Some Critical and Methodological Aspects of ...

J Archaeol Method Theory DOI 10.1007/s10816-010-9084-x

Some Critical and Methodological Aspects of Shoreline Determination: Examples from the Baltic Sea Region Kristin Ilves & Kim Darmark

# Springer Science+Business Media, LLC 2010

Abstract Coastal shorelines worldwide are generally unstable and changing. The study of the precise relation between any archaeological site and the shoreline at the time when the site was used is therefore complicated, but still often not met with appropriate methodological approaches. In this article, we test models based on phosphate analysis and discuss how they can be used to detect ancient shorelines. We propose that a model of increased and oscillating phosphate values at the former water level is considered reliable and useful in areas with advancing shoreline. Keywords Coastal archaeology . Shore displacement . Baltic Sea region . Phosphate analysis

Background The authors of this article have both been dealing with the study of archaeological sites presumed to have been occupied by people heavily dependent on the sea. Ilves has focussed on the settlement pattern of coastal western Estonia during the late Iron Age (Ilves 2006a, 2006b), a period characterised by the sea as an increasingly important means of transportation in the Baltic Sea region, while Darmark has been involved in the excavation and publication of several Mesolithic and Neolithic settlements in eastern central Sweden (Darmark and Sundström 2005; Sundström and Darmark 2005; Sundström et al. 2006), which bear witness to a high dependency on marine resources. Thus, from different points of view, the authors have encountered the same problem: what was the relation between a given site and the shoreline at the time K. Ilves (*) Centre for Baltic and East European Studies, Södertörn University, 14189 Huddinge, Sweden e-mail: [email protected] K. Ilves : K. Darmark Department of Archaeology, Stockholm University, Stockholm, Sweden

Ilves and Darmark

when the site was used? This problem became especially obvious in the study of the Iron Age landing sites, where it is usually assumed that a location on the former coast combined with practically any traces of human activity automatically proves that a place has functioned as a landing site, especially if all the so-called cultural criteria used as a help for locating places for landing are fulfilled as well (see for example Carlsson 1991; Dobat 2002; Mägi 2004, 2006; Ulriksen 1992, 1998). In this case, the site is ascribed a very specific function, that of being a landing site, from purely circumstantial evidence. The Stone Age settlement system is subject to the same difficulties. The evidence for an economy based on marine resources is so strong that it tends to overshadow the possibility of the existence of sites not immediately positioned by the shore (cf. Björck 2003: pp. 18–20). None of the authors wishes to contest that the people of Iron Age Estonia or Stone Age Sweden, seen as cultural systems, were dependent on the sea. However, such contextual knowledge needs to be met with methodological approaches when dealing with empirical sources—otherwise, our story of the past becomes selffulfilling. Yes, we can assume that people who depend on fish also live by the shore, or that sea-faring people had places for landing. Showing this archaeologically and separating different activities from one another is another matter. The aim of this article is to explore how the relation between sites and ancient shores has been studied in archaeology and, more importantly, to try to create a frame of reference for the archaeological data by using an abandoned modern harbour site as an example. Shore Displacement and Shoreline Determination Change is a characteristic trait of all types of shore areas globally. Rivers have changed their courses, disappeared, entire lakes have dried up, canals have been dug to drain large territories, silting has aided land reclamation, etc. Most shorelines worldwide have advanced or retreated over time. A shoreline advances when the deposition of sediment exceeds the rate of erosion or due to the uplift of land or a drop in water level. The shoreline will retreat when erosion exceeds deposition, or when there is submergence due to land subsidence or a water level rise (Bird 2008: p. 9). Dramatic changes in coastal areas are caused by the effects of both regional and local factors such as drift of water and ice, high flood, non-frozen coastal sediments that enable erosion of the coasts during winter storms, changes caused by hydrodynamic conditions and the direct and/or indirect human affect (Orviku 1992: pp. 9–10). Obviously, visible coastline changes resulting from human activities comprise mostly reclamation, i.e. land claim; there are a number of examples of the creation of new ground by enclosing or filling nearshore areas; the Netherlands in particular has a long history of winning land from the sea, and densely populated coasts in southeast Asia have been subject to a continuous increase in land area. Global factors, such as the greenhouse effect causing more intensive cyclonic activity changing coasts, are also clearly apparent. The short-term visibility is somewhat feebler in case of the phenomenon called shore displacement. The shore displacement comprises both isostatic and eustatic changes (i.e. changes of the earth’s crust and the world sea, respectively) of the shoreline, which also results in transgressions and regressions of the water level.

