| Ogallala Formation | |
|---|---|
| Stratigraphic range: | |
 Common appearance of the "caprock" caliche beds from the middle of the Ogallala at Ash Hollow, Nebraska | |
| Type | Formation / Group |
| Sub-units | Nebraska only:
|
| Underlies | Pleistocene loess |
| Overlies | Weathered Cretaceous, Jurassic, Triassic, and Permian terrains |
| Lithology | |
| Primary | sand, gravel, caliche cementation |
| Other | chert, agate, opaline sandstone, marl, limestone, ash |
| Location | |
| Region | High Plains |
| Country | United States |
| Type section | |
| Named for | Ogallala, Nebraska |
The Ogallala Formation is a Miocene to early Pliocene geologic formation in the central High Plains of the western United States and the location of the Ogallala Aquifer.[1] In Nebraska and South Dakota it is also classified as the Ogallala Group.[2] Notably, it records the North American Land Mammal Ages (NALMAs) Hemphillian, Clarendonian, and Barstovian.[3] It also includes an excellent record of grass seeds and other plant seeds, which can be used for biostratigraphic dating within the formation. The Ogallala Formation outcrops of Lake Meredith National Recreation Area preserve fish fossils.[4] Similar specimens from the same unit are found at Alibates Flint Quarries National Monument in Texas.[4]
- ^ Cite error: The named reference
BuchananEtAlwas invoked but never defined (see the help page). - ^ "Geologic Unit: Ogallala". National Geologic Database. Geolex — Significant Publications. United States Geological Survey. Retrieved 2020-06-05.
- ^ Cite error: The named reference
LudvigsonEtAlwas invoked but never defined (see the help page). - ^ a b Cite error: The named reference
nps-fish-meredith-67was invoked but never defined (see the help page).