Raven Ridge is a starkly visible

sedimentary rock Sedimentary rocks are types of rock that are formed by the accumulation or deposition of mineral or organic particles at Earth's surface, followed by cementation. Sedimentation is the collective name for processes that cause these particles ...

exposure located in Rio Blanco County,

Colorado Colorado (, other variants) is a state in the Mountain West subregion of the Western United States. It encompasses most of the Southern Rocky Mountains, as well as the northeastern portion of the Colorado Plateau and the western edge of t ...

and

Uintah County Uintah County ( ) is a county in the U.S. state of Utah. As of the 2020 United States Census the population was 35,620. Its county seat and largest city is Vernal. The county was named for the portion of the Ute Indian tribe that lived in the b ...

Utah Utah ( , ) is a state in the Mountain West subregion of the Western United States. Utah is a landlocked U.S. state bordered to its east by Colorado, to its northeast by Wyoming, to its north by Idaho, to its south by Arizona, and to it ...

, USA. It is managed by the

Bureau of Land Management The Bureau of Land Management (BLM) is an agency within the United States Department of the Interior responsible for administering federal lands. Headquartered in Washington DC, and with oversight over , it governs one eighth of the country's la ...

. The ridge contains a diverse selection of rare plants unique to the state of Colorado.

Geology

The Raven Ridge and the adjacent parallel Squaw Ridge are northwest striking rock exposures which provide an opportunity to understand this part of Earth's history. This section through a sequence of rock layers that were deposited between ~53-49 million years ago, has become exposed because of its later

tectonic Tectonics (; ) are the processes that control the structure and properties of the Earth's crust and its evolution through time. These include the processes of mountain building, the growth and behavior of the strong, old cores of continents k ...

history. The

outcrop An outcrop or rocky outcrop is a visible exposure of bedrock or ancient superficial deposits on the surface of the Earth. Features Outcrops do not cover the majority of the Earth's land surface because in most places the bedrock or superficial ...

s span the geological time interval that includes the early and middle portions of the

Eocene Epoch The Eocene ( ) Epoch is a geological epoch that lasted from about 56 to 33.9 million years ago (mya). It is the second epoch of the Paleogene Period in the modern Cenozoic Era. The name ''Eocene'' comes from the Ancient Greek (''ēṓs'', "daw ...

. During this time, ancestral horses, primates, and rodents, among many other mammal groups, were common at Raven Ridge. At the southern edge of Raven Ridge are found the only available surface coal beds in the area. The rocks of Raven Ridge were originally deposited on or near a shore line as horizontal sedimentary layers within the

Uinta Basin The Uinta Basin (also known as the Uintah Basin) is a physiographic section of the larger Colorado Plateaus province, which in turn is part of the larger Intermontane Plateaus physiographic division. It is also a geologic structural basin in ...

. Uplift and folding associated with the later stages of the

Laramide Orogeny The Laramide orogeny was a time period of mountain building in western North America, which started in the Late Cretaceous, 70 to 80 million years ago, and ended 35 to 55 million years ago. The exact duration and ages of beginning and end of the o ...

subsequently tilted them into a nearly vertical position.

Plants

Raven Ridge is the habitat for eight

endemic Endemism is the state of a species being found in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also found elsew ...

rare plant species: ''Penstemon grahamii'' (Graham's beardtongue), ''Penstemon albifluvis'' (White River beardtongue), ''Astragalus lutosus'' (Dragon milkvetch), ''Aquilegia barnebyi'' (Mancos columbine), ''Cryptantha rollinsii'' (Rollins's catseye), ''Parthenium ligulata'' (Colorado feverfew), ''Eriogonum ephedroides'' (ephedra buckwheat), and ''Phacelia incana'' (hoary phacelia). Numerous other plants are found there as well.

Fossils

Found at the summit of the ridge are a multitude of perfectly preserved fossil

gastropod The gastropods (), commonly known as snails and slugs, belong to a large taxonomic class of invertebrates within the phylum Mollusca called Gastropoda (). This class comprises snails and slugs from saltwater, from freshwater, and from land. T ...

Notes

External links

* * {{authority control Paleogene geology Landforms of Rio Blanco County, Colorado Landforms of Uintah County, Utah Bureau of Land Management areas in Colorado Ridges of Colorado