268 



GEOLOGY. 



dynamic action involved has had a metamorphosing effect on the rocks. 

 Thus in the mountains of the eastern part of the United States the 



Fig. 113. — Section showing the relation of the Cambrian in the Appalachian moun- 

 tains. The strata are both folded and faulted. €. Cambrian; 0, Ordovician: 

 S, Silurian. Length of section, 13 miles. (Hayes, Cleveland, Tenn. folio, U. S. 

 Geol. Surv. Ordovician and Silurian not separated in original.) 



Fig. 114. — Section showing the relations of the Cambrian at another point in the 

 Appalachian region where the faulting has been extreme. Al, Proterozoic; €, 

 Cambrian; O, Ordovician; S, Silurian. Length of section, about 8£ miles. 

 (Keith, Harper's Ferry, Va.-Md.-W. Va. folio, U. S. Geol. Surv. Ordovician and 

 Silurian combined in original.) 



original sandstones have been converted into quartz schists, the shales 

 into slates and schists, and the limestones into marble where the dynamic 



Fig. 115. — Section showing the relations of the Cambrian at a point in Massachusetts 

 where the rocks are much metamorphosed. A, Proterozoic; €, Cambrian; O, 

 Ordovician; C, Carboniferous; T, Triassic; am, amphibolite. Length of sec- 

 tion, about Hi miles. (Emerson, Holyoke, Mass. folio, U. S. Geol. Surv.) 



movements were profound, and less altered where the folding was 

 simple. Fig. 102 shows the general position of the Cambrian strata 



Fig. 115a. — Section showing the relations of Cambrian and other formations at a 

 point in Colorado a little north of Leadville. Aiyn, Arcnean; £7s, Cambrian 

 (Sa watch quartzite); Cmr, Carboniferous (Maroon formation); Jw, Jurassic 

 (Wyoming formation); Ip and qp, igneous rocks. (Emmons, U. S. Geol. Surv.) 



(€) over much of the interior. Fig. Ill shows their position and 

 relations in the vicinity of Tintic, Utah; Fig. 112, at a point in Montana; 



