Grain-size analysis and quartz surface microtextures observations of sediments from Jijelian East coast, Algeria: sedimentary environment implications

This study aims to enrich the information on sedimentary dynamics along the Algerian coastline through an investigation on the Eastern part of the Jijel embayment. On this coast, sediment samples were collected on the El Kebir wadi bed, and on beach and dune zones. Grain-size analyses were performed by Laser Diffraction. Also, a morphoscopy analysis of selected quartz grains was conducted with a binocular magnifying glass, while the surface textures of quartz grains were observed with a scanning electron microscopy (SEM) equipped with an EDAX microprobe. Granulometric data indicate a decrease in sediment size from upstream (M-z < 1 phi) to downstream of the wadi (M-z > 1 phi) and a high-to-moderate transport medium energy conditions. The beach sands are medium to coarse, moderately to well sorted, and primarily fall into the mesokurtic to leptokurtic ranges, revealing high-energy pulsating conditions in shallow marine water. Current dune sands are generally medium-grained, moderately to well sorted, negatively asymmetric, and mesokurtic to very leptokurtic range. Old dune sands, instead, are fine to very fine with a diameter of 2-4 phi. SEM observations show different types of grain surface microtextures relative to their depositional environments. Those distinguished related to fluvial, marine, and aeolian agents of depositional environments. According to the path of sediment transport, the grains are mostly angular and sub-angular in the wadi bed, rounded and sub-rounded along the beach, and rounded in the dune field. The beach sands were relatively coarser than those of the upper beach and old dunes.