Soils of Indian Mounds in Northeastern Iowa as Benchmarks for Studies of Soil Genesis

A study was made to evaluate the degree of horizon development in seven prehistoric Indian mounds of known age in northeastern Iowa. Comparisons were made between the data obtained for the Indian mound soil profiles and two virgin, loess‐derived Fayette profiles from the landscape near the mounds. The parent materials for the mound soils were the leached upper horizons of the soils under and immediately adjacent to the mounds. Morphologically, the mound profiles exhibited pronounced A 1 horizons, weak color and structural A 2 horizons, and incipient B horizons. Differences in profile development among the mounds were attributed to differences in mound age. The development of soil profiles in the mounds has been the most pronounced during the first 1,000 years. The mounds have reached their greatest present horizon expression in a period of no more than 2,500 years, and are similar in many respects to the Fayette soils which have developed over a period of no more than 14,000 years.