Geochemical mapping based on overbank sediments in the heavily industrialised border area of Belgium, Germany and the Netherlands

The geochemical distribution patterns based on overbank and stream sediments were studied in the border region of Belgium, Germany and the Netherlands. In total 34 sites were sampled over an area of approximately 16,000 km(2). Geologically the region comprises formations of the Palaeozoic Ardennes and Eifel, and the unfolded Mesozoic to Quaternary cover. Two overbank sediment samples were collected at each site; one from the lower part of the profile and another from the upper. In addition, samples of active stream sediment were taken from the same sites for comparison and complementary geochemical information, Geochemical distribution patterns for the lower overbank sediment samples reflect the natural situation, with lithology as the main influencing factor. Natural anomalous patterns, due to Pb and Zn mineralization, are also detectable. The upper overbank sediment clearly shows the influence of Pb-Zn mining and metallurgy, as well as other anthropogenic chemical contamination. Pollution is even stronger in stream sediment, obscuring almost completely the natural pattern. The results of these investigations demonstrate the applicability of overbank sediment as a sample medium in regional geochemical mapping. However, for an effective interpretation of the results a good knowledge of the sedimentological history and age of the sample sites is required in mining and industrial areas.