2019 A recent tombolo on Cape Pipa was formed by the erosion of Quaternary deposits and Palaeo- gene siliciclastic rocks. The submerged tombolo is much bigger, clearly visible on the sea bed toward the southwest. The conditions for forming a submerged and recent tombolo have oc- curred during a slow rise and then stagnation of sea level of the Adriatic Sea in the Holocene. The sea flooded the fossil tombolo probably in the final part of a period of rapid sea-level rise at the beginning of the Holocene when a large proportion of the Quaternary sediments were ero­ ded. Waves from the northwest (tramuntana) and southeast (jugo) refract and diffract around the tombolo. The nourishment of the beach body happens permanently on both sides of the cape. Accumulated sediments are protected by resistant rocky blocks of breccia on the peak of Cape

Pipa, acting as a natural tombolo. Due to the fact that wave directions are perpendicular to the beach coastline, they do not generate longshore currents that would erode sediment in beach Keywords: tombolo, marine erosion, coastal bodies around Cape Pipa. Therefore, the recent tombolo is probably stable in the present cli- geomorphology, sea-level rise, Holocene matic and oceanographic conditions in the Kvarner area.

1. INTRODUCTION the most common but there are also tombolo pairs and triplets Sea level is a global boundary with weathering and erosional pro­ (GOSSEAUME, 1973; MARRINER et al., 2008; CEYLAN, cesses prevailing above it, whereas the accumulation of sediments 2012). The preconditions for tombolo formation are: (i) high se­ occurs below it. In accordance with sea level changes during geo­ diment supply, (ii) a physical barrier against the swell and (iii) logical history, the intensity and location of erosion and accumu­ coastal processes conducive to the development of a sand bank, lation of sediments also changed (COWELL & THOM, 1997). i.e., bidirectional currents converging towards this physical ba­ Remnants of the effects of sea level changes have been found on rrier (DAVIES, 1980, according to MARRINER et al., 2008). the coastal and submarine relief in the Kvarner area in the north­ Geomorphological forms like tombolos are rare on the Croatian eastern part of the Adriatic Sea (BENAC & JURAČIĆ, 1998). coast of the Adriatic Sea and have not been studied in the scien­ This paper analyses the origins of two tombolos (one recent tific literature so far. This is the first known scientific research of and one submerged) and their conditional dependence on the Ho­ the morphogenesis of recent and submerged tombolos at nearby locene sea level rise. Both tombolos are located on the southwest­ locations. ern coast of Prvić Island in the Kvarner area, in the northeastern part of the Adriatic Sea (Fig. 1A). 2. STUDY AREA A tombolo is a depositional geomorphological landform Prvić Island is elongated in the NW-SE direction. The surface of 2 (sandbar, barrier or spit) that joins an island or a barrier with ei­ the island is 12.76 km , maximum length is 7.84 km, maximum ther the mainland or another island, resulting from longshore drift width is 2.6 km and the total length of the coast is 23.12 km or the migration of an offshore bar toward the coast (WARD, (DUPLANČIĆ-LEDER et al., 2004). The highest peak of the is­ 2004). land is 356 m above mean sea level (m.s.l), (Fig. 1C). Although they are a relatively rare geomorphological phe­ This island is mostly formed of carbonate rocks consisting of nomenon, they have been studied all over the world, eg: Finland Upper Cretaceous limestone and dolomitic limestone, Palaeogene (SCHWARTZ et al., 1989), Australia (SANDERSON & ELIOT, foraminiferal limestone, and partially of Palaeogene siliciclastic 1996), Japan (KAN et al., 1997) and the United Kingdom rocks i.e. marls and flysch (MAMUŽIĆ et al., 1969; BENAC et (FLINN, 1997; HANSOM, 2003). There are also a number of al., 2013). The bare karstic plateau in the central area of the island tombolos in the Mediterranean Sea, eg: Italy (GOSSEAUME, has an elevation of > 300 m above m.s.l. (Fig. 1B, C). 