410 CHARLES S. PROSSER 



kindly placed at his disposal, and has recently been published 

 under the auspices of the state survey. 



THICKNESS 



The strata covering Allegany county have a thickness vary- 

 ing from about 13,300 to 16,000 feet. This thickness is divided 

 between the four geological systems represented in the county 

 in the following manner: Silurian, from 2200 to 2400 feet; 

 Devonian, 7875 to 10,200 feet; Carboniferous, 2825 to 3000 

 feet, and Permian ( ?) , about 400 feet. 



SILURIAN STRATA 



Jiutiata formatio7i. — The oldest rocks outcropping in Allegany 

 county belong in this formation, and are shown in only one 

 locality. This outcrop forms the lower part of the cliffs in the 

 gorge known as "the Narrows" just northwest of Cumberland, 

 where Wills Creek has cut a deep and narrow trench through Wills 

 Mountain. This gorge presents an admirable example of a narrow 

 transverse valley where a stream has cut through a mountain 

 ridge, and this locality has a justly deserved reputation for great 

 natural beauty. The upper 370 feet of the formation is well 

 shown on the northern side of the creek ; but in many places in 

 the gorge it is concealed for the most part by heavy talus of white 

 quartzite blocks from the cliff above. In the Narrows 550 feet 

 of the Juniata are shown, but no fossils have been found at this 

 locality. The formation is composed of alternating beds of deep 

 red shales and sandstones which have no regularity of succes- 

 sion, but show a much greater total thickness of shales than 

 sandstones. The sandstones are hard, fine-grained, cross- 

 bedded, and micaceous, some of the strata a foot or more in 

 thickness, but usually less than six inches. The shales are 

 micaceous, weathering readily, and the beds vary from an inch 

 to six feet or more in thickness. This formation was named 

 from the Juniata River, Pa., though in the earlier reports of that 

 state it was termed the Medina or Levant red sandstone (No. 

 Wh). It probably represents the older part of the Medina 



