The Pleistocene deposits of Wisconsin consist of a complex sequence of deposits differing in origin, age, lithology, thickness, and extent. This book presents additions and revisions to the original lithostratigraphic classification of deposits published in 1984 and the supplement published in 1988. The Lexicon contains definitions of 15 formations and their 48 members.

A compilation of the new formal geologic names introduced into the literature from 1981 to 1985 in the United States and Puerto Rico.

The Wisconsinan Stage and its Altonian, Farmdalian, Woodfordian, Twocreekan, and Valderan Substages are described as time-stratigraphic units of the Pleistocene of Illinois and Wisconsin.