Curtis Formation
Stratigraphic range : Callovian Pre? ? O S D C P T J K Pg N ↓
Curtis Formation type
Type	Formation
Unit of	San Rafael Group
Underlies	Summerville Formation
Overlies	Entrada Sandstone
Lithology
Primary	Sandstone
Other	Mudstone , limestone
Location
Coordinates	39°07′36″N 110°26′51″W  /  39.126665°N 110.447615°W  / 39.126665; -110.447615
Region	Utah
Country	United States
Type section
Named for	Curtis Point, Emery County, Utah
Named by	Gilluly and Reeside
Year defined	1928

The Curtis Formation is a geologic formation in Utah . It preserves fossils dating back to the Callovian age of the Jurassic period .

Description [ edit ]

The Curtis Formation is composed of shallow marine sandstone , with thin beds of mudstone and minor limestone and gypsum . The sandstone is grayish-green in color and flat bedded or cross bedded. The presence of glauconite and marine invertebrate fossils indicates it was laid down in a shallow marine environment that became hypersaline towards the end of deposition. It represents a high stand of the Sundance Sea in the Callovian . ^[1]

History of investigation [ edit ]

The formation was first described by Gilluly and Reeside in 1928 and named for exposures in the northeast San Rafael Reef at Curtis Point ( 39°07′36″N 110°26′51″W  /  39.126665°N 110.447615°W  / 39.126665; -110.447615 ). Pipiringos and Imlay reassigned the Curtis as a member of the Stump Formation in 1979, ^[2] but this was rejected by Peterson in 1988. ^[3]

Footnotes [ edit ]

See also [ edit ]

• List of fossiliferous stratigraphic units in Utah
• Paleontology in Utah

References [ edit ]

• Gilluly, James; Reeside, J.B. Jr. (1928). "Sedimentary rocks of the San Rafael Swell and some adjacent areas in eastern Utah". Shorter Contributions to General Geology, 1927: U.S. Geological Survey Professional Paper . 150-D: D61?D110.
• Lucas, Spencer G.; Anderson, O.J. (November 1992). "The Middle Jurassic Summerville Formation, northern New Mexico" (PDF) . New Mexico Geology . 14 (4) . Retrieved 4 June 2020 .
• Peterson, Fred (1988). "Stratigraphy and nomenclature of Middle and Upper Jurassic rocks, western Colorado Plateau, Utah and Arizona". Revisions to Stratigraphic Nomenclature of Jurassic and Cretaceous Rocks of the Colorado Plateau: U.S. Geological Survey Bulletin . 1633-B: B13-56.
• Pipiringos, G.N.; Imlay, R.W. (1979). "Lithology and subdivisions of the Jurassic Stump Formation in southeastern Idaho and adjoining areas". Unconformities, Correlations, and Nomenclature of Some Triassic and Jurassic Rocks, Western Interior United States: U.S. Geological Survey Professional Paper . 1035-C: C1?C25.
• 
  Entrada (orange) and Curtis formations exposed in a road cut, Green River Cutoff Road. They are separated by the J3 unconformity.
• 
  Lower and middle members of the Curtis Formation, Green River Cutoff Road, Emery County, Utah.