Schwermetalltiefengradienten in Auensedimenten der Selke als Ausdruck der historischen Montanwirtschaft im Ostharz

Abstract

DOBLER, L.: Vertical gradients of heavy metals in floodplain sediments of the river Selke as indicator of ancient mining activities in the Eastem Harz Mountains.- Hercynia N.F. 34 (2001): 171- 186. The beginnig of mining activities in the surroundings of the local mining centre in the Eastern Harz Mountains is unknown. First indications are from the late 8th century. Relative highdays of historical mining activities are known from about 1450 AD until1618 AD and from about 1700 AD until1765 AD (Straßberg) and 1903 AD respectively (Neudorf/Harzgerode). Until 1765 AD mining for silver ores and Galenit was most important and in the following decades iron ores (Neudorf, Tilkerode) and feldspar became dominant. Geochemical investigations and datings 14C) between Güntersberge and Meisdorf showed that horizontal and vertical patterns of heavy metal contents, especially lead, reflect local mining history. Upstream of Agezucht creek loamy grey sediments (Graulehme) are nearly unaffected by mining, downstream heavy metal contamination is severe and worst between Straßberg and Alexisbad/Mägdesprung. Here mine tailings from processing plants near Straßberg were deposited over older grey sediments until the beginning of the 20th century. High metal concentrations in old grey sediments indicate that mining was at least activ since the late middle ages (13th century) and might have already begun in the early middleage (7th century). Similar results are known from the western parts of the Harz Mountains. After cessation of mining activities typical brown floodplain sediments derived from the catchment area of the River Selke were deposited over the mine tailings. In the youngest sediments concentrations are still high because of mixing with older contaminated sediments and recent input of copper-rich fluid waste from a feldspar mine near Straßberg (active until 1990). Towards the margin of the Harz Mountains heavy metal concentrations decrease and the maximum shifts towards the younger sediments.