[1] Univ Aberdeen, Sch Geosci, Dept Geog & Environm, Elphinstone Rd, Aberdeen AB24 3UF, Scotland
[2] Univ Cambridge, Dept Archaeol, Cambridge Archaeol Unit, 34A StoreysWay, Cambridge CB3 0DT, England
[3] Early Mines Res Grp, 19 High St, Fen Ditton CB5 8ST, Cambs, England
[4] Univ Santiago, Fac Biol, Dept Edafol & Quim Agr, Campus Sur, Santiago De Compostela 15782, Spain
[5] Univ Northampton, Sch Sci & Technol, Newton Bldg, Northampton NN2 6JD, England
[6] Rhodes Univ, Dept Geog, ZA-6140 Grahamstown, Eastern Cape, South Africa