Evolution of the Basco-Cantabrian Basin, Northern Spain

Owen Vaughan

The Basco-Cantabrian basin (BCB) stretches for 150 km west from the Pyrenean system and displays a complex subsidence pattern through time, involving Triassic faulting, Jurassic quiescence, Cretaceous faulting and subsidence, followed by Tertiary compression. Its southern margin is rimmed by a narrow (40 km wide) Tertiary basin, deeper in places than the coeval Ebro basin in the southern Pyrenees, but lacking any driving load. This Tertiary Cantabrian basin may reflect the interaction between thermal subsidence phases at the southern margin of the BCB and uplift (inversion) of the Mesozoic basin to the north.

In addition, the BCB shows a number of interactions between thin-skinned and thick-skinned styles of shortening. In the west, inversion has uplifted a major basement ridge between areas of vastly differing sedimentology and structural style. The southern thrust margin to the basin has no basement outcrops, even though it marks the southern margin of Mesozoic sedimentation. Balanced sections imply the reactivation of basement faults in controlling the geometry, position, and orientation of the thrust front. In the northern part of the BCB, around Bilbao, major monoclines and thrusts follow basement fault trends--trends which earlier strongly affected the distribution of the Mesozoic.

The BCB has a stratigraphy and structure in common with eastern basins such as the Aquitaine and Ebro. Though it can be difficult to correlate individual structures, many features of basin dynamics are similar. It is valuable to study the less-deformed BCB in order to understand the basins of northern Spain and southern France.

AAPG Search and Discovery Article #91032©1988 Mediterranean Basins Conference and Exhibition, Nice, France, 25-28 September 1988.