After the sedimentological description, the mineralogical and geochemical investigations provide further data about the depositional and diagenetic environments of deep-lying pelagic sediments. In particular, when applied to the clays and the trace elements they have absorbed, and provided that their value is enhanced by statistical methods, they are found to be quite suitable to the determination of the various, complex, combined and sometimes antagonistic influences that affected given sediments. Both investigational means are much more efficient when applied simultaneously: through a good knowledge of the relations between mineralogical and chemical compositions, when acquired in some propitious circumstances, it becomes possible in other cases when the latter alone is known, to assess the former. This is one of the ways by which, in this work, the study of Atlantic series has been helpful for the understanding of Alpine series