Soil investigations to determine the function of different areas within the Roman fortress near Hermeskeil (Germany)

The area of the Hermeskeil main camp, built by the Roman army during Caesar’s Gallic Wars, is subdivided by an internal fortification consisting of a ditch and bank and separating a larger southern from a smaller northern part of the fortress. Our study deals with possible functional differences between these two parts of the temporary camp since both a separate stationing of potentially mounted auxilia and a secondary reduction of the camp’s surface could explain the building of such internal defences. An intensive soil survey was undertaken in the northern part of the main camp to delineate areas of high human activity. We conducted a mapping of 128 drill cores. Multi-element analyses and their statistical evaluation succeeded in isolating anthropogenically influenced areas, which were, however, located exclusively in the intervallum, i.e. the space immediately behind the camp’s ditch and bank that was left free of housing regular troop quarters. Samples in this area also showed a high coprostanol/cholestanol and a low 5β-stigmastanol/coprostanol ratio, indicating faecal matter from omnivores. Biomarker analyses do not indicate that horses and, therefore, auxilia were present in the northern part of the main camp, but the ratios of individual biomarkers rather speak in favour of the existence of latrines in the intervallum. Accordingly, the northern part of the Hermeskeil main camp was probably used for the regular stationing of infantry. The building of an internal fortification, therefore, most probably relates to a secondary reduction of its surface, which was connected to a phase of re-use.