摘要
In the Cretaceous Yuanan Basin, a graben on the northwest of the Jianghan Basin, there occur a variety of macrodeformation mechanisms including deformation bands, faults, joints, veins and stylolites. Mainly based upon the abutting or crosscutting relationship between the deformation structures, the authors recognized four tectonic phases, in which paleostresses were inferred. The first two phases are extensional and formed during the rifting of late Cretaceous. The latter two phases are compressional and were formed during the post-rifting after the Late Cretaceous. The inferred horizontal large stresses are directed from NNE to SSW, and from NWW to SEE, respectively, indicating a strong tendency of clockwise rotation with time.