Pedogenesis and Cementation in Calcareous Till in Indiana
- S. L. McBurnett and
- D. P. Franzmeier
Glacial till is extensive in the north central USA. In Indiana, it is calcareous and dense and has high strength and low hydraulic conductivity. It limits root growth and water movement. Its strength has been attributed to compression by thick glacial ice resting on till during deposition. It is not known if chemical cementation also contributes to its strength. In some soils, argillans coat the large prisms in the till-derived C horizons, and in others, calcans coat the prisms. The objective of this study was to learn if the kind of cutans indicates how water moves through till and if some of the till's strength is due to chemical cementation. We sampled six pedons in Delaware County, Indiana, to a depth of 3 m. Soils with argillans in the till-derived upper C horizon had outwash strata 2 to 3 m below the surface, and those with calcans lacked outwash. We postulate that argillans indicate that water moves through planar voids in the till and into outwash strata and calcans indicate that the planar voids end in the till. To look for possible cementing agents, we extracted soil samples with acid oxalate (o), citrate-bicarbonate-dithionite (d), and NaOH (n) and determined Fe, Al, and Si in the extracts. We also determined soil strength with a modulus of rupture test. Strength was higher in Cd horizons than in the solum, so strength was lost during soil formation. Strength was positively correlated with extractable Si (Sio, Sid, and/or Sin) and CaCO3 equivalent and was negatively correlated with clay and extractable Fe and Al. We conclude that the strength of the glacial till C horizons is due in part to weak cementation by silica, carbonates, or both.
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