Identifying fossil cave entrances with ERT at Sierra de Atapuerca caves (Burgos, Spain)

Abstract

The Sierra de Atapuerca sites (Burgos, Spain) consist of various caves filled with sediments that bear outstanding archaeo-palaeoanthropological remains (Bermúdez de Castro et al., 1997; Carbonell et al., 2008; Ortega et al., 2014). Indentifying the development of this multilevel karstic system is therefore crucial for understanding these sites formation processes as well as for excavation planning strategies. To this end, geophysical prospection has already been applied at Sierra de Atapuerca, revealing interesting information that has been verified by test pits. In particular, the ERT (Electrical Resistivity Tomography) method has proven to characterize this karst environment successfully, especially because of the high resistivity contrast that exists between the sediments that fill the caves and the limestone host rock (Ortega et al., 2010; Bermejo et al., 2017). In this work, we present the results of the systematic ERT surveys carried out for the last years over all the passable areas of the range that contains this karstic system and in relation to all of its levels. More specifically, we present the profiles related to ancient cave entrances. All these entrances have in common to be filled with sediments and covered by vegetation, fact that makes them indistinguishable in the field. The location of some of them has been possible thanks to previous topographic and geomorphological studies, whereas the rest were unknown to present. The interpretation of these 2D ERT profiles has allowed indentifying the geometry of 3 known entrances. Besides, these profiles have unveiled the location of 3 other unknown entrances and their morphologies.