SHENANDOAH LIMESTONE AND DEVONIAN SHALE. 187 



stone, much contorted and apparently broken up, shows also. It is not 

 continuous to the westward with the sandstone showing in the creek 

 section, because the main fault has here cut it out for a short distance. 

 The correspondence between the two sections is so close that there can 

 be no question about- the sequence. Everything is normal except the 

 limestone, and all the evidence goes to show that this is a projecting boss 

 that rises from below and now appears to penetrate the shales. This 

 limestone was examined by McCreath and d'Invilliers * in connection 

 with the ore, and was pronounced by them to be of Carboniferous age, 

 but they neglect to state the evidence upon which they based their 

 statement. 



The outcrop was examined by the writer quite carefully in order to 

 obtain some definite evidence as to its age, but no fossils were found. It 

 is a gray siliceous limestone, in places quite crystalline, and is certainly 

 cherty, for there were found in the clay resulting from the disintegration 

 of the limestone, along the line of contact, badl}^ decomposed cherts. In 

 almost all respects it resembles the Shenandoah limestone, but does not 

 bear any resemblance to the Carboniferous limestone. The ore is found 

 in pockets and small particles scattered through the clay. Altogether 

 the evidence is regarded as conclusive, and determines this limestone to 

 be the Shenandoah. The appearance in the ore-pit confirms this view, 

 as the limestone appears to descend indefinitely, with a wall of shale on 

 either side rising at least 50 feet above the lowest exposure of limestone ; 

 so that the writer came to the conclusion that it was a projecting boss of 

 limestone, around which the Devonian shales had been deposited, and 

 the presence of iron ore, occurring, as it almost invariably does, on the 

 southern side of the limestone, probably marks an old soil of residual 

 clay from which the iron has segregated. It is true that in the move- 

 ments which have since taken place a great amount of crushing has 

 occurred along the line of contact, but this in no way affects the evidence. 

 Again, about a mile due north of this area another of these limestones, 

 marked Y on the map, was found, only here it is free from ore and is a 

 much larger exposure. It has all the characteristics of the Shenandoah 

 limestone, but rises out of the Devonian shales in a narrow exposure, 

 probably three-quarters of a mile long and not more than 200 feet in 

 width. Both of these exposures have their longer axis on a line almost 

 due north and south and coincident, so that it has the appearance of a 

 narrow fold in the Shenandoah limestone, parts of which were eroded, 

 leaving isolated exposures on a line from Hamilton knob to Clarks 

 summit. At the latter place the limestone is again exposed, and again 



*The New River-Cripple Creek Mineral Region of Virginia, p. 141. 

 XXV— Bur.i,. Geol Soc. Am., Vol. 5. 1893, 



