202 J. J. STEVENSON CARBONIFEROUS OF APPALACHIAN BASIN 



tabulate, as far as possible, the synonymy of such beds as are of strati- 

 graphical importance. 



In the preceding description, the plane between Upper and Lower 

 Pottsville was drawn on top of the Sharon sandstone. 



Crossing the Anthracite fields northwardly, one sees that the Potts- 

 ville column decreases rapidly, for the most part owing to successive 

 disappearance of the lower members, so that in much of the northern 

 field even the Sharon sandstone has but an insignificant representative. 

 The loss in the lower portion continues westwardly, so that in Wyoming 

 and Sullivan counties even the Sharon and some overlying beds have 

 disappeared. Only the upper members of the section are present along 

 the Allegheny front in Pennsylvania, but the whole of the Upper Potts- 

 ville, as well as the Sharon and some sub-Sharon beds, make their 

 appearance along this line in Maryland, as shown by the Potomac sec- 

 tions. Thence southward, along the eastern border of the basin, the 

 Lower Pottsville increases by successive additions of new members 

 below — sandstone, conglomerates, shales, and coal beds — as well as by 

 thickening of the upper beds, until on New river, of West Virginia, it is 

 the great New River series of Fontaine, which is 1,400 feet thick in Doc- 

 tor White's Nuttallburg section. Southwestwardly the increase con- 

 tinues until the maximum is reached in southwest Virginia and northern 

 Tennessee. Thence southward, along the general line of outcrop, in 

 Tennessee, into Alabama, the section . shortens through loss of some 

 lower members, as well as by thinning of the higher beds. Meanwhile, 

 in the same direction, the Upper Pottsville expands in a similar way — 

 by addition to the lower part of the section — while the upper members 

 for the most part expand less rapidly ; but as the Kanawha river is ap- 

 proached the expansion becomes notable throughout, and the great 

 thickness observed in central West Virginia is maintained into northern 

 Tennessee, where one reaches the last exposure of the Upper Pottsville. 



Along the northern border the Sharon sandstone and immediately 

 overlying beds reappear in the area studied by Mr Ashburner and 

 Doctor Chance, and thence along the northern border of Pennsylvania 

 one has the grouping offered by Doctor White : 



Homewood sandstone. 



Mercer group, shales, coals, and limestones. 



Connoquenessing sandstones, with Quakertown shales and coal. 



Sharon group, shales and coals. 



Sharon sandstone. 



This is the succession in Ohio along the northern and much of the 

 western border, though at the extreme northwest there is a great thick- 



