Archaeology and Sea-Level Change

A Archaeology and Sea-Level Change Niki Evelpidou and Anna Karkani Faculty of Geology and Geoenvironment, National and Kapodistrian University of Athens, Athens, Greece Definition The archaeological remains that can be used, better together with biological, geomorphological, or other sea-level indicators, in order to obtain accurate information regarding their relationship with sea level during the period they were functional may be called archaeological sea-level indicators. Introduction The primary publications regarding the assessment of sealevel changes through the interpretation of archaeological indicators came from Flemming (1969), Caputo and Pieri (1976), and Pirazzoli (1976). Despite the large number of important archaeological remains, only a small percentage can be used in order to obtain accurate information regarding their relationship with sea level during the period they were functional. The constraints arising result from their uncertain use and lack of preservation. Two general types may provide evidence for past sea levels. The first refers to those constructions that were probably terrestrial or unrelated to sea level, but today are submerged, and the second to coastal remains that were constructed taking into account the sea-level of that specific time period. The sunken paintings of Cave Cosquer (France) belong to the first category and provide the earliest known archaeological remains, which are associated with the changing sea level in the Mediterranean (Lambeck and Bard 2000). Such findings can only provide a constraint on sea # Springer International Publishing AG, part of Springer Nature 2018 C. W. Finkl, C. Makowski (eds.), Encyclopedia of Coastal Science, https://doi.org/10.1007/978-3-319-48657-4_384-1 level and they are generally considered as indicators of low accuracy. The second category is especially valuable and includes shipbuilding berths, fish tanks, jetties, and harbors, which were mainly built after 2500 BC (Flemming 1978). These types of remains are usually directly related to sea level and they are able to provide accurate data for relative sea level (RSL) reconstructions. Some studies have used more indirect indicators, such as wells (e.g., Sivan et al. 2004, Caesarea, Israel), and churches’ floors, in order to reconstruct the changes of the water table in coastal areas. The ancient habitation in the Mediterranean has left a rich archive along its coasts, and it is clear that some archaeological structures provide interesting data regarding the size of relative sea-level changes since antiquity. During the last century, a large number of authors have explored the use of archaeological indicators in the study of relative sea-level changes (e.g., Flemming 1969; Pirazzoli 1976; Blackman 1973; Galili et al. 1988, Morhange et al. 2013; Sivan et al. 2004; Lambeck et al. 2004; Auriemma and Solinas 2009; Evelpidou et al. 2012; Kazmer et al. 2016, among others). The archaeological evidence associated with sea-level changes is rich globally, including the Atlantic Europe, the Mediterranean and the Near East, India, and China. According to Morhange and Marriner (2015), archaeological indicators are usually inadequate in determining relative sea-level changes; however, when they are combined with fixed bio-indicators, their value can be significantly increased (Fig. 1). The analysis of both port facilities and biological organisms, found on coastal constructions, has been long recognized as a possible source of information on sea-level data (Laborel and Laborel-Deguen 1994), such as the Roman columns in the market of Pozzuoli in southern Italy. Where it was possible to establish accurate vertical correlation between the archaeological construction and the biological sea level, the relative sea-level trends were accurately 2 Archaeology and Sea-Level Change Archaeology and Sea-Level Change, Fig. 1 The combination of archaeological and biological indicators has raised light to the palaeogeography of Lechaion area (Morhange et al. 2012) reconstructed since antiquity, in some Mediterranean locations (Morhange and Marriner 2015). By transferring the techniques developed on rocky shores (Laborel and Laborel-Deguen 1994) in ancient harbors, it is possible to accurately calculate the paleo-sea level (Fig. 1). Biological remains have enabled the use of radiocarbon dating and, also, the biological zonation of specific species (e.g., the upper limit of the populations of Balanus spp., L. lithophaga, Vermetus triqueter, Chama griphoides) is empirical and associated with the biological mean sea level (Laborel and Laborel-Deguen 1994; Morhange and Marriner 2015). Measuring the highest altitude variation between fossilized and modern populations, vertical error limits of 5 cm can be taken into account. Tectonic uplift (e.g., the port of Falasarna in Western Crete, around 365 BC) and silting of sedimentary basins, as in ancient harbors, contribute to the preservation of marine organisms in archaeological remains and in their use, afterward, as sea-level index points. The accuracy of the measurements depends on the determination of a reliable reference point (e.g., current biological sea level). Recent archaeological studies, which combine bioindicators and archaeological findings, allowed the progress in the measurements of sea-level changes in various archaeological sites, such as Marseille and Frejus in France; in Pozzuoli (Morhange et al. 2006), Italy; and in Vis, Croatia. Multiproxy approaches combining archaeological, biological, geomorphological, and geological sea-level indicators allow for more precise RSL reconstructions. Functional Heights and Other Considerations Auriemma and Solinas (2009) presented a very interesting review regarding archaeological sea-level indicators. Many different archaeological constructions, which were initially above sea level or in contact with sea water, are today submerged, thus revealing a relative change between the sea level and the position of the construction. In the Eastern Mediterranean, coastal and submerged archaeological remains