Clay Mineral Associations of the Quaternary Fluvial Deposits in Fez Area

The city of Fez is located in the north-center part of the Saïs Basin composed of marine sediments of Miocene age which have been submitted to regression during the Pliocene and Quaternary. This basin contains a Plio-Quaternary substratum consisting of deposits of lacustrine, palustrine, and fluviatile origin. This study aims to identify the associations of the clay minerals from these deposits in order to understand the paleo-environmental settings and the paleo-climate of the Quaternary. Several methods were used to analyze these clay deposits. X-ray diffraction (XRD) was performed on natural, oriented, and ethylene glycol-solvated specimens. Supplementary SEM and EDS analyses were performed for a detailed characterization of the clay minerals. The clay mineral assemblages of the studied area showed the dominance of smectite as the main clay mineral associated with kaolinite, illite, and palygorskite (2θ = 8.50°). This mineral is well visible on glycol-solvated X-ray pattern when smectite shifted to 5.2° 2θ (d = 16.9 Å). In addition, chlorite and non-clay minerals represented by quartz, calcite, iron oxides, sulfates, and ashcroftine were present. The dominance of smectite suggests a tropical to subtropical climate with high humidity where kaolinite formed. The presence of illite indicates short cold and desertic periods. The presence of palygorskite and ashcroftine in these fluviatile deposits represents new findings, which are likely connected to Triassic and Plio-Quaternary basaltic rocks.