LOESS STUDIES IN CENTRAL UNITED-STATES - EVOLUTION OF CONCEPTS

Few words in the realm of earth science have caused more debate than ' 'loess''. It is a common term that was first used as a name of a silt deposit before it was defined in a scientific sense. Because this ''lo ose'' deposit is easily distinguished from other more coherent deposit s, it was recognized as a matter of practical concern and later became the object of much scientific scrutiny. Loess was first recognized al ong the Rhine Valley in Germany in the 1830s and was first noted in th e United States in 1846 along the lower Mississippi River where it lat er became the center of attention. The use of the name eventually spre ad around the world, but its use has not been consistently applied. Ov er the years some interpretations and stratigraphic correlations have been validated, but others have been hotly contested on conceptual gro unds and semantic issues. The concept of loess evolved into a complex issue as loess and loess-like deposits were discovered in different pa rts of the US. The evolution of concepts in the central US developed i n four indefinite stages: the eras of (1) discovery and development of hypotheses, (2) conditional acceptance of the eolian origin of loess, (3) ''bandwagon'' popularity of loess research, and (4) analytical in quiry on the nature of loess. Toward the end of the first era around 1 900, the popular opinion on the meaning of the term loess shifted from a lithological sense of loose silt to a lithogenetic sense of eolian silt. However, the dual use of the term fostered a lingering skepticis m during the second era that ended in 1944 with an explosion of intere st that lasted for more than a decade. In 1944, R.J. Russell proposed and H.N. Fisk defended a new non-eolian, property-based, concept of lo ess. The eolian advocates reacted with surprise and enthusiasm. Each s ide used constrained arguments to show their view of the problem, but did not examine the fundamental problem, which was not in the proofs o f their hypothesis, but in the definition of the term. Between 1944 an d about 1950, the debates about loess reached a maximum level of compl exity. The main semantic problem was submersed in peripheral arguments about physical properties and genetic interpretations. The scholarly treatment of the subject by Fisk and Russell stimulated quality respon ses from a diversity of earth scientists interested in academic and ap plied studies, particularly gee-history, pedology, soil mechanics and stratigraphy. The long-lasting popularity of loess studies during the bandwagon era lasted to about 1970. By that time, the analytical and t echnical interests had attracted the mainstream into the fourth era wi th a focus beyond the old arguments. Although Fisk and Russell found t hemselves defending an unpopular theory, they stimulated a scientific interest in the late Quaternary history of the Mississippi Valley that may never be exceeded.