are widely used as indicators of Holocene relative sea level (RSL). Sea-level indicators include fishponds (e.g., Auriemma and Solinas 2009; Evelpidou et al. 2012), harbor infrastructure such as quays, submerged settlements, coastal wells (e.g., Sivan et al. 2004), or any other datable remains, where a functional height can be determined. According to Morhange and Marriner (2015), the functional height is defined as the “elevation of specific architectural parts with respect to an averaged sea-level position at the time of their construction.” The functional use of an archaeological construction is determined by specific parts of it, taking into account the local mean sea level and depends on the type of the construction, its use, and the local tidal amplitudes. Jetty surfaces, for example, can be estimated at an elevation of at least 1 m above sea level, the bollards of the ships at 0.7–1 m and up to 2 m for large harbors, depending on the size of the ship. Slipways, which exist in many areas of the Mediterranean, such as Sicily, Cyprus, and Turkey, need to have enough length, so that the ship can be plucked out of the water and, also, enough water depth at their base, for the ship to get into the water (Blackman 1973). Archaeology and Sea-Level Change The concept of functional height is analogous to the indicative meaning (Shennan et al. 2015). If the relationship between archaeological remains and sea level is clear, a sealevel index point can be produced, using the functional height to reconstruct the former sea level. In the case of an unclear relationship between the sea level and the archaeological remain, only an upper or lower constraint on sea level may be achieved. Also, a large number of archaeological sea-level data derive from older publications, and the assumptions used to determine functional elevations, age, and uncertainties are not always consistent. The functional heights set the minimum height of the construction over the highest local tide (Lambeck et al. 2004; Evelpidou et al. 2012). However, in practice, this is very difficult to achieve, as their functional heights and their corresponding errors are estimated on the basis of the current analogues, which are not always related to ancient constructions. Furthermore, there is a great variety of ancient coastal remains that have undergone significant erosion due to wave action. Errors of the order of tens of centimeters are often larger than the absolute measurement (Morhange and Marriner 2015). Several archaeological findings can be used to reconstruct sea-level changes, but with variable accuracy. In order for these indicators to be used, the archaeological interpretation must ensure the coastal function of the construction and clarify its typology. Further estimates include building technics, which are important elements for age estimations and functional elevations (Auriemma and Solinas 2009). Therefore, it is very important to determine the age of the construction, the period of use, and the reason of abandonment or destruction (Marriner and Morhange 2006). This evidence can be determined through archaeological excavations in the study area and geoarchaeological investigations. Emphasis should be given on multidisciplinary work, in order to determine the accurate functional height, related to the present sea level and a strict chronological framework, using ages based both on pottery and archaeological constructions (Morhange and Marriner 2015). Ponds, Fish Tanks Artificial Roman fish tanks were structures that provided a suitable environment for fishes. There are numerous references to Roman fish tanks in Italy, where the largest number of the best preserved remains exists until nowadays. Along the Mediterranean coast at least 80 fish tanks have been recorded. Fish tanks have been widely used for the reconstruction of sea-level changes (e.g., Pirazzoli 1976; Lambeck et al. 2004; Evelpidou et al. 2012, among many others). They are primarily found along the western peninsula of Italy, while 3 fewer examples may be found in the Adriatic Sea, in North Africa, Spain, Greece, and Israel. The Roman fish tanks have structural components that are directly connected with sea level at the time of their construction. Their construction and use are well documented by authors such as Pliny, Marcus Terentius Varro, and Columella. The latter one described the use of the tank as a means of storing the fish, intended for cultivation. Fish tanks may provide information on past sea levels, but it is important to clarify the function of the individual characteristics and estimate the functional height in relation to sea level. Latin writer Columella, in the first century AD, distinguished three types of fish tanks, with variable depth. Depending on the type, the functional heights of their morphological features can be calculated, according to the sea level. Specifically, the fish tanks that had been opened on rocky platforms had a depth of about 9 ft (2.745 m) (Columella, De Re Rustica, XVII). These structures, often consisting of a few built walls and including channels, started from the outer limit of the platform and had a depth of 2 ft (0.61 m) near the fish tank. Some examples of this type are the fish tanks of Torre Valdaliga and Mattonara in Italy (Fig. 2). The fish tanks that were built entirely on the coast had a 7-ft depth (2.135 m). Examples of this type are Piscina di Lucullo, Punta della Vipera, Formia, T. Astura, La Banca, and Fosso Guardiole Saracca (A), also in Italy. Finally, the third type was similar to the previous one, but it had a depth of only 2 ft (0.61 m), because it was intended for flat fish, such as soles. An example of this type is a small arched fish tank in Fosso Guardiole (B) in Italy. Architectural Characteristics The foot walks are narrow paths along the inner tanks. Initially, they were used for maintenance purposes and therefore they are considered to have been above mean sea level. In some cases, such as the fish tank of Lucullus (Circeo National Park, Italy), lower foot walks were built beneath the openings for the water’s entrance (Pirazzoli 1976). The measurement of the foot walk position in relation to sea level provides some evidence for the range of RSL variation. The channels were used in order to fill and empty water from the basins using the local tide. They should, therefore, be studied and used carefully. The in situ mid-tidal gates (closing gates), which are precise indicators, are extremely rare, due to their original location in the surf zone. The metal grids (cataractae) along the channels or between the tanks were operating within opened grooves on the rocks. Cataractae were placed within the tidal range levels and consequently, their marks can be particularly useful, if interpreted correctly, for the estimation of the paleosea level. 