58 



Indiana University Studies 



raised to this critical level had a porous barrier which did 

 not permit it to overflow, but rather encouraged it to filter 

 thru in sufficient quantity to take care of the inflow, thus 

 allowing time for the development of subterranean passage- 

 ways with favorable outlets, is another very special factor 

 entering into the problem. For, had this basin been able to 

 overflow^ at the low^er side, it is quite probable that the surface 

 drainage would have persisted, and the ''American Bottoms" 

 basin w^ould not have been preserved. Thus, the "American 

 Bottoms" basin is an unusual physiographic feature, because 

 of the exceptional set of conditions critically adjusted to one 

 another. Only by understanding these conditions can we 

 appreciate how and why the "American Bottoms" has been 

 preserved as a youthful area topographically, which must 

 remain for a long time almost exactly as it is today, standing 

 scores of feet above the neighboring valleys. 



The "American Bottoms" basin, while probably without 

 parallel, is not such a specific feature that it fails of being 

 a representative of a certain general class. It is a very strik- 

 ing and peculiar feature, but there are others of its type, 

 tho none have gone so far or are so specifically adjusted. 

 To a considerable degree it is a representative of all specially 

 filled valleys in front of the Illinois Glacial Lobe, and perhaps 

 has its closest relative in the "Flatwoods" region of south- 

 eastern Owen and western Monroe counties. It has been 

 shown that "Flatwoods" is also a filled valley, and that the 

 filling was not without certain adjustments, and further that 

 McCormicks Creek Canyon, now set aside as one of the state 

 parks because of its exceptional scenic beauty, was probably 

 begun by subterranean drainage, not altogether unlike that 

 of the present "American Bottoms."^"' 



SUMMARY 



This paper postulates that the physiography of southern 

 Indiana has resulted from four conditions or sets of condi- 

 tions which control the physiographic reactions and topo- 

 graphic forms. Probably the most important of these is the 

 geology. Because of the monoclinical dip to the west, a series 

 of litho'ogical units is presented to the surface, upon which 



C. A. Malott, The Flatwoods Reg-ion of Owen and Monroe Counties, Indiana. Pro- 

 rcedinfjs of the Indiana Academy of Science for 1914. 



