SOLUBLE SALT IN THE SEDIEMNTS AT THE MADIGOU SITE, NIHEWAN BASIN AND ITS ENVIRONMENTAL IMPLICATIONS

The Madigou site lies on the northeast margin of the Nihewan Basin, North China. It is one of the newly discovered Early Pleistocene archaeological site in the Basin. The Madigou site is dominated by lake deposits located at the lower part of the Madigou section. Based on a well constructed soluble salts sequence of the section, the processes of hydrochemical and environmental evolution as well as human activities are studied by the authors. Results show that the Nihewan lake near the Madigou site was characterized by SO₄^2-, Na⁺, HCO₃^- and Cl^- ions,and the average content of the total soluble salts reaches 11.41‰, suggesting that the paleo-lake belonged to the kind of brackish water lake between the sulphate and the chloride lake in terms of lake evolution phase in a semi-arid area. The variation in K⁺、Na⁺、Ca²⁺、Mg²⁺、SO₄^2-, and Cl^- and the total content of soluble salts are well correlated. Upon the basis, five paleoclimatical stages were recognized according to the changes in mean grain size, susceptibility content, total soluble salt and soluble salt indicators in the profiles, which indicate the corresponding changes of lake environment. The middle stages of 2, 3 and 4, which were relatively warm and wet, are the periods dominated by active paleoanthropological activities. There were rich animal and plant resources in these periods and the salinity of the lake was relatively low. The results bear great significances in the research of the adaptive environment and behaviors of the early humans at the Madigou site.