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Early atmospheric metal pollution provides evidence for Chalcolithic/Bronze Age mining and metallurgy in Southwestern Europe
- Martínez Cortizas, Antonio, López-Merino, Lourdes, Bindler, Richard, Mighall, Tim, Kylander, Malin E.
- The Science of the total environment 2016 v.545-546 pp. 398-406
- aluminum, chromium, copper, isotopes, lead, metallurgy, mining, organic matter, paleoecology, peat, pollution, sediments, silicon, titanium, tracer techniques, zinc, Spain
- Although archaeological research suggests that mining/metallurgy already started in the Chalcolithic (3rd millennium BC), the earliest atmospheric metal pollution in SW Europe has thus far been dated to ~3500–3200cal.yr. BP in paleo-environmental archives. A low intensity, non-extensive mining/metallurgy and the lack of appropriately located archives may be responsible for this mismatch. We have analysed the older section (>2100cal.yr. BP) of a peat record from La Molina (Asturias, Spain), a mire located in the proximity (35–100km) of mines which were exploited in the Chalcolithic/Bronze Age, with the aim of assessing evidence of this early mining/metallurgy. Analyses included the determination of 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 ~8000 to ~4980cal.yr. BP the Pb composition is similar to that of the underlying sediments (Pb 15±4μgg−1; 206Pb/207Pb 1.204±0.002). A sustained period of low 206Pb/207Pb ratios occurred from ~4980 to ~2470cal.yr. BP, which can be divided into four phases: Chalcolithic (~4980–3700cal.yr. BP), 206Pb/207Pb ratios decline to 1.175 and Pb/Al ratios increase; Early Bronze Age (~3700–3500cal.yr. BP), 206Pb/207Pb increase to 1.192 and metal/Al ratios remain stable; Late Bronze Age (~3500–2800cal.yr. BP), 206Pb/207Pb decline to their lowest values (1.167) while Pb/Al and Zn/Al increase; and Early Iron Age (~2800–2470cal.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 show a rapid 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, and reconcile paleo-environmental and archaeological records.