Multi-element analysis of soils from Scottish historical sites. Interpreting land-use history through the physical and geochemical analysis of soil

Arable farming in the Highlands and Islands of Scotland by the 18th century was characterized by labour-intensive techniques of husbandry and the transfer of fertilizing resources from their extensive non-arable sector to their arable land. Such practices had a considerable impact on soil development and characteristics. The use of inductively coupled plasma-mass spectrometry (ICP-MS) in this study has allowed the geoarchaeological significance of a broad range of elements to be investigated on soils collected from a former settlement site on the Trotternish peninsula, Isle of Skye. The on-site geochemical data are expressed as "enrichment factors" relative to the mean concentration of the control samples. Of the elements investigated in this study Ba, La, Ce, Pr, K, Cs, Th, and Rb were found to be indicative of human settlement at Greaulin, whilst the spatial enrichment patterns for Ca and Sr suggest additions of shell sand to the arable land over the central region of the site. Vanadium, Co, Zn, Pb, Ni, Ga, Sc, Mg, Cu and U all showed minimal or no on-site enrichment. The generally lower on-site levels of percentage loss-on-ignition (relative to the control soils) are interpreted as reflecting the former use of the fields for cultivation. Interpretation of the P results, in the light of documentary evidence, suggest that some of the 19th century croft farmsteads may have reoccupied sites formerly inhabited during pre-clachan times. Hence, the clachan at Greaulin may not have been as long-standing a settlement feature as traditionally envisaged.