Characteristics of Wisconsinan Glacial Tills in Indiana and Their Influence on Argillic Horizon Development

Abstract

AbstractIn relatively young soil landscapes the parent material largely controls the properties of soils formed on it. Glaciers of the Tazewell subage (15 000–21 000 yr ago) covered the northern two‐thirds of Indiana and glaciers of the Cary subage (15 000–12 000 yr ago) covered the northern third. Particle size distribution, calcium carbonate equivalent (CCE), and calcite‐dolomite ratio were determined by standard soil characterization procedures on pedons sampled mainly during the course of the soil survey to represent till‐derived soils. These data were grouped into classes according to geographic areas defined by major end moraines and recognized ice‐margin positions and by new boundaries that separate areas shown to have different kinds of till in this study. Tazewell‐age till is mainly loam in texture and has a CCE between 200 and 300 g kg−1 (20 and 30%), but some in the eastern part of the state has CCE around 350 to 400 g kg−1. The Cary‐age till in the north‐central part of the state also has loam (to sandy loam) texture and CCE around 200 to 250 g kg−1. In a series of concentric Cary‐age moraines in the northeast, average clay content increases from 27 to 37% and CCE decreases from 310 to 170 g kg−1 northeastward, reflecting increasing lacustrine influence in the younger tills. The clay content of the B horizon of till‐derived soils is a function of the clay content, CCE, and age of the glacial till parent material.