<p>The Brahmaputra-Jamuna River system represents a potential source of valuable heavy minerals (VHMs) within the Bengal Delta. Previous studies focused on major and trace element geochemistry and whereas this study adopts a combined approach by integrating subsurface standard penetration test (SPT) boreholes data with detailed sedimentological, geochemical, and mineralogical analyses. The samples are dominated by fine to medium-grained sands with moderately well sorting, comprising ~ 98% of the total sediment, while the remaining ~ 2 wt% consists fine silt and minor clay. X-ray fluorescence (XRF) analysis shows that the samples are mainly composed of SiO₂ (69.06 wt%), Al₂O₃ (12.70 wt%), and Fe₂O₃ (4.47 wt%), and LOI averaging 2.70 wt%. X-ray diffraction (XRD) analyses reveal that the sediments are dominated by quartz, feldspar, and mica, while semiquantitative analysis shows that magnetite (6.41 wt%) and ilmenite (3.83 wt%), with total heavy mineral (THM) averaging 11.8 wt% and VHMs varying from 6.1 to 38.1 wt% across boreholes. Photomicrographs show magnetite as subhedral-euhedral, ilmenite with fractured surfaces, rutile prismatic, zircon angular-subrounded, monazite rounded and fractured, and garnet subhedral with surface irregularities. Spatial distribution patterns indicate enrichment of magnetite and garnet from proximal Himalayan sources, while the concentration of zircon, sillimanite, monazite, and rutile is controlled by hydraulic sorting and sediment recycling. Provenance-sensitive indices (ZRi 18.71–91.71%, RZi 8.29–81.29%, GZi 31.39–94.62%, MZi 10.31–84.7%) indicate that sediments were derived from mixed felsic-mafic sources. These results provide new insights into subsurface heavy mineral distribution and establish a scientific basis for future economic evaluation and sustainable utilization of fluvial heavy mineral resources in Bangladesh.</p>