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Biozones types. Each rectangle represents bodies of sedimentary rocks and each line a different taxon. The arrows indicate the taxon first or last appearance.

Biostratigraphic unit or biozones are intervals of geological strata that are defined on the basis of their characteristic fossil taxa.

A biostratigraphic unit may be defined on the basis of a single taxon or combinations of taxa, on relative abundances of taxa, or variations in features related to the distribution of fossils. The same strata may be zoned differently depending on the diagnostic criteria or fossil group chosen, so there may be several, sometimes overlapping, biostratigraphic units in the same interval.

The length of time represented by a biostratigraphic zone is called a biochron. The International Commission on Stratigraphy defines the following types of Biozones:[1]

See alsoEdit


  1. ^ "Biostratigraphic Units". International Commission on Stratigraphy. Retrieved 11 May 2018.