36J: 



GEOLOGY OF EASTERN WISCONSIN. 



the layer above having changed so as to be scarcely rlistinguish- 

 able from the compact rock below. Farther on, the ditt'erence 

 becomes still less, a few cavities, and a shghtly greater irregu- 

 larity in the subordinate layers, being all that distinguishea 

 them from the layers below, (h.) At the farthest point t.i 

 which these layers can be traced, no geologist would think of 

 separating them from the layers below, thus making it a clear 

 case of thinning out and transformation. These layers are es- 

 sentially horizontal. 



If we now return to the point in the southwestern part of the 

 quarry, whence we started, and take 69 paces to the southwest, 

 JJllHlll ' ■ i we find the rock exposed in the road as foUows: 



First, a compact Limestone, similar to that in the quarry, dip- 

 ping eastward at an angle of 6°. Tlie upper layer is 8 inches 

 . thick, underlaid by one of 4 inches, (d.) The rook for 5 paces 

 ^ is then covered, beyond which it again appears. The upper 22 

 ^ inches of this are divided irregularly into beds, the superior por- 

 5 tion of which is as compact as any seen at the quarry, but the 

 = lovrer is somewhat more porous. This dips 11° N. of E. Under 

 3 this lie 5 inches of porous rock, but not of the most pronounced 

 i class. Under this, again, lie 2 inches of similar kind; beneath 

 J which, again, there are 5}4 inches of hmestone, containing 

 ■ many cavities of the size of an almond, and similar to the upper 

 j layer described at the quarry. Under this lie 18^^ inches of the 

 j more pronounced and typical, porous, granular rook, (c.) Here 

 I again the section is interrupted by 8 paces of unexposed sm-faco, 

 [ when a porous, granular rock succeeds, having a dip of 14° N. 

 of E. (6.) There are about 26 inches of this, the irregularity of 

 the structure making it diflScult to measure exactly. Below thia 

 come 6 to 8 inches of a rough, irregular, brecciated, rather 

 hard and tough, but somewhat porous, rock, containing large 

 and small crinoid stems, like those common in the Racine beds. 

 The section is again interrupted for 4 paces, when a rougli, very 

 irregular, brecciated, porous rock foUows, constituting a confused 

 mass, similar to the rock mounds near Milwaukee and Wauwa- 

 tosa, yet to be described, (a.) In this, Illcenus ioxus, fragmcntd 

 of Atrypa and Ehynchonella, crinoid stems, and an Orthocems, 

 were found. This exposure continues 18 paces. The whole sit- 

 uation is imperfectly represented by the accorapanyuig figm-e. 

 It seems to be possible to draw but one rational conclusion 

 ; from the foregoing facts, viz: (1) That the last mentioned urog- 

 ular mass stood as a reef in the depositing sea; and (2) that tllo 

 alternating layers were deposited on its slope, while (3) these, 

 in the more quiet waters at a little distance from the reef, were 

 replaced by a deposit of finer silt, which formed the compact 

 layers. The unusual phenomena of cross and oblique lamina- 

 tion in limestone harmonizes with this view. 



Within a mile from this point, there are several exposm-es of 

 the compact rock. In the south half of Sec. 36, this even tex- 

 tured, coml)act variety is associated with a layer of the same 

 general color and composition, but having a sort of lumpy 

 Btructure, a kind of conglomerate, in which the pebbles and 



