High data density electrical resistivity tomography survey for sediment depth estimation at the Romuald's Cave site

Electrical resistivity tomography (ERT) surveys were conducted at the Velika Pecina near Klicevica and Romuald's Cave sites in Croatia in 2014 and 2015. The goal of the surveys was to estimate sediment depth to bedrock. However, neither survey produced reliable results at the 0.5 m probe spacing. In 2017, the Romuald's Cave site was revisited utilizing a high data density survey of 0.1 m probe spacing. All three surveys were conducted with a GeoScan RM85 in a pole-pole configuration. The high data density survey produced reliable results given the subsurface information available from three excavation trenches in the first chamber of the cave. The 2015 and 2017 ERT survey results are presented along with the results from two additional high data density ERT surveys located in the back chamber of Romuald's Cave. These results suggest that utilizing high data densities may improve the reliability of ERT surveys in cave environments.