1973; AIELLO et al., 2007), France (VU et al., 2018, 2018b), Le­ The northeastern slopes between cape Stražica (NW) and banon (MARRINER et al., 2007, 2008) Turkey (CEYLAN, 2012) Cape Šilo (SE) are mostly very steep, with an average inclination and Egypt (TORAB, 2016). > 70°, and many vertical scarps are located above the shore. The Tombolos length varies from few tens of metres behind small carbonate rock mass is partially covered by active talus. Subma­ obstacles, up to more than ten kilometers. Single tombolos are rine slopes are also very steep, resulting in the 50 m isobath being­ Geologia Croatica and flysch, 3-UpperCretaceous limestone anddolomiticlimestone, 4-reverse fault,5-anticline axis, 6-proposed Island. fault;C-basic of relief characteristics Prvić Figure 1.A-Location geological map;B-Simplified map(according to MAMUŽIĆ etal., 1969):1-Neogenelimestone breccia, 2-Palaeogene foraminiferal limestone 196 Figure 2.The southwestern 1–Cape Island(photo: coast Pipa, Ž.Gržančić): ofPrvić Rock. 2–theNjivice Geologia Croatica 72/3 Geologia Croatica ­ ­ ­ ­ ­ 197 yearreturn period and for - . 2 Based on the data collected from the maps and fieldwork, In order to determine the influenceof waves on theforma geomorphologicalanalysis and synthesis were carried out, focu­ singon theand geological oceanographic conditions,forms and processes that created the recent features the on Cape relief of Pipa. 4. RESULTS Cape Pipa is formed the sea by erosion Palaeogene of siliciclastic younger partially with are covered which flysch) and (marls rocks sediments,cohesive Quaternary of probably This 3). (Fig. age phy fromphy an aircraft, and geological geomorphological mapping, and reconnaissance the underwater of part the exploration of area using scuba diving equipment. geomorphological mapping, For a customized methodology was used according to GAMS et al. et andal. This(2009). PAVLOPOULOS (1985) methodology is based on the morphogenetic determination observed of geomor processes,phological forms and conditions which are related to the morphogenesis The tombolos. geomorphological of mapping involved recognizing, locating andformsand processes drawingthe coastal of and morphogenetic slope type on the map the main with relief theof main purpose determining of their spatial rela tionships. thetion tombolos, numerical of modeling was used. Numerical simulation was performed using the Nearshore Simulating Waves numeric model, which is the third(SWAN) generation for model application in coastal areas, equilibrium based on Euler’s equa spectral A JONSWAP tion of (BOOIJ waveform 1999). et al., Numericalsimu­used. was 3.3 spectrum= parameterwave withγ was carried waves lation of in out the wider area the Grgurof Channel northwestern of waves for (generated tramuntana by wind) and southeastern directions The nu (generated jugo). by merical simulationthe was 50 done for windmean Relevant sea strengths level. numerical for simulation (southeastern m/s, northwestern direction: 27.4 direction: 22.2 m/s) were taken from the wind climate study of Vinodolthe Channelnearby ­ ­ ­ ­ In the prepara SE trending SE reverse fault - . The Njivice Rock is also built 2 State Geodetic Administration, Zagreb Geodetic Administration, State ,

E. Its largest width is about 12 m, its height is 4 m and m 4 is height its m, 12 about is widthlargest Its E. - . According to information from the visual interpretations Cape Pipa is located in the central part the southwestern of Large blocks of limestone anditselfbrecciaof formPipa CapeLarge blocks Approximately 340metres fromSSE Cape Pipalies theNji­ The second method was field investigation. The mainpur 1 25,000, 25,000, Croatian base mapand (1:5000) Digital orthophoto ce Rock (Fig. 2). It is a small rock with a length of about 50 m m 50 about of length a with rock small a is It 2). (Fig. Rock ­ce https://geoportal.dgu.hr/Geoportal mouth in Crikvenica. Dubračina Zagreb at the area for climate Wind Service and Hydrological (2006): Meteorological Croatian Cape Pipa (photo: Č. Benac): A) carbonate rock mass, B) Quaternary sediments, C) Palaeogene flysch, D) gravely beach, E) collapsed blocks of limestone of collapsed blocks E) beach, gravely D) flysch, B) Quaternary C) mass, sediments, Palaeogene rock carbonate Benac):Č. A) (photo: Pipa 3. Cape Figure F) tombolo. - an obstacle, breccia 2 toryphase, variousmaps were usedto provide information on the geomorphological phenomena the area: of topographic map 1: map Three different methodswere used in this study. 