Mineral Assemblages and Palaeoenvironmental Changes of Core DG03 of Gahai Lake in Delingha Basin

Key words: 
• Delingha Basin /
• Gahai Lake /
• mineral assemblages /
• palaeoenvironment /
• aragonite /
• gypsum

Abstract: Gahai Lake lies in the conjunction area of some largescale climatic systems such as East Asian monsoon area, southwest monsoon area and westerly wind and so on. Through studies on some palaeoenvironmental proxies such as minerals, grain size and carbonate content in Core DG03, we have analyzed and discussed the characteristics of palaeoenvironment changes in Gahai Lake, where is a sensitive area for climatic change. The research results show that the main minerals in core DG03 include quartz, plagioclase, microcline, chlorite, illite, calcite, aragonite, dolomite, gypsum and halite. The core records the palaeoenvironmental change information of Gahai Lake since about 11ka BP (AMS14C age). According to change characteristics of minerals and lithology, the core is divided into three parts: Ⅰabout 11 ka～10 ka BP, the last period of lateglacial (Younger Dryas event); Ⅱ 10 ka～4 ka BP, the early and middle Holocene; Ⅲ 4 ka ～0 BP, the late Holocene. The mineral assemblages in different period indicate that the water level of Gahai Lake experiences a process of lowhighlow and accordingly salinity highlowhigh. Gahai Lake orderly experiences the reverse and forward process of lake evolution. Combining the lithology and grain size, we speculate that Gahai Lake area orderly experienced the cold and dry climate of lateglacial, the warm and dry climate of early Holocene, the warm and wet climate of middle Holocene and the gradually cold and dry climate of late Holocene. The analysis of lithology also shows that there is a complex sedimentary environment and there are some different types of terrestrial deposits in Gahai Lake and the influence of alluvialproluvial deposition is through the whole Holocene. But we believe that the complex sedimentary environments can better reveal the change characteristics of regional environment. 