Z. Geomorph. N.F. 53 GeoarchaeologicalSuppl. 1 169 ^ challenges190 Berlin ´ Stuttgart Juni 2009 169

Geoarchaeological challenges in the continental shelf () V. Kapsimalis, K. Pavlopoulos, I. Panagiotopoulos, P. Drakopoulou, D.Vandarakis, D. Sakelariou, C. Anagnostou

with 8 figures and 1 table

Summary. The present day Cyclades Plateau in Central Aegean Sea () is characterised by the presence of numerous small islands and an extended shelf. The interpretation of high-resolution seismic profiles reveals that the shelf has been subjected to successive stages of submergence and emergence due to the Quaternary relative sea level changes.This has resulted to shelf seabed erosion by sub-aerial conditions or palaeo-surfaces burial by thick deltaic/coastal sequences.Within this complicated habitat, it is very dif- ficult for Palaeolithic human remains to be discovered due to their elimination by physical processes. On the basis of present study's bathymetric data set and applying the model developed by Lambeck (1996), a detailed description of the palaeo- of Cyclades shelf since the Last Glacial Maximun (LGM) (ca. 20,000 B.P.) has been accomplished. In addition, a statistical analysis has shown a loss of the three-fourth of the initial surface area of the Plateau, up to present time.The low-lying shelf areas, with an average slope of 1.58o, perhaps provided appropriate conditions for sustaining human, animal and plant life. Therefore, parts of this area could present high geoarchaeological interest improving our knowledge in relation to human activities and associated environments duringeschweizerbartxxx Uppermost author Palaeolothic, Mesolithic and Neolithic. Key words: shoreline displacement ^ palaeo-geomorphologic reconstruction, plateau ^ Cyclades

Zusammenfassung. Der kykladische Inselschelf im ØgÌisraum (Griechenland) wird als Epikontinental- meer mit hoch differenzierter Geomorphologie bezeichnet. Sein charakteristisches Merkmal ist eine groÞe Zahl von kleinen und groÞen Inseln. Die Analysen von lithoseismischen Profilen liefern Informa- tionen Ïber die verschiedenen Phasen der Meeresspiegelschwankungen wÌhrend des QuartÌrs. Erosions- flÌchen, Delta- und KÏstenformationen sind die Indikatoren dafÏr. In diesem komplizierten System menschliche Zivilizationsrelikte des PalÌolithikums zu entdecken, scheint eine schwierige Aufgabe zu sein. Aufgrund von existierenden bathymetrischen Daten und unter Anwendung des Modells von Lambeck (1996) entstand eine genaue Beschreibung der PalÌogeographie des kykladischen Inselschelfs seit dem LGM (die letzten 20.000 Jahre). Statistische Rechnungen zeigen, dass drei Viertel des,wÌhrend dieser Zeit existierenden Landes der Kykladen, vom Meer bedeckt waren. Die flache Neigung der SchelfoberflÌche lieferte wahrscheinlich geeignete Bedingungen sowohl fÏr die Entwicklung des menschlichen Lebens als auch der Tier- und Pflanzenwelt. Es scheint sehr interessant zu sein, unsere Kenntnisse Ïber die Bezie- hungen zwischen Umwelt und Mensch wÌhrend der palÌolithischen, mesolithischen und neolithischen Zeit zu erweitern.

1 Introduction It is well documented for over 40 years that the global spread of humanity was enhanced by the emergence of continental shelf regions during the Pleistocene glacial phases, since extended migration routes were created, i.e. through connection of land masses and easy crossing of sea channels (Masters &Flemming 1983). New marine techniques have contributed significantly

DOI: 10.1127/0372-8854/2009/0053S1-0169 0372-8854/09/5301-0169 $ 5,50 ß 2009 GebrÏder Borntraeger, D-14129 Berlin ´ D-70176 Stuttgart 170 V. Kapsimalis et al. to the detection of the seafloor and substratum of the shelves for finding evidence of hominid and modern human occupation (Green 2004). Stone tools, bones, fireplaces, food remains, and cut timbers with age ranging from 5,000 to 1 million years ago, found in the continental shelves of South Africa, Japan, Australia, North America, and Europe are proofs for the existence of human establishments in these areas during Pleistocene Age (Flemming 2004). Prehistoric remains in the continental shelves cannot be easily discovered since they have been probably destroyed due to coastal erosion, decay, disintegration, etc. or have been disap- peared due to their burial from the occurring sedimentation processes (Bailey &Flemming 2008). However, archaeological finds in the submerged landscapes cannot provide by themselves clear understanding of early human settlement and migration. This happens since during the periods of lower sea level, coastal environments which are now submerged might have provided completely different conditions for the survival of the plants, animals and humans compared with these prevailing in the modern coastal areas (Van Andel 1989; Faure et al. 2002). Thus, it must be emphasised the importance of the different types of submarine surveying (e.g. bathy- metric, geophysical, sedimentological) in filling the gap in the knowledge of the nature of the palaeo-coastal resources associated with periods of lower sea level. This can lead to the provision of important information used for the evaluation of existing conceptions and hypotheses have been already derived by the archaeological findings. In addition, underwater geographical, geolo- gical and geophysical research may contribute remarkably to the discovery of these prehistoric submarine sites which can afford a sufficient amount of archaeological finds and a convenience in their exploration. The present investigation, based on acoustic,eschweizerbartxxx author bathymetric and archaeological data, examines the Quaternary stratigraphy and internal structure of the Cyclades Shelf and suggests particular areas of high archaeological potential. In particular, a Geographical Information System (GIS) has been used to display the geometric characteristics and morphologic modifications in the Cyclades Plateau since the Last Glacial Maximum (LGM). Thus, present study compared to the relative studies of other researchers (Lambeck 1996; Lambeck &Purcell 2005) describes in a more detailed way the Cycladic landscape variation during the last 20,000 years in combination with prehistoric human settlements and activities. The already identified prehistoric human establishments in the Cyclades region and the present's study geophysical and geomorphologic information support the concept that the submerged part of the Cyclades Plateau is a site of great archaeological interest.

