Implications for Late Holocene Sea-Level Fluctuations

Sedimentary Geology 294 (2013) 294–302

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Sedimentary Geology

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First record of beachrock on Black Sea coast of Turkey: Implications for Late Holocene sea-level ﬂuctuations

Ahmet Evren Erginal a,⁎, Yunus Levent Ekinci b, Alper Demirci b, Mustafa Bozcu c, Muhammed Zeynel Ozturk d, Mustafa Avcioglu c, Erdal Oztura e a Ardahan University, Department of Geography, TR-75000 Ardahan, Turkey b Çanakkale Onsekiz Mart University, Department of Geophysical Engineering, TR-17020 Çanakkale, Turkey c Çanakkale Onsekiz Mart University, Department of Geology Engineering, TR-17020 Çanakkale, Turkey d Çanakkale Onsekiz Mart University, Department of Geography, TR-17020 Çanakkale, Turkey e Çanakkale Onsekiz Mart University, Department of Geography Education, TR-17020 Çanakkale, Turkey article info abstract

Article history: We present new data on the diagenetic characteristics, subsurface nature and radiocarbon ages of beachrock Received 9 May 2013 from the Thracian Black Sea coast of Turkey, indicative of sea-level changes and climatic conditions favoring Received in revised form 14 June 2013 lithiﬁcation of beach sands between 5.4 ka and 3.5 ka cal BP. Micrite coatings and succeeding meniscus ce- Accepted 15 June 2013 ments typify diagenetic history and suggest a two-stage cementation over this timeframe. The early cements Available online 24 June 2013 are typical of upper intertidal zone when the sea-level was likely similar to that of today. The ensuing Editor: Dr. J. Knight intergranular bridges refer to an approximate 2 m decline in sea-level, favoring downward percolation of meteoric waters related to subaerial exposure, marked by a reduction in Mg concentration and dissolution Keywords: pits on early cement coatings. Formation of beachrock during this bimillennial period could be associated Beachrock with relatively drier conditions promoting the precipitation of connective cements. Sequential cementation © 2013 Elsevier B.V. All rights reserved. Sea-level changes Thrace Black Sea

1. Introduction as a key indicator for sea-level changes due to differing viewpoints (Kelletat, 2006; Knight, 2007). As a kind of cemented beach deposit frequently found in the form In contrast to authors who have focused on geomorphological of blocks or slabs, beachrock offers a record of the morphodynamic, data (Kelletat, 2006), many researchers have recently gained benefit climatic and oceanographic changes that have occurred in coastal from studying cementation characteristics (Kneale and Viles, 2000; areas. Amalgamation of sediments as well as fossil shells and micro- Hillgaèrtner et al., 2001; Calvet et al., 2003; Rey et al., 2004; Vieira fossils entombed within cement or intergranular spaces provide a re- and De Ros, 2006) and stable isotope data (Holail and Rashed, 1992; cord of the diagenetic history of the beachrock. Since the very earliest Calvet et al., 2003; Friedman, 2005; Vieira and De Ros, 2006). One of studies, attempts have been made to pinpoint the origin, age, distri- the main problems regarding the solidity of intertidal beachrock in bution and significance of beachrock on various coastal outcrops real terms is lack of information on the continuation of beachrock around the world (see Vousdoukas et al. (2007) and references there- backshore under beach materials, since samples are mostly taken in). Since abiotic cement, i.e., aragonite and high Mg-calcite, is precip- from slabs exposed at the coast. Along the 8333 km-long coastline itated as a direct result of the evaporation of sea-water, predominantly of Turkey, beachrocks display a wide distribution, from the eastern as a connective carbonate, beachrock has been generally attributed to end of the Mediterranean to the Gulf of Saros, comprising the northern intertidal cementation and regarded as giving explicit indications of limit of the Aegean Sea (Avşarcan, 1997; Desruelles et al., 2009). sea-level changes. Nevertheless, contribution of different specific pro- In this study, results obtained from the first recorded beachrock on cesses regarding to precipitation of binding carbonates have been sug- the Thracian Black Sea coast of Turkey are discussed (Fig. 1a, b). We gested (Vieira and De Ros, 2006 and references therein). Until considered that the formation of beachrock on the coast of the Black recently, however, there was debate on the credibility of beachrock Sea is substantive in that this anoxic sea is presently characterized by low (17–20‰) surface salinity and a nominal amount of evaporation compared to the much greater amount of freshwater input by precipita- ş ⁎ Corresponding author. Tel.: +90 478 2114132; fax: +90 478 2113275. tion and rivers (Be iktepe et al., 1994; Mertens et al., 2012). Based on E-mail address: [email protected] (A.E. Erginal). diagenetic characteristics in conjunction with radiocarbon ages and

