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Geological Environments of the Late Cenozoic Lakes and Salt-Forming and Oil-Gas Pool-Forming Actions in the Tibetan Plateau
详细信息   
摘要
The evolution of the lakes in the Tibetan plateau is dominated by the change of both the geological structure and the climate. Thus the lacustrine sediments can serve as a good recorder for both the past geological events and the climate change. Besides, the lacustrine sediments are strategic resources for salts, oils and gas. However, there had been no high resolution successive drilling core from the lacustrine sediments in the QT plateau that could reach a length of 1～2 km before this work. Since the beginning of this century, the authors have systematically collected 5 drilling cores with lengths of 1～2 km from the east and west Qaidam basin, and have obtained unprecedented rich information concerning the geological and climatic history of the Tibetan Plateau from these sedimentary cores. Through comparing the chronologic results with the latest international standard, a more precise model of magnetostratigraphy was established. Based on studying the cold, warm and eurythermal saline minerals in Qaidam basin, the authors found 31 series of cold events since 2 Ma BP. From that time Qaidambasin began to intermittently appear cold events. The time of cold events is close to the chronologic data of Cenozic Global Glaciation. The uplift of the Tibetan Plateau was tentatively divided into several stages according to the study of the deposition rate and the particle size. At the first time, the authors found that there was a demarcation line in the middle of Qaidam basin, which was not only the boundary of paleo-atmospheric circulations but also the boundary of salt formation. The westerly wind inclined area located to the north of the investigated line reflects salt deposits in the cold-wet climate period. To the west of the study area, the cold saline sediments occurred after 2 Ma, whereas they gradually crystallized into cold saline deposits at 0.72 Ma; in contrast, the saline sedimentary period started at 0.048 Ma in the south part of the boundary. The point of view is put forward in this paper that potassium was concentrated by the transportation of the multi-stage salt basin lying in the high mountain-deep basin environment, and this viewpoint can further improve the theory of potassium formation in continental facies. A new potash-rich brine horizon was found by the authors in the western Qaidam basin.

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