The Classification of the Wisconsin Glacial Stage of North Central United States

The Wisconsin glacial stage is classified on the basis of stratigraphy into six glacial substages, named, from older to younger, Farmdale, Iowan, Tazewell, Cary, Mankato, and Valders. In this paper names are proposed for the intraglacial substages not previously designated, completing the sequence as follows: These divisions fit the natural succession and provide the basis for historical and climatic interpretations of a broad scope, be they glacial advances, pauses, retreats, stagnation, eustatic changes of sea level, events beyond the ice sheet, changes of biotas, climatic changes and climatic controls, and analysis of radiocarbon dating. Valley trains were deposited during active maximum and submaximum stands of the glaciers and were in part followed by glacial torrents. The latter occurred when the icecap was being reduced and sea level was being raised. Except in the case of the Valders, another refrigeration followed, but the climatic change that halted the advance of the Valders was revolutionary. It brought on progressive stagnation and initiated the Recent about 11,000 radiocarbon years ago. This paper also gives consideration to other classifications including the one recently proposed by Frye and Willman's new classification.