Publication: Clay minerals as provenance indicators in
continental lacustrine sequences: the Leza
Formation, early Cretaceous, Cameros
Basin, northern Spain
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2005
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Blackwell Scientific publications
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Abstract
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. Chlorite composition and illite KI values indicate that these minerals were formed
at temperatures higher than those reached by the Leza Formation which indicates its detrital origin.
The similarity in the Mg-chlorite composition between the Arnedillo lithosome and the Keuper
sediments of the area indicates that these materials acted as a local source area. This implies that
Triassic sediments were exposed, at least locally, at the time of deposition of the Leza Formation.
The presence of smectite in the Leza Formation is related to a retrograde diagenesis event that altered
the Mg-chlorites in some samples.