Stratigraphy and Genesis of Polygenetic Soils on the Illinoian Till Plain of Southwestern Ohio
1987
Ransom, M. D. | Smeck, N.E. | Bigham, J. M.
Three pedons each of Clermont (Typic Glossaqualfs) and Avonburg (Aeric Fragiaqualfs) soils were investigated on the Illinoian till plain of southwestern Ohio in order to evaluate parent material stratigraphy and to determine if paleosols were substantially altered following burial by a thin mantle of loess. The relationship between fragipan development and paleosol properties was also examined. The soils were found to have formed in 57 to 69 cm of Late Wisconsinan (Peoria) loess overlying a composite Early Wisconsinan and Sangamon paleosol. The Sangamon paleosol, which was most strongly developed at approximately 150 to 200 cm, was formed in Illinoian till. The material from about 70 to 140 cm consisted of a mixture of Early Wisconsinan loess and Illinoian till with till characteristics dominating. Evidence for a mixed zone in the upper paleosol included (i) a higher silt content than the lower paleosol, (ii) a maximum in elemental Ca in the total silt fraction, and (iii) an abundance of pedotubules in up to 50% of some horizons suggesting that mixing was caused by bioturbation. Modification of the paleosols has occurred as evidenced by recharge with secondary carbonates and bases leached from the overlying loess. A fragipan was identified in only one Avonburg pedon that had a clay content of 27% in the upper part of the paleosol as compared to 31 to 38% for the other pedons. Fragipans appear to have formed in these soils only if the clay content of the upper part of the paleosol is currently less than about 30%.
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