AEOLIAN SANDS IN NORTH AFRICA AND THE SOUTHWEST OF THE ARABIAN PENINSULA

Background. The majority of the world’s deserts were formed within the valleys and coasts of ancient alluvial rivers and lakes. The material carried across many hundreds and thousands of kilometres by the wind was mixing with sediments of various genetic types. In addition, due to the similar physical nature of the wind and water transport of sediments, the recognition of the aeolian environment can be problematic.

Aim. Using innovative research approaches, to provide a qualitative structural description of sands; to identify and characterize factors contributing to the formation and preservation of a ferruginous film on grains; to establish the genesis of the transferred sediments, as well as the relationship with the parent rocks.

Materials and methods. Samples for analysis were collected from aeolian deposits in three deserts: Rub al Khali (United Arab Emirates), Nubian desert (Egypt) and Grand Erg Oriental (Algeria). Particle size analysis was used to characterize samples in terms of three parameters (length, width, thickness). X-ray diffraction analysis was carried out using an ARL X’tra diffractometer (Switzerland). The collected samples were also studied using a binocular microscope in reflected light and a scanning electron microscope.

Results. The mineral composition of the sands under study was examined. The graphs (histograms) of the size distribution of quartz grains (being the most common sand mineral in terms of size and frequency of occurrence) were plotted. The shape and nature of the grain surface were analysed.

Conclusion. The frosting on aeolian sand grains can result not only from micro-cracking as the most common sign of wind transfer, but also from the presence of a calcite film on grains. Factors contributing to the formation and preservation of a ferruginous film (desert varnish) were identified. The conditions for the formation of aeolian sands, as well as the genesis of such sand sediments, were established.

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