446 



PENNSYLVANIAN PERIOD 



The Carboniferous system of the west includes 

 all sorts of sedimentary rocks, among which are 

 considerable thicknesses of limestone. They are 

 exposed at many points (Fig. 383) and their exist- 

 ence over wide areas where they are now covered 



Fig. 388. Section showing the position and relations of 

 .the Carboniferous section near Estillville, Ky. C= Carboni- 

 ferous (including Mississippian); D = Devonian; 5 = Silurian. 

 Length of section about 16 miles. (Campbell, U. S. Geol. Surv.) 



by later deposits is certain. The system is, how- 

 ever, not continuous. Numerous islands of older 

 rock probably maintained themselves throughout 

 the period, and a large area of land existed through- 



Och 



O s 



S > 



J 



Oc/3 

 U-S 



ii 8 



j- ^H3 

 ^3 ^ r* 

 O f c! 



Fig. 389. Section in northwestern Massachusetts, showing 

 the position and relations of the Carboniferous system. Cw = 

 igneous rock, Carboniferous; Sc (Conway schist) and Sg 

 (Goshen schist) are Silurian formations; Oh (Hawley schist), 

 Os (Savoy schist), and Och (Chester amphibolite) are probably 

 Ordovician, though classed with the Silurian in the Hawley 

 folio. (Emerson, U. S. Geol. Surv.) 



out the Paleozoic era in western Nevada (west of 

 long. 117), and had an unknown extension north 

 and south. 



Figs. 390 to 392 show the positions and rela- 

 tions of the Mississippian and Pennsylvanian sys- 

 tems at various points in the west. The sections 

 are from regions where the strata have been much 

 disturbed by folding, faulting, and the intrusion 

 of igneous rock. 



North of the United States, Carboniferous 

 strata (largely Mississippian) outcrop on the west 

 side of the northward continuation of the Great 

 Plains. These strata are probably continuous 

 southward with the contemporaneous formations 

 of the United States. Strata of the same age are 

 found on both sides of the Gold Range of British 







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"I " ti 



U ^ o 



^g-3 



tl'C a 

 52-3 a 



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