Tracing modern environmental conditions to their roots in early mining, metallurgy, and settlement in Gladhammar, southeast Sweden: Vegetation and pollution history outside the traditional Bergslagen mining region

We present results from a multidisciplinary project using lake sediment as a natural archive in combination with archaeology to investigate the earliest history of the Gladhammar mining area, southeastern Sweden. The aim was to identify and trace human impacts on the landscape, specifically in connection with settlement and metal production. Sediment records from two lakes linked to different processes in metal production were analyzed; Tjursbosjon down-slope of the mining area and Hyttegol situated downstream of an excavated blast furnace, 1.8 km from the mines. The sediment analyses included multi-element geochemistry (WD-XRF), stable lead isotopes, pollen, and charcoal. Although historical documents record activities beginning in AD 1526, the archaeological study found indications that mining and metal production likely predated this period. The known historical period is well reflected in the sediment records, such as a 500-fold increase in copper, stream erosion, loss of forest cover and an expansion in agriculture. More importantly, already in the 12th–13th centuries, there was a 2- to 10-fold increase in lead, copper, and charcoal particles and evidence of erosion linked to the establishment of a blast furnace. Lead isotopes reveal a change from natural conditions to an input of lead from regional ores as early as the 9th–10th centuries. Settlement in the form of agriculture can be seen from 2000 BP. This sediment evidence of early mining or metallurgy during the 9th–15th centuries is supported by a few radiocarbon dates from the excavated mining fields, which on their own were considered as vague or improbable outliers by archaeologists.