PENNSYLVANIAN. 441 



4. The upper portion of the section, extending down for about 370 feet, contains for the 

 first 200 feet some mingling of "Coal Measures' ' plants with species found in the "Upper Lykens 

 division" of the Pottsville, and was therefore provisionally termed by the writer '"^^ the "Upper 

 Intermediate division." This division, which includes Lykens coal No. 1, belongs to the upper 

 PottsviUe or Beaver River formation." It will be recalled that this is the only part of the Potts- 

 vUle found throughout the bituminous coal regions of K 17 and K 18, aU of which falls within 

 the region of later Pottsville overlap. In the Virginian region this upper PottsviUe expands 

 tremendously to the southeast, probably exceeding 1,500 feet in thickness and including the 

 greater part, if not all, of the Kanawha formation in West Virginia. The paleobotanic data 

 seem to indicate the PottsvOle-Allegheny line of the bituminous fields at a coaly streak about 

 100 feet below the conventional top of the Pottsville in the type section, the paleobotanic 

 boundary being inclosed in the upper part of the great plexus of conglomerates. In the more 

 northern anthracite areas the upper conglomerate has waned and the boundary as drawn on 

 the sheets of the Geologic Atlas generally falls on or near a coal which, so far as determined 

 paleontologicaUy, belongs to the BrookvUle-Clarion coal group. 



From a thickness of over 1,400 feet in the Pottsville region of the southern anthracite 

 field, the Pottsville, in passing to the north, thins to about 850 feet in the Mahanoy region, in 

 the western middle field, about 400 feet in the Silver Creek basin, only a few miles to the north, 

 in the eastern middle field; 300 feet in the vicinity of Hazleton, in the same field; and from 

 about 250 to 163 feet, averaging about 225 feet, in the northern anthracite field. '^^'''^'^^ In the 

 western part of the western middle field the lower PottsviUe * is partly represented, though 

 the remaining coals have thinned. It is not recognized and is probably not present in the 

 eastern middle field, where the upper part of the middle PottsviUe is thought to have a thin 

 representative. Only the upper PottsviUe ("Upper Intermediate division") appears to be 

 present, incomplete in some sections, in the northern anthracite field, where the lowest fossUifer- 

 ous stratum, at points just above the Mississippian, is not older than the Sharon shale mem- 

 ber of the bituminous districts. PottsvUle coals, such as the Dunmore coal group (Mercer 

 age in part), are few in the northern area though workable at a number of points (Boston mine, 

 near Pittston, etc.), where, they are included in a lower "red-ash group." Only the upper 

 PottsviUe is present in the smaU residual areas in Wyoming and SuUivan counties. At Bernice 

 it presents not over 125 feet, missing the lower portion of the Beaver River formation; at 

 Mehoopany, the lowest bed, a conglomerate on the red shale, is perhaps not older than the lower 

 sandstone of the Connoquenessing member. In other words, the basal portion of the Beaver 

 River formation ("Upper Intermediate division" of the PottsvUle type section) appears not 

 to have been deposited in portions of the overlap area north of the anthracite fields, nor locally 

 along the Allegheny Front or in certain other parts of the bituminous regions of K 17 and K 18. 

 The subsidence and overlap of sediments is thus seen to have been most rapid and strongly 

 marked in the anthracite regions. 



The axis of the lower Pottsville estuary doubtless extended southwestward across the 

 eroded region to the south of the Broad Top field, which contains no Pennsylvanian older than 

 the Beaver River formation or upper PottsvUle. The early series is not seen again until, follow- 

 ing the eastern edge of the coal field, we begin, in the Cheat Mountain region of central West 

 Virginia, to pick up lower beds, as the present border of the Pennsylvanian gradually passes 

 diagonally downward into the deeper portions of the smaller basin of the early deposition. 

 Not till we reach the Pocahontas district do we meet beds as old as the lowest of the lower 

 PottsviUe in the type section of the southern anthracite field. The PottsviUe expansions have 

 been described and illustrated elsewhere by the writer.^''^'' 



The "Coal Measures" or post-Pottsville in the Pennsylvanian anthracite region. — The vari- 

 ability of intervals and the consequent difficulties of correlation of the individual members 



« See remarks on application of the name, pp. 433-434. 



6 I. C. White '"" has applied the name Pocahontas group to the lower part of the lower Pottsville. 



