Soils Their Properties and Management Author:Thomas Lyttleton Lyon, Elmer Otterbein Fippin, Harry Oliver Buckman Purchase of this book includes free trial access to www.million-books.com where you can read more than a million books for free. This is an OCR edition with typos. Excerpt from book: CHAPTER III THE GEOLOGICAL CLASSIFICATION OF SOILS Weathering must be considered as affecting soils both in situ and in motion. This gives two general clas... more »ses of materials — those that have not been shifted far from their place of origin, and those in the formation of which the transporting agencies have been instrumental. These two general groups, designated as sedentary and transported,1 are subject to considerable subdivision, as follows: — f Residual Cumulose Gravity — Colluvial [ Alluvial Water j Marine [ Lacustrine Ice — Glacial Wind — Transported 25. Residual soils. — This group of soils covers wide areas of our arable regions and comes from many kinds of rocks. Residual soils are old soils, the oldest with which we have to deal in agricultural operations. Since a 1 See Trowbridge, A. C. A Classification of Common Sediments. Jour, of Geol., Vol. 22, No. 4, pp. 420-436. 1911. residual soil is formed in situ, the rocks that underlie it, if sound, show the character and composition of the rocks from which the soil was actually a product. In such soils the changes that a rock undergoes in forming a residual clay are to be studied to the best advantage. An examination of the various grades of material that are found overlying the country rock (Fig. 3) in an area where Fig. 3.- - The gradual transition of country rock into residual soil by weathering in situ. this residual mantle exists, reveals more or less accurately the gradations from rock to soil. Residual soils, besides being old soils, are usually nonstratified and present a heterogeneous mass of material. Since they have been subjected to leaching over vast periods, a very large amount of the soluble materials have been washed out, tending to leave high percentages of the per...« less