Hex T. Prider. 
found which in any way favours a pro-gTanite age for the Cardup 
Series, lies in the pi'estuna* in th(‘ slates of small amounts of idiohlastic 
tourmalijie, which as described al)ov<*, may equally well be ex])Iained as due 
to crystallisation of components of the original sediment during the earth 
movements whi('h tilted the Cardui> Series. 
The position of the Cardup Series in the Pre-Cambrian succession of 
Western Australia (as deduced from all the evidence* available in this area) 
is therefort* later than the tinal granite intrusions and earlier than the basic 
igneous inti’usions of the Xullagine period (late ifre-Cambi'ian ). I have 
re<iently had (X'casion to examine a collection of I'ocks from the Stirling 
Pango S(‘ries and from the evidence at present available these rocks appear 
to belong U) tin* sanu* period as the Cardup Series — the field relations of 
the Stirling Range Series have been investigated by Professor E. de C. 
Clarke and further <letails regarding these rocks will be given in a future 
paper. 
(b) The Darltufj ^‘FauU-’ Senrp, 
The area descrilaxl above iTicludes one of the numerous fiat spurs which 
extend out IVom the present line of the scarp. If the Darling Scarj) is a 
fault scarp then the fault should lie situated somewhere in the vicinity of 
the tip of these projecting spurs. Movements of tin* magnitude required 
to produce a downthrow' to the west of several thousaTids of feet (as re- 
quired to ex])Iain the structure of the coastal i^lain) should surely be 
reflected in the comparatively weak slat(*s forming these si)urs. Obser- 
vation of all the minor structures in tin* slates of the Aianadale area indi- 
cates in eve?‘y instance, that the western side has been i)Ushed up and over 
th<* rocks lying to the east and ajjpears to lu'gative the [)ossibility of any 
lai'ge faults with a downthrow to the west in the vicinity. The structures 
are consist(*nt with an extensi\'e downwarp to the west involving m tilting 
of th(* Cardup S('i'ies to the west and minor iipihrusting along the eastei’n 
margin of the downwarj). If this he tlie case (and it will only ])e proved 
or disproved by close investigation of the structmx's in tin* Cardup Series 
all along the face* ol' the scarp) then the* Darling Scar]), Avhich is one of the 
most pronounced i)hysiographie features of south-west(*rn Australia, must 
he* an ere)sion feature* due to diffei’ential (‘rosion of a monoclinal fold imther 
than a fault stj’ucture*. 
(e) The Geological Ilistorg of the Area. 
The geological history of the area, from the evidence presented in the 
foregoing i»age>s, may he summarised as follow's: — 
1. Period of granitisation during w'hich ])re-existing basic I'ocks were 
permeated by granitic e*manalions and the hyl)rid gneisses pro- 
duced. 
2. Perioel e)f granite intrusion (aplogranite), 
d. Eai'th movements, causing development of shear zones and joint 
]>attern in the granitic gneisses, follow'ed by the formation of the 
quartz veins in the gneisses. 
4. Deposition of the (birdu]) s(*diments. 
5. Formation of an (*xteiisive downwai’p parallel to the present Darling 
Scar}.) and some distance to Ihe west, involving upthrusting along 
the eastern margin, development of fracture cleavage in the slates 
and tilting of the sediments to the west. 
6. Intrusion of alhite epidiorite sill into Cardup Series, probably con- 
temporaneous w'ith (5). 
