1880.] A-KJO [Stevenson. 



served at the head of the South Fork of Powell river, where the divide be- 

 tween that stream and the West Fork of Stone creek joins the two moun- 

 tains. The figure exhibits the fact that here there isacnxcked anticlinal, with 

 the crack at some distance north from tlie line of the axis. The succession 

 of the rocks on the south side of the axis is continuous from the Lower 

 Helderberg to the Coal Measures, the latter being present in Hunter valley, 

 on the southerly side of Powell mountain ; but on the nortii side of the 

 axis the succession is broken, and the Black Shales of the Devonian rest 

 against the upturned beds of the Lower Carboniferous. It is evident that 

 during the plication of the rocks the beds gave way, and that the lateral 

 shove was so strong as to push those on one side of the fracture into an almost 

 vertical position, while those on the other side were simply raised or per- 

 haps pushed over on to the upturned edges of some lower rocks, which 

 are not shown at the surface along the li;ae of the fault. It is altogether 

 probable that the rocks now occupying the valley along the southern foot 

 of Stone mountain rest on beds of Vespertine age. 



The vertical extent of this fault is less than one might suppose, and 

 doubtless is little more than 6000 feel. Tlie Devonian is represented here 

 only by black shales, which are of inconsiderable thickness when compared 

 with the great mass of Devonian rocks in New York and Pennsylvania. 

 If erosion had not removed so much material along the Powell river and 

 its tributaries, one might have foimd throughout only the condition indi- 

 cated by the dotted lines in Fig. 2 ; and the vertical extent of the fault 

 would have been regarded as altogether insignificant, for the Lower Car- 

 boniferous limestone is practically in contact on both sides of the fault in 

 the vicinity of the Little Stone gap. 



TJie Fault of Poo?' Valley Ridge.— K. petty anticlinal exists between 

 Powell and Stone mountain in the valley near the Little Stone gap. Its 

 dips are more abrupt on the northern than they are on the southern side, 

 while at the same time they are much more abrupt near the axial line than 

 they are at a little distance from it. Only the Devonian and Lower Helder- 

 berg rocks are brought to the surface in the valley here. 



At but a little toward the west a crack appears in this anticlinal and soon 

 develops into the well-marked fault of Poor Valley ridge, which is approxi- 

 mately parallel to the Stone Mountain fault and lies at say three miles S. S. 

 E. from it. Erosion has been actively at work along the southerly side 

 of this fault and has divided Wallen's ridge into Poor valley ridge and 

 Wallen's ridge, the separation first becoming distinct at Cedar gap, some- 

 what more than a mile below the mouth of the South Foi-k of Powell river. 



As the two faults are approximate!}^ parallel, the dips are the same in 

 direction on the northern side of both ; but on the southerly side of the 

 Poor Valley Ridge fault, the dips are almost due east, as is well shown at 

 the head of Turkey cove. Entering this valley from the north by way 

 of Cedar gap, one finds the structure represented in Fig. I. The Clinton 

 rocks on the north side of the fault strike IST. 70^ E. The Lower Silurian 

 njcks, on the opposite side, which have been shoved into closelj^ compressed 



