zone

noun

(Gr. zônê: belt) (As biostratigraphic zone) A unit of rock characterized by a clearly defined fossil content. To avoid confusion with other types of zone the term `biozone` (short for `biostratigraphic zone`) is preferred by many authorities, although the term `biozone` is also used in a different sense. The term is usually qualified to denote the type of zone. See acme zone; Assemblage Zone; Concurrent Range Zone; Lineage Zone; Oppel Zone; Range Zone; Subzone; Taxon Range Zone; Teilzone; Zonule; and Index Fossil.