128 THE GEOLOGY OF TASMANIA— THE PRB-CAMBRIAN. 



A short explanation appears necessary in order that 

 the character of the evidence, upon which the age of 

 these five groups has been stated to be, in all proba- 

 bility, Cambrian, may be clearly stated. 



I. The Dundas slate series consists of clay slates, 

 sandstones, conglomerates, and breccias, with which are 

 associated a characteristic series of massive and schis- 

 tose igneous rocks. They extend from the North Coast 

 between Penguin and TJlverstone to Birch's Inlet on 

 Macquarie Harbour, and probably still further to the 

 southward. 



The rocks of this series are judged to be of greater 

 antiquity than the 'Gordon River limestone on strati- 

 graphical evidence (i). 



2. The Caroline Creek beds consist of yellow sand- 

 stones, which are fossiliferous in both localities where 

 they outcrop, and have been definitely referred to the 

 Upper Cambrian upon the evidence of the organic re- 

 mains preserved in them. 



3. The " tubicolar " sandstone forms a well-marked 

 horizon, which has been recognised at Mount Zeehan, 

 Middlesex, Mount Claude, the Five-mile Rise near 

 Lorinna, and on the Loddon Plains to the eastward of 

 the Frenchman's Cap. 



To this horizon has hitherto been assigned a much 

 higher position in the geological column by other 

 authors. The writer considers that it is of Cambrian, 

 age for the reasons here briefly stated : — 



The peculiar tubular impressions have been recog- 

 nised in the West Coast Range conglomerate on the 

 Mount Lyell peaks. 



The tubicolar sandstone proper overlies the West 

 Coast Range conglomerate conformably at Mount 

 Zeehan, and the relationship of the two formations is 

 shown in Mr. Waller's section across Mount Zeehan (2). 



Hence, whatever may be the nature of these proble- 

 matical fossil casts, they are persistent through at least 



(i) Geological Survey of Tasmania, Bullelin No. 5, pp. 

 8-10. 



(2) G. A. Waller, " Report on the Zeehan Silver-Lead 

 Mining Field," 1904. 



