The Geology and Physiography of the Lawnswood Area. 
49 
2.— THE GEOLOGY AND PHYSIOGRAPHY OF THE 
LAWNSWOOD AREA 
By 
J. R. H. McWhae, B.Sc. (Hons.). 
I. 
Read : 12th March, 1940, 
CONTENTS. 
Introduction 
Page 
... 49 
11. 
Physiography 
... 50 
III. 
Geology 
A. Occurrence of the rocks 
... 51 
B. Structural interpretation of the Jimperding Series 
... 54 
IV. 
Petrology 
A. The Jimperding Series 
55 
1. Metasediments 
(a) Quartzites ... 
... 55 
(b) Mica schists 
... 50 
(c) Metajaspilites 
... 58 
2. Meta-igneous rocks 
(a) Hornblende schist and its variants 
... 60 
(b) Cordierite — aiithophyllite rook ... 
... 01 
3. Granitic gneiss and associated xenoliths 
(a) Upper granitic gneiss 
... 02 
(b) Xenoliths in the granitic gneiss 
... 02 
B. The younger igneous intrnsives 
1. Younger granites ... 
... 00 
2. Quartz dolerites ... 
... 70 
V. 
Economic Geology 
A. Refractories 
... 71 
B. Charcoal iron ... 
... 72 
VI. 
History of the Area ... ... 
... 72 
VIL 
Acknoi\t:>edg>ient.s 
... 73 
VIII. 
List of References ... 
... 73 
1. JXTRODI’CTIOX. 
Lawiiswood is situated on the Claekliiie-Milidu- railway, three miles north 
01 Claekliiie and approximately oO miles in au east-north-east direction from 
Perth (see locality jdan on Plate !.)■ The lanvnswood Area, which occupies 
about 10 square miles with the southern boundary less than one mile north 
of Clackline, is lar;tiely composed of early Pre-Cambrian rocks of the Jim- 
])erding Series ((>, p. 107). This s<‘ri('.s is composed {)f pelilic and p.sammitic 
metasediments with intercalated layers of acid and basic igneous j'ocks all ot 
which have sutfered silHmanite zoiu' regimial melamorphism (20, p. 11; 23. 
p- 84; 9, p. 108). Tt extends from York (15 miles south oi' ( lackline) to at 
least as far north as the Irwin Ki\er District (23, p. 84). Forman (12, p. 
XXV) regards this series as eqiiivahmt in age to th(‘ Whitestom* and AIos<iuito 
Creek Series, Avhich, as indicated l)y recent work at Southern Cross (10, p. 
13), are younger than the Oldei* Ort'enstoru's of the