INFLUENCE OF UNDERLYING MATERIAL ON THE WEATHERING OF LOESS IN OHIO

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Abstract
The influence of chemical and textural discontinuities on soil development has not been well documented. In this study, weathering and clay accumulation in a thin (43 to 66 cm), Late Wisconsinan loess mantle underlain by different materials (dolomite, siltstone, sandstone, and shale residua; Illinoian and Wisconsinan glacial tills) were assessed in six pedons from southcentral Ohio. Lithological and micro-morphological evidence suggested that mixing of underlying materials with the loess was limited to the basal portion of the mantle. Chemical analyses indicated greater weathering of loess deposited over low base status or clayey materials relative to that deposited over those with high base status or loamy textures. Particle size and micromorphological and reconstructional analyses also indicated greater pedogenic clay accumulation in loess deposited over clayey materials. Apparently, the presence of acidic materials beneath the initially calcareous loess accelerated acidification and weathering within the loess mantle. In addition, fine-textured underlying materials may have impeded water movement, resulting in a wetter environment in the loess that accelerated in situ clay formation or promoted deposition of clay from suspension. We propose that enhanced weathering of parent materials just above, and as a result of contact with, a contrasting material be referred to as basal weathering. © Williams & Wilkins 1988. All Rights Reserved.