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祁连山各个山前盆地内发育了大量断裂和褶皱,是青藏高原向北扩展的重要表现形式。对这些断层和褶皱的研究有助于探讨青藏高原向北扩展和隆升的机制问题。酒西盆地是位于祁连山最西端的山前坳陷盆地,其内部正在发育最新生的白杨河逆断裂-褶皱带。本文通过对白南断裂-白杨河背斜的地质调查、阶地测量以及探槽开挖工作,对酒西盆地内部最新生的白杨河逆断裂-褶皱得到了几点认识:①白杨河逆断裂-褶皱是酒西盆地内新生的逆断裂-褶皱,是酒西盆地边界断层无法完全吸收青藏高原向北扩展的变形量所产生的次级构造。②白南断裂-白杨河背斜符合断层相关褶皱中的断弯褶皱模型,并存在膝折带迁移的现象。③白杨河背斜的起始隆升时间在中更新世后期,即距今300ka左右,平均隆升速率约0.21mm/a;构造强度有逐渐增大的趋势,全新世以来隆升速率约0.36~0.5mm/a。④白南断裂是全新世活动断裂,全新世以来发生过至少2次古地震。在近1ka以来至少存在一次最新的古地震事件。
A large number of faults and folds are developed in all foreland basins in Qilian Mountains, which is an important manifestation of the northward expansion of the Qinghai-Tibet Plateau. The study of these faults and folds will help to explore the mechanism of the northward expansion and uplift of the Tibetan Plateau. Jiuxi basin is located in the Piedmont basin at the westernmost tip of the Qilian Mountains, and the interior of the newly developed Baiyanghe thrust fault-fold belt is under development. In this paper, by means of the geological investigation, terrace measurement and trench excavation work of the Bai’nan fault and the Baiyanghe anticline, some understandings have been given to the newly born Baiyanghe thrust fault-fold within the Liuxihe basin: ① the Baiyanghe thrust fault-fold It is the reverse fault-fold of the new born in the Jiuxi basin. It is a secondary structure caused by the inability of the boundary fault in the western Sichuan basin to completely absorb the northward expansion of the Qinghai-Tibet Plateau. ② The Bai-Nan fault-Baiyanghe anticline is consistent with the fault-bend fold model in fault-related fold, and there is the phenomenon that the knee flexure zone migrates. ③ The initial uplift time of the Baiyanghe anticline was in the late Middle Miocene, about 300 ka away from the present, and the average uplift rate was about 0.21 mm / a. The tectonic intensity tended to increase gradually. The uplift rate was about 0.36 ~ 0.5mm / a. ④ The Bai Nan fault is the active fault of the Holocene. At least 2 paleoseismic events have occurred since the Holocene. There has been at least one latest paleo-earthquake event since at least 1ka.