Clay Mineralogy of Selected Soils in Southern Nigeria

Abstract

Abstract Clay minerals in eight soil profiles from southern Nigeria were investigated by means of X‐ray diffraction, infrared spectroscopy, differential thermal analysis, and electron microscopy. These soils are derived from basement complex rocks, arenaceous sedimentary rocks and basalts. Kaolinite is the most predominant clay mineral for all the soils studied. A pronounced variation in clay mineralogy was found in the soils derived from basement complex rocks sampled at various locations along a toposequence. Halloysite occurs in freshly weathered materials, while smectite is found in poorly drained, lower members of the toposequence. Gibbsite occurs in soil derived from cretaceous arenaceous rocks in the high rainfall area. Among all soils studied, the highest amounts of amorphous Al silicate and extractable Fe and Al oxides were found in those derived from basalts. In all cases, Fe oxides exist predominantly in crystalline forms.