Rocks of the Howqua River. 5d* 



sn: 



-1 I j I 



Shaly Bro/ien s/dtednd shdit 



mt/ (7 stone a hour /cAnh 



ci b c de f y 



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



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

 A Comparative Review. 



Ihese rocks from stratigraphical 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 strengthened, and much 

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

 made of 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 be 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 

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

 of Protospo7igia cherts and overlying Lower Ordovician rocks, con- 

 taining such graptolites as Tetragrapfus and Bidymograptus. At 

 the Dolodrook, Upper Ordovician rocks come 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,. 



