BY W. N. BENSON. 329 



with ferruginous tuffs with limestone-fragments such as have 

 been already mentioned. Traces of a Stromatoporoid, of Favo- 

 sites multitabulata, Heliolites, and a large cyathopbylloid coral 

 were observed. These are insufficient to determine whether the 

 limestone belongs to the Nemingha or Loomberah horizon. It 

 runs due north, and is cut off to the south by a marked cross- 

 fault, which also truncates the adjacent serpentine. Limestone 

 again appears on the ridge in Portion 52, Loomberah, associated 

 with chert and spilite, all in a very shattered condition. This 

 lies in the transitional region between the Serpentine Line and 

 the Tamworth Series, but probably represents an altered form 

 of the Nemingha Zone. 



The great masses of jaspers, which are such a marked feature 

 of the Eastern Series in the Nundle District, are especially well 

 developed in the Wallaby Mountain, west of Woolomin, where 

 a strong band strikes across the mountain, forming the long 

 ridge which deflects the outlet of Cope's Creek, rising into the 

 high cliffs that form the eastern side of the mountain, and dying 

 out in the valley to the north. Other jasper-belts occur east of 

 this, nearer to Woolomin, and further long bands traverse the 

 Parish of Woolomin, and others occur east of Dungowan, though 

 the last are not so extensive as elsewhere. They result from 

 intense silicification along zones of shattering, and are not 

 primary deposits. 



The igneous rocks, other than tuff, namely the dolerites, 

 spilites, and keratophyres, occurring east of the serpentine, and 

 especially in the transitional zone west of the serpentine, are dis- 

 cussed below (p.342). 



The Tamworth Series. 



The region occupied by rocks of this division forms the greater 

 portion of the area considered, and, throughout this area, the 

 dips are nearly vertical or inclined to the W.S.W. at angles of 

 about 60°-70°, with only here and there a narrow band dipping 

 in the opposite direction. The total width of this region is 

 over four miles, so that, were no repetition of strata present, a 

 thickness of nearly 20,000 feet must occur, which is several times 

 greater than was shown to be probable in the Tamworth Dis- 



