干旱区生态环境知识资源中心

Few studies on the characteristics and mineralogical trends of the soils in the Sahara Desert have been reported in the literature. This work aims at studying the morphology, the classification, and the mineralogy of desert alluvial soils of the Mzab region in the Northern Sahara, Algeria. Morphological and analytical studies carried out on fourteen pedons of wadi Zegrir over a range of elevations (250-850 m) indicate that the soils are sandy to silty clay, nonsaline (electrical conductivity, EC < 0.53 dS/m), moderately to slightly alkaline (pH 7.46-8.52), and poor in organic matter content (0.02-2.38%) with good drainage conditions. In addition, the nature and composition of the soils show that they can be classified as aridisols (haplocambids and haplocalcids) and entisols (torriorthents, torrifluvents, and torripsamments). They have well-stratified layers, especially in the downstream part of the wadi, indicating interactions between alluvial and aeolian processes in which evaporite tertiary and secondary formations play an important role in the formation of contemporary minerals. Thin-section observations revealed that the occurrence of calcite in these soils is related to allochthonous mechanisms and in situ crystallization. X-ray diffraction analysis indicates that palygorskite and illite are present throughout the clay fraction of the soil samples in all studied profiles. Kaolinite and chlorite are less abundant, whereas smectite is present in minor amounts.