3. METHODS coast Prvić of Island where the coastal relief and geologic fabric other coastal to parts are very of relation this different island. in Steepverticalor upper parts the slopes are of formed carbo­ of known. well not and complex is tectonicfabric the and rocks,nate the inrocks siliciclastic carbonate betweencontacttheseand The partlower the isa NW slope of mostly <100 m from the coastline.mostly <100 The slopes are more gently the drykarsticvalley, A island. the western parttheof inclinedin formgeomorphological dominant exogenous a dragais Smokova (Fig. 1C). (MAMUŽIĆ et al., 1969), (Fig. 1B). 1B). (Fig. (MAMUŽIĆ 1969), et al., sandy andgravely beaches formed have both the along of sides The sea bed is at a shallow depth 2). cape (Fig. around this cape. vi strikingW its surface is approximately 500 m Benacet al.: On the origin of both a recentand submerged tombolo on Prvić Islandin the Kvarner area (Adriatic Sea, Croatia) 1 of carbonateof breccia, Palaeogene The age. of probably investi gated part of Prvić Island is exposed to waves from both the southeast and the northwest compared which low are relatively into waves the open sea due to their below). small (see fetch of of these maps, we found this specificlocation and recognized ­active and submerged at nearby tombolos locations. Further, we used orthophoto map as a base theinvestigation. for field pose theof work field was to collect data on landforms and their relationship with the structure geological the terrain of in the obtainedCapePipa.Dataaerialwerewider area by of photogra Geologia Croatica Figure 5.Outcrops layers of subvertical (photo: (precise Č.Benac) location isvisible inFig. 4). wave to (Fig. obstacle motion an 3). provides and breccia Behind body. sediment is sidesof this both on formed cliff coastal The mass. rock carbonate the from originate that blocks and fragments angular contain layers Some body. sediment this in prevails sand silty observations, field liminary pre to slope. According coastal the to opposite gentle inclination have a planes bedding clearly is visible and body sediment nary visible on its southeastern side. The stratification of the Quater deposit is 10 to 12 m, and outcrops of flyscharebedrock partially Quaternary of height 50 this The m. of around length abase with triangle of irregular an aform has body sediment Quaternary 198 of submerged tombolo, 3-location ofFig. 5. imageofCapeFigure Pipa andthesubmerged tombolo 4.Ortho-photo spotsare (dark meadows ofPosidonia oceanica) 1-submerged beaches, 2-supposedarea Cape vertex itself is formed on collapsed blocks of talus talus of blocks collapsed on formed is itself vertex Cape ­ ­ stacle. The Njivice Rock is built of carbonate breccia, probably breccia, carbonate of built is Rock Njivice The stacle. ob another behind formed was tombolo form submerged This side (Fig. 4). southeastern the on noticeable less side and western clearly visible the on are of coast ancient long. Concave traces a palaeo it as So, consider we can sediments. beach of built submerged are form of this edges The of Pipa. southwest Cape bed sea clearly is visiblebolo the on form visible. partially are pebble grains 2 between diameter average an of with gravel tombolo. Grains a as characterized be can (WARD, 2004), classification logical geomorpho to according Pipa, Cape coast. the Vertex with Cape connect that sediments of beach accumulation the is obstacle this and 6 cm prevail in the beach body. Coarse sand and subangular subangular and sand body. beach the Coarse in prevail 6cm and - coastline, approximately 300 m m 300 approximately coastline, A much bigger triangular tom A much bigger triangular Geologia Croatica 72/3 ­ ­ ­ Geologia Croatica - - - ­ 199 diving equip - rudite). - arenite and calc - cially built walls (Fig. 4). Exploration usingcially built scuba 4). walls (Fig. ment has revealed that they are outcrops of vertical layers of rocks of verticallayers of outcropsare they that revealed has ment first At glance,5). (Fig. seemthey carbonateto be members a of (calc rockflysch mass ­ - ­ Unusual dark parallel lines are clearly visible on the ortho Geological cross-sections of the submerged and recent tombolos. 