Search for geochemical indicators of pre-urban habitation sites: case study from the Skomantai hill-fort and settlement, western Lithuania

Abstract

Thermoluminescence dating of potsherds found in the Skomantai hill-fort and settlement areas in western Lithuania confirms that they were fired from the 4th to the 10th century and historical human activity existed at Skomantai. The aim of this research was to investigate the relationship of chemical elements with total organic carbon and total inorganic carbon and distinguish possible anthropogenic indicators in the study area which is characterised by sandy sediments and wooden construction. Twenty-six chemical elements were determined by EDXRF. Two groups of possible anthropogenic indicators were distinguished: Ca, Zn, Mn, Cu, Ba, P and S, Pb, Br, Cl. All of them are significantly positively correlated with total organic and inorganic carbon. The enrichment factors of possible anthropogenic indicators were calculated based on the local background concentration of sand. Elevated enrichment factors in topsoil indicate regional and local anthropogenic influence; in the layer at 20–50 cm depth they give evidence of historical human activity. The descending sequence of their average enrichment factors in the latter layer of the hill-fort and settlement areas is as follows: S(18.7)> P(7.0)>Cl(4.3)>Mn(4.2)>Cu(3.8)>Zn(3.3)>Br(2.4)> Ca(1.8)>Pb(1.7)>Ba(1.1). The additive index of group S, Pb, Br, Cl is much higher than the additive index of the group Ca, Zn, Mn, Cu, Ba. However, the relative part of the additive index of the group Ca, Zn, Mn, Cu, Ba increases in the settlement area compared to the hill-fort.