Group

A lithostratigraphic unit of two or more formations that share a lithological character or a common origin. The Green River Formation belongs to no group; the Judith River Formation belongs to the Montana Group.

Sources

International Commission on Stratigraphy — International Stratigraphic Guide (abridged)
North American Commission on Stratigraphic Nomenclature — North American Stratigraphic Code (2005)

Cite this article

Stratum Study. "Group" (Glossary). Stratum Study pack 2026.09, as of 2026-09-16. https://stratum.black/study/glossary/group. Accessed 2026-09-20.

BibTeX · CSL-JSON

@misc{stratum-group,
  title        = {Group},
  author       = {{Stratum Study}},
  howpublished = {\url{https://stratum.black/study/glossary/group}},
  year         = {2026},
  note         = {Glossary article, Stratum Study pack 2026.09, as of 2026-09-16; sources: stratum. Accessed 2026-09-20.}
}

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