248 



tions Nos. 5604, 5607, 5546, and 5517. It outcrops in the 

 vineyards of Highercombe, and can be traced up the side of 

 the hill towards the house; but it disappears before reaching 

 the latter. It is probably thrown down by a fault, as the 

 limestone was penetrated when sinking a well in Highercombe 

 House at a depth of 80 feet. On its western side the lime- 

 stone is here bounded by quartzite ; and on its eastern sid6 

 the Pre-Cambrian beds, in a high and rocky ridge, form a 

 continuous outcrop from the River Torrens to Houghton and 

 beyond. 



Other Localities for the Lower Limestone. — In the- 

 Onkaparinga, a little below Hack's Bridge, where the beds 

 consist mainly of white marble, and are much obscured by the 

 alluvial of the stream. This outcrop is at no great distance 

 from the basal grits. 



At Mount Bold, in the valley of the Onkaparinga, a blue 

 siliceous limestone outcrops on the east side of the Mount, and 

 a more extensive outcrop of limestone occupies the summit of 

 a minor elevation (Section 295, Hundred of Noarlunga), 

 about half a mile north-Avest of Mount Bold, and has been- 

 used to construct the ford of the river on the Clarendon 

 Road. The stone apparently dips S.S.W. at 15°. I cannot 

 definitely place this limestone, as it is a few years since I 

 visited the locality, but it is probably the lower limestone. 



On the South Para there is an outcrop of the same lime- 

 stone series, which can be traced for a long distance on the 

 north side of the river, and is closely associated with the basal 

 beds, which rest on Pre-Cambrian gneiss. 



Absence of these Limestones at Mount Lofty. — In 

 the consecutive order of the lower Cambrian beds this im- 

 portant limestone series ought to outcrop on the east side of 

 Mount Lofty, between that eminence and the Aldgate grits. 

 No such outcrop, however, occurs. The absence of these beds 

 must be referred to a strike fault of some magnitude, which 

 has prevented the limestone from showing at the surface. 

 This effect might be brought about in several ways. Two 

 examples are shown on Plate xii., figs. 2 and 3. 



In fig. 2 the beds are throvrn down in two parallel trough 

 faults, which obscure the limestone, and cause a repetition 

 of some of the higher beds at the surface. The limestone is 

 shown as faulted ap-ainst the Pre-Cambrian beds at depth. 



In fig. 3 a fault is shown which hades in the direction 

 of the dip. This would have tlie effect of cutting off some 

 beds and preventing their coming to the surface. I think 

 the section shown in fig. 2 is the more likely occurrence of 

 the two. and this is supported by some local features, which 