2 Cyclades Plateau 2.1 Geological evidence The Cyclades Plateau is a marginal platform characterised by complicated geomorphology (Dermitzakis &Papanikolaou 1981), with water depths being lower than 250 m, and by numerous outcropping islands (Fig. 1). It divides the relatively shallower northern Aegean Sea (depths ranging from 400 to 800 m) from the deeper Sea (Cretan Sea, depths ranging from 1,500 to 2,500 m). The Plateau area constitutes part of the Attic-Cycladic complex, consisting of metamorphic and igneous rocks (Hejl et al. 2002). Sedimentary formations are Geoarchaeological challenges 171

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Fig. 1. Location map and bathymetry of the Cyclades Plateau. Contours are expressed in meters. limited, whilst very low discharges (from small rivers and streams) of sediment matter into the sea have been recorded (Poulos 2009). At present, the Cyclades Plateau is considered as an almost aseismic region surrounded, however, by zones of high seismic and volcanic activity (Papazachos 1990). Granulometric studies associated with the surface sediments of the Cyclades Plateau carried out previously by Volakis &Anagnostou (1993), and Anagnostou et al. (1993b, 1998) reveal the existence of medium to coarse-grained biogenic sands (mean grain sizes varying from 600 to 900 mm), with high percentages of the total carbonate fraction (up to 70%). Most of the sediments are moderately well-sorted and only the terrigenous sand fraction of the sedimentary material (30^40%) is moderately well to well-sorted; this consists of sub-rounded grains (indicating its relict 172 V. Kapsimalis et al. character) originating from reworked palaeo-beaches during the late stages of the Last Glacial period (ended between ca. 10,000 and 15,000 B.P.). The biogenic fraction consists mostly of coralline algal debris (Lithothamnium and Phymatoliton sp.), coral debris (Derdrophylia sp.) and mollusc shell debris (Calliostoma sp.,Caecum trachea, etc.), implying modern calcareous sedimentation. The sedimentological study of the Plateau sea bed and the configuration of the relative bed- forms have been presented by Anagnostou et al. (1993a), Lykousis et al. (1995), Karageorgis et al. (1997), and Lykousis (2001).These authors analysing side-scan sonar images, high-resolution acoustic profiles and sea-bed samples have shown that sandy sediments are arranged into a variety of sub-aqueous bedforms such as sand dunes, ribbons and ripples. The thickness of these bedforms varies from a few decimetres to 6 meters.

2.2 Palaeoclimatic evidence High-resolution palaeoclimatic data derived from the examination of planktonic foraminifera and pollen assemblages in bottom sediments from southwesten Aegean Sea (Geraga et al. 2005), indicate the existence of two major climatic periods since LGM: (i) from ca. 20,000 to 10,000 B.P.; and (ii) from 10,000 B.P. to present day. In addition, some other climatic events of shorter dura- tion have been also identified since the Last Glacial Maximum (LGM). Within this time interval, two cold phases can be defined at approximately ca. 14,000 and 11,000 years B.P., which probably correspond to the H (Heinrich) 1 and Younger Dryas events, respectively. Further, three more cold phases can be detected at ca. 9,700, 7,300 and 6,000 years B.P. Finally, the correlation of the aforementioned data with the lithostratigraphiceschweizerbartxxx author sequence at the Franchthi Cave (Geraga et al. 2005) exhibits a good agreement between these particular palaeoclimatic events and the ethno- lithostratigraphic changes or hiatuses. The above results infer that climate had a significant impact on human accommodation during the Stone Age in the southwestern Aegean Sea.

