Eagle Sandstone

{{Short description|Geological formation in Montana, USA}} {{Infobox rockunit | name = Eagle Sandstone | image = Eagle SS.jpg | caption = Eagle Sandstone above Billings, MT | type = Geological formation | age = Late Cretaceous | period = Campanian | prilithology = Sandstone | otherlithology = Sandy shale | namedfor = | namedby = | region = Montana | country = | coordinates = | unitof = | subunits = | underlies = Claggett Shale, Judith River Formation | overlies = Telegraph Creek Formation, Niobrara Shale | thickness = 100 to 350 feet | extent = | area = | map = | map_caption = }}

The '''Eagle Sandstone''', originally the '''Eagle Formation''', 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.<ref>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 [http://www.mbmg.mtech.edu/pdf_100k/billings-gm59.pdf]</ref>

Dinosaur fossils have been recovered from the formation.<ref name="cretaceousdistribution">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}}.</ref>

Weathering and erosion of the formation has created natural arches, hoodoos and other picturesque features of the Upper Missouri River Breaks National Monument.<ref>[https://archive.today/20130409223027/http://www.blm.gov/mt/st/en/fo/umrbnm/geology1.html Geology of the Upper Missouri River Breaks National Monument, U.S. Department of the Interior, Bureau of Land Management]</ref>

==Vertebrate paleofauna== * "Ornithomimus" grandis - Pes.<ref name="table-5-1-113">"Table 5.1," in Weishampel, et al. (2004). Page 113.</ref>

==See also== {{Portal|Earth sciences|Paleontology|Dinosaurs}} * List of dinosaur-bearing rock formations * List of fossiliferous stratigraphic units in Montana * Paleontology in Montana

==References== {{Reflist}}

==Bibliography== * {{cite web|title= Fossilworks: Gateway to the Paleobiology Database|author= ((Various Contributors to the Paleobiology Database))|url= https://www.fossilworks.org/|access-date= 17 December 2021|archive-date= 19 August 2022|archive-url= https://web.archive.org/web/20220819182839/https://www.fossilworks.org/|url-status= dead}}

Category:Shale formations of the United States Category:Cretaceous Montana Category:Campanian Stage Category:Sandstone formations of the United States Category:Geologic formations of Montana