Fig. 1. (a–b) Location maps of study area; (c) geology map of the study area and its environs; (d) ERT lines taken perpendicular to the coastline. geophysical imaging data, new findings in respect of Late Holocene the northern coast is the mouth of the Kazandere River which flows sea-level fluctuations on the Turkish Black Sea coast are presented. into the sea from between Kıyıköy port and a coastal spit (Fig. 1c). On the backshore, a low ridge made up of a 5-m thick coastal dune stands between the river mouth and the present sandy beach. Meteoro- 2. Study area logical data (1975–2006) from Kumköy meteorology station 85 km to the southeast indicate that the area receives a yearly precipitation of On the eastern coast of Kıyıköy, Kırklareli, NW Turkey, the studied 831.4 mm. The average annual air and sea-water temperatures were deposits constitute the first record of beachrock from the northwestern recorded as 13.8 °C and 14.3 °C, respectively. During the hot period be- Thracian Black Sea coast of Turkey (Fig. 1a, b). Comprising the European tween May and September, evaporation values from sea water reach a part of the country, Thrace is bounded by the Sea of Marmara to the totalof600mm,whichislowerthantheMediterranean(approximate- south and Black Sea to the north and has a coastline of about 786 km. ly 2000 mm). Climatically, a humid-temperate Black Sea climate domi- The Black Sea coast of Thrace starts from the mouth of the River Rezve nates (Türkeş,1996). Tidal range is nominal with an average of 10 cm (Rezovo) at the Bulgarian border and extends in a northwest–southeast (Goudie, 2001). direction down to the strait of Istanbul (Bosphorus) (Fig. 1b). The eastern part of Thrace comprises the Çatalca Peninsula and is characterized by a nearly straight coastline. However, in the northwestern section, 3. Methods the Thracian coast is rather indented as the coastal area forms a seaward (northeast) prolongation of the Strandja Mountains, a massif consisting 3.1. Analyses of beachrock materials of basement rocks such as gneiss and amphibolite, and cover deposits formed of schist, limestone, sandstone and igneous rocks (Pamir Five samples of beachrock were collected for analysis and radio- and Baykal, 1947). carbon dating. Petrographic analysis was carried out based on thin The geology of the backshore at the southern end of the cemented section interpretations. Energy Dispersive Spectroscopy (EDX-Bruker beach in this study is composed of Middle to Late Eocene fossiliferous AXS XFlash) analysis of the beachrock was performed to shed light on limestones with sandstone and claystone intercalations (Fig. 1c). On elemental composition of connective cements. Using Scanning Electron 296 A.E. Erginal et al. / Sedimentary Geology 294 (2013) 294–302

Microscopy (SEM-Zeiss EVO 50 EP), the same sub-samples were used depth of −2 m extends up to 20 m offshore. Following the assump- for determination of sequential cement fabrics on and around the bond- tion that beachrock is suggestive of intertidal cementation, and its po- ed grains. Analysis was carried out at Izmir Institute of Technology, tential for highlighting sea-level changes, knowledge of the total Turkey. To determine foraminiferal contents, samples were treated thickness of beds, including buried slabs, is of importance. For this with 10% H2O2 for one day and wet sieved through a 63 μmsieve.The purpose, ERT images (Fig. 3) were obtained from the beach. Taken residue was then dried in air. In the sediment fraction above the 63 μm perpendicular to the coastline (Fig. 1d), resistivity tomograms pro- sieve, benthic foraminiferal fauna was examined under a binocular mi- duced by the 2D tomographic inversion process displayed a depth croscope. Five bulk samples of beachrock were dated by conventional range of about 2.7 m for ERT-1 and ERT-2 and about 4 m for ERT-3 and AMS radiocarbon methods at BETA, Miami, USA. and ERT-4 (Fig. 3). The resistivity values in the survey area vary between about 1 and 550 ohm.m. Thus, the tomographic images clearly 3.2. Geophysical survey show a sharp resistivity contrast between the high-resistivity beachrocks and high-conductivity beach material. The abnormal decrease in the A geoelectrical survey using electrical resistivity tomography resistivity values of the beach material might have resulted from an in- (ERT) technique was conducted along 4 coastline-perpendicular lines crease in salinity due to seawater intrusion. These images also show (Fig. 1d), 10 m apart from each other, in order to depict the internal that the buried slabs of beachrock are about 1 m thick, showing a structure and contact relationship of the beachrocks and also to monitor sharp termination at this depth. Additionally, a high-resistivity zone is their landward extent. The ERT measurements were carried out with a observed at the end of ERT-3 and ERT-4 lines. This high-resistivity zone GF ARES multi-electrode resistivity-meter system using dipole–dipole is thought to be associated with fossil dunes located on the backshore. electrode configuration. Apparent resistivity data were collected from According to ERT images, the buried beds are followed up to about the beach using 22 electrodes spaced at 1 m for ERT-1 and ERT-2, and 23 m at the backshore. At the beginning of the ERT lines, traces of the 1.5 m for ERT-3 and ERT-4. The total number of data levels was 11 beachrocks are not observed probably due to erosion. for each survey line. Quality enhancement of the measured data was Geophysical imaging data provided two important insights into carried out by performing 6 stacks (repeated measurements) in each the beach environment cemented to form this beachrock; i.e., (1) a data point, and average apparent resistivity values were assigned to maximum thickness of beds of 1.75 m, exceeding the inconsiderable related datum points. Measured apparent resistivity data were then tidal amplitude of the Black Sea (Goudie, 2001), when exposed and processed by an automatic 2D tomographic inversion scheme based buried slabs are taken into consideration, and (2) the total width of on smoothness-constrained least-squares algorithm (Loke and Barker, the cemented zone (about 40 m), including the submerged parts off- 1996), for a more accurate interpretation. There were no topographic shore and buried onshore parts. differences along the survey lines of ERT-1 and ERT-2. However, due to the significant topographic relief at the end of the lines of ERT-3 4.2. Composition and diagenetic stages and ERT-4, elevations of each electrode location were measured and the topographical data were incorporated into the 2D inversion proce- A coastal conglomerate predominated by small pebbles and coarse dure in order to carry out more detailed and reliable processing. The cal- sands in grain size distribution, the studied beachrock contained culated apparent resistivity data were obtained using the finite-element calcium carbonate of between 34 and 45%. The amalgamated compo- method with four nodes per unit electrode spacing during the inversion nents were poorly sorted, containing pebbles (48%) and sands (52%), process. For final interpretation, geoelectrical resistivity tomograms the latter of which were composed mainly of very coarse sand (81%) were chosen at the iteration after which RMS error did not change and finer grains. Pebbles smaller in size than 3 mm were predomi- significantly. nant, implying that the cemented beds arose from a higher-energy shingle beach. Broken shell fragments dominated by D. trunculus, 4. Results and discussion Venus gallina and Patella sp. were observed to be tightly embedded solely on the case-hardened surface of beds. Petrographic analyses 4.1. Morphology and subsurface nature of beachrock from thin sectioned images of the finer parts indicate that the beachrock was composed of quartz arenite to sublitharenite based on Folk's (1974) Similar to the orientation of the present beach, the beachrock beds classification, containing various rock fragments derived from granite, extend in a northwest–southeast direction to the south of a coastal micaschist and quartzite as well as some algae (Fig. 2c–g). This composi- spit stretching toward Kıyıköy Port (Fig. 2a). Visible thickness of the tion is indicative of derivation from the Strandja massif in the northwest exposed beds ranges between 10 cm and 75 cm. The length and which holds the basement rocks of Thrace. Thin section images showed width of the beds are 250 m and 20 m, respectively. Dipping toward that grains are, to a large extent, composed of weakly-bonded sands the sea at angles between 5° and 10°, the beds are composed of of sub-rounded polycrystalline quartz typical of short-distance drift by hard-bonded coarse sands with sizes ranging between 0.5 mm and longshore coastal currents. 1 mm, very fine gravels smaller than 3 cm and bivalvia fragments The benthic foraminiferal fauna within the samples consisted of (Fig. 2b). Having a maximum visible thickness of 75 cm, many of number of species (Table 1) at varied amounts, the majority of which the beds emerge from the 20-m wide sandy beach and are backed were recently reported from a cemented coquina to the east of the by iron-oxidized dune deposits with abundant fossil shells of Donax study area (Erginal et al., 2012). Predominance of Rosalina vilardeboana trunculus. Throughout the cemented zone, the surface of the beachrock and Ammonia tepida within the samples indicates shallow water in re- and fractures enlarged by sea waves is substantially colonized by spect of the depositional environment. Enteromorpha sp. At the southeast end of the beach, the beachrock SEM analyses in conjunction with EDX undertaken to highlight the beds terminate in front of cliffs cut in Middle–Upper Eocene lime- origin and diagenetic history of the beachrock indicated the presence stones mostly composed of overlapping broken blocks due to violent of different cement fabrics (Fig. 4). These cements are composed, in sea-wave erosion. These blocks, up to 3 m in size, appear to have dis- order of priority, of micrite coatings and meniscus bridges formed sected along fracture sets of orthogonal and polygonal joints. Given exceptionally of radial aggregates and scalenohedral calcite rims. In that the studied coast is tectonically dormant, these fractures may decreasing order of abundance, cements measured by EDX (Table 2) be supposed to be of syndepositional origin, showing a lack of any contain, on average, O (49.64%), Ca (25.76%), C (12.98%), Si (5.15%), tectonically-induced displacement along the studied coast. Mg (1.27%), Al (0.98%), Fe (0.31%) and Na (0.29%). Albeit at low Even though the visible thickness of the emerged beachrock is concentrations, the presence of Al, Si and Fe in cements is likely related about 75 cm, the seaward margin of the submerged beachrock at a to involvement from the mineral fragments. These cements are composed A.E. Erginal et al. / Sedimentary Geology 294 (2013) 294–302 297

