Magnetic Fabric Characteristic of Cenozoic Sediments from Lulehe Section in the Northern Qaidam Basin,China and Its Tectonic Implications
The Qaidam Basin is the largest Cenozoic sedimentary basin on the northern part of Qinghai-Xizang Plateau,with a stratum thickness exceeding 10 km.By revealing the magnetic fabric information preserved in Cenozoic within the basin,it is possible to reconstruct the regional tectonic stress orientation,which is of great significance for exploring the tectonic deformation and dynamic mechanism in the northern part of Qinghai-Xizang Plateau.The anisotropy of magnetic susceptibility in various directions of Cenozoic strata samples from Lulehe section in the northern Qaidam Basin was measured.Subsequently,magnetic fabric information was obtained from 1 070 samples,and an analysis was conducted on the morphology of the magnetic fabric and its related parameters.The results show that the magnetic fabric of strata during 23.7-9.9 Ma in Lulehe section shows an initial deformation magnetic fabric,with its magnetic lineation indicating the direction of compression stress.The magnetic fabric of strata during 9.9-5.2 Ma is characterized by sedimentary fabric,and no obvious tectonic stress direction is recorded.After removing the effects of structural rotation using magnetic declination,variations are observed in the orientation of the compressive stress recorded by the magnetic fabric in Lulehe section over different periods,respectively.During 23.7-18.1 Ma,it gathers at～25°,revealing that the northern Qaidam Basin suffers from near SN compression stress in the Early Miocene.During 18.1-15.2 Ma,the direction of compressive stress rotates counterclockwise from～25° to～-20°.During 15.2-9.9 Ma,the direction of compressive stress rotates clockwise from～-20° to～20°.These results reveal that the compression stress direction of the northern Qaidam Basin first rotates counterclockwise(18.1-15.2 Ma)and then rotates clockwise(15.29.9 Ma)in the Middle Miocene.Based on the surrounding tectonic framework and the previous analysis of tectonic deformation,it is considered that the rotation of tectonic stress on the northern margin of Qaidam Basin since the Middle Miocene may be closely related to the superposition of bidirectional compression stress from East Kunlun and Qilian Mountains.
magnetic fabricrock magnetismtectonic straintectonic transitionCenozoicQaidam Basin
万方数据
维普
