Cathodoluminescence and metamorphism in rudist shells from the Upper Cretaceous marbles of Menderes Massif (Western Turkey)

Resumen

Radiolitid rudist shells from the Upper Cretaceous marbles in the southern sector of Menderes Massif (Turkey) have been studied under cathodoluminescence microscopy (CL). The background of equant calcite mosaic appears non-Iuminescent, and only some scarce relicts of growth lines and walls are red and yellow-Iuminescent. CL observations allow us to think that the Upper Cretaceous marbles of the Menderes Massif were completely homogeneized through high-pressure metamorphism during the Alpine history that led to a strong recrystallization to non-luminescent ferroan calcite. After this process, the "honeycomb" microstructure still remains ill-preserved as some isolated patchs. From our previous observations in bivalve shells from the Middle-to-Upper Cretaceous of the Basque-Cantabrian Region (northern Spain) we think that, in spite of metamorphism, luminiscence survives restricted to the shell parts which originally could host a more dense concentration in organic matter.