434 A. W. GRAB AIT PALEOZOIC DELTA DEPOSITS OF XORTH AMERICA 



southern exposure of this rock in the gorge of Wills Creek, where it cuts 

 through Wills Mountain just northwest of the city of Cumberland, 

 Maryland. I examined this small exposure in the center of the anticline 

 in 1910, but could not wholly satisfy myself of the relation of this to the 

 succeeding rock. It is not improbable that these red beds are post- 

 Juniata, or of Siluric (Medina) age, representing the reworked Ordo- 

 vicic Juniata, as will be more fully discussed further on. The fact that 

 the formation apparently grades upward into the overlying Tuscarora at 

 this point lends additional weight to the supposition that all of the red 

 beds shown may not be Ordovicic. Xevertheless, it must not be over- 

 looked that even if there is a hiatus between the two series of beds, as 

 would apparently be the case if the lower bed is true Juniata, the expres- 

 sion of this hiatus may be obscured by the reworking of a part of the 

 upper beds at the beginning of Tuscarora sedimentation. 



The red beds of the Wills Gorge section are interbedded sandstones 

 and shales, the former usually of slight thickness, though some of the 

 sandstones are over a foot thick. Clay galls and flattened clay pebbles 

 either red or green occur in some of the sandstones, and cross-bedding 

 of the torrential type is seen iu some of the higher beds. Lutaceous ma- 

 terial predominates, some of the shale beds being 6 feet or more in thick- 

 ness. Both shales and sandstones are more or less micaceous in character. 

 The total thickness measured by the Maryland Survey 48 is 530 feet, 

 though 140 feet is covered by talus. 



Farther north in the Wills Mountain Gap at Milligans Cove in Bed- 

 ford County, Pennsylvania, r 800 feet of the red sandstone are shown 

 resting on 100 feet of Bald Eagle. According to Bogers, 49 the formation 

 here contains more gray sandstone than usual. Throughout the Bedford 

 County district the Juniata "contains comparatively little soft shale, its 

 beds being chiefly hard, fine-grained red sandstone grits." Clay galls 

 and compressed clay pebbles are common, these usually being of an ochery 

 color and of such a condition as to easily weather out, leaving the rock 

 in a honeycombed condition. In other cases these clay galls are red in 

 color. As already mentioned, these sandstones overlap the Bald Eagle 

 in the southern part of Bedford County, where, in the sections made bv 

 the Juniata through Tussey and Evitts mountains, these red beds rest 

 directly on Upper Martinsburg sandstone and shale (here of Oswego age) 

 and form a continuous depositional series with it. Professor Stevenson 

 here found fossils which he identified as Ambonycliia [Byssonychial] 

 radiata and Bhynchonella capax. The latter has been identified by Ulrich 



48 Alleghany County, p. 87. 



49 Geology of Pennsylvania, p. 120 ; see also Stevenson Report T 2 . 



