Characterization of Gallo-Roman roads in northern France using micromorphological methods

The road network plays an important role in the birth and evolution of town planning and structuring of the landscape. It presents unique and original dynamics that encompass both its status and uses. Whatever their reality in the field, stratigraphic sequences are poorly studied using geoarchaeological methods. To document the formation processes of these road networks, micromorphological analyses were undertaken on a street in a Roman secondary town, Sains-du-Nord, on a road in a Roman civitas capital, Metz Divodurum, and on a lane created in medieval times in Lieusaint. Analyses of the Sains-du-Nord street and the Paille-Maille (Metz) road revealed intense vehicle traffic where traffic-related repairs and traffic layers were differentiated. Analyses of the Lieusaint site, enabled specialists to characterize the processes and layers resulting from vehicle traffic. Pedofeatures linked to passage and traffic presented in this paper, can be used to identify such types of space in other case studies. Finally, results show that the use of thin sections of archaeological layers can reveal not only the surface history, but also the original characteristics of traffic circulation space. The microscopic sequences are presented here as descriptive models of formation processes. The monophasic model appears to be the result of ongoing maintenance attributable to the status or continued use of the street (Sains-du-Nord) or lane (Lieusaint). Polyphasic and polycyclic models reflect rhythmic use and allow reconstruction of traffic levels (Paille-Maille (Metz) road).