227 



THE GEOLOGY OF THE MOUNT LOFTY RANGES. -PART II 



(the lower and basal beds of the CAMBRIAN.) 



By Walter Howchin, F.G.S., Lecturer iii Geology and 

 Pal£eontology in tlie University of Adelaide. 



[Read July 10, 1906.] 

 Plate XII. 



Contents. Page. 



T. liitroduction ... .- ••• ••■ •• 227 



11. Cambrian Cxlaoial Till 228 



IIT. Upper Qiiartzites (Mitcham and Glen 



Osmond Beds) 234 



IV. The Thick Shite (Glen Osmond Slate) ... 23o 



V. •Bhie-metal" Limestone ... ... . 237 



VI. Small Dolomitic Limestone ..- ••• ••• 241 



VII. The Thick Quartzite 241 



VITI. The Phyllites and Lower Limestone (Hiver 



Torrens Limestone) ... ... 245 



IX. Basal Beds of the Cambrian Series ( Basal 



Grits and Conglomerates) ... ... ... 249 



X. Pre-Cambrian Complex (Archtean) ... 257 



XI. General Considerations ... .- ••• 260 



I. — Introduction. 

 In a previous paper which 1 had the honour of placing 

 before the Society ''^ the geology of the maritime district bor- 

 dering the Mount Lofty Ranges was described. The area in- 

 cluded the older rocks of the eastern side of Gulf St. Vincent, 

 and inland to Tapley's Hill ; the. western banks of the River 

 Sturt, and the lower Onkaparinga Valley. The beds which 

 came under notice in that communication were considered in 

 the three following divisions : — 



(a) A very thick series of jjurple slates, '^uartzites, and 

 limestones, which form the upper members of the Cam- 

 brian beds, and are mainly covered, in the southern parts 

 of South Australia, by the waters of Gulf St. Vincent, but 

 are extensively developed in the Flinders Ranges. Some of 

 the limestones of this series contain Archccocyathino. Oho- 

 lella, and other charact-eristic Cambrian fossils. 



(h) A calcareous .series which immediately underlie the 

 purple slates. Strong oolitic limestones occur near the top, 

 but pass down into siliceo-calcareous slates, that gradually 



* Trans. Rov. Soc. (S. .\n<s.), vol. xxviii. (1904), p. 253. 

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