Geochemical impact of a bloomery : Tracing a bloomery furnace in peat records with geochemistry in central Sweden

Abstract: The aim of this study was to work out whether bloomery activities might have left a geochemical imprint in two mires close to a known bloomery and identify differences between the geochemical signals in the mires. Therefore two peat profiles (140 cm deep) and a series of bulk samples (composite of 10-60 cm) were taken near the remains of a bloomery close to Ängersjö, Hälsingland, which has one documented radiocarbon date of AD 1300-1435. One profile was taken in the fen closest to the bloomery, the other profile was taken close to a nearby lake. Geochemical analysis of the peat samples was performed with X-ray fluorescence spectroscopy (XRF). The results were combined with previously taken data from a sediment profile from the lake ~120 m away and a pollen profile close to the bloomery. The results showed that the activities of the bloomery were visible in the geochemical signals of the peat core closest to the bloomery with two peaks in Pb and Zn, which coincide with the previous reported times of operation (1. AD 1030-1060; 2. AD 1300-1435), which also fits with the pollen record from the nearby peat record. The mire close to the lake, which is hydrologically not connected with the area where the bloomery was, did not show these increases in elements associated with iron processing and only a small peak of Pb was visible. Furthermore, the geochemistry of the bulk samples showed that a disturbance of the mire surrounding the lake was responsible for the geochemical changes observed in the lake,particularly as a source of increases in inferred biogenic Si observed in the sediment record (as increased Si/Al ratios) in association with human-related disturbance in the sediment record during AD 800-1200. Si concentrations in the bulk peat samples in the fen adjoining the lake range as high as 14% (≤23% as SiO2).