2.3 Geomorphologic changes The analysis of seismic data by Lykousis (2009) provides the subsidence rates of the Aegean margins during the Middle-Upper Pleistocene and suggests a conceptual model concerning the paleogeographical evolution of the Aegean Sea. Particularly, this study argues that during oxygen isotopic stages 12 and 10 (480^350 kyrs B.P.), and stage 8 (300^250 kyrs B.P.) Cyclades Plateau constituted a great land mass which bridged Greek mainland with Minor Asia. Additionally, during oxygen isotopic stage 6 (180^140 kyrs B.P.) this land mass was separated by the Minor Asia via a strait located at the eastern side of ---Donoussa- landmass. Finally, at the Last Glacial Period (oxygen isotopic stage 2, 30^18 kyrs B.P.), the Plateau obtained

the form of a mega' island'. Moreover, Lambeck (1996) calculated the relative sea level rise in the Cyclades area and based on bathymetric data sets, interpolated on a 180 m grid, estimated the shoreline displace- ments from the Late Palaeolithic to present day. That study used a numerical model which took in consideration the eustatic, isostatic and tectonic components. This kind of model has been applied successfully in the French Mediterranean (Lambeck &Bard 2000), Italian (Lambeck et al. 2004a) and central Mediterranean (Lambeck et al. 2004b) coasts. Geoarchaeological challenges 173

3 Methods and Materials The Quaternary stratigraphy in the Cyclades shelf has been investigated on the basis of acoustic methods. High-resolution seismic reflection profiles have been obtained from Cyclades Plateau by the research vessel AEGAEO, using a single-channel airgun with air chambers of 10 and 40 in3, and an 8-hydrophone SIG streamer. Moreover, a detailed bathymetric map of the study area has been produced by: (a) numerous bathymetric tracks recorded by a narrow beam (8o) echo sounder (FURUNO) during the cruises of the research vessel AEGAEO; and (b) the digitisation of six nautical charts of the Hellenic Navy Hydrographic Service, which display various parts of the central Aegean Sea: (i) Saronikos Gulf (Ref. No: 413, scale 1:100 000, publ.: 1992), (ii) I. to Monemvasia (Ref. No: 414, scale 1:100 000, publ.: 1997), (iii) YdraI. to I. (Ref. No: 415, scale 1:150 000, publ.: 1997), (iv) Petalioi Gulf to I. (Ref. No: 421, scale 1:150 000, publ.: 2005), (v) Naxos I. to I. and Opposite Coasts of Asia Minor (Ref. No: 422, scale 1:150 000, publ.: 2005), and (vi) I. to I. (Ref. No: 423, scale 1:150 000, publ.: 2006). These bathymetric data sets have been interpolated on a high-resolution grid, i.e. 20 m. Considering present study's new data, the palaeogeographical maps of Cyclades Plateau published by Lambeck (1996) have been refined, showing in a more detailed way the palaeo- shoreline displacements (during shorter time intervals than those of Lambeck's study) due to the relative sea level rise since the Last Glacial Maximum (LGM). Furthermore, a distribution of the slopes in the Cyclades Plateau is presented. In addition, information about the human prehistory in the Cycladic region has been combined with the various shoreline displacements (during the last 20,000 years) in order to improve our understandingeschweizerbartxxx author for the prehistoric people adaptation to landscape changes. Table 1 presents a comprehensive review of the geological and archaeological terminology/chronology for the Cyclades region in order to emphasise the close relation between environmental changes and human occupation.

4 Geomorphologic changes and human occupation 4.1 From Middle to Upper Palaeolithic In the northwestern part of Cyclades shelf, near Keos Island (Fig. 2), the recorded seismic reflec- tion profiles show a number of Depositional Sequences (DS) with the uppermost sequence (DS1) representing presumably the last lowstand delta progradation during the oxygen isotopic stage 2. Two delta wedges occur in the outer shelf; where the transitions between the forset and topset (inflection points) facies are located in water depths of about 134 m (inflection point of 0.179 s) and 122 m (inflection point of 0.162 s). The deeper wedge was probably formed at a time the sea level had reached its lowest position (ca. 20,000 B.P.) while the shallower wedge, since it is a later sedimentary unit, might be formed during a stillstand phase of the last sea transgression.The base reflector of DS1 corresponds to an erosion surface truncated by subaerial and fluvial processes. The lower DS2 consists of sub-parallel reflectors, which follow seawards a divergent configura- tion. DS2 may represent distal prodelta deposits created during the oxygen isotopic stage 5. The above assumption is derived by the stratigraphic correlation of DS2 with the corresponding seis- mic units in the Gulf of Argos (Van Andel et al. 1990). Below DS2, a sequence of superimposed 174 V. Kapsimalis et al.

Table 1. Correlation of geological with archaeological terminology/chronology for the Cyclades region. Oxygen Isoropic Stages are displayed according to Shackleton (1987).

