stratotype

thumb|250px|The Khulsan locality, which is the stratotype of the Barun Goyot Formation, [[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.

It can also be defined as "The particular sequence of strata chosen as standard of reference of a layered stratigraphic unit."