Aeolian dynamics: mineralogical composition and source of Dakhla dune sands (Southern Morocco)

Abstract

As in many arid regions worldwide, wind-driven sand transport removes large quantities of sediment from multiple sources, thereby intensifying desertification processes in southern and southeastern Morocco. In this region, desertification is particularly evident through the active movement of dune sands.The study of wind dynamics in southern Morocco seeks to elucidate the environmental conditions and geomorphological processes that drive desertification, from bedrock erosion to the transport and deposition of diverse sand deposits. In this context, the present research provides a detailed petrographic and mineralogical characterization of the Dakhla sands, enabling the identification of their provenance and transport mechanisms

The Dakhla dune sands consist primarily of quartz grains and accessory minerals, including oxides, heavy minerals, and sandstone fragments, with smaller amounts of feldspars, micas, and calcite. This mineralogical composition reflects erosion, transport, and depositional processes associated with crystalline and sedimentary formations from the Anti-Atlas and Saharan domains, which supply the study area through both hydrological and aeolian pathways.

The quartz grains of the Dakhla dune sands, accumulated predominantly by wind action, are mainly rounded and dull grains of aeolian origin. However, a significant proportion comprises glossy, abraded grains of aquatic (mainly coastal or fluvial) origin, together with angular, locally derived grains. The mineralogical associations identified three main types of sand stocks:

1) Aeolian sands - dominated by rounded, dull quartz grains enriched in accessory minerals, primarily wind-transported and of likely crystalline origin.

2) Mixed alluvial–aeolian sands - characterized by glossy, abraded quartz grains enriched in accessory minerals, resulting from alluvial transport followed by aeolian reworking, with both crystalline and sedimentary sources.

3) Coastal sands - composed mainly of glossy, abraded quartz grains poor in accessory minerals, indicative of a highly quartzose composition of coastal origin.

Overall, the results clarify the complex interplay between aeolian, alluvial, and coastal processes in shaping the Dakhla dune sands, and underscores the importance of sediment provenance analysis for assessing the evolution of desert landscapes in southern Morocco.