Radiocarbon, Vol 57, Nr 3, 2015, p 493–505 DOI: 10.2458/azu_rc.57.18363 © 2015 by the Arizona Board of Regents on behalf of the University of Arizona

SEA SURFACE RADIOCARBON RESERVOIR AGE CHANGES IN THE AEGEAN SEA FROM ABOUT 11,200 BP TO PRESENT Yorgos Facorellis Department of Antiquities and Works of Art Conservation, Faculty of Fine Arts, Technological Educational Institute of Athens, Aghiou Spyridonos St., 12210 Egaleo, Athens, Greece. Corresponding author. Email: [email protected]. Evi Vardala-Theodorou Hydrobiological Department, Goulandris Natural History Museum, 100 Othonos St., 14562 Kifissia,Athens, Greece. Email: [email protected].

ABSTRACT. Archaeological excavations in two coastal sites of Greece, Ftelia on Mykonos and Cyclops Cave on Youra, have provided suitable material (charcoal/marine mollusk shell paired samples deposited simultaneously in undisturbed anthropogenic layers) to estimate regional changes of the sea surface radiocarbon reservoir effect (ΔR) in the Aegean Sea. Moreover, pre-bomb 14C ages of marine mollusk shells of known collection date, from Piraeus and Nafplion in Greece and Smyrna in Turkey, also contributed to the marine reservoir calculation during recent years. In this article, these already published results, 10 in total, are considered and calibrated again using the latest issues of the calibration curves IntCal13 and Marine13. The same calibration data were applied to 11 more paired samples from the archaeological sites of Palamari on Skyros and Franchthi Cave in the Argolic Gulf, published here for the first time, in order to investigate the fluctuation of the reservoir ages R(t) and ΔR values in the Aegean Sea from ~11,200 BP (~13,000 cal BP) to present. Our data show that R(t) and ΔR values are not constant through time and may vary from 1220 ± 148 to –3 ± 53 yr and –451 ± 68 to 858 ± 154 14C yr, respectively. An attempt was also made to correlate these fluctuations with eastern Mediterranean paleo- environmental proxies and other relevant paleoceanographic data found in the literature.

INTRODUCTION It is well known that samples from species living contemporaneously in the atmosphere and sea surface waters (<100 m depth) show different conventional 14C ages. This difference between the 14C ages of such paired samples is called the marine reservoir age R(t), or apparent age. R(t) is not constant (t = cal age) due to the difference in sea surface reservoir and atmosphere 14C-specific ac- tivity changes caused by (1) oceanic circulation processes that tend to advect intermediate and deep 14 14 C-depleted water masses to the surface, (2) atmospheric C production changes, and (3) air-sea CO2 exchange processes (Stuiver et al. 1986, 1998; Stuiver and Braziunas 1993; Siani et al. 2000, 2001).

A global box-diffusion carbon model (Oeschger et al. 1975), which reproduces depth-dependent marine 14C variations in response to atmospheric 14C production changes (Stuiver et al. 1986; Stu- iver and Braziunas 1993), is used in order to estimate the reservoir ages of the global mixed sea surface layer. These were found to be ~400 yr older in the well-ventilated gyres of the central North and South Pacific and the Atlantic Ocean (Bard 1988). Moreover, the magnitude of this effect may also differ from region to region due to e.g. long residence time of deep waters in upwelling areas, which is in turn affected by the coastline shape, climate, and sea bottom topography (Robinson and Thompson 1981; Domack 1992; Dye 1994; Heier-Nielsen et al. 1995; Berkman and Forman 1996) and the hardwater effect in marine organisms that have grown near estuaries (Ingram and Southon 1997; Goodfriend and Flessa 1997).

The local sea surface reservoir deviations (ΔR) from R(t) may be determined either by 14C dating of (1) live-collected pre-bomb marine mollusk shells (Siani et al. 2000; Reimer and McCormac 2002); (2) foraminifera or mollusk shells extracted from marine sediments and plant material from terrestri- al settings, such as peat profiles paired samples, assuming a coeval date of organism death for both sample types, based on volcanic ash onshore/offshore isochrones (Ascough et al. 2005); and (3) marine mollusk shell/charcoal paired samples, assumed to be deposited simultaneously, collected from undisturbed archaeological layers (Facorellis et al. 1998).

