PENEPLAINS OF DRIFTLESS AREA 131 



angles of dip which are less than the dip of the underlying strata, 

 and they rise stratigraphically. For the relation of this plain to 

 the underlying formations and to the upper plain in Wisconsin 

 and Illinois, see figure 11. 



(3) In spite of minor folds and dips, the plain is uniform. 

 In the southern part of the Elizabeth quadrangle where the strata 

 dip southwestward at an exceptionally high angle, the general 

 level of the plain conforms to the level over the rest of the area, 

 even though it is here on soft Maquoketa shale. 



(4) Wherever found the lower plain is characteristically uni- 

 form and free from stream dissection except around the borders 

 of -its remnants. Especially is this noticeable when compared 

 with the dissected character of the upper plain. This is the to- 

 pography which a younger plain should have in contrast with 

 that of an older one. 



(5) The correlation made in the present paper departs from 

 that of Grant and Burchard who consider that there is in the 

 Lancaster-Mineral Point district an upper plain represented by 

 the tops of the numerous mounds and that all the lower flat are*as, 

 including the Dodgeville Prairie, the flat around Lancaster, and 

 the flat north of Cuba, belong to the lower or Lancaster plain. 

 That this is in error is shown by a study of the elevations of this 

 supposed plain. As shown by figure 12, the drop from Mt. Ida, 



Fir;. 12 — A profile from Mt. Ida on the Dodgeville Prairie south aero 

 portion of the Lancaster plain. Grant and Burchard assumed that 

 two upland surfaces shown here belonged U> the lower or Lancaster 

 plain. The profile makes it clear that two plains are represented. 



a distance of only eight miles, is one hundred feet, or more than 

 ten feet to the mile. Such a relation would be a severe strain on 

 the idea of peneplaination. In characteristic topography. ;is 

 well as in altitude, the Dodgeville Prairie belongs with the upper 

 rather than with the lower plain. 



