Thk Geology of the Darling Scarp at Ridge Hill. 
119 
lo about 12 foot. Downstream from this point the gulley continues as. a 
narrow Avashout four feet wide by 12 feet deep which is roofed by the 
roots of the adjacent jarrali trees (text tig*. 4). 
Text tig. 4. — Washout in yellow sand, seven eliai)is south-weat from the H-niile 
railway peg. The very recent develojnnent of this feature is evident from 
the uncovered roots of the nc^arhy Jarrnh trees. 
The yelloAV sand profile exposed consists of 12 to IS inches of light grey 
:sand Avith plant roots, the remaimler of the profile consisting entirely of 
yelloAv sand in whicli there is absolutely no sign of bedded structure, the 
whole ])rofile consisting of sand of uniform texture from top to bottom of 
the exposed section. Throughout the sand at intervals of several inches 
-are small nodules of more compact material averaging Va inch diameter 
Avhich project from the vertical sand face. These nodules which can be cut 
through Avith a knife consist of the sand Aveakly cemented Avith reddish iron 
oxide. On cutting a fresh surface Avith a hatchet they ai)j)ear only as red- 
dish iron-stained spots with a gradual transition lo the yelloAV saml. It is 
only Avhere they have been exijosed to the atmos))heve on the Avails that a 
^liglitly hardened surface has been formed on them. At the bottom of the 
section exposed in tin' Avashed out drain the sand contains an abundance of 
these nodules, in some (>laccs aggregated to nodules several inches in 
diameter. These larger aggregates are weakly cemented and can be broken 
across with the liiigoi's. Tliey contain a higher proportion of fine-grained, 
light broAvnish to greyish clayey material. TIk'v appear to have been enriched 
in alumina AA’ilh respect lo the suirounding sand and if this material AAdiieh 
in places Avas slightl\- damp were desiccated it Avould he similar to non-con- 
cretioiiary laterite. It Avould appear then that Avith the development of 
these aluminous nodules at the base of the ex])osed ]u*ofile aud of the small 
iron-stained jjatclies throughout the mass of the sand incipient lateritisation 
is taking place Avithin this sand deposit. 
