Interstratified 1:1–2:1 Mineral Formation in a Polygenetic Soil from Southern Ohio

Abstract

AbstractA polygenetic soil from southern Ohio, formed by loess deposition on a pre‐existing Sangamon paleosol, was examined to determine if the lithologic discontinuity has affected subsequent clay‐mineral weathering or formation. Analyses of the <0.2 µm clays indicated that cation exchange capacities (CECs) and total Mg, K, and Fe contents were lowest near the interface between the loess and underlying paleosol at a depth of approximately 65 cm; in contrast, total Al contents were highest in this zone. An interstratified 1:1–2:1 mineral was identified in materials surrounding the loess‐paleosol contact and was concentrated in the 2.03 g/cm3‐density fraction of the <0.2 µm clay using density‐gradient centrifugation. Alkylammonium exchange of the 2.03 g/cm3‐density fraction demonstrated that the 2:1 component of the interstratified mineral was heterogeneous in charge and included layers characteristic of both smectite and vermiculite. Soil properties and depth distribution of the interstratified mineral suggest a pedogenic origin.