Coarse-loamy soils with glossic horizons have not been extensively studied in the upper Great Lakes region, and thus, questions remain regarding their genesis. As a first step toward resolving this problem, I examined glossic horizon development in two calcareous coarse-loamy, bisequal soils in NE Lower Michigan. Data collected from these soils were integrated with published pedogenic models to develop a unifying model that illustrates the most likely pathways of glossic horizon formation in similar soils of the region. The model involves the acidification of a calcareous parent material, followed by mechanical translocation of clay (and associated Fe-oxides) and fine silt to a preferred (illuvial) zone under oxidizing conditions. The illuvial zone, a Bt horizon, eventually functioning as an aquitard during seasonally wet periods, facilitates temporary localized saturation and change in redox status near its upper boundary. Subsequently, clay-bound Fe compounds are reduced and eluviated from the zone, resulting in the destabilization, degradation, and remobilization of illuvial cutans to form glossic features. The expression of glossic features evolve gradually as a result of micro-erosion and eluviation of clays and fine silts from preferred locations within the degrading zone, the magnitude of which follows a distinct sequence at progressive stages of the degradational process: (1) fine clay, (2) coarse clay, and finally, (3) fine silt. With time, the glossic character of the degrading zone becomes increasingly pronounced, until ultimately, little to no evidence of the former Bt horizon remains. At this point, Bt horizon morphology has progressed through glossic to an albic horizon.
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