624 



GEOLOGY 



areas of the system shown in Fig. 435 have probably been isolated 

 by erosion since their deposition. 



PRODUCTIVE COAL-FIELDS 



The Pennsylvanian system does not contain coal in workable 

 quantity everywhere, though coal is widely distributed as far west 

 as the 96th or 97th meridian in Oklahoma, and nearly to the 100th 

 meridian in Texas. The productive coal areas of the system in 

 the United States are five in number. These are as follows 1 : 



(1) The anthracite field, which is confined to eastern Penn- 

 sylvania, and contains an area of 484 square miles. It includes 



I 



Fig. 436. Map showing the areas of anthracite coal in Pennsylvania. 



IMfotxxe Mt 



Fig. 437. Section across Panther Creek basin in the anthracite region of 

 Pennsylvania, showing the position of the strata and the coal beds, 

 in black. (Stock, U. S. Geol. Surv.) 



several elongate, nearly parallel, synclinal basins, the longer .-i 

 of which have a northeast-southwest direction (Figs. 436 and 437). 

 From the adjacent anticlines, and from the neighboring shallower 

 synclines, the coal-bearing beds have been removed by erosion. 

 The strata of this field may once have been continuous with tl 

 of the next. 



1 Hayes, Stock, White, Campbell, Haseltine, Lane, Ashley, Bain, and TatT. 

 22d Ann. Rept., U. S. Geol. Surv., Pt. Ill, p. 15. 