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eschweizerbartxxx author Fig. 2. Airgun seismicInflection Points profile (IP). from North Keos to the North Makronissos, showing various Depositional Sequences (DS), Delta Wedges (DW) and 176 V. Kapsimalis et al. prograding oblique sediment wedges appears. The thickness of DS3 is about 75 m whilst its inflection point ranges from 0.222 (depth of 167 m) to 0.245 s (depth of 184 m). Similar lithoseis- mic formations have been detected in many parts of the Aegean margin and may be interpreted as Lowstand System Tracks (LST) of the Upper Pleistocene Age (Lykousis 2009). In particular, comparing the depths of the inflection points of analogue prograding deltaic sequences in the eastern Cyclades Plateau (Lykousis et al. 1995), it may be assumed that the formation of DS3 is related to oxygen isotopic stage 6 (ca. 146 kyrs B.P.). The estimated subsidence rate from isotopic stage 6 to isotopic stage 2 varies from 0.26 to 0.40 m/kyr, i.e. subsidence of 33 to 50 m for a period of 126,000 years. The seismic profiles for the western part of the Andros Island (Fig. 3) demonstrate a narrow continental shelf affected by tectonism, with its width being less than 2 km in some locations. The present day shelf-break is situated in water depths of about 133 m (inflection at 0.177 s) with its substratum consisted of a series of Quaternary Depositional Sequences. The uppermost DS1 represents probably distal prodelta sediments coming from an adjacent delta wedge. The inflection point of this delta wedge is defined at a water depth of about 114 m in the outer shelf (inflection at 0.152 s). This delta wedge is covered by a truncated surface and it may be associated with a stillstand stage of the sea level rise during the last transgression. DS2 represents a Transgressive System Track (TST) including various depositional units, such as beach^shoreface complexes (BSC), incised-channel fills (ICF) and transgressive distal prodeltas (TDP). The formation of DS2 probably has taken place just after the oxygen isotopic stage 6, since its deepest erosion surface, which corresponds to the basement of a palaeo-channel, is located in a water depth of about 159 m

(inflection at 0.213 s). Similarly, DS3 and DS4eschweizerbartxxx author could be interpreted as aTSTof older eustatic cycles; probably associated with the oxygen isotopic stages 8 and 10. Finally, seismic profiling of the eastern margin of Island illustrates a series of stacked lowstand progradational units with the later units located farther landward (Fig. 4). According to the stratigraphic interpretation proposed by Piper &Perissoratis (2003) for a similar pat- tern to the south of Island, Depositional Sequences 1, 2, 3, 4 and 5 could be related with the oxygen isotopic stages 2, 6, 8, 10 and 12, respectively. This cross-sectional model is typical of rapidly subsiding shelves and provides a complete stratigraphic continuum for the last 500 kyrs. In conclusion, the Cyclades shelf has been evolved through various phases during Middle- Upper Pleistocene (ca. 500^20 kyrs B.P.). The relatively sea level variation is not the only reason affecting shelf geomorphology. Besides that, erosion and deposition processes may contribute considerably to the modification of the landscape. The Palaeolithic human settlements and activ- ities in the Cyclades region cannot be easily preserved in that continuously altered region since erosion and deposition activities can destroy and eliminate the majority of the evidence.

4.2 Uppermost Palaeolithic (ca.20,000^10,000 B.P.) During the LGM (ca. 20,000 B.P.), in accordance with the model developed by Lambeck & Purcell (2005), the sea level was occurring in depths ranging from 140 m in the southern part of Cylades Plateau to 135 m in its northern part. The area situated between Evvoia, Attica and Keos Island was partly exposed to subaerial conditions, while within its central part there were several Geoarchaeological challenges 177

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Fig. 3. Airgun seismic profile of the northwestern part of Andros Island, showing Depositional sequences (DS), Transgressive System Tracks (TST), Incised Channel Fills (ICF), Transgressive Distal Prodeltas (TDP) and Beach Shoreface Complexes (BSC). topographic depressions, characterized by depths higher than 135 m, which could have operated as palaeolakes (Fig. 5a). At that time, Cyclades Plateau was an emerged area of *10,400 km2 extending from Andros Island (to the north) to Island (to the south) over a distance of *200 km, and from Milos Island (to the southwest) to Amorgos Island (to the southeast) over a distance of *175 km. The main characteristic of this emerged Plateau was a single large island 178 V. Kapsimalis et al.

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Fig. 4. Airgun seismic profile of the eastern part of Kythnos Island, showing prograding Delta Wedges (DW) during sea level lowstands from the Middle Pleistocene (Oxygen Isotope Stage 12) to Uppermost Pleistocene (Oxygen Isotope Stage 2).

extending in an area of *7,600 km2.This mega-island'' was 160 km long and 90 km wide, with

its main axis directed from NNW to SSE. From that mega-island'' the presently existed islands of Andros, , Dilos, Despotikon, Donoussa, , , , , , Mykonos, Naxos, , Rhenia, , Sikinos, , Tinos and Yaros were created.

