241 



underlying harder beds. The general trend of these lime- 

 stone outcrops is along the western slopes of the foot-hills, and 

 separately, curving upwards in an easterly direction towards 

 the rise, die out before reaching the summit. 



VI. — Small Dolomitic Limestone. 



At a lower horizon in the thick (Glen Osmond) slates 

 than that occupied by the '"blue metal" limestone, a small, 

 buff-coloured dolomitic limestone occurs. It does not appear 

 to exceed from a few inches up to a foot in thickness, and 

 from its thinness is often only indicated by loose fragments 

 and travertine cover. It is associated with a fine-grained, 

 laminated quartzite, which weathers smooth and of a buff 

 colour, and carries a close superficial resemblance to a dolo- 

 mitic limestone. Irdeed, some specimens give a slight re- 

 action for calcium-magnesium carbonate. It has a distinct 

 outcrop, about a foot thick, on the west side of Waterfall 

 Gully (high up) ; also at some old mine workings on the same 

 side, but at a lower level. It has also been noted at Brown- 

 hill Creek, above Mitcham ; on the north-east side of Green- 

 hill road, where it is associated with lumps of magnesite or 

 dolomitic travertine; on tne spur between the Third Creek 

 and Horsnell's Gully ; and probably on the hillside, near the 

 by-road, south of Fifth Creek, where a piece of dolomitic lime- 

 stone was found in the surface travertine associated with the 

 buff-coloured laminated quartzite, which usually accompanies 

 this bed. A thin dolomitic limestone was found crushed in a 

 fault plane, on the hill south of the Torrens Gorge, where it 

 is associated with much quartz and chlorite. 



VII.— The Thick Quartzite. 



Anstey's Hill, the Black Hill, Stonyfell, and Mount 

 Lofty form the most conspicuous eminences of the Mount 

 Lofty Ranges, as seen from Adelaide. They have much in 

 common. They each consist of quartzites of great thickness 

 (probably not less than 1,000 feet), whilst a similar geological 

 character has given rise in each case to a scrubbv vegetation 

 that clearly defines them in the landscape. In structure, the 

 quartzite is seldom massive, but is divided up into relatively 

 thin layers of solid stone, separated by partings of shale or 

 mylonitic material. The composition of the stone is that of 

 a clastic rock, consisting, in the main, of rounded quartz and 

 felspar grains, similar to the other quartzites of the series. 

 From the features which these several outcrops have in com- 

 mon, as well as other considerations which will a]3pear in the 

 sequel, it is believed that thev represent the same geolosfica? 

 horizon, although thev form disconnected fragments. 