Proceedings of the 1st International Radiocarbon in the Environment Conference 18–22 August 2014, Queen’s University Belfast, Belfast, Northern Ireland, UK Edited by Evelyn Keaveney and Paula Reimer 494 Y Facorellis & E Vardala-Theodorou

Consequently, calculation of ΔR allows (1) reliable calibration of the conventional 14C ages of ma- rine samples (e.g. marine mollusk shells), in the absence of other suitable material from an excavat- ed site (as they are usually short-lived samples, rarely transported over long distances), (2) reliable calibration of 14C ages of human bones in case of mixed (marine and terrestrial) diet (Sveinbjörns- dóttir et al. 2010), and (3) obtaining of paleoceanographic information (Siani et al. 2001).

The firstΔ R value in the Mediterranean Sea corresponds to a pre-bomb marine mollusk shell sample collected in AD 1954 at the Kouali Point of Tipasa in Algeria (36°40′N, 2°30′E) (Olson and Bro- ecker 1959; Broecker and Olson 1961), which produced a ΔR value of –133 ± 83 14C yr (Stuiver et al. 1986). Facorellis et al. (1998) then published a mean R(t) of 515 ± 22 yr and a ΔR value of 149 ± 30 14C yr in the Aegean Sea for the time interval 8800–7400 BP (9900–8000 cal BP) based on three paired charcoal/marine mollusk shell samples collected from the Mesolithic anthropo- genic layers of Cyclops Cave on Youra Island. Siani et al. (2000) followed with the publication of 26 modern, pre-bomb marine mollusk shells live-collected between AD 1837 and 1950 throughout the Mediterranean Sea, which enabled estimation of the R(t)mean = 390 ± 85 yr and the ΔRmean = 35 ± 70 14C yr. They also calculated a pre-bomb R(t) value of 520 ± 40 yr in the Dardanelles Strait (collection year AD 1900), which is in a very good agreement with the several millennia older one from Youra Island. Siani et al. (2001) then published another seven tephra charcoal/planktonic for- aminifera paired samples from the South Adriatic Sea spanning from 16,130 to 3820 BP (19,790–

4090 cal BP), which showed significant deviations from the Mediterranean R(t)mean. Additionally, Reimer and McCormac (2002) found that pre-bomb R(t) in at least two Aegean sites [Piraeus, collection year AD 1943, R(t) = 427 yr; and Nafplion, collection year AD 1940, R(t) = 324 yr] is statistically the same at a 95% level with the aforementioned values. A third pre-bomb marine mollusk shell from Smyrna, Turkey (collection year AD 1893/4) produced a much higher R(t) of 652 yr, which may be attributed to the estuarine environment that this marine mollusk species often inhabits (Reimer and McCormac 2002). Subsequently, Facorellis and Maniatis (2002), based on three paired charcoal/marine mollusk shell samples collected from the Middle Neolithic layers of the Ftelia site on Mykonos, calculated a regional mean R(t) of –32 ± 31 yr and a mean ΔR value of –393 ± 40 14C yr for the time interval 6080–5720 BP (7150–6400 cal BP), showing that during that time period there was no significant local sea surface reservoir effect.

All the aforementioned data, together with the Mediterranean Sea R(t) changes since the Last Gla- cial Maximum reported by Siani et al. (2001), indicate that R(t) is not constant through time. In or- der to estimate these changes in the Aegean Sea, we reconsidered all the available data found in the literature (Facorellis et al. 1998; Siani et al. 2000, 2001; Facorellis and Maniatis 2002; Reimer and McCormac 2002), as well as 11 new paired samples we dated from two other archaeological sites in that region, which are presented here for the first time. More specifically, two pairs from Palamari on Skyros and nine more from Franchthi Cave in the Argolic Gulf have been dated. This study aims to present all the up-to-date published regional R(t) values and recalculate the corresponding ΔR values using the latest IntCal13 and Marine13 calibration curves (Reimer et al. 2013), together with the 11 new R(t) and ΔR values from Palamari and Franchthi Cave. Finally, an attempt was made to correlate these values with published southeastern Mediterranean paleoproxies and regional paleoceanographic data in order to understand the underlying reasons for the variability observed.

