Elemental Composition and Mineralogy of Silt and Clay Fractions of Cracking Clay Soils of Semi Arid and Arid Parts of Gujarat, India

Elemental composition and mineralogy of silt and clay fractions in two basaltic Vertisols viz Semla series: Aridic Haplusterts and Sokhda series: Calcic Haplusterts from semiarid and arid tracts respectively of Gujarat were studied to characterize the nature and composition of clay minerals in relation to elemental composition and to derive geochemical climofunctions. The most reactive fine clay had smectite with traces of quartz and mica whereas concentrations of CaO and Na₂O contents in silt fractions indicating intensive weathering of calcium and sodium minerals. The chemical data further supported the formation of montmorillonite-beidellite group(molar ratio of Al/Al+Fe >0.5 in fine clay fracion). The high degree of salinisation (CaO/K₂O) in Sokhda series indicated the prevalence of high evapotranspiration and prolonged dry seasons in the region. The CALMAG index supported the formation smecite under past humid climate but preserved even in existing alternate wet and dry seasons.