Discrete clay diagenesis in a very low-permeable sequence constrained by an isotopic (K–Ar and Rb–Sr) study

摘要: Multimethod analyses of several size fractions clays were used to reconstruct the diagenetic history shallow buried claystones within Paris Basin. A systematic decrease occurred in K–Ar dates relative clay fractions, signifying higher amounts newly formed material finer fractions. We suggest that authigenic minerals occurring fine had an Al-montmorillonite composition. By assuming isotopic and Rb–Sr obtained on a bentonite layer sedimentary sequence stand for pure, minerals, one may interpret all as mixtures two detrital end-members. The results imply period low sea level favoured smectite-type formation about 10–15 million years after deposition sediments. Signatures limited-scale chemical homogenisation mean rock volumes affected by modifications be quite limited. study extracted from some stylolites further suggests any overpressure related origin no effect authigenesis.