major division of Pleistocene time and deposits in North America (the Pleistocene Epoch occurred from 1,600,000 to 10,000 years ago). The Nebraskan Glacial Stage is the oldest generally recognized Pleistocene episode of widespread glaciation in North America; the Nebraskan was named for deposits in the state of Nebraska, although representative exposures in that state are rather poorly developed. The Nebraskan throughout North America is not well known; although its position as the earliest recognized of four Pleistocene glaciations in the Midwestern United States is well established, much remains to be done to delineate that position more precisely. Nebraskan deposits are best developed in Missouri, Nebraska, Iowa, and Kansas. Elsewhere, deposits designated as Nebraskan are not considered reliable. Authenticated Nebraskan deposits are rich in clays.