Correlation plots showing the relation of the raw material spectrum’s shift from fine-grained non-local materials towards coarse-grained local quartzite to the percentage of heat-treated silcrete.

(a) By contexts (CT) and (b) by (sub)groupings. The non-local fine-grained / local coarse-grained materials ratio is calculated as the addition of the percentages of chert and DWS/hornfels divided by the percentage of quartzite in each context. Heat-treated silcrete percentages refer to the number of silcrete artefacts in the contexts. The coefficient of determination of the correlation is r2 = 0.823, p = 0.005 for (a) and r2 = 0.921, p = 0.040 for (b).