The (ih:oLOGY and Physiochiaphy of the W'^ngong-Cardup Area. 279 
On the .slo})es below the Interiie, frag'nicnts of a dark-red fine-grained 
limonite rock are found in a few restricted areas. Thin section lana^aJs a 
fine-grained inati'ix of limonite with a small amount of interstitial (jiiartz. 
This rock may be e(iuivalent to the ferruginous grit found below the laterite 
of other Darling Range areas (Miles, 1938, p. 32). 
On the lower levels laterite occurs as boulders of the ]>isolitic variety 
or as unconsolidated deposits of limonite pebbles with sand or ferruginous 
clay. 
2. AUtivi'um . — The alhnium in the Wongong Brook is sandy. At the 
bend west of the gorge, large l)oulders of conglomeratic rock lie in the aban- 
doned stream bed. This rock contains pebbles and boulders of granite and 
gneiss Avhich have been ceuumled by clay, in the banks of the stream. 
V. CONCLUSIONS. 
A. Af/e of the Cardup Series wfid its relation to the (jranifie rock's. 
The structure of tlie gtUMss can be broadly interprded as due to folding 
which took j)laee before Ihe formation of tlu* Cardu[> Series. Further facts 
similar to those recorded by Prider (1941) support the conclusion that Ihe 
gneiss and granile are older lhan the Cardnp Series. They are 
(i) No (|uart-/ or pegmalitt* veins have been obsen'ed to pass from 
the granile and gneiss into the (hualup Series. 
(ii) The Cardup Series maintains a normal (U’osion sequence and the 
basal lieds must rest iqjon the eroded grnnit(^ gneisses Avhich strike obliquely 
to th(^ Cardup Series. 
(iii) Xenoliths of the sediments are alisent from the gneiss. 
(iv) The gneiss does not vary in character across the strike and therefore 
does not appear to be a granitised ])hase of the Cardup Series. 
(v) Contact metamorjihic effects in the sedinunts are slight and are due 
to basic intrusions. 
(\i) The wides]Ar(‘ad occurrence of small idioblastic crystals of tour- 
maline in t he slates can be readily attributcal to original Iioron in the sediments 
rather than to pneumatolytic elfects of a granite intrusion. 
(vii) Hounded zircons are found in the basal sandy beds of the sedi- 
ments, whereas mim‘ralogi('alIy similar zircons occurring in the gneiss and 
basic xenoliths are unrounded. 'This points to the possible derivation of the 
Cardup Series (in part at least) from the gneiss. 
(viii) Detrital microcline, most reasonably regardt'd as derived from the 
aplogranites and gneisses, occurs in the Cardup sediments. 
B. Dorlhig Scar}). 
Prider, (1941), considered that ihe Darling Scarp was produced by the 
differential erosion ol‘ a monoclinal fold, and Avas not luamarily a fault 
structure as has been suggested by most geologist-s (Jutsoii. 1934, p. 87). 
He based his conclusions on the minor structures in the slates at Armadale, 
AA'hich indicate an upflirnst from the Avest, the result of a dowinvarp of 
sediments to the west of the area. In the Wongong-Cardu]> area, similar 
structures are found in the slates of the State Brickworks Quarry. It is true 
that at Cardup, slate further Avest of the granite gneiss Cardup Series contact 
dips almost vertically Avhieh is hard to reconcile Avith the u])thrust, but this 
steepening of dip may be attril)uted to the deformation produced by the 
nearby basic dykes. 
