Cenozoic Tectonic Evolution Of Bohai Bay Basin And Its Implications On The Pacific Plate Subduction

Data shows that the North China Craton has suffered significant destructionsince Phanerozoic, however, the dynamic background of destruction is still lack ofreliable evidence. The research shows, the main control factor of the destruction is thesubduction of the Pacific plate. The Bohai Bay Basin is located in the central area ofdestruction, so take the research of the Bohai Bay Basin as a breakthrough. The studyof prototype restoration, the stretching evolution and the tectonic deformation process,figure out the migration evolution of the internal structure in Bohai Bay Basin, knowabout the dynamic background of its formation, so provide the basis for the Pacificplate subduction mechanism.In this paper, based on balanced section theory, restore the7sections whichthroughout the Bohai Bay Basin in2Dmove and the results show that the extensionalrates have obvious space and time differences. Cenozoic tectonic evolution of theBohai Bay Basin have gone through three stages, that is, faulted period,rifting-subsiding period and depression period. During Es3to Ek is the major rift timewhen have the maximum extensional rate of18.64%. In Es3to Ek, the JiyangDepression began highly faulted, and Linqing Depression also started early which wasaffected by the Taihang Mountains. Meanwhile, the extensional rate of the central partwas less than4%, and Liaohe Depression has not formed yet. When the Es3, thecentral and north part of the basin were into the peak of the rifting, indicating that theactive central had a trend toward the basin center, but the extensional rates of thesouthwest (8.97%)and northeast (18.64%)were still larger. During the Es1to Es2,faulting weakened significantly weakened and some areas came into the depressionperiod, and this time the extensional rates had the feature that east was bigger thanwest, central was bigger than north and south, indicating that the activity center hadtransferred to Bozhong. In Ed, except the extensional rates of LiaoheDepression(4.33%) and Bozhong Depression(2.6%) rose slightly and faulted twice,the extensional rates of the rest were less than1%and there were no space-timedifferences. Since the Neogene, the whole basin was into the depression period and keep calm to accept deposition.The extension direction of Bohai Bay Basin in Cenozoic mainly is NNW to NS,the faults migrating characteristics are "from north to south, from west to east"gradual change, the major activity center Neogene located in the Bozhong Depressionwhich nearby Tanlu fault.From the aspect of the shallow tectonic features, the subduction rate anddirection of Pacific Plate have changed during Cenozoic. In the main rift period ofBohai Bay Basin, the subduction rate was low, while in the rifting-depression anddepression period were high. At the beginning of Cenozoic, the subduction directionwas NNW, and later it changed to nearly EW. The migration of tectonic activity centershows that the Pacific Plate drift had a northward trend, but from the perspective ofthe direction difference between the subduction and stre, add to the weakenedsubduction force, suggesting that at this time the Pacific Plate had a trend to east. Thereason maybe is numbers of plates became active which made northeastasthenosphere creeping eastward.