Palaeo-Lake Level Variations Of Jilantai Salt Lake And The Environmental Change Since Late Qatrenary

The Jilantai Salt Lake (39°46'59"N, 105°37'31"E) lies on the Alashan Plateau, Inner Mongolia, and is adjacent with the Ulanbuh Desert in the east, Tengger Desert in the southwest and Hetao Plain in the northeast. Bayinwula Mountain and Helan Mountain lie to the northwest and southeast of this lake respectively. Situated on the transition belt of arid and semi-arid region in northern China, Jilantai Lake is climatically influenced by Eastern Asia Moonsoon, and the lacustrine deposits are sensitive to environmental changes. Currently, Jilantai area are facing many environmental problems disturbing the living and production of residents dramatically, such as the expansion of desert and the drastic drop of groundwater level, which not only decrease the availability of natural resources in this area, but also increase the difficulty and cost of exploitation, In adjacent Hetao area, there are also some serious environmental problems such as salinization and desertification. Therefore, analysis on the formation, development and evolvement of lakes in the area of Jilantai not only provides the scientific clue to the evolutionary history of Hetao Palaeolake, but also helps to accumulate the referential data for environmental management as well as sustainable utilization of water resource. In this thesis, the spatial-temporal distribution pattern of the lake evolvement is reconstructed by accurately measuring the altitudes of each shoreline on the basis of differential GPS and analysis of remote sensing imagery, and determining the age of lake sediment by OSL dating method. In combination with the sedimentary proxies such as the granularity and magnetic susceptibility, the environmental change history is also reconstructed. The main conclusions of this dissertation are as follows:1. Large scale in-situ investigations indicate that there were five barrier-lagoon shorelines around the Jilantai Lake at elevations of 1080-1070 m, 1060 m, 1050 m, 1044 m and 1035 m respectively. ANW-SE barrier spit extends 4 km to the northwest of Jilantai Paleolake with elevations between 1048m and 1038m. Another NW-SE shoreline at 1080 m and a spit system at 1052-1035 m also existed in Herimuxini, central of the Ulanbuh desert. The partially extant paleo-beach erosion landforms, like high-level lacustrine stratum, and paleo-beach deposition landforms, like shoreline plate,...