Geochemical provenance analyses of Roman lava millstones north of the Alps : a study of their distribution and implications for the beginning of Roman lava quarrying in the Eifel region (Germany)

In Roman times, rotary querns and different types of millstones, driven either by horse-capstan or water power, were produced in the lava quarries of the quaternary volcanic Eifel region and exported to many parts of the Empire. The geographic distribution of Roman lava millstones from the Eifel region provides important information about trade patterns and, in cases of well dated millstones, also allows an estimate as to when the Roman lava quarrying in the Eifel region began. Sixty-two millstones from Germany, France and Austria were sampled and analyzed for major and trace elements by X-ray fluorescence. To determine their provenance, the millstone data was evaluated by a combination of geochemical discrimination and cluster and discriminant analyses using an extensive and detailed database of all Roman lava quarries in the Eifel region. An Eifel provenance could be confirmed for forty-four artefacts and, furthermore, determined down to the exact lava flow. The affiliation of the other artefacts to other possible regions where millstones of comparable lava were extracted was carried out on the basis of geochemical data from the literature. However, because of insufficient data, only assumptions about the regional provenance can be made. The origins of the other finds are assumed to be the Vogelsberg region, the Massif Central, Orvieto, and, possibly, the Pannonian Basin. A preliminary map of the distribution of Eifel millstones in Roman times based on these data is presented; the beginning of Roman lava quarrying can be constrained to 8e7 BC