Preliminary structural and chemical study of two quartzite varieties from the same geological formation: A first step in the sourcing of quartzites utilized during the Mesolithic in northwest Europe

Wommersom and Tienen quartzite are found as varieties of lithified arenite banks within the Cenozoic Tienen Formation. These macroscopically distinct varieties were utilized as raw material for stone tool production during the Mesolithic period in the Rhine-Meuse-Scheldt area of northwest Europe. They were distributed over 80,000 km² between the Paris and North Sea basins for over four millennia. This distribution has been interpreted by archaeologists as a long-distance exchange network. In this work, samples from both outcrops have been examined by different characterization methods with the aim to develop an operator-independent and objective method to determine the origin of a certain artifact. Petrographical study revealed a distinct difference in grain size of both quartzites. However, considering the results of the petrographical analyses, it is clear that there is a difference between the accessory minerals that are more or less irregularly distributed in the samples. Cathodoluminescence (CL) revealed additionally information on the presence of feldspars and facilitated the recognition of minerals such as apatite, zircons and kyanite. X-ray tomography was used to obtain in a non-destructive way, a structural overview of the samples as well as a detailed 3D grain-size distribution of some accessory minerals. The latter is important given that these nondestructive techniques could be used for sourcing of other geological material as well as archeological artifact. This work is a first step in the sourcing of different quartzite varieties to their different outcrop locations and their specific facies within the same geological formation. However, when characterizing artefacts for sourcing purposes, it will remain crucial to provide attention towards a possible level of heterogeneity inside these samples. In order to do this correctly, besides a characterization of the artefacts themselves, also a detailed analysis of the entire geological formation is needed.