Down core variation of texture and clay mineralogy in a sediment core (SK-72/1) from Bengal Deep Sea Fan: Implication to climate and provenance

24-28Texturally, the samples are silty-clay to clayey-silt. The clay mineral assemblage is predominated by chlorite, followed by montmorillonite, illite and kaolinite. Non-clay minerals are quartz and calcite. Semi-quantitative clay species abundances on diffractograms and crystallinity indices (CI) of illite and montmorillonite were also estimated. CI of montmorillonite reflects the poorly crystalline nature. It is inferred that the clays are of detrital origin most likely from the soils of Himalayan region drained by rivers Ganges and Brahanlaputra and that a portion of montmorillonite could be possibly sourced in the soils derived from the weathering of flood basalts at the Deccan Plateaue of west central India and transported by the east flowing rivers of the peninsula. However, the clay sized quartz is of detrital origin, whereas calcite is mostly biogenic. Down core variation of clay mineral assemblage at a depth of 40 cm indicates a shift of climate from cold/dry to warm/humid condition during 12×103 y BP.