Remarkable flysch formations of Deba, Basque Coast Geopark, Basque Country, Spain. Flysch formed at the end of the Mesozoic era in the Cretaceous - flyschs are formed by sediment accumulation following repeated submarine avalanches, due to earthquakes, and producing after compaction and crystallization very regular layers of sandstone and limestone here recovered by Pyrenean orogeny and released by erosion.