Malott: The " America'ri Bottoms'' Region 23 



One must conclude that the Cincinnati-Ridgeport ridge and 

 its branch between the ^'American Bottoms" and Clifty Creek, 

 and also the end of the ridge between Clifty and Plummers 

 creeks, as seen north of Koleen, represent the level of a 

 former peneplain, which may be seen on the upland divides 

 over the whole unglaciated portion of the state, reaching up 

 occasionally to maximum elevation of 1,000 feet or more. 

 There are places in the state where it is broad and plateau- 

 like as compared with local peneplains or structural levels 

 below, or the entrenched drainage channels. Some of these 

 characteristics may be seen on the topographic map of the 

 ''American Bottoms" region. To this high former peneplain 

 of southern Indiana, Beede has given the name Kirksville 

 plain from its excellent development near the little village of 

 Kirksville in Monroe County.' It has been regarded as a 

 correlative of the Lexington peneplain of Kentucky and the 

 Highland Rim of Tennessee, and was probably developed in 

 middle Tertiary times. 



The Kirksville peneplain is the oldest peneplain repre- 

 sented in southern Indiana, and, so far as the physiography 

 can be read from the topographic forms, must be used as a 

 beginning of represented physiographic history ; yet there 

 is no doubt but that other peneplanations succeeded the with- 

 drawal of the Pennsylvanian seas and preceded the develop- 

 ment of the Kirksville. There is no physiographic record of 

 the great lapse of time represented by the remainder of the 

 Paleozoic, the entire Mesozoic, and the earlier part of the 

 Cenozoic. 



The Partial Erosion Cycle Succeeding the Kirksville Pene- 

 planation. Succeeding the Kirksville peneplanation, the re- 

 sidual forms of which are found in the gently undulating, 

 often broad, inter-stream spaces of the ''American Bottoms" 

 region, was an uplift which initiated an ensuing cycle of 

 erosion. Whether the amount of this uplift is to be measured 

 by 'the difference between the Kirksville level and the grade 

 level of the present streams, or by more or less than this 

 amount, we should be able to read from the resulting as- 

 semblage of topographic features. Close study of the region 

 fails to reveal a consistent series of benches that may be 



•' J. W. Beede, Features of Subterianean Drainage in the Bloomington Quadrangle. 

 Procecdififjs of the Indiana Academy of Science. 1910. 



