CENOZOIC SUBSIDENCE IN BOHAI BAY BASIN:CHARACTERISTICS AND DYNAMIC MECHANISM

Abstract

The characteristics of development and distribution of Cenozoic faults, amount of extension, and the temporal-spatial variation rules for subsidence of sediments in Bohai Bay Basin were analyzed based on previous study results. Analysis of the deep structures was made to investigate the dynamic mechanism for the Cenozoic subsidence. The results show that in the uplifting period development of faults controls the transition of deposition or subsidence centers, while at the end of the depressing period, accelerated subsidence whose center is Bozhong Depression occurs and shows a tendency of transition from the center to its adjacent depressions. It can be concluded that development of faults, deposition, and subsidence was controlled by the stress field generated from the plate movement, and subsidence of sediments was resulted from the horizontal extension and vertical thermal thinning of lithosphere in the uplifting period. The accelerated subsidence of sediments in the postrift uplifting period may result from the vertical change in density of the lithosphere and its following quick thermal decay.