A bioevent or bio-event (a shortening of 'biotic event' or 'biological event') is an event recognised in a sequence of

sedimentary rock Sedimentary rocks are types of rock that are formed by the accumulation or deposition of mineral or organic particles at Earth's surface, followed by cementation. Sedimentation is the collective name for processes that cause these particles ...

s, where there is a significant change in the biota as recorded by assemblages of fossils over a relatively short period of time. It has been defined as "short-term (hours or days to

kyrs KYRS, known as "Thin Air Community Radio", is a non-profit, non-commercial, full-power community radio station in Spokane, Washington (licensed to Medical Lake, Washington) at 88.1 MHz FM. The station has a translator, K222BG, at 92.3 FM, lic ...

) locally, regionally, or interregionally pervasive changes in the ecological, biogeographical, and/or evolutionary character of biotas that are isochronous or nearly so throughout their range". Bioevents either relate to diversification of a particular fossil group or a reduction, these may equate to

speciation Speciation is the evolutionary process by which populations evolve to become distinct species. The biologist Orator F. Cook coined the term in 1906 for cladogenesis, the splitting of lineages, as opposed to anagenesis, phyletic evolution withi ...

events or

extinction event An extinction event (also known as a mass extinction or biotic crisis) is a widespread and rapid decrease in the biodiversity on Earth. Such an event is identified by a sharp change in the diversity and abundance of multicellular organisms. I ...

s, or may only represent migration. Records of the appearance and disappearance of particular taxa at a single locality are insufficient to define a bioevent.

References

{{Extinction Stratigraphy