资源环境科技发展态势分析平台

We conducted a paleomagnetic study of the Upper and Lower Cretaceous red-beds in the Yibin area, in the southern part of the Sichuan Basin. High-temperature magnetic components were isolated between 580 degrees C and 695 degrees C. An ambiguous fold test resulted in alternative interpretations of the Cretaceous primary magnetization or Oligocene-Miocene remagnetization. Nevertheless, the two different interpretations of the paleomagnetic data consistently show that the Yibin area on the southern edge of the Sichuan Basin experienced clockwise rotation, relative to the eastern edge of the South China Block and Europe. A comparison with the Cretaceous and Paleogene paleomagnetic data from the northern and western part of the Sichuan Basin indicates that, except for the southeastern corner of the Sichuan Basin, the crust of the Sichuan Basin generally experienced significant clockwise rotational deformation since the early Miocene. The northeastward escape of the Songpan-Ganzi Terrane and the counterclockwise rotation of the Yangtze Fold Belt applied a right-lateral shear stress to the region surrounding the Sichuan Basin since the Miocene, which induced the passive crustal clockwise rotational deformation of the Sichuan Basin. Subsequently, the non-synchronous crustal rotational deformation of the Sichuan Basin and its surrounding blocks controlled the tectonic evolution of their boundary tectonic belts: for example, the right-lateral strike-slip movement of the Longmenshan fault belt and the southeastward extension of the Xianshuihe strike-slip fault since the Miocene.