Eagle Sandstone
The Eagle Sandstone is a geological formation in Montana whose strata date back to the Late Cretaceous. It is a light to brownish gray to pale yellow-orange, fine-grained sandstone. It contains areas of crossbedding and local shale members. It contains large (up to 15 feet in diameter) sandy calcareous concretions. Its thickness varies from 100 to 350 feet due to the lens nature of the individual sandstone layers and local interbedded sandy shale layers.[1]
| Eagle Sandstone Stratigraphic range: Late Cretaceous | |
|---|---|
| Type | Geological formation |
| Underlies | Claggett Shale, Judith River Formation |
| Overlies | Telegraph Creek Formation, Niobrara Shale |
| Thickness | 100 to 350 feet |
| Lithology | |
| Primary | Sandstone |
| Other | Sandy shale |
| Location | |
| Region | Montana |
Dinosaur fossils have been recovered from the formation.[2]
Weathering and erosion of the formation has created natural arches, hoodoos and other picturesque features of the Upper Missouri River Breaks National Monument.[3]
Vertebrate paleofauna
- "Ornithomimus" grandis - Pes.[4]
gollark: Really tempted to just say "[REDACTED] you" to all my users on older browsers and rewrite this in Rust.
gollark: Apparently my JS project from some months ago won't build for some cryptic reason, the newer version of the build tool I used pulls in about 850 dependencies, and there are several security vulnerability warnings during `npm install`.
gollark: No mods, though, so it's boring.
gollark: Python is apparently fine with this.
gollark: ```python>>> import ctypes, sys>>> ctypes.memmove(id(7), id(8), sys.getsizeof(7))140001623574848>>> 78```
See also
- List of dinosaur-bearing rock formations
References
- Lopez, David A., 2000, Geologic Map of the Billings 30' x 60' Quadrangle, Montana, Geologic Map Series No. 59, Montana Bureau of Mines and Geology
- Weishampel, David B; et al. (2004). "Dinosaur distribution (Late Cretaceous, North America)." In: Weishampel, David B.; Dodson, Peter; and Osmólska, Halszka (eds.): The Dinosauria, 2nd, Berkeley: University of California Press. Pp. 574-588. ISBN 0-520-24209-2.
- Geology of the Upper Missouri River Breaks National Monument, U.S. Department of the Interior, Bureau of Land Management
- "Table 5.1," in Weishampel, et al. (2004). Page 113.
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