PBESIDENTIAL ADDRESS. 25 



Infolded amongst these Algonkian rocks are strata of 

 Cambrian, Ordovician and Silurian Age thrown into long 

 folds approximately parallel to the older trend lines of the 

 Pre-Oambrian rocks. These strongly marked N.N.W. and 

 S.S.E. trend lines of the western side of Tasmania are 

 crossed by a line of granite intrusion which may be termed 

 the Waratah axis, as it runs through the Mount Bischoff 

 Mine at Waratah; this trends about N.E. and S.W. On 

 the east coast the long meridional line of granite intrusions 

 extending from the Hippolyte Rocks on the S., through 

 Maria and Schouten Islands, Freycinet's Peninsula, St. 

 Patrick's Head, St. Helens and Cape Barren Island and 

 Flinders Island, marks a strong N. and S. tectonic line. 



In the V formed by these two dominant trend lines is 

 enclosed the Permo-Oarboniferous and Trias-Jura basin 

 with their massive sills of quartz-dolerite or quartz-diabase. 

 Mr. Twelve trees has shown that the alkaline rocks of the 

 Port Cygnet district have broken out along a line trending 

 S. 40° W., and that the distribution of the melilite basalts 

 of Tasmania indicate an eruptive line trending about E. 

 and W., near Lake Sorrell, and about E. 10° N. near Hobart 

 between Rokeby and One Tree Point. The geological 

 faults of Tasmania have not yet been worked out. Mr. 

 Montgomery 1 records minor faults with throws of about 

 200 feet at Beaconsfleld to the north of Launceston. 



Mr. E. 0. Andrews 2 has enumerated some probable lines 

 of heavy fault as indicated by physiographic evidence, as 

 follows: — Ben Lomond, Western Tiers, Mounts Roland and 

 Wellington, north-east coast and east coast. R. M. John- 

 ston 3 has already figured, on direct stratigraphic evidence 

 several important faults on the south side of Mount Well- 

 ington. The line of melilite basalt eruption already 



1 Eep. Austr. Assoc, for Adv. of Sci., Hobart, Vol. iv, pp. 321-327. 



2 This Society's Journal, Vol. xliv, 1910, p. 477. 



3 Geology of Tasmania, p. 163, see section opposite page. 



