Profile Characteristics of Some Forest-Formed Soils Derived from Iowan Till

Three profiles were collected in Bremer and Floyd counties to represent the proposed Coggon series; detailed field and laboratory studies were conducted on these profiles. The Coggon soils have developed under forest vegetation from a two-story parent material consisting of a silty mantle-pebble band-glacial till sequence. Being formed from Iowan-age glacial till, the Coggon profiles exhibit an amount of development that is low compared to other Gray-Brown Podzolic soils of Iowa. Coarser parent material might possibly explain why Coggon is less developed than the Weller soils, which are formed from presumably younger, loessial parent material. On the other hand, the lack of development in Coggon could be explained by its youth if one considers the possibility that the present geomorphic surface of the Iowan till represents a rather young pedi-sedimented surface which is more recent than the last glaciation