Excerpt from Soils of the Eastern United States and Their Use X: The Marshall Silt Loam Not infrequently, however, there are found within the sub-soil concretions and accumulations of lime carbonate, and occasionally the limy remains of shells, principally of land forms of organic life. The Marshall silt loam is derived from the extensive body of fine silty rock powder which overspreads a considerable proportion of the central prairie States, mantling the older rock formations and covering the underlying glacial till to varying depths. This silty material doubtless originated from the outpouring of turbid water through the melting of the glacial ice during one of the later stages of its recession. It was widely distributed over the central portion of the Mississippi drainage region, and there is good evidence to show that when the surface of this material became dried and powdery it was taken up by the winds and thus distributed even over the higher elevations of that region hi the form of a thin mantle of loess. In fact the Marshall silt loam is one of several important soil types derived directly from the partial weathering of this loess mantle. It constitutes the brown prairie areas, stone free, and gently rolling to undulating in its characteristic surface features. The Marshall silt loam and other soils of the Marshall series are thus distinguished from the soils of the Miami series, which are light colored and derived from the weathering of the glacial till, and also from the black soils of the Carrington series, which resemble it in color, but have also been derived principally from ice-laid materials. It is separable from the soils of the Knox series, which also owe their origin to the surface layer of loess, in that the latter are distinguished by light-colored surface soils and are found within the timbered areas as contrasted with the prairie areas in which the darker Marshall soils occur. The black soils of the Waukesha series usually occur to the northward of the regions occupied by the Marshall silt loam and its associates, and the Waukesha soils are derived from the coarser outwash laid down directly by the action of moving water. The Marshall silt loam may be briefly characterized as the most important soil of that series, and as the brown to black silty prairie soil formed from the modification of the surface materials of the loess. Surface Features And Drainage. Throughout its entire extent the Marshall silt loam is marked by nearly level, slightly undulating, or gently rolling surface topography. Only where the larger streams have cut deep trenches are sloping areas found within this type. These, even, are infrequent since the eroded and sloping bluffs of the loess along the stream drainage ways are most frequently timbered and possess the lighter colored surface soils, thus falling within the Knox series as contrasted with the Marshall. About the Publisher Forgotten Books publishes hundreds of thousands of rare and classic books. Find more at www.forgottenbooks.com This book is a reproduction of an important historical work. Forgotten Books uses state-of-the-art technology to digitally reconstruct the work, preserving the original format whilst repairing imperfections present in the aged copy. In rare cases, an imperfection in the original, such as a blemish or missing page, may be replicated in our edition. We do, however, repair the vast majority of imperfections successfully; any imperfections that remain are intentionally left to preserve the state of such historical works.