Comparative mineralogical and geochemical clay sedimentation in the Betic Cordilleras and Basque-Cantabrian Basin areas at the Cretaceous-Tertiary boundary

The mineralogy and geochemistry of the bulk rock and clay fraction of sediments deposited at the CretaceousTertiary transition and in the KTB layer have been investigated by various methods in two sections from the Betic Cordilleras (Agost, Caravaca) and five sections from the Basque-Cantabrian Basin (Monte Urko, Sopelana, Zumaya, Hendaye, Biarritz). Active terrigenous supply prevailed in both regions during the latest Maastrichtian and earliest Paleocene. Very different clay associations occur in the regions, smectite being dominant to the south and illite to the north. The Betic Cordilleras series mainly reflects climate and weathering conditions, as well as volcanic activity, with the KTB layer displaying a specific source and diagenesis control expressed as increased amounts of smectite. The sequences cropping out in the Basque-Cantabrian Basin mainly reflect tectonic activity and burial diagenesis, the effects of which differ according to the palaeogeographical location. The clay sedimentation patterns in the North and South Iberian sections across the Cretaceous-Tertiary passage are controlled overwhelmingly by regional or local geodynamic and diagenetic phenomena. Thus any global, namely extraterrestrial, influence cannot be identified.