Mineralogy and provenance of red clay soils in Barind and Madhupur clay formations, Bangladesh: Implications for tectonic setting and chemical weathering

This study investigates the geochemical and mineralogical properties of the Barind and Madhupur clay formations in the Bengal Basin, focusing on their provenance, tectonic setting and weathering processes in relation to regional geological evolution. Several techniques such as particle size distribution, X-ray diffraction (XRD), X-ray fluorescence (XRF), atomic absorption spectrometry (AAS) and geochemical weathering indices were applied to analyze the mineralogical, chemical and heavy metal characteristics of red clay soils. The particle size distribution reveals that the soil consists predominantly of fine-grained silt (∼80 %), with minor amounts of clay and sand, influenced by pedogenesis and weathering processes. Mineralogical analysis reveals dominance of quartz, kaolinite, illite, chlorite and iron oxides, suggesting a mix of weathered metamorphic and sedimentary rocks and intense weathering in a humid, cold Pleistocene climate. Geochemical data show high concentrations of SiO₂, indicating a quartz-rich source with a mature mineralogical composition. Principal component analysis (PCA) points to extensive weathering, particularly of mafic rocks. Chemical index of alteration (CIA) values ranges from 70.93 % to 90.80 %, indicating moderate to intense weathering. Trace metal concentrations are lower than the average Upper Continental Crust, suggesting long-term weathering. These findings underscore the role of humid, cold climates and tectonic setting in shaping the Bengal Basin’s Pleistocene landscapes. The study advances regional paleoclimatic reconstructions and highlights the interplay of Himalayan erosion, fluvial transport and chemical weathering in producing the distinctive red clay soils. Future work should integrate isotopic tracing to refine sediment source apportionment and climatic models.