Environmental impact of early Basque mining and smelting recorded in a high ash minerogenic peat deposit

Fabrice Monna (1) , Didier Galop (2) , Laurent Carozza (3) , Magali Tual (1) , Argitxu Beyrie (4) , Fabrice Marembert (5) , Carmela Chateau (6) , Janus Dominik (7) , F. E. Grousset (8)

1 GéoSol - Microbiologie des sols-GéoSol
2 LCE - Laboratoire de chrono-écologie - CNRS (UMR6565)
3 Inrap - Institut national de recherches archéologiques préventives
4 University of Utah
5 LA - Laboratoire d'Anthropobiologie
6 BGS - Biogéosciences [UMR 6282]
7 Institut F.A.
8 EPOC - Environnements et Paléoenvironnements OCéaniques

More than four metres of core, covering almost 5000 years of deposition, were collected in a high ash minerogenic peat deposit located in the High Aldudes valley (Basque country), an area well known for its mineral abundance, exploited from Roman Times at least.Although minerogenic peatlands are not generally considered as the best archives to reconstruct past atmospheric metal deposition history, lead isotopic geochemistry demonstrates the integrity of the Pb record at least within the three upper meters; that is to say over the last four millennia.Zn, Cd and Cumay have been widely redistributed either by biological cycling, advective groundwater movements, or diffusional processes.Anthr opogenic lead input phases are clearly pinpointed by positive shifts in PbySc ratios with concomitant sharp drops in 206Pby207Pb ratios.They are often accompanied by significant declines in tree taxa, interpreted as increasing demand for wood to supply energy for local mining andyor metallurgical operations.Periods of mining andyor smelting activity are identified during Antiquity and Modern Times, and are also confirmed by textual and field evidence.Inputs from the Rio Tinto (Southern Spain), often invoked as a major lead contributor to the European atmosphere during Roman Times, were not detected here.This remote source was probably masked by local inputs. Other mining andyor smelting phases, only suspected by archaeologists, are here identified as early as the Bronze Age.Although the durations of these phases are possibly overestimated because of detrital inputs consequent to the release of lead from polluted soils over a long period of time after major pollutant inputs, the periods at which pollution peaks occur are in good agreement with archaeological knowledge and palaeo-botanical data.Thecombination of geochemical and palaeo-botanical techniques with field archaeology, therefore provides a powerful tool in studying the interaction of early human societies with their environment, as regards early mining and smelting.

Mots clés: Pollution; Lead isotopes; Peat deposit; Atmospheric deposition; Mining; Smelting

Domaines: Géographie

Fabrice Monna, Didier Galop, Laurent Carozza, Magali Tual, Argitxu Beyrie, et al.. Environmental impact of early Basque mining and smelting recorded in a high ash minerogenic peat deposit. Science of the Total Environment, 2004, pp. 197-214. ⟨halshs-00759153⟩