MATERIALS AND METHODS The new charcoal and marine mollusk shell samples were 14C dated in the laboratory of Archaeom- etry of NCSR “Demokritos” in Athens using the conventional gas counting technique, as described elsewhere (de Vries and Barendsen 1953; Münnich 1957; Kromer and Münnich 1992; Facorellis 1996; Facorellis et al. 1997; Maniatis and Papadopoulos 2011). 14C Reservoir Age in the Aegean Sea, 11,200 BP to Present 495

The two charcoal samples from Palamari (DEM-1036 and DEM-1038) were thoroughly examined and manually cleaned under a stereoscope. The samples were then chemically treated using the standard acid-base-acid treatment to remove all carbon contaminants (Olsson 1979, 1986; Mook and Streurman 1983).

The 11 marine mollusk shells, two from Palamari (DEM-1074 and DEM-1076) and nine from Franchthi Cave (DEM-1048 to DEM-1056), were washed with deionized water in an ultrasonic bath and the depositions on the surface were removed with a dentist’s drill. Next, more than 35% of their remaining weight was removed with a solution of 2% HCl to eliminate any recrystallized carbonates during the time of burial (Goslar and Pazdur 1985; Facorellis et al. 1998). 14C ages of the nine marine mollusk shells samples from Franchthi Cave were paired with the corresponding published 14C ages of charcoal samples originating from the same undisturbed archaeological layers (W R Farrand, personal communication, 2000), which were dated in the University of Pennsylvania 14C laboratory (Lawn 1971, 1974, 1975; Fishman et al. 1977).

The shells of short-lived marine mollusks living in relatively shallow waters are ideal material to be used for the calculation of the sea surface regional reservoir effect R(t) and ΔR values, as they reflect the 14C content of their environment and they are directly related to their archaeological use. Such marine mollusk shells are appropriate only if they are food residues, originating from the same undisturbed anthropogenic layers with the paired charcoal samples. Table 1 summarizes all the available aforementioned information for the marine mollusk species used in this study, proving that they fulfill all the above requirements. From the table, one can see that most of the marine mollusks belong to short-lived (<20 yr), edible species living from just offshore in shallow waters and deeper, on the sea floor at depths less than 100 m (Shackleton and van Andel 1980; Forster 1981; Sabelli et al. 1990; Delamotte and Vardala-Theodorou 2001; Papathanassiou and Zenetos 2005; Papaconstan- tinou et al. 2007; Peharda et al. 2012).

Figure 1 shows the locations of the sites in the Aegean Sea region involved in this study. More spe- cifically, the samples originate from undisturbed anthropogenic layers of the following:

1. The Bronze Age site Palamari on Skyros (38°58′N, 24°30′E) [2 pairs] (Parlama 2007, 2009; Parlama et al. 2010; Pavlopoulos et al. 2010);

2. Neolithic, Mesolithic and Paleolithic layers of Franchthi Cave in Porto Cheli, Argolic Gulf (37°25′20.90″N, 23°7′52.73″E) [9 pairs] (Lawn 1971, 1974, 1975; Fishman et al. 1977; Jacob- sen 1981; Jacobsen and Farrand 1987; Farrand 2000, 2003; Perlès 2001, 2003; Facorellis 2003, 2011, 2013);

3. The Neolithic site Ftelia on Mykonos (37°27′N, 25°22′E) [3 pairs] (Sampson 2002; Facorellis and Maniatis 2002);

4. The Neolithic and Mesolithic layers of Cyclops Cave on Youra (37°27′N, 24°10′E) [4 pairs] (Facorellis et al. 1998; Facorellis 2003, 2013; Sampson 2008, 2011); and

5. Three pre-bomb 14C ages of marine mollusk shells from Piraeus (37°56′N, 23°38′E), Nafplion (37°32′N, 22°47′E), and Smyrna, Turkey (38°26′N, 27°9′E) (Reimer and McCormac 2002).

It is worth noting that the successive cultural phases in the Helladic area are roughly correlated to the Paleolithic, which ends at ~10,000 BC, the Mesolithic (10,000 to ~6500 BC), the Neolithic (~6500 to 3200/3000 BC), and the Bronze Age (3200/3000 to 1050/1025 BC). 496 Y Facorellis & E Vardala-Theodorou - - m m m m m

