CONSTRAINING THE DEFORMATION AND EROSION HISTORIES OF CONTINENTAL RIFTING IN THE BOHAI BAY BASIN, CHINA

The Bohai Bay Basin in eastern China is a continental rifted basin that experienced numerous Cenozoic base level changes during extension. We have analyzed three large low-angle normal fault systems within the Bohai Bay Basin using high-quality seismic data. In each instance, erosional events associated with base level changes led to loss of footwall section and alterations to hanging-wall fold style, including the development of significant angular unconformities. We present an interactive modeling approach which recreates angular relationships between folded beds and erosional surfaces as well as hanging-wall fault-bend fold geometries. Animated model results provide quantitative constraints on fault shapes, deformation kinematics, burial and erosional history, and fault slip rates. We applied these modeling methods to three separate seismic profiles. In all three profiles, distal hanging wall beds exhibit steep rollover geometries and are overlain unconformably by shallower, less-steep structural surfaces. Models that include continuous extensional behavior along a listric fault accompanied by multiple kilometers of base level drop recreate the observed geometric sequences. Reproductions of additional shallow unconformities in two of the profiles require late-stage contractional inversion with several kilometers of slip. Interactive structural modeling that incorporates erosion thus provides a quantitative check on interpretation validity while constraining kinematic deformational behavior in the Bohai Bay Basin.