Glossary · Stratigraphy
Formation
The basic unit of lithostratigraphy: a body of rock distinguished by its lithology, mappable at the surface, and named for a place (a type locality).
The basic unit of lithostratigraphy: a body of rock distinguished by its lithology, mappable at the surface, and named for a place (a type locality). A formation is defined by rock type, not by age, and can be diachronous.
Sources
Cite this article
Stratum Study. "Formation" (Glossary). Stratum Study pack 2026.09, as of 2026-09-16. https://stratum.black/study/glossary/formation. Accessed 2026-09-20.
@misc{stratum-formation,
title = {Formation},
author = {{Stratum Study}},
howpublished = {\url{https://stratum.black/study/glossary/formation}},
year = {2026},
note = {Glossary article, Stratum Study pack 2026.09, as of 2026-09-16; sources: stratum. Accessed 2026-09-20.}
} Citations carry the pack version and the article's as-of date so they resolve to the same text later. The facts themselves belong to the sources listed below; cite those for the science.