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Indiana University Studies 



casual observer. The types of rock exposed to the physio- 

 graphic processes give rather distinct regional physiographic 

 strips in succession from east to west. In a region like south- 

 ern Indiana, which has been subjected to minor uplifts from 

 time to time with short periods of stability between, the kind 

 of rock is the controlling conditioning factor. It is easy to 

 see in crossing the unglaciated area of southern Indiana from 

 east to west that both the major and minor features are 

 largely due to the kind of rock present. It follows, therefore, 

 that any discussion of the physiography must take fully into 

 consideration the areal geology, in so far as the latter is re- 

 lated to the lithologic type. While the type of rock of the 

 various physiographic belts has been a controlling condition, 

 there are also a number of forms, such as high, level-topped 

 dividing ridges, local peneplains, and similarly developed 

 stream trenches, common to all parts of the unglaciated area. 

 With proper care these may be traced thru the various physio- 

 graphic belts, and correlated. Since the major lines of drain- 

 age either rise in the glaciated area to the east, or in the 

 unglaciated area, and pass thru it into the glaciated area to 

 the west or into a stream itself affected by glaciation, there are 

 as a consequence certain other sets of conditions and results 

 tending to give continuity to the physiographic types. 



Thus, it will be seen that the physiography of southern 

 Indiana may have had its features determined by any one or 

 any combination of four sets of conditions : first, the type of 

 rock exposed; second, the several uplifts with intervening 

 short periods of stability; third, glaciation on two sides of a 

 triangular unglaciated area; and fourth, the fact that the 

 main elements of the drainage flow toward the west or south 

 from the glaciated region on the east, across the unglaciated 

 area and into the glaciated area to the west, or into a stream 

 that has been affected by glaciation. The physiography of 

 southern Indiana may be expressed in terms of one or more 

 of these four sets of conditioning factors. 



The locality known as ''American Bottoms" in eastern 

 Greene County, Indiana, illustrates all four of the above con- 

 ditioning factors, and may, therefore, be considered as a unit 

 or type of southern Indiana physiography. With these intro- 

 ductory remarks we are now ready to pass to a consideration 

 of the details of the region in question. 



