Stratotype

{{Short description|Reference location for a specific type of rock layering (strata)}}

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File:Barun_Goyot_Formation,_Khulsan_locality,_Mongolia.png, Mongolia]]

In geology, a stratotype or type section is the physical location or outcrop of a particular reference exposure of a stratigraphic sequence or stratigraphic boundary. If the stratigraphic unit is layered, it is called a stratotype, whereas the standard of reference for unlayered rocks is the type locality.{{cite web |url=http://stratigraphy.org/upload/bak/strats.htm |title=Stratotypes and Type Localities |publisher=International Commission on Stratigraphy |access-date=20 August 2017}}

Also it can be defined as "The particular sequence of strata chosen as standard of reference of a layered stratigraphic unit."{{Quote without source|date=September 2022}}

When a stratigraphic unit is nowhere fully exposed, the original type section may be supplemented with reference sections covering the full thickness of the unit. A reference section may also be defined when the original type section is poorly exposed, or for historical units which were designated without specifying a type section according to more modern standards.{{cite journal |author=North American Commission on Stratigraphic Nomenclature |title=North American Stratigraphic Code |journal=AAPG Bulletin |date=November 2005 |volume=89 |issue=11 |doi=10.1306/07050504129 |url=https://ngmdb.usgs.gov/Geolex/resources/docs/AAPG_Bull-89_NACSN-Code.pdf |access-date=8 August 2020 |page=1563|bibcode=2005BAAPG..89.1547. }}