The topography and relative amount of erosion which till-sheets suffer is sometimes used as a measure of identification and correlation. The method, however, is at best, only qualitative in character, and personal equation enters altogether too largely to make the test generally serviceable. Nevertheless, recently, it becomes possible to devise a methodical scheme of comparing tills, or of determining their ages based upon cosmical data, and relief expression assumes new interest and quantitative character. Thus, contrasted relief expression of the Ashuawa till, the Des Moines lobe of the Wisconsin group of glaciations the till derived from the Keewatin center of ice dispersion, when compared with the topography of the tills occurring just outside of the Ashuawa border, gives time-evaluations surprisingly different, as well as surprisingly precise, from previous empirical results.
Proceedings of the Iowa Academy of Science
©1933 Iowa Academy of Science, Inc.
"Contrasted Till Reliefs,"
Proceedings of the Iowa Academy of Science, 40(1), 135-135.
Available at: https://scholarworks.uni.edu/pias/vol40/iss1/67