The Geology and Physioghaphy or the Lawnswood Area. 
73 
5. In Lato Pra-Cambrian ( Xullaii'ine) oi' T.o\v(‘l‘ ('ainbrian time (24), 
after considerable erosion had taken place, <|uart/ dolerite dykes were in- 
truded alon^' liiu'S of weakness jiossibly caused by mild diastropbism. 
The cataclasis noted in some of the granitic gneisses and (juartz veins 
and the e])idotisation of country along veins emanating from the dykes may 
have occurred at this stage. 
(). A long ])eriod of (‘rosion followed, culminating in a jumeplain on 
which residual laterite deposits were formed in Pliocene (20, p. 17, 32, 
]). 125) or Plioccme times. There was ])robably a moderate to liigh rainfall 
at the time of formathju of the latente (20, p. 47, 20, p. 10). 
7. A n(*w cycle of erosioji was initiated l)y the epeirogenic u[)lift of 
the ancient peneplain to form the Great Plateau of Western Australia 
in Pliocene and Pleistocene times (8, ]). 288). The area is now a dissected 
2 -)lateau with lalerite-ca[>ped mesas and buttc'i j'e])resenting residuals of 
the old peneplain, above which project ridges of more resistant tjuartzites. 
Vn. A(4 aXOW!.EI)G5LEXT. 
T wish to ex[)ress my deepest thaidxs to Professor E. de G. (4arke 
for liis many luOpful sugg(‘stions and discussions during the preparation 
and revision of tins pa])er. 
I also wish to thank Dr. li. T. Prider for his very great help in the 
field, in llu' practical work, and for his advice in the ])reparalion of the 
text. 
Tin* mapping of the area d(‘sci'ibed was done* in the cenu'se of fic'ld 
instrmdion (dass(*s, by [)ai'lies of -<<‘ 1001 * geology sludenls of the 1 niversity 
■of Westeiai Australia in IDoi) ami P)45. i\Iany of the thin sections used 
ill t!u‘ preparation of this })aper were cut by these students. The author 
tiesires to express his gratefulness for this assistance. 
l.IST OF hFFEHEXOKS. 
1. A Ideniiaii. A. Ih, 1942. ‘ ‘ Silliinaiiite, Kyaiiite ami Olay Deposits near Willia ms- 
town, 8outIi Australia.’’ Trdiis, Hay. -S'oe. *S'. A/os-/., A'^ul. (ifi (1), p]>. 3-14. 
2. Balk, Ji., 11)37, “ structural Heluiviour of Igneous Bocks.” Geol. Hoc. America, 
^^cm. o. 
3. P.astin, E. S., 199!), ^Chemical C'oinpositiou as a Criterion in Identifying 
-Metainorpliosed Rodinients. ” Jr»()'n. Gaol., Vol. 17, pp. 445-472. 
4. Bucher. W. IF., 1933, “Tlie Deforinalion of the Earth’s Crust. An inductive 
approach to the prohlenis of Diastroidiisin. ” Prineetowu University Press, 
Priucctown. 
5. Canavou, P.. and Edwards, A. B., l!)3s, ^'The Tron Ores of Vniupi Hound, 
Western Australia.” Proc. AkhI. Tns‘f. Min. & Met., XS. Xo. 100. 
13. Clarke, E. dc C., 1930, “The J’rc-Camhrian Succession in Some Parts of 
Westei’ii Australia.” IGjA. Au-sl. A^s.ioc. AAv. He. for J03t>, ])p, 15.)-192. 
7. Clarke, E. de 193S, “Middle and Western Australia.” Bd. 1 VII of 
lieg. Gr<d. dcr Krdc, Alad. Vnlag. (Leijizlg). 
8. Clarke. E. de C., Prider. H. T., and Teichert, C’., 1944, “ Elements of Geology for 
Western Australian Shidents.” (Cniv. of AV.A. Text Books Board, Perth.) 
9. (k>le, W. F.. and Gloe, C. S., 1919, “The Getilogy and Physiography of the 
Malkup Area.” Journ. Hoy. Hoc. W. Aast., Vol. XXVI, pp. 139-171. 
