A light stable isotope (C, N, H, O) approach to identifying movement of medieval textiles in North West Europe

This thesis examined how light stable isotopic analysis could be used to examine the provenance of archaeological wool textiles preserved by anoxic waterlogging.

Preliminary studies in modern sheep wool samples showed that their carbon (δ13C), nitrogen (δ15N), un-exchangeable hydrogen (δ2H) and oxygen (δ18O) composition varied systematically with geographical location in British Isles and Iceland, but were significantly influenced by farming practice (fodder provision, fertilizer use). Keratin and collagen isotope values within a single sheep were shown to be systematically related. Experimental characterisation of the isotopic effects of wool degradation by elemental, amino acid and isotopic composition showed that changes in experimentally buried samples were minimal compared to samples treated under high-temperature hydrous conditions, which showed significant hydrolysis, oxidation and racemisation.

These results were used to interpret data from 101 archaeological textiles from contexts dated between AD 7001600 from excavations at Reykholt, Iceland; York and Newcastle, Britain; Hessens, Germany; and Birka, Sweden. Local isotope range for each location was defined by assemblage median ± maximum variation derived from a modern flock. Isotopic identifications of local/non-local wool did not always correspond to typical/atypical interpretations of textile origin based on features of textile construction, fibre type and dye use. Thus distinctions could be made between the movement of textiles (atypical construction, non-local composition), movement of textile techniques (atypical construction, local composition) and movement of raw wool (typical construction, non-local composition). The most significant limitation of the technique was insufficient isotopic difference between regions of origin and deposition. The results made a significant contribution to understanding the origin of a number of specific textile types, including the much-discussed ‘Frisian cloth’.