194: Wisconsin Academy of Sciences, Arts, and Letters. 



ON SOME POINTS IN THE GEOLOGY OF THE KEGION 

 ABOUT BELOIT. 



By G. D. Swezey. 



Along the line of hills which forms the western boundary of 

 the Eock river bottoms at Beloit are exposed at frequent intervals 

 the outcropping edges of rock strata ; these include the upper 

 layers of the St. Peters sandstone, the whole or nearly the whole 

 thickness of the Trenton limestone, and the lower layers of the 

 Galena limestone. 



The Trenton limestone, which consequently most interests us 

 today, is a formation which presents so much variation in litho- 

 logical characters, and to some extent in fossils, that it is readily 

 divisible into a large number of distinct subdivisions, whose char- 

 acters are so well marked that they can in most cases be identi- 

 fied with ease, and sufficiently persistent, at least over the few 

 miles of extent with which we have to do, so that they can be 

 matched with a good degree of certainty ; there is scarcely an ex- 

 posure of any extent in the region of whose place in the Trenton 

 section we have any doubt. Moreover it happens that of the one 

 hundred and eleven feet of Trenton limestone, we have exposed 

 in one or more outcrops of the region, every layer unless it be a 

 few feet in the horizon of the Upper Blue. 



The subdivisions of our Trenton rock and their exposure in the 

 various quarries and outcrops of the region are shown upon the 

 chart ; the names of the quarries are given as they are familiarly 

 known by us at Beloit. Between the St. Peters sandstone and 

 the Trenton limestone are eight feet or perhaps more of transi- 

 tional layers ; they include at the bottom a foot or so of sand- 

 stone, more coarse and impure than is usual with the St. Peters, 

 above this five feet of impure lim.estone and shale, and at the top 

 two feet more of coarse sandstone. Above these transitional 

 layers we have twenty-two feet of Lower Buff limestone, sep- 

 arated by well marked shaly seams at least, if not by lithological 

 characters,_into three or four subdivisions, everywhere recognizable 



