Variability and sampling strategy of cave wall concretion: Case study of the moonmilk found in Leye Cave (Dordogne)

Cave Art is a fragile testimony of past human societies and the development of modern behaviours. In limestone caves, moonmilk commonly endanger the artworks. It is a calcite deposit with a large variability of chemical composition and morphological structures and it hosts numerous microbial communities. The possibility to characterize this deposit in the field would aid in a better understanding of cave behaviour and allow the setting up of proper conservation measures. The present study analyses the variability of a moonmilk strip of metric size in Leye Cave in the Vézère Valley (Dordogne, France). The cave was not ornate and was selected as a laboratory cave in which in‐situ observations and micro‐sampling could be carried out, before they were performed in cavities hosting parietal artworks. Scanning electron microscope (SEM) observations of 24 samples allowed, for the first time, an investigation of the variability of moonmilk deposits over the same wall of a few metres dimension. The observations highlighted the low variability of the moonmilk at the microscopic scale when regarding the chemical composition and morphological structures, despite significant macroscopic diversity, thus providing insights into how to optimize the sampling strategy of moonmilk in ornate caves.