Cathodoluminescence and cement stratigraphy in Middle Cretaceous rudist shells (Hippuritacea, Bivalvia) from Ereño (Bizkaia, Basque Country)

The cathodoluminescent behaviour of rudist shells and coral skeletal fragments from Ereño Urgonian limestones has been studied. Two different models of luminescence have been distinguished in rudist fragments. Whereas requieniid shells show luminescent patterns that moderately coincide with growth lines, the caprotinid ones exhibit more spread luminescent areas. The interprismatic lines control the lateral spreading out of luminescence. Since some caprotinid shells seem to have their interprismatic lines locally opened by tectonic deformation, luminescence progresses here more clearly. A complex cement stratigraphy has also been deduced, including vadose, meteoric and burial events. The cement sequence ranges from «dogtooth» non-luminescent calcite to yellow hair-line calcite to «blocky» calcite having a complex luminiscence pattern. This sequence appears infilling relatively-early fractures in shells, interprismatic spaces in caprotinid shells, «honeycomb» cells in radiolitid shells, moulds originated from selective dissolution ofaragonitic scleractinid corals, and interlamellar spaces in Chondrodonta sp. valves. The same sequence is recorded as aggradational neomorphism upon micrite that infilled the moulds produced by very-early selective dissolution of aragonitic hipostraca of caprotinid