Critical and Methodological Aspects of Shoreline Determination

The Baltic Sea area is one example of fluctuating shorelines, since it has been and is constantly influenced by shore displacement, which is a result of the Ice Age. The earth’s crust was pressed down by the ice and is striving to attain its former level. The deglaciation of the last ice sheet and the contemporaneous sea level as well as isobases for recent movements in the earth’s crust in the land uplift area of Fennoscandia and the Baltic and related sea level changes are known fairly exactly (see Ekman 1993, 2001; Eronen 1974: p. 94; 1987; Møller 1989, 2003; Ristaniemi et al. 1997; Saarse et al. 2005). On this basis, the reconstructions of the shorelines at different times can be generated. For example, if the rate of shore displacement in Estonia is known to be 3 mm per year, the Estonian Middle Neolithic (4200/4000– 3200/3000 BC) (Lang and Kriiska 2001: pp. 90–92) shoreline could be calculated to be between 19 and 15 m above the present sea level, while the Viking Age (800– 1050 AD) shoreline is generally calculated to be 4–3 m above the present sea level. In areas of flat terrain, this means that differences in shore level as small as 1 m result in huge landscape transformations. An integral part of this kind of shoreline development research is the study of archaeologically dated coastal sites (e.g. Eronen 1983; Harff et al. 2005; Jussila and Kriiska 2004; Meyer and Harff 2005; Møller 1987). The lower limit of the archaeological finds of a given period is considered to correspond approximately to the sea level of that period1. The spatial relation between archaeological sites and shores is also similarly reconstructed in other areas besides the Baltic Sea where ancient shorelines are available for investigation in a modern-day terrestrial context. Indicative information is collected from isobases for recent movements in the earth’s crust and shoreline determination is done using dated coastal archaeological sites. For example, studies on archaeological and historical material in relation to fluctuating shorelines in the archipelago of Svalbard/Spitsbergen, in the Arctic Ocean, have been systematically carried out already from the 1950s (e.g. Blake 1961; Christiansson 1961; Lejoneke and Rönnby 2005). The interchangeable combination of archaeological and geological data is diligently used in North America—in Canada, where archaeological sites are routinely used as elevational or chronological datum levels (e.g. Andrews et al. 1971; Cannon 2000; Clark and Fitzhugh 1992; McGhee 1979), as well as in Southeast Alaska (e.g. Giddings and Anderson 1986; Mobley 1988). Also, in the European North, along the coast of northern Norway resembling studies have found a solid ground (e.g. Møller 1987, 2003). But the process of uplift has not been linear and steady. Isostatic movement varies between different places and the crust has moved irregularly. The centres of uplift have been shifting. Also, uplift is greatly influenced by the fluctuations of the sea level, and there has been a great deal of confusion of ideas and opinions about the transgressions. Besides, it is unknown to which extent the land uplift has slowed down since the last glaciation (Berglund 2005; Clague 1983; Eronen 1974: pp. 80–95; Lindén et al. 2006; Petersson 2006: pp. 34–35; Risberg et al. 2007: pp. 102–103). Archaeological data has been the main means of testing the calculated reconstructions of the shorelines at different times (e.g. Ambrosiani 1981), but in many cases 1

Within the limited coastal areas, the shoreline displacement is also calculated by counting of annual varves in ancient river deltas and lakes or by diatom, pollen and C-14 analysis (see for example in Königsson and Paabo 1981).

Ilves and Darmark

the archaeologists and geologists use each other’s material, which definitely magnifies the factor of uncertainty. Despite the factors which affect the uplift, the usual physical model used within archaeological practice to reconstruct the shorelines at different times assumes that the rates of shore displacement decrease evenly with time, even if stagnation and/or transgression phases are well acknowledged. In this way, a rough estimation of the ancient landscape is obtained, which definitely is very helpful in archaeological surveys. But it is not the same as precise information regarding the shoreline at a certain point in time, and without this knowledge it is difficult to discuss the relation of a specific archaeological site to the contemporary shoreline as it actually stays very hypothetical. To this should be added the uncertainty concerning radiocarbon dates, which can only give us an estimate of the age of occupation, often with a standard deviation of hundreds of years. A rough correlation between the dating of a group of sites and the dating of a particular shore level, even though it certainly indicates that the sea has been an important localising factor, can thus hardly be used as a way to establish the position of the shore at a particular site during its time of occupation. The Problem of Archaeological Landing Sites The discussion above has direct implications for the archaeological identification of landing sites. The archaeological definition of a landing place is heavily connected to a site’s position by the ancient shore, but since the shoreline is usually determined on the basis of shore displacement calculations, which, as argued above, does not give any accurate information about the shoreline at a certain point in time, there seems to be a problem. The potential landing places recorded within the project “Coastal Settlements on Prehistoric and Medieval Saaremaa” (carried out in 2003–2006) were found at sites visited after a survey of suitable locations along the reconstructed Iron Age shoreline on the island of Saaremaa, Estonia (Mägi 2004). The material traces at these sites consisted of darkened soil, occasionally containing some finds of potsherds, bones and charcoal (i.e. common Iron Age settlement finds). Apart from a rough association between the sites and a particular reconstructed shoreline, there are little data to determine the site’s character and function. Ascribing a specific function to these archaeological locations, in this case that of a landing site, based on the kind of generalising data that is available (shoreline displacement models and radiocarbon or relative datings) is futile. Not every coastal community living immediately by the water always “put water to use”—and the choice between using and not using the water is done deliberately, and it is not always caused by lack of knowledge or technology (see for example Jones 1975). Well-known examples of insular populations not exploiting their surrounding maritime resources include the Guanches of the Canary Islands, who did not know navigation skills (Crosby 2004: p. 80), and the people of the Easter Island, who subsisted mainly on farming regardless of the rich marine environment surrounding them (Diamond 2005: pp. 90f). The islanders of Pohnpei in Micronesia did not possess ocean-going sailing vessels and did not venture beyond the barrier reef that surrounded the island according to the earliest records made by European visitors, and there is no environmental reason why, at some time after colonising the


