Curtis Formation

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

Curtis Point, namesake for the Curtis Formation visible as the light gray strata.

Curtis Formation
Stratigraphic range: Callovian PreꞒ Ꞓ 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	39.126665°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

Light-colored beds of the Curtis Formation in abrupt contact with the underlying Entrada Formation. This contact marks the J3 unconformity,

Description

Lightly-colored Curtis Formation at Wild Horse Butte

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

The formation was first described by Gilluly and Reeside in 1928 and named for exposures in the northeast San Rafael Reef at Curtis Point (39.126665°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]