Life cycle of a moat: A detailed micromorphological examination and broader geoarchaeological survey at the late Neolithic Wadian site, Central China

Moats and rammed earth walls are two key criteria considered by many archaeologists as the universal characteristics of late Neolithic 'cities' in China. However, archaeological evidence of their construction and maintenance remains ambiguous. We investigate the taphonomical and functional issues of the moat excavated at Wadian in Central China by conducting a detailed micromorphological examination of soil samples. The construction of this moat coincided with high groundwater table and the initial stage of its use benefited from this favorable hydrological condition while it was still connected with natural water bodies. However, the moat gradually silted up due to increased cultural activities, changing sedimentary processes, and fluctuating hydrological conditions at the site. The frequent alternations between wet and dry conditions dominated the last stage of the life cycle of the moat and it probably lost its original functions at this stage before it was completely silted up. Such changing sedimentary regime and fluctuating hydrology were confirmed by our geoarchaeological survey in the region. Our research provides crucial information concerning the construction, maintenance and abandonment of this moat and how these processes were related to subsistence strategies and local environmental changes.