island, the Pohnpeians had to stop building large sea crafts (Rainbird 2007: pp. 102– 104). These ethnographic examples are not intended to point out the uniqueness of each particular historical context (cf. Hodder 1982), but rather to stress again the fact that it is difficult to make specific (contextual) interpretations in archaeology if specific data is not available. We know very little of what a prehistoric landing site looked like, what it was used for, what kinds of features can be associated with it or what kinds of objects could have been discarded at the site. There is not even enough evidence that the act of landing leaves traces in the material culture record. It is thus hard for us to create specific data covering these functional aspects of the sites and to separate the activity of landing from other activities (see Ilves 2006a). One thing we do know about them, however, is that they must have been situated right by the shore. Is it then possible for us to create specific data using this knowledge? Phosphate Mapping as a Means of Identifying Shorelines Phosphate mapping has a long history of being used to detect ancient shorelines in Fennoscandia, mainly in the study of the Stone Age (G. Arrhenius 1945; Broadbent 1979; Florin 1948; Halén 1994; Löfstrand 1974; Nunez 1977, 1978; Schnell 1932; Siiriäinen 1982; Simonsen and Lysnes 1968; Sundström and Darmark 2005; Sundström et al. 2006). Phosphates, which occur in all living organisms, are released during the decomposition of organic remains and are bound to particles of soil as iron, aluminium, copper or calcium phosphates; phosphates could also absorb to mineral particles in the soil. The phosphates, partly organic as well as inorganic, being withdrawn from the natural cycle, remain intact in the ground for millennia— no considerable leaching process is taking place (Bethell and Máté 1989: p. 9; Blidmo 1995: pp. 7–8; Österholm 1991: p. 269). There are different activities that create an increase in the phosphate content of the soil. The butchering and cleaning of game can leave organic matter, which increases phosphate content. Fish remains have been argued to leave a high contribution of phosphate; the gutting of fish can result in as much as one third of the weight being discarded (B. Arrhenius 1974). Human waste and urine is another source. Further human activities adding phosphorus to soils include burning organic materials (i.e. in hearths, kilns, etc.), the storage of organic material such as food as well as the processing of non-food organic materials such as wood or bone. There is even evidence pointing to the fact that areas where inorganic material (chipped stone tools etc.) has been processed will be characterised by increased phosphate content (Middleton 2004: pp. 53–54). Thus, there is testimony to the fact that a human activity area of almost any kind will leave a chemical trace in the ground. According to the early studies on the potential of phosphate analysis in the determination of the ancient shorelines, a site located directly by the shore would have sharply delineated phosphate values by the former water level as the chemical residues below the water level are washed away (see for example Florin 1948; Rausing 1963; Schnell 1932; Simonsen and Lysnes 1968). A site not located directly by the shore would show evenly decreasing amounts of residue towards its outer margins. More recent work done in the study of Mesolithic and Neolithic coastal sites in Middle and Northern Sweden has supplemented the model of sharply

Ilves and Darmark

delineated phosphate values by the former water level with additional observations. Several sites have yielded evidence of a pattern where the decrease in phosphate content towards the presumed shoreline is interrupted by a peak or several peaks between the settlement and a shoreline area (Broadbent 1979: pp. 28–29; Löfstrand 1974: pp. 98–101; Sundström et al. 2006: pp. 101–103). According to Löfstrand (1974), if these sites would not have had contact with water, the phosphate distribution would have decreased evenly (of which he has evidence, especially at the site Smällan; see Löfstrand 1974, fig. 94), but as the sites have been in contact with an annually fluctuating sea level, there are a number of variations in phosphate values at the lower levels of the sites—the oscillations of the phosphate values at the lower levels of the sites, along the shorelines contemporary with the sites, denote the sites’ dependence on alterations of the sea level and the beach (Fig. 1). Thus, the models of phosphate distribution in relation to shorelines are based on, firstly, the assumption that activities conducted in proximity to the water leave behind organic waste deposits, generating phosphates that are bound to soil particles. Secondly, that these deposits are affected by post-depositional processes, where the effect of water is the most significant. In one scenario, the water will transport phosphate-rich soil out into the sea, thus creating a marked drop in phosphate content, which contrasts with a normal distribution otherwise expected. In the second scenario, the fluctuating water level will transport phosphate-rich soil back and forth, creating an undulating pattern and an accumulation of phosphate-rich soil along the upper contact zone of water and land. Admittedly, it is in no way impossible to imagine processes creating similar patterns of phosphate distribution at sites not situated by the sea. For example, a landslide could create a marked drop in phosphate content, or cultural formation processes could create accumulations of

Fig. 1 Theoretical phosphate distribution models. Above: evenly decreasing amounts of phosphate residue at a site not located directly by the shore. Centre: sharply delineated phosphate values at a site located by the former water level. Below: accumulated and fluctuating phosphate values at a site located by the former water level


phosphate at the margin of activity areas. Identification of the actual processes responsible is to be judged by the researcher on a case-to-case basis. To summarise, in order to establish the position of the seashore at the time of a site’s occupation, at least two models based on phosphate analysis have been presented—(1) coastal sites would have sharply delineated phosphate values by the former water level and (2) coastal sites would have increased phosphate values at the water’s edge. These models have their roots already in the very first studies combining archaeology and phosphate analysis (e.g. O. Arrhenius 1931, 1935). Theoretically, one or both models could be useful in any case where humans have been present, leaving behind organic waste deposits by the regressing shoreline. Identification of these patterns at an archaeological site would give much more reasoned cause for estimations of where the old seashore was at the time of the occupation and, thus, for answering the question concerning the spatial relation to the shoreline. Therefore, focus in this article is laid on these models and these are specifically tested by analysing the phosphate values from a site known to have been situated on the verge of the sea, as well as used for maritime purposes, but not in use for the last 100 years—the nineteenth-century village harbour of Österby by the Baltic Sea coast in Estonia. The Case of Österby Österby is a small village in the former Estonian–Swedish habitation area and is located in Noarootsi parish, on the southern part of the Noarootsi peninsula by the Haapsalu bay in northwestern Estonia (Fig. 2). There are rarely any archaeological

Fig. 2 The Baltic Sea region and Estonia. Inset Noarootsi Peninsula, location of Österby and map of investigation area. Marked on the map are the Village of Österby, the Old and New harbour sites. For reference, the 3 ma.s.l., where the village is situated, is enhanced

