| Tarkio Limestone | |
| Type: | Member |
| Age: | (Virgilian stage) |
| Period: | Late Carboniferous |
| Prilithology: | Limestone |
| Namedfor: | Outcrops in the Tarkio Valley in northwestern Missouri |
| Namedby: | G.E. Condra |
| Year Ts: | 1935 |
| Region: | Kansas |
| Country: | United States |
| Unitof: | Zeandale Limestone of Wabaunsee Group |
| Underlies: | Wamego Shale member of Zeandale Limestone |
| Overlies: | Willard Shale |
The Tarkio Limestone, is a Late-Carboniferous member of the Zeandale Formation in Kansas, extending into Nebraska, Iowa, and Missouri.[1] [2] The unit was named for outcrops in the Tarkio Valley in northwestern Missouri, however, R.C. Moore designated a typical exposure of this unit on Mill Creek, southwest of Maple Hill, Kansas. Owing to its unusual coloration, an early name for this rock was chocolate limestone.[1] This rock can be recognized by its coloration and abundant fusulinids, Triticites ventricosus, protruding from the surfaces, giving a "raspy" texture.[3]
The Tarkio Limestone forms bold bluffs along Deep Creek in southeastern Riley County, Kansas and can be easily accessed there at Pillsbury Crossing,[4] about 30miles west of Maple Hill.