What is "stratotype"

n. (context geology English) A stratigraphic section used to establish a reference point on a geologic time scale.

A stratotype or type section is a geological term that names the physical location or outcrop of a particular reference exposure of a stratigraphic sequence or stratigraphic boundary. A unit stratotype is the agreed reference point for a particular stratigraphic unit and a boundary stratotype the reference for a particular boundary between strata.