Clay and Other Minerals in Soils and Sediments as Evidence of Climate Change

Abstract

Identification of paleoclimatic signatures in paleosols is a major challenge to soil scientists. It is realized that the clay minerals of the paleosols are potential promising materials for documenting and resolving a wide spectrum of different genetic environments and reactions. It is often difficult to determine which soil minerals are characteristic of different climatic zones as the environment itself changes over time with consequent further modification of mineral assemblage and this is particularly true for clay minerals. Clay minerals such as kaolinite often remain unaltered through subsequent changes in climate, and therefore, may preserve a paleoclimatic record. Other layered silicates at a less advanced stage of weathering may adjust to subsequent environmental changes and thus may lose their interpretative value for paleoclimatic signatures. However, Indian soil scientists, clay mineralogists and earth scientists indicate that minerals of intermediate weathering stage can act as potential indicators of paleoclimatic changes in parts of central India and Gangetic Plains. They have demonstrated how secondary minerals like di- and trioctahedral smectites (DSm and TSm), smectite-kaolinite interstratified minerals (Sm/K), hydroxy-interlayered smectite (HIS), hydroxy-interlayered vermiculite (HIV), pseudo-chlorite (PCh) of intermediate weathering stage, and CaCO₃ of pedogenic (PC) and non-pedogenic (NPC) origin can be regarded as potential indicators of paleoclimatic changes in major soil types of India and also in paleosols of the alluvial sediments of the Himalayan river systems and Cratonic source from Peninsular India.