NORTH AMERICA AND THEIR VERTEBRATE FAUNA. 8l 



Condit* describes the general outline and condition of these deposits: 



"The Conemaugh formation outcrops in a broad band, lo to 20 miles wide, 

 across the southeastern part of Ohio, and extends eastward, under cover, into West 

 Virginia and Pennsylvania, again rising to the surface towards the eastern edge of 

 the Appalachian coal basin. The strata included within this formation lie between 

 the base of the Pittsburgh and the top of the Upper Freeport coal, and have a thick- 

 ness in Ohio of 355 to nearly 500 feet. The area of outcrop * * * extends eastward 

 across Pennsylvania around the northern margin of the Appalachian coal basin, 

 thence southward through western Maryland and eastern West Virginia. From 

 southern Ohio the exposures may be traced into eastern Kentucky and West Virginia. 

 Hence, it is evident that, structurally, the ' Coal Measures ' area of Pennsylvania, 

 Maryland, West Virginia, Kentucky, and Ohio is a broad synclinal basin, into which 

 the rocks slope from the margin. The gentle southeasterly dip in Ohio is persistent 

 for a distance into West Virginia, carrying the Conemaugh strata hundreds of feet 

 below drainage, but beyond the middle of the basin the rocks rise again to the 

 surface. 



"As to the lithological character, the formation consists mostly of sandstone, 

 sandy shale, and clay, much of which has a reddish-brown color. Coal seams and 

 limestones are few and thin. All the beds are characterized by lack of persistence, 

 and vary greatly as to thickness and appearance from place to place. Local erosion 

 planes and unconfonnities of small magnitude are extremely abundant and occur 

 at all horizons. The hiatuses are shown by conglomerates and truncated strata. 

 Frequently the material of the conglomerates can be traced to some nearby fossilif- 

 erous limestone bed or coal-seam. 



' ' Much of the lower half of the Conemaugh formation is of marine origin and 

 has a number of fossiliferous horizons. The highest fossil-bearing beds, lying a 

 little above the middle, mark the final invasion of the sea into the Appalachian 

 Basin. All the overlying strata lack forms of undoubted marine origin, the fossils 

 being mostly plant remains, certain minute fossils, such as Spirorbis, ostracods, and 

 gastropods, generally regarded as fresh- water, together with occasional fish, amphib- 

 ian and reptilian bones. Insect remains are sometimes found well preserved in the 

 shales. The marine limestones of the lower half of the formation are the most per- 

 sistent and lithologically uniform beds, but these have suffered contemporaneous 

 erosion and locally failed to form, owing to the unfavorable conditions, such as the 

 presence of shoals in the sea and continuous sedimentation from rivers." 



Condit '' gives the following list of the beds in the Conemaugh formation 



in Ohio and their equivalents in West Virginia: 



Ohio. West Virginia. 



Pittsburgh limestone Upper Pittsburgh limestone. 



Little Pittsburgh coal (upper). 

 Bellaire sandstone Lower Pittsburgh sandstone. 



Little Pittsburgh coal (lower). 



Summerfield limestone Lower Pittsburgh limestone. 



Connellsville sandstone Connellsville sandstone. 



Little Clarksburg coal Little Clarksburg coal. 



Clarksburg limestone Clarksburg limestone. 



Morgantown sandstone Morgan town sandstone. 



Elklick coal. 



Elklick limestone. 



Birmingham shale Birmingham shale. 



Skelly limestone. 



Ames limestone Ames limestone. 



' Condit, Conemaugh Formation in Ohio, Bull. 17, Geol. Bur. Ohio, p. 14, 1912. 

 '■Condit, Geol. Sur. Ohio Bull. 17, p. 20, 1913. 



