Yerdi sand dunes (Erfoud area, southeastern of Morocco): color, composition, sand’s provenance, and transport pathways

Abstract

This study aims to prove sand dunes’ color difference across Ziz riversides at Yerdi and then to investigate sand’s origin and transport pathways. We have opted for remote sensing and Geographic Information System tools as a methodology, in addition to laboratory analyses, that included mineralogy, grain size, and shape investigation of samples collected from studied dunes. The results reveal the following: (i) variation in grain size and shape of the studied sand. A high concentration of quartz and a low amount of carbonates and iron oxide were recorded in the studied dunes. Heavy mineral analyses have shown a similar mineralogical concentration in both samples, yet sand in the left side appears to be richer in hematite and goethite than the right one. (ii) Band ratios 6:4 and 5:7 of Landsat TM allowed the mineralogical distinction of mafic minerals, carbonates, and quartz, while Landsat 3:1 band ratio and Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) 2:1 band ratio were the most suitable for iron oxide distinction. The results confirm the dominance of quartz in both sides. However, iron oxide III (Fe3+) concentration is much important in the left side, which explains the difference in sand color. (iii) The studied dunes are potentially supplied from Quaternary, Cretaceous, and Paleozoic formations. The abundance of ferruginous conglomerate among potential formations supplying dunes and the abundance of hematite and goethite in sand from the left bank more than the right explain the red color marking these dunes. While, dunes’ morphodynamic explains the pal color observed in dunes located in the right bank.