Key Aspects of A Horizon Formation for Selected Buried Soils in Late Holocene Alluvium; Southern Prairies, USA

Two soil profiles containing multiple buried soils were described and sampled to determine the relative impact of past alluvial sedimentation and melanization on buried A horizon formation. Total organic carbon content (TOC), particle size analysis, and soil morphology were combined to detect buried soils and determine the influence of melanization, cumulization, sedimentation, and welding on A horizon formation. The incorporation of phytolith content supported the interpretations made by combining TOC, soil morphology, and clay-free sand content in all but one of the seven surface and buried soils investigated. Soils predominantly formed by melanization, but two thick and dark buried A horizons formed by cumulization during multiple small flood events. Large flood events, as identified by medium to thick beds, were common throughout the soil profiles, marked the top of the buried A horizons, and ended periods of soil formation, Phytolith content versus depth mirrored changes in TOC and can be used as a proxy for soil stabilization by plants. The addition of diatom identification to grass-type phytolith analysis assisted in the recognition of a period of excess wetness during soil formation for one buried soil.