1-recent collapsed blocks of breccia, 2-beach sediments (coarse sand and gravel), 3-Qua sand and gravel), (coarse sediments 2-beach blocks of breccia, collapsed 1-recent tombolos. and recent cross-sections 7. Geological of the submerged Figure Palaeogene flysch. in layers resistant 6-more flysch, 5-Palaeogene breccia, (?) limestone and silty sand), 4-Palaeogene ternary fragments blocks, (carbonate sediments A geomorphological map of Cape Pipa and the surrounding area. 1-Quaternary sediments, 2-Palaeogene flysch mostly covered by slope deposits, 3-carby slope deposits, covered mostly flysch 1-Quaternary area. and the surrounding 2-Palaeogene Pipa sediments, map of Cape 6. A geomorphological Figure bonate rock mass (Upper Cretaceous limestone and dolomitic limestone and Palaeogene foraminiferal limestone), 4-main ridges, 5-reverse fault, 6-fault escarp 5-reverse 4-main ridges, limestone), foraminiferal and Palaeogene and dolomitic limestone limestone mass (Upper Cretaceous rock bonate 12-recent cliff, 11-recent sand and gravel), 10-beaches (coarse mass, rock in carbonate shoreline fan, 9-recent prolluvium 8-assumed submerged 7-gully, ment, 16-position of 15-direction genesis, tombolo of major waves, the time of submerged at 14-assumed position of the shoreline tombolo, 13-submerged tombolo, 7). cross-sections (see Fig. geological of Palaeogene This age. of submerged lies tombolo an at approxi metresmate the depth recent 10 below of sea level. Benacet al.: On the origin of both a recentand submerged tombolo on Prvić Islandin the Kvarner area (Adriatic Sea, Croatia) photo image where these submerged outcrops look like artifi Geologia Croatica 7). In addition to the above mention obstacles of different geo different of obstacles mention above the to addition In 7). tombolos (Fig. development the of investigated enabled the that (Fig. now 6). submerged are which sedi­ that hypothesize fans, can prolluvium some we formed gullies the from eroded ment maps, topographic on isobaths and of contours the shape the to According present. also is erosion bonate but rocks are on karstified, the steep slopesintensive line car These gullies. deep few a with rocks carbonate Cretaceous slopes. steep with elevations higher on beach, the from distant more are rocks carbonate Cretaceous and carbonate) rocks are present only at lower elevations whereas (siliciclastic Palaeogene rocks. carbonate Cretaceous in formed was coast away, the further little A limestone. and rocks clastic silici­ Palaeogene in formed tombolos was the around area the in 7. 6. and coastline Figures recent in The shown are area rounding 200 Figure 9.Significant wave heights from southwest wave directions for a50- year (inmetres) period return at Cape NjiviceRock. Pipa andthe Figure 8.Significant wave height (inmetres) andthemain wave of50- direction year intheGrgur period return Channel. Geological cross Geological of formed predominantly is Island Prvić the of inland The Geomorphological and geological conditions in the sur the in geological conditions and Geomorphological - sections indicate several favourable factors favourable factors several indicate sections ar ­ar ­ ­ ­ the southeast (H southeast the from waves coming wind model results, to According tribution. dis wind al., et 1999),model (BOOIJ auniform assumes which SWAN the using simulations wave wavecant height and direction shows8 signifi Figure Channel. Grgur the waves in highest the sediments. of erosion these marine against tion fly sch in rock mass (Figs. layers 5, 7) was also likely resistant to have more helped the of protec position vertical The portions. pro small but probably in fans, prolluvium submerged supposed the tombolo was submerged for the of material asource sible that from Cape Pipa and probably Palaeogene body flysch(Fig. sediment 6). Itis pos Quaternary the likely most are These portant. im is material accumulation of beach source the origins, logical tombolo and the adjacent coast of Prvić Island are protected from shoaling significant from and Njivice, of Rock the on break rections protected are Island Prvić di of Waves southeastern from direction. southeast the waves from coast adjacent the and tombolo the northwest (H northwest the The southeastern and northwestern wind directions generate generate directions wind northwestern and southeastern The S S 50 50 =2.40 m) are higher than ones coming from from coming ones than higher are m)=2.40 =2.00 m) in the Grgur Channel. The recent recent The Channel. Grgur the in m) =2.00 Geologia Croatica 72/3 ­ ­ ­ ­ ­ ­ ­ ­ Geologia Croatica ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ 201 grainedsedi - rosion of an ancient of largerosion sediment body has been E

