ALLEGHENY FORMATION 22 L 



tion. This is in the stratigraphic position of the Brookville coal. It 

 has been known in Maryland as the Bluebaugh coal, and was so called 

 in the Report on the Geology of Allegany County. 



Clarion coal (12). — A seam of coal approximating 2 } feet in thickness 

 is found at an interval of from 12 to 30 feet above the Brookville coal, 

 or, in the absence of that coal, about the same distance above the base of 

 the formation. This seam corresponds in position to the Clarion coal. 

 It has been hitherto known in Maryland as the Parker coal, and was so 

 called in the Report on the Geology of Allegany County. 



Clarion sandstone (13). — Separated from the Clarion coal by a thin 

 series of shales, there is frequently a massive sandstone, which some- 

 times reaches as much as 70 feet in thickness. It is especially well de- 

 veloped along the Potomac river in Garrett county, where it can readily 

 be mistaken for the Homewood sandstone. This sandstone is in the 

 stratigraphic position and has the lithologic character of the Clarion 

 sandstone of Pennsylvania. 



Ferriferous limestone (14). — A short distance above the Clarion sand- 

 stone, or the horizon for it, is a limestone a few feet in thickness. This 

 limestone has been seen at only a few points in the southern part of 

 Garrett county. At all of these localities it is evidently of fresh-water 

 origin, and contains no fossils except Ostracoda. In the bore-hole four 

 miles northwest of Oakland a thin limestone with marine fossils was 

 encountered at this horizon. It is the position of the " Ferriferous " 

 limestone of Pennsylvania, and is probably the equivalent of the Putnam 

 Hill limestone of Zanesville, Ohio. 



Kittanning sandstone (15). — The interval between the Ferriferous lime- 

 stone and the next coal above is usually occupied by shale. In the 

 bore-hole four miles northwest of Oakland, where this interval is large, 

 it is occupied in par ( t, however, by sandstone. This sandstone corre- 

 sponds in position to the Kittanning sandstone of Pennsylvania. 



" Split-six" coal (16). — Separated from the Ferriferous limestone by a 

 variable thickness of shale is a seam of coal about 4 feet in thickness, 

 but too impure to mine. This is best developed in the southern end of 

 the Georges Creek valley, where it is known as the " Split-six." It does 

 not appear to have any named equivalent in other regions. 



Lower Kittanning coal (17). — A seam of coal of great persistence, which 

 can be seen at almost every point where strata of this horizon are ex- 

 posed, occurs at an interval of from 90 to 140 feet above the base and 

 from 170 to 210 feet below the top of the Allegheny formation. This 

 seam corresponds in stratigraphic position to the Lower Kittanning coal 

 of Pennsylvania. 



