Mineral magnetic characterization of the Godavari river sediments: Implications to Deccan basalt weathering

Abstract

Mineral magnetic analysis including thermo-magnetic studies and clay mineralogy on bed load and floodplain sediments from the Godavari river indicate distinct mineral assemblages. The floodplain sediments up to the delta region are characterised by unimodal ferrimagnetic mineralogy marked by the presence of maghemite and single domain magnetites derived from Deccan basalts. On the other hand the bed loads show varied magnetic mineral assemblages depicting greater local mixing from the non-basaltic bedrock province. The temperature dependent magnetic susceptibility and clay mineralogy of the floodplain samples show titanomagnetites (Fe3O4-Fe2TiO4), maghemite (χ LF-Fe2O3) and smectite that are characteristic of the Deccan Volcanic Province (DVP). Presence of this ferrimagnetically dominant unimodal assemblage up to the delta region and probably into the Bay of Bengal off the Godavari river is attributed to extensive chemical weathering of the basalt. The quantitative approach of mineral magnetism, therefore, can be used to study the paleomonsoon variability and its relation to Deccan basalt weathering from the Godavari-Bengal fan system.