Ilves and Darmark

field studies conducted in Noarootsi parish, excepting the village of Einbi and its surroundings on the Noarootsi peninsula, which have been archaeologically studied in order to discuss the questions of ethnicity and continuity of Swedes in Estonia (Markus 2004); some minor field surveys have also been conducted in the northern parts of Noarootsi parish (Ilves 2006b: p. 96). However, despite the unclear nature of the prehistoric settlement, the area’s general history is still considered closely connected with coastal development and shore displacement (Hoppe and Markus 2001). The area of Noarootsi parish shows the fastest rates of land mass upheaval on the Estonian mainland. The area’s rate of shore displacement has been calculated to be 2.8 mm per year on the peninsula and 2.9–3.1 mm per year on the northern mainland territories of the parish (Hoppe et al. 2002; Nõulik 2001: pp. 39–40). The modern, active harbour of Österby was founded in the years 1905–1906 when a 253-m-long granite stone jetty covered with gravel was built (The Estonian State Archives 982.1.15 page 13). Only 300 m east of it, the old, abandoned harbour of Österby is situated. It consists of the grass-covered remains of a granite stone jetty, which is approximately 110 m long and detectable in today’s landscape (Fig. 3). Reeds surround one third of this jetty; during months without lush vegetation, the jetty becomes almost invisible for the “untrained” eye—the reeds help to visualise the jetty. The jetty is situated on a flat coast with coastal gleysoils (www.maaamet.ee (map of soils) [15.02.2007]) in between 0 and 1 ma.s.l., and the outer end of the jetty is still situated in open shallow water. During its use, this harbour was situated ca. 2 km south of the actual village of Österby. The site was thus used solely as a landing site and for tasks associated with this function. The exact nature of these activities is not certain, but fishing should be considered. Beginning with the twentieth century, there was no real fishing practised anymore in any of the villages on the Noarootsi peninsula except Einbi, but prior to

Fig. 3 Österby old harbour site in the autumn of 2006. Photo by K. Ilves


the twentieth century fishing was of major importance in Österby. As the actual village is not situated right next to the sea, there must have been necessary arrangements, such as sheds, constructions for drying nets, etc. by the landing site (Stahl 1964: pp. 224, 228). However, no visible and unequivocally interpretable traces of such are possible to observe in the landscape today. The old harbour of Österby was tested for phosphates in a manner similar to the work done in the study of Stone Age coastal hunting and fishing sites, based most of all on the collecting techniques used at the Early Neolithic–Middle Neolithic seasonal Pitted Ware settlement sites in northern Uppland, Sweden (Sundström et al. 2006). Samples were collected at Österby along a line toward the shore area and water zone; test pits of 0.30×0.30 m were laid out at 1-m intervals along a 70-m-long, S–N directed line parallel to the stone jetty. The level ranges between approximately 0.2 and 1 ma.s.l. The phosphate sampling started 46 m from the outer end of the jetty, which at the same time roughly marked the beginning of the present shoreline. From every pit, one sample was collected while the soil for the sample was mixed from all four walls of the pit (cf. Sundström et al. 2006: pp. 35, 84). This was done in order to avoid extreme local fluctuations in phosphate value and instead obtain a local mean. Samples were uniformly taken ca. 15 cm below the surface, ca. 10 cm below the thin humus layer. The sample pits closest to the sea were without any detectable stratification; the grey-coloured soil was loamy, mixed with clay and sand. The bottoms of the sample pits were quickly covered with water until the sampling was 18 m from its southern end. In addition, 18 m from the seaside start of the sampling stratification occurred in the pits, darker layer(s) of soil in between grey-coloured soil became especially obvious from the 24th metre and continued up to the 34th metre (Fig. 4). However, no finds or other special characteristics were noted. From the 35th metre, the soil turned back to grey, loamy, mixed with clay and sand, but after some additional 10 m the layer of darker coloured soil occurred again and was continuous to about the 58th metre from the start of the sampling. From that point to the end of the sampling line, the soil in the sample pits turned relatively abruptly to yellow sandygravely and was very difficult to sample. The analysis of the soil samples was done in steps, starting by analysing every tenth sample2 in order to evaluate whether there was a potential for the use of the phosphate content as a methodological tool at all. The first eight analysed samples covering the whole 70-m-long line of sampling showed values from the 55 to 197 mg P2O5 per 1,000 g dry soil. The phosphate content, according to these first analysed samples, had a general correlation with the different characteristics of soil at the site—where there was a darker layer the phosphate content was higher. But the most interesting factor for the present study was the steep rise of the phosphate content curve close to the present shoreline; the decrease in phosphate content towards the shoreline was interrupted by a significant rise at the water edge (Fig. 5). The rise in the phosphate content curve close to the water seems to corroborate the patterns obtained in the archaeological studies, i.e. the tendency for phosphate-generating matter to accumulate at the water edge. 2

Phosphate determination of the first, 70-m-long line of samples was done by Elna Haiba in the laboratory of the Institute of History, Tallinn University, by the citric acid method determining milligrams of P2O5 per 1,000 g dry soil (financed by the Estonian Science Foundation Grant No. 6998).

Ilves and Darmark

Fig. 4 Phosphate sample pit with two darker layers of soil in between grey-coloured soil. Photo by K. Ilves

These results motivated an analysis of more samples. Special attention was directed towards the lower end of the line, to the presumed water fluctuation zone contemporary with the harbour’s use. In the first 19 m of the line, all the collected samples were analysed for phosphates, as it was not possible to explain the steep rise of the phosphate content curve at this end with the location of the test pits or the soil’s character. Similarly, the 20 m furthest away from the sea were also controlled by analysing every collected sample. This choice was also made on the basis of the first received phosphate contents from that end of the line, as the results from the highest areas of the tested territory were remarkably low (although, in itself,

Fig. 5 Phosphate line 1. The first eight analysed samples. Results are shown as milligrams of P2O5 per 1,000 g dry soil


indicated already by the character of the soil). A more detailed sample resolution was required at the beginning and the end of the line in order to obtain a picture of possible fluctuations in these areas. The area between both ends of the line was complemented with analyses of every fifth sample (Fig. 6). The first sampling line was also complemented with two short lines of samples in the immediate vicinity—1 m away from the first line and from each other. These were positioned parallel to the first line, but were extended 4 m into the sea, i.e. these 15-m-long lines crossed the present shoreline. The reason for extending the phosphate sampling lines was to make this study comparable to results obtained on archaeological sites, where soil samples had been taken in areas presumed to have been below the sea level, and thereby to enable the possible detection of the pattern in phosphate content by the lower level as our models propose. A fourth line of 15 m, similarly crossing the land/water area, was placed ca. 150 m west from the jetty and the lines 1–3 on the area between the abandoned and the active harbour of Österby. Methodologically, for lines 2–4, the same methods were used as the first line3. As for the samples from the water, the sample depth was counted from the earth surface under the water and not from the water surface (the depth of the water did not exceed 10 cm); however, a certain degree of arbitrariness must be reckoned upon because of the problems connected with test pit sampling under the water.

