PALEOZOIC ROCKS FOUND IN DEEP WELLS 



549 



Wisconsin and northeastern Illinois (Table V). In northern Illinois 

 it was formerly correlated with the Madison and Mendota of 



TABLE V 



Partial Log of City Well No. 4, Kaukauna, Wisconsin 



Wisconsin, but bears no resemblance to those formations.^ The 

 thickness averages close to 100 feet with a maximum of 165 feet. 



FRANCONIA FORMATION 



Distribution. — The Franconia sandstone caps a wide cuesta in 

 western Wisconsin which extends southeast from St. Croix Falls to 

 near Baraboo. It also forms a bench along the valley sides within 

 the Lower Magnesian cuesta. The surface of the formation is 

 divided into several minor terraces each corresponding to some 

 difference in relative resistance to weathering. 



Character. — The Franconia sandstone is fine grained, gray to 

 green in color, and for the most part somewhat calcareous. How- 

 ever, the lithologic character of the formation varies considerably 

 in different parts of the state, and there are rapid changes in the 

 character of the formation. For instance the yellowish sandstone 

 of the Sparta district is represented near Viroqua at the same 

 stratigraphic level by dark green clay shale. The greater part of 

 the Franconia is highly glauconitic, especially near the bottom and 



^ C. B. Anderson, "The Artesian Waters of Northeastern Illinois," Illinois State 

 Geol. Siirvey Bull. 34 (1919), pp. 84, 107. 



