Genesis of Argillic Horizons in Soils Derived from Coarse-textured Calcareous Gravels
1976
Rostad, H. P. W. | Smeck, N. E. | Wilding, L. P.
Soils with fine-textured argillic horizons overlying calcareous gravel are of widespread occurrence on terraces, kames, and eskers in Ohio. The objective of this study was to determine if the argillic horizon in these soils, generally containing 25–50% clay, could develop from a calcareous gravelly deposit containing < 10% clay. Two pairs of sites were chosen, one pair developed on gravel material containing 60% carbonates, the other pair on gravel containing 40% carbonates. One member of each pair occurred on a terrace whereas the other occurred on a kame. A reconstruction technique utilizing Ti and Zr contents of the soil fraction >2 µm was used to calculate the gains and losses of various constituents in the solum relative to the parent material. The residue remaining after acid dissolution of carbonates was determined for gravel, sand, and silt fractions. The carbonate content of the C horizons ranged from as high as 90% in the 16–32 mm fraction to < 5% in the clay fraction. Dissolution of carbonates and addition of clay residue from the carbonate rocks decreased the gravel content from 75 to 52% and increased the clay content from 1.4 to 10.3%. A calculation of gains and losses for weathered solum shows substantial gains of clay, silt, and sand which is balanced by a loss of gravel. It has been proposed that the gain in sand, silt, and clay is a result of disintegration of shale, siltstone, sandstone, and crystalline lithics in the sand and gravel fractions. It is therefore concluded that fine-textured B horizons could develop from coarse-textured calcareous gravelly outwash.
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