A Lithosequence of Soils in Extremely Gravelly, Dolomitic

Parent Materials, Bois Blanc Island, Lake Huron

Randall J. Schaetzl

Eight extremely gravelly pedons on Bois Blanc Island were characterized, and pathways and processes of genesis were examined. The soils are developed in dolomitic gravels and cobbles, and contain 1-50% (mean 15%) fine-earth; most pedons are in coarse-loamy or skeletal particle-size families. In extremely gravelly parent materials with less than 5% fine-earth, B horizons have not formed. Accumulation of organic matter on the surface and between coarse fragments in the upper solum is the main pedogenic process in such soils (Borofolists). IN other soils, distinct eluvial and illuvial zones are present, with organic carbon, silts, fine sands and CaCO₃ being the primary constituents undergoing translocation. Quantity and mineralogical composition of the fine-earth appear to alter the pathways of pedogenesis. As the amount of fine-earth and the percentage of non-carbonate materials (derived from crystalline rocks) increase, cambic horizons with spodic morphology may develop.