Effects of site lithology on geochemical signatures of human occupation in archaeological house plans in the Netherlands

This study presents the application of multi-element soil analyses (X-ray fluorescence spectroscopy and inductively coupled plasma optical emission spectroscopy of 1 M HCl extracts) to grid samples from 3 archaeological house plans embedded in sandy clays, clays and sands to assess effects of site lithology on geochemical signatures of human occupation. The results indicate that this effect is significant and that each house plan is characterized by enhanced concentrations of different sets of elements. Copper, Cr, Sn and Nd enrichments were found at all sites and thus represent elements that have no or only a weak relation with lithology. Depletions of Fe and Mn were also found to be universal indicators of human occupation in the house plans. A combination of off-site sampling, comparison to regional element background concentrations and the use of bivariate plots (Al vs selected elements) was successfully applied to identify anthropogenic elements, verify background element concentrations and element sources, and assess element distribution patterns within house plans. Spatial patterning of several anthropogenic elements suggest the presence of an in-house barn at two sites, while for another site no spatial patterning of chemical elements was observed. For two sites this contrasts with earlier archaeological interpretation. Our results further suggest that 1 M HCl extractable elements are unreliable indicators of human occupation in clayey and especially calcareous clayey soils. (C) 2009 Elsevier Ltd. All rights reserved.