STRATIGRAPHY OF OHIO WAVERLY FORMATIONS 673 



south line of Vinton County. It has not been traced into Jackson 

 County where a few miles farther to the southward it must pass 

 below drainage. 



Over the center of the province, the Black Hand is a coarse 

 pebbly sandstone with occasional beds of conglomerate. The peb- 

 bles, all quartz, seldom exceed an inch and a half in diameter. 

 The most striking feature of the member is the bedding, which is 

 inclined at angles ranging commonly from 10° to 20° and sometimes 

 reaching 25° or even more. This structure is much more promi- 

 nent on the eastern side of the area. This inclination is found 

 throughout most of the thickness of the Black Hand, only the top- 

 most 10-25 feet lying horizontally. The inclined beds correspond 

 in a way to the foreset beds of a delta, the horizontal beds above 

 to the top-set beds. The inclination is almost always toward the 

 northward or at least with a northerly component. 



When all the features of the Black Hand and Fairfield members 

 over the area of the facies are taken into consideration, it is evident 

 that the members are distinct. Yet it may be difficult to draw the 

 Une between them in any given section, especially in the southern 

 part of the area in western Hocking County. It is impossible here 

 to discuss the relation of one bed to the other. Owing to the 

 physical nature of the members, the contact is almost always cov- 

 ered except for short exposures of a few feet at wide intervals. 

 Where the members are well developed there is almost invariably 

 an erosion plane present at or near this contact. But whether 

 this is a plane of unconformity between the two members or is 

 merely another of the commonly observed erosion surfaces, several 

 of which can sometimes be seen in a single outcrop and most of 

 which are obviously local, is not yet fully determined. In any 

 event the erosion plane, if there is an extensive one, disappears 

 near the margin of the facies as the coarse sediments give place to 

 shales, and is believed to be of no great significance. Whether 

 these conglomerate facies be regarded as deltas of a peculiar type 

 or as bar formations, the surface of the accumulation at any given 

 time stood well above the mud floor of the adjacent shale facies 

 and was Hable to erosion over portions of its surface under con- 

 ditions which would not affect the adjoining deeper areas. 



