Raven Ridge
Raven Ridge is a starkly visible sedimentary rock exposure on an ancient tributary of the Green River, located in Rio Blanco County, Colorado and Uintah County, Utah, USA. It is managed by the Bureau of Land Management. The ridge contains a diverse selection of rare plants unique to the state of Colorado. Embedded in its shales is one of the richest collections of insect fossils from the Eocene Period in North America. It is forbidden to remove items from the site without a permit.[2]
The exposed layered sedimentary rocks of the ridge are at least 65 million years old and provide a window into the boundary between two geological periods, the Cretaceous and Tertiary, known as the K–T boundary.[1]
Geology
The Raven Ridge rock exposures provide an opportunity to understand this part of Earth’s history. This section through a sequence of rock layers that were formed 65 million years ago, has become exposed because of its later tectonic history. The outcrops span the geological time period that includes the boundary between the Cretaceous and Tertiary periods, the K–T boundary. This was the time interval during which a vast number of plant and animal species, including dinosaurs, disappeared completely from the fossil record.[1] At the southern edge of Raven Ridge are found the only available surface coal beds in the area.[3]
The rocks of Raven Ridge were originally deposited on or near a shore line as horizontal sedimentary layers within the Uinta Basin. Uplift and folding associated with the later stages of the Laramide Orogeny subsequently tilted them into a nearly vertical position.[1][4]
Plants
Raven Ridge is the habitat for eight endemic 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.[2][5]
Fossils
Found at the summit of the ridge are a multitude of perfectly preserved fossil gastropods.[2]
Notes
- ^ a b c d "Raven Ridge, Colorado : Image of the Day". earthobservatory.nasa.gov. Retrieved 2009-10-11.
- ^ a b c "Raven Ridge - Colorado State Parks". parks.state.co.us. Retrieved 2009-10-11. [dead link]
- ^ U.S. Geological Survey. "Bulletin - United States Geological Survey, Issue 415". books.google.com. Retrieved 2009-10-13.
- ^ Picard, M. Dane. "AAPG/Datapages, Inc. DOI Citation". search.datapages.com. Retrieved 2009-10-11.
- ^ "Plants of Raven Ridge, near Rangely, CO, Rio Blanco Co. [Rio Blanco Co(s), Colorado]" (PDF). Colorado Native Plant Society. Retrieved 2009-10-11.
External links
- Eaton, Jeffrey (1989). "Evidence of Reworked Cretaceous Fossils and their Bearing on the Existence of Tertiary Dinosaurs". The Society of Economic Paleontologists and Mineralogists. JSTOR. Retrieved 2009-10-11.
{{cite web}}: Unknown parameter|coauthors=ignored (|author=suggested) (help) - Woodburne, Michael O. "Late cretaceous and cenozoic mammals of North America". books.google.com. Retrieved 2009-10-11.