Results Figures 5, 6 and Table 1 show the horizontal distribution of phosphates in line 1 in the soil of the old, abandoned harbour of Österby. The analysed 47 samples have phosphate contents ranging between 19.8 and 204.16 mg P2O5 per 1,000 g. The mean value is 112.4 and the standard deviation is 41.8. Figure 6 shows that the phosphate value grows steadily with the decrease in elevation. For the sake of the present analysis, the samples will be divided into three groups based on topographical and stratigraphical criteria. The first group, consisting of 13 samples, was collected from the higher parts of the site, beyond the dark layer, between 58 and 70 m from the present shoreline. The soil in these test pits contained more gravel than the soil in the test pits in the lower parts of the site. This zone displays considerably lower phosphate content than the other two groups as seen in Table 1. The second group consists of 17 samples collected from the test pits between 17 and 57 m from the present shoreline. This constitutes a zone of its own both because of the stratigraphical characteristics of the test pits, where a dark layer occasionally could be observed in between loamy, clay and sand mixed grey-coloured soil, and because of the topography—there is a slight decrease in elevation between this zone and the previous one. The dark layer in this area is possibly seen as a result of human activity at the site. This is also reflected in the phosphate values, which are higher in this area than in the previous zone; the observed pattern corresponds with models attained in studies of Stone Age coast-bound sites. 3 Phosphate determination of lines 2–4 was done by Kjell Persson in the laboratory of Stockholm University by the citric acid method determining milligrams of P2O5 per 100 g dry soil (Persson 2008).

Ilves and Darmark

Fig. 6 Phosphate line 1. All the analysed samples and their division into three groups based on topographical and stratigraphical criteria. Results are shown as milligrams of P2O5 per 1,000 g dry soil

The third group of 17 samples derives from the test pits closest to the sea, between 0 and 16 m from the present shoreline. The test pits from which the samples were taken contained loamy grey soil mixed with clay and sand, and were situated within a waterlogged area. This zone is flat and the increase in elevation is only 2 cm. The zone displays higher phosphate values than average, as summarised in Table 1. How should these results be interpreted? There is a strong negative correlation between elevation and phosphate content, meaning that the higher parts of the site contain low phosphate values and vice versa. The middle area with darker layer observed in several test pits is not differentiating this trend. This relation, between elevation and phosphate content, makes one suspicious of this being a natural distribution. However, the flat landscape of the site makes this implausible. The elevation at the site is less than 1 cm per metre (56 cm in 70 m). This terrain excludes the probability of a major soil movement/erosion from the upper parts of the site to the lower, which otherwise could be an explanation for the observed pattern. We are therefore inclined to see the higher phosphate values between the dark layer and the present shoreline, i.e. in group 3, as the result of human activity at the site and as a tendency for the site’s contemporary phosphate-generating matter to Table 1 Österby Old Harbour Site Phosphate

Group 1 (n=13)

Min

19.8

Max

117.5

Group 2 (n=17) 80.1

Group 3 (n=17)

Total (n=47)

83.6

19.8

161

204.2

204.2

Average

68.9

114.2

143.9

112.4

SD

35.7

21.9

31.7

41.8

Phosphate values divided into three groups based on the context of the test pits


accumulate at the water edge. The tendency is also supported by the additional lines 2 and 3, both showing a similar pattern with significant oscillations in the phosphate distribution in the vicinity of today’s shoreline, and in addition, somewhat decreasing oscillations further into the water (Figs. 7 and 8)—as observed on several Stone Age sites (see Broadbent 1979, figs. 10–12; Löfstrand 1974, figs. 94–95). Phosphate sampling line 4, which was meant to be a reference line and placed farther away from the old harbour site, although showing a different trend of phosphate distribution and generally lower values than lines 1–3 (Fig. 9), could not, however, be used to support the present argumentation. Over half of the analysed samples had a high content of CaCO3 which causes reaction with the citric acid used for phosphate content determination, and it is likely that the phosphate contents differ from the attained results (Persson 2008). Furthermore, it cannot be guaranteed that sampling results of line 4 represent soil without human influence because of the line’s relative closeness to both the active and the abandoned landing site.

Discussion Ancient shorelines above current sea level exist worldwide. In this article, we have examined how the relation between sites with human activity and ancient shores in land uplift areas has been studied in archaeology and highlighted related dilemmas. Starting from studies of Stone Age coastal sites in the Baltic Sea region, we have discussed models based on phosphate analysis as possible methods for establishing the exact position of the seashore at the time of a site’s occupation. In order to create a frame of reference for the archaeological data, a model of sharply delineated phosphate values at the former shoreline and a model of increased and oscillating phosphate values on different levels inside the archaeological localities were

Fig. 7 Phosphate line 2. Dashed line marking represents the shoreline. Results are shown as milligrams of P2O5 per 100 g dry soil

Ilves and Darmark


specifically tested in our study of an abandoned modern-day harbour site. The case of Österby produced answers to the question of the reliability of the method— oscillating and increased phosphate values at the water edge at this seaside site support the observations attained in the studies of Stone Age coast-bound sites. However, for particular discussion on the archaeological potential of phosphate distribution model suggesting increased and oscillating phosphate values at the former water level, the results from the experimental case of Österby are also explicitly compared with some deeper-time archaeological data sets from different environmental settings.



