The physical setting and sampling

5.2.1 The geology and pedology of Avaldsnes

The Cambric, silty loam soils of Avaldsnes overlie undulating bedrock. Bedrock is exposed over low peaks, typical of the wet, cool, West Norwegian maritime climate and landscape. Soil depths vary greatly over the site, and beneath the deepest areas are buried soils, which appear to be organic rich, fairly stone-free and shallow, developing directly over weathering bedrock, and typical of Regosols. The geology of Karmøy consists of both sedimentary and igneous rocks, and previous geological studies have focused on the volcanic trenching and intrusions between the dominant rock types (Poppleton and Piper, 1990). There are various published maps of the geology, and the general consensus is that the site lies upon the Karmøy ophiolite group, formed 495-485 million years ago (Fossen et al., 2007). The origin of ophiolites (part of the amphibolites group) is the oceanic crust and mantle, and they are generally seen as the result of ocean floor spreading and later uplift. Volcanic activity associated with this has resulted in igneous granites, metamorphic sandstones, quartz and pillow lava deposits in a series of intrusions as the sea floor spread. The composition of amphibolites is a SiO4 tetrahedra, which are often iron and magnesium rich. Due to the alkaline base, they also contain calcium in the mineral structure, and under the present climatic conditions produce near-neutral to slightly acidic soils. The

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granites and metamorphic rocks are unusual on Karmøy in that they are very varied in composition from the melting of the continental land mass, and contain everything from limestone to marble within the granite amalgamation. The site lies close to a geological boundary between the green schist which underlies much of the archaeological site, and volcanic metamorphic sandstones and quartz (N.G.U, 2013). The alkaline, iron rich geology has produced fine silt loam soils that are very productive where of sufficient depth for cultivation.

The area of the site where the samples are taken contains no glacial deposits. Therefore all samples are directly related to the geology and subsequent weathering to soils, and anthropogenic activity.

5.2.2 Site specific aims and objectives

In chapter one, the overall aim was stated as assessing the potential of integrated geochemical analysis using pXRF to better understand the use of space and the range of activities in Viking Age settlements. The objectives include the use of coring as a sampling method to capture temporal and spatial change. As part of the RMP, the targeted areas fit within the project aims of understanding the economic diversity and structure of the site as a power centre in the Iron Age. The long Iron Age in southern Scandinavia shows upheaval and change in land ownership, hierarchy and social structure, cultural and cultic foci, settlement and household forms, in fact in every way but for the elongated exterior form of the longhouse (Herschend, 2009). Therefore generalisations should not be made. By the later Iron Age, when hierarchy becomes more pronounced in architecture, the specialisation and delineation of production areas within high status sites appears more strongly (e.g. Järrestad and Tissø) (Jørgensen, 2002, Söderberg, 2005).

The division of space in other comparable high status settlements, by the Migration Period suggest that divided cultural and economic functions indicate specialty beyond the intermixed domestic and industrial typical of the farmstead. This is simultaneously a social and economic division. How divisions are manifest, whether by deliberate and/or accidental waste accumulation, they demonstrate ingrained practices if they endure over time, and geochemistry is reliant on repeated action. The aim was, via geochemistry using pXRF, to see if these divisions were apparent, how they were structured, and the types of activities that could be identified.

Temporality is a challenge to geochemistry. Therefore at Avaldsnes, the first case study in this research, cores were taken to test if they could provide an additional dimension to the single, horizontal layer sampling and analysis. This came from the extensive coring done over the site during the excavation seasons of 2011 and 2012, which was aimed at understanding site formation processes and archaeological prospection (see 4.2.2).

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Figure 5.3. Map showing the areas excavated by the Royal Manor Project in relation to current buildings and roads at Avaldsnes, Karmøy, Norway. Map source: Author/RMP/Norwegian Mapping Authority, 2016

5.2.3 Sampling methods and hindrances

The geochemical sampling for multi-elemental analysis at the site was focused on Area 6 (figure 5.3), which was excavated in 2012. This area was selected for practical and archaeological reasons. The silty loam cambric subsoil appeared consistent on the selected archaeologically defined surface. The revealed archaeology was complex and multiphase; however there was no immediately visible structure or pattern, such as a clearly defined house as discovered in other areas, complicating interpretive efforts. Modern disturbance presented a constant challenge during the Avaldsnes excavations, as noted in chapter 4. In Area 6, although modern intrusions such as cable trenches are present, these were nevertheless isolated and appeared demarcated, hence sampling could potentially avoid these areas.

Area 6 can be physically defined. A bedrock scarp, formed by changing geology from green schist to metaphoric sandstone, limits the area to the east and south; the scarp allows a vista over the land and coast to the east, toward Bukkøya, Karmsund, and the mainland. Modern disturbance, buildings and raised bedrock limited the available surface to the immediate south and west, whilst to the north the substantial Kjellerhaugen burial mound formed another boundary,

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delimiting an area for study. Of course, it cannot be assumed these defined boundaries had the same, or indeed any, relevance in the past.

During the excavation of Area 6, 85 postholes were recorded, along with several oven features, cooking pits, stakeholes, and stone settings (figure 5.4 and figure 5.5). There is clearly a multi-period aspect to all areas of the site; according to ¹⁴C results, Area 6 was occupied from 300 BC to AD 1160, excluding the modern geographically constrained space, as well as the activities represented within it, could be highly enlightening in regard to understanding the role of the site throughout the period as a centre for royal power. The majority of the dates relating to the area sampled for this analysis fall within the Viking Age (see figure 5.6). Geochemical results could potentially define features and specific activity areas, as well as detecting the function of oven features. For example, the purpose and use of an oven, such as for metalworking, domestic activities, or large-scale food processing, can have significant implications for the economic and social structure of the site. This was demonstrated for the Silchester site by Cook et al. (2009), who analysed samples from hearths and furnaces using laboratory-based XRF in order to specify hearth and oven function to the metals worked or domestic activity. Within buildings, ‘zones’ or ‘functional areas’ can be chemically defined in environments as varied as Neolithic Orkney to Hellenistic Turkey, and could therefore help define the use of space in Area 6 (Jones et al., 2010, Vyncke et al., 2011).

Figure 5.4. Photo of the mechanical topsoil stripping of Area 6, Avaldsnes. Taken facing south, with the flank of Kjellerhaugen, the Bronze Age burial mound, sloping up in the far right foreground of the picture. The boulders visible in the centre for- and middle-ground are from what has been interpreted as a revetment or fortification. Photo:

RMP, MCH, UiO.

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Figure 5. 5a &b. Top: The archaeological features in Area 6. Note all features are shown here; the figure does not relate to one single phase of the site. The ditch A12178 is in brown, and oven A44031 is the key shaped oven.

Bottom: As figure 5.5a, with sample locations. Map Source: Author/ RMP/ Norwegian Mapping Authority, 2016.

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Figure 5. 6. Postholes in Area 6 that have been radiocarbon dated via material in the backfill. The majority were dated using grains found in these backfills, and the dates are to 2σ. Key to abbreviations: VA= Viking Age, MIP=

Migration Period, MP= Merovingian Period, RIA= Roman Iron Age. The similar and wide date ranges are a product of the flat calibration curve in the later Iron Age. Map source: Author/RMP/Norwegian Mapping Authority, 2016.

All ¹⁴C dates courtesy of the RMP, taken from Bauer & Østmo 2013: 127.