# Rock Point Formation

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Geologic formation in the United States

Rock Point Formation Stratigraphic range: late Triassic PreꞒ Ꞓ O S D C P T J K Pg N Rock Point Formation capped by Entrada Formation, near Youngsville, New Mexico Type Formation Unit of Chinle Group Underlies Wingate Sandstone Overlies Petrified Forest Formation Thickness 70 m Lithology Primary Siltstone Other Fine sandstone Location Coordinates 36°31′29″N 109°33′22″W / 36.5247221°N 109.5560845°W / 36.5247221; -109.5560845 Region Utah, Arizona, New Mexico Country United States Type section Named for Rock Point School, Apache County, Arizona Named by Harshbarger, J.W., Repenning, C.A., and Irwin, J.H., 1957 Rock Point Formation (the United States) Show map of the United States Rock Point Formation (Arizona) Show map of Arizona

The **Rock Point Formation** is a [geologic formation](/source/Formation_(geology)) in [New Mexico](/source/New_Mexico), [Arizona](/source/Arizona), and [Utah](/source/Utah). It preserves [fossils](/source/Fossils) dating back to the [late Triassic](/source/Late_Triassic).

## Description

The formation is up to 70 m thick and is mostly reddish-brown and grayish-red massive [siltstone](/source/Siltstone) and fine [sandstone](/source/Sandstone) beds. It is the uppermost portion of the [Chinle Group](/source/Chinle_Group) wherever it is exposed. In the Chama basin, its base is placed at the first persistent sandstone bed above the mudstones of the [Petrified Forest Formation](/source/Petrified_Forest_Formation). Its contact with the overlying [Entrada Sandstone](/source/Entrada_Sandstone) is sharp.[1]

## Fossils

The Whitaker quarry of [Ghost Ranch](/source/Ghost_Ranch), New Mexico is believed to be located in the Rock Point Formation, although these beds have also controversially been assigned to the [Owl Rock Formation](/source/Owl_Rock_Member).[1] This quarry has also been referred to as the *[Coelophysis](/source/Coelophysis)* quarry due to preserving a large number of specimens of the early [theropod](/source/Theropoda) [dinosaur](/source/Dinosaur) *Coelophysis bauri*.[2]

## History of investigation

The unit was first named by J.W. Harshbarger, [C.A. Repenning](/source/Charles_Repenning), and J.H. Irwin in 1957, who assigned [Herbert E. Gregory](/source/Herbert_E._Gregory)'s (1917) "A" division of the [Chinle Formation](/source/Chinle_Formation) to the [Wingate Formation](/source/Wingate_Formation) as the Rock Point Member. It was named for Rock Point School, located near the type exposures at Little Round Rock.[3] J.H. Stewart and coinvestigators argued in 1972 that the unit has more affinity with the Chinle,[4] and R.F. Dubiel assigned the Rock Point to the Chinle in 1989.[5] The unit has created an unusual amount of controversy, but [Spencer G. Lucas](/source/Spencer_G._Lucas) and coinvestigators raised it to formation rank within the Chinle Group in 2005.[1]

		- Bed of concretions in the Rock Point Formation near Youngsville, New Mexico

		- Fossil from Rock Point Formation

## See also

- [Earth sciences portal](https://en.wikipedia.org/wiki/Portal:Earth_sciences)
- [Utah portal](https://en.wikipedia.org/wiki/Portal:Utah)
- [Paleontology portal](https://en.wikipedia.org/wiki/Portal:Paleontology)

- [List of fossiliferous stratigraphic units in Utah](/source/List_of_fossiliferous_stratigraphic_units_in_Utah)

- [Paleontology in Utah](/source/Paleontology_in_Utah)

## Footnotes

1. ^ [***a***](#cite_ref-FOOTNOTELucasZeiglerHeckertHunt2005176_1-0) [***b***](#cite_ref-FOOTNOTELucasZeiglerHeckertHunt2005176_1-1) [***c***](#cite_ref-FOOTNOTELucasZeiglerHeckertHunt2005176_1-2) [Lucas et al. 2005](#CITEREFLucasZeiglerHeckertHunt2005), p. 176.

1. **[^](#cite_ref-FOOTNOTERinehartLucasHeckertSpielmann2009_2-0)** [Rinehart et al. 2009](#CITEREFRinehartLucasHeckertSpielmann2009).

1. **[^](#cite_ref-FOOTNOTEHarshbargerRepenningIrwin1957_3-0)** [Harshbarger, Repenning & Irwin 1957](#CITEREFHarshbargerRepenningIrwin1957).

1. **[^](#cite_ref-FOOTNOTEStewartPooleWilson1972_4-0)** [Stewart, Poole & Wilson 1972](#CITEREFStewartPooleWilson1972).

1. **[^](#cite_ref-FOOTNOTEDubiel1989_5-0)** [Dubiel 1989](#CITEREFDubiel1989).

## References

- Dubiel, R.F. (1989). ["Sedimentology and revised nomenclature of the Upper Triassic Chinle Formation and the Lower Jurassic Wingate Sandstone, northwestern New Mexico and northeastern Arizona"](https://nmgs.nmt.edu/publications/guidebooks/downloads/40/40_p0213_p0223.pdf) (PDF). *New Mexico Geological Society Field Conference Series*. **40**: 213–223. Retrieved 25 May 2020.

- Harshbarger, J.W.; Repenning, C.A.; Irwin, J.H. (1957). ["Stratigraphy of the uppermost Triassic and the Jurassic rocks of the Navajo country"](https://pubs.er.usgs.gov/publication/pp291). *U.S. Geological Survey Professional Paper*. **291**. Retrieved 25 May 2020.

- [Lucas, Spencer G.](/source/Spencer_G._Lucas); Zeigler, Kate E.; Heckert, Andrew B.; Hunt, Adrian P. (2005). ["Review of Upper Triassic stratigraphy and biostratigraphy in the Chama Basin, northern New Mexico"](https://nmgs.nmt.edu/publications/guidebooks/downloads/56/56_p0170_p0181.pdf) (PDF). *New Mexico Geological Society Field Conference Series*. **56**: 170–181. Retrieved 29 April 2020.

- Rinehart, L.F.; [Lucas, S.G.](/source/Spencer_G._Lucas); Heckert, A.B.; Spielmann, J.A.; Celesky, M.D. (2009). ["The paleobiology of *Coelophysis bauri* (Cope) from the Upper Triassic (Apachean) Whitaker quarry, New Mexico, with detailed analysis of a single quarry block"](https://econtent.unm.edu/cdm/ref/collection/bulletins/id/1285). *New Mexico Museum of Natural History & Science, A Division of the Department of Cultural Affairs Bulletin*. **45**: 260.

- Stewart, J.H.; Poole, F.G.; Wilson, R.F. (1972). ["Stratigraphy and origin of the Chinle Formation and related Upper Triassic strata in the Colorado Plateau region, with sections on sedimentary petrology by R.A. Cadigan and conglomerate studies by William Thordarson and H.F. Albee"](https://doi.org/10.3133%2Fpp690). *U.S. Geological Survey Professional Paper*. **690**. [doi](/source/Doi_(identifier)):[10.3133/pp690](https://doi.org/10.3133%2Fpp690).

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Adapted from the Wikipedia article [Rock Point Formation](https://en.wikipedia.org/wiki/Rock_Point_Formation) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Rock_Point_Formation?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.