Comparative soil development of Quaternary paleosols of the central UnitedStates

Buried soils in the central United States aid in deciphering stratigraphy a nd chronology by being stratigraphic markers. Such soils may provide a reco rd of many Quaternary events, particularly that of climatic change. Intergl acial soils like the Sangamon Soil may have formed for over 100 000 years, during which the climate shifted from cold to warm to cold again. Interstad ial soils formed under cooler conditions and for less time. In this paper, we review our knowledge of Quaternary paleosols in the central United State s with emphasis on Indiana and through comparison with the type localities. In Indiana, the Sangamon Soil is the most widespread buried soil of interg lacial rank. Exposures of the Sangamon Soil reveal a range of characteristi cs that are related to soil-forming factors (Jenny, H., 1941. Factors of So il Formation. McGraw-Hill, New York, 281 pp; Jenny, H., 1980. The Soil Reso urce: Origin and Behavior: Ecological Studies 37. Springer, New York); the most important of these factors include parent materials, soil drainage, an d the duration of soil development. How long a buried soil formed may be de termined by whether it is an interglacial or an interstadial soil. Thus, th e Sangamon Soil can serve as a standard to which other soils, both intergla cial and interstadial, can be compared. The most widespread interstadial so il in the central United States is the Middle Wisconsinan Farmdale/Sidney S oil. Exposures of this soil are less common than for the interglacial Sanga mon Soil, although enough data are available to provide an additional basis for evaluation of other soils. Based upon a semi-quantitative ranking of s oil-development by an assemblage of characteristics, we have numerically de fined soil development for well-developed, moderately developed, and weakly developed categories. The most strongly developed buried soils in the cent ral United States are the early Pleistocene soils and the Yarmouth Soil. Bo th the Yarmouth Soil and the Sangamon Soil may be more strongly developed i n Indiana than in their respective type areas in Iowa and Illinois. Both th e Yarmouth Soil and the Sangamon Soil are more strongly developed than the surface soil. The primary reason seems to be the greater time intervals ove r which the Yarmouth and Sangamon soils developed. As expected, interstadia l soils are much more weakly developed than interglacial soils. Soil develo pment is also a function of soil drainage. In general, better-drained profi les of the Sangamon Soil are the best-developed soils. (C) 2000 Elsevier Sc ience B.V. All rights reserved.