Quaternary coastal sand dunes occur frequently along the Atlantic coast of Morocco and result from the combined effect of river discharge, littoral drift, winds, vegetation, and other meteorological conditions. In this paper, we investigate the textural and compositional parameters of the coastal dune sands of Essaouira across the Ksob riversides, as well as their provenance. Morphologically, they occur as present-day active dunes, Holocene fossil dunes and Pleistocene aeolianite deposits. To investigate the grain provenance, we have opted for laboratory analyses including grain size, mineralogy, microtextures, and micromorphology of quartz grains. Sands from Holocene fossil and active dunes revealed very fine to medium mean grain size and a moderate sorting, while those of the Pleistocene aeolianites showed fine to very fine mean grain size and very poor sorting. Studied dunes showed the dominance of grain shapes varying from sub-rounded to fresh angular. Regarding mineralogy, calcite bioclasts are prevalent in sands of the right bank of the river, while quartz is more abundant in dunes located at the left bank. In the active dunes of the left bank, other carbonates were also detected in bioclasts such as aragonite, dolomite, and magnesian calcite, suggesting a marine provenance. The siliciclastic grains of the studied generations of aeolian dunes are likely originating from Triassic, Jurassic, and Quaternary units crossed by the Ksob River. In fact, the results revealed the presence of minerals such as albite, plagioclase, microcline, and orthoclase which could have been sourced from Triassic basalts and gypsum which is often associated to Jurassic evaporitic rocks. This study allowed to suggest the probable origin of the sands that form these dunes based on the detailed study of their grains, which has not been studied on previous research works of the area. In addition, this research is of particular relevance as it fits into the current research trend related to understanding the evolution of Plio-Quaternary coastal dune systems in the world and could be applicable to other dune systems of the Atlantic coast of Morocco in the future.

中文翻译：

---

索维拉沿海沙丘系统的沉积学，矿物学和地球化学研究：潜在成因和来源

第四纪沿海沙丘经常发生在摩洛哥的大西洋沿岸，是河水排放，沿海漂流，风，植被和其他气象条件共同作用的结果。在本文中，我们调查了科索夫河沿岸的索维拉沿海沙丘沙的质地和组成参数，以及它们的来源。从形态上讲，它们以现今的活跃沙丘，全新世化石沙丘和更新世风成岩沉积物的形式出现。为了调查晶粒的出处，我们选择了实验室分析，包括晶粒大小，矿物学，微观纹理和石英晶粒的微观形态。全新世化石和活性沙丘的沙粒显示出非常细至中等的平均粒度，且分类适中，而更新世的风成岩则显示出细到极细的平均晶粒度，并且分类很差。研究过的沙丘显示出谷物形状的优势，从亚圆角到新鲜角都有变化。关于矿物学，方解石生物碎屑普遍存在于河的右岸，而石英在左岸的沙丘中含量更高。在左岸的活跃沙丘中，在生物碎屑中还检测到其他碳酸盐，如文石，白云石和镁方解石，表明有海洋起源。被研究的风沙丘世代的硅质碎屑颗粒可能起源于科索布河穿越的三叠纪，侏罗纪和第四纪单元。实际上，结果表明存在诸如钠长石，斜长石，微碱，正长石可能来自三叠纪玄武岩和石膏，通常与侏罗纪蒸发岩有关。这项研究可以根据对沙丘的颗粒的详细研究来提出形成这些沙丘的砂的可能来源，而该地区以前的研究工作尚未对此进行研究。此外，这项研究具有特殊意义，因为它适合当前与理解世界上的Plio-第四纪沿海沙丘系统的演变有关的研究趋势，并且将来可能会应用于摩洛哥大西洋海岸的其他沙丘系统。尚未对该地区以前的研究工作进行过研究。此外，这项研究具有特殊意义，因为它适合当前与理解世界上的Plio-第四纪沿海沙丘系统的演变有关的研究趋势，并且将来可能会应用于摩洛哥大西洋海岸的其他沙丘系统。尚未对该地区以前的研究工作进行过研究。此外，这项研究具有特殊意义，因为它适合当前与理解世界上的Plio-第四纪沿海沙丘系统的演变有关的研究趋势，并且将来可能会应用于摩洛哥大西洋海岸的其他沙丘系统。