126 
Rex T. Prideh. 
Tlie examijKition of the surface textures Indicates that the fine sand 
grains of the ferruginous sandstone show no appi’eciable frosting. In tlu^ 
yellow sands on the other hand frosting is coininou down to grains Vi 
diameter. IVforeover all the yelloAr sands exhibit similar features so far as 
the surfaces of the grains ai'(' concerned, the proportion of rounded grains 
and the degree of frosting of such grains increasing with increasing’ grain 
size. ! ) 
The ycno\^■ colour of the sands is due to a very small amount of iron. 
When the yellow sand is lieated it changes to a brick red colour. Deter- 
minations of the iron content res]Jonsible for the yellow colouration of the 
Crawl(‘y and Kidga' flill sands Avere made by first removing the magnetic 
minerals (magnetite and ilmenite) and leaching the residue Avitli warm 
ItCl and determining the iron conteiit of the material leached oiit. The 
results Avere as follows: — 
Yellow sand, CraAvley (22801) : 0.80% Fe.O,. 
Yellow sand, Ridge Hill (218(H); 0.48% FeA- 
From the above considerations of mechanical composition, heaA’v 
minerals, shape ami surface texture of grains, the ferruginous sandstones, 
in view of the absence of frosted surfaces on the fine sand grains and tbe 
presence of tbe tuberose alloplianoid, together Avitb the different size distri- 
bution of the heavy minerals and the better grading than the yelloAA' sands, 
must be regarded as diftVring in mode and time of origin from the uncon- 
solidated sands. Theii* T)r(>venance however (as evidenced by the heavy 
mineral sfK'cies) was similar to that of th(‘ yelloAv sands. In all Avays 
excejit in their higher heavy mineral content the yellow sands of Ridge 
Hill are similar to the only examined sample of yelloAV sand from tlie 
IVretrojiolitan Area and each of these must, until further evidence to the 
contrary he lu'ougbt foi'ward, be regarded ns belonging to the same forma- 
tion. Tin* ju’esence of frosting* on grains less tlian one mni. diameter 
(grains down to ^ j mm. are frosted) is indicatiAu*’ of aeolian transporta- 
tion (Twenhofel, 1948, p. (i"). The yelloAv sands of the AFetropolitan Area 
have not previously lieeii examined in detail although Essou (192G, p. 14) 
suggests that th(*y are dune sands. It may rather ].k‘ tliat they are resi- 
duals from the disintegration of the Coastal Limestones. Pending further 
investigation il is im])ossilTle to say whether the yellow sands of Ridge 
Hill are sands blown from the sea bcuich and bankcal up vUgaiust the 
Darling Scarp oi* are residual deposits from the Coastal Limestones (in 
Avhich tlie sand grains may prove to haAX^ sul'fenMl aeolian transport). 
Th(‘ complete absema* of bedded and otlno* structures in these yellow sands 
seems to indicate the latter. The observation that the Ridge Hill sands 
have a much higher heavy mineral cont<*nl than the yellow sands of the 
l\Ietro])olit;ui Area also seems to indicate that tin* sands fronting the 
scarp are resiflual rather than sands blown from the west, in AA’hicli ease 
they would be expected to liave a lower heavy mineral index than the 
sands of the "Melropolitan Area. If the Ridge Hill sand be residual from 
the Coasal lamestone Series il means that the Coastal Limestone once 
covered the entire [>laiu in this I'egion or that there were belts of coastal 
limestone representing successive shore lines. 
