Colton Formation
The Colton Formation is a geologic formation in Utah. Its age is based on its position between the Upper Cretaceous-Paleocene North Horn Formation and overlying Green River Formation.
| Colton Formation | |
|---|---|
| Stratigraphic range: Paleocene and Eocene | |
 Typical exposure of the Colton Formation | |
| Type | Formation |
| Underlies | Green River Formation |
| Overlies | North Horn Formation |
| Area | Central Utah |
| Thickness | 200–800 meters (660–2,620 ft) |
| Lithology | |
| Primary | Reddish mudstones and sandstones |
| Location | |
| Region | Utah |
| Country | United States |
| Type section | |
| Named by | P.T. Walton 1944 |
The name was first used by P.T. Walton[1] in 1944 for strata below the Green River Formation at the base of the Roan Cliffs, Utah. However, the type section was first given by E.M. Spieker in 1946.[2] for exposures near the town of Colton on Soldier Summit, Utah County, Utah. Previously, the strata were assigned to the Wasatch Formation, which had become a rather generic name by the US Geological Survey for mudstone-sandstone strata of Eocene age.
The formation is composed of reddish-brown to green beds of mudstone and shaly siltstone, interlayered with yellowish- to grayish-orange and grayish-brown, thin, fine- to medium-grained quartzose sandstone beds. The mudstones are locally variegated in shades of red and gray. Many sandstones are cross-bedded in large and small trough sets and the thicker sandstones are interpreted as deltaic deposits growing into Lake Flagstaff and Lake Uinta.[3]
Root structures and mudcracks are common in the mudstone beds.
The only fossil described to date is a fragmentary skeleton of the aquatic bird Presbyornis recurvirostrus[4] from a lacustrine limestone.
References
- Various Contributors to the Paleobiology Database. "Fossilworks: Gateway to the Paleobiology Database". Retrieved 17 December 2021.
- Walton, P.T., 1944, Geology of the Cretaceous of the Uinta basin, Utah: Geological Society of America Bulletin, v. 55, no. 1, p. 91-130.
- Spieker, E.M., 1946, Late Mesozoic and early Cenozoic history of central Utah, IN Shorter contributions to general geology, 1943-45: U.S. Geological Survey Professional Paper, 205-D, p. D117-D161.
- "Utah Geological Survey Interactive Map Portal". Utah Geological Survey.
- J. W. Hardy. 1959. A previously undescribed recurvirostrid from the Eocene of Utah. Auk 76(1):106-108 [type of Coltonia recurvirostra, now Presbyornis recurvirostrus]