摘要
The Haiyuan fault zone,one of intensive deformational zones in the northeastern Tibetan Plateau,records the information about the northeastward growth of the Tibetan Plateau.On the basis of detailed structural measuring,we proposed the sequences of the Cenozoic paleo-stress fields and the tectonic evolution of the Haiyuan fault zone.Our studies show a five-stage tectonic evolution as follows.The first was the widespread development of the basins along the Haiyuan fault zone from the Eocene to the Miocene due to the NW SE extension;secondly,the Haiyuan fault zone was featured by right strike-slip activity in the late Miocene to the Pliocene controlled by the NNE SSW compression;thirdly,the fault intensively thrusted northeastward in the Late Pliocene to the Early Pleistocene owing to the NE SW compression,which resulted in the geomorphic formation;fourthly,Late Pleistocene basins occurred,caused by the NE SW extension;lastly,Haiyuan fault zone was marked by sinistral strike-slip movement since the later Late pleistocene,and some pull-part basins formed along the fault.The neotectonics of the Haiyuan fault zone will provide some new structural evidences for probing the northeastward extending of the Tibetan Plateau.