188].] ^4:t5 [Stevenson. 



around the headwaters of the South Fork of Powell river and its tributary, 

 Wildcat creek. This embraces so much of the region between Stone 

 mountain and Powell mountain as is drained by those streams. 



At the apex of this space, where Stone and Powell mountains come to- 

 gether, just east from Little Stone gap, one finds in the valley only the 

 Hamilton shales. The gentle anticlinal, in which the fault of Poor Valley 

 ridge originates, soon brings up the Oriskany, the Lower Helderberg, and, 

 at a little way further west, the Clinton ore group. The ridge formed by 

 the anticlinal and gradually developing fault is known here as Wallen's 

 ridge and shows the Clinton group on both sides, with the higher groups 

 at a little distance from the foot. No detailed section was made on Pow- 

 ell mountain, but the Hamilton shales are at its base ; higher up is the 

 Lower Carboniferous, forming a conspicuous band along the face of the 

 mountain ; while above it the Quinnimont group extends to the crest, 

 whence it may be followed to the Hunter valley. 



Along Wildcat valley and the southerly slope of Wallen's ridge. Upper 

 Silurian rocks prevail, the Medina at the crest of the ridge, the Clinton 

 lower down the slope, while the Lower Helderberg occupies the valley and 

 here and there reaches some way up the side of the ridge. The Clinton 

 ores are unusually good here, that from one bed showing 52.6 per cent, of 

 iron with but 0.116 per cent, of phosphorus.* The Lower Helderberg 

 shows two ore-horizons, of which the upper may belong in part to the 

 Oriskany. The lower horizon has an unusually good brown hematite, with 

 52.55 per cent, of iron and only O.Ool per cent, of phosphorus. The pockets 

 of good ore are separated by stretches of varying length, in which an 

 enormous amount of brown hematite is seen, but so mixed with sand as to 

 be altogether unavailable. Beyond all doubt the higher horizon carries 

 much good ore, but the old workings, whence ore was obtained for a 

 Catalan forge, have been filled up and only the silicious ore is exposed. 



The Helderberg ores of Poor valley are of uncertain value. Some fair 

 ore occurs at several miles east from Big Stone gap, but the most of that 

 seen there is silicious and evidently belongs to the higher horizon. It con- 

 tains many fossils characteristic of the Lower Helderberg. Further Avest, 

 the ore seems to be wanting, no evidence of its presence having been ob- 

 served at any exposure between Big Stone and Pennington's gap. 



The best exposure of the Hamilton shales in the Poor valley is at a mile 

 or so east from the Big Stone gap, where the rock seems to be thicker than 

 it is further west. It is said to yield fossils there. The increasing strength 

 of the disturbance westward makes the dip of these beds vertical before 

 reaching Pennington's gap and exposures in that vicinity are not wholly 

 satisfactory. The valley itself is very narrow until beyond that gap, 

 where it opens up somewhat. No trace of Chemung rocks were found in 

 the valley and the Lower Carboniferous rests directly on the lower black 

 shales of the Hamilton. 



*AU analyses in this memoir, unless otherwise stated, are by Mr. A. S. Mc- 

 Creath, chemist to the Second Geological Survey of Pennsylvania. 



PROC. AMER. PHILOS. SOC. XIX. 108. 3e. PRINTED FEBRUARY 25, 1881. 



