The ''x\merican Bottoms'" Region of Eastern 

 Greene County, Indiana — A Type Unit in 

 Southern Indiana Physiography 



Clyde A. Malott, Ph.D., Assistant Professor of Geology, Indiana 



University 



INTRODUCTION 



There are few regions with more diversified physiographic 

 conditions and resulting wealth of topographic detail than 

 southern Indiana. The fairly uniform monoclinal dip of the 

 rock strata to the west-southwest brings to the surface a 

 highly variable succession of strata, each lithologic type 

 having its characteristic topographic forms. Since several 

 erosion cycles have been initiated, only the oldest of which 

 ever neared completion, the physiographic and topographic 

 features have been multiplied and rendered complex. An- 

 other highly important influence has been that of partial 

 glaciation. The Illinois glacial lobes came in from the north 

 on the two sides of the state, reaching as far south as the 

 Ohio River, but coming together or overlapping in the middle 

 of the state only as far south as northern Monroe County, 

 thus leaving a triangular area, with apex to the north, some 

 5,000 square miles in extent. The effects of the glacial ice 

 over the area covered by it largely determine the topographic 

 features. In the region adjacent to the glacial margin are 

 found some rather peculiar and striking drainage modifica- 

 tions and resulting topographic features. Since the drainage 

 of southern Indiana, especially its middle and western part, 

 is almost exclusively toward the west and south, these drain- 

 age modifications are to be found chiefly on the western side 

 of the unglaciated area. 



While there is, therefore, a great variety of topographic 

 forms resulting from the physiographic conditions mentioned 

 above, the complexity is not so extreme as may appear to the 



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