There are still problems connected with the Dakota sandstone, though that formation was named and described 60 years ago and has been under investigation by many geologists at frequent intervals ever since. Even such simple questions as its stratigraphic limits and its areal extent have not received answers of sufficient clearness to be generally accepted, and its mode of origin is still a subject of discussion.
The typical exposures from which the formation took its name are in the bluffs bordering the Missouri River valley “back of the town of Dakota,” a village in northeastern Nebraska about 6 miles south of Sioux City, Iowa, but the outcrops which were early studied and from which the first collections of both plants and mollusks were obtained are distributed along both banks of the Missouri from Ponca, Nebraska, to Tekamah, Nebraska, a . . .