436 INDEX TO THE STEATIGEAPHY OF NORTH AMERICA. 



Survey,^*^^ and the identifications of the members have been critically reviewed and revised 

 by I. C. White ""^^ and J. J. Stevenson.''"* The variation in the sections and the introduction 

 of local coals are discussed by Ashley.^'" The correlations in the Broad Top field are fully 

 considered by Stevenson.'""' 



Conemaugh formation. — The Conemaugh as defined by Frankhn Piatt/" in the Conemaugh 

 River section of Pennsylvania, includes a series, generally less than 600 feet in thickness, lying 

 between the Allegheny or "Lower Productive Coal Measures" ("XIII"), and the Monongahela, 

 or "Upper Productive Coal Measures" ("XV"). On account of its relative deficiency in coals 

 and economic hmestones or iron ores it has been known as or included in the "Lower Barren 

 Measures " also called "Elk River series " '"'^'' and "No. XIV."'"* 



The numerous sections given in the Ohio and Pennsylvania reports, or cited by I. C. 

 White ""^^ and G. H. Ashley,'" show a lack of regularity far exceeding that of the members of 

 the Pottsville. Not only do the component terranes vary greatly in thickness but in many 

 places they are absent; yet several of the individual members are of great persistence. The 

 principal members of the Conemaugh formation which have been described from different 

 areas"*"'''" are, in descending order: 



1. Ufper Pittsburg limestone -member; just under Pittsburg coal; one to several thin, in places brecciated lime- 

 stones, containing minute univalve moUusks in a variable interval averaging about 25 feet; in Fayette County, Pa., 

 locally replaced by iron ores. 



2. Little Pittsburg coal; a, widespread coal-bearing zone, rather than a single coal, 20 to 60 feet below the top of 

 the formation; locally associated with two limestones, one ("Upper Pittsburg limestone") 3 to 5 feet thick, above, 

 and the other (Lower Pittsburg limestone member) 8 to 10 feet thick, below the coal horizon. 



3. Connellsville sandstone member; massive, conglomeratic, about 20 feet or more in thickness, largely confined to 

 the Connellsville region of Pennsylvania and the Potomac basin of Maryland and West Virginia. 



4. Little Clarksburg coal; 100 to 130 feet below the top "of the formation; confined to southern Pennsylvania and 

 northwestern West Virginia; directly underlain in latter region by the Clarksburg limestone member, which is impure, 

 with ostracods and fish, and attains a local thickness of 20 to 30 feet. 



5. Morgantown sandstone member; yellowish-gray mealy sandstone, 20 to 100 feet thick, locally conglomeratic or 

 brecciated; 200 feet below top of Conemaugh at Morgantown, W. Va.; generally persistent in Pennsylvania, Mary- 

 land, and West Virginia. 



6. Elk Lick coal; close under No. 5, widely persistent and usually present in Pennsylvania, Maryland, Ohio, and 

 northern West Virginia, and locally workable to the east; surmounts the Elk Lick limestone member, 12 feet thick, 

 in Somerset County, Pa. 



7. Ames (" Crinoidal") limestone member; very thin bed nearly midway in Conemaugh, generally 275 to 300 feet 

 below top in most of Pennsylvania, 200 feet below on the Ohio at Wellsburg, the interval decreasing westward to 140 

 feet, though swelling to 300 feet at the southern outcrop in Ohio,""^"^ dark-bluish or greenish-gray tough siliceous granular 

 limestone, usually 3 to 5 feet thick; present or represented by marine calcareous shell-bearing shales nearly everjrwhere 

 except in northeastern portion of the Plateau region; a series of red clays, sandstones, and marls, the "Washington 

 Reds,'' of variable thickness and color, lies above it; the limestone is rich in marine brachiopods and pelecypods; 

 "its common fossUs are Productus nebrascensis, P. prattenianus, P. longispinus, P. semireticulatu^, Hemipronites crassus, 

 Spirifera camerata, S. plano-convexa, Athyris subtilita, Lophophyllum proliferum, Zeacrinus m,ucrospinus, together with 

 undetermined plates and stems of crinoids." 



8. Harlem ("Friendsville" or "Crinoidal") coal; thin and less persistent, immediately under Ames limestone 

 member; present in most of outcrops in Ohio and western Pennsylvania, but rare near Allegheny Front. 



9. "Pittsburg Reds;" mainly soft or variegated shale and marly clays in thick variable series under No. 8; less in 

 evidence toward the northeastern and northwestern borders of the Conemaugh area; incloses a bluish fossiliferous 

 limestone (the-Ewing limestone of Ohio State reports) over much of the Ohio area. 



10. Saltsburg sandstone member; massive (20 to 60 feet); in places absent; probably same as Cow Run sand of 

 southeastern Ohio; underlain by thin shale and local dark or gray limestone. 



11. Bakerstown coal; "Tyson'' coal of Maryland, correlated by Stevenson with the Barton coal; fairly persistent 

 in southern Pennsylvania but rarely identified in Ohio; locally important in Maryland and West Virginia. 



12. Upper Cambridge ("Pine Creek") limestone member; typical in Noble County and southward in Ohio; thin 

 and local in southwestern Pennsylvania. 



13. Anderson coal; unimportant; fairly persistent through Ohio and northern West Virginia but disappearing a 

 short distance east of the Pennsylvania State line. 



14. Buffalo sandstone member; correlated with the Saltsburg by Stevenson; locally a conglomerate, 60 feet thick 

 on Kiskiminitas River; generally persistent, 30 to 50 feet thick, though thinner on northern and eastern sides of basin; 

 less important though locally coarse on west through Ohio. 



15. Lower Cambridge ("Brush Creek") limestone member; thin, black, fossiliferous, 30 to 60 feet below No. 13; 

 generally present in Pennsylvania but disappears to west and sovith in Ohio. 



