438 INDEX TO THE STRATIGRAPHY OF NORTH AMERICA. 



description of the Dunkard group in Chapter XI (pp. 492-494), the beds of the Dunkard above 

 the Washington coal carry plants undoubtedly indicative of lower Permian age. I. C. White'"" 

 regards the earlier Monongahela, together with the upper half of the Conemaugh, as represent- 

 ing the closing stage of the Permo-Carboniferous, connecting the latter with the base of the 

 true Permian. No paleobotanic or invertebrate evidence justifying a reference of the Monon- 

 gahela to the Permian has yet been found. It is regarded by the writer **' *"■ "" as of Ste- 

 phanian age. The black shales of the Monongahela contain fish fragments, largely unstudied, 

 while the limestones present abundant Cyprian and Estherian types, generally regarded as of 

 fresh-water origin. 



In the vicinity of Carnegie, Pa., a local unconformity occurs at the base of the formation, 

 the topmost Conemaugh being eroded.^""' The formation, which is variable in character, con- 

 tains much limestone and coal. The section at the Lambert shaft in Fayette County, Pa., was 

 found by I. C. White ^"'"^ to contain 44 feet of carbonaceous shale and coals and 202 feet of 

 limestone, out of a total thickness of 388 feet for the entire series. There is relatively little red 

 material in areas K 17 and K 18, though the limestones turn to shale and sandstone with great 

 increase of red and green sediments in passing southward into J 17. The Monongahela reaches 

 its greatest thickness, over 400 feet, in central West Virginia, averages about 380 feet along 

 Monongahela River in southwestern Pennsylvania, is 240 to 270 feet in the Maryland district, 

 is incomplete in the Broad Top field, and thins to about 260 feet along the Ohio River boundary 

 and to about 140 feet at its farthest northwest occurrence in Jefferson County, Ohio. Its 

 composition in the type district is indicated by the following general section in Fayette and 

 Westmoreland counties, Pa., compiled by J. J. Stevenson."''"** The annotations in brackets 

 are taken chiefly from another paper by Stevenson."" 



Section of Monongahela formation in Fayette and Westmoreland counties, Pa. 



Feet. 



1. Waynesburg coal [fairly persistent in northern part of great bituminous field and on west, but 



locally absent in south and east; sometimes replaced by limestone breccia or iron] 6 



2. Sandy shale or sandstone [Browntown sandstone]; hard, gray, massive, in Harrison County, 



W. Va 20 



3. Little Waynesburg coal [thin, apparently confined to southwestern Pennsylvania and northern 



West Virginia] 2 



4. Waynesburg limestone [recognized generally in the Monongahela River valley of southwestern 



Pennsylvania and possibly in Broad Top field, but rarely in Ohio; usually over 8 feet thick, 

 but fades entirely to the south in West Virginia] 20 



5. Uniontown sandstone [coarse, gray, locally occupying interval in southwestern Pennsylvania, 



massive and conglomeratic in portions of the West Virginia area, shale in other regions] 50 



6. Uniontown coal [unusually persistent as coal or black shale, in Maryland, southwestern Penn- 



sylvania, and West Virginia, even in deeper bore holes, though apparently patchy north- 

 ward in Ohio; near type locality, Fayette County, it underlies a thin limestone with pelecy- 

 pods] 3 



7. Uniontown limestone [generally persistent, 2 to 12 feet thick, in Pennsylvania and most of 



Ohio and West Virginia, though not noted in some drillings on west side of basin; 160 feet 

 above Pittsburg coal in Salisbury basin (Somerset County, Pa.)] 12 



8. Sandstone [interval appears to change to "Tyler red beds" and "Ritchie red beds" of north- 



western West Virginia] 30 



9. Great limestone [later designated Ben wood limestone; thin along northern outcrop, lacking 



in portions of southwestern Pennsylvania; thickest (60 to 90 feet) in parts of Fayette and 

 Westmoreland counties; replaced by shale and sandstone locally; patchy and broken by 

 partings in northern part of Ohio area, fading to sandstone. and shale to south in Ohio and 

 West Virginia; includes Bulger and Dinsmore limestones] 80 



10. Sewickley sandstone [local, though massive or even double] 30 



11. Sewickley coal [Meigs Creek of Ohio; important and widely persistent, about 100 feet above 



base of series, in Maryland, Pennsylvania, Ohio, and most of West Virginia] 3 



12. Fishpot limestone [same as "Sewickley" limestone of Stevenson; gray limestone, variable to 



30 feet in thickness; absent east and south of area in southwestern Pennsylvania, northern 

 Ohio, and northern West Virginia, as well as from much of deep interior of basin; fades to 

 shale and sandstone to south; has "fresh- water" shells] '. 25 



13. Shale or shaly sandstone 20 



