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Curecanti National Recreation Area, in west-central Colorado, is three reservoirs strung along the Gunnison River — Blue Mesa, Morrow Point and Crystal — in fjord-like canyons between the Rocky Mountains and the Colorado Plateau. The water is new; the walls around it hold 1.7 billion years of rock, with 370 million years of it missing.
The area in brief
| Established | February 11, 1965, with the completion of Blue Mesa Dam |
| Where | Gunnison and Montrose Counties, beside Black Canyon of the Gunnison National Park |
| Size | about 43,000 acres |
| Known for | trout and salmon fishing, boating, hiking, camping, birding |
The rock record
| Age | Rocks | What they record |
|---|---|---|
| Precambrian, ~1.7 billion years | gneiss, schist, granite, gabbro, diorite, pegmatite | the black walls of the Black Canyon — one of the world's best exposures of such ancient rock |
| missing | no Paleozoic rock at all | an unconformity: about 370 million years of history eroded away |
| Jurassic | Entrada Sandstone, Wanakah and Morrison formations | deserts, lakes and rivers; dinosaur fossils still turn up in the Morrison |
| Cretaceous | Dakota Sandstone, Burro Canyon Formation, Mancos Shale, Cimarron Ridge breccia, Fruitland Formation, Pictured Cliffs Sandstone | coasts, seas and coal swamps |
| Paleogene | West Elk Breccia, Blue Mesa, Dillon Mesa and Carpenter Ridge tuffs | volcanic eruptions at the end of the Laramide mountain-building; they cap the mesas |
| Quaternary | terraces, alluvium, slope debris | the little left behind by erosion |
The Gunnison is still cutting: mud and debris in its water, rockfalls from the cliffs and landslides creeping into the canyon keep deepening it.
Two landmarks
Curecanti Needle above Morrow Point Reservoir. NPS photo.
- Curecanti Needle. About 4.5 miles below Blue Mesa Dam, near Sapinero, a spire rises nearly 800 feet above the river. It is carved from the Precambrian Curecanti Quartz Monzonite — a granite-like rock made mostly of feldspar — part of a flat, lens-shaped intrusion about 3.5 by 2 miles across.
- Dillon Pinnacles. A popular hike leads to cliffs, pillars, windows and hoodoos eroded from the West Elk Breccia, a mix of lava and shattered volcanic debris more than 1,000 feet thick that once amounted to more than 150 cubic miles.
The Park Service's Geologic Resources Inventory has published geologic maps and a report for Curecanti, free on the NPS DataStore. Fossils are protected by the Paleontological Resources Preservation Act of 2009.
Sources
Written from "NPS Geodiversity Atlas—Curecanti National Recreation Area, Colorado", National Park Service Geologic Resources Division, a work of the United States government in the public domain, which cites Thornberry-Ehrlich (2005) and Hansen (1964).
Dans ces collectionsCurecanti National Recreation Area
Licence : CC0 1.0 (domaine public) · Adapté de www.nps.gov
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