18 PROF. T..W. E. DAVID & MR. E. F. PITTMAIT [Feb. 1 899, 



on the western side of the cave-limestone. Obscure traces, however, 

 of radiolarian casts may be observed in the shales east of the caves, 

 and underlying the limestone. The radiolarian rocks have been 

 traced for at least 5 mile west of the caves, the best sections being 

 exposed in McKeown's Creek, and for about 1 mile eastward to 

 Inchman's Creek. As it is still uncertain whether the Jenolan 

 limestone is of Silurian or of Devonian age, it may be premature as 

 yet to attempt its correlation with the Tamworth beds. If it be 

 homotaxial with them, the radiolarian rocks will be proved to have 

 a range of at least 285 miles, from Jenolan on the south to Bingara 

 on the north. 



III. Stratigraphy of the Radiolariait Eocks. 



(i) In the neighbourhood of Bingara and Barraba there is a 

 remarkable similarity in the lithological character and mode of 

 occurrence of the radiolarian rocks. They consist of jointed clay- 

 stones, of a dark bluish-grey colour at some depth from the surface, 

 weathering yellowish-brown, with very numerous interstratified beds 

 of submarine tuff and thick bands of coral-limestone. 



So far as observed, the strata are all more or less fine-grained, 

 the individual particles composing the rock being as a rule not more 

 than 0'05 mm. in diameter, with the exception of the radiolaria, 

 whose diameter ranges from about 0*125 up to about 0*41 mm. 



A conspicuous feature in the geology of this district is a belt of 

 serpentine, from 5 to J mile wide, extending south-south-east from 

 Bingara to the coast at Port Macquarie, a distance of 180 miles. 

 A zone of red and dark-grey or greyish-white jasperoid rock, several 

 hundred feet in thickness, runs parallel with the serpentine-dyke on 

 its E.N.E. side. It is not yet certain that the jaspers owe their 

 silicification or their red colour to contact-metamorphism induced by 

 the serpentine-dyke. That the latter is intrusive is proved by the 

 nature of its junction with the sedimentary rocks, as seen at Barraba 

 and Bingara, where small veins and tongues of serpentine, offshoots 

 of the main mass, may be observed intersecting and penetrating the 

 sedimentary rocks. 



That this dyke has materially influenced the metalliferous 

 character of the neighbouring sedimentary rocks is proved by the 

 existence of numerous gold-bearing veins in close proximity to it, 

 for a considerable distance along its course. The gold-veins have 

 been worked at Bingara, Woodsreef, Ironbark, Crow Mountain, 

 Ti Tree, Bowling Alley Point, Hanging Eock, near Nundle, etc. 

 "With regard to the red colour of some of the jaspers, the fact should 

 be mentioned that near Ironbark, in the Barraba district, there are 

 beds of hard red clay-shales, interstratified with the jasperoid 

 series, which appear to owe their red colour to haematite formed 

 contemporaneously with their deposition, and therefore prior to the 

 intrusion of the serpentine-dyke. The serpentine appears to have 

 resulted from the alteration of an ultrabasic rock, rich in olivine 