Among the aforementioned ' highlands' there were low-lying and relatively flat plains with an average slope of 1.58o. At the same period the shoreline was located very close to the present

shelf-break (Fig. 6.). In particular, there were two main plains in the mega-island'' region: (a) the central plain located between Syros-Dilos-Mykonos and Antiparos-Paros-Naxos highlands, char- acterized by a W to E direction and an average slope of 0.12o; and (b) the southern plain located Geoarchaeological challenges 179

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Fig. 5. Paleogeographic reconstruction of Cyclades Plateau, during: (A) 20,000 B.P.; (B) 18,000 B.P.; (C) 14,000 B.P.; (D) 12,000 B.P. between Antiparos-Paros-Naxos and Folegandros-Sikinos-Ios highlands, having a SW to NE direction and an average slope of 0.5o. Identified topographic depressions on these flat areas could operate as palaeolakes. These plains were regarded as the more suitable and productive habitats, with a lot of freshwater resources and ideal grounds for animal grazing. In spite of the fact that during this period the climate was cold and dry, milder conditions were prevailed in the

areas near the sea. To the west of the mega-island',' the islands of Kythnos, Serifos, , and Milos-- remained detached from each other as well as with Greek mainland. The distances among them were considerably smaller than these occurring today. For example,

the Milos-Kimolos-Polyaigos Island was separated from the mega-island'' and Peloponese by marine areas of *14 km and *85 km width, respectively. Finally, during the LGM the volcanic

island of Santorini was probably isolated from the Cycladic mega-island',' though its palaeomor- phology cannot be clearly determined due to the frequent volcano eruptions. 180 V. Kapsimalis et al.

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Fig. 5 (continued). Paleogeographic reconstruction of Cyclades Plateau, during: (E) 10,000 B.P.; (F) 8,000 B.P.; (G) 6,000 B.P.; and (H) 2,000 B.P.

Approximately 2,000 years after the LGM (ca. 18,000 B.P.), as the climate turned warmer and wetter, seawater progressively flooded Cyclades Plateau. The sea level was occurring in depths ranging from 126 m in the southern part of Cylades Plateau to 122 m in its northern part.

In this period the only modification was the detachment of Yaros Island from the mega-island'' (Fig. 5b). At ca. 14,000 B.P., the surface area of the Cyclades Plateau gradually diminished loosing approximately 20% of its initial extent (Fig. 7). However, the retreat of the palaeo-shoreline did not occur at the same rate everywhere (Van Andel &Shackleton 1982; Perissoratis & Conispoliatis 2003), with the loss of landmass being considerably greater in the areas of low- gradient (plains) than in the abrupt coastal sites. The central and northwestern flat fields (together with their associated palaeolakes) were flooded and retreated at a maximum horizontal rate of 10 m/yr and 3 m/yr, respectively. Moreover, Keos area was separated from South Evvoia and Greek mainland and was shaped into an island (Fig. 5c). Geoarchaeological challenges 181

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Fig. 6. Slope distribution (in degrees) of the Cyclades Plateau based on bathymetric data. Dashed line represents the paleo-shoreline of 20,000 B.P.

Since ca. 14,000 B.P. the sea level rise became more rapid and at ca. 12,000 B.P. it had reached

82 m below its present day position. This event was the reason for which mega-island'' was divided into two sectors (northern and southern), extending into a total land area of *3600 km2, i.e. land loss of *45% (Fig. 7). The northern sector consisted mainly of Andros-Tinos, Syros and Mykonos- Dilos islands, whilst the southern sector comprised Antiparos-Paros-Naxos, Sikinos-Folegandros and Ios islands. The distance between these two sectors reached *20 km with the average water depth being *12 m. Donoussa area to the east of Antiparos-Paros-Naxos Island became, finally

an island too (Fig. 5d). From ca 12,000 to 10,000 B.P. both sectors of the mega-island'' were subjected to further reduction of their size (land loss of *60%, Fig. 7), with sea water surface reaching a level of 54 m below its present position. Concerning the human presence during Uppermost Palaeolithic in Cyclades region, several archaeological finds provide strong evidence about that. Sampson (2006) argues that on Naxos Island exists an archaeological site (Stelida) where pre-Mesolithic artefacts, such as blades, retouched 182 V. Kapsimalis et al.

Fig. 7. Emerged surface area (in km2) of Cyclades Plateau since the LGM. Solid line represents the exposed surface' area of the shelf in Cyclades Plateau, while dashed line represents the exposed surface area of the mega-island'. eschweizerbartxxx author flakes and cores, have been identified. In addition, finds of Milian obsidian stone, from Late Palaeolithic strata, in the Franchthi Cave in southern Peloponese (Perle© s 1987), reveal that pre- historic people were able for a two-way crossing with small sea-crafts (Renfrew 1991). This is in agreement with Cherry (1985) and Torrence (1986) studies which argue that the location of the obsidian stone sources in Milos Island had been discovered by mainland-based groups of hunters after an extensive exploration by them of the Cyclades archipelago.

