THE PENNSYLVANIAN PERIOD 627 



minous and of good quality. The system here attains a thickness 

 of 13,000 feet, 



In the vicinity of Narragansett Bay, 1 the Carboniferous system 

 has great thickness, and often rests on beds of Cambrian age. Coal 

 occurs here, but it is too highly anthracitic (or graphitic) to burn 

 readily. The beds are much deformed and are associated with 

 igneous rocks. Carboniferous rocks of undetermined extent occur 

 at other points in New England, where they are partly igneous 

 (Fig. 441) or meta-igneous, and partly meta-sedimentary. They 



Fig. 440. Section showing the position and relations of the Carboniferous 

 section near Estillville, Ky. C = Carboniferous (including Mississip- 

 pian); D = Devonian; S = Silurian. Length of section about 16 

 miles. (Campbell, U. S. Geol. Surv.) 



Fig. 441. Section in southwestern Massachusetts, showing the position and 

 relations of the Carboniferous system. Cw = igneous rock, Carbonifer- 

 ous; Sc (Conway schist) and Sg (Goshen schist) are Silurian forma- 

 tions; Oh (Hawley schist), Os (Savoy schist), and Och (Chester Amphib- 

 olite) are probably Ordovician, though classed with the Silurian in 

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



are so completely metamorphic in some places as to make the 

 determination of their age and relations difficult and uncertain. 

 Beds of this age have recently been recognized in the Piedmont 

 of Alabama. 2 



Distribution west of the Great Plains. The Pennsylvanian 

 system is wide-spread west of the Great Plains, and probably under- 

 lies the Plains themselves. With rare exceptions, the western beds, 

 largely of limestone and sandstone, are coal-less. The coal-less 

 phase of the system, the whole earth considered, is far more wide- 

 spread than the coal-bearing. The abundant coal of the west be- 

 longs to later systems. 



1 Shaler, Woodworth, and Foerste. Geology of the Narragansett Basin 

 Mono. XXXIII, U. S. Geol. Surv. 



2 Smith, E. A., Underground Water Resources of Alabama, Geol. Surv. 

 of Ala., 1907. 



