The Tarkio Limestone, is a Late-Carboniferous member of the Zeandale Formation in Kansas, extending into Nebraska, Iowa, and Missouri.

Moore designated a typical exposure of this unit on Mill Creek, southwest of Maple Hill, Kansas.

[3] Owing to its unusual coloration, an early name for this rock was chocolate limestone.

[2] This rock can be recognized by its coloration and abundant fusulinids, Triticites ventricosus, protruding from the surfaces, giving a "raspy" texture.

[4] The Tarkio Limestone forms bold bluffs along Deep Creek in southeastern Riley County, Kansas and can be easily accessed there at Pillsbury Crossing,[3] about 30 miles (48 km) west of Maple Hill.