Chert from the Vegamian Formation: A new raw-material supply source in the Cantabrian Mountains (NW Spain) during prehistory

This work provides the keys to the mineralogical and geochemical characterization of black chert from the Vegamian Fm. This formation crops out throughout the whole of the Cantabrian Zone (of Palaeozoic age), one of the geological zones of the Cantabrian Mountains (NW Spain). The geographical distribution of this formation is very wide, surfacing in the provinces of Leon, Asturias, Palencia and Cantabria. This variety of chert had been included within the group generically known as 'black chert', a macrogroup including different types of chert that appear in different Palaeozoic formations in the area and which share a characteristic black colour at the macroscopic level. The characterisation presented here has enabled us to distinguish it from other varieties. In this study, Vegamian chert has been divided into two different groups depending on their textural, mineralogical, geochemical and thermal propierties. Type 1, the most suitable for knapping, is characterized by high content in silica (>97%), laminated matrix and, occasionally, ghost of radiolarians. In addition, the characteristics specific to this chert make it suitable for lithic knapping processes. To confirm its use by prehistoric populations, this chert will be compared to that found in two Mesolithic sites, the caves of La Una and El Espertin (Leon, south versant of the Cantabrian Mountains), the raw materials from which are currently under study.