PRELIMINARY STUDY ON SEDIMENTARY CHARACTERISTICS AND EVOLUTION OF PALAEOCLI MATE OF QARHAN SALT LAKE IN QAIDAM BASIN

Qarhan salt lake which covers an area of 5800 square kilometres is a large playa in Qaidam basin, Qinghai Province. The salt-bearing layers are usually 40 m thick, the maximum thickness being 73 m.The sedimentation of the lake has the following basle characteristics: (1) The salt-containing layers are principally composed of interbedded halite and clastic sediments, and they are either lacking in sulfate deposits or deficient in carbonate sediments. (ii) The sedimentary differentiation is not sufficient, and all of the halite layers almost contain mud, sand, carbonates and gypsum in varying degrees; there exist mixtures of gypsum and halite in the intercalations of clastic sediments. (iii) The salt-carrying beds are associated with aeolian deposits. The authors found for the first time that Malan loess exists in the salt-bearing layers of Qarhan salt lake.Features of evolution of palaeoclimate: A lot of evaporite deposits had appeared in Qarhan salt lake by the end of Late Pleistocene, 24,000—25,000 ye