| Straight Cliffs Formation | |
|---|---|
| Stratigraphic range: Turonian-Campanian ~ | |
_3_(30765890505).jpg) Cedar Canyon Basalt over Straight Cliffs Formation (Iron County, Utah) | |
| Type | Geological formation |
| Underlies | Wahweap Formation |
| Overlies | Tropic Shale |
| Thickness | Max. 750 m (2,460 ft) |
| Lithology | |
| Primary | Sandstone |
| Other | Siltstone, mudstone, coal, conglomerate |
| Location | |
| Region | South central Utah |
| Country |  United States |
| Extent | 3,600 km2 (1,400 sq mi) |
| Type section | |
| Named for | Straight Cliffs |
| Named by | Gregory and Moore |
| Year defined | 1931 |
The Straight Cliffs Formation is a stratigraphic unit in the Kaiparowits Plateau of south central Utah. It is Late Cretaceous (latest Turonian – early Campanian) in age and contains fluvial (river systems), paralic (swamps and lagoons), and marginal marine (shoreline) siliciclastic strata. It is well exposed around the margin of the Kaiparowits Plateau in the Grand Staircase – Escalante National Monument in south central Utah. The formation is named after the Straight Cliffs, a long band of cliffs creating the topographic feature Fiftymile Mountain.
The Straight Cliffs Formation was deposited in a marginal marine basin system along the western edge of the Cretaceous Western Interior Seaway. It is bounded below by the Tropic Shale and above by the Wahweap Formation. A variety of fossil species have been found within the Straight Cliffs including ammonites, mollusks, foraminifera, ostracods, sharks, fish, amphibians, turtles, lizards, crocodyliforms, dinosaurs, and mammals.