PENEPLAINS OF DRIFTLESS AREA 



uppermost line, figure 11] from this 1400- I to the I 



of the mounds in the southern portion of the Elizabeth quad- 

 rangle in Illinois, remnants of this plain between the 

 extreme points come to about the level of this line. South of 

 Baraboo. the first great area of upland is an st si idge, 

 known as Military Ridge or locally known as Dodgeville Prairie 

 because it is a gently undulating plain and alin ~ 

 nattish surface averag 3 12 : in altitude, with occasional 



swells and knobs reaching higher levels. It is here underlain by 

 Galena dolomite. Farther south the plain is found on th- I 

 of numerous mounds and ridges at elevations of 1170. 1152. 1160 



■ in the northern part of the Elizabeth quadra: _ 1112. 



1115. 1065. 1 • L072 : in the central part, and - - 96±. 



27. 1004 and 1000 feet in the southern part of the quadrangle. 

 In the northern part of the Elizabeth quadrangle the plain is 

 on about I ~ Xiagaran dolomite whereas in the south- 



ern part it is on more than 100 feet of the same formation. 



The plain is seen to cut from Huronian quartzite at Baraboo 

 across the Prairie du Chien. St. Peter. Platteville. Deeorah. 

 Galena, and Maquoketa formations, to the Xiagaran formation 

 at the south border of the Driftless Area. It slop- - - 

 amount of six feet per mile in a direction 16 r wesl 



4 The surface of the upper plain does nor conform to i 

 dip of the strata. The strata dip S. 45 c W.j the surface 

 plain slopes S. 16 c W. The si I lip about fifteen feel 

 each mile ; the plain slopes only sis r each mile. 



The surface of the upper plain wherever found is ehar- 

 acteristically more dissected than the lower and younger plain. 

 This - - -ially noticeable near Dodgeville. Near Highland. 

 Wisconsin, the ei - - pronounced and the sharp draws - 

 to what extent the original plain has been dissected. 



It is not necessary to suppose that the plain is controlled 

 by layers of : sisl itherefoi - 



trary the features as found in the field are exactly what would 

 be expected of a partly dissected peneplain. TVherever ti. 

 resistant rocks, like the Maquokel - vnied the 



surface, they have been more eroded than the mor- - s 

 mations. whose surfaces are left to form the remnants 

 plain today. 

 9 



