Shelf-edge trajectories and stratal stacking patterns: Their sequence-stratigraphic significance and relation to styles of deep-water sedimentation and amount of deep-water sandstone

摘要

Using a seismic database from the Qiongdongnan Basin in the South China Sea, this study demonstrates that shelf-edge trajectories and stratal stacking patterns are reliable, but understated, predictors of deep-water sedimentation styles and volumes of deep-water sand deposits, assisting greatly in locating sand-rich environments and in developing a more predictive and dynamic stratigraphy. Three main types of shelf-edge trajectories and their associated stratal stacking patterns were recognized: (1) flat to slightly falling trajectories with negative trajectory angles (T-se) (-2 degrees to 0 degrees) and negative shelf-edge aggradation to progradation ratios (dy/dx) (-0.04 to 0) and associated progradational and downstepping stacking patterns with low clinoform relief (R-c) (150-550 m [492-1804 ft]) and negative differential sedimentation on the shelf and basin (A(s)/A(b)) (-0.6 to 0); (2) slightly rising trajectories with moderate T-se (0 degrees-2 degrees) and medium dy/cLx (0-0.04), and associated progradational and aggradational stacking patterns with intermediate R-c (250-400 m [820-1312 ft]) and intermediate A(s)/A(b) (0-0.6); and (3) steeply rising trajectories with high T-se (2 degrees-6 degrees) and high dy/dx (0.04-0.10) and associated dominantly aggradational stacking patterns with high R-c (350-650 m [1148-2132 ft]) and high A(s)/A(b) (1-2). Each trajectory regime represents a specific stratal stacking patterns, providing new tools to define a model-independent methodology for sequence stratigraphy.