The data which will be digitized and ingested as part of VISEAD will be building on The Strategic Environmental Archaeology Database [SEAD] which is underpinned by a well established set of scientific disciplines and principles which allow past environments, climates and human impacts to be reconstructed from proxy data sources. In this segment follows descriptions of the analysis methods used by the archaeological research labs whose data will be prepared by the VISEAD project. For further information about the other proxies in SEAD, please visit www.sead.se.
Stable isotope analysis
An isotope is a variety of a chemical element. There is a distinction between unstable isotopes, which decays over time (e.g. 14C), and stable isotopes that do not (e.g. 13C). Ratios of stable isotopes are compared with certain standards in an effort to draw conclusions about such things as diet and provenience .
The most commonly used stable isotopes in relation to archaeological studies are carbon (13C/12C), nitrogen (15N/14N), and oxygen (18O/16O). These are referred to as light stable isotopes, used to interpret isotopic variability in natural ecosystems. There are also heavy stable isotopes, strontium (87Sr/86Sr) and lead (208Pb/204Pb, 207Pb/204Pb, 206Pb/204Pb), which are used to gain insight into the source of biological/geological material as well as place of origin. Commonly bone and tooth tissues, from recovered human and animal remains, are used in stable isotope analysis. Although other biological materials (e.g. hair, nails) can be used if there was extraordinary preservation (Krigbaum 2008).
The light stable isotopes have proven themselves to be useful for reconstructing human palaeodiet, especially when viewed in relation to the archaeological record and secondary subsistence evidence (faunal and floral remains), whilst heavy stable isotopes allows you to infer a person’s place of origin and patterns of migration. When interpreting stable isotope ratios it is important to understand the variation and cycling of isotope ratios in the natural ecosystems. There is, for example, a dichotomy between the terrestrial and marine ecosystems which helps you delineate different subsistence regimes (Krigbaum 2008).
Biomolecular archaeology and lipids
The biomolecular archaeology of lipids studies the remains of organic residues, such as fats, oils and waxes. Lipids are medium-sized atoms created from organic residue of different kinds. A broad definition of lipids is hydrophobic (not soluble in water) or amphiphilic (both water-loving and fat-loving properties) small molecules. The most widely used method for determining the origin of these organic residues is matching the structures of individual compounds and comparing them to contemporary animal and plant natural products. These are referred to as biomarkers (Evershed 1993, Isaksson 2009).
Lipid analysis is often performed on ceramics, since identifying the organic residues will let you infer what the ceramic vessels contained or what food/drinks were produced (e.g. animal fats, dairy products, vegetable oil). Common methods to measure and analyze lipids are Gas Chromatography [GC], Mass Spectrometry [MS] and the two combined GC-MS which provides the best way to analyze the lipids with such accuracy as to identify individual compositions.
The results from lipid analysis are often used together with the results from stable isotope studies for the purpose of reconstructing the palaeodiet of various cultures.
Dendrochronology and wood analysis
Identification of the tree species found at an archaeological site can give valuable information on resource utilisation, trade and climate. It is also essential if the wood is to be carbon dated. Wood macrofossils can also be vital in identifying the presence of trees when pollen production has been limited by environmental stress, including climatic conditions.
Dendrochronological data are instrumental in calibrating radiocarbon dates and dating sites and events. In dendrochronology crossdating is a fundamental principle. By matching patterned ring-width variations between living trees of the same species you can build a tree-ring chronology and assign common-era dates to the rings in the tree-ring sequence. Then you can match the pattern in annual variations in ring-width from specimen to specimen, working yourself back in time. Starting with a living specimen tree-ring sequence, you match the sequence overlap with older and older specimens found in various contexts, including archaeological, gradually building a chronology. Swedish tree-ring chronologies are based mainly on oak, beech, pine, and spruce, but in some cases other species are included (Nash 2008, Linderson 2017).
In environmental application of dendrochronology tree-ring sequences are used to reconstruct environmental variables, such as temperature, precipitation, fire frequency, insect infestation, and more.
Pottery is a group often mistakenly interpreted as a homogenous mass, since it is made using the same raw material, which is clay. Clay is however often mixed with different material depending on the geologic conditions in your area. These conditions also have an effect on the cultural choices made in that area (Lindahl & Eriksson, 2013) .
Studying thin-sections of ceramic handicraft can reveal facts about pottery, technology, and the choice of temper and clay. For example, by identifying variations in choice of raw material and tempering of ceramic vessels it will allow you to distinguish between ceramic ware used for household purposes and finer wares, as well as identify new information regarding the possible import of ceramic styles or potters.
Evershed, R. P. 1993. Biomolecular Archaeology and Lipids. World Archaeology, Vol. 25, No.1, Biomolecular Archaeology (Jun., 1993). pp. 74-93.
Isaksson, S. 2009. Vessels of Change. A long-term perspective on prehistoric pottery use in southern and eastern middle Sweden based on lipid residue analyses. Current Swedish Archaeology, Vol. 17. pp.131-149.
Krigbaum, J. 2010. Stable Isotope Analysis. Encyclopedia of Archaeology. pp. 2075-2077
Lindahl, A. & Eriksson, T. 2013. The Handicrafts of Iron Age Pottery in Scandinavia. Regionalities and Tradition. Lund/Archaeological Review, Vol. 18. pp.45-60.
Linderson, H. 2017. Dendrokronologisk datering. Hur fungerar dendrokronologisk datering? http://www.geologi.lu.se/service/vara-laboratorier/nationella-laboratoriet-for-vedanatomi-och-dendrokronologi/dendrokronologisk-datering. – 2017-01-31
Nash, S. 2010. Dendrochronology. Encyclopedia of Archaeology. pp. 1083-1088.
Papmehl-Dufay, L., Stilborg, O., Lindahl, A., Isaksson, S., 2013. For everyday use and special occasions : a multi-analytical study of pottery from two early neolithic funnel beaker (TRB) sites on the island of Öland, SE Sweden. Naturwissenschaftliche Analysen vor- und frühgeschichtlicher Keramik III: Methoden, Anwendungsbereiche, Auswertungsmöglichkeiten 238. p.123-152. http://lup.lub.lu.se/record/4195295