Fig. 2. (a) View of studied beachrock. Stars indicate sampling locations. (b) Close up of cemented sands and bioclast on upper, case-hardened surface of beachrock. (c–g) Thin section images of beachrock with sample codes; (c) polycrystalline quartz grains within weakly bonded beachrock with very high void ratio; (d) typical example of meniscus cement; (e) a quartzite fragment and weak meniscus bridges between the grains; (f) Polycrystalline quartz and meniscus cement following thin micritic coatings; (g) algae fragments.

exclusivelyoflow-Mgcalcite(0.52–1.7 mol% MgCO3), suggesting the in- et al., 2003; Rey et al., 2004). Rey et al. (2004) suggest that the mixing ﬂuence of freshwaters. Such fabrics are known to dominate not only in of marine and meteoric waters results in an increase in the concentration beachrocks from temperate coasts (Kneale and Viles, 2000)butarealso of dissolved carbonates, in that increased pH makes carbonate precipita- ascribed to freshwater diagenesis (Binkley et al., 1980). In this respect, it tion easier. The existence of carbonates formed by Eocene limestones is essential to establish whether this cement was either low-Mg calcite, might have been a landward source of cement. originally transported by downward-percolating carbonate-rich ground- The width of the connecting bridges may reach 200 μm. Closer ex- waters from Eocene limestones at the backshore, or is associated with amination of meniscus cements displayed the presence of aggregates transformation from aragonite or high-Mg calcite to low-Mg calcite of calcite (1.45 mol% MgCO3) subjected to dissolution under subaerial with the lapse of time (Siesser, 1974; Guerra et al., 2005). EDX analysis exposure conditions (Fig. 4g). Albeit rare, the third form of cement of the bedrock samples displayed a lack of Mg in their elemental concen- binding siliciclastic grains is composed of low-Mg calcite rims consisting tration, being composed of C (18.6%), O (60%), Ca (20.3%), and Si (0.6%) of clumps of reciprocal-oriented calcites having scalenohedral termina- (Table 2). Thus, neomorphic replacement from early cement to low-Mg tions (Fig. 4h, i). Contributing to building intergranular bridges, these calcite is not likely. rims are thinner than 50 μmandfollow5-μm thick micrite envelopes.

