| Tokio Formation | |
| Type: | Formation |
| Age: | Cretaceous |
| Namedfor: | Tokio, Hempstead County, Arkansas |
| Namedby: | Hugh Dinsmore Miser and Albert Homer Purdue[1] |
| Region: | Arkansas, Oklahoma |
| Country: | United States |
| Unitof: | none |
| Subunits: | none |
| Underlies: | Brownstown Marl |
| Overlies: | Woodbine Formation |
| Thickness: | up to 300 feet[2] |
The Tokio Formation is a Late Cretaceous geologic formation in Arkansas and Oklahoma.[2] Named in 1919 by Hugh Dinsmore Miser and Albert Homer Purdue in their study of Arkansas.[1] They assigned the town of Tokio, Hempstead County, Arkansas as the type locality, but did not designate a stratotype for this unit.