Model-independent sequence stratigraphy

Stratal stacking patterns provide the basis for the definition of all units and surfaces of sequence stratigraphy. The same types of stacking patterns may be observed at different scales, in relation to stratigraphic cycles of different magnitudes. At each scale of observation, stacking patterns define systems tracts, and changes in stacking pattern mark the position of sequence stratigraphic surfaces. The construction of a framework of systems tracts and bounding surfaces fulfills the practical purpose of sequence stratigraphy. Beyond this framework, model-dependent choices with respect to the selection of the 'sequence boundary' may be made as a function of the mappability of the various types of sequence stratigraphic surface within the studied section. Sequence stratigraphic frameworks are basin-specific in terms of timing and scales of the component units and bounding surfaces, reflecting the interplay of global and local controls on accommodation and sedimentation. A stratigraphic sequence corresponds to a cycle of change in stratal stacking patterns, defined by the recurrence of the same type of sequence stratigraphic surface in the rock record. Sequences, as well as component systems tracts and depositional systems, can be observed at all stratigraphic scales. Sequences of any scale may include unconformities of equal and/or lower hierarchical ranks, whose identification depends on the resolution of the data available. The relative ranking of sequences of different scales is defined by their strati graphic relationships, as lower rank sequences are nested within higher rank systems tracts. Despite this nested architecture, the stratigraphic framework is not truly fractal because sequences of different scales may differ in terms of underlying controls and internal composition of systems tracts. A scale-independent approach to methodology and nomenclature is key to the standard application of sequence stratigraphy across the entire range of geological settings, stratigraphic scales, and types of data available.