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

Texturally, the samples are silty-clay to clayey-silt. The clay mineral ass emblage is predominated by chlorite, followed by montmorillonite, illite an d kaolinite. Non-clay minerals are quartz and calcite. Semi-quantitative cl ay species abundances on diffractograms and crystallinity indices (CI) of i llite and montmorillonite were also estimated. CI of montmorillonite reflec ts the poorly crystalline nature. It is inferred that the clays are of detr ital origin most likely from the soils of Himalayan region drained by river s Ganges and Brahamaputra and that a portion of montmorillonite could be po ssibly sourced in the soils derived from the weathering of flood basalts at the Deccan Plateaue of west central India and transported by the east flow ing rivers of the peninsula However, the clay sized quartz is of detrital o rigin, whereas calcite is mostly biogenic. Down core variation of clay mine ral assemblage at a depth of 40 cm indicates a shift of climate from cold/d ry to warm/humid condition during 12 x 10(3) y BP.