Interdisciplinary characterisation and environmental imprints of mining and forestry in the upper Durance valley (France) during the Holocene

The upper Durance valley contains the largest silver–lead mines of the French Southern Alps. We investigated the characterisation and impact of these mining activities and associated forestry in the Argentière (L'Argentière-La Bessée) and Faravel (Freissinières) districts using a multidisciplinary approach that includes archaeological, palynological, geochemical, anthracological and dendrochronological studies applied to mining remnants and a peat bog (Fangeas, in the Faravel district). More specifically, we studied the occurrence of lead contamination episodes, the chronology of mining activities and their link to the evolution in woodland cover. Our chronology is based on mining archaeology, radiocarbon dating of about thirty charcoal samples and the dendrochronological analysis of more than 170 specimens of exhumed waterlogged wood. The anthracological analysis was established with more than 10,000 charcoals from firesetting. The main geochemical approach was based on the analysis of lead and its stable isotopes in sediment fractions from a peat core. The combination of palynological records and lead isotope imprints were used to characterise (i) a Roman contamination episode unknown to archaeology, (ii) the development of medieval mining activities and (iii) the reactivation of mining during the Modern period and the Industrial Revolution. Medieval mining coincides with an extension of the high mountain agropastoral areas. The in situ continuous human activities in the same industrial territory led to rational communal management of subalpine forests, but also to their parcelling that reached its peak in the High Middle Ages. Mining during the Modern period coincides with significant stress on woodland areas that also appears to be related to lumber and fuel timber production for shipyards (French Royal Navy) as well as the functioning of several military fortresses. The mining reactivation during the 19th c. matched public measures of forest protection that took shape in the afforestation programme of the uplands.