THE TRANSFORMATION PROCESS OF MESOZOIC-CENOZOIC TECTONIC REGIME IN THE NORTH OF NORTH CHINA

The north of North China is situated in the overlapping area of Paleo-asian ocean tectonic system and Pacific ocean tectonic system.The geological facts of the regional unconformity,the evolution of Mesozoic-Cenozoic fault and basin in the area show that there are five compression deformations in Mesozoic-Cenozoic period.They are the compressions in the end of Middle Triassic (the compression deformation before Laohugou Formation or Xingshikou Formation, ≥ 215Ma),Early Jurassic (that before Haifanggou Formation or Jiulongshan Formation ≥ 178Ma),Late Jurassic (that before Yixian Formation or Donglingtai Formation, ≥ 135Ma),Cretaceous (that before Paleogene,65Ma) and Paleogene(that before Neogene,25Ma).The five compressions are short in time.There are six periods of sedimentary basin formation occurring among the five time compressions,that is longer in time,more gently and extensional in tectonic activity.The six periods of sedimentary basin formation are Early and Middle Triassic,Late Triassic and Early Jurassic,Middle and Late Jurassic,Cretaceous,Paleogene,Neogene and Quaternary.There are obvious extensional characteristics in Middle and Late Jurassic,Cretaceous,Paleogene,Neogene and Quaternary.That is,the Mesozoic-Cenozoic tectonic evolution process in the north of North China is an alternatively developing process of intracontinental (or intraplate) basin sedimentation and compression deformation in the basement of North China Craton.Both of compression and extension are all important,the compression from strong to weak,the extension from weak to strong in the process,and extension stays longer than the compression in time.The compression and extension occurred alternatively,compression structures and extension structures developed alternatively in the structrure evoltion. The tectonic regime transformation process in the north of North China records the continental dynamic process of tectonic regime transformation from the convergent tectonic regime of Paleo-asian ocean tectonic system to the subducting tectonic regime of Pacific ocean tectonic system.