Living zone Intertidal zone, just off shore to depths of 100 m Intertidal zone to depths of 100 m, distribut ed in ~1–40 m From just offshore to 130 m depth Upper sublittoral zone transitional ecosystem lagoons, estuaries 1–40 m Upper sublittoral zone 1–20 Intertidal 0.5 m to 40 depth 1–150 m sublittoral to circalittoral zone Midlittoral to sublittoral and more from 0.5–60 m Midlittoral to sublittoral 1–40 Midlittoral to sublittoral 1–40 Midlittoral to sublittoral 1–40 Midlittoral to sublittoral 1–40 ; English: edible cockle or coques Consumption interest Edible; in some locations the species is commercially important as seafood resource; major interest Edible; Croatian cuisine Edible; widely collected for human consumption; major interest Edible; excellent seafood; major interest Edible; collected locally in Nestos and Vistonis lagoons for human consumption Edible; French: common European cockle Edible; excellent seafood; major interest Edible; excellent seafood; major interest Edible; minor commercial interest Inedible, used as fishing bait Inedible Inedible Edible - >20 yr

Lifespan Up to 16 yr, with max length 7 cm Ages range from 5 months to 11 yr (Peharda et al. 2012) >40 yr (Forster 1981), slow grow ing, 6 cm in 15–17 yr (Forster 1981; Papaconstantinou et al. 2007) 10–16 yr (Peharda et al. 2012) grow very old 20+ yr (Papaconstantinou et al. 2007) -

Linnae Lmck, Poiret, HAWSS IN Linnaeus, Bruguière, Linnaeus, 1758 Linnaeus, 1758 Defrance, 1820 Linnaeus, 1758 Linnaeus, 1758 Linnaeus, 1758 Linnaeus, 1758 Linnaeus, 1758 Table 1 Summary of the marine mollusk shell species information used in this study for estimation sea surface reservoir Aegean Sea. Shell species Arca noae Acanthocardia tuberculata us, 1758 Barbatia barbata Callista chione Cerastoderma glaucum 1789 Cerastoderma edule 1758 Mytilus edulis Mytilus galloprovincialis 1819 Ostrea edulis Pinna nobilis Gastropoda Cerithium vulgatum 1792 Columbella rustica Conus mediterraneus BRUGUIRE, 1792 Diodora italica 14C Reservoir Age in the Aegean Sea, 11,200 BP to Present 497 ) ® Living zone Subtidal to sublittoral 5–30 m Lower Midlittoral Midlittoral Figure 1 Map of the Aegean Sea indicating the geographic the indicating Sea Aegean the Map of 1 Figure location of the study sites (modified from Google Earth Consumption interest Edible; excellent seafood; major interest, fishing bait Edible; limpets are widely collected for human consumption and as fishing bait; minor commercial interest Edible; limpets are widely collected for human consumption and as fishing bait; minor commercial interest Lifespan Gmelin in Linnaeus, 1758 Linnaeus, 1758 Table 1 Summary of the marine mollusk shell species information used in this study for estimation sea surface reservoir Aegean Sea. Shell species Hexaplex trunculus Patella caerulea Patella ulyssiponensis L., 1791 4) the Neolithic and Mesolithic layers of Cyclops cave on Youra (37° 27΄ N, 22´ N, 24° 10´ E) [4 pairs] (Sampson 2008, 2011; Facorellis et al. 1998; Facorellis 2003, 2013) and 5) three pre-bomb radiocarbon ages of marine mollusk shells from Piraeus (37° 56΄ N, 23° 38´ E), Nafplion (37° 32΄ N, 22° 47´ E) and Smyrna, Turkey (38° 26΄ N, 27° 9´ E) (Reimer and McCormac 2002).

It is worth noticing that the successive cultural phases in the Helladic area are roughly defined in a consensual manner to the Palaeolithic, which ends at ca. 10,000 BC, the Mesolithic (10,000 to ca. 6,500 BC), the Neolithic (ca. 6,500 to 3,200/3,000 BC) and the Bronze Age period (3,200/3,000 to 1,050/1,025 BC). 498 Y Facorellis & E Vardala-Theodorou RESULTS AND DISCUSSION RESULTS AND DISCUSSION TableThe Appendix 2 presents (online all the supplemental dating results file) sorted presents by age.all the A totaldating of results 21 pairs sorted of samplesby age. Aare total shown of 21 includingpairs of samples the three are shown,single preincluding-bomb the marine three mollusksingle pre-bomb samples marine of known mollusk collection samples date.of known The 14 13 conventionalcollection date. CThe ages conventional of the samples 14C ages were of the calcu sampleslated wereusing calculated δ C val uesusing of δ -1325C ‰values for ofcharcoa –25‰l andfor charcoal1‰ for andma rin1‰e molluskfor marine shel molluskls (Stuiver shells and (Stuiver Polach and 1977 Polach), which 1977), are which the typicare theal typicalvalues usedvalues for used that for type that oftype material of material in the in Aegeanthe Aegean region region (Facorellis (Facorellis et etal. al. 1998) 1998).. However, However, these 13 13 δδ13C valuesvalues maymay have have a apossible possible ±2‰ ±2‰ error error due due to 13 toC variationC variation (Stuiver (Stuiver and Polach and Polach 1977), 1977which), 14 whichcorresponds correspond to an additionals to an ±32additional yr error ±32 in the yr calculated error in 14theC ages. calculated This was incorporatedC ages. This into was the 14 incorporatedfinal14 C age error into ofthe the final new samplesC age error by using of the the newfollowing samples formula by using for summing the following errors: formula for summing errors:

