Magnetic mineral tracing of sediment provenance in the central Bengal Fan

We present a comprehensive magnetic mineral analysis of surface sediments from 110 sites in the central Bengal Fan to trace sediment provenance. Multiple magnetic parameters, including magnetic mineralogy, concentration, and grain size were generated. Rock magnetic measurements indicate that the dominant magnetic minerals within the studied sediments are detrital magnetite and titanomagnetite, which is further confirmed directly by scanning electron microscope (SEM) and transmission electron microscope (TEM) observations on magnetic extracts. Fuzzy c-means clustering analysis of magnetic parameters indicates that the study area can be divided into three clusters. Considering the position of ‘active valley’, we further divide cluster 1 into clusters 1A and 1B. Cluster 1A primarily covers the west side of the ‘active valley’ with relatively high magnetic concentrations and dominantly coarse-grained magnetic minerals, which likely correspond to basaltic materials derived from the Deccan Plateau. From the Godavari river mouth to the inner Bay of Bengal, magnetic concentration gradually decreases with a fining trend of magnetic grain size. Clusters 1B, 2, and 3 are on the east side of the ‘active valley’, where magnetic concentration and magnetic grain size decrease with increasing distance to the ‘active valley’. Combined with published data in the Indian region and the upper Bengal Fan, we suggest that the main provenances are the Himalayan and the Deccan Plateau, whose contributions to sediment distribution are quantitatively assessed. Our analysis suggests that the position of ‘active valley’ plays a key role in sediment distribution in the central Bengal Fan, while the effect of ocean currents is negligible.