EROSION AL HISTORY OF DRIFTLESS AREA 93 



ville plain projected from cuesta to cuesta, lies on the 

 average 200 feet higher than the Lancaster plain in the 

 inter-cuesta areas. (See Figs. 14 and 23). (5) Where 

 both plains are found together the change from one to the 

 other takes place either along lines parallel with or oblique 

 to the strike. (6) There are m^ny places along the main 

 south-flowing streams, for instance, along the Mississippi 



Fig. 24. A profile from Mt. Ida on the Dodgeville Prairie south across a portion of 

 the Lancaster plain. The iirofile makes it clear that two plains are represented. 

 (After U. B. Hughes). 



river, where upland surfaces representing the Lancaster 

 plain can be traced continuously from an inter-cuesta area 

 across a cuesta, on the summits of which the Dodgeville 

 plain is represented, to connect definitely with the Lancas- 

 ter plain in another inter-cuesta area (Fig. 25). There are 

 lines along which the Lancaster plain is unbroken by rem- 

 nants of the Dodgeville plain for the whole north-south ex- 

 tent of the Driftless Area. (7) If it be assumed that the 

 Lancaster plain in an area south of a Dodgeville cuesta is 

 merely the projection of the Dodgeville plain down the dip 

 of the strata, so that the two plains together form the 

 gentle southerly slopes of normal cuestas (Fig. 16), three 

 points located so as to include both plains, should show^ a 

 surficial slope parallel with stratigraphic dips. That this 

 assumption is not true is shown by the table on page 95, 

 in which both plains are represented in each computation. 

 Nowhere do the slopes of the surface and the dips of the 

 strata coincide. 