! ! (1) σ!"#$% = σ!"! + σ!"# TheThen 14 theC ages 14C ofages the ofcharcoal the charcoal samples samples were then we recalibrated calibrated with with the theIntCal13 latest calibrationissue IntCal13 curve of (Re the- internationalimer et al. 2013). calibration The 14C curve ages of(Reimer the marine et al. mollusk 2013). shell The samples14C ages were of the calibrated marine molluskusing the shell cal- samplesculated Δ weR valuere calibrated corresponding using thefor calculatedeach pair ( AppendixΔR value) correspondingin conjunction withfor eachthe Marine13 pair (Table inter 2)- inationaln conjunction calibration with curve. the AllMarine13 calibrations international were performed calibration with the curve OxCal. vAll 4.2.4 calibrations software (Bronk were performedRamsey 2009). with All the calibrated OxCal v dates4.2.4 aresoftware rounded (Bronk to the Ramseynearest decade. 2009, 2010). All calibrated dates are rounded to the closest decade. The regional sea surface reservoir R(t) value of each pair is calculated by subtracting the 14C con- ventional age of the charcoal sample from that of the marine mollusk sample. The R(t) error is The regional sea surface reservoir R(t) value of each pair is calculated by subtracting the 14C calculated using a similar formula for summing errors as mentioned above. conventional age of the charcoal sample from that of the marine mollusk sample. The R(t) errorThe local is calculated deviation by ΔR using values a similarare calculated formula by for combining summing the errors calibrated as mentioned ages of the above. terrestrial and marine samples, using the latest issues of the atmospheric and marine international curves (Reimer Theet al. local2013), deviation respectively, ΔR as valuesfollows are(Southon calculated et al. 1995;by combining Facorellis etthe al. 1998).calibrated The measuredages of the14C terrestrage of theial andterrestrial marine sample sample gives, each a calendar time using date usingthe latest the atmosphericissues of the calibration atmospheric curve. and Based the marineon this calendarinternational date, thecurves marine (Reimer calibration et al. curve2013) gives respectively an equivalent (Southon 14C age. et al.ΔR 1995; is the Facorellisdifference 14 etbetween al. 1998) this asequivalent follows: and the the measured measured C14 Cage age of for the the terrestrial marine sample. sample In gives this study, a cal endarthis is dateper- usingformed the with atmospheric the OxCal vcalibration 4.2.4 software curve using. Based the followingon this calendar routine, date,as adapted the marine for the calibrationPalamari-1 14 curvepaired givessamples an (Appendixequivalent, FigureC age. 2). ForΔR eachis the pair difference of samples, between the uncertainty this equivalent U(x ,x ) andwas theset 14 1 2 measuredaccordingly, Cso agethat thefor ΔtheR probabilitymarine sample. distribution In this is atstudy the center, this ofis theperformed plot. with the OxCal v4.2.4 software using the following routine, as adapted for the Palamari-1 paired samples Plot() (Table 2, Figure 2). For each pair of samples the uncertainty U(x1,x2) was set accordingly, so that { the ΔR probability distribution is at the center of the plot. Curve(“IntCal13”,”IntCal13.14c”); Plot() Curve(“Marine13”,”Marine13.14c”); { Delta_R(“PALAMARI-1”,U(0,600)); Curve("IntCal13","IntCal13.14c");Combine() { 4 Curve(“=IntCal13”);

R_Date(“DEM-1036”, 3545, 41); Curve(“=PALAMARI-1”); R_Date(“DEM-1076”, 4161, 51); }; }; 14C Reservoir Age in the Aegean Sea, 11,200 BP to Present 499