Behind barriers, complicated a mechanism curwaves, of Accumulatedsediments are then protected resistanta by The recent is in tombolo a state equilibrium of in the present nent. Sheet wash and rilling types erosion caused of surface by water are and visible additional consequently, feeding the beach of sediment body is active on both the 6). cape of sides 3, (Figs. erosion of theerosion Quaternary of sediment body on Cape Pipa is perma rents, sediment transport, and morphology occurs. Cape At Pipa, over transmitted reflected and dissipated beenergyby will wave topping, waves also diffract around the tombolo 10). As (Fig. a result,they generate currents longshore opposite directions of and support erosion or accumulation sediment of in beach bodies around Cape Pipa. naturalcreatingtoma Pipa, Cape of peakthe on breccia of block directions as wave onthe windward are side 11), per (Fig. bolo pendicular to the beach coastline, and sediment trans longshore setup inport the lee Wave is on the is minimal tombolo 10). (Fig. diffraction, of combination partly transmission a and refraction. directionThe wave and energy behind Cape Pipa seem favoura­ sediment for ble accumulation and retention due to reduced ero causedsion currents. longshore by climatic and oceanographic conditions in the Kvarner area (PEN Stagnation occurred sea level of ZAR 2001). in et al., the last 7000 years,after the rapidLate Pleistocene–Holocene rise in the Adri BENJAMINetSURIĆ,2009; 2004; (LAMBECK Sea atical., et 2017). al., intensive during this the period. described Namely, Quaternary sediment body has features Therefore, soil. me a cohesive of chanical weathering and erosion are intensive and permanent. This sediment body resistance has lower to destructive at wave tackin to the relation carbonate rocks. The coarse ­ ­ ­ ­ ­ ­ ­ The effects of wave diffraction and shoaling are clearly mani­ The question arises as recent to why and submerged tombo Exogenous slope geomorphological slope Exogenous processes are very in Significant wave heights (in metres) from the main wave direction for 50 – year return period at Cape Pipa. Cape return periodat year for 50 – direction wave the main from (in metres) heights wave 10. Significant Figure 5. DISCUSSION Croatianthe along rareare tombolo a likeformsGeomorphologic coast the Adriatic of Sea, due to the resis prevalence relative of occurs at the submerged tombolo (Figs. 6, 9, 10). Wind waves Wind waves occurs 10). at the submerged 6, 9, (Figs. tombolo from northwestern directions higherhave significant wave theheights same of return period than from waves southeastern directions on Cape 10). Pipa (Fig. fested around Cape Pipa. A majority the incoming of wave’s ­energy dissipates on Cape Pipa and the surrounding seabed. Be hind this cape, there is a shadow zone with low wave energy which provides stability. tombolo tant carbonate rocks in which processes of mechanical marine The 2013). JURAČIĆ,(PIKELJexpressed & well less are erosion same situation occurs in the Kvarner area, where a very pro slow cess prevails, bioerosion of while marine erosion is more strongly Quaternary and rocks siliciclastic resistant less in the expressed deposits (JURAČIĆ et al., 2009). The origin ofposits at Cape Pipa the had been not investigated in described detail. According de can these be considered deposits 3) (Fig. to MARJANAC (2012) as the remains the glacial of terrace. Benacet al.: On the origin of both a recentand submerged tombolo on Prvić Islandin the Kvarner area (Adriatic Sea, Croatia) los were formedlos in nearby locations? The cause may be three a geomorphologicalspecific factors:geological fabric(1) on the oceanographic favourable (2) Island, Prvić of side southwestern conditions in the Grgur change the Channel dur sea level and (3) ing the Holocene. tense on the southwestern coast Prvić of Island, especially where active talus formation and rock sliding are visible (Fig. The2). Geologia Croatica mately 10 m, and according to Holocene sea to 10mately according and m, on the southeastern side (Fig. 4). southeastern the on so less side, and western the on clearly visible: are better beaches ancient of traces However, the formed. was cliff coastal the and eroded was sediments of Quaternary the proportion agreat and of Holocene the beginning of atthe level sea rapid phase rise last (Fig. surface 2). The sea floodedthe tombolo probably the during sea the above visible today is rock the of top The Island. Prvić and Rock Njivice the between bodies sediment beach forming conditions for created has This area. in the shallow and flattened waves to obstacle an provide blocks rocky large tombolo.These of the formation the role in played important an breccia bonate al., et 2017).al., BENJAMIN 2004; car relatively The resistant et Holocene (LAMBECK the in level sea global rise the during deposits. these from al., et 2009) probably originated Šilo (PIKELJ Cape near Chanel of Grgur the part of southeastern the bottom atthe found ments Figure 11.The recent tombolo protected by blocks. rocky 202 lines (seeFigs. 6,7). Figure 12.The positionoftherecent andsubmerged tombolos relative to Holocene sealevel (according rise to LAMBECK etal., 2004).AandBare cross-sections 3

