Late Pleistocene-Holocene clay mineral record from the Great Rann of Kachchh basin, Western India: Implications for palaeoenvironments and sediment sources

The present study uses clay mineralogy to delineate a ∼17 ka record of palaeoenvironmental/palaeoclimatic changes in the recently uplifted palaeogulf of Arabian Sea i.e. Great Rann of Kachchh (GRK). Situated on continental margin of Indian subcontinent and flanked by Indus delta, the GRK basin has preserved continuous record of post glacial sedimentation. Clay mineral studies on two long cores (∼60 m and 50 m long) show more abundance of physical weathering products (illite and chlorite) over the chemical weathering products (smectite and kaolinite). We show that the GRK sediments depict multiple sources of sediment input. Dominance of illite-chlorite suggests GRK received sediments dominantly from the Himalayan terrain with minor contribution from adjacent regions. We present the oldest clay mineralogical signature of an interval of intensified monsoon conditions during the late Pleistocene (∼17.7-16.3 cal ka B.P.). Monsoon became stronger before ∼8.4 cal ka B.P., and whereas the mid Holocene weakening of monsoon occurred after ∼7 cal ka B.P. Despite the differences in source region and composition of clay mineral records from the GRK with northeastern and southeastern Arabian Sea, the sedimentation responded to major climatic shifts that have occurred since the LGM.