228 CLARK AND MARTIN — THE COAL MEASURES OF MARYLAND 



Inches 



" Over "-clay 9 



"Breast" coal 33 



Parting 01 



" Bearing-iu " coal 4 



Parting 0£ 



"Brick " coal # 10 



Parting 0£ 



"Bottom" coal ' 14 



The various elements composing the seam are constant and character- 

 istic in number and relative position. The relative thickness of these 

 individual elements varies from place to place. From the Pittsburg re- 

 gion toward the southeast there is a gradual increase in the thickness 

 of the " breast " coal, which reaches a maximum in the southern end of 

 the Georges Creek basin, where the entire vein has been found at a single 

 locality to reach 22 feet in thickness. There is greater change within the 

 limits of the Georges Creek basin than there is between the central part 

 of the Georges Creek basin and the Pittsburg region. This change con- 

 sists chiefly in an increase in the number and thickness of the shales at 

 the expense of the "breast" coal. This seam was called the Pomeroy 

 coal in the Ohio reports and the Elkgarden coal in the Piedmont folio 

 of the U. S. Geological Survey and in the Report on the Geology of 

 Allegany County. The name Pittsburg coal was applied to this seam 

 by J. P. Lesley in 1856. 



Redstone limestone (46). — A thin limestone is sometimes found a few 

 feet above the Pittsburg coal. In this region it is commonly separated 

 from it by argillaceous shales. It occurs in the position of the Redstone 

 limestone of Pennsylvania. 



Redstone coal (47). — At an interval of from 18 to 45 feet above the Pitts- 

 burg coal is a seam of coal which corresponds in position to the Redstone 

 coal of Pennsylvania. It is apparently very constant in the Georges 

 Creek basin, although it has not been prospected for, and has accord- 

 ingly not been opened at many points. The thickness is about 4 feet. 



Seivickley limestone (48). — A bed of limestone occurs about 10 feet above 

 the Redstone coal. It is in the stratigraphic position of the Sewickley 

 limestone of Pennsylvania. 



Loiver Seivickley coal (49). — At an interval of from 25 to 30 feet above 

 the Sewickley limestone, and from 40 to 45 feet above the Redstone coal, 

 is a thin seam of coal which has been recorded only from Borden shaft 

 and the Pumping shaft in the Georges Creek basin. This seam occurs 

 at the horizon of the Sewickley coal. As there is another seam above 

 this, however, which still falls within the limits of the Sewickley, and 



