PRESIDENTIAL ADDRESS. 17 



Lofty Ranges represent Cambrian strata which have 

 experienced intense contact metamorphism as the result 

 of the intrusion of large contiguous belts of granite. 



Mr. Howchin, at the same time, has recorded the exist- 

 ence of Pre-Oambrian rocks in the neighbourhood of Aldgate 

 in the Mount Lofty Ranges, where their general trend lines, 

 as far as they can be seen, correspond with those of the 

 overlying Cambrian rocks. Certainly the Cambrian 

 cleavages and joint planes pass directly downwards into 

 those of the Pre-Oambrian. 



Mr. W. N. Benson, i3.sc. 1 states (op. ctt., p. 107) that "in 

 each of the three periods of great earth-movements evi- 

 denced in the Mount Lofty Ranges, viz. (1) the Pre- 

 Oambrian, (2) the older Palaeozoic Post-Cambrian, (3) the 

 late Tertiary, the axis of folding or faulting was almost a 

 meridional one. From Yankalilla to Aldgate, in the southern 

 part of the Mount Lofty Ranges there appears to be an 

 approximate agreement in direction between the Pre- 

 Cambrian and older Palaeozoic Post Cambrian folding. At 

 the same time it is generally admitted that there is a strong 

 unconformity between these two groups of rocks.'' 



Again in Yorke Peninsula, near the Parara Mine, west 

 of Ardrossan, Mr. Otto Tepper 2 shows that there is no 

 great divergence between the strike of foliation there of 

 the schists of Pre-Cambrian age and that of the Lower 

 Cambrian limestone. He gives the strike of these Pre- 

 Cambrian strata as N. 5° W., 3 at the Parara Mine, and N. 

 8° E. at Mooloowurtie, the dip of the foliation at the Parara 



1 Trans. Eoy. Soc. S. Australia, Vol. xxxm, 1909, Petrographical 

 Notes on Certain Pre-Cambrian rocks of the Mount Lofty Eanges, with 

 special reference to the Geology of the Houghton District, pp. 101 - 140, 

 pis. i - v. 



2 Trans. Phil. Soc. Adelaide, 1877-8, pp. 71 - 79, Cliffs and Eocks at 

 Ardrossan, Yorke Peninsula. 



3 The bearings given from here to the end of the paper are magnetic, 

 except in the case of the bearings relating to West Australian areas. 

 The latter bearings are true. 



B— May 3, 1911. 



