Genesis and Classification of Some Paleborolls and Cryoboralfs in Northern Utah

Abstract

AbstractThree soil series in northern Utah were studied to determine if the apparent surface mantle is a depositional discontinuity. Field descriptions show a dark gray silty deposit overlying thick E horizons and reddish brown, clayey skeletal B horizons. Laboratory results show an abrupt change in texture and mineralogy with amphiboles and Ca‐feldspar and zeolites in the surface deposit or upper sequum and quartz, chlorite, mica, and kaolinite in the lower sequum. The fine clay in the upper sequum of all three soils is dominated by amorphous material suggesting an early stage of weathering. Results of these studies suggest that the older soils (lower sequum) were Alfisols. Recent additions of eolian material from Lake Bonneville sediments and Snake River plain have covered the Alfisols and mollic epipedons have developed in the eolian material. These soils are now classified as Paleborolls. We suggest that Thapto extragrade classification would help identify more of the characteristics of these soils than the present classification.