PENNSYLVANIAN. 443 



ConemaugJi formation. — The Conemaugh formation has naturally a much larger area than 

 the Monongahela and extends closer to the anticlines near the West Virginia and Maryland line. 

 From a thickness of 700 to 800 feet in southwestern Pennsylvania it thins to the northern and 

 western outcrops (about 300 feet in Ohio), but on the east, in one of the sections of western 

 Maryland, it exceeds 625 feet. In the Piedmont folio ^^^ the equivalent of that part of the 

 Conemaugh above the Bakerstown coal is mapped as the FairfarX formation and the equivalent 

 of the lower Conemaugh is included in the Bayard formation. Toward the southwest the 

 Conemaugh thins again, so that the formation is limited to a very narrow strip, hardly more 

 than a county in width, on entering Kentucky, where it measures about 550 feet, and, though 

 its distribution is not fully worked out, it probably does not extend southwest of Morgan County, 

 Ky. The fossil floras of the formations show that neither the Monongahela nor the Conemaugh 

 is now represented in all that portion of the Appalachian trough lying to the south of this 

 district. Like the Monongahela, the Conemaugh is notable for the diminution of the calcareous 

 matter toward the south; the red sediments increase in passing diagonaUy downward through 

 the formation, which also becomes more conglomeratic toward its eastern outcrop. 



MlegTieny formation. — The lower limit of the Conemaugh along its southern outcrop has 

 recently been so radically changed as the result of a revolution in the classification of the older 

 Pennsylvanian in the southern region that only in the latest contributions by Stevenson '""^ and 

 I. C. White"*" is it even approximately located. 



The Allegheny formation, which in K 17 and K 18 approaches so near the margin of the 

 Pennsylvanian as to be nearly everywhere indistinguishable on smaU-scale maps, except in the 

 southern and western middle anthracite fields, keeps the same relative position along the western 

 outcrop for some distance beyond Ohio River; but on the east side it retreats westward as the 

 thicker and successively lower Pottsville strata are developed along the Pennsylvanian outcrop ; 

 so that at the Kentucky line its connected areas are confined to a short belt lying in the western 

 half of the field, though isolated patches cap the high ridges and tallest mountain tops far to 

 the east. 



The formation measures 260 to 350 feet in western Maryland,^'^ where that portion below the 

 Middle Eattanning coal is described by Darton and Taff^^' as the Savage formation, the upper 

 part being included in the Bayard formation. Deep-well records show it to be much thinner 

 beneath the Monongahela area, though it approaches 300 feet in thickness at some places on 

 its western outcrop in Ohio. Toward tlie south, however, it thins remarkably, so that in the 

 Kenova quadrangle, in northeastern Kentucky, it falls under 170 feet, though several of its 

 limestones are there present. Remarkably enough, in consonance with the downward diagonal 

 trend of the red material noted in the overlying formations, we find records "^^^ ""<* of red shales 

 in the upper part of the Allegheny at several points on the southeastern and southwestern 

 borders of the basin. This feature is, however, attributed by I. C. White""" to weathering. 



Formerly it was supposed that the Allegheny formation was very much thickened to the 

 southeast and included what had been described '" as the Kanawha formation, which aittains a 

 thickness of over 1,200 feet in southern West Virginia. A later review of the stratigraphy by 

 Stevenson '"^^ '""'' more than confirmed the very conservative changes first proposed by the 

 writer^"" after the study of the fossil plants. Subsequent conclusions reached as the paleo- 

 botanic studies progressed have been met by the results of the stratigraphic work of the State 

 Survey, so that the classification given by I. C. Wliite in a recent report of the West Virginia 

 Geological Survey is in nearly all important points in agreement with the preliminary correla- 

 tions drawn by the present writer. The Stockton coal, the topmost coal of the Kanawha 

 formation, which was previously ""''* placed in the Upper Freeport position and regarded as the 

 topmost bed of the Allegheny, is now put at a horizon beneath that of the Homewood sand- 

 stone member, being regarded as representing an Upper Mercer horizon. Similarly the "Roar- 

 ing Creek" sandstone member, so well developed in the Tygart 'S'alley and in the Buckhannon 

 quadrangle, though formerly regarded as "Upper Freeport," is now placed by Stevenson and 

 I. C. White at the level of the Homewood sandstone, the top member of the Pottsville, a corre- 



