424 W. 11. TWENIIOKEL THE SILVEE CITY QTAKTZITES 



brecciated, dark green, very earthy chert, which has a thickness of about 

 5 feet. The bed could not be traced from B to C, as the interval is 

 covered; but the character of the rock, except for the brecciation, is the 

 same, and there seems little doubt but that the correlation is correct. A 

 thin-section made from the l:»reccia at C showed exactly the same mineral 

 constituents as the rock in the place where brecciation had not occurred. 

 The cherty fragments show no wear whatever and are generally, but not 

 everywhere, well cemented together, the cement being of a lighter shade 

 of green, but still dark. Many of the fragments have their peripheral 

 portions nearly white, or at least of a lighter shade than are the centers, 

 and in the cases of many of the smaller pieces the change of color extends 

 to the center. At D typical latan limestone occurs, while at E the degree 

 of brecciation is greater than was seen elsewhere, although, as in the 

 previous instance, it is not certain that the breccia is the equivalent of 

 the limestone, although it holds what appears to be the position belonging 

 to the latter, and in it was found a marine fossil which could not have 

 come from either of the shale divisions, since they are without marine 

 fossils in this region. Mineralogically, the breccia at E is somewhat dif- 

 ferent from what it is at C, as is shown by the notes which Professor 

 Winchell kindly made for the writer. At G typical latan limestone is 

 exposed, and traced northwesterly it shows no change. At F the altera- 

 tion appears to be merely, initial, while east of E there are no exposures 

 in which any evidence of alteration is visible. In none of the exposures 

 of this division w^as there observed any parallel arrangement of minerals 

 or rock fragments. 



The Le Koy shales underlying Silver City ridge are finely laminated, 

 well cemented, fine-grained quartzites of a gray to greenish coloj*; There 

 are no yellows or reds, nor is there any orientation of constituents which 

 is referable to dynamic processes. In the deepest shaft which was dug- 

 Professor Mudge states^ that the sandstones "assumed the form of bluish 

 green cherts^' which "is traversed by veins of white quartz.^' Play consid- 

 ered this chert to be a "true igneous rock,"^ a view not supported by 

 Mudge. The shafts are now largely filled up, but much of the debris 

 which was thrown from them remains scattered over the ridge, and this 

 debris contains no igneous rocks. 



Near the top of the south side of the ridge are several very excellent 

 cold-water springs. Since they occur on that side of the ridge from which 

 the strata are inclined, it is rather difficult to explain their presence except 

 on the assumption that the water rises along fractures. 



Mudge: Trans. Kansas Ac-ad. Sci., vol. vii. ISSl, p. 12. 

 Robert Hay : Ibidem, vol. viii, 1882, p. 17. 



