Age and Origin of Albian Glauconites and Associated Clay Minerals Inferred from a Detailed Geochemical Analysis

Clay mineralogy, organic carbon burial, and redox evolution in Proterozoic oceans

“…The precursor may form as an intermediate phase during early diagenesis and glauconitization, or it may be composed of detrital material that reacted with ambient chemistry in the sediment. Nevertheless, the origins of glauconite most clearly represent specific physical/chemical conditions (i.e., reducing, seawater K diffusion and low sedimentation rate) during early diagenesis (Velde, 2003;Rousset et al, 2004). In our samples, smectites are essentially undetectable; however, a major fraction of 1M/1M d illite in our samples probably represents the transformation of pre-existing smectite and/or kaolinite in the original clay assemblage.…”

“…2). Glauconite is generally thought to form by the recrystallization of a precursor material (usually Fe-rich) under typically reducing conditions, and this reaction must occur near the sediment-water interface in contact with seawater derived K to allow K 2 O incorporation and the formation of glauconitic mica (Rousset et al, 2004;Meunier and El Albani, 2007). The precursor may form as an intermediate phase during early diagenesis and glauconitization, or it may be composed of detrital material that reacted with ambient chemistry in the sediment.…”

Influence of local fluid flow on properties of low permeability Cretaceous siltstones (South-Eastern France): Implications for a nuclear waste deep repository

“…It consists essentially of illite-smectite Rousset et al (2004). mixed layers (I-S), enriched in smectite layers, and mixed with illite/micas and accessory kaolinite and chlorite.…”

“…A preliminary investigation of the diagenetic history of this sedimentary succession, based on the mineralogy, the morphology, and the chemical and isotopic compositions of the clay mineral components (Rousset et al, 2004), indicated that glauconite was evolved enough to allow accurate age determination. Potassium-Argon (K-Ar) and Rubidium-Strontium (Rb-Sr) dating of the glauconite yielded an age of sedimentation of about 98 Ma.…”

“…Assuming that the diagenetic pyrite formed during very early diagenesis in the sequence (c. 97-98 Ma based on glauconite dating [Rousset, D., Leclerc, S., Clauer, N., Lancelot, J., Cathelineau, M., Aranyossy, J.F., 2004. Age and origin of Albian glauconites and associated clay minerals inferred from a detailed geochemical analysis.…”