Journal of the Virtual Explorer

Greece has the longest coastline in the Mediterranean, consisting of 13,780 km and including 6,000 islands and islets that make up around half of the country’s coastline (ec.europa.eu/maritimeaffairs). It is thus obvious that a great component of geomorphological and geoarchaeological processes in the Greek territory has been critically influenced by sea-level fluctuations. The continental shelf of the Aegean is wide along the northern and eastern coasts, where large rivers from the Balkans and Asia Minor have formed broad alluvial plains with thick sedimentary sequences that make up a smooth morphology of low slope gradients (Perissoratis and Conispoliatis 2003). Those coastal alluvial plains extend seaward until water depths of about 120-140 m, where a distinct shelf-break occurs. In contrast, on the coastal zone of Western Greece, the eastern coast of Peloponnesus and the fringes of ca. 200 islands, the continental shelf is mostly narrow (<10 km) and rocky; in those cases the shelf break is largely controlled by major bounding faults and it occurs at depths of 130-150 m, beyond which very steep slopes (up to 1:20) lead into deep basins (Aksu et al. 1995). Overall, the Aegean region has been intensely fractured by tectonic movements, resembling now “a tectonic puzzle made up of relatively small pieces” (Muscle and Martin 1990: 276), with a complex topographical structure and an irregular bathymetry (Stanley and Perissoratis 1977). The fact that major archaeological sites occur at or near the current shoreline, along with the aforementioned intricate character of the coastal configuration, drew the attention of geoscientists and encouraged their involvement in archaeologically-oriented projects. At the same time, this interest was further enhanced by the realization that archaeological evidence (e.g. submerged archaeological sites) can be used as proxies for inferring vertical tectonic movements along coastlines (e.g. Flemming 1998; Pavlopoulos et al. 2012). Being subject to intense tectonic activity and sea-level oscillations, the coastal landscapes of Greece were all the more suitable for assessing the three main components, namely the eustatic, isostatic and tectonic contribution, which need to be corrected for in the construction and calibration of sea-level curves (e.g. Lambeck 1995). As a consequence of all the above, coastal geoarchaeology was the first research domain where geological methods were used in Greece for the resolving of archaeological research questions, and, to our knowledge, these were some of the very first geoarchaeological studies to appear on a global scale.

A number of important and pioneering publications appeared in the 1970s and 1980s, dealing with coastal change, shoreline stratigraphy, sea-level fluctuations and paleotopographic reconstructions – all of which were carried out with reference to the locations of archaeological sites, their palaeoenvironmental settings and the investigation of (past) coastal settlement patterns (Raphael 1973; Kraft and Aschenbrennen 1977; Kraft et al. 1975, 1977, 1980, 1987; van Andel et al. 1980; van Andel and Shackleton 1982; Shackleton et al. 1984; van Andel 1989). Those studies came as a result and in parallel to a renewed interest in Mediterranean shoreline/sea-level investigations, which was spurred by global advances in deep-sea research and chronometric dating techniques (Butzer 1983). The oxygen isotope record, as recovered by foraminifera analyses in deep-sea sediment cores, provides a history of global continental ice volume and hence of the glacio-eustatic component of sea-level change. Progress in this field revolutionized Quaternary geochronology (e.g. Fairbanks and Matthews 1978; Shackleton 1987) but also showed that, albeit more complete and of higher resolution, the marine record was no less complex than its terrestrial counterpart. Building upon this sort of previous works on marine research (e.g. Flemming 1968, 1978; van Andel and Lianos 1984); and along with a gradually-growing appreciation of the role of paleogeography on archaeological interpretations (e.g. with regard to colonization processes and maritime/insular occupational patterns; Cherry 1981), those studies refreshed the research agenda of geoarchaeology and further promoted interdisciplinarity in research designs.

It is in this historical context that in the early 1970s J.Kraft, S. Aschenbrennen and G. Rapp began their work on the subsurface geology of some major embayments in Peloponnesus (Kraft et al. 1975, 1977; Kraft and Aschenbrennen 1977). Using a combination of drill core data, radiocarbon dating, geomorphological indicators and archaeological evidence, Kraft and colleagues (1977) were able to reconstruct the paleogeographic coastal settings of important archaeological sites and presented a relative sea-level curve for the Peloponnesian embayments. They created Neolithic to Bronze Age paleogeographic maps for the landscapes of the Argolid and Helos plains, and showed that ancient Tiryns was in Mycenaean times much closer to the shoreline, thereby supporting the view that Tiryns might have served as a port. This work (ibid), virtuously published in the journal Science, prefaced subsequent research on the role of alluvial infilling and/or marine regressions/transgressions in altering the paleotopography of archaeological sites (e.g. Zangger 1991; Maroukian et al. 2004). A few years later, the same team published a similar study on coastal change, this time presenting a paleogeomorphic reconstruction of the Navarino Bay and its surrounding area, where a number of important Bronze Age sites are located, including the late Helladic complex identified as the palace of Nestor, as well as sites of the Classical, Hellenistic and Roman times (Kraft et al. 1980). In another important research, Kraft and his associates (1987) reconstructed the physiography of Thermopylae, where the famous battle between the Greeks and the Persians took place in 480 BC. By use of geological and geomorphic investigations that included also extensive drilling, they estimated a 15-km shoreline progradation for the last 4500 years and showed that, due to widespread alluviation, the site of the battlefield is now buried by up to 20 m of sediment; in addition, this study raised the issue of the relative importance of the ‘pass’ at Thermopylae, in showing that the pass was closed for great portions of the last five thousand years and, when open, was frequently very narrow and marshy.

