246 



quartz and chlorite, in their origin, is proved by the inclu- 

 sion of granular chlorite within the crystals of quartz. 



Phyllites also occur extensively in the Onkaparinga River, 

 about Clarendon ; in the Little Para River, and tlie South and 

 North Para Rivers. 



Interbedded with the lower phyllites are quartzites and 

 limestones. The latter are of great stratigraphical value in 

 determining the geological horizon of the lower members of 

 the Cambrian series. 



Tlte Jjower (or liivtr Torrmii) Limestonf. — Towards the 

 lower j^art of the phyllite-quartzite series (which underlies 

 the thick quartzite of the Black Hill, Mount Lofty, etc.), is 

 an important developnient of limestone. The main bed varies 

 from a blue or buff-coloured limestone to a white crystalline 

 marble. It is frequently dolomitic, aud in places becomes a 

 true dolomite. The designation 'lower limestone" distin- 

 guishes it from the Brighton and Reynella limestone, which 

 occupies a much higher geological horizon : and as it is typi- 

 cally seen in the valley of the Torrens and its tributaries, it 

 may be called the 'Torrens limestone." 



The limestone proper is associated with impure calcareous 

 beds and quartzites, whilst the much faulted and broken condi- 

 tion of the beds makes it somewhat difficult to state their 

 exact sequence, but the following appears to be the order in 

 descent : — 



( (t ) Overlying (rather thick) quartzite. 



(h) Impure siliceous blue limestone. , 



( c) Calcareous quartzite. Weathers with quartz grains on 



surface of stone. 



(d) Quartzite. About 50 feet thick. 



( e ) Slate. Calcareous near bottom. About 60 feet thick. 



( f) Buff-coloured dolomitic limestone, or marble, with 



one or two earthy beds (not exceeding 2 feet), in- 

 terbedded with the limestone. About 150 feet 

 thick. 



(g) Phyllites and quartzite. 



Taking the limestone beds as a whole, for general descrip- 

 tion, the following localities have been noted : — It forms a 

 rounded hill at Montacute, on the I'idge behind the church. 

 It crosses the new and old Corkscrew Roads, where it is appar- 

 ently faulted with a throw to the west. In one direction 

 (going east) it can be followed down to the Corkscrew Valley, 

 and skirting the hillside (going east) it crosses a small creek 

 at the back of Mr. Barnet's house; then, passing over the next 



