Early concept that Aftonian paleosol developed on Nebraskan till is oversimplified. Also, the Pearlette ash which was once thought to be a single marker has now been determined to be three volcanic ash beds of different ages. A number of different tills occur at the land surface at different elevations; and the name Nebraskan has been applied to several of them, thus leading to miscorrelation of tills. As a result present knowledge leads to the conclusion that there is no single Nebraskan till, but rather tills of several ages that have been assigned to the Nebraskan. Name Nebraskan abandoned; rocks formerly designated Nebraskan are part of a grouping of 12 glaciations of pre-Illinoian, Pleistocene to late Pliocene age. Letter designations applied to the individual tills. Stratigraphic chart.

Source: GNU records (USGS DDS-6; Denver GNULEX).

Has been miscorrelated. Name has been applied to rocks of Kansan age as well as those of Nebraskan age. " ... continued use in any context will lead to miscorrelation of stratigraphic units or assignment of erroneous numerical ages or age ranges to biotic assemblages and stratigraphic units. Redefinition of the terms ... will lead to confusion of stratigraphic nomenclature." Term Nebraskan glaciation abandoned in chapter by Hallberg (this vol, p. 11-15).

Source: GNU records (USGS DDS-6; Denver GNULEX).