Argillic Horizon Expression and Classification in the Soils of Two Michigan Hydrosequences

Abstract

Two hydrosequences in central Michigan were investigated to evaluate the degree of Bt horizon expression as influenced by the depth and duration of soil saturation. Each hydrosequence was sampled in duplicate and consisted of well or moderately well, somewhat poorly, and poorly drained soils. Total clay ratios, I/E indices (fine clay/total clay of the illuvial zone divided the fine clay/total clay of the eluvial zone), and argillan development were greatest in the well‐drained soils and decreased with decreasing depth to and increasing duration of soil saturation. One of the poorly drained soils lacked Bt horizons while one had Bt horizon expression similar to that of the somewhat poorly drained soils. The water table regimes of all poorly drained soils were similar. The poorly drained soils with Bt horizons contained relatively large amounts of smectite, particularly in the clay films, while those lacking Bt horizons contained virtually no smectite. The Bt horizons developed to a greater degree where moisture fronts penetrated the solum the greater period of the year. Where penetration was retarded by soil saturation, mineralogy contributed to the degree of Bt horizon development.

Eocene and Oligocene Paleosols of Central Oregon

“…However, the reduction spots and ferrous iron low in the Bt horizon of the type Pswa clay may be evidence of slow drainage at that level during a wet season, as in intermittently wet soils (Cremeens and Mokma, 1986). This was probably not a place of permanent seepage because Pswa paleosols lack rusty mottles or spots of iron manganese like those found in consistently waterlogged soils and in Acas and Lakim paleosols described here.…”

“…Pasct paleosols probably occupied geomorphic positions above water table, as indicated by their textural and chemical differentiation and lack of unoxidized iron. On the other hand, the drab color and inferred high content of humus together with ferrous iron near the surface as evidence of local puddling or slow drainage are indications of flat, imperfectly drained surfaces, such as fluvial terraces (Cremeens and Mokma, 1986). Such an interpretation is in accord with the likely parent material of Pasct paleosols.…”

Paleosols as Indicators of Paleoenvironment and Paleoclimate

“…Well-drained soils, where argillans become more abundant and continuous with increasing depth, show better Bt horizon development (Cremeens & Mokma 1986). However, shrink-swell processes characteristic of Vertisols may www.annualreviews.org • Paleosols and Paleoclimate 11.7 Changes may still occur before final publication online and in print disrupt the formation of argillans within Bt horizons .…”

Soils with Carbonate-rich Zones in East Central Michigan

“…The family particle-size class of the Thomas, Tappan-I, and Tappan-2 pedons was fine-loamy while that of the Lenawee variant pedon was finesilty (Table 2). According to uniformity values (Cremeens and Mokma, 1986), Tappan-2 developed in one material, loamy glacial till, and Thomas, Lenawee variant, and Tappan-l pedons developed in two materials; silt loam to silty clay lacustrine or water-sorted materials over loam glacial till. The thickness of lacustrine material varied from 20 in.…”