392 



GEOLOGY OF EASTERN WISCONSIN. 



"he creek, a half a mile east, near the lower face of the Hamilton 

 formation confirms this view. 



We find, however, on the north side of the Hamilton area, some of 

 the shaly rock under discussion in the drift, from which it is probable 

 that there is a concealed area on that side. This harmonizes witli the 

 view taken in this report, viz.: that this shaly rock belongs to the 

 Lower Helderberg formation, which is found in Michigan, and ab- 

 sent in Iowa, according to the geologists of those states, and hence, 

 must terminate in the interval, and it would seem that we have here 

 the point of its disappearance. It is certain, at least, that no " narrow 

 circular rim " of the shaly limestone surrounds the Hamilton. 



Fossils are very rare in this rock, and I am not aware that any have 

 previously been reported from it. A fair specimen of Meristella 

 nucleolata, an OrtMs, resembling a young 0. oblata, and an imper- 

 fect specimen of Meristella or Pentamerus were the only reward of 

 repeated and diligent search. 



About one mile above the village of Waubakee, in the town of 

 Fredonia, Ozaukee county, in the bed of the Milwaukee river, and the 

 vicinity, is a formation that deserves our consideration in this con- 

 nection. On the north side of the river is a quarry in which the fol- 

 lowing section is exposed: 



FIG. 48. 



1. Light gray, thin bedded, shaly dolomite, resembling 

 that above described as occurring at Mud creek, but 

 less porous. The surfaces of some of the layers are 

 covered with large numbers of a Leperditia, undistin- 

 guishable from Leperdilia alta 2 ft. 



2. A layer of hard dolomite, containing cavities, some 5 or 

 6 inches in diameter, which are usually filled with large 

 crystals of calcite. Leperditia occurs occasionally in 



this layer 10 in. 



3. Alternating thin and thicker beds similar to No. 1 in 

 lithological character, but some layers are marked with 

 a dark, rusty coating 2 ft. 2 in. 



4. Similar to No. 2 1 ft. 2^ in. 



5. Moderately thick beds somewhat shaly, intermediate in 

 character between the thinner and thicker beds above . . 1 ft. 



^- r - I Total. . 7 ft. 2% in. 



*T~---- "^ . 



