Original Cretaceous stratigraphy discussed in O'Connor, H.G., 1968, Cretaceous System, in, Zeller, D.E., (ed.); The stratigraphic succession in Kansas: Kansas Geological Survey, Bulletin, no. 189, pp. 54-58 http://www.kgs.ku.edu/Publications/Bulletins/189/09_meso.html#CRET