Physicochemical weathering conditions of the characteristic white soil horizon at Al Firjah area and it’s vicinity in North Kordofan State, Central Sudan.

Mineral deposits and valuable materials are deposited, concentrated, and purified by natural processes during long or short time, chemical weathering reactions is a major one. Satelliteimages exhibit distinct white horizon of high reflectance. Investigation of this phenomenonreveals that these areas were associatedwith the distal reaches of the major part of the drainage system. Exposures of the basement rocks include metasediments marl, marble, and other silicate rocks(granite, granodiorite,meta andesite,….etc) at high land where the proximal reaches of the drainage system. These rock were subjected to chemical disintegration process of hydrolysis for silicateconstituent and dissolutionfor carbonate constituent and consequently these material were transportedby the drainage system as colloidal (kaolinite) and dissolved material(calcium cation and bicarbonate), eventually these material were deposited due to evaporation at flash delta to form the kaolinite carbonatesoil at Alfirjah area and it’s vicinity. Field observations in addition to rock and soil sample analysis forearm the above mentioned hypothesis.