ORIGIN OF THE HAJIANG SALINE POOL IN THE SOURCE AREA OF THE YELLOW RIVER AND ITS SIGNIFICANCE
黄河源区哈江盐池的成因与意义*

The Hajiang saline pool in the source area of the Yellow River is located in Madoi County, Qinghai Province, at 36.42°N, 99.06°E. It was considered as the starting place of the ancient Qiang people who migrated from grasslands in the northeastern Qinghai-Tibet Plateau to the Chengdu Plain in the Upper Ancient Age. Then, the ancient Qiang people created the San Xing Dui and Jin Sha cultures in Chengdu and the adjacent area. According to the analyses of geomorphological evolution and related climatic variation, it is suggested that the developmental process of the Hajiang saline pool may be divided into two stages: the paleo-lake stage and the saline lake stage. In the first stage, the Yellow River incised into the Duoshixia Gorge from the east to the west and stretched up to the Source Area, as the results of headward erosion and river capture since ca.7000aB.P. The Hajiang paleo-lake lost its major water supply from mountains of the north side. Although late development of this stage made the Hajiang paleo-lake into a half-closed lake, it is suggested that the lake was not a saline lake under warm-humid climate during that age(equal to the "Atlantic Period" or the "Altithermal Period"). The Hajiang paleo-lake later became a half-dry saline lake because of the Middle Holocene climatic change("Mid-Holocene transition")from warm-humid to cold-dry and a series of climatic events since 5500aB.P. , especially the great cold-dry event (equal to "IRD(ice-rafted debris) event 3",or "Holocene event 3")at ca.4500aB.P.The geomorphological evolution and climatic variation not only resulted in the formation of the saline pool, but also compelled the ancient Qiang people to migrate to lower and warmer places, among which the valleys in the eastern margin of the Plateau and the Chengdu Plain were the best choices. The formation of the Hajiang saline pool made it possible for local residents to develop an ancient salt industry to exchange salt with others from the adjacent area, which helps their migration from the plateau to the plain.