Containing 1.29 mol% MgCO3, micritic envelopes with a maximum thickness of 20 μm were very common in all the analyzed samples, 4.3. Implications for Late Holocene sea-level changes with a high void ratio (Fig. 4a, b). These cements were attached to siliciclastic grains (Fig. 4c, d), lithoclasts and, to a lesser extent, shell Radiocarbon dating of the bulk carbonates obtained from the five fragments. Constituting different orientations on their substrates, samples was undertaken to date the formation of the beachrock sam- micrites are composed of equal-sized crystals with an average length ples collected from three different sections; namely, the middle, of 4 μm. Closer views of these coatings display the presence of micritic backmost and leading edges. Results presented in Table 3 yielded aggregates of low-Mg calcite (Fig. 4e). This fabric may be attributed to ages 5460 cal BP and 3500 cal BP for the oldest and the youngest precipitation in the backshore by meteoric groundwater in the upper beds, respectively. Extracted from a depth of 15 cm, the oldest sample intertidal zone (Guerra et al., 2005). (KK1) represents the middle section of the cemented beds, dated to These thin coatings are followed by bridging cements, i.e., meniscus 5460–5260 cal BP. Samples from the leading edges and backmost fills connecting grains and lithic fragments (Fig. 4f). Lower than the for- parts of beds are represented by the youngest calibrated ages of mer, the low percentage of Mg calcite, with an average of 0.52 mol%, is 3830–3570 cal BP (KK3) and 3760–3500 cal BP (KK4), respectively. indicative of precipitation from the mixing of sea water and meteoric This indicates that beds lying on the seaward side and outer (a few waters or solely from the latter (Scoffin and Stoddart, 1983; Spurgeon meters offshore) parts of beds are concurrent units in the sense of 298 A.E. Erginal et al. / Sedimentary Geology 294 (2013) 294–302

Fig. 3. Interpreted inverse model resistivity tomograms taken perpendicular to the coastline.

deposition, as opposed to the belief that outer units manifest older timeframe, the curves represent different magnitudes of fluctuations generations of beachrock (Psomiadis et al., 2009). Two samples taken before and after 5 ka BP from the perspective of ages acquired from from the landward and seaward edges of slabs yielded very similar values beachrocks. For instance, the curves by Ostrovsky et al. (1977), of 4270–3970 cal BP (KK5) and 4210–3920 cal BP (KK2), respectively. Tchepalyga (1984), Voskoboinikov et al. (1982), Filipova-Marinova In view of middle to Late Holocene sea-level changes in the Black Sea, (2007) and Balabanov (2007) all agree on a decline varying between the ages obtained are of particular importance for the period spanning the −2 m and −8 m at 5.5 ka BP, as against Nevessky's (1970) curve last 5 ka. It is known that the Black Sea has been in equilibrium with the which demonstrates a remarkable descent near −25 m (Fig. 5). For Mediterranean sea-level since their last reconnection at 7500 cal BP the period when early marine-phreatic cements were precipitated at (Fouache et al., 2012). Since then, several authors have dealt with the 5.4 ka, the Filipova-Marinova (2007) and Balabanov (2007) curves ap- sea-level history of the Black Sea (Brückner et al., 2010 and references pear to be the most plausible as they show a sea-level between 0 m therein). and −2 m, which does not conflict with those proposed for the Eastern Superimposed curves illustrative of Holocene sea-level fluctuations Mediterranean (Fouache et al., 2012). This is confirmed by data from during the Holocene infer a rising sea-level trend with important fluctu- the offshore delta lobes of the Danube (Giosan et al., 2006). On the ations up to near 5 ka BP, then rises and falls thereafter in reference to basis of the optical age of beach ridge sands and 14C ages of bivalves the present-day (Martin and Yanko-Hombach, 2011). Regarding this within them, Giosan et al. (2006) suggested that the sea-level in the past 5 ka was between +1.5 m and −2m. Table 1 From 5 ka BP to the present, the level of the Black Sea followed a more List of benthic foraminifera identified in the beachrock samples. regular trend with lower-magnitude fluctuations. With regard to the time span between 4.2 ka and 3.5 ka when many of the beachrock slabs Sample code Foraminifera Number developed, the proposed curves display apparent contradiction. For ex- KK1 Ammonia tepida 35 ample, variations of a few meters in proportion to the present sea-level KK3 Ammodiscus planorbis 5 Patellina corrugata 2 illustrated by Tchepalyga (1984) and Voskoboinikov et al. (1982) as well Quinqueloculina sp. 1 as the calibrated and uncalibrated curves of Filipova-Marinova (2007) are Pseudotriloculina sp. 1 at variance with the relatively regular regressive stage depicted in Rosalina vilardeboana 40 Ostrovsky et al. (1977) and Balabanov (2007).Furthermore,aremarkable Rosalina sp. 1 short time regression around 500 BC is marked by a fall up to −10 m on Cibicides sp. 1 Ammonia sp. 1 all curves, which has been attributed to the postulated Phanagorian re- KUM1 Ammonia parkinsoniana 6 gression by Fedorov (1963),criticizedbyFouache et al. (2012) based Ammonia sp. 7 on archeological, historical and hydrodynamic arguments. Elphidium macellum 20 With regard to the questions raised above, the bimillennial period Elphidium sp. 16 spanning 5.5 ka BP and 3.5 ka BP matches the formation of the studied A.E. Erginal et al. / Sedimentary Geology 294 (2013) 294–302 299

