In Shaanxi province there outcrops a complex rock series composed mainly of phyllite intercalated with lens -shaped dolomitite between Taowan Group and the Cambrian System. This rock series actually forms a shear-melange belt (SMB) the boundary between Qinling orogenic belt and North China Platform. The belt is not stratigraphic but tectonic unit. In Baiyushi area the belt can be divided into three tectonic slices separated by a series of thrusts. The tectogenetic dolomitite blocks occurring in the belt also can be regarded as secondary slices. According to analyses of microstructure, small -scale structure and lithologic comparison, the thrusts are believed to be moved southward and at least late Proterozoic Dazhuang Formation, Sinian Luoquan Formation and Middle - Lower Cambrian series and some of the Taowan Group were involved in the belt. Strong tectonic deformation resulted in fragmentation of the original strata and great changes in the sequence of strata. The shear-melange belt originated mainly in the Yanshanian Stage.