Till, Tazewell Till. Kansan Till, Till of Iowa
11 Compositional and
Kansan and Tazewell tills can be distinguished by compositional and textural properties throughout portions of Buena Vista, Cherokee, Clay and O'Brien counties in northwest Iowa. Kansan till contains more clay than silt or sand while Tazewell till is composed of nearly equal portions of clay, silt and sand. Coarse sand is more abundant in Tazewell till than Kansan till. Siliceous rounded shale grains are common in Tazewell till but scarce or absent in Kansan till. Igneous and metamorphic rock fragments are more common in the coarse sand of Kansan than Tazewell till. Significantly more carbonate grains occur in the medium sand fraction of Tazewell till than Kansan till. The lithology of Tazewell till suggests ice occupied the Minnesota-Des Moines rivers' lowland by 20,000 radiocarbon years before the present.
Proceedings of the Iowa Academy of Science
© Copyright 1974 by the Iowa Academy of Science, Inc.
Van Zant, Kent
"Compositional and Textural Analyses of Kansan and Tazewell Till in a Portion of Northwest Iowa,"
Proceedings of the Iowa Academy of Science: Vol. 81:
, Article 11.
Available at: http://scholarworks.uni.edu/pias/vol81/iss3/11