4 Archaeology and Sea-Level Change Archaeology and Sea-Level Change, Fig. 2 Some archaeological remains, such as Roman fish tanks, have structural components that are directly connected with sea level at the time of their construction This type of indicator is quite complex, and different researchers (Lambeck et al. 2004; Evelpidou et al. 2012) have calculated different sea levels for the same fish tanks in Italy. When dating relies on indirect means such as pottery typology, outlier data points result. Channels and Quarries Rock-carved structures are defective. Quarries exist along many coastal areas in the Mediterranean and elsewhere, but in most cases direct dating is not possible (Fig. 3). According to Auriemma and Solinas (2009), the height of the mining surface of the blocks in coastal quarries brings a higher margin of error. For coastal quarries, which are now found at least partially submerged, the assumption that they were completely emerged in order to enable mining is considered (Auriemma and Solinas 2009). Morhange and Marriner (2015) suggest that this type of indicator can provide information only on the direction of sea-level change. Harbor Structures and Shipsheds Harbor structures refer to moles, quays, harbor towers, docks, shipsheds, etc. These structures are frequently problematic. It is difficult to decipher the function for many of these features since they frequently consist of rock mounds in the water; their state of preservation adds further uncertainties. If the preservation state is poor and eroded, reconstruction of past sea level is not possible. Even in the case of well-preserved and well-dated quay remains, a vertical uncertainty of 0.5 m is very common (Auriemma and Solinas 2009), since interpretations rely on assumptions regarding the draughts of ancient ships and unloading techniques. In such types of indicators only moderate accuracy may be achieved and only few provide upper constraints on sea level. Within harbors, rock-carved shipsheds, cannot be directly dated, so they can only be correlated with available nearby sea-level indicators (Fig. 4). However, this is also a difficult task, considering that such structures are sometimes incomplete, and their relationship to sea level depends on assumptions regarding ancient maritime technology. Building Foundations and Floor Surfaces The base level of many structures, including foundations and floor surfaces from roads, buildings, walls, etc. (e.g., Auriemma and Solinas 2009) is a common sea-level indicator. However, such archaeological remains can only give a maximum constraint for sea level (Fig. 5). Furthermore, their interpretation often relies on various speculations, e.g., how close they could be built above water (e.g., Morhange and Marriner 2015). Coastal Wells Coastal water wells have been very useful indicators of RSL in Israel due to a large, continuous dataset (e.g., Sivan et al. 2004). According to Sivan et al. (2004) and references within, the reconstruction of sea level is accomplished from the base Archaeology and Sea-Level Change 5 Archaeology and Sea-Level Change, Fig. 3 Direct dating of quarries is not possible; other nearby indicators may be used in combination Archaeology and Sea-Level Change, Fig. 4 Moles are frequently problematic since they consist of mounds of rocks in the water that raise many uncertainties related to their preservation level elevation of the well, plus 35 cm for a water drawing jar, minus the thickness of the freshwater table resting on the saltwater intrusion. Uncertainties in age estimation of wells may also arise; however, in the case of well-studied archaeological sites, such as Caesarea, domestic wells are part of well-understood and accurately dated context (Sivan et al. 2004). 6 Archaeology and Sea-Level Change Archaeology and Sea-Level Change, Fig. 5 Submerged buildings, roads, and similar structures may only provide a constraint on sea level and thus are considered as low accuracy indicators Summary Bibliography Archaeological remains may help in studying sea-level fluctuations since the prehistoric times. There are many different types of archaeological sea-level indicators with variable accuracy and precision. Among them, one of the most prominent are fish tanks, providing RSL data since the Roman times. Archaeological indicators alone are usually inadequate in determining relative sea-level changes with a high level of precision. However, multiproxy approaches, combining geomorphological, geological, or biological indicators, can allow not only to reliably reconstruct RSL changes but also coastal landscape evolution, providing archaeologists with valuable data related to former human occupation. Auriemma R, Solinas E (2009) Archaeological remains as sea level change markers: a review. Quat Int 206:134–146 Blackman DJ (1973) Evidence of sea level change in ancient harbors and coastal installations. In: Blackman DJ (ed) Marine archaeology. Colston papers, vol 23. Butterworth, London, pp 114–117 Caputo M, Pieri L (1976) Eustatic variation in the last 2000 years in the Mediterranean. J Geophys Res 81:5787–5790 Columella, De Re Rustica, XVII Evelpidou N, Pirazzoli P, Vassilopoulos A, Spada G, Ruggieri G, Tomasin A (2012) Late Holocene sea level reconstructions based on observations of Roman fish tanks, Tyrrhenian coast of Italy. 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