4.3 Mesolithic From ca. 10,000 to 8,000 B.P. the sea water surface was rising at an average rate of about

15^20 mm/yr reaching a level of about 30 m below its present position, while the mega-island'' continued disintegrating and the morphology of the area started to have a rough resemblance with the present status (Fig. 5e, f). To the north, the separation of Andros-Tenos Island from Dilos-Mykonos and Syros islands was more apparent, whilst later on, Dilos and Mykonos became individual islands. To the south, the distance between Antiparos-Paros-Naxos and Ios islands became larger, whilst Folegandros Island detached from Sikinos Island. Finally, the areas of Kimolos and Milos remain merged whilst Naxos, Irakleia, Schoinoussa and Keros areas become autonomous islands. Geoarchaeological challenges 183

The first permanent establishments dated from the Middle Stone Age, in the area of Aegean Sea, have been detected in Maroulas site on Kythnos Island. Sampson et al. (2002) brought to light many significant findings, like open-air burial grounds and relicts (paved floors) of Meso-

lithic ' houses', which are the earliest known archaeological remains in the Aegean Sea area. In addition, an examination of food remains suggested that the inhabitants of that area practised fishing, marine shell collecting and hunting of small-sized animals and birds. Further, the dis- covery of a plethora of finds made from Milian obsidian stone (small-sized blades, scrapers, spatulae, etc.) indicates that Kythnos Island inhabitants had a convenient access to Milos Island. This evidence points out also that Kythnos Island was a significant station in the sea course, which had connected Milos Island with the Greek mainland (Attica).

4.4 Neolithic From ca. 8,000 to 6,000 B.P. the sea water surface had reached to a level of 6 m lower than the pre- sent one. During that time span Milos-Kimolos-Polyaigos area was divided into the present islands (Fig. 5f, g). From ca. 6,000 to 2,000 B.P., sea level rose at a average rate of *1 mm/yr reaching -1.5 m below its present position. This value has also been estimated by Poulos et al. (in press) who have analyzed data from various submerged archaeological sites located in central Aegean Sea. However, Fouache et al. (2005) who have dated beach rocks from Mykonos, and Rhenia islands, have suggested a sea level lowering of 2.5 m below its present position, at ca. 2,500 B.P. No significant geomorphologic changes have taken place in the Plateau region during eschweizerbartxxx author that period (Fig. 5h). The total surface area of the residual islands, belonging to the original `mega-island,' has decreased in an extent of about 1,700 km2 (Fig. 7), i.e. approximately 4.5 times smaller than the initial size of the area. Human occurrence and the relative geoarchaeological information during that period in the Cyclades region concerning the areas of Sikinos, Antiparos (), Mykonos (Ftelia), Paros (Koukounaries), Keos (kefala) and Andros (Strofilas) are described briefly bellow:

Sikinos Island Recently, near to a cape in the southern part of this small Cycladic island, prehistoric architecture remains dated from the Early Neolithic period have been found (Sampson 2006). It is impressive also the discovery of a lot of well designed tools made of obsidian stone (e.g. sickle blades). The fact that this Neolithic settlement appears to be isolated from the rest of the island area raises interesting questions about the need of its existence.

Saliagos Islet It is located between Paros and Antiparos Islands with its horizontal dimensions being 100 and 50 m and its highest altitude being 5 m. This islet hosts an archaeological site occupied by Neo- lithic people from ca. 6,300 to 5,700 B.P. During this period, the sea level had reached at least 6 m below its present position with Antiparos and Paros areas being still connected and Saliagos rock 184 V. Kapsimalis et al. constituting the crest of this emerged peninsula. The discovery of plenty of fish-, sheep-, goat-, cattle- and pig-bones together with plant remains is a strong indication of human farming activity. Also remarkable finds may be considered the various pottery items, marble figurines and tools made from chipped obsidian stone.

Ftelia site on Mykonos Island The Neolithic settlement of Ftelia site is located on a hill in the northern part of Mykonos, cover- ing an area of 7,000^8,000 m2. The site comprises four structural levels dated from ca. 7,100 to 6,500 B.P. The most important of these establishments is a building, which resembles with a megaron, on the top of the hill, attributed to the earliest phase of the settlements. The discovery of great quantities of burned seeds of cereals and pulses on the floor of other smaller buildings in connection with the limited finds of shells and fish bones suggests that the Neolithic inhabitants of Ftelia site were involved more with land cultivation, animal husbandry and hunting than fishing. Moreover, it is impressive the discovery of numerous pottery fragments and obsidian tools char- acterised by excellent decoration and workmanship. Finally, copper material within the Neolithic layers of this site has been discovered.

Koukounaries site on Paros The Neolithic inhabitants were settled on the hill of Koukounaries (situated near the Bay of eschweizerbartxxx author Naousa in the northern part of Paros Island) around 6,500 B.P., and occupied the area until the Late Neolithic (ca. 5,000 B.P.). The selection of the site was certainly contingent upon its proxi- mity to the sea, the fertile land and the water resources of a nearby valley, the panoramic view, and the natural fortification of the hill. These establishments give the impression of rather poor constructions. However, this estimation may be false since post depositional activity should have severely affect the perishable material which had been used for the settlement building. Pottery and obsidian stones comprise the findings in the Neolithic layers, along with a few samples of shards and animal bones. The finds in the earlier Neolithic layers are reminiscent of the style found in the late settlements of Saliagos Islet, whilst finds in the later Neolithic layers manifest evidence of a transition which although transcends the limits set by other Neolithic settlements of Cyclades region (e.g. Kefala site on Keos Island), constitutes a step prior to the Early Bronze Age.

