[Proc. Eoy. Soc. Victoria, 21 (N.S.), Pt. I., 1908.] 



Art. v. — The GlierU and Diabase Rocks of Tatong. 



By H. S. summers, M.Sc. 



(Geological Laboratory, Melbourne University.) 



(With Plate IX.). 



[Eead 9th April, 1908]. 



In Vol. L, part 4 (1907) of the Eeoords of the Geoloorical 

 Sui-vey, Mr. A. M. Hewitt briefly describes a series of cherts 

 with associated hornblendio dyke occurring about a mile to the 

 south-easit of Tatong township. From the similarity of these 

 rocks to the cherts of Heathcote, Mr. Howitt concludes that 

 they probably belong to the Heathcotian series described by 

 Professor Gregory. (i) 



In December, 1905, I accompanied members of the Benalla- 

 Tolmie Railway League from Benalla to Tolmie via Tatong and 

 Spring Creek, and in a brief report in the '' Benalla Standard " 

 of the geological features along the proposed route, I recorded 

 the presence of a large area of diabasic rocks neai' the junction 

 of the Holland's Branch of the Broken River, and one of its 

 tributaries, Spring Ci"eek. Cheai:y rocks were found associated 

 with the diabase, and the general lithologioal character of the 

 series showed that they presented strong resemblances to the 

 Heathcote rocks, and consequently they were recorded as being 

 probably of Heathcotian age, that is, of pre-Ordovician age. 



On further investigation, however, no sharp junction could be 

 found between the cherty series, and the less altered sedimen- 

 tary rocks with which, in Mr. Howitt's map, they are shown in 

 contact, and one is forced to the belief that the two form only 

 a single series in which a gradually increasing metamorphism 

 can be noticed as the diabases are approached, the cherts re- 

 presenting the extreme stage of such alteration. 



1 Proc. Roy. Soc. Victoria, vol. xv. (N.S.), pt. ii. (1903), p. 148. 