Fig. 4. SEM images from beachrock samples. (a–e) Thick micrite coatings. These coatings are typical in all samples; (a) all samples have high void ratio; (b) close-up view of white square in (a), showing that calcite surfaces are mostly marked by solution pits due possibly to percolated freshwaters during subaerial exposure of beachrock slabs; (c–e) another views of such envelopes; (e) closer view of the square in (d) demonstrating micritic aggregates with thickness of about 20 μm; (f) typical image of meniscus cement; (g) closer view of bridge marked in square showing aggregates of calcite subjected to dissolution, as in (b); (h) low-Mg calcite rims; (i) rims binding juxtaposed siliciclastic grains are thinner than 50 μm and composed of clumps of reciprocal-oriented calcite crystals with scalenohedral terminations. beachrock based on limiting age values. The aforementioned charac- groundwaters in the backshore, followed by meniscus bridges and, to a teristics of cement fabrics in samples are suggestive of the initially lesser extent, rims of low-Mg calcite. This consecutive pattern is typical precipitation of low-Mg calcite to form micritic coatings from meteoric of the precipitation in upper intertidal and vadose zones. Observed

Table 2 EDX analysis results obtained from beachrock cements.

Sample code Analyzed surface Elements (wt.%)

C O Na Mg Al Si Ca Fe MgCO3 (mol%)

KK1 Micritic coating 11.54 50.34 0.5 1.74 2.49 3.92 28 1.5 1.4 KK1 Micritic coating 12.5 51.1 0.56 1.47 1.44 3.08 29.2 0.7 1.17 KK1 Micritic coating 11.09 49.37 0.5 1.63 2.01 3.77 30.5 1.1 1.33 KK2 Micritic coating 11.93 51.28 0.5 1.98 2 4.69 26.4 1.2 1.57 KK2 Micritic coating 13.3 52.67 – 2 0.74 3.74 27.5 – 1.56 KK2 Meniscus bridge 15.49 57.35 ––3.43 4.83 18.9 –– KK3 Meniscus bridge 10.42 52.8 – 1.35 2.59 11.8 21 – 1.06 KK3 Micritic coating 13.64 51.64 – 1.77 – 1.31 31.6 – 1.39 KK3 Radial aggregates 11.63 49.1 – 1.48 – 2.78 35 – 1.21 KK4 Micritic coating 13.18 53.14 – 1.76 – 5.18 26.1 0.6 1.37 KK4 Radial aggregates 11.9 49.9 – 2.06 1.07 – 32.5 – 1.64 KK4 Meniscus bridge 15.4 60.53 –––13.4 10.7 –– KK4 Meniscus bridge 15.54 60.39 –––12.7 11.4 –– KK5 Micritic coating 12.48 50.75 1.7 ––3.92 29.8 –– KK5 Meniscus bridge 14.2 53.92 0.97 1.07 – 4.97 23.5 – 0.82 KK5 Micritic coating 13.45 51.92 – 2.16 – 2.33 30.1 – 1.7 Bedrock Bulk sample 18.6 60 –––0.6 20.3 –– 300 A.E. Erginal et al. / Sedimentary Geology 294 (2013) 294–302

Table 3 Radiocarbon ages of beachrock carbonates (KK) and bivalves recovered from fossil coastal dune (KUM) at backshore. For sample locations, see Fig. 2.

Sample code Lab. code Material dated 14CyrBP 14CyrBP Calibrated age (yr BP) δ13C/12C (measured age) (conventional age) (2 sigma)a (‰)

KK1 BETA-338674 Bulk carb. 4850 ± 30 4990 ± 30 5460–5260 −0.3 KK2 BETA-338675 Bulk carb. 3610 ± 40 4030 ± 40 4210–3920 +0.4 KK3 BETA-338676 Bulk carb. 3420 ± 30 3840 ± 30 3830–3570 +0.4 KK4 BETA-338677 Bulk carb. 3280 ± 30 3700 ± 30 3760–3500 +0.4 KK5 BETA-338678 Bulk carb. 3660 ± 30 4080 ± 30 4270–3970 +0.6 KUM3 BETA-338672 Shell 2850 ± 30 3250 ± 30 3230–2940 −0.6 KUM5 BETA-338673 Shell 4560 ± 30 4960 ± 30 5440–5230 −0.6

