ABSTRACT: Some writers, speakers, and students have problems with clear usage of stratigraphic terminology, a topic made more acute by the appearance of the complex 1983 North American Stratigraphic Code, its 2005 revision, and new editions of the International Stratigraphic Guide. The basic categories of stratigraphic units are: 1) material; 2) non-material; 3) hybrid. Examples are the well-known rock (lithostratigraphic), time (geochronologic), and time-rock (chronostratigraphic) units, respectively. Biostratigraphic units (biozones) are used to describe and correlate time-rock units. Lesser-known categories include magnetostratigraphic, lithodemic, pedostratigraphic, diachronic, and unconformity-related units. Sequence-stratigraphic nomenclature, still developing, is in a state of turmoil at present. Both formal and informal stratigraphic units are recognized. All words in formal units are capitalized, except for species names in biozones. 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, late versus upper, and Ma for Myr is epidemic. Web sites and publications such as lexicons, geologic time scales, and correlation charts are recommended as initial sources of stratigraphic information. Naming, revising, and abandoning formal stratigraphic names are governed by specific rules for names to be accepted. In illustrations of stratigraphic units, it is important to distinguish clearly between scales of time and position. Strata are not measured in years, or time in meters!
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