关键词: 武威盆地, 青藏高原东北缘, 晚新生代, 砾石, 沉积过程, 高原隆升

Abstract: The Wuwei Basin is located in the eastern part of the Hexi Corridor basin group. It belongs to the frontier of uplift and expansion of the northeastern margin of the Qinghai-Tibet Plateau. The Quaternary sedimentary strata in the Wuwei Basin are hundreds of meters thick, which records the geological information of uplift and expansion of the northeastern margin of the Qinghai-Tibet Plateau during the Quaternary period. In order to study the sedimentary process of the Wuwei Basin since Quaternary and the characteristics of the uplift and extension of the northeastern margin of the Qinghai-Tibet Plateau, the sedimentary stratigraphy and stratigraphic chronology methods are applied to analyze the Quaternary sedimentary strata in the Wuwei Basin. Firstly, the Quaternary sedimentary sequence of the Wuwei Basin is established by studying the stratum characteristics and OSL ages of the Quaternary sedimentary strata. Secondly, through the analysis of the paleocurrent direction and zircon U-Pb isotopic age of the sedimentary gravel, the paleocurrent direction of different deposition periods and sediment source are restored. Finally, based on the above analysis, the sedimentary process of Quaternary strata in the Wuwei Basin and its response to the uplift and extension of the Qinghai-Tibet Plateau are discussed. The Quaternary sedimentary strata in the Wuwei Basin are the lower Pleistocene Yumen conglomerate bed, the middle Pleistocene Jiuquan gravel bed and the Upper Pleistocene-Holocene Gobi gravel bed from bottom to top. The Gobi gravel bed can be subdivided into the Upper Pleistocene gravel bed, the Upper Pleistocene -Holocene loess layer and the Holocene gravel bed. In the early Pleistocene, the Yumen conglomerate’s source material is mainly Mesozoic and Paleozoic rocks. The main provenance area of the Yumen conglomerate is located in the Qilian Mountains south to the Wuwei Basin. The main sedimentary area of the Yumen conglomerate is located in the Zoulang Nan Shan located in the southern part of the Wuwei Basin and the southern part of the northern fault basin. In the middle Pleistocene, the Jiuquan gravel bed’s source material is mainly Cenozoic and Mesozoic rocks. In the early sedimentary stage of the Jiuquan gravel bed, the main provenance area is located in the Zoulang Nan Shan and the main sedimentary area is located in northern part the Wuwei Basin. In the late sedimentary stage, the main provenance area of the Jiuquan gravel bed is located in the Zoulang Nan Shan and the Fenmen Mountain located in the northwestern margin of the Wuwei Basin, and the main sedimentary area is located in the most of the northern fault basin and the surrounding area of the Fenmen Mountain. Since late Pleistocene, the Gobi gravel bed’s source material is mainly early Paleozoic rocks. The main provenance area of the Gobi gravel bed is located in the Zoulang Nan Shan, the Fenmen Mountain and the Longshou Mountain, and the main sedimentary area is located around the source area. The uplift boundary of the northeastern margin of the Qinghai-Tibet Plateau continued to expand towards the northeast direction. The uplift boundary was located in the Qilian Mountains south to the Wuwei Basin in the early Pleistocene. It extended northward to the Zoulang Nan Shan and the Fenmen Mountain in the middle Pleistocene, and reached the southern margin of the Longshou Mountain north to the Wuwei basin in the late Pleistocene. The mainly provenance and sedimentary areas of the Quaternary sediments in the Wuwei Basin show the migration characteristics from south to north, which indicates the uplift and expansion of the northeastern margin of the Qinghai-Tibet Plateau. The uplift time was early in the south and late in the north, and the uplift intensity was strong in the south and west and weak in the north and east.

Key words: Wuwei basin, northeastern Qinghai-Tibet Plateau, late Cenozoic, gravel, sedimentary process, plateau growth