Genesis and mineralogy of some red and laterite soils of Orissa

Two red soil profiles and two of laterites in the state of Orissa were studied for their morphology, mineralogy and genesis. Both the red soils are developed on charnockite ard khondalite rocks of the Eastern Ghat region. Acidic reaction and high permeability have led to the dominance of kaolinite in the soil from Semiliguda while a higher proportion of potash feldspar and mica are responsible for dominance of illite in the Phulbani soils. Laterite soils are derived from Athgarh sandstones, an extension of lower Gondwana rock system, under hot and humid climate. Higher proportion of potash bearing minerals in the sand fraction reflects the prevalence of moderate weathering conditions which is conductive for illite in the laterite soils from Khurda. Parent rocks rich in quartz and orthoclase feldspar subjected to more leaching have resulted in kaolinitic and illitic type of clay in the Bhubaneswar soils.