president's address. 549 



Archpean rocks and the overlying Lower Cambrican Limestone, the 

 Parara Limestone as figured by Mr. Otto Topper.'^ 



In the above section the Parara Limestone is shown dipping at 

 an angle of only 15° off the Ardrossan marble, which dips at 591°. 

 In a subsequent report,! however, Mr. Tepper expresses his belief 

 that the Ardvossan marble is probably of Cambrian Age and 

 passes up conformably into the Lower Cambrian Parara Limestone. 



No organic remains have hitherto been detected in these rocks. 

 A specimen exhibiting a structure somewhat resembling macrosco- 

 pically that of Eozoon Canadense was collected by Mr. C. S. 

 Wilkinson, the late Government Geologist of New South Wales, 

 from these Archpeans, but proved on microscopic examination to 

 differ from that sui)posed organism, and was certainly inorganic. 

 The marble limestone of Ardrossan, however, is very suggestive 

 of contemporaneous life, but it may be of Cambrian Age. 



These rocks were folded on N.E. and S.W. axes before the 

 commencement of the Lower Cambrian Age, and as both con- 

 glomerate beds and ripple marks are met with in the Archsean 

 Group as well as in the succeeding Cambrian formation, it is 

 almost certain that a land surface existed in the neighbourhood 

 of Adelaide before the close of Pre-Cambriau time. 



These north-easterly axes of folding can be traced from near 

 Adelaide to Thackaringa and Broken Hill, though it is by no 

 means certain as yet that all the rocks folded on these axes within 

 the above limits are Archaean. 



(2) The Musgrave Ranges, which in Mount WoodrofFe attain 

 an altitude of 5,120 feet, are composed of crystalline schists, 

 gneiss and various eruptive rocks, together with considerable 

 deposits of magnetite and titaniferous iron, but it is not stated 

 by Mr. Brown | whether the last-mentioned deposits are contem- 



* Trans. Phil. Soo. Adelaide, 1878-79, pp. 76-79, pi. i.-ir. Government 

 Printer, Adelaide, 1879. 



+ Trans. Proc. and Report Roy. Soc. S. Australia, Vol. iv. (for 1880-81), 

 p. 61. Adelaide, 1882. 



X l^'outh Australia. Report on Journey from Warrina to the Musgrave 

 Ranges. H. Y. L. Brown. By authority. Adelaide, 1890. p. 2. 



