ABSTRACT: Chemostratigraphy has evolved as a significant scientific subdiscipline of the Geosciences during the past seventy years. Chemostratigraphic data have contributed to deciphering deep-time ocean and atmospheric climates and processes, and it has become a practical correlation tool. As new instruments, methods and techniques are developed, geochemical data will add to geoscientific research and applications in new ways. However, some inconsistencies and confusion in use of the terms have developed in practice, in which objective observable data are considered as past events rather than as the record of past events. Chemical excursions documented by samples in measured stratigraphic sections and cores commonly and called â€œeventsâ€. The distinction between physical stratigraphic units and geohistorical events is commonly obscured. TheNorth American Code of Stratigraphic Nomenclature is the appropriate venue in which to present guidelines that clarify usage of chemozones as distinct from interpretations about paleoenvironmental conditions and to ensure objective testable correlation practices.