Chalk Butte Formation
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TypeFormation
ThicknessAbout 538 feet
PrimaryTuffaceous sandstones, siltstones, conglomerates
OtherTuff, ash beds, freshwater limestone
| Chalk Butte Formation | |
|---|---|
| Stratigraphic range: Tortonian-Zanclean (Hemphillian) ~ | |
| Type | Formation |
| Thickness | About 538 feet |
| Lithology | |
| Primary | Tuffaceous sandstones, siltstones, conglomerates |
| Other | Tuff, ash beds, freshwater limestone |
| Location | |
| Coordinates | 43°36′N 117°30′W / 43.6°N 117.5°W |
| Approximate paleocoordinates | 44°18′N 114°36′W / 44.3°N 114.6°W |
| Region | Malheur County, Oregon |
| Country | United States |
| Type section | |
| Named for | Chalk Butte |
  Chalk Butte Formation (the United States)  Chalk Butte Formation (Oregon) | |
The Chalk Butte Formation is a geologic formation in Oregon, which forms a part of the Idaho Group.[1] It preserves fossils dating back to the Neogene period.[2] It was proposed along with the Grassy Mountain Basalt Formation and the Kern Basin Formation as a division of the Idaho Group rocks in the Mitchell Butte Quadrangle.[3] The predominant rock types are tuffaceous sandstones, siltstones, and conglomerates with smaller amounts of tuff, ash beds, and freshwater limestone.[3] A partial section at the type location determined the formation to be about 538 feet thick.[3]