366 



GEOLOGY OP EASTERN WISCONSIN. 





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point an east and west axis occurs, having the general trend of the ridge farther eMt, 

 and with which it probably has a definite connection. An east and west section in this 

 part of the quarry would show a dip to the westward, and a north and south section would 

 exhibit the layers curving gently over this axis. But as we 

 trace the rock eastward, it changes in nature. Near the east- 

 em extremity, the upper layer becomes slightly irregular in 

 bedding, and rather soft, and granular in texture. 



Below this is a layer from 22 to 24 inches thick, divided 

 into sublayers, somewhat irregularly, and occasionally show- 

 ing lines of deposition. To casual observation, it appears to 

 be a compact, fine-grained, even-textured dolomite, but 

 closer inspection shows it to contain many small cavities, 

 that are angular and sharply defined, and arc the result of 

 tlie removal of minute fossils, in which the rock abounds at 

 Ihis point. Aside from these, the rock is as previously de- 

 Kribed, with occasional seams of argUlaceous material. Be- 

 low this, the rock is siimlar to that in the western part of tho 

 quarry. In the extreme southeastern portion exposed in con- 

 nection with this quarry, the rock becomes quite irregular ui 

 structure. 



There ensues at this point, unfortunately, an interruption 

 of several rods in the exposure, so that this incipient change 

 in structure cannot be traced to its consummation . 



Passing this interval, we find at the western extremity of 

 Mr. >Schoonmaker's quarry, at the surface, a ceDular, even 

 textured, regularly bedded rock, similar 'to the last described, 

 but of lighter color, and more distinctly granular nature. 

 This dips southward at an angle of about 15°. As the face 

 of tlie quarry curves round to the south, the whole section is 

 composed of similar rock down t/) and beneath tlie water 

 that occupies tlie bottom of the quarry at this point. But 

 these lower layers dip less and less, until they become hori- 

 zontal, and even slightly incline toward the irregular mass. 

 If we trace these lower layers toward the ridge, their inclina- 

 tion somewhat increases as well as their thickness — this 

 latter sometimes markedly — until they are lost in the ob- 

 scure structure of the reef, or disappear at the surface. 



As we pass eastward along the fa^je of this ridge, now well 

 exposed by quarrying, the dip of the ill-defined layers in- 

 creases gradually to 54°, when the stratification can no longer 

 be clearly distinguished. This obscm-ity continues for 80 

 paces. There are some indications of horizontal bedding in 

 this space, and also some that the dip is to the south, and 

 that the exposure is along the strike of the strata, but neither 

 observation is altogether trustworthy. 



East of this, blue and lighter colored bands indicate a dip 

 of about 30° eastward. This continues for about ;!5 paces, 

 the observation at tho eastern extremity showing a dip of 

 31° in a direction E. 10° to 15° S., this being the dip as ex- 

 posed, not necessarily the full amount of the tnie dip. The 

 same qualification is true of the other observations made en 

 dip along the face of this exposm-e. 



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