The Basque-Cantabrian Basin is an area of 250 x 100 km located in the extreme west end of the Pyrenees Mountains. It is a Mesozoic and Tertiary sequence on a Hercynian (Devonian-Carboniferous) basement and the stratigraphic colum shows continuous series of sediments from the Permo-Triassic through the Tertiary, reaching a thickness of 15,000 metres, including evaporites, carbonates, clastics and volcanics.