Composite reflexion seismic line and its line drawing crossing the Basque – Cantabrian Pyrenees from south (left) to north (right) with nine boreholes and refraction seismic data projected. The surface geology and the main sedimentary successions of syn-extensional sediments and syn-compressional sediments are showed together with the main structures of the area. See the text and Appendix 1 for further details.