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stratotype (type section) An actual rock succession, chosen at a particular locality (the type locality) to act as the standard comparison for all other chronostratigraphic or lithostratigraphic units of its ilk. Generally, the type section of a stratigraphic unit should be the rock succession originally so designated and described (the holostratotype), but circumstances may require amendment (see LECTOSTRATOTYPE; and NEOSTRATOTYPE), or amplification (see PARASTRATOTYPE; and HYPOSTRATOTYPE). However, although many similar sequences may exist, only a single stratotype at any one time can act as the standard. See also BOUNDARY-STRATOTYPE; COMPOSITESTRATOTYPE; COMPONENT-STRATOTYPE; and TYPE AREA.