Rock magnetic investigations of surface and sub-surface soil samples from five lake catchments in tropical southern India

Iron oxide minerals in soils provide valuable insights into pedogenic processes. A wealth of such information has been obtained by rock magnetic investigations on temperate soils but similar studies on tropical soils are rare. Here, we report rock magnetic data on pristine soil profiles and surficial soils from five catchments in the tropical southern India and throw light on the pedogenic processes. We ruled out contributions from greigite, bacterial magnetite and anthropogenic sources; hence, the magnetic signal is mainly from the catchment, principally pedogenic and, thus, has a climatic signature embedded in it. The Pookot profile from a high rainfall (~4000 mm/year) region does not exhibit any magnetic enhancement at the surface. In fact, there is hardly any difference between surface and sub-surface samples, which reflects on its deeply weathered nature as a result of the high rainfall. The Shantisagara profile exhibits lessivage of magnetic minerals, resulting in a thick magnetically enhanced zone. It shows the highest χ _lf values among the five profiles studied. The Thimmannanayakanakere (TK) and Ayyanakere (AK) soil profiles do not exhibit any magnetic enhancement of top-soil. In fact, χ _lf values increase towards the profile-bottom, suggesting top-soil erosion, besides contribution of magnetic minerals from parent rocks. In the TK profile, there is a clear distinction between surface and sub-surface samples, the former being magnetically coarser grained. The Kurburukere profile exhibits moderate to strong χ _lf values and a mild magnetic enhancement at the surface.The data would be useful for establishing soil-sediment linkages for paleoclimatic studies of lake sediments.