Magnetofossil Contribution to Sedimentary Magnetic Records and Sediment Provenance Reconstruction: A Case From the Bengal Fan

Environmental magnetism is widely employed for sediment provenance study, particularly in detrital‐dominated marine and lake systems. However, magnetofossils can complicate magnetic signals for accurate reconstructions of source‐to‐sink processes, yet their impact remains underexplored. The Bengal Fan, the largest submarine fan in the world, provides an ideal setting for studying sediment transport for its diverse sediment sources and transport pathways. Here, we combine magnetic and electron microscope analyses on a large set of surface sediments from the central and lower Bengal Fan to characterize magnetofossil contributions to magnetic properties. Results demonstrate widespread magnetofossil occurrence. Quantitative unmixing of isothermal remanent acquisition curves and first‐order reversal curve‐principal component analysis, assisted with direct transmission electron microscopic imaging of magnetofossils reveal that the southernmost region contains the highest magnetofossil contribution. Total organic carbon influences the magnetofossil abundance, while the magnetofossil morphology compositions are likely modulated by redox conditions impacting the diversity of magnetotactic bacteria species. Fuzzy c‐means clustering analysis identifies four sediment clusters. Cluster 1 derives from Indian Peninsula. Cluster 2 represents Himalayan–Burma–Indian mixtures, transported by the active channel with fining downstream. Cluster 4 and the southern part of cluster 3 show anomalous magnetic grain size trends linked to high magnetofossil contributions. The magnetofossil presence alters detrital magnetic records, showing high correlation between magnetofossil magnetization and bulk magnetic grain size parameter, thus complicates provenance interpretations. We demonstrate the combined use of rock magnetism and electron microscopy to quantify magnetofossil contributions for robust magnetic interpretation, especially in high detrital input regions where magnetofossils are often overlooked.