Palaeozoic Geology oj Victoria, 79' 



up to the junction. Following the river bed upstream, the Serpentine 

 about one chain in width passed serpentinous and ferruginous shale- 

 of the Garvey Gully type, highly ferruginous here on account of 

 weathering. The rock continues for about eight chains, when a 

 hard cherty band of contorted slates is encountei-ed. It is about 

 two chains wide and definitely lipper Ordovician, from wliich 

 characteristic graptolites have been obtained. At first sight, the 

 band has the appearance of being interbedded with the Cambrian 

 sediments, but palaeontological evidence supported by petrological. 

 differences and comparison with similar small outliers of Upper 

 Ordovician in the vicinity, shows that the occurrence is due to 

 intense folding which has nipped portions of the overlying Ordo- 

 vician into the Cambrian. Continuing with the section, the cherts 

 are followed' again by a belt of about 10 chains of typical greenisli 

 basic tuffs with interbedded Cambrian limestone about one chain 

 wide and beyond this to the south-west, these rocks are bounded 

 by a belt of contorted Upper Ordovician cherts. 



The contact between the two series is shown in a small gully 

 which enters the Dolodrook at the limestone outcrop. It is situated' 

 about five and a half chains from the junction in a south-west 

 direction. The passage from basic tuffs to cherty slates is sharp, 

 with about two feet of gossany material in between, probably 

 occupying a fault. The rocks are highly inclined and disturbed on 

 either side. 



A chemical analysis of the tuff is appended, showing its basic- 

 character. 



I. 



SiO, . 



50.09 



AiA- 



12.69 



FeA- 



5.30 



FeO - 



12.01 



TiO^ - 



2.12 



CaO 



5.08 



MgO- 



5.60 



H^O- 



0.40 



H,0 + 



2.72 



Na^O- 



2.54 



KiO - 



1.32 



CO, - 



0.80 





100.67 





IT. 



. 



48.11 



_ 



13.30 



. 



3.70 



_ 



8.10 



. 



MnO 1.43 



_ 



8.48 



. 



9.51 



Loss 



on Ignition 4.21 





1.96 



- 



1.57 



- 



— 



100.37 



S.G. 2.86 

 (I.) Green banded tuff— Garvey Gully series Dolodrook River 

 (Teale.) 



