Mineralogy of Saudi Arabian Soils: Southwestern Region

Abstract

Abstract Mineralogical properties of soils along a 500‐km north‐south transect in the mountainous Asir region were investigated. The transect represented areas of wide variations in climate, parent material, and topography. Soils developed on stable landscapes at higher elevation (> 2,000 m) have well‐developed profiles and near neutral soil pH's. Soils developed on alluvial terraces near wadi banks at lower elevations (> 1,500 m) have deep but less developed profiles, and slightly greater than neutral pH's with carbonates present. Quartz, feldspars, and micaceous minerals are the major components of the silt and sand fractions of the soils. Clay fractions of the soils are composed mainly of kaolinite, smectite, vermiculite, mica and chlorite minerals. Kaolinite is the most abundant clay mineral of the soils developed on well‐drained highland areas. Smectite is the most abundant clay mineral in the alluvial soils developed on lower terrace areas.