High-resolution sequence stratigraphy of clastic shelves VII: 3D variability of stacking patterns

In the geological record, high-frequency sequences at the scale of fourth-order and lower rank stratigraphic frameworks are usually stacked to compose higher rank (lower frequency) systems tracts (i.e., sequence sets) along dip-oriented transects. Higher rank transgressive, normal regressive (highstand and/or lowstand) and falling-stage systems tracts are defined by retrogradational, upstepping progradational, and downstepping progradational stacking patterns of component high-frequency sequences, respectively. However, these stacking patterns may vary markedly along depositional strike due to lateral changes in the rates of accommodation and sedimentation, resulting in the coeval deposition of different types of higher rank systems tracts. In this case, surfaces bounding such systems tracts are diachronous along depositional strike. Moreover, if the high-frequency sequences that compose the lower frequency systems tracts are laterally continuous, the higher rank bounding surfaces are discontinuous along depositional strike, consisting of a series of stepped surfaces that can be observed in high-resolution studies. These aspects have important implications for petroleum exploration and need to be considered in high-resolution sequence stratigraphic analysis.