According to data provided by Mohorovičić Andrija ofGeophysics, Geophysical Institute, Department Faculty ofScience, University ofZagreb Based on the depth of the submerged tombolo of of approxi submerged the depth the on Based tombolo occurred asubmerged for forming conditions The

- level rise, it can be be itlevel can rise, ­ ­ sea level rise could be 62 be could level ±14sea of rise 21 end by the the cm predicted analyses, new al., et to 2009). (TSIMPLIS Sea According Adriatic the in measurements of instrumental beginning the from of 2.0 range ± 0.9 the in rise (Figs.the outcrop behind 8, the sediment 9, driving 10). Sea level higher make and (tramuntana), directions frequent northwestern from more winds the waves than are (jugo) directions southeastern from winds the of tombolo, the because for formation responsible have may been conditions ago (Fig. 12).years oceanographic Local 7,000 approximately formed fossil tombolo was the that assumed trend, which will have a negative impact on tomboloon Ac stability. have a negative impact will which trend, of sustained anew start probably the are tides high extremely recorded These future. the in submerged and eroded be therefore it could and form unstable conditions) given an bolo (under these is +122 cm above MSL from 1 MSL from 29 MSL from graph graph in city: Bakar + 117 cm above MSL from 1 mareo the in recorded tides high extremely include levelsea rise accelerated PASARIĆ,of2013). & (ORLIĆ indications Possible th th October 2018 st November 2012 and + 127 cm above above cm 127 + and 2012 November 3.4 ± 1.1 mm/yr has been recorded recorded - 3.4 been ± 1.1 has mm/yr 3 . 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BOOIJ, N., RIS, R.C. & HOLTHUIJSEN, L.H. (1999): A third-generation wave model A L.H. (1999): BOOIJ, N., RIS, R.C. & HOLTHUIJSEN, CEYLAN, M.A. (2012): General Overview of the on Coastlines. Tombolos Turkey’s In: evolution.– of coastal Morphodynamics B.G. (1997): THOM, & P.J. COWELL, in J.L. Coastal (1980): Development. Geographical Variation Longman, DAVIES, Lon­ REFERENCES AIELLO, G., BARRA, D., DE DONADIO, PIPPO, T., C. & PETROSINO, C. (2007): ACKNOWLEDGMENT This work has been supported inunder the part projects Uniri by the University of Rijeka ­ chang level sea the of indicators Geomorphological (1998): M. JURAČIĆ, & Č. BENAC, Fluviokarst (2013): K. PIKELJ, & I. RUŽIĆ, D., MATIČEC, M., JURAČIĆ, Č., BENAC, M., INGLIS, VACCHI, A., FURLANI, S., A., FONTANA, BENJAMIN, J., ROVERE, Within this research, the existence and two (recent fossil/sub of 6. CONCLUSIONS merged) tombolos in neighbouring locations on Prvić Island in the northern Adriatic Sea has been reported. the oceanographic change during sea level (2) conditions and the (3) Holocene. clastites, and submerged subrecent potential prolluvial fans, all in an area dominated karstifiedby carbonates, enabled theexis tence obstacles of as a prerequisite the for formation tombolos. of In addition, geological specificities have enabled the source of material to feed both and (recent submerged) Windy tombolos. fromwaves the northwest (tramuntana) and southeast (jugo) to gether with generated currents longshore are responsible for coastal erosion and accumulation sediment of in the beach bo cordingto the expected sea Benacet al.: On the origin of both a recentand submerged tombolo on Prvić Islandin the Kvarner area (Adriatic Sea, Croatia) at Cape Pipa. two tombolos at differentheights at different times.Regarding is supposed m it the depth that approx. 10 of the tombolo fossil beencould have submerged approximately years ago. 7,000 6805 and GEOSEKVA (HRZZ IP and6805 GEOSEKVA extremely high ( water levels coastal processesmight become more intensive. This could con tribute to the acceleration of marine erosion, cliff retreat andex changespressive beach of bodies including tombolos. is a unique phenomenon in the Adriatic Sea, and in possibly the Mediterranean Sea.