ulrich: major causes of oscillations 75 



But, so far as positive evidence regarding the age relations of 

 the Franconia and the Mazomanie is concerned, these investiga- 

 tions of the bluffs along Wisconsin River left the question as 

 unsolved as before. Nor did we come any nearer to its satis- 

 factory solution in the course of the following season's work 

 when a series of sections was made on the south side and around 

 the eastern end of the Baraboo range. But just before the 

 close of the field studies in 191 8 some very promising but under 

 the circumstances inconclusive observations were made in sec- 

 tioning the outliers and bluffs which dot the sandy plain of cen- 

 tral Wisconsin. Namely, at one of these bluffs I found a per- 

 fectly characteristic Mazomanie cliff and beneath it a 2 -foot 



NORT H 



OF 



B AR A BOO 



RANGE 



WtST 



Mississippi River 



SHAKOPE-E_ 



f ilot Knob 



Berl::. 



ONEOTA DOU 



VAOISOM S& 



ONTOTA 



MADISON^ 



ikssss?;.;; 



Fig. 4. — Section across central Wisconsin, showing greater eastward exten*^ 

 of the Franconia in this part of the State and intercalation of the Mazomanie be- 

 tween the top of the Franconia and the base of the St. Lawrence. 



exposure of reddish sandstone that seemed to me to be of Fran- 

 conia age. 



However, the evidence at this place was not satisfactory to 

 Doctor W. O. Hotchkiss, State Geologist, and Mr. F. Thwaites, 

 who accompanied me on this as on most of the other trips through 

 the State. Their doubts arose mainly from the fact that my 

 interpretation required the assumption of a fault hitherto un- 

 suspected between this bluff and Pilot Knob, which lies less 

 than a mile to the northwest. 



