GEOGRAPHICAL CHANGES DURING PENNSYLVANIAN 153 



shallow near the Pennsylvania-Ohio line, for in a considerable area that 

 limestone is represented only by occurrences of fossiliferous shale, more 

 or less calcareous; but the limestone reappears in central Tuscarawas 

 county, and thence southward it is recognized as limestone or as ore to 

 Breathitt county of Kentucky. In central and southern Ohio as well as 

 in Kentucky the main body of the limestone lay west from the outcrop, 

 and in much of the present area the horizon is traceable only by means 

 of the ore bed, which extends eastwardly for some distance beyond the 

 last trace of the limestone. The Vanport is richly fossiliferous. 



jSTo later important inroad of the sea occurred. The fossiliferous shale 

 overlying the Middle Kittanning is found only as far north as central 

 Ohio, while the Lower and Upper Preeport limestones, though extending 

 over a great part of the basin at the north, are either non-fossiliferous or 

 contain only fresh-water forms; but south from the Ohio river in Ken- 

 tucky the Upper Freeport limestone carries a characteristic Carboniferous 

 fauna. 



It is wholly probable that the Appalachian and the Indiana-Illinois 

 fields were not united during the Allegheny, though they may have been 

 during the Eockcastle, as they were during the Mississippian. 



Observers in Pennsylvania note at many places that the Homewood, 

 the last deposit of the Beaver, is continuous with a sandstone in the 

 Allegheny reaching at times to the Lower Freeport coal bed, but for the 

 most part to about the Vanport horizon. At a little distance on each 

 side the Allegheny portion of the sandstone disappears and the proper 

 section is found. Eecords of borings in West Virginia show the same 

 condition, with in some portions of the deeper area a much greater verti- 

 cal extent. Mr Eead gives a section in Coschocton county of Ohio where 

 a continuous sandstone, 280 feet thick, occupies a trough in Beaver and 

 Allegheny beds. Borings in Greene of Pennsylvania and Marshall, 

 Tyler, and Wetzel of West Virginia seem to show narrow areas in which 

 sandstone is continuous from Homewood far up into the Allegheny and 

 in some instances even into the Conemaugh. These may mark stream 

 courses, constantly agraded. It has been suggested that they are evi- 

 dence of local foldings and elevations in which valleys were made by 

 subaerial erosion. This explanation applies to very few of the examples, 

 since there is no nonconformity on either side. For example, in the 

 Ohio instance the Brookville coal bed rests on the sandstone, while at a 

 short distance away the same bed is shown with the Beaver beds below, 

 each with its proper interval for the region. 



Beyond all doubt, there were serious local irregularities, for intervals 

 often vary with extraordinary abruptness; but one must be cautious in 



