﻿Tol. 64.] CAMBRIAN AGE IN SOUTH AUSTRALIA. 251 



and passing the remainder through a powerful mill) is utilized for 

 brick-making. 



The glacial outcrop, in this instance, measures 2 miles in its 

 north-and-south direction and a mile and a half in width. Its 

 northern extension is limited by a fault which throws the under- 

 lying beds across the normal strike ; and, on the south, the beds are 

 obscured by overlying Miocene sandstones and gravels. In their 

 upper limits, the glacial beds vary in dip from 35° to 50° south-west- 

 ward ; but at their base a reversed fold has thrown the underlying 

 laminated quartzites on to the till with a dip to E. 20° S., at 70°. 

 (See Pi. XXVI.) 



In an unstratified bed of great thickness, as is the case in this 

 and other sections of the Cambrian till of South Australia, it is a 

 difficult matter to estimate the thickness with accuracy, more 

 especially as the strongly-marked cleavage obscures the folding to 

 which the beds may have been subjected : therefore, in the following 

 section of the Sturt-Yalley beds, the figures in relation to the thick 

 till must be taken as approximate only. (See fig. 8, p. 250.) 



Overlying Beds. 

 Tapley's-Hill laminated and banded slates, with about 4 feet of im- 

 pure dolomitic limestone at their base, resting immediately upon 

 characteristic till. 



Glacial. Thickness m feet. 



«=iHighe8t till-bed, with numerous erratics 45 



6=Grits and till, intimately mixed in irregular patches 12 



c=:Black slaty till, calcareous in places and carrying a few erratics. 14 



t?=Blue limestone, on top of grits, very local in occurrence 2 



e=Strong grits, fine to coarse and in places including pockets of 

 stones. They are somewhat irregular in occurrence, and develop 



prismatic jointmg 10 



/=Thick till, sometimes slaty and in places becoming a distinct grit ; 

 but it is characteristically a gritty mudstone, with numerous erratics 

 of foreign origin measuring up to 4^ feet in length. Cleavage-strike 



N. 15° E. to N. 20° E., at 60° to 70° easterly (?)600 



y=Yellow and buif decomposed kaolinized slates, without 

 stones, and very fine-grained. They include a band of contorted 



quartzite, about 3 feet thick 72 



A=Bottom till, with erratics 40 



795 

 Underlying Beds. *"~~ 



Finely-laminated quartzites and arenaceous slates, sharply defined in 

 junction with the overlying till ; dip E. 10° N. at 70°. Can be well 

 seen in the bed of the Sturt River, and in railway-cuttings near 

 the Metropolitan Brick-Works, where the fine lamination shows the 

 minute and excessive contortion attendant on the reversed fold, in 

 a very high degree. 



The precipitous sides of the Sturt Gorge are unfavourable for the 

 collection of glaciated stones; but several very characteristic 

 examples of glaciation have been secured in the pits of the Metro- 

 politan Brick Company. 



