Incorporating simple erosion into structural forward models: The effects of regional erosion on growth strata geometry

Abstract

Growth strata in fault-related folds record interactions between fault kinematics and sedimentation. In folded growth strata, syn-deformational erosion is evidenced by angular unconformities within hangingwall strata and missing section within footwall strata. In many cases, the footwall may be entirely eroded. Erosion complicates horizon correlation across faults, interpreting structural evolution, and has significant implications for burial history. This paper presents a new approach to structural fault-related fold forward modeling that parameterizes model surfaces by age as well as depth. By including surface age, we can define complex burial histories with periods of regional 2-dimensional erosion that acts vertically on fault-related folds. The fold models are computed using established kinematic methods that quantitatively relate folding to fault shape by parameters such as shear angle and displacement. Organizing the model stratigraphy by age allows us to define footwalls where younger surfaces erode into older surfaces. In hangingwall folds, this produces angular unconformities where younger fold surfaces intersect and truncate older folds. This modeling technique is applied to a seismic section from the Bohai rift basin in China. The model matches the natural growth folds and angular unconformities, giving quantitative insight into the deformational and depositional history of the rift basin.