The geochemical and pedogenic signatures of Shantisagara lake sediments, southern India: Implications for weathering, terrigenous influx, and provenance during the Holocene

Abstract

This study aims to determine variations in the terrigenous influx, the intensity of chemical weathering, pedogenic activity, and provenance of Shantisagara lake sediments in southern India for the past 11,000 years reconstructed using geochemical and magnetic susceptibility data. The results showed that K/Al, Fe/Al, Ti/Al, and Zn/Al ratios exhibited significant down‐core variations, whereas P/Al, Pb/Al, Na/Al, Cu/Al, and Ba/Al display steady values. The sediments have resulted from moderate to intense degree of chemical weathering and show high compositional maturity. The discrimination function diagrams, Al2O3/TiO2 and K2O/Na2O values, point towards a change from an intermediate source during the Early‐ and Mid‐Holocene to a felsic one during the Late Holocene. The similar LREE‐enriched chondrite‐normalized REE patterns indicate no significant change. The Early Holocene phase was characterized by a moderate influx of fine detrital fraction with a peak around 10,500 cal. Years B.P. The pedogenesis was strong in the catchment area during this period, with oxic conditions prevailing in the lake. The catchment area experienced moderate to high rainfall during this period. A fluctuating trend of terrigenous influx and chemical weathering is documented during ~8,000–4,000 cal. Years B.P. period in response to variable rainfall. Decreasing rainfall trends are observed during 4,000–2,000 cal. Years B.P., with a slight increase from 2,000 cal. Years B.P. to the Present. Anoxic conditions were present in the lake during the Middle‐ and Late Holocene with low pedogenic activity in the catchment.