贺兰山西麓中生代构造反转及意义

通过对小松山断裂特征的再分析和对顺层断层特征的观察研究发现,发育于贺兰山北段西麓的小松山“推覆”构造实际上是一个滑覆构造。该区于晚侏罗世之后发生大规模构造反转,贺兰山沉积特征及玄武岩环境指示该区是一大陆裂谷斜坡,在中生代早中期并不存在大规模的东西向挤压应力环境。滑覆面之下的三叠系—中上侏罗统的褶皱变形及顺层剪切是这种滑覆引起的局部构造变形,与鄂尔多斯地块西部发育的典型的东西向逆冲形成明显对比,值得重视。 

TECTONIC REVERSE OF MESOZOIC AT THE WESTERN FOOT OF HELAN MOUNTAIN AND ITS MEANING

The comprehensive analysis of fractures and bedding structures in the Xiaosongshan fault indicates that,a huge tectonic reverse took place after the Late Jurassic and the Xiaosongshan 'nappe' structure developed at the western foot of the northern part Helan Mountain is actually a slipping structure.The sedimentary feature and the basaltic environment prove that,the region is a continental rift slope.Therefore,the(massive) compressive stress in EW direction did not exist in the Early Mesozoic.Fold deformation as well as bedding shear is the result of local structural deformation caused by the slipping structure,which is obviously contractive to the typical EW trend thrusting in the west of Ordos block and should be paid attention to in research.