Xabier Orue-Etxebarria (a), Aitor Payros (a), Fernando Caballero (a), Estibaliz Apellaniz (a), Victoriano Pujalte (a) & Silvia Ortiz (b)
(a) Department of Stratigraphy and Paleontology, Faculty of Science and Technology, University of the Basque Country (UPV/EHU), Ap. 644, E48080 Bilbao, Spain. E-mail: xabi.orueetxebarria@ehu.es
(b) PetroStrat Ltd, Tan-y-Graig, Parc Caer Seion, Conwy, LL32 8FA, Wales, UK.