548 



kneaded rock, chiefly of a slaty character, the exact strati- 

 graphical position of which is doubtful. As the main 

 quartzite of the mount dips westerly the slates that appear 

 immediately on its eastern side should be the equivalents of 

 the slates that, in the neighbourhood of Adelaide, occupy 

 the intermediate position between the quartzite that underlies 

 the tillite on the one side, and the Mitcham and Glen Osmond 

 quartzite on the other. This view is supported by the fact 

 that in some cases noted the slates exhibited a closer litho- 

 logical resemblance to the slates of that horizon than those 

 which occur higher in the series. There is, however, a 

 possibility that some of the broken-up slates may have been 

 derived from the Tapley Hill series which follows, in a naturally 

 descending order, the limestones that outcrop on the adjacent 

 foot hills. The stratigraphical relationship of these broken-up 

 slates to the main quartzite can be best seen in the section 

 exposed in the Cathedral-rock Creek. 



2. The Matn Quartzite. 



The backbone of the mount consists of quartzite, some- 

 what flaggy, and in places carries dark lines, apparently from 

 the presence of granular, clastic ilmenite, the planes of depo- 

 sition often showing current-bedding. The summit of the 

 mount takes the form of a somewhat narrow ridge, from which 

 it is sometimes possible to see the water of the Gulf on one 

 side and the Willochra plains on the other. The mount, in 

 its general outline, converges at both its northern and 

 southern ends, and is widest in a transverse section passing 

 through its highest point from east to west. A similar 

 feature is shown by the quartzite outcrops, the latter being 

 narrowed at either extremity but widening at the greatest 

 transverse diameter of the mount, where they show a width 

 across the strike of about a mile in horizontal measurement. 



The strike of the beds is maintained more or less in the 

 direction of the longer axis of the mount, and the dip, which 

 is westerly, gradually increases in pitch across the strike from 

 west to east. 



In places the rock makes sheer faces of great height. 

 At the northern end of the mount broken quartzite occupies 

 most of the slopes, and on the north-western portion the road 

 has been cut into the quartzite for a length of 69 yards. The 

 stone carries nne-orained clastic felspar, with occasional dark 

 lines on the bedding-planes, and dips W. 20° N. at 50°. 



The "Cathedral rocks," situated about one mile and a 

 half from Melrose, make a very bold feature on the eastern 

 side of the mount. A sheer face of quartzite, about 200 feet 

 in height, reaches to a shelf from which another pinnacle 



