Hillslope Sedimentation and Soil Formation in Northeastern Iowa

Systematic investigation of a hillslope from summit to alluvial positions revealed that particle size variations within the soil A horizons are due to sedimentological sorting. The mean particle size in the surficial sediments follows a systematic decrease within two subset systems down the hillslope. Each subset is expressible mathematically. A discordance in the backslope position is caused by truncation of a sand zone within the till underlying the surficial material. Hillslope sedimentation has also influenced accumulation of organic matter, bulk density, and cation exchange capacities in the soils formed at various positions on the slope. Profile characteristics indicate little pedogenic development; rather, many of the soil properties are inherited from the sedimentary nature of the hillslope surficial sediment.