Geochemical analysis using portable X-ray fluorescence

Authors: Cannell, R.J.S., Cheetham, P.N. and Welham, K.

Pages: 421-454

Abstract:

This chapter presents the results from geochemical analyses of soil samples from Area 6, where remains from production and a palisade were identified (Ostmo, Ch. 9). The samples were taken during the 2011-12 excavation campaign, and later analysed using portable X-ray fluorescence (pXRF) to obtain the elemental composition. The geochemical data from the samples was then statistically treated using principal component analysis to simplify the data volume. This reduced the elemental quantities into activity types, which could be further refined to areas and, from selected cores taken, by stratigraphic layer. The analytical results suggest that several different activities occurred in Area 6 in the late Iron Age and early Middle Ages. In addition to samples taken on a regular grid, an oven feature was sampled for comparison, and to aid interpretation of its function. The sampled oven feature, dated to early Site Period V, appears to have been used for organic processes such as corn-drying rather than metalworking. In the same stratigraphic phase, food-processing, potentially involving seaweed ash or a by-product of this process, was identified. To the west of this feature, copper alloy-working on a small scale possibly occurred during the Viking Age. Prior to this, perhaps as early as the Roman Iron Age, the site had a different function, one that might have involved the addition of organic waste such as dung collected as a by-product of animal stocking, or more likely the middening of organic waste. The waste management and use of space appears delineated; despite the small area, clear clustering patterns appear. As portable XRF technology and its application-particularly to soils in archaeology-are relatively new, its suitability warrants debate. This chapter therefore also contains a short review of the use of pXRF in archaeology.

Source: Scopus