In the eastern Cypress Hills the Frenchman Formation (Upper Cretaceous), a correlative of the Hell Creek in Montana, consists of a clay lithosome and a sand lithesome. Study of sections shows that either lithological unit may form the lowest unit of the Frenchman and that they may alternate vertically. Equivalence of the two lithologies is suggested also by their similar fossil content.
The Frenchman is distributed over a larger area than previously assumed. Certain sands formerly interpreted as belonging to the Eastend Formation (theFox Hills of Montana) are assigned to the Frenchman because of their fossil content. Differences in grain size, color, accessory minerals, stratification, and other characteristics can be used to distinguish Eastend sands from the sand lithosome of the Frenchman.
The Frenchman rests on a surface of erosion; the upper contact is abrupt but conformable.