CHAPTER IX 



SUB-PROVINCES, CLASSES, TYPES AND SURVEYS 



IN working out the classification of soils in detail in a single 

 state, it may be necessary to make other divisions, or sub-provinces, 

 the soils of which have a common origin, but differ from those of 

 other sub-provinces in some fundamental characteristics. 



Sub-provinces. On this basis the glacial and loessial province 

 of Illinois has been divided into the following sub-provinces: 

 (1) Unglaciated, comprising three areas, the largest being in the 

 south end of the state; (2) Illinoisan Moraines, including the 

 moraines of the Illinoisan Glaciation; (3) Lower Illinoisan Glacia- 

 tion, covering the south third of the state; (4) Middle Illinoisan; 

 (5) Upper Illinoisan; (6) Pre-Iowan, but now believed to be part 

 of the Upper Illinoisan; (7) lowan Glaciation; (8) Deep Loess 

 Area, including a zone a few miles wide along the Wabash, Illinois 

 and Mississippi rivers; (9) Early Wisconsin Moraines; (10) Late 

 Wisconsin Moraines; (11) Early Wisconsin Glaciation; (12) Late 

 Wisconsin Glaciation; (13) Old River Bottom and Swamp Lands, 

 found in the older or Illinois Glaciation; (14) Sand, Late Swamp 

 and Bottom Lands, those of the Wisconsin and lowan Glaciation ; 

 (15) Gravel Terraces formed by overloaded streams draining from 

 the glaciers and gravel outwash plains; (16) Lacustrine Deposits, 

 formed by Lake Chicago or the enlarged Lake Michigan. 



Soil Classes. The soils of these sub-provinces are divided 

 into classes based primarily on texture. The classes are as follows: 



(1) Peats, (2) Peaty Loams, (3) Mucks, (4) Clays, (5) Clay 

 loams, (6) Silt loams, (7) Loams, (8) Fine sandy loams, (9) 

 Sandy loams, (10) Sands, (11) Gravelly loams, (12) Gravels, (13) 

 Stony loams. These are further divided into soil types. 



Soil Types. A soil type is the unit of soil classification. It 

 is a soil unit which throughout the area has the same physical, 

 chemical and biological characteristics. In the establishment of 

 soil types, the following factors are taken into account: (1) Origin, 

 whether residual, cumulose, colluvial, sedimental, glacial or eolial. 



(2) The topography or lay of the land. (3) The native vegetation, 

 as forest or prairie. (4) The strata or character of surface, sub- 

 surface or subsoil. (5) Physical composition or texture of the 



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