Figure 10 shows the phosphate distributions crossing the shorelines at the Stone Age coastal settlement site of Lundfors (Broadbent 1979: p. 28, fig. 11) and at the early medieval inland lacustrine site of Garn connected to iron forging (Ilves, in preparation). The Lundfors site is situated in the land uplift areas of northern Sweden, Garn in eastern middle Sweden. These sites were chosen since one of the purposes of these investigations was to the study shoreline relation by means of systematically implemented phosphate analysis. The sampling lines from Lundfors and Garn are shown in comparison with one of the representative lines from Österby harbour—line 2 (see also Fig. 7) that crossed the land/water area and is thereby comparable with the sampling lines from Lundfors and Garn. The environmental

Fig. 10 Phosphate distribution lines at the presumed contact zone between land and water at the time of use at a Österby, b Garn and c Lundfors

Ilves and Darmark

settings as well as the date and nature of the activities conducted at these places have not been the same, which also concerns the degree of archaeological visibility of these activities. Therefore, the phosphate degrees are not on the same scale as it is the character of the activity which decides the amount of phosphate in the soil. All three phosphate sampling lines at these sites show, however, practically identical pattern at the suggested shoreline—significant oscillations in the phosphate distribution at the sites’ lowest sections. This is quite remarkable considering that the sites have different topographical, environmental and cultural settings. Thus, we are confident to state that the model suggesting increased and oscillating phosphate values at the former water level is potentially applicable at different archaeological sites for determining the relation between a given site and the shoreline at the time when the site was used in areas with raised shorelines. The three sites illustrated, although different in many respects, are however characterised by the fact that these were used during a rather short period of time. The question on the location of the exact previous shorelines at more complicated sites with long occupation spans during times of falling (or rising) sea level based on the suggested phosphate distribution model has not been addressed yet. It would probably be difficult to argue for the possibility to segregate shorelines of different periods using phosphate analysis at sites with prolonged usage since the pattern at the former shorelines would be disturbed by subsequent activity. At sites with long occupation spans, only the last phase of water-bound activities would be visible and older phases would remain underrepresented. However, it is reasonable to hypothesise that in case of faster isostatic uplift periods at the long-term used coastal sites, the pattern of significant concentrated oscillations in the phosphate distribution at the former water level could be visible as following peri-water margin activities would in such case leave a gap marking the move following water. The method of using the phosphate distribution model on precise estimations of where the old seashores may have been situated should thus be specifically tested also on presumed coastal sites of prolonged usage. Notwithstanding its limitations, on the basis of the implemented study we consider the phosphate distribution model suggesting increased and oscillating phosphate values at the former water level to be potentially useful in archaeology for precise estimations of where the old seashore may have been situated when the site was used. We are optimistic that this model is useful for establishing the exact shoreline in any case where humans have been present, leaving behind organic waste deposits by the raised shoreline, especially in case of sites which are otherwise characterised by low or equivocal archaeological visibility.

References Ambrosiani, B. (1981). Changing water-levels and settlement in the Mälar District since AD 700. In: Köngsson, L.-K., & Paabo, K. (Eds.), Florilegium Florinis Dedicatum. Striae 14, Uppsala, pp. 140–143. Andrews, J. T., McGhee, R., & McKenzie-Pollock, L. (1971). Comparison of elevations of archaeological sites and calculated sea levels in arctic Canada. Arctic, 24, 210–228. Arrhenius, O. (1931). Markanalysen i arkeologiens tjänst. Geologiska Föreningens i Stockholm Förhandlingar, Bd. 53, H. 3: 47–59. Arrhenius, O. (1935). Markundersökning och arkeologi. Fornvännen, Årg, 30, 65–76.

