Pleistocene stratigraphy, pre-Illinoian till, Wisconsinan till, surface area, clay mineralogy
Specific surface area is a property used by earth scientists to estimate the proportion of expandable clay minerals in soils. In this study, specific surface area method is shown to compare favorably with standard clay mineralogical techniques in determining gross differences in expandable clay mineral content in tills. The results of over 100 measurements on till samples from Iowa indicate undifferentiated pre-Illinoian tills from southern and southwestern Iowa have the highest specific surface area values of Iowa tills (ranging from nearly 100 to greater than 150 m2/g) and Wisconsinan Dows Formation tills have the lowest average specific surface area values (approximately 50 to 80 m2/g). Pre-Illinoian tills from eastern Iowa have significantly lower average specific surface area values than undifferentiated pre-Illinoian tills collected from southern and southwestern Iowa. Specific surface area determinations proved useful in distinguishing between pre-Illinoian till units at the formation level in eastern Iowa. The use of this property at the formation and sub-formation level in Wisconsinan tills is less diagnostic. Limited specific surface data exist for Illinoian tills, which appear to have clay mineral compositions intermediate between those of undifferentiated pre-Illinoian tills from southern and southwestern Iowa and Wisconsinan tills.
Journal of the Iowa Academy of Science
© Copyright 1992 by the Iowa Academy of Science, Inc.
Schilling, Keith E. and Gedlinske, Brian L.
"The Specific Surface Area Values for Iowa Tills,"
Journal of the Iowa Academy of Science: JIAS: Vol. 99:
, Article 5.
Available at: http://scholarworks.uni.edu/jias/vol99/iss2/5