Zwarte vuurstenen uit het Midden-Paleolithicum in Nederland
Black Middle Paleolithic Flints in the Netherlands. Several Middle Palaeolithic sites producing artefacts with mainly black patina in the central Netherlands are discussed. Most of these artefacts derive from river deposits of the Kreftenheye Formation and have mainly been recovered by suction dredging. The black patina consists of a compound of iron and sulphur and was produced by sulphate-reducing anaerobic bacteria. It is suggested that the development of this patina is associated with a braided river system, and that these finds will date especially from the Eemian and/or the Early or Middle Weichselian (130,000–40,000 years ago). In cultural terms, they can be placed in the Mousterian or in some cases in the Keilmesser Gruppen. It is probable that the important Middeldiep site in the North Sea, which has yielded more than ten handaxes, belongs to the same group; this site also produced a skull fragment of a Neanderthal. Artefacts of the Rhenen Industry in the central Netherlands derive from much older river deposits, of the Urk Formation, and are dated to a warm phase within the Saalian Complex (probably 250–200,000 years ago). These artefacts are mainly patinated brown, probably because the gravelly layers in which they were embedded were laid down by a meandering river system.