a Calibration of samples based on calibration data base information (MARINE09 from INTCAL09) (Stuiver and Reimer, 1993; Reimer et al., 2009). widely in all samples, the coexistence of dissolution on early micritic Another argument associated with coastal processes matching the cements and minute concentrations of MgCO3 within both cements formation of beachrock arises from a relict coastal dune sequence on are likely suggestive of diagenetic alteration by deeply percolated the backshore at the Kıyıköy location. The sandy beach is backed by a freshwaters. 3-m thick dune deposit consisting of polycrystalline quartz, epidote In the present case, climatic conditions might have played an impor- and plagioclase with coloration of opaque iron oxide rings. The sequence tant role with respect to the precipitation of calcium carbonates during also includes fragments of ferro-magnesium minerals as well as poorly the evaporation-prone stages and thereby beachrock cementation. rounded metamorphic rock fragments derived from quartz–epidote– During the abovementioned timeframe, precipitation of amalgamating schist and marble. The bottom and middle levels of the sequence contain carbonates into loose beach sand prior to 3.5 ka would have been pro- fossil shells of D. trunculus and V. gallina, the latter of which is present moted by increased evaporation under drier conditions. Hence, based only in the middle level. The sequence is almost absent of foraminifera on recent data from the Sofular Cave records, the wet period of Holocene with the exception of the bottom level which incorporates Elphidium Climatic Optimum starting from 9.6 ka changed into a drier climate after macellum, broken fragments of Elphidium sp., Ammonia parkinsoniana 5.4 ka BP (Göktürk et al., 2011). Although no record is available for and other Ammonia sp. possible arid periods of the Black Sea to compare with the Eastern From bottom to top, the total amount of CaCO3 in this relict dune, Mediterranean at 4500–3900 BP and 3100–2800 BP (Roberts et al., decreases from 14% to 2%. Coarse and medium sands are predominant 2011), we might suppose that the rest of the samples dated at between (95%). The rest of the dune deposit comprises very fine sand and silt. 4.2 and 3.5 ka are possible indicators of such drier periods. All these components are weakly bonded by meniscus cement The lack of Emiliania huxleyi, recently documented from slightly formed by iron-oxides. Besides being of similar composition to the younger-aged carbonate-cemented coquina on the southeastern Thracian beachrock, two shells of D. trunculus collected from the bottom and Black Sea coast of Turkey (Erginal et al., 2012), also permits forecasting middle levels yielded AMS radiocarbon ages of 5440–5230 cal BP the cementation environment. This calcareous nannoplankton is notably and 3230–2940 cal BP, respectively (Table 2). These ages, as well as abundant in surface waters of the Black Sea (Lancelot et al., 2002)and the compositional attributes specified, are virtually identical to those first appeared in this body of water about 3000 years ago when salinity of beachrock, suggesting that both occurrences are coeval. Nevertheless, prone to its adaptation reached 11‰ (Bukry, 1974). The absence of the this consolidated, well-drained and iron-oxidized dune deposit requires coccolith E. huxleyi within all samples could be indicative of the fact further study owing to its paleosoil-like characteristics. that cementation took place prior to 3500 BP and did not continue thereafter. During the precipitation of connective carbonates just before 5. Conclusions the invasion of the Black Sea by E. huxleyi, on the lower boundary of ecozone 1 at 3300 BP (Giunta et al., 2007), water-salinity was below The beachrock exposures in this study were observed on the the tolerance limit of this coccolith. northwest coast of East Thrace, Turkey. Albeit with a limited exposure,

