Cement stratigraphy: Image probes of cathodoluminescent facies

Abstract

Cement stratigraphy of carbonates aims to establish the chronology of processes involved in the rock diagenesis. Regional cement stratigraphy allows correlations and understanding of the petrological heterogeneities in reservoirs and aquifers, but is a long and rigorous approach. This article exposes a methodology of image analysis that facilitates the spatial correlation of diagenetic events in carbonate rocks. Based on the statistical comparison of signals extracted from the red spectrum emission of cathodoluminescence digital images, it gives via crosscorrelation a measure of similarity (values scaled from minimum -1 to maximum 1) between two cathodoluminescence facies. Cementation events and diagenetic chronologies can thus be quickly correlated without the support of a full chronology, the model normally established on cement morphologies, petrological analyses and cathodoluminescence zonation sequences. A case study from two Upper Kimmeridgian Mount Salève outcrops (France) illustrates this methodology. Their diagenetic sequences recorded in cathodoluminescent cements are presented and being compared. The final statistical similarity between the two outcrops reaches an index of R = 0. 78. This result is sustained by petrological and geochemical analyses such as alizarine-ferricyanure stained thin sections, X microfluorescence mapping of elements, and microthermometry of fluid inclusions. © 2011 Swiss Geological Society.