Geochemical Split Among the Suspended and Mud Sediments in the Nethravati River: Insights to Compositional Similarity of Peninsular Gneiss and the Deccan Basalt Derived Sediments, and Its Implications on Tracing the Provenance in the Indian Ocean.

Major, trace, and rare earth element (REE) geochemistry of sediments from a tropical mountain river is investigated to understand the behavior of chemical elements during weathering and transportation in a Peninsular Gneissic terrain. The results from this study are compared with the Deccan Basalt‐derived River sediments and the eastern Arabian Sea sediments with an intent to highlight the challenges associated with the provenance determination of sediments along the continental margin of India. The geochemistry of suspended particulate matter (SPM) and mud sediments (<63 μm) of the Nethravati River indicate that sediments are derived from a relatively homogenous lithology, characterized by intermediate rocks of tonalitic (low‐Al TTGs) composition. The tectonic origin of the source rocks discriminated using sediment geochemistry suggests an ocean island arc origin. The sediments experience intense chemical weathering in the source region. The elemental composition and their inter‐element relationships suggest differential chemical weathering of mineral phases fractionate mafic components and their secondary mineral products in SPM, and mixed sources dominated by felsic components and their secondary mineral products in mud sediments. Intense chemical weathering induces significant geochemical splits among the suspended and mud sediments. The transport of mafic‐biased sediments from Peninsular India to Oceans, and the geochemical similarity with Deccan Basalt‐derived sediments makes it challenging to track the Peninsular Gneiss‐derived sediment provenance along the continental margin of India using conventional elemental geochemistry. The inferences from this study have important implications for determining the sediment provenance along the continental margin of India. Plain Language Summary: The focus of this study is to characterize the impacts of chemical weathering and hydrodynamic sorting on the chemical composition of river sediment along a river in Peninsular India. The Arabian Sea dominantly receives sediment from the Himalaya and Deccan Traps and thus other sources, like rivers draining Peninsular India, are overlooked as important sediment sources. However, the processes that govern river sediment chemistry in Peninsular India are not well characterized, which may lead to incorrect interpretations of sedimentary records in the Arabian Sea. To address this knowledge gap, the major and rare earth element (REE) compositions of river‐suspended sediment and mud sediments have been analyzed and compared with the sediment compositions of Deccan Basalt draining rivers and the sediments from the Indian Ocean. The composition of river‐suspended sediment differs from mud due to hydrodynamic sorting, where suspended sediment has a more mafic affinity and mud has a more felsic affinity. Moreover, the study shows that REE patterns in rivers with substantially different exposed bedrock types can be similar because of intense weathering, which complicates the interpretation of incompatible element patterns in geologic records. Key Points: Geochemical split among the granulometric grades of sediments observed in the Peninsular RiverFelsic‐biased coarser sediments and mafic‐biased finer sediments in the Peninsular Gneissic cratonic RiverGeochemical similarity among the Peninsular Gneiss derived finer sediments and Deccan Basalt‐derived sediments is observed [ABSTRACT FROM AUTHOR]