EROSIONAL HISTORY OF DRIFTLESS AREA 85 



Portions of the Lancaster Plain are known in the north- 

 ern part of the Sparta quadrangle at an average altitude 

 of 1100 feet; in the Baraboo district at 1200 feet: in the 

 northern and central portions of the Richland Center quad- 

 rangle on divides sloping southward from 1200 to 1100 feet; 

 in the central and southern portions of the Lancaster and 

 Mineral Point quadrangles at levels varying from 1100 to 

 1000 feet ; in the northern and central portions of the Gale- 

 na and Elizabeth quadrangles, Illinois, sloping southward 

 from 1000 feet to 900 feet ; in southeastern Minnesota at al- 

 titudes of about 1200 feet; and in northeastern Iowa from 

 the Minnesota line at an altitude of 1100 feet to Dubuque, 

 where it lies at and around 900 feet altitude. The best 

 general view of the surface may be obtained from the 

 Mississippi river between Bellevue, Iowa, and La Crosse. 

 Along this whole extent of river the immediate rim of the 

 Mississippi valley appears to be almost a horizontal line ex- 

 cept where broken by tributary valleys. Nowhere does the 

 Dodgeville plain come to the edge of the bluff, although, 

 near Turkey river and Prairie du Chien, remnants of the 

 higher plain are close enough to be visible from the river 

 and appear as monadnocks standing above the plain which 

 forms the rim of the valley. 



On the whole, the Lancaster plain is represented by up- 

 land surfaces which are more numerous, larger, closer to- 

 gether, and more nearly continuous than the summit areas 

 which constitute the remnants of the Dodgeville plain. In 

 the Sparta quadrangle, the Lancaster plain is represented 

 by a series of narrow divides above which stand con- 

 spicuous remnants of the Dodgeville plain such as Castle 

 Rock and Balls Bluff. In the Baraboo district por- 

 tions of the lower plain include the general fiat crest of 

 the North quartzite range at Ableman and at the Lower 

 Narrows, broad, poorly drained divides between north flow- 

 ing and south flowing, streams on the south range, and fiat 

 benches on the south range, such as the one at 1200 feet 2 

 miles northeast of Denzer. Just north of the Wisconsin 

 river the plain is best shown on the crests of north-south 

 divides, such as the divides between Pine, Bear, Narrows, 



