THE ' 



GKOLOGICAL MAGAZINE. 



NEW SERIES. DECADE V. VOL. IX. 



No. VI.— JUNE. 1912. 



I. — B,ADIOLAErA-BKAKING RoCKS IN THE EaST InDIES. 



By J. B. SCRIVENOR, M.A., F.G.S. 



HAVING read with great interest Mr. E. E. L. Dixon's remarks 

 on the Kadiolarian cherts of Gower in the November number of 

 the Quarterly Journal of the Geological Society,^ I am tempted to offer 

 some notes on the occurrence of similar rocks in the Malay Peninsula 

 and Archipelago, where Hadiolaria-bearing rocks are known to be 

 widespread. 



The idea that Radiolarian cherts are not necessarily evidence of 

 deep-sea conditions has been steadily growing for a long time, but no 

 one, as far as I am aware, came to close grips with the problem of 

 their origin in shallow Avater until Mr. Dixon read the paper referred 

 to (I note that the date of reading was March 9, 1910). The theory 

 of a Radiolarian 'lagoon-phase' is the first serious attempt to 

 explain how Radiolarian cherts came to be formed in shallow water. 



The foundations of the ' deep-sea ' hypothesis having been under- 

 mined, it is only natural to inquire if, after all, any known outcrops of 

 Radiolarian rocks are evidence of deep-sea conditions apart from the 

 Barbadian rocks. An extremely interesting paper on this subject 

 was published in 1909 by Professor Molengraaf concerning widespread 

 Radiolarian rocks in Central Borneo, which Professor Molengraaf 

 believes to be oceanic deep-sea deposits.^ This paper is supplementary 

 to a previous publication, and in order to appreciate its full significance 

 we must go back some years. In 1902 Professor Molengraaf published 

 the results of his explorations in Central Borneo during 1893-4.^ In 

 this volume the ' Danau formation ' is described.* It comprises 

 diabase-tuff, diabase-porphyrite, quartzite, chert, jasper, hornstone, 

 clay-slate, and sandstone, the leading rocks being silicified and partly 

 serpentinized diabase-tufp and jasper.^ The jasper and hornstone were 

 found to contain many Radiolaria, described by Dr. G. J. Hinde in an 

 appendix. Their examination led to the conclusion that the rocks 



^ " The Carboniferous Succession in Gower, Glamorganshire, etc." : loc. cit., 

 vol. Ixvii, pp. 511-31, 1911. 



^ G. A. P. Molengraaf, " On Oceanic Deep-sea Deposits of Central Borneo " : 

 Proc. Koy. Acad. Amsterdam, vol. xii, pp. 141-7, 1909. 



^ Geological Explorations in Central Borneo, English edition, London, 1902. 



* pp. 414-21. 



° Op. cit., p. 414. 



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