Figure 2 Example of probability distribution plot for the Palamari-1 pair ΔR value (Appendix)

Figure 3 shows the plot of R(t) values in the Aegean Sea versus 14C age from ~11,200 yr BP until present (black dash-dotted line), with respect to the pre-bomb mean R(t) value in the Mediterranean

Sea [R(t)mean = 390 ± 85 yr, area between the red dotted lines], as estimated by Siani et al. (2000). This figure also includes, for comparison purposes, data (spanning from ~10,400 to 16,000 BP) from the South Adriatic Sea (Siani et al. 2001, supplementary online material). One can see that the R(t) values fluctuate significantly from 1220 ± 148 (Franchthi-9) to –3 ± 53 yr (Ftelia-2), resulting in regional ΔR values ranging from –451 ± 68 (Ftelia-3) to 858 ± 154 14C yr (Franchthi-9). Of the 21 pairs (Appendix), 13 pairs (Piraeus, Nafplion, Palamari-1 and -2, Franchthi-1, -2, -3, -6 and -7, Youra-1, -2, -3 and -4) produced R(t) values falling within two standard deviations (2σ, probability 95.4%) in the range of the Mediterranean pre-bomb mean value.

The prevailing question concerning our data is whether these sea surface reservoir ages R(t) are valid for all over the Aegean Sea within the same time period. Until further research adds new ev- idence, the black dash-dotted line connecting the points in Figure 3 is only tentative. By carefully looking at our results, one can see that there is an intrasite repeatability, overlapping within one standard deviation (1σ, probability 68.3%), in the following cases:

1. Ftelia site on Mykonos, three pairs (Ftelia-1, -2 and -3): mean R(t) = 26 ± 96 yr and mean ΔR = –400 ± 113 14C yr for the time interval 7150–6400 cal BP. 2. Franchthi Cave, two pairs (Franchthi-2 and -3): mean R(t) = 357 ± 120 yr and mean ΔR = –34 ± 123 14C yr and for two more pairs (Franchthi-4 and Franchthi-5): mean R(t) = 765 ± 161 yr and mean ΔR = 461 ± 140 14C yr for the time intervals 7690–7440 and 9140–8520 cal BP, respec- tively. 3. Cyclops Cave on Youra, three pairs (Youra-1, -2, and -3): mean R(t) = 529 ± 90 yr and mean ΔR = 167 ± 116 14C yr for the time interval 9530–8050 cal BP. 500 Y Facorellis & E Vardala-Theodorou

Figure 3 Changes of the sea surface reservoir age R(t) in the Aegean Sea versus 14C age (yr BP) (black dash-dotted line), with respect to the pre-bomb R(t) in the Mediterranean Sea calculated by Siani et al. (2000) (within 2σ, area between the red dotted lines), in comparison with the sea surface temperature fluctuation in the South Adriatic Sea (modified from Siani et al. 2000). Data from the South Adriatic Sea are from Siani et al. (2001, supplemental online material). Intraregional repeatability is observed between the Franchthi-6 (10,000–9540 cal BP) and Youra-4 (9910–9700 cal BP) pairs, which happen to be the only pairs of our study that chronologically overlap: mean R(t) = 267 ± 88 yr and mean ΔR = –37 ± 99 14C yr. Although this specific sea surface reservoir effect is now confirmed by the measurement of two independent pairs from two different sites, one mainland (Franchthi Cave) and one island (Cyclops Cave on Youra), the Youra-4 pair was initially rejected by Facorellis et al. (1998), as it was considered an outlier at the time due to lack of confirming evidence.

There are two sites that produced outlying R(t) values, Franchthi Cave in the Argolic Gulf (Franchthi-4, -5, -8, and -9 pairs) and Ftelia on Mykonos Island (Ftelia-1, -2, and -3 pairs). The R(t) values of the Franchthi-8 and -9 pairs and those of Franchthi-4 and -5 are higher than the Mediterranean

R(t)mean value by a factor of 3 and 2, respectively (Appendix, Figure 3). On the other hand, the Ftelia pairs R(t) values are lower by a factor of 1.

