76 UlyRICH: MAJOR CAUSES OF OSCILLATIONS 



And SO it was left to the work of the past summer to clear 

 away all doubt, if possible. And it was cleared away. Other 

 outliers in this vicinity were visited until finally we found two 

 that were capped by Mazomanie and St. Lawrence and beneath 

 the Mazomanie showed from 50 to 100 feet of profusely fossili- 

 ferous Franconia. Incidentally the presence of the fault just 

 mentioned was unquestionably established. As an interesting 

 and welcome confirmation of the earlier conviction that the 

 Franconia is older than the Mazomanie — welcome despite the 

 fact that it came to light after the case had been proved by 

 actual superposition — I may add that two entirely new faunas, 

 one from near the top, the other just above the base of the forma- 

 tion, were discovered in the Mazomanie. The upper of the two 

 occurs rather widely distributed but in a sandstone so friable 

 that it can not be picked up without crumbling in one's hand. 

 Despite this difficulty a considerable collection was made and 

 safely transported to Washington by soaking the sand with 

 shellac. 



I have described the solution of this problem in greater detail 

 than may seem necessary, first because of its intrinsic value and 

 interest as a new instance of oppositely overlapping formations, 

 second because of its bearing on the question of differential 

 surface movements, and third as an illustration of the thorough- 

 ness of modern stratigraphic investigations. 



The case shows differential movement, first in the fact that the 

 Franconia is confined to the western half of the State, whereas 

 the preceding Dresbach was laid down on the east side and 

 over the south side as well as the west. Next, the very differ- 

 ent distribution of the Mazomanie shows reversal of the tilt from 

 the west toward the east. Further — through the fact that the 

 two formations are separated to the south of the Baraboo rknge 

 by a broad strip, in which neither is present, whereas to the 

 north of the pre-Cambrian range both formations were laid 

 down so that the younger overlaps the older for a distance of at 

 least 50 miles — it is proved that the movement was not simply 

 an east-west reversal of tilt but that it was accompanied by ad- 

 ditional local subsidence on the north where a depression was 