Fig. 5. Holocene sea-level curves for the Black Sea (partly modified from Martin and Yanko-Hombach, 2011). Data are based on Nevessky (1970), Ostrovsky et al. (1977), Voskoboinikov et al. (1982), Tchepalyga (1984), Balabanov (2007) and Filipova-Marinova (2007). A.E. Erginal et al. / Sedimentary Geology 294 (2013) 294–302 301 the studied beachrock is the first record from the Black Sea coast. The (Eds.), The Black Sea Flood Question: Changes in Coastline, Climate, and Human Settlement. Springer, Dordrecht, The Netherlands, pp. 453–481. ages range between about 5.5 ka BP and 3.5 ka BP, a controversial Folk, R.L., 1974. Petrology of Sedimentary Rocks. Hemphill Publishing, Austin, Texas period with regard to the Middle to Late Holocene sea-level history of (184 pp.). the Black Sea. Predominating coarse grains and small pebbles in the Fouache, E., Kelterbaum, D., Brückner, H., Lericolais, G., Porotov, A., Dikarev, V., 2012. The Late Holocene evolution of the Black Sea — a critical view on the so-called cemented beds are indicative of the fact that the pre-cementation envi- Phanagorian regression. Quaternary International 266, 162–174. ronment was a high-energy shingle beach backed by coastal dunes. Friedman, G.M., 2005. Climatic significance of Holocene beachrock sites along shorelines These dunes are preserved as a relict dune sequence at the backshore of the Red Sea. American Association of Petroleum Geologists Bulletin 89, 849–852. and form a contemporaneous unit based on the AMS radiocarbon age Giosan, L., Donnelly, J.P., Constantinescu, S., Filip, F., Ovejanu, I., Vespremeanu-Stroe, A., Vespremeanu, E., Duller, G.A.T., 2006. Young Danube delta documents stable Black of its bioclasts. Sea level since the middle Holocene: morphodynamic, paleogeographic, and Our results revealed that the thickness of the beds, based on the archeological implications. Geology 34, 757–760. geophysical imaging survey, exceeded the tidal range, implying that Giunta, S., Morigi, C., Negri, A., Guichard, F., Lericolais, G., 2007. Holocene biostratigraphy and paleoenvironmental changes in the Black Sea based on calcareous nannoplankton. the cemented beach could not be simply of intertidal origin. Besides Marine Micropaleontology 63, 91–110. the existence of low-Mg calcite, the secondary cement-producing me- Göktürk, O.M., Fleitmann, D., Badertscher, S., Cheng, H., Edwards, R.L., Leuenberger, M., niscus bridges on early micritic cements and dissolution pits on micrite Frankhauser, A., Tüysüz, O., Kramers, J., 2011. Climate on the Southern Black Sea coast during the Holocene: implications from the Sofular Cave record. Quaternary coatings are likely connected with freshwater penetration due to sub- Science Reviews 30, 2433–2445. aerial exposure of slabs when the sea-level was slightly lower than it Goudie, A.S., 2001. The Nature of the Environment, 4th edition. Wiley-Blackwell, Oxford is today. We assume that the cements were precipitated when Black (560 pp.). Guerra, N.C., Kiang, C.H., Sial, A.N., 2005. Carbonate cements in contemporaneous Sea's salt content was lower than present, based on the absence of beachrocks, Jaguaribe Beach, Itamaracá Island, northeastern Brazil: petrographic, E. huxleyi. We suggest that the cements were first precipitated in geochemical and isotopic aspects. Anais da Academia Brasileira de Ciências 77, the upper intertidal zone when the sea-level was close to the present. 343–352. Hillgaèrtner, H., Dupraz, C., Hug, W., 2001. Microbially induced cementation of carbonate Beachrock formation continued during subaerial exposure of the sands: are micritic meniscus cements good indicators of vadose diagenesis? Sedimen- whole sequence when the sea-level declined slightly (about −2m), tology 48, 117–131. inasmuch as early cements have etched surfaces in consequence of Holail, H., Rashed, M., 1992. Stable isotopic composition of carbonate-cemented recent downward-percolating meteoric waters. beachrock along the Mediterranean and the Red Sea coasts of Egypt. Marine Geology 106, 141–148. Kelletat, D., 2006. Beachrock as a sea-level indicator? Remarks from a geomorphological point of view. Journal of Coastal Research 22, 1555–1564. Acknowledgments Kneale, D., Viles, H.A., 2000. Beach cement: incipient CaCO3-cemented beachrock development in the upper intertidal zone, North Uist, Scotland. Sedimentary Geology Dr. Aydın Büyüksaraç is thanked for allowing us to use the resistivity- 132, 165–170. ı ı Knight, J., 2007. Beachrock reconsidered. Discussion of Kelletat, D., 2006. Beachrock as a meter for this research. We would like to thank Dr. Elmas K rc -Elmas for sea-level indicator? Remarks from a geomorphological point of view. Journal of her help with determination of foraminifera within beachrock samples. Coastal Research 22, 1558–1564. Journal of Coastal Research 23, 1074–1078. We wish to thank Mr. Graham Lee for correction of English text. We Lancelot, C., Staneva, J., Van Eeckhout, D., Beckers, J.-M., Stanev, E., 2002. Modelling the Danube-influenced north-western continental shelf of the Black Sea. Part II: are also indebted to the Journal Editor Dr. Jasper Knight, and two anon- ecosystem response to changes in nutrient delivery by the Danube River after ymous referees for their constructive comments that have greatly im- its damming in 1972. Estuarine Costal Shelf Science 54, 473–499. proved our paper. This study was supported by the Scientificand Loke, M.H., Barker, R.D., 1996. Rapid least-squares inversion of apparent resistivity – Technological Research Council of Turkey (TÜBİTAK) (Project Number: pseudosections using a quasi-Newton method. Geophysical Prospecting 44, 131 152. Martin, R.E., Yanko-Hombach, V., 2011. Rapid Holocene sea-level and climate change in 112Y217). the Black Sea: an evaluation of the Balabanov sea-level curve. In: Buynevich, I.V., Yanko-Hombach, V., Gilbert, A.S., Martin, R.E. (Eds.), Geology and Geoarchaeology of the Black Sea Region: Beyond the Flood Hypothesis. Geological Society of America References Special Paper, 473, pp. 51–58. Mertens, K.N., Bradley, L.R., Takano, Y., Mudie, P.J., Marret, F., Aksu, A.E., Hiscott, R.N., Avşarcan, B., 1997. Yalıtaşı oluşumu ile ilgili kuramlar ve Türkiye kıyılarındaki yalıtaşlarının Verleye, T.J., Mousing, E.A., Smyrnova, L.L., Bagheri, S., Mansor, M., Pospelova, V., bazı özellikleri. İ.Ü Coğrafya Dergisi 5, 259–282 (in Turkish with English abstract). Matsuoka, K., 2012. Quantitative estimation of Holocene surface salinity variation Balabanov, I.P., 2007. Holocene sea-level changes of the Black Sea. In: Yanko-Hombach, in the Black Sea using dinoflagellate cyst process length. Quaternary Science Reviews V., Gilbert, A.S., Panin, N., Dolukhanov, P. (Eds.), The Black Sea Flood Question: 39, 45–59. Changes in Coastline, Climate, and Human Settlement. Springer, Dordrecht, The Nevessky, E.N., 1970. Holocene history of the coastal shelf zone of the USSR in relation Netherlands, pp. 711–730. with processes of sedimentation and condition of concentration of useful minerals. Beşiktepe, S., Sur, H.I., Özsoy, E., Latif, M.A., Oguz, T., Ünlüata, Ü., 1994. The circulation Quaternaria 12, 78–88. and hydrography of the Marmara Sea. Progress in Oceanography 34, 285–334. Ostrovsky,A.B.,Izmaylov,Y.A.,Balabanov,I.P.,Skiba,S.I.,Skryabina,N.G.,Arslanov,S.A.,Gey, Binkley, K.L., Wilkinson, B.H., Owen, R.M., 1980. Vadose beachrock cementation along a N.A., Suprunova, N.I., 1977. Novie dannie opalegidrologicheskom rezhime Chernogo Southeastern Michigan marl lake. Journal of Sedimentary Petrology 50, 953–962. moria v verkhnem pleistotsenei golotsene (New data on the paleohydrological regime Brückner, H., Kelterbaum, D., Marunchak, O., Porotov, A., Vött, A., 2010. The Holocene of the Black Sea in the Upper Pleistocene and Holocene). In: Kaplin, P.A., Shcherbakov, sea level story since 7500 BP — lessons from the Eastern Mediterranean, the F.A. (Eds.), Paleogeografi ia i otlozheniia pleistotsena iuzhnykh morei SSSR. (Pleistocene Black and Azov Seas. Quaternary International 225, 160–179. Paleogeography and Sediments of the Southern Seas of the USSR). Nauka, Moscow, Bukry, D., 1974. Coccoliths as paleosalinity indicators — evidence from Black Sea. In: pp. 131–140 (in Russian). Degens, E.T., Ross, D.A. (Eds.), The Black Sea — Geology, Chemistry and Biology. Pamir, H.N., Baykal, F., 1947. Istranca masifinin jeolojik etüdü. MTA Rap., 2257 (in Turkish). Memoir American Association Petroleum Geologist, 20, pp. 353–363. Psomiadis, D., Panagiotis, T., Konstantinos, A., 2009. Electrical resistivity tomography Calvet, F., Cabrera, M.C., Carracedo, J.C., Mangas, J., Pérez-Torrado, F.J., Recio, C., Travé, mapping of beachrocks: application to the island of Thassos (N. Greece). Environ- A., 2003. Beachrocks from the Island of La Palma (Canary Islands, Spain). Marine mental Earth Sciences 59, 233–240. Geology 197, 75–93. Reimer, P.J., Baillie, M.G.L., Bard, E., Bayliss, A., Beck, J.W., Blackwell, P.G., Bronk Ramsey, Desruelles, S., Fouache, E., Çiner, A., Dalongeville, R., Pavlopoulos, K., Koşun, E., Coquinot, C., Buck, C.E., Burr, G.S., Edwards, R.L., Friedrich, M., Grootes, P.M., Guilderson, T.P., Y., Potdevin, J.L., 2009. Beachrocks and sea level changes since Mid-Holocene: com- Hajdas, I., Heaton, T.J., Hogg, A.G., Hughen, K.A., Kaiser, K.F., Kromer, B., McCormac, parison between the insular group of Mykanos–Delos–Rhenia (Cyclades, Greece) F.G., Manning, S.W., Reimer, R.W., Richards, D.A., Southon, J.R., Talamo, S., Turney, and southern coast of Turkey. Global and Planetary Change 66, 19–33. C.S.M., van der Plicht, J., Weyhenmeyer, C.E., 2009. IntCal09 and Marine09 radio- Erginal, A.E., Ekinci, Y.L., Demirci, A., Kırcı-Elmas, E., Kaya, H., 2012. First note on Holocene carbon age calibration curves, 0–50,000 years cal BP. Radiocarbon 51 (4), coquinite on Thrace (Black Sea) coast of Turkey. Sedimentary Geology 267–268, 1111–1150. 55–62. Rey, D., Rubio, B., Bernabeu, A.M., Vilas, F., 2004. Formation, exposure, and evolution of Fedorov, P.V., 1963. Stratigrafija Krimsko-Kavkazskogo pobrezija I nekotorie voprosi a high-latitude beachrock in the intertidal zone of the Corrubedo complex (Ria de geologicheskoi istorii Chernogo morja (Stratigraphy of Quaternary Deposits of Arousa, Galicia, NW Spain). Sedimentary Geology 169 (1–2), 93–105. Crimean–Caucasian Coastline and Several Questions of Geological History of the Roberts, N., Eastwood, W.J., Kuzucuoglu, C., Fiorentino, G., Caracuta, V., 2011. Climatic, veg- Black Sea). (Trudi GIN AN SSSR, Moscow. Science, tom. 88. [Transactions Geol. Inst. etation and cultural change in the eastern Mediterranean during the mid-Holocene RAS. Moscow, Science 88]). environmental transition. The Holocene 21, 147–162. Filipova-Marinova, M., 2007. Archaeological and paleontological evidence of climate Scoffin, T.P., Stoddart, D.R., 1983. Beachrock and intertidal sediments. In: Goudie, A.S., dynamics, sea-level change, and coastline migration in the Bulgarian sector of the Pye, K. (Eds.), Chemical Sediments and Geomorphology. Academic Press, London, circum-Pontic region. In: Yanko-Hombach, V., Gilbert, A.S., Panin, N., Dolukhanov, P. pp. 401–425. 302 A.E. Erginal et al. / Sedimentary Geology 294 (2013) 294–302

