Tidwell Member of the Morrison Formation

Usage of Geologic Unit Name:
Tidwell Member* of Morrison Formation (AZ*,CO*,NM*,UT*)
Jurassic, Late*
Geologic Province:
San Juan basin*
Black Mesa basin*
Plateau sedimentary province*
Piceance basin*
Paradox basin*
San Juan Mountains province*
Areal Extent:

Type Locality:
Type section: NE/4 SE/4 SE/4 sec. 24, T. 22 S., R. 13 E., Emery Co., UT. Named for Tidwell Bottoms, a marshy area along San Rafael River, Emery Co., UT (Peterson, 1988).
Reference section: on east-facing cliffs of Gunnison River, western Black Canyon, Montrose Co., CO (O'Sullivan, 1992b).

Unit Name History:
First used; Areal limits (O'Sullivan, 1984). Isotopic dating (Kowallis and Heaton, 1987). Named as a basal member of Morrison Formation (Peterson, 1988). Areal limits (O'Sullivan, 1991, 1992a). Age modified; Reference; Areal limits (O'Sullivan, 1992b).


O'Sullivan, R.B., 1984, The base of the Upper Jurassic Morrison Formation in east-central Utah: U.S. Geological Survey Bulletin, 1561, 17 p.

Kowallis, B.J. and Heaton, J.S., 1987, Fission-track dating of bentonites and bentonitic mudstones from the Morrison Formation in central Utah: Geological Society of America, Geology, v. 15, no. 12, p. 1138-1142.

Peterson, Fred, 1988, Stratigraphy and nomenclature of Middle and Upper Jurassic rocks, western Colorado Plateau, Utah and Arizona, IN Revisions to stratigraphic nomenclature of Jurassic and Cretaceous rocks of the Colorado Plateau: U.S. Geological Survey Bulletin, 1633-B, p. B13-56.

O'Sullivan, R.B., 1991, Correlation of Middle Jurassic San Rafael Group and related rocks from Kane Springs, Utah to Uravan, Colorado: U.S. Geological Survey Oil and Gas Investigations
Chart, OC-134, 1 sheet.

O'Sullivan, R.B., 1992, Correlation of Middle Jurassic and related rocks from Ouray to Black Canyon, western Colorado: U.S. Geological Survey Oil and Gas Investigations Chart, OC-139, 1 sheet.

O'Sullivan, R.B., 1992, Jurassic Wanakah and Morrison Formations in the Telluride-Ouray-western Black Canyon area of southwestern Colorado: U.S. Geological Survey Bulletin, 1927, 24 p.

Bernier, Julie C., Chan, Marjorie A., 1995, Stratigraphy and sedimentology of the Late Jurassic Tidwell Member, Morrison Formation in southeastern Utah: Geological Society of America,
Abstracts with Programs, v. 32, no. 7, p. 226.

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* show accepted USGS usage.
Note that data on this page contains information that has been partly revised from bibliographic resources available via the National Geologic Map Database GEOLEX:
The URL is: https://gotbooks.miracosta.edu/gonp/coloradoplateau/lexicon/morrison_tidwell.htm
Last modified: 1/7/2011