In generally the same period, i.e. from the late 1960s-beginning of 1970s and up to the late 1980s, archaeological investigations in the Argolid (Peloponnesus) undertaken by the universities of Indiana, Pennsylvania and Stanford, brought together a remarkable number of important archaeologists and geoscientists, now renowned as leading experts in geoarchaeological applications (to name but a few: T. Jacobsen, M. Jameson, C. Renfrew, C. Runnels, N. Shackleton, J. Shackleton, W. Farrand, T. van Andel and J. Hansen). Central to this ‘joining of forces’ was the excavation of Franchthi Cave, a site of world-wide significance that preserves an almost continuous habitation for more than 20,000 years, from the Upper Palaeolithic through the Mesolithic and up to the end of the Neolithic period (Jacobsen 1981; Douka et al. 2011 and references therein). Shackleton and van Andel (1980, 1986) and van Andel and co-workers (1980) examined the shell assemblages from Franchthi and the evolution of the coastal environment near the cave after the post-glacial rise of the sea level, and demonstrated how the gradual change of the topography might have influenced the subsistence strategies and occupational choices of the cave’s inhabitants. A couple of years later, van Andel and Shackleton (1982) were the first to publish a reconstruction of the late Palaeolithic and Mesolithic paleogeography of Greece and the Aegean, elaborating on the archaeological implications with regard to coastal plain recourses and migration routes. Notably, they were also the first to provide a quantitative and qualitative account of the estimated loss of coastal zone due to the rising sea level in a given area of Greece (in their example, the southeast Argolid). Such accounts and their accompanied maps provide a means of envisaging how much of the (potential) archaeological record lies submerged since the post-glacial marine inundation: for instance, the coastal land exposed in Greece during the Last Glacial Maximum (sea level lowered at -100 to -120 m) would correspond to more than a third of Greece’s current continental extent (Table 1). In archaeological terms, these spatially extended, most likely well-watered and biologically productive coastal plains (cf. Tourloukis 2010) may have supported food acquisition and resource procurement strategies that are not reflected in the sites preserved inland and on the present shorelines (van Andel and Shackleton 1982). In addition, the landmasses that would emerge during sea level low-stands could have served as landbridges and migration pathways for animal and human population movements (cf. Cherry 1981; Shackleton et al. 1984; van Andel 1989; Tourloukis and Karkanas 2012; see also below). Therefore, the decline or total loss of these resources needs to be seriously considered when explaining site- or regional-specific archaeological patterns.

Overall, those studies served as the point of departure –as well as a point of reference– for a long-lasting research tradition on the effects of coastal dynamics upon past human behavior and the role of paleogeography in the preservation and detectability of archaeological sites. If not directly integrated, they were at least highly influential to the first intensive archaeological surveys in Greece, which had a regional focus and explicitly sought to understand settlement patterns in conjunction to landscape evolution; this was, for instance, the case with the Minnesota Messenia Expedition (McDonald and Rapp 1972), the Argolid Exploration / Southern Argolid survey project(s) (e.g. Jameson et al. 1994) or the Pylos Regional Archaeological Project (e.g. Zangger et al. 1997). The aforementioned works by J. Kraft and colleagues, or T. van Andel and his associates, did not simply provide palaeogeographic contexts for the archaeologists to use in their explanatory narratives; they were also pivotal for the designing and execution of survey projects that subsequently discovered new sites, as well as for excavations –such as that of Franchthi– that established state-of-the-art standards in multidisciplinary research. Moreover, they can be deemed as pioneering not only for their conceptual contributions, i.e. as regards the way in which an archaeological inquiry can be approached, but also for the methodological advances that they promoted. For example, van Andel and Lianos (1983, 1984) were able to pinpoint the sea-level position of the last glacial maximum on the self of the southern Argolid by using high-resolution seismic profiler records; this investigation offered the first ‘direct’ evidence for the identification and reconstruction of submerged paleosurfaces in the Aegean, foreshadowing the importance of seismic reflection profiling as a powerful tool in marine geology.