Salt-forming Ages of the Dabusun and Bieletan Regions in Qarhan Playa, Qinghai

Abstract: The¹⁴C and ²³⁰Th data of the sedimentS from the cores CK₈₂₆ of the Dabusun region and from the cores CK₂₀₂₂ of the Bieletan region have been accumulated in the study of chronology since 1976.From 1989, we made a systematic determination of¹⁴C and²³⁰Th on the samples of cores 88-01 and 89-04, and obtained more detailed data in the Study of evolution of Qarhan Playa.Cores 88-01 and 89-04 is located in the north shore of Dabusun Lake. The depths of both cores are 47m and 45m, respectively. The sediments are similiar not only in depositional characteristics,but also in salt-forming ages. A ages vs. depth chart is given in this paper, and a linear equation is obtained from the chart.It can be seen from the chart that there is a good correlation between the ages and the depths.From the linear equation, rough salt-forming ages of the four salt layers in the Dabusun region are obtained. The ages of the bottom layer S₁, S₂, S₃, S₄are 50000, 36000, 30000, 18000a. B. P.,respectively. In addition, the surface salt crust of Qarhan Playa was formed in about 8000- 9000a.B. P.. In order to make the explanation more clear, the core section chart and age data of cores 88-01 and 88-04 are made together with those of the four cores described in the reference (3). The result indicates that the salt-forming age in the Dabusun region is about 50000 a. B. P., which is largely different.from those of cores CK₂o₂₂,CK6and CK₁₃₀₈, and they reveal the salt-forming age of the Bieletan region. The salt-forming age of the Dabusun region is about 2000 years older than that of the Bieletan region.