Glauconitization processes in the northwestern Mediterranean (Gulf of Lions)

Two sedimentary profiles, at IS kin and at 125 kin from the Rhone River mouth were selected to Study the steps of glauconitization inside green (glaucony) grains, in a temperate marine environment. The Proxima I site is characterized by a greater content of alpine minerals (chlorite, illite) than the distal one. In the proximal site, pellets at a Younger level demonstrate a largely inherited mineral composition. In the older level, representing the most advanced stage of glauconitization, there is a mixed-layer glauconite-nontronite (G-N) phase with 20% glauconite-80% nontronite in dark green grains. In the distal site, more evolved glaucony has LIP to 92% glauconite in the G-N. In spite of this difference, the glauconitization process developed similarly in the two sites. The relatively low Fe content in the mud-matrix does not reflect the concentration of this element inside the grains. During diagenesis, most of the inherited minerals disappear, making way for neoformed mixed-layer glauconite-nontronite.