Formation · Cretaceous
Ripley Formation
Late Cretaceous unit, Mississippi · Alabama · Tennessee · Georgia
The Ripley Formation of Mississippi and Alabama is a Maastrichtian marine sand that produces Exogyra costata oysters, Sphenodiscus and Discoscaphites ammonites, Baculites, shark teeth and Enchodus fangs in creek beds around Ripley, Booneville and Blue Springs. It shares its fauna with the Coon Creek Formation and New Jersey's Navesink. Oysters are common and cheap; a complete Sphenodiscus with its shell is a good find.
| Country | United States |
|---|---|
| Region | Mississippi, Alabama, Tennessee, Georgia |
| Age | Maastrichtian, Late Cretaceous |
| Age range | ~72–66 Ma |
| Group | Selma Group |
| Macrostrat rank | Fm· Macrostrat |
| Macrostrat age | 71.2–67 Ma· Macrostrat |
| Lithology | sand, sandstone, clay, marl, chalk· Macrostrat |
| Environment | transition zone/lower shoreface, offshore, deltaic indet., marine, deep subtidal shelf· Macrostrat |
| Macrostrat columns | 6 column(s) sampled from 8 unit(s)· Macrostrat |
| Members (Macrostrat) | Chiwapa Sandstone, Coon Creek, McNairy Sand· Macrostrat |
| PBDB collections | 120 collections, 1819 occurrences· Paleobiology Database |
Collecting and legality
Ripley outcrops in Mississippi and Alabama are creek beds and road cuts on private land; road-cut collecting is tolerated in some counties but ask the state DOT and landowners. Alabama has no state fossil law for invertebrates on private land.
Lithology and setting
Glauconitic sands, sandy marls and thin limestones of the Selma Group, deposited on the Mississippi Embayment shelf.
Commonly recorded taxa (PBDB)
Genera most often recorded from this unit in the Paleobiology Database (first 200 occurrences): Turritella (22), Paladmete (9), Euspira (8), Volutomorpha (7), Anchura (5), Graciliala (5), Pugnellus (Pugnellus) (5), Creonella (4), Drilluta (4), Gyrodes (4), Morea (4), Bellifusus (3), Beretra (3), Cylichna (3), Graphidula (3).
Source: Paleobiology Database
Elsewhere
- Macrostrat: 1742
- macrostratConcept: 3573
- PBDB: strata:Ripley
- Wikidata: Q7335617
- Macrostrat stratigraphic name
- PBDB occurrences for this unit
- Wikipedia: Ripley Formation
- Mindat: Ripley Formation
Cite this article
Stratum Study. "Ripley Formation" (Formation). Stratum Study pack 2026.09, as of 2026-09-19. https://stratum.black/study/formations/ripley-formation. Accessed 2026-09-20.
@misc{stratum-ripley-formation,
title = {Ripley Formation},
author = {{Stratum Study}},
howpublished = {\url{https://stratum.black/study/formations/ripley-formation}},
year = {2026},
note = {Formation article, Stratum Study pack 2026.09, as of 2026-09-19; sources: stratum, macrostrat, pbdb, wikidata, commons. 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.