Critical and Methodological Aspects of Shoreline Determination Arrhenius, G. (1945). Gånggriftstidens boplatsnivåer i Södertörn. Geologiska Föreningens Förhandlingar, Bd. 67, H. 4: 498–510. Arrhenius, B. (1974). Arkeologi i laboratoriet. Kuml: 287–290. Berglund, M. (2005). The Holocene shore displacement of Gästrikland, eastern Sweden: a contribution to the knowledge of Scandinavian glacio-isostatic uplift. Journal of Quaternary Science, 20(6), 519–531. Bethell, P., & Máté, I. (1989). The Use of Soil Phosphate Analysis in Archaeology: A Critique. In: Henderson, J. (ed.), Scientific Analysis in Archaeology and its interpretation. Oxford University Committee for Archaeology, Monograph No. 19, pp. 1–29. Bird, E. (2008). Coastal geomorphology: an introduction. 2nd edition. Wiley, New York. Björck, N. (2003). Neolithic Society in Eastern Sweden. Segmentary, virilocal and animistic? In: Rönnby, J. (ed.), By the Water. Archaeological Perspectives on Human Strategies around the Baltic Sea. Södertörn Academic Studies 17, Huddinge, pp. 11–37. Blake, W. (1961). Russian settlement and land rise in Nordaustlandet, Spitsbergen. Arctic, Journal of the Arctic Institute of North America, 14(2), 101–111. Blidmo, R. (1995). Liten fosfathandbok för arkeologer. Stockholm: Arkeologikonsult AB. Broadbent, N. (1979). Coastal Resources and Settlement Stability. A Critical Study of a Mesolithic Site Complex in Northern Sweden. Aun 3, Uppsala. Cannon, A. (2000). Settlement and sea-levels on the central coast of British Columbia: evidence from Shell Midden Cores. American Antiquity, 65(1), 67–77. Carlsson, D. (1991). Harbours and trading places on Gotland AD 600–1000. In: Crumlin-Pedersen, O. (ed.), Aspects of Maritime Scandinavia AD 200–1200. Proceedings of the Nordic Seminar on Maritime Aspects of Archaeology, Roskilde, 13th–15th March, 1989, Roskilde, pp. 145–158. Christiansson, H. (1961). The Russian settlement at Russekeila and land rise in Vestspitsbergen. Arctic, Journal of the Arctic Institute of North America, 14(2), 112–118. Clague, J. J. (1983). Glacio-isostatic effects of the Cordilleran Ice Sheet, British Columbia, Canada. In D. Smith & A. Dawson (Eds.), Shorelines and Isostasy (pp. 321–343). London: Academic. Clark, P. U., & Fitzhugh, W. W. (1992). Postglacial relative sea level history of the Labrador coast and interpretation of the archaeological record. In L. L. Johnson & M. Stright (Eds.), Paleoshorelines and Prehistory: An Exploration of Method (pp. 189–213). Boca Raton: CRC. Crosby, A. W. (2004). Ecological Imperialism. The Biological Expansion of Europe, 900–1900. Cambridge University Press. Darmark, K., & Sundström, L. (2005). Postboda 3—en senmesolitisk lägerplats i Uppland. SAU Skrifter 9. Uppsala. Diamond, J. (2005). Collapse. How Societies Choose to Fail or Survive. Penguin, London. Dobat, A. S. (2002). Die Schlei in der Wikingerzeit. Eine Maritime Kulturlandschaft im Spiegel der archäologischen und onomastischen Quellen. Schriftliche Hausarbeit zur Erlangung des Grades eines Diplom-Prähistorikers (Dipl.-Prähist.) der Mathematisch-Naturwissenschaftlichen Fakultät der Christian-Albrechts-Universität zu Kiel. Kiel. Ekman, M. (1993). Postglacial rebound and sea level phenomena, with special reference to Fennoscandia and Baltic Sea. In: Kakkuri, J. (Ed.), Geodesy and Geophysics. Lecture Notes for NKG-Autumn School 1992 organized by Nordiska Kommissionen för Geodesi, Korpilampi—Finland 7–13 September 1992, Helsinki, pp. 7–70. Ekman, M. (2001). Computation of historical shore levels in Fennoscandia due to Postglacial Rebound. Small Publications in Historical Geophysics, No. 8. Summer Institute for Historical Geophysics, Åland Islands. Eronen, M. (1974). The history of the Litorina Sea and associated Holocene events. Societas Scientiarum Fennica. Commentationes physico-mathematicae, 44: 4, Helsinki. Eronen, M. (1983). Late Weichselian and Holocene shore displacement in Finland. In: Smith, D. E., & Dawson, A. G. (Eds.), Shorelines and Isostasy. Academic, New York, pp. 183–207. Eronen, M. (1987). Global sea-level changes, crustal movements and quaternary shorelines in Fennoscandia. Geological Survey of Finland, 2 (special paper): 31–36. Florin, S. (1948). Kustförskjutningen och bebyggelseutvecklingen i östra Mellansverige under senkvartär tid. Stockholm. Giddings, J. L., & Anderson, D. D. (1986). Beach ridge archaeology of Cape Krusenstern: Eskimo and pre-Eskimo settlements around Kotzebue Sound. Publications in Archaeology 20. Washington: National Park Service. Halén, O. (1994). Sedentariness during the Stone Age of Northern Sweden in the light of the Alträsket site, c. 5000 B.C., and the comb ware site Lillberget, c. 3900 B.C. Source Critical Problems of Representativity in Archaeology. Acta Archaeologica Lundensia, Series in 4º, No. 20, Stockholm.

Ilves and Darmark Harff, J., Lampe, R., Lemke, W., Lüdke, H., Lüth, F., Meyer, M., et al. (2005). The Baltic Sea: a model ocean to study interrelations of geosphere, ecosphere, and anthroposphere in the coastal zone. Journal of Coastal Research, 21(3), 441–446. Hodder, I. (1982). The Present Past. An Introduction to Anthropology for Archaeologists. Cambridge University Press, London. Hoppe, G., & Markus, F. (2001). Kring frågan om estlandssvenskarnas äldsta historia. Kustbon, 3–4. Hoppe, G., Nõulik, I., & Punning, J.-M. (2002). Shoreline development and Swedish colonisation of north-west Estonia during the Middle Ages. GeoJournal, 56(3), 185–190. Ilves, K. (2006a). Archaeological investigations on the coast of Sutu bay on Saaremaa. Archaeological Fieldwork in Estonia 2005, Tallinn, 83–89. Ilves, K. (2006b). Place-names about life by the sea—an archaeological perspective on the Estonian Swedish landscape. Folklore, 34, 89–104. Jones, R. (1975). Why did the Tasmanians stop eating fish? In R. A. Gould (Ed.), Explorations in Ethnoarchaeology. A School of American Research Book (pp. 11–47). Albuquerque: University of New Mexico Press. Jussila, T., & Kriiska, A. (2004). Shore displacement chronology of the Estonian Stone Age. Estonian Journal of Archaeology, 8(1), 3–32. Königsson, L.-K., & Paabo, K. (eds.) (1981). Florilegium Florinis Dedicatum. Striae 14. Uppsala. Lang, V., & Kriiska, A. (2001). Eesti esiaja periodiseering ja kronoloogia. Eesti Arheoloogia Ajakiri, 5(2), 83–109. Lejoneke, P., & Rönnby, J. (2005). Svalbard. Marinarkeologisk rekognoscering 1998 och 2000. Arkeologi, Södertörns Högskola. Huddinge. Lindén, M., Möller, P., Björk, S., & Sandgren, P. (2006). Holocene shore displacement and deglaciation chronology in Norrbotten, Sweden. Boreas, 35, 1–22. Löfstrand, L. (1974). Yngre stenålderns kustboplatser. Undersökningarna vid Äs och studier I den gropkeramiska kulturens kronologi och ekologi. Aun 1. Uppsala. Markus, F. (2004). Living on Another Shore. Early Scandinavian Settlement on the North-Western Estonian Coast. Uppsala. McGhee, R. (1979). Paleo-Eskimo Occupation at Port Refuge. Archaeology Survey of Canada Paper 92. Ottawa: National Museum of Canada. Meyer, M., & Harff, J. (2005). Modelling palaeo coastline changes of the Baltic Sea. Journal of Coastal Research, 21(3), 598–609. Middleton, W. D. (2004). Identifying chemical activity residues on prehistoric house floors: a methodology and rationale for multi-elemental characterization of a mild acid extract of anthropogenic sediments. Archeometry, 46(1), 47–65. Mägi, M. (2004). "…Ships are their main strength." Harbour sites, arable lands and chieftains on Saaremaa. Estonian Journal of Archaeology, 8(2), 128–162. Mägi, M. (2006). Excavations on the coasts of Prehistoric and Medieval Saaremaa. Archaeological Fieldwork in Estonia, 2005, 65–82. Mobley, C. M. (1988). Holocene sea levels in southeast Alaska: preliminary results. Arctic, 41(4), 261– 266. Møller, J. J. (1987). Shoreline relation and prehistoric settlement in northern Norway. Norsk Geografisk Tidsskrift, 41, 45–60. Møller, J. J. (1989). Geometric simulation and mapping of Holocene relative sea-level changes in Northern Norway. Journal of Coastal Research, 5(3), 403–417. Møller, J. J. (2003). Late Quaternary sea level and coastal settlement in the European North. Journal of Coastal Research, 19(3), 731–737. Nõulik, I. (2001). Noarootsi poolsaare looduse ja inimasustuse kujunemislugu viimase tuhande aasta jooksul. Magistritöö. Käsikiri Tallinna Ülikooli Akadeemilises raamatukogus. Nunez, M. (1977). Archaeology through soil chemical analysis: an evaluation. University of Helsinki, Department of Archaeology. Unpublished document, stencil 14. Helsinki. Nunez, M. (1978). The Vantaa phosphate survey; a practical illustration of the method. Annales Academiae Scientiarum Fennicae, Series A III, Geologica-geographica, 124. Orviku, K. (1992). Characterisation and evolution of Estonian seashores. Doctoral thesis at the University of Tartu. Käsikiri Tartu Ülikooli Raamatukogus. Persson, K. (2008). Fosfatanalys, Österby Estland. Uppdragsrapport nr 95. Institutionen för arkeologi och antikens kultur. Arkeologiska forskningslaboratoriet. Stockholms universitet. Petersson, M. (2006). Strandförskjutningen i Södermanland. In: Lilja, S. (ed.), Människan anpassaren— människan överskridaren. Natur, bebyggelse och resursutnyttjande från sen järnålder till 1700-tal med

