THE PRE-POTSDAM PENEPLAIN 3 I 3 



The larger stream valleys about Wausau have been carved in the peneplain 

 to a depth of about 200 feet. 



Fig. 2. — Profile extending approximately east and west through Grand 

 Rapids and Pittsville forty miles south of Wausau at the border of the pre- 

 Cambrian and sandstone districts. Here the pre-Cambrian is covered with 

 remnants of the Potsdam sandstone, and the valley bottoms are broad and 

 shallow, and have no depth in the peneplain. 



Fig. 3. — Profile extending north and south through the pre-Cambrian and 

 Paleozoic areas, from Merrill and Wausau through Grand Rapids to Madi- 

 son. The elevation of the dissected peneplain at Merrill is 1,550 feet, of the 

 partly uncovered peneplain at Grand Rapids about 1,000 feet. The buried 

 peneplain has an elevation of 500 feet at Kilbourn and 70 feet at Madison. 

 The dissected peneplain, the slightly dissected peneplain, and the buried 

 peneplain have essentially a continuous and uniform slope downward to the 

 south. Rib hill and the Mosinee hills are monadnocks in the dissected pene- 

 plain, and the Necedah and Baraboo quartzite bluffs are monadnocks in the 

 buried peneplain. Mosquito mound, the Friendship mounds, and Elephant's 

 Back are mounds of Potsdam sandstone in the valley-bottom plain of the 

 sandstone district. 



