Petrographic and mineralogical study of the beach rocks of Souiria Laqdima coast, Morocco

Abstract

Beach rock is an interesting and distinctive formation, especially in contrast to other types of rock formations. There is a geological formation that is very similar to this one in the Moroccan province of Souiria Laqdima which is located on the coast of the Atlantic. Given the lack of previous research and studies on this topic in Morocco, the objective of this project is to investigate and identify a selection of the beach rocks that can be found along the Atlantic coast. For that, some beach rock samples were collected along the shore of Souiria Laqdima located close to the mouth of Oued Tensift and then to go for quantitative mineralogical investigations namely XRD and XRF analysis. The diffraction spectra demonstrate the presence of components that were formed as a consequence of erosion in the hinterland. These elements include quartz, feldspars, ferromagnesians, some calcite and other phyllosilicates. Calcite, aragonite and magnesian calcite are all inherent elements; as a result, they are considered to be marine elements. Most of the clay minerals have a continental provenance and a detritic origin such as kaolinite, illite and chlorite; however, a specific percentage of these minerals has a diagenetic origin in this marine environment. The examination with X-ray fluorescence reveals the existence of both quartz and feldspar. However, it also contains a significant amount of calcite and even some magnesian calcite. The petrographic study allowed us to determine, first, the nature of the cement in the beach rocks which was found to be calcite and magnesia calcite in the majority of the samples and secondly, the traces of bioturbations as well as the action and contribution of the burrows, on the fixing of the pebbles and on the cementing of the beach rocks.