"Outstanding Paleozoic ichnofossils from Cabañeros National Park (Central Spain) and large casting processes for the preservation of Geological Heritage"

Abstract

Outstanding trace fossils preserved in Cambrian and Ordovician sandstones constitute part of the geological heritage of Cabañeros National Park (CastillaLa Mancha Region, Central Spain) which has thousands of visitors each year. The lower Cambrian record is represented by the ichnogenus Astropolichnus, occurring as convex hyporeliefs, even preserving the central cylinder, or as concave epireliefs on rippled surfaces of the Azorejo Formation (GutiérrezMarco et al., 2015). Overlaying the Toledanian angular unconformity, the lower Floian “Intermediate Beds” bear unique large burrows, measuring up to 1160 cm long and 20 cm wide, preserved as full-reliefs at the top of several quartzite beds and sometimes forming prominent loops. Further up in the section, the Armorican Quartzite yield abundant traces of the Cruziana and Skolithos ichnofacies. Among them stands out a large bedding plane covered by “rusophyciform”-like Cruziana hyporeliefs, which may reflect a massmating event by their producers. Finally, the same beds yielded a very large burrow (45 cm wide) of a still unknown trace (Gutiérrez-Marco et al., 2010). In order to preserve and study these astonishing bedding planes, we made two large casts measuring up to 13.4 m2 . The concentration of a very wide Cruziana required the use of thixotropic agents on the moulding silicone and on the polyester shells prepared on-site. The resulting casts were made of epoxy resins, strengthened with woven and non-woven fibreglass fabrics and epoxy rebars, and coloured with mineral pigments (Baeza et al., 2013). The replica of Cruziana is the second largest single-piece cast in the world in the field of invertebrate paleoichnology, and is housed in the main Interpretation Centre in Cabañeros National Park as a permanent exhibition.