Chlorine isotopes in sediments of the Qarhan Playa of China and their paleoclimatic significance

This study presents chlorine isotopic composition of salt deposits recovered in a core from the Qarhan Saline Lake in the Qinghai Province of China. The δ37Cl trend has three stages, and they correspond to the upper, middle, and lower salt-bearing groups of the entire evaporite system. The δ37Cl values are between −0.22‰ and 0.13‰ with an average value of −0.02‰ in the lower salt-bearing group. It ranges between 0.14‰ and 0.76‰ (x¯ = 0.36‰) in the middle salt-bearing group, and varies between −0.35‰ to 0.35‰ (x¯ = −0.04‰) in the upper salt-bearing group. This work indicates that stratification of δ37Cl values is accompanied by stratigraphic variations in Mg/Cl and K/Cl in halite. We suggest a “evaporation cycles model” and it indicates the potential of Cl isotope as a geochemical tracer in order to understand paleoclimatic conditions during different stages of evaporite deposition.