Provenance-landscape-climatic constraints on the clay mineral record of the Great Rann of Kachchh Basin, Western India

The Great Rann of Kachchh (GRK) Basin accumulated a huge sediment pile during the Holocene under complex climate-tectonic influences. The clay mineralogical investigations on three sediment cores, namely DS (~32 m), VK (~42 m) and KC (~37 m) show predominant illite and chlorites over the smectite and kaolinites suggest largely Himalayan derived sediment input to the GRK Basin, majorly through fluvial transport. The early Holocene clay mineral record marks predominant Himalayan sources (illite-chlorites) with substantial mixing from NW alluvial plains (Rajasthan-Haryana), Thar Desert and Aravalli ranges (smectite and kaolinite). These sediments were mainly transported through large Himalayan river/s (currently buried under Thar Desert e.g. Ghaggar-Hakra-Nara?) under developing monsoon. Later, the arid landscape of western India during mid-Holocene potentially facilitated aeolian mixing of fine-grained sediments contaminating sediment influx with relatively higher “smectite” proportions in overall clay mineral compositions. During Late-Holocene, despite choking of river channels, increased aridity, the GRK Basin continued to receive Himalayan sediments, suggests uninterrupted fluvial past of the region. Higher kaolinites and smectite during this period denoteincreased proximal source mixing and/or reduced Himalayan input to the GRK basin. The results show that the clay mineral assemblage at millennial scales was controlled by complex interactions between provenance, landscape and climatic phases, rather than the palaeoclimate alone.