There is only one data set of paired samples from the eastern Mediterranean Sea found in the litera- ture (Siani et al. 2001, supplemental online data) that coincides chronologically with our data. More specifically, this is the charcoal/planktonic foraminifera pair (OCF97129PP & R-704/GIFA96208), whose charcoal (from the Agnano Pomici Principali eruption) age (10,450 ± 40 BP) overlaps within 2σ with the charcoal age (10,260 ± 110 BP) of the Franchthi-8 pair (Figure 3, dashed rectangle). 14C Reservoir Age in the Aegean Sea, 11,200 BP to Present 501

Their corresponding R(t) values are 380 ± 100 and 988 ± 120 yr, respectively. This important R(t) difference shows that there is a different prevailing mechanism providing 14C-depleted water in the Argolic Gulf, than that of the Mediterranean Sea.

The subsurface hydraulic communication between the Argolic plain (Argon field) and the Argolic Gulf was known since ancient times. Pausanias (Arcadica, §7–8) mentions that the word argon means “slow cultivation”; thus, “Argon field” means a field of slow cultivation. This is due to the occasional flooding during wintertime, caused by water coming from the surrounding mountains and the karstic springs flowing from the margins, consisting mainly of multifolded cretaceous lime- stones (Pindos geotectonic unit). The Argon field would have probably turned into a lake if the wa- ter had not been drained through a ground rift. In this case, the rift is apparently the cave-sinkhole of Nestani, which is located at the lowest topographic point of the whole field. After a few days (based on modern tracing experiments), the water reappears from this sinkhole in a submarine system of karstic springs in the Argolic Gulf, that in ancient times were known as Dini, located near Kiveri village (Mariolakos and Mariolakos 2004). In addition, there are also three rivers, named Tanos, Kephalari (Erasinos), and Inachos, emanating from the mountains Lirkio and Trachi that flow into the Argolic Gulf. Consequently, the aforementioned sources of freshwater near Franchthi Cave indicate that the significantly higher R(t) values of the regional sea surface reservoir, compared to Mediterranean mean, may be a phenomenon caused by a combination of a predominant local hard- water effect and coastal retreat events during deglaciation (Shackleton and van Andel 1980; van Andel and Lianos 1983; Lambeck 1996). The higher R(t) value of the Franchthi-9 pair, of 1220 ± 148 yr, is observed during the Younger Dryas stadial (11,240 ± 140 BP or 13,380–12,790 cal BP).

Mykonos is an island of the Cyclades located almost at the center of the Aegean Sea. The three pairs from the Ftelia site gave R(t) values that are overlapped within 1 standard deviation, thus leaving no room for doubt about their validity. However, the calculated mean R(t) value (26 ± 96 yr) is consid- erably lower than the Mediterranean mean. The low regional R(t) value could only be explained by reduced mixing rates of the surface waters with 14C-depleted waters from greater depths, during the time period studied (about 6100–5700 BP or 7150–6400 cal BP).

In an attempt to propose a mechanism involved, we discuss the following environmental events and paleoproxies: (1) the sea surface temperature fluctuation and (2) the sapropel S1 formation in the Aegean Sea.

(1) Sea Surface Temperature Fluctuation The Aegean Intermediate Water is derived from the Levantine Intermediate Water, which travels north along the Turkish coast. Prevailing offshore winds allow upwelling of the intermediate water to the surface, thus forming a single uniform water mass from the surface to the seafloor (Lascaratos 1989; Yüce 1995). As the upwelled Aegean Intermediate Water moves northward, its salinity con- tinues to increase due to evaporation and this together with winter cooling increases its density. This buoyancy loss drives the formation of Aegean Deep Water. The modern Aegean Sea is an important source of deep water for the eastern Mediterranean (Casford et al. 2002). Several Holocene cool- ing events reconstructed for the southern Adriatic Sea, lasting some hundred years, are apparently synchronous with those in the Aegean Sea, in which sea surface temperatures declined by approx- imately 2°C around 6000 and 3000 yr BP (Sangiorgi et al. 2003). Figure 3 shows the R(t) changes in the Aegean Sea with respect to the sea surface temperature fluctuation in the South Adriatic Sea (modified from Siani et al. 2001). Our data show that the 6000 yr BP cooling event coincides with an important decrease of R(t) values of the three paired samples from the Neolithic site Ftelia on Mykonos. However, cooling of the surface waters is expected to increase their density and make 502 Y Facorellis & E Vardala-Theodorou them move deeper into the sea, causing high mixing rates with 14C-depleted bottom waters, thus resulting in higher rather than lower R(t) values, as in the case of the Ftelia pairs.

