542 GREAT SERPENTINE-BELT OF NEW SOUTH WALES, V., 



In 1893, in an address to this Society, Prof. David suggested 

 that the jasperoid slates of the Bingara, Barraba, and Nundle 

 District, which pass through the eastern portion of the area now 

 under discussion, may be altered abyssal deposits(6). Three 

 years later, he discovered that, not only do the jasperoid rocks 

 contain numerous spherical casts, probably replacing radiolaria, 

 but there is a large development at Tamworth of claystones and 

 cherts, and siliceous limestones, containing abundant radiolarian 

 remains, which he briefly described!?). He stated that there 

 appeared to be two beds of coral limestone, one of which was 

 greatly altered by the metamorphosing effect of the New England 

 granite. The thickness of the limestone he placed between 100 

 and 1000 feet, and added four more forms to the list of fossils. 

 He further remarked : " The claystones and cherty rocks, both 

 above and below the limestone, have also been much altered by 

 innumerable granite sills for a zone over five miles in width 

 measured at right angles to the junction line between the sedi- 

 mentary rocks and the granite. . . . The sills vary from a frac- 

 tion of an inch up to several feet in thickness, and at first sight 

 have every appearance of being regularly interstratified with the 

 sediments. A careful examination, however, at once revealed 

 their intrusive character, as they trespass slightly across the 

 planes of bedding, and have slightly altered . . . the sediment- 

 ary rocks both above and below them." In another paper he 

 said : "The whole zone for several thousands of feet is half sill, 

 half sediment."{8) So far, however, these apparently intrusive 

 rocks do not appear to have been subjected to microscopical 

 examination. 



In 1899 appeared the classical paper on this district, namely, 

 the account given by Professor David and Mr. Pittman con- 

 jointlyO). With this there is a geological map of the area. 

 The authors showed that there is an anticline in the valley of 

 Seven Mile Creek, east of the town, and adjacent to the bound- 

 ary of the granite. Metamorphosed limestone occurs on either 

 side of the axis. Above this, there continues a series of radio- 

 larian cherts, claystones, and lenticular patches of limestone, 

 interspersed with igneous rock. This dips steadily to the west. 