Kefala site on Keos Island This prehistoric site is of great importance since it hosts the largest discovered Neolithic grave- yard in the whole Cyclades area. The settlement, dated from ca. 6,300^5,300 B.P., is located near a rocky cape in the northern part of Keos Island. Besides the significant burial ground which has been preserved in a very good condition, limited remains from the other constructions of the settle- ment have been rescued due to the intense erosion activity. Finally, the discovery of copper material at Kefala site likewise with Ftelia area on Mykonos Island (see above) and the great similarities Geoarchaeological challenges 185 which have been traced between Kefala site and Evvoia region settlements offer a good evidence of the interrelations between the Cycladic islands and the metalliferous regions of Greek main- land.

Strofilas site on Andros Island The Strofilas settlement is situated in the area of Stavropeda to the west coast of Andros Island, occupying roughly 25,000^30,000 m2, and is dated from the Early Neolithic period (ca. 6,000 B.P.). This settlement, considering the standards of that era, could be described as a town since it is fortified, well built and very well preserved too. In general, the architecture of this town shows a particular social organisation with signs of early urbanisation. Refined artwork (e.g. pottery, jewels), useful domestic devices, stone tools and weapons equipped with obsidian stone pikes, as well as figurines and many objects made from copper constitute some of the important finds in this area.

5 Geoarchaeological challenges It is possible that Lower and Middle Palaeolithic humans could pass from Minor Asia to Greek mainland via the central Aegean landmass during sea level lowstand stages occurring in those epochs. However, due to subsidence and tectonic activities, this land bridge was partly sub- merged and separated from the neighbouring landmass (Lykousis 2009). Later on, in Upper eschweizerbartxxx author Palaeolithic, only a landmass characterised by a shallow shelf, was existed in the central area of

Aegean Sea, which had the shape of a single mega-island'.' Moreover, erosion and deposition activities had altered the morphology of Cyclades shelf. Within this variable coastal environment (alternating terrestrial with shallow marine phases), it was extremely difficult for Palaeolithic human remains and settlements to be maintained. It is possible that settlements and human remains have been destroyed by sub-aerial, fluvial or coastal erosion or have been buried under thick sediment deposits. Thus, the layers of Middle and Upper Palaeolithic in Cyclades Plateau cannot be considered as areas of high archaeological potential. During the Last Glacial Maximum (ca. 20,000 B.P.), where no significant deposition, tectonic and subsidence activity occurred, the Plateau offered the prehistoric people, through the emer- gence of extended flat fields, opportunities for animal hunting and exploitation of the abundant natural resources. It is documented that districts characterised by slopes lower than 10o could be considered as places convenient for occupation by prehistoric humans (Davidson 1988). There- fore, there is an increased probability for the low-lying areas (slope lower than 10o) of the Cyclades shelf to have been occupied in an extent of 98% of the total available area. Hence, Palaeolithic humans from the Greek mainland could migrate to the aforementioned flat fields (Runnels & Murray 2001). In these regions, climate conditions were milder than those prevailing in the mountainous hinterland supplying fertile land and suitable conditions for animal and plant survi- val. However, it should be emphasised the fact that this migration route had to overcome several difficulties raised by the sea environment. Kafireas Straits were the narrowest sea-passage between the Greek mainland and the Cyclades landmass and situated to the north of Andros Island. It was 186 V. Kapsimalis et al. a relatively deep (*300 m) channel with a minimum width of about 6 km. The strong currents (Pehlivanoglou 2001) which had been developed within the straits and the hard effort in approaching the rocky coasts of Andros Island were probably the major problems prehistoric sai- lors had to face during their long journey in that part of Aegean Sea. However, some particular sites along the insular palaeo-shoreline offered protection from the bad weather (temporary anchorage), food and water supply and a few days of rest during the long and exhausting trips. The abundance of natural resources and the adequate knowledge of the morphology of the broader area were good motives for permanent occupation of Cyclades islands. This dense insu- lar network, which was characterised by inter-accessible and often inter-visible islands, provided good conditions for safe navigation and further opportunities for discovery of new land. More- over, the lack of significant tides (with their amplitude being <0.3 m) and of the subsequent tidal currents made the approach of several coasts very easy. However, although the permanent habitation of the coastal areas offered several advantages to the settlers, such as free access to the sea, a variety of natural environments, adequate food supply, this was not always without problems. The various natural disasters (e.g. earthquakes, tsunamis, storms, etc.) and the progressive rise of the sea level resulted in the abandonment of the settlements and the unceasing migration of prehistoric humans towards mountainous hinter- land. In spite of the fact that Cyclades Plateau itself is not characterised by frequent and intensive geotectonic events, its southern margin constitutes part of the active volcanic arc of the Aegean Sea, where intensive seismic and volcanic activities are present. These activities are so powerful which besides the Cyclades Plateau itself affect also the surrounding area. For example, the his- toric explosion of the volcano of Santorinieschweizerbartxxx authorIsland shocked the whole eastern Mediterranean Sea. In addition, the generation of earthquakes often is associated with large vertical tectonic move- ments which can result in the emergence or sinking of an area near the shoreline. Further, some- times, very strong earthquakes under the sea water may cause the generation of tsounamis. Many researchers have suggested that the Aegean Sea is an area with high potentiality for tsounamis generation (Papadopoulos &Chalkis 1984). There is the recent analogous in Amorgos Island where a wave of 20 m height caused huge catastrophes to the human constructions located in the coastal zone. The continuous rising of the sea level during the Mesolithic and early Neolithic periods had as a result the loss of vast areas of fertile plains and high percentage of the available natural resources and habitats. Consequently, the majority of human remains were disappeared or eroded by the floods. However, the existence of Milian obsidian in several archaeological sites of Mesolithic (e.g. Franchthi Cave and Kythnos Island) and Neolithic (e.g. Sikinos and Antiparos Islands) reveals the existence of at least two major two-way sea routes: (a) from Milos Island to Attica, through Kimolos, Sifnos, Kyhtnos and Keos islands; and (b) from Milos Island to South Evvoia, through Folegandros, Sikinos, Ios, Naxos, Paros, Antiparos, Dilos, Mykonos, Tinos and Andros islands. At that time when the sea level was ranging from 82 to 6 m below its present position (from ca. 12,000 to 6,000 B.P.) some places near the palaeo-shoreline were served as per- manent or transit stations affording protection and supplies. Thus, these shelters which nowadays are submerged probably constitute areas of great archaeological potential. In particular, such areas could be located around Milos-Kimolos-Polyaigos, Antiparos-Paros-Naxos-Keros-Koufonisia, Andros-Tinos and Rhenia-Delos-Mykonos insular complexes. That estimation is enhanced by the Geoarchaeological challenges 187

