Rocks of the Howqua River. 59' 



S.W. 



b c de f '/ 



Fig. 4. — Section across outcrop of phosphate breccia. 



E. Concerning the Age of the Diahase and the Cherts. — 

 A Comparative Revietv. 



These rocks from stratigrapliical considerations appear to be 

 the oldest rocks in this region, which necessarily places them low 

 down in the older Palaeozoic series, but on the evidence available 

 in this region alone it would be difficult to assign a definite horizon 

 to them. 



The view in this direction, however, is sti-engthened, and much 

 uncertainty as to age is removed, when a comparative review is 

 made oi other closely similar occurrences in the State. Various 

 gaps in the evidence, which make any one area in itself incomplete 

 disappear when all are taken in conjunction. The other areas 

 which call for special consideration in this direction are : — 



1. Heathcote. 



2. Dolodrook River, near Mount Wellington, Gippsland. 



The fossil evidence of the Dinesus beds with associated Proto- 

 spongia cherts, at Heathcote, established the age of the rocks as 

 Cambrian. 



There would seem to he little doubt that the Howqua rocks 

 are on an extension of the Dolodrook line, where the age is definitely 

 fixed by the tribolite limestone. The absence of this evidence at the 

 Howqua, however, is counterbalanced to some extent by the presence 

 of Frofosjjongia cherts and overlying LoAver Ordovician rocks, con- 

 taining such graptolites as Tetragraptvs and Didymograjitus. At 

 the Dolodrook, Upper Ordovician rocks oome directly in contact 

 with the Cambrian. Again, as an offset against the paucity of 

 direct fossil evidence at the Howqua, we have the very complete 

 lithological resemblances and mineral changes which match the- 

 typical Heathcote occurrences. There would seem little doubt,. 



