Abstract
Although archaeological research suggests that mining/metallurgy began in the Chalcolithic (3rd millennium BC), the earliest atmospheric metal pollution in SW Europe has so far been dated to approximately 3500–3200 cal. yr. BP in palaeoenvironmental archives. Low-intensity, non-extensive mining/metallurgy and the lack of suitably located archives may explain this discrepancy. We analysed the older section (> 2100 cal. yr. BP) of a peat record from La Molina (Asturias, Spain), a mire located near (35–100 km) mines exploited during the Chalcolithic/Bronze Age, to assess evidence of this early mining/metallurgy. Analyses included determining C as a proxy for organic matter content, lithogenic elements (Si, Al, Ti) as markers of mineral matter, and trace metals (Cr, Cu, Zn, Pb) and stable Pb isotopes as tracers of atmospheric metal pollution. From approximately 8000 to 4980 cal. yr. BP, the Pb composition is similar to that of the underlying sediments (Pb 15 ± 4 μg g−1; 206Pb/207Pb 1.204 ± 0.002). A sustained period of low 206Pb/207Pb ratios occurred from approximately 4980 to 2470 cal. yr. BP, which can be divided into four phases: Chalcolithic (~4980–3700 cal. yr. BP), 206Pb/207Pb ratios decline to 1.175 and Pb/Al ratios increase; Early Bronze Age (~3700–3500 cal. yr. BP), 206Pb/207Pb increase to 1.192 and metal/Al ratios remain stable; Late Bronze Age (~3500–2800 cal. yr. BP), 206Pb/207Pb decline to their lowest values (1.167) while Pb/Al and Zn/Al increase; and Early Iron Age (~2800–2470 cal. yr. BP), 206Pb/207Pb increase to 1.186, most metal/Al ratios decrease but Zn/Al shows a peak. At the beginning of the Late Iron Age, 206Pb/207Pb ratios and metal enrichments rapidly return to pre-anthropogenic values. These results provide evidence of regional/local atmospheric metal pollution triggered by the earliest phases of mining/metallurgy in the area, reconciling palaeoenvironmental and archaeological records.
