﻿Vol, 64.] GLACIAL BEDS OF CAMBRIAN AGE IN SOUTH AUSTRALIA. 253 



{c) Appila-Gorge Section. (Figs. 4 & 10, pp. 244 & 254.) 



• The Appila Creek takes its rise at Tarcowie, and, after a course of 

 24 miles, finds its outlet by marshy flats into the Ilocky River near 

 Laura, which is distant 86 miles by rail north of Adelaide. About 

 5 miles from its source the creek turns abruptly westwards, cutting 

 a gorge through a low range of hills which have a north-and-south 

 direction. The gorge is about half a mile long, and for about 

 three-fourths of this distance it is cut through glacial beds. For the 

 greater part, the river cuts the beds withiu a few degrees of a true 

 cross-section ; and in the remainder of the distance a section across 

 the strike can be continued, by following a small tributary which 

 comes in at the angle of the stream. 



The strata throughout are at a high angle of dip, for the most part 

 varying from 85° to 90° eastwards ; and they present, therefore, 

 very favourable conditions for calculating the thickness of the beds. 



The boundaries of the glacial beds are strongly marked, both at 

 their lower and at their upper horizons. Immediately below are 

 massive quartzites, which, from their superior hardness and nearly- 

 vertical position, weather into great rampart-like ridges. These beds 

 are the equivalent of the Mitcham Quartzites, which occupy a similar 

 position in the section near Adelaide. The upper boundary of the 

 glacial beds is marked by a sharp line of division, in which boulder- 

 clay with big erratics is covered by a homogeneous fissile slate or 

 shale : this is the equivalent of the Tapley's-Hill ribbon-slate, but 

 splits more readily along the bedding-planes than the latter does. 



A rough measurement of the glacial series in this section gives a 

 total thickness of 1526 feet, which is split up into three sub- 

 sections : — (a) An upper till of 120 feet ; (h) an interbedded series 

 of slates to 656 feet ; and (c) a lower till of 750 feet. The following 

 is a detailed description of the section (see fig. 10, p. 254) : — 



Overlying Beds : Laminated aud banded slates, dipping eastwards 

 at 80^ to 90° (= Tapley's-Hill Slates). 



Glacial. Thickness in feet. 



a= Upper till, with numerous erratics, some glaciated 120 



b= Slates, with few or no erratics 480 



c= Quartzites and slates, alternating in beds about 3|- feet thick, 18 

 d= Slates, with wavy structure, which gradually become calcareous 



towards their base 60 



e= Thin, impure, buff-coloured limestones (in bands from 



1 to 9 inches thick), separated by partings 18. 



/= The above pass down into more definite limestones, which in- 

 clude an erratic of micaceous gneiss, 9 inches long 12 



g= Quartzite, including a slate-band of 6 inches 27 



rSlate ISfeet] 



h= < Band of slate with small erratics ... 1 foot > 20 



[Slate 6feetJ 



i= Bluish limestone, in wavy bands about 1 inch thick 3 



;■= Quartzite 18 



k= Lower till, with numerous erratics, some glaciated 750 



Underlying Beds: Massive quartzites, passing down into — ~ 

 siliceous slates and thin bands of quartzite. Dip E. 20° S. at ^^^^ 

 80°. (--=Mitcham Quartzites.) 



