132 



THE GEOLOGY OF TASMANIA— THE PRE-CAMBRIAN. 



to the eastward. But the junction of the two systems 

 is rendered complex by faulting (i). 



These infra-Ordovician sediments cannot 3^et be 

 satisfactorily correlated with any of the other develop- 

 ments of Cambrian rocks in Tasmania. 



The character and succession of these beds, albeit 

 questions of great interest, cannot here be more fully 

 discussed. We are concerned rather with the relation- 

 ship of these Cambrian rock groups to the foundations 

 upon which they rest. 



In this matter also the most satisfactory evidence 

 has been gathered by Mr. W. H. Twelvetrees near the 

 northern extremity of the Denison Range. 



Passing westwards, Mr. Twelvetrees has observea 

 that the siliceous sediments, upon which the Ordovician 

 limestone rests unconformably, themselves rest uncon- 

 formably upon the foliated rocks which are here re- 

 ferred to the Pre-Cambrian. The actual junction has 

 been observed on the western side of the Denison 

 Range, in the neighbourhood of the North Star (2). 



The writer has observed the similar reddish quartzite 

 on the edge of the central plateau near Mount Arrow- 

 smith, resting unconformably on the quartz-mica 

 schists which are described below. 



In the valley of the South Loddon River the tubi- 

 colar and discoidal sandstone have been observed rest- 

 ing unconformably upon micaceous schists (3). 



At Mount Farrell, the eastern wall of the valley of 

 the Sophia River is constituted of the quartz-mica 

 schists mentioned below. These give place, on the 

 western wall of the valley, to the West Coast Range 

 conglomerate and quartzite which form the ridge of 

 Mount Farrell ; and these in turn are followed bv the 



(i) See Section III. 



(2) See Section I. 



(3) See Section II. 



