BY W. N. BENSON. 707 



B. Sedimentary Rocks. 



Classification. — The sedimentary rocks will be described in order 

 of their stratigraphical succession, an arrangement which, while 

 necessitating some slight repetition, will best indiqate the re- 

 semblances and differences, in the lithological characters, of the 

 various series. 



(l)The rocks of the eastern series are all much altered. They 

 consist of phyllites, jaspers, and metamorphosed members of the 

 western Devonian, and possibly Carboniferous groups. As before 

 pointed out, spilite-lavas occur in great abundance throughout this 

 series, and, where greatly sheared, veined, and otherwise altered, 

 they are easily mistaken, in hand-specimen, for altered, sedimen- 

 tary rocks, more especially if the spilite be one of the highly 

 felspathic type. 



Unfortunately, only a small collection of eastern rocks was 

 made, and hence this paragraph can give but an incomplete 

 description of the series. Such studies, as have been made, show 

 that it is only by the microscopical study of a large series of these 

 rocks, that the nature and stratigraphy of the eastern series can be 

 finally elucidated. 



The following are the rocks that have been determined, and 

 their probable equivalents, among the unaltered types, are indi- 

 cated. The mudstones and clay-shales are represented by sericitic 

 phyllites. In the neighbourhood of the red jaspers, these may 

 become more ferruginous, and pass locally into hsematitic schists. 

 Conglomerates, such as cross the Peel River, south of Nundle, are 

 represented in the narrow band of schistose conglomerate on the 

 Namoi River, near its junction with Ireland Creek. They contain 

 fragments of granite, etc. 



The altered breccias, that occur on Wiseman's Arm Creek. M.B., 

 273, can be clearly correlated with the Tamworth breccias; while 

 green, schistose greywaekes may represent the tuffs of the Upper 

 Tamworth beds. Occasionally, these may contain small, circular 

 or oval areas, suggesting the presence of radiolarian casts. A 

 typical, altered tuff [e.g., M.B., 53; from Woods' Reef] is com- 



