ABSTRACT

Some writers and speakers have problems with clear usage of stratigraphic terminology, a topic made more acute by the appearance of the complex 1983 North American Code and revisions in progress of the 1976 International Guide. The basic categories of stratigraphic units are 1) material; 2) nonmaterial; 3) hybrid. Examples are the well-known rock (lithostratigraphic), time (geochronologic), and time-rock (chronostratigraphic) units, respectively. Lesser-known categories include magnetostratigraphic, lithodemic, pedostratigraphic, unconformity-bounded, and diachronic units.

Both formal and informal stratigraphic units are recognized. All words in formal units are capitalized. Only the geographically derived name in informal units is generally capitalized. Inadequate distinction between time and place words, both formal and informal, leads to unnecessary confusion. Misuse of early versus lower and late versus upper is prevalent.

Publications such as lexicons and correlation charts are recommended as initial sources of stratigraphic information. Naming, revising, and abandoning formal stratigraphic nomenclature is governed by specific rules laid down in the Code and Guide.

In illustrations of stratigraphic units, it is important to distinguish clearly between scales of time and position. Strata are not measured in years, nor time in meters!