A distinction in stratigraphy is made between conventions that need to be stable, and therefore regulated by codes for formal use, and those that evolve with developing science. Some stratigraphic codes and guides, in adding categories to the essential minimum, have both weakened the code and given a spurious authority to matters beyond regulation. Moreover, the tendency to multiply categories has confused the logic of what is being done.
The essential stratigraphic code is the procedure to establish all rock bodies internationally as formal lithic units in a neutral (nongenetic) category for basic reference common to all disciplines. The procedure is also available to consolidate rules, which are already virtually agreed upon, and for expressing age in terms of both chronostratic and numerical time divisions. Beyond these space-time framework categories, guidance as to conventions may be more suitable than regulation with respect to categories involving contingent elements of new observations and opinion, for example, biostratigraphy, magnetostratigraphy, tectonostratigraphy, climatostratigraphy, and sequence stratigraphy.