Figure 6. Conceptual contrast between lithostratigraphy and sequence stratigraphy. Sequence stratigraphic surfaces are event-significant and mark changes in depositional trends. In this case, their timing is controlled by the turnaround points between transgressions and regressions. Lithostratigraphic surfaces are highly diachronous facies contacts. Note that the system tracts and sequence boundaries cross the formation boundaries. Each system tract is composed of three depositional systems in this example and is defined by a particular depositional trend; i.e., progradational or retrogradational (after Catuneanu et al., 2005).