VISEAD

Pushing the cutting edge of the Strategic Environmental Archaeology Database

Methods

 
The new data, to be digitized and ingested into The Strategic Environmental Archaeology Database [SEAD] as part of VISEAD, 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. The analysis methods used to produce these data are described down below. For further information about the other proxies in SEAD, please visit www.sead.se.

 

Stable isotope analysis

 

Sampling a tooth for 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.

Some of the more commonly analysed stable isotopes in archaeological studies are carbon (13C/12C) and nitrogen (15N/14N). These are referred to as light stable isotopes, used to interpret isotopic variability in natural ecosystems. Since the protein component of your diet affects the proportions of these isotopes in the body tissue, light stable isotopes have proven themselves to be a good proxy for palaeodiet, especially when viewed in relation to the archaeological record and secondary subsistence evidence (faunal and floral remains).

During your lifetime, the bone collagen is constantly being remodeled. Due to this the bone collagen will represent an individual’s average protein intake during several years prior totheir death. In tooth dentine, however, the isotopic composition is fixed at the time of the formation of the tooth, meaning that an analysis of different type of teeth will show possible diet change over certain stages in an individual’s life. Naturally other biological material (e.g. hair, nails), including animal remains, can also be used in stable isotope analysis, if they are preserved.

Heavy stable isotopes, such as strontium (87Sr/86Sr) and lead (208Pb/204Pb, 207Pb/204Pb, 206Pb/204Pb), are used to gain insight into the source of biological/geological material as well as place of origin, i.e., an analysis could help you infer an individual’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 (e.g. societies with a marine based economy vs. a pastoral economy) (Krigbaum 2008).

 

 

Lipids analysis

 

Cholesterol_(chemical_structure).svg

Cholesterol chemical structure (example of a lipid)

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

 

6000 year old oak, Thorne moor, UK

6000 year old oak, Thorne moor, UK

 

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.

 

oak thorne moor ukDendrochronological 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.

 

Petrographic microscopy

 

Tempering grains from a ceramic thin section

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.

 

 

 

 

 

 

References

 

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