(2) Sapropel S1 Formation in the Aegean Sea Sapropels develop during episodes of reduced oxygen availability and increase the nutrient supply in bottom waters as a result of reduced deep seawater circulation. The most recent sapropel S1 in the eastern Mediterranean Sea formed from 9500 until 6000 yr BP (Mercone et al. 2000; Casford et al. 2002). The low R(t) values of the Ftelia pairs (Appendix, Figure 3) were likely caused by the low mixing rates of the sea surface waters due to the reduced deep-sea circulation of 14C-depleted waters during the sapropel S1 formation.

CONCLUSIONS Three live-taken pre-bomb marine mollusk shells from Piraeus and Nafplion in Greece and Smyr- na in Turkey, as well as 18 charcoal/marine mollusk shells pairs from the archaeological sites of Franchthi Cave in the Argolic Gulf, Cyclops Cave on Youra, Ftelia on Mykonos, and Palamari on Skyros allowed calculation of the sea surface reservoir age changes R(t) and regional deviations ΔR in the Aegean Sea from ~11,200 BP (~13,000 cal BP) to present. Our data show that the R(t) and ΔR values in the Aegean Sea are not constant through time and may vary from 1220 ± 148 to –3 ± 53 yr and –451 ± 68 to 858 ± 154 14C yr, respectively.

Thirteen pairs produced R(t) values falling within 2σ of the Mediterranean pre-bomb mean value

R(t)mean = 390 ± 85 yr. Two sites produced outlying R(t) values, Franchthi Cave and Ftelia. The mean R(t) and ΔR values for the Ftelia site is R(t) = 26 ± 96 yr and ΔR = –400 ± 113 14C yr for the time interval 7150–6400 cal BP. This very low R(t) value is probably due to the reduced deep-sea circulation of 14C-depleted waters during the sapropel S1 formation. The Franchthi Cave mean R(t) and ΔR values exhibit significant fluctuation probably due to the hardwater effect in the Argolic Gulf. During the time intervals 9140–8520 and 7690–7440 cal BP, the following mean values were calculated, respectively: R(t) = 765 ± 161 yr and ΔR = 461 ± 140 14C yr and R(t) = 357 ± 120 yr and ΔR = –34 ± 123 14C yr. The Cyclops Cave paired samples resulted in mean R(t) = 529 ± 90 yr and ΔR = 167 ± 116 14C yr for the time interval 9530–8050 cal BP. Combined data from Franchthi and Cyclops Cave produced mean R(t) = 267 ± 88 yr and ΔR = –37 ± 99 14C yr for the time interval 10,000–9540 cal BP.

The final goal of this ongoing project is to establish a regional detailed curve for short-lived marine mollusk shells from various coastal sites in the Aegean covering all the time range of the 14C dating method. This will allow accurate calibration of marine samples from that region in conjunction with the marine international calibration curve, and to obtain more paleoceanographic information for the region and time periods studied.

ACKNOWLEDGMENTS The authors would like to thank Dr Yannis Maniatis for allowing the use of the 14C dating facility of the Laboratory of Archaeometry, NCSR “Demokritos” in Athens. Many thanks are also due to the archaeologists: Prof Adamantios Sampson, University of the Aegean, director of the Cyclops Cave excavation on Youra and Ftelia site on Mykonos; Prof Karen D Vitelli, Indiana University, director of the Franchthi Cave excavation; Drs Liana Parlama and Maria Theochari of the Greek Ministry of Culture, co-directors of the excavation at Palamari on Skyros, for providing the necessary sam- ples and archaeological information. We also thank the late Prof William R Farrand, University of Michigan, who indicated the most prominent undisturbed anthropogenic layers of Franchthi Cave 14C Reservoir Age in the Aegean Sea, 11,200 BP to Present 503 from which it was advisable to date marine mollusk shells, and Prof Catherine Perlès, University Paris Ouest Nanterre, for helping to locate them at Leonardo’s warehouse of the D’Ephoreia of Prehistoric and Classical Antiquities in Nafplion. We also thank Dr Brian Damiata, research asso- ciate at UCLA; Prof Christopher Bronk Ramsey, Oxford University; Prof Paula Reimer, Queen’s University of Belfast; and Dr Stella Katsarou-Tzouveleki, archaeologist at the Greek Ministry of Culture for helpful comments and discussion in the field of their expertise; as well as ΙΚΥ (Greek State Scholarships Foundation) and INSTAP (Institute for Aegean Prehistory) for funding.

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