In Search of the Bartonian (Middle Eocene) GSSP (I): Potential in the Basque–Cantabrian and Aquitanian Basins (Western Pyrenees)

The Global Stratotype Section and Point (GSSP) for the base of the Bartonian (middle Eocene) stage is as yet undefined. Herein we assess the GSSP potential of the successions found in the Basque–Cantabrian and Aquitanian basins (western Pyrenees). On the basis of the available data, no outcrop in the Biarritz and Pamplona areas fulfilled the requirements outlined by the International Commission on Stratigraphy. However, the succession exposed on the eastern side of the Cape of Oyambre (San Vicente de la Barquera, province of Cantabria, northern Spain) did so, and yielded positive preliminary results.