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鄂尔多斯盆地南缘上、下古生界呈现明显的角度不整合,标志着该区卷入了加里东造山带变形。本文以盆地内奥陶纪沉积充填记录为线索,利用地层序列中沉积凝灰岩的锫石U-Pb同位素测年,结合秦岭造山带岩体年代学研究成果,探讨了秦岭加里东期构造事件的发生与发展过程。研究表明:1)奥陶系沉积时期,沉积序列经历了海侵至海退的完整旋回,中奥陶世马五期海退序列开始,晚奥陶世背锅山期海水自鄂尔多斯盆地西南缘完全退出;2)晚奥陶世平凉期至背锅山期,地层序列中凝灰岩、滑塌构造、滑塌角砾岩普遍发育,滑塌构造和滑塌角砾岩的直接触发因素是构造活动引发的地震,构造活动性明显加强;3)中奥陶世马五期海退序列的开始,孕育着秦岭洋壳板块开始向北俯冲,时限大约为475~463 Ma;4)晚奥陶世平凉期,沉积序列中重力流、滑塌构造和凝灰岩普遍发育,孕育着秦岭洋向北的俯冲碰撞进入了高峰阶段,其时限大约为454~450 Ma。
The upper and lower Paleozoic in the southern margin of Ordos Basin show obvious angle unconformity, which indicates that this area is involved in the deformation of the Caledonian orogenic belt. Based on the records of Ordovician sedimentary filling in the basin and U-Pb isotopic dating of tuff from sedimentary tuffs in the sequence, combined with the geochronology of Qinling orogen, the occurrence of Caledonian tectonic events in Qinling And development process. The results show that: 1) During the Ordovician depositional period, the sedimentary sequence underwent a complete cycle from transgression to regression. The middle Ordovician M-5 regression sequence began. The late Ordovician back-pots from the western margin of the Ordos Basin Completely withdraw from the basin; 2) tuff, slip structure and slip breccia in the stratigraphic sequence are generally developed during the Pingliang Period to the Repo Period in the late Ordovician period. The direct triggers of the slip structure and slip breccia are tectonic activities The earthquakes triggered and the tectonic activities obviously strengthened; 3) The beginning of the Middle Ordovician M-5 regression sequence began with the northward subduction of the oceanic crust in the Qinling Mountains with a time limit of 475- 463 Ma; 4) Late Ordovician During the Pingliang Period, the gravity flow, slump structure and tuff generally developed in the sedimentary sequence, and the subduction collision of the Qinling ocean northward entered the peak phase with a period of about 454-450 Ma.