Geodiversity refers to the full variety of natural geologic (rocks, minerals, sediments, fossils, landforms, and physical processes) and soil resources and processes that occur in the park. A product of the Geologic Resources Inventory, the NPS Geodiversity Atlas delivers information in support of education, Geoconservation, and integrated management of living (biotic) and non-living (abiotic) components of the ecosystem.
Geologic Features and Processes
Sweeping mesas, deep canyons, and fjord- like lakes abound in Curecanti, attracting recreational enthusiasts from around the world. Curecanti’s three reservoirs, named for corresponding dams on the Gunnison River, form the center of Curecanti National Recreation Area. Blue Mesa Lake is Colorado's largest body of water. Morrow Point Lake marks the beginning of the Black Canyon of the Gunnison. Below these two, Crystal Lake is the site of the Gunnison Diversion Tunnel, a National Historic Civil Engineering Landmark.
Through incredible erosion, the Gunnison River has exposed a wide range of rock types, from 1.7 billion year old gneiss and schist to Mesozoic – Cenozoic fossiliferous sedimentary rocks and modern unconsolidated sediments.
The steep, “black” walls of neighboring Black Canyon of the Gunnison are composed of Precambrian granites, gneisses, gabbros, diorites, pegmatites, and schists. The canyon itself is considered one of the best exposures of these ancient rocks in the world.
Directly atop the Precambrian rocks, lie Mesozoic and Cenozoic sedimentary strata. No Paleozoic sedimentary rocks exist in the Black Canyon – Curecanti area. The absence of Paleozoic strata creates an unconformity, indicating that approximately 370 million years of earth history are missing from this landscape. The Entrada Sandstone, Wanakah Formation, and Morrison Formation represent Jurassic time in the area. The fossils and depositional structures within these rocks record a vast array of Jurassic climates and environments.
Above the Jurassic rocks are the Cretaceous sandstones, shales, and coal beds of the Dakota Sandstone and Burro Canyon Formation. The muds of the Mancos Shale, the volcanic breccia of the Cimarron Ridge Formation, and the brown shales and calcareous sandstones of the Fruitland Formation and Pictured Cliffs Sandstone complete the Cretaceous strata at Black Canyon – Curecanti.
At the end of the Laramide orogeny volcanic activity erupted across the area resulting in large deposits of volcanic ash, tuff, and breccia. These and other Tertiary igneous rocks cap the regions mesas today. Specific formations include West Elk Breccia, Blue Mesa Tuff, Dillon Mesa Tuff, and Carpenter Ridge Tuff.
Today, Quaternary silts, sands, and gravels are preserved in the canyons and surface depressions of Black Canyon- Curecanti as terrace deposits, alluvium, and colluvium. They represent only a fraction of the deposits that once spread across this area, only to be subsequently stripped from the region by the relentless process of erosion.
The Curecanti Needle is located about 7.2 km (4.5 mi) downstream from Blue Mesa Dam near Sapinero, Colorado. It is a spirelike monolith rising nearly 244 m (800 ft,) composed of an intrusive igneous rock called the Curecanti Quartz Monzonite. This name was applied by J. Fred Hunter in 1925. The quartz monzonite is Precambrian in age and forms an irregular, rather flat laccolith, roughly centered around Curecanti Needle. The laccolith is a pluton roughly 5.6 km (3.5 mi) across from west to east and 3.2 km (2 mi) from north to south (Hansen, 1964).
The Dillon Pinnacles are comprised of West Elk Breccia. The West Elk Breccia contains solidified lava flows intermixed with coarse fragments of material resulting from the explosive destruction of previous volcanic features. The volume of the West Elk Breccia is enormous, remnants of the formation exceed 305 m (1000 ft) in thickness and conservative estimates of the formations original volume exceed 625 cubic km (150 cubic miles).
A popular hike in the park leads to the Dillon Pinnacles which typify the erosional formations contained within the West Elk Breccia. Cliffs, crags, pillars, windows and assorted erosional hoodoos abound.
The fossil rich Morrison Formation is exposed within Black Canyon - Curecanti and dinosaur fossils continue to be found locally in this formation. Other units, such as the Mancos Shale and the Dakota Sandstone, also contain fossils that should be catalogued.
All NPS fossil resources are protected under the Paleontological Resources Preservation Act of 2009 (Public Law 111-11, Title VI, Subtitle D; 16 U.S.C. §§ 470aaa - 470aaa-11).
Geology Field Notes
Students and teachers of college-level (or AP) introductory geology or earth science teaching courses will find that each park's Geologic Resource Inventory report includes the Geologic History, Geologic Setting, and Geologic Features & Processes for the park which provides a useful summary of their overall geologic story. See Maps and Reports, below.
Curecanti National Recreation Area is a part of the Southern Rocky Mountains Physiographic Province near it's indistinct boundary with the Colorado Plateaus Physiographic Province to the west, and the park shares its geologic history and some characteristic geologic formations with regions that extend well beyond park boundaries.
- Scoping summaries are records of scoping meetings where NPS staff and local geologists determined the park’s geologic mapping plan and what content should be included in the report.
- Digital geologic maps include files for viewing in GIS software, a guide to using the data, and a document with ancillary map information. Newer products also include data viewable in Google Earth and online map services.
- Reports use the maps to discuss the park’s setting and significance, notable geologic features and processes, geologic resource management issues, and geologic history.
- Posters are a static view of the GIS data in PDF format. Newer posters include aerial imagery or shaded relief and other park information. They are also included with the reports.
- Projects list basic information about the program and all products available for a park.
Related ArticlesCurecanti National Recreation Area
National Park Service Geodiversity AtlasThe servicewide Geodiversity Atlas provides information on geoheritage and geodiversity resources and values within the National Park System. This information supports science-based geoconservation and interpretation in the NPS, as well as STEM education in schools, museums, and field camps. The NPS Geologic Resources Division and many parks work with National and International geoconservation communities to ensure that NPS abiotic resources are managed using the highest standards and best practices available.
For more information on the NPS Geodiversity Atlas, contact us.