# Petrified Forest Member

> Mediated Wiki article. Canonical URL: https://mediated.wiki/source/Petrified_Forest_Member
> Markdown URL: https://mediated.wiki/source/Petrified_Forest_Member.md
> Source: https://en.wikipedia.org/wiki/Petrified_Forest_Member
> Source revision: 1352885791
> License: Creative Commons Attribution-ShareAlike 4.0 International (https://creativecommons.org/licenses/by-sa/4.0/)

Lithostratigraphic layer of the Chinle formation

Petrified Forest Member Stratigraphic range: late Triassic, 240–215 Ma PreꞒ Ꞓ O S D C P T J K Pg N Petrified Forest Member at its type location, north of Tiponi Point, Petrified Forest National Park Type member Unit of Chinle Formation Underlies Rock Point Formation Overlies Poleo Formation Lithology Primary Mudstone Other Sandstone, siltstone Location Coordinates 35°04′26″N 109°46′48″W / 35.074°N 109.780°W / 35.074; -109.780 Region New Mexico Country United States Type section Named for Petrified Forest, Navajo and Apache Counties, AZ[1] Named by Herbert E. Gregory Year defined 1947 Petrified Forest Member (the United States) Show map of the United States Petrified Forest Member (Arizona) Show map of Arizona

The **Petrified Forest Member** is a [stratigraphic unit](/source/Stratigraphic_unit) of the [Chinle Formation](/source/Chinle_Formation) in [Arizona](/source/Arizona), [Colorado](/source/Colorado), [New Mexico](/source/New_Mexico), [Nevada](/source/Nevada), and [Utah](/source/Utah).[2] It preserves [fossils](/source/Fossils) dating back to the [Triassic](/source/Triassic) [period](/source/Period_(geology)).

## Subunits

Beds (are in alphabetical order, asterisks (*) indicate usage by the U.S. Geological Survey, other usages by state geological surveys):[2]

- Capitol Reef Bed (UT*)

- Correo Sandstone Bed (NM*)

- **Sonsela Sandstone Bed** (AZ*,NM*)

In the Chama Basin of New Mexico, the Chinle Formation is promoted to group status and the Petrified Forest Formation has the following members:[3]

- Painted Desert Member

- Mesa Montoso Member

The Mesa Montosa Member is up to 22 meters (72 feet) thick and is mostly composed of [sandstone](/source/Sandstone) (44%) and [mudstone](/source/Mudstone) (35%), with a lesser proportion of [siltstone](/source/Siltstone) (20%). The color is reddish brown to brown and the sandstone is thinly bedded and ripple laminated.

The Painted Desert Member is up to 176 meters (577 feet) thick and is primarily reddish brown [bentonitic](/source/Bentonite) mudstone. The name was originally applied to the beds above the Sonsela Sandstone Bed in [Petrified Forest National Park](/source/Petrified_Forest_National_Park) in eastern Arizona. Correlative beds of similar lithology are found throughout west-central and central New Mexico and the [Four Corners](/source/Four_Corners). The Black Forest Bed within this member has a maximum age of 213 ± 1.7 [Ma](/source/Ma_(unit)) based on [detrital zircon geochronology](/source/Detrital_zircon_geochronology), with an actual age estimated as 209 Ma. This places the upper part of the Painted Desert Member in the latest [Norian](/source/Norian) [age](/source/Age_(geology)).[4]

## Fossils

The Snyder quarry, discovered by amateur fossil hunter Mark Snyder near the town of [Abiquiu, New Mexico](/source/Abiquiu%2C_New_Mexico), in 1998, is an unusually productive and diverse bone bed in the Petrified Forest Formation. Abundant charcoal suggests a mass kill due to a paleowildfire. Fossils include [archosaurs](/source/Archosaur), [procolophonids](/source/Procolophonid), [metoposaurid](/source/Metoposaurid) amphibians, [semionotid](/source/Semionotiformes) fish, a [decapod](/source/Decapoda), a [conchostracan](/source/Conchostracan), and [unionid](/source/Unionid) bivalves.[5]

## See also

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

- [List of fossiliferous stratigraphic units in New Mexico](/source/List_of_fossiliferous_stratigraphic_units_in_New_Mexico)

- [Paleontology in New Mexico](/source/Paleontology_in_New_Mexico)

## Footnotes

1. **[^](#cite_ref-FOOTNOTEGregory1950_1-0)** [Gregory 1950](#CITEREFGregory1950).

1. ^ [***a***](#cite_ref-FOOTNOTEGEOLEX2020_2-0) [***b***](#cite_ref-FOOTNOTEGEOLEX2020_2-1) [GEOLEX 2020](#CITEREFGEOLEX2020).

1. **[^](#cite_ref-FOOTNOTELucasZeiglerHeckertHunt2005_3-0)** [Lucas et al. 2005](#CITEREFLucasZeiglerHeckertHunt2005).

1. **[^](#cite_ref-FOOTNOTERiggsAshBarthGehrels2003_4-0)** [Riggs et al. 2003](#CITEREFRiggsAshBarthGehrels2003).

1. **[^](#cite_ref-FOOTNOTEZeiglerHeckertLucas2005_5-0)** [Zeigler, Heckert & Lucas 2005](#CITEREFZeiglerHeckertLucas2005).

## References

- ["Geolex Petrified Forest Member entry"](https://ngmdb.usgs.gov/Geolex/Units/PetrifiedForest_9600.html). *ngmdb.usgs.gov*. [U.S. Geological Survey](/source/U.S._Geological_Survey). 24 Sep 2018. Retrieved 27 January 2019.

- [Gregory, H. E.](/source/Herbert_E._Gregory) (1950). ["Geology and geography of the Zion Park region, Utah and Arizona"](https://pubs.usgs.gov/pp/0220/report.pdf) (PDF). *Geological Survey Professional Paper*. [doi](/source/Doi_(identifier)):[10.3133/PP220](https://doi.org/10.3133%2FPP220). [ISSN](/source/ISSN_(identifier)) [0096-0446](https://search.worldcat.org/issn/0096-0446).

- [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.

- Riggs, N.R.; Ash, S.R.; Barth, A.P.; Gehrels, G.E.; Wooden, J.L. (2003). "Isotopic age of the Black Forest Bed, Petrified Forest Member, Chinle Formation, Arizona: An example of dating a continental sandstone". *Geological Society of America Bulletin*. **115** (11): 1315. [doi](/source/Doi_(identifier)):[10.1130/B25254.1](https://doi.org/10.1130%2FB25254.1).

- Zeigler, Kate E.; Heckert, Andrew B.; Lucas, Spencer G. (2005). ["Taphonomic analysis of a fire-related Upper Triassic vertebrate fossilassemblage from north-central New Mexico"](https://nmgs.nmt.edu/publications/guidebooks/downloads/56/56_p0341_p0354.pdf) (PDF). *New Mexico Geological Society Field Conference Series*. **56**: 341–354. Retrieved 25 May 2020.

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