GEOLOGY OF CENTRAL AVISCONSIN, 



CHAPTEE I. 

 SUKFACE FEATURES OF CENTRAL WISCONSIN". 



The region here designated as Central Wisconsin includes Colum- 

 bia, Marquette, Waushara, Adams, Juneau, Wood, Marathon, Clark 

 and Jackson counties; all of Dane and Sauk counties except the west- 

 ern tier of towns in each; and also that portion of Green Lake county 

 which lies north of the Fox river. The Atlas plates of Areas D, E, F, 

 and H, apply in part or wholly to this region. 



RIVER SYSTEMS AND GENERAL SURFACE SLOPES. 



Disregarding the small areas in Clark and Jackson counties which 

 drain into the Chippewa and Trempealeau rivers, the region may be 

 said to include portions of four distinct drainage systems: those of 

 the Wisconsin, Black and Rock rivers, which flow southward and 

 westward to the Mississippi, and that of the Fox river, which flows 

 northward and eastward to Lake Michigan, and is thus tributary to 

 the Saint Lawrence. 



The directions and areas of these river systems are more or less 

 directly influenced by the rock structure of the state. Extending into 

 Wisconsin from the Upper Peninsula of Michigan, and forming the 

 central nucleus of the northern half of Wisconsin, is a great mass of 

 ancient crystalline rocks, which is bordered on all sides by newer and 

 undisturbed formations, whose outcropping edges, on the south, east, 

 and west, succeed one another in concentric bands. The central crys- 

 talline mass, probably for the most part never covered by later forma- 

 tions, includes the highest land in the state. It has a general slope 

 to the southward, reaching its greatest elevation 1,000 feet above 



