Kansan glaciation was used by early geomorphologists and Quaternary geologists to subdivide glacial and nonglacial deposits within north-central United States from youngest to oldest and are as follows: As developed between 1894 and 1909, the Kansan Stage was based on a model that assumed that the Pleistocene deposits contained only two glacial tills and one volcanic ash bed within Nebraska and Kansas.
[1][2][3][4] In time, the stratigraphy of Pleistocene deposits was found to be far more complex than the two glacial tills and one volcanic ash bed on which the Yarmouthian, Kansan, Nebraskan, and Aftonian glacial – interglacial nomenclature was originally based.
Detailed research by Boellstorff demonstrated that the two glacial tills and one ash bed stratigraphic model, on which the Yarmouthian, Kansan, Nebraskan, and Aftonian glacial – interglacial nomenclature was based, was completely wrong.
[8] As a result, the basic assumptions on which the Yarmouthian (interglacial), Kansan (glacial), Aftonian (interglacial), and Nebraskan (glacial) nomenclature was originally defined was found to be lacking any scientific basis.
As a result, this nomenclature was abandoned by Quaternary geologists in North America and merged into the Pre-Illinoian Stage.