234 



tinguished geologists * who have been on the ground, and 

 their special knowledge of this department of geological 

 science confers on their opinions the greatest weight. 



From the base of the glacial till there follows, in de- 

 scending order, a thick series of quartzites, slates, phyllites, 

 and limestones, which exhibit a certain uniformity of features. 

 They are found in the country lying between the Sturt River 

 and the main heights of the Mount Lofty Ranges. The very 

 siliceous character of most of the quartzites confers on them 

 great resistance to waste, with the result that they develop 

 prominent ridges, forming the principal heights, and make 

 precipitous cliffs and waterfalls in the lateral gullies. The 

 associated slates give feature to the foot-hills and lesser heights 

 by rounded summits and a rich verdure which springs from 

 their productive soils. 



The series is conformable, and with strong resemblances 

 throughout, but for convenience of treatment it may be con- 

 sidered imder the following sections : — fa ) The Upper 

 Quartzites (Mitcham and Glen Osmond beds) : fh ) the Thick 

 rGlen Osmond) Slate : fr) the Middle or Thick Quartzite : frl) 

 the Phyllites and Lower Limestone: ff') the Basal Grits and 

 Conglomerates. 



III. — Upper Quartzites (Mitcham and Glen Osmond 



Beds). 



The junction of the till beds with the underlying quartz- 

 ites can be conveniently stiidied in the Sturt Valley (Section 

 22, Hundred of Adelaide), and in the railway cutting near 

 the Blackwood Metropolitan Brickworks. A good section is 

 also visible in the Onkaparinga (Section 858, TTundred of 

 Willunga). The beds immediately beneath the till are lami- 

 nated and wavy in structure, and usually strongly flexured 

 and contorted. They stand at a high angle, and, in places, 

 override the till beds along its eastern margin ; whilst the 

 till beds override the superior Tapley's Hill slates on the 

 Onkaparinga. 



The Upper Q^^artzites, of which there are several dis- 

 tinct beds, outcrop along the foot-hills at Glen Osmond, Mit- 

 cham, Belair, etc.. They have been extensively quarried 

 throughout the Adelaide district, and many instructive sec- 

 tions can be seen. As they are much faulted, it is difficult 

 to establish a clear correlation of the disjointed members of 

 the series, but the main quartzite, worked at Glen Osmond 



* See refei-ences, ante, under the names of Professor T. W. 

 E. David, Profes.sor J. W. Qrefroty, Mr. E. F. Pittnian, and 

 otl)ors. 