Critical and Methodological Aspects of Shoreline Determination särskild hänsyn till östra Mellansverige och Södermanlands kust. Södertörns Högskola, Research reports 2006: 4, Huddinge, pp. 33–46. Rainbird, P. (2007). The Archaeology of Islands. Topics in Contemporary Archaeology. Cambridge University Press, Cambridge. Rausing, G. (1963). Fra arkæologiens laboratorium. Skalk, 1, 20–29. Risberg, J., Alm, G., Björk, N., & Guinard, M. (2007). Synkrona paleokustlinjer 7000–4000 kal. BP i mellersta och norra Uppland. In: Stenbäck, N. (Ed.), Stenåldern i Uppland: uppdragsarkeologi och eftertanke. Arkeologi E4 Uppland—studier, Volym 1, Uppsala, pp. 99–135. Ristaniemi, O., Eronen, M., Glückert, G., & Rantala, P. (1997). Holocene and recent shoreline changes on the rapidly uplifting Coast of Western Finland. Journal of Coastal Research, 13(2), 397–406. Saarse, L., Vassiljev, J., & Miidel, A. (2005). Simulation of the Baltic Sea shorelines in Estonia and neighbouring areas. Journal of Coastal Research, 19(2), 261–268. Schnell, I. (1932). Strandlinjebestämningar och markanalys. Fornvännen, Årg, 27, 40–47. Siiriäinen, A. (1982). Shore displacement and archaeology in Finland. In: Aartolahti, T., and Eronen, M. (eds.), Studies on the Baltic Shorelines and Sediments Indicating Relative Sea-Level Changes. Proceedings of the Symposium of Inqua Subcommission on Shorelines of Northwestern Europe held at the Lammi biological station 13th September 1981. Annales Academia Scientiarum Fennicae, Series A. III Geologica-Geographica, Helsinki, pp. 173–184. Simonsen, P., & Lysnes, H. (1968). Fosfatanalyser fra Varangerbopladserne. In: Simonsen, P. (ed.), Varanger-Funnene VI. Analyseresultater og mindre rapporter. Tromsø Museums Skrifter, Vol. VII, Hefte VI, Tromsø/Oslo, pp. 24–36. Stahl, A. (1964). Sjöfart och fiske hos Estlands svenskar. In E. Lagman (Ed.), En bok om Estlands svenskar 2 (pp. 191–230). Stockholm: Svenska Odlingens Vänner. Sundström, L., & Darmark, K. (eds.) (2005). Bålmyren—en familjebaserad tidigneolitisk kustboplats i Uppland. SAU Skrifter 7. Uppsala. Sundström, L., Darmark, K., & Stenbäck, N. (eds.) (2006). Postboda 2 och 1. Säsongsboplatser med gropkeramik från övergången tidigneolitikum-mellanneolitikum i norra Uppland. SAU Skrifter 10. Uppsala. Ulriksen, J. (1992). Lokalisering af anløbspladser. In: Sjællands jernalder. Beretning fra et symposium 24. IV.1990 i København. Arkæologiske skrifter 6, Arkæologisk institut, Københavns universitet, København, pp. 91–112. Ulriksen, J. (1998). Anløbspladser. Besejling og bebyggelse i Danmark mellem 200 og 1100 e.Kr. En studie af søfartens pladser på baggrund af undersøgelser i Roskilde Fjord. Roskilde. Österholm, I. (1991). Phosphate surveying of coastal settlements. In: Crumlin-Pedersen, O. (ed.), Aspects of Maritime Scandinavia AD 200–1200. Proceedings of the Nordic Seminar on Maritime Aspects of Archaeology, Roskilde, 13th–15th March, 1989, Roskilde, pp. 269–274.

Further Reading The Estonian State Archives 982.1.15 page 13 www.maaamet.ee (map of soils) [15.02.2007]