Clay Minerals of Soils at Wadi Hanifa (Najd plateau, Saudi Arabia)

Abstract

Three soil profiles representing the main landforms (plain, fans, and wadi bottom) at wadi Hanifa which is located within the sedimentary Najd plateau are selected for clay mineral identification. The studied soils are classified as Typic Torriorthents, particle size classes are either loamy, loamy skeletal or sand skeletal. Soils are generally highly calcareous with few secondary lime segregation at subsurface horizons. Mineral assemblage of the clay fraction in all clay samples is dominated by attapulgite followed by kaolinite. Chlorite, smectite, interstratified minerals and accessory minerals are found in traceable amounts. Clay mineral assemblage of the studied landforms and throughout the respective horizons of soil profiles is nearly similar. The mineralogical composition of these soils is mostly relicts of the soil parent materials forming the successive horizons of soil profiles as soils are recent from the pedological point of view. Mineralogical composition of clay and calcium carbonate content throughout the depth representing the profile control section differentiates these soils to two mineralogical classes namely: carbonatic and mixed (calcareous).