Let’s make a mess, maybe no one will notice. The impact of bioturbation activity on the urn fill condition

The research was carried out at the cremation cemetery of the Lusatian culture in Wtórek, Ostrów Wielkopolski district, Wielkopolska province, Poland. Contrary to the so-far-studied topics related to the CT imaging of burnt bones and their virtual exploration, we concentrated on the analysis of the structures formed by the soil fauna activity in the fills of urns and additional vessels, and reconstruction of the dynamics of the ecosystem variability within the cemetery area based on thereof. We also demonstrated the impact of macrofaunal activity on stratigraphy and bone fragmentation. From the total of 222 excavated burials in 18 urns and one additional vessel, the remains of macrofauna or its bioturbation activity were identified. Out of 19 vessels subjected to CT examinations, traces of macrofaunal activity were demonstrated in 13: in five vessels animal bioturbative activity was not observed and in one, observations was impossible (due to significant metal-related artifacts). In two vessels both macrofaunal remains and traces of activity were identified. Discovered bioturbations were associated with specific species or genera. Nests or their parts of the genus Geotrupes sp. beetles were the most frequently observed traces of macrofaunal activity. Tunnels and aestivation chambers of earthworms and chambers of the genus Harpalus sp. beetles filled with Setaria sp. caryopses were discovered. The chitinous parts of other insects and the humerus bones of the vole of the genus Microtus sp. were also identified. It was shown, especially due to the non-destructive method, that rodents activity had the most destructive effect on the bone stratigraphy as well as on the movement and fragmentation of the burnt bones. The chances of visualizing bioturbations decreased with time since their creation. The process of disappearance of traces of macrofaunal activity concerned both traces of rodent activity and nests set up by Geotrupes sp. and other species.