586 EDWARD SAMPSON 



In eastern Australia is found a thick series of Devonian rocks. 

 They form a belt extending from Tamworth to Bingara. According 

 to David and Pittman^ they consist principally of "clay-stones" 

 with numerous interstratified bands of submarine tuff. There are 

 a few hmestone beds, one being 50 to 100 feet thick, and others 

 only from 6 to 12 inches in thickness. Near Bingara and Barraba 

 are exposed "several hundred feet of dark red-grey or greyish- 

 white jasperoid rock" which is thin-bedded. Most of these rocks, 

 including the limestone, are replete with radiolaria. 



Near Tamworth the chert is found only in small quantities. 

 Here there are many beds of tuff interbedded with the shale, large 

 sections showing beds of shale alternating with the tuffs. "The 

 shales sometimes pass into chert in contact with tuffs and cherty 

 masses occur inclosed within the tuff beds."^ In places there is 

 an extraordinarily intimate mixture of chert with tuff, the chert 

 occurring in disconnected areas of extreme irregularity.^ 



Radiolaria are found in all types of rock, cherts, shales, tuffs, 

 and Umestones, the latter yielding extremely well-preserved forms. 

 At many places Lepidodendron remains are abundant in the shales 

 indicating that the sediments were laid down near shore. 



Analyses of various types of rock are given and in discussing 



these the authors say: 



With reference to these analyses, we could comment on the fact that 

 although, so far as can be judged from the microscopic examination, the radio- 

 larian shales are almost as rich in radiolarian remains as the black chert, the 

 former contain only about 68 per cent of silica, while the latter contain 91.06. 

 This points, in our opinion, to the probability that the higher percentage of 

 silica in the chert is due, not to the sihca it has received from the radiolarian 

 tests, but rather to secondary sihca derived from the sihceous tuffs. 



Since the work of David and Pittman, Benson" has found that 

 spilitic lava flows occur in various parts of the section. He beheves 

 that they are submarine flows and cites one instance where the lava 

 contains coral fragments. 



^T. W. E. David, and E. F. Pittman, "On the Paleozoic Radiolarian Rocks of 

 New South Wales," Quar. Jour. Geol. Soc, Vol. LV (1899), pp. 16-37. 

 ' Ibid., p. 27. 3 Ibid., figure on p. 22. 



4 N. Benson, "Spilite Lavas and Radiolarian Rocks of New South Wales," Geol. 

 ., Decade V, Vol. X (1913), pp. 17-21. 



