宁夏中卫盆地的沉积特征及其所反映的新构造运动

Depositional Features of the Zhongwei Basin, Ningxia, and Its Implications for Neotectonic Movements

地表及钻孔资料分析表明 :约在上新世 ,香山山地沿香山—天景山断裂带向东北强烈逆冲上升 ,山前挤压下陷形成南深北浅、剖面上呈楔形的中卫盆地。伴随挤压作用的进行 ,盆地南缘部分早期沉积沿一系列南倾叠瓦式断层从南向北逆冲抬升 ,后期沉积则伴随其南部逆冲而不断北迁 ,穿越盆地的古黄河也不断北移 ,使盆地沉积具穿时性。约在中更新世末期 ,中卫盆地因其北东侧烟筒山断裂强烈活动而抬升 ,黄河下切 ,盆地消亡。上述过程可能反映青藏高原东北缘强烈挤压变形的北进。

The Zhongwei Basin is the largest compressional basin situated between the arc-form mountains along the northeast margin of Tibetan Plateau. Based upon our investigation in the field and in borehole data, depositional features and their variations in space and time are analyzed in this paper. In the Pliocene, the Xiangshan Mountain began to thrust northeast strongly along the Xiangshan-Tianjingshan fault zone, resulting in the depression in foreland and formation of the Zhongwei Basin. The strong compression also made some earlier sediments in the southern part of the basin thrust and uplift northward along some south-dip imbricate faults, producing wedge-like basin in the north-south profile with deep southward and shallow northward. Combing the thrusting, later sedimentation, including the one of the Yellow River, which flew through the basin from the west to east, had continuously moved northwards, occurring in diachronism of the sediments. Approximately in the end of the middle Pleistocene, the Zhongwei Basin was elevated responsible for strong activities of Yantongshan fault zone situated in the northeast of the basin, resulting in the down-cutting of the Yellow River, which ended the depositional process of the Zhongwei Basin. The end of depositional process of the Zhongwei Basin possibly means the starting of the strong activities of the Yantonshan fault zone rather than the end of the activities of the Xiangshan Tianjingshan fault zone. The process above probably implies the shifting processes of the strong compressional deformation from southwest to northeast along the northeast margin of Tibetan Plateau.