The Contributions of J. A. Udden to an Understanding of Iowa Geology

Johan August Udden served on the faculty of Augustana College from 1888 until 1911. His research during that time was directed toward an understanding of the geology of areas close at hand, the region around Rock Island and nearby areas in Iowa and Illinois. Udden\u27s most significant contributions to Iowa geology were in his treatment of 1) Paleozoic, Cretaceous, and Quaternary stratigraphy; 2) subsurface geology, including information on bedrock elevations and topography; 3) characteristics and origin of the loess. Most of this information was included in the Annual Reports of the Iowa Geological Survey published between 1899 and 1903. He made important contributions to the study of the Devonian of eastern Iowa. He was the first to recognize cyclic sedimentation in Pennsylvanian strata. He compiled subsurface information on the thickness of Pennsylvanian rocks in Jefferson County and was probably among the first to present such information on a map. He prepared what may be the earliest maps of bedrock topography, in Muscatine and Louisa counties. He was an unwavering proponent of the eolian hypothesis for the origin of loess. He noted that modern wind deposits have the same particle-size distribution as does the loess, and in the process of making these analyses he devised a widely used size-grade scale