MINERALOGICAL RECORDS OF HOLE 1F IN LAKE QINGHAI AND THEIR PALEOCLIMATIC IMPLICATIONS

We applied X-Ray Diffraction Analysis to the mineralogy of the cores of Hole 1F, which was drilled in the center of northwest Qinghai Lake, and determined the content of quartz, aragonite, dolomite and calcite. Based on the characteristics of mineral assemblages, together with sedimentary facies, we divided the 18.5m long core into three distinctive segments at the depth of 11.65m and 4.8m indicating three climate stages. The results indicate that:(1) the mineralogy of the core is a record of paleoclimatic events in the Qinghai Lake. From the 18.5m long core, there were three paleoclimatic stages:Cold-dry period (18.5~11.65 m), tempered cold-dry period (11.65~4.8 m), and warm-humid period (4.7~0 m), and the third period can be further divided into three periods:climatic oscillation period, the Holocene climatic optimum and cool-dry period. (2) the quartz content correlates well with the dry climate, high quartz content reflects a dry climate, while the low content represents a humid climate. (3) During the Last Glacial Period, there deposited little aragonite in the lake, but during the stage of Deglaciation, aragonite deposited steadily and reach the top value during Holocene. High aragonite content reflects a warm-humid climate, while low aragonite content represents a cold-dry climate, and can be reasonably correlated with δ¹⁸O record of stalagmite in Dongge cave. Quartz and aragonite assemblages may well represent Qinghai Lake's paleoclimatic variation.