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鄂尔多斯地区南部和东秦岭北部是华北稳定陆块与秦岭海槽之间的过渡带．早古生代可划分为５个中层序（ｍｅｓｏｓｅｑｕｅｎｃｅ）．ＭＳ－１．包括下寒武统及中寒武统徐庄组，为混水台地沉积体系，时间跨度在３５Ｍａ；ＭＳ－２．包括下寒武统张夏组、上寒武统和下奥陶统冶里—亮甲山组，为清水台地沉积体系，时间跨度近３７．９Ｍａ；ＭＳ－３．包括下奥陶统马家沟组和峰峰组，为蒸发型台地沉积体系，时间跨度近３１Ｍａ．三者组成显生宙第一大层序（ｍｅｇａｓｅｑｕｅｎｃｅ），形成一巨大沉积旋回，为地壳动力伸张所成；ＭＳ－４．包括赵老峪组，为弧后盆地形成的斜坡沉积体系和盆地沉积体系，时间跨度１７Ｍａ；ＭＳ－５．系上奥陶统，包括背锅山组、上店组、两岔口组等，为残留海台地型沉积体系．这两个中层序形成显生宙第二大层序的主体，形成一巨大沉积旋回，为地壳动力挤压所成．
The Erdos area and the northern part of the East Qinling Mountains are the transitional belt between the stable land mass in North China and the Qinling Trough. Early Paleozoic can be divided into five mesosequences. MS-1. Including the Lower Cambrian and Middle Cambrian Xuzhuang Formation, is a sedimentary system of mixed water platform with a time span of 35Ma; MS-2. Including the Lower Cambrian Zhangxia Formation, the Upper Cambrian and the Lower Ordovician Yeli-Liangjishan Formation, which is the Qingshuitai Depositional System with a time span of nearly 37.9Ma; MS-3. Including the Lower Ordovician Majiagou Formation and Fengfeng Formation, are evaporative platform depositional systems with a time span of nearly 31 Ma. The three constitute the largest sequence of the Pleistocene (megasequence), forming a huge sedimentary cycle, resulting from the crustal dynamic extension; MS-4. Including the Zhao Laoyu Formation, a slope sedimentary system and basin sedimentary system formed for the backarc basin with a time span of 17 Ma and MS-5. Department of Ordovician, including the back pot group, shop group, two fork group, as the residual sediment deposition system. These two middle-level sequences form the body of the second largest sequence of the Phanerozoic, forming a tremendous sedimentary cycle that is crushed by crustal motions.