Fig. 8. Bar diagram of archaeological sites discovered on the Cyclades island during Palaeolithic to Geometric time (after Syriopoulos1994^1995).

eschweizerbartxxx author plethora of archaeological finds (of Mesolithic and Neolithic age) already discovered in Sikinos, Mykonos, Paros, Keos, Andros Islands, Saliagos Islet etc. (Fig. 8). There, settlements were prob- ably characterised by a well-organised social and economic life. Nevertheless, the inhabitants of these settlements did not only come from the Greek mainland but they could also have moved from the low-lying areas of the islands. Later on, the loss of extended low lying areas as well as the threat for a further rising of the sea level, perhaps, contributed to the abandonment of the residual islands and the discovery of safer places in the mainland (Runnels 1995). People who, finally, stayed in the residual islands created later the famous , which reached its peak period at the end of the Bronze Age. This particular Age was characterised by populous fortified settlements with obvious town planning, communal buildings and other works of public interest, specialization in labour, economic prosperity and accumulation of wealth (Renfrew 1991; Broodbank 2000). The larger islands in Cyclades Plateau constituted the centers of a pri- mary urbanization in Aegean Sea area.

7 Conclusions The Cyclades Plateau is a shallow (<250 m) submarine area which has been submerged and emerged during the Palaeolithic. During the LGM (ca. 20,000 B.P.), the Cyclades Plateau had been

exposed as an extended landmass comprising a single mega-island'and' a few other smaller islands and covering a total surface area of about 10,400 km2. Then, at the time of the last sea transgression, 188 V. Kapsimalis et al. the Plateau progressively flooded resulting in the disappearance of a significant land bridge for human migration. However, the finding of Milian obsidian in the Greek Mainland (Franchthi Cave) shows that navigation constituted one of the main human activities since the Mesolithic. When the sea level reached approximately its present position (ca. 6,000 B.P.), the Cyclades Plateau had already lost about the three-fourth of its initial surface land. At that time, the oldest known Neolithic settlements in the Cyclades area were appeared on Sikinos, Mykonos, Paros, Keos, Andros Islands and Saliagos Islet. These settlements were probably organised by human groups who moved to hinterland forced by the sea level rise event. The inundation of the Cycladic Plateau and the subsequent migration of humans to the highlands constituted one of the major events in the Greek prehistory. It seems that the Cyclades Plateau is an area of high archaeological interest and future under- water surveys could reveal many of the secrets related to Cycladic civilisation, which are now buried deep in the Aegean Sea bed.

Acknowledgements The authors wish to thank the captain (Mr. K. Chandras), officers and crew of the R/V AEGAEO for their significant assistance in the field work.

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Addresses of the authors: V. Kapsimalis, I. Panagiotopoulos, P. Drakopoulou, D. Sakelariou and C. Anagnostou, Hellenic Centre for Marine Research, Institute of Oceanography, 46.7 km Athens-Sounio Av., 190 13 Anavyssos, Greece K. Pavlopoulos and D. Vandarakis, Harokopio University, Department of Geography, 70 El. Venizelou Str, 15671 Athens, Greece