Siesser, W.G., 1974. Relict and recent beachrock from southern Africa. Geological Society Vieira, M.M., De Ros, L.F., 2006. Cementation patterns and genetic implications of Holo- of America Bulletin 85, 1849–1854. cene beachrocks from northeastern Brazil. Sedimentary Geology 192 (3–4), 207–230. Spurgeon, D., Davis Jr., R.A., Shinnu, E.A., 2003. Formation of ‘Beach Rock’ at Siesta Key, Voskoboinikov, V.M., Rotar, M.F., Konikov, E.G., 1982. Sviaz' ritmichnosti stroeniia Florida and its inﬂuence on barrier island development. Marine Geology 200, 19–29. tolshch golotsenovykh otlozhenii Prichernomorskikh limanov s kolebatel'nym Stuiver, M., Reimer, P.J., 1993. Extended 14C data base and revised CALIB 3.0 14C age rezhimom urovnia Chernogo moria (Relationship between the rhythmic composition calibration program. Radiocarbon 35, 215–230. of thick Holocene layers of the Black Sea region lagoons and the oscillatory level regime Tchepalyga, A.L., 1984. Inland sea basins. In: Velichko, A.A., Wright, H.E.J., Barnosky, C.W. of the Black Sea). In: Kaplin, P.A., Klige, R.K., Chepalyga, A.L. (Eds.), Izmeneniia urovnia (Eds.), Late Quaternary Environments of the Soviet Union. University of Minnesota moria. (Sea-Level Fluctuations). Moscow State University, Moscow, pp. 264–274 (in Press, Minneapolis, Minnesota, pp. 229–247. Russian). Türkeş, M., 1996. Spatial and temporal analysis of annual rainfall variations in Turkey. Vousdoukas, M.I., Velegrakis, A.F., Plomaritis, T.A., 2007. Beachrock occurrence, charac- International Journal of Climatology 16, 1057–1076. teristics, formation mechanism and impacts. Earth-Science Reviews 85, 23–46.