Variations in clay mineral assemblages, changes in KuÈbler index (KI), and the
chemical composition of chlorites are used to identify source areas in the lacustrine materials in the
Lower Cretaceous Leza Limestone Formation of the Cameros Basin, northern Spain. This formation
has fairly homogeneous lithological characteristics and facies associations which do not allow for
identification and characterization of local source areas. The Arnedillo lithosome of the Leza
Limestone Formation contains a clay mineral association (Mg-chlorite, illite and smectite) indicative
of its provenance.