CORRELATION OF ALLEGHENY FORMATION 69 



Dunkard Upper Barren series of Stevenson ; upper part 



I. C. White, 1891. of Greene County group of H. D. Rogers ; 



upper part of Upper Coal Measures of New- 

 berry ; upper part of XV of W. B. Rogers. 

 In the description of the several formations, the names here given will 

 be employed as limited by Franklin Piatt and I. C. White. 



Allegheny Formation 

 correlation 



The plane of separation between the Pottsville and the Allegheny in 

 the bituminous area is marked on top of the Homewood sandstone, but 

 only approximately, for, as will be seen, that sandstone is replaced more 

 or less by shale in extensive spaces, while in others it is continuous with 

 sandstone extending upward even into the Conemaugh. A more con- 

 venient base is the Brookville coal bed, belonging a few feet above the 

 Homewood in its normal condition. The Allegheny is paleontologically 

 as well as stratigraphically distinct from the underlying Pottsville ; for, 

 although the fauna exhibits comparatively little change, there is, as shown 

 by Mr David White, for a great part of the field a very marked difference 

 in the flora. 



The Allegheny area is much smaller than that of the Pottsville. It 

 becomes narrow in southern West Virginia and northeastern Kentucky. 

 The present condition of our knowledge makes impossible any positive 

 conclusions respecting its extent in southeastern Kentucky and south- 

 western Virginia, though reconnaissance work in the former state suffices 

 to show that Allegheny coal beds are present there. It is possible that 

 the formation reaches into the northeastern corner of the Tennessee coal 

 field. Uncertainty prevails respecting the correlation of beds in the 

 anthracite areas of Pennsylvania, which will be considered apart after the 

 description of the Conemaugh. 



Though comparatively thin, at most little more than 300 feet, the Alle- 

 gheny contains a large number of elements, most of which are persistent 

 for long distances on both sides of the basin, though practically all be- 

 comes unidentifiable in much of the broad interior, where throughout 

 the Coal Measures the coal beds and limestones disappear or become in- 

 definite and there remains only detrital matter of variable character. 

 The important elements are: 



Upper Freeport coal bed. 

 Upper Freeport limestone. 

 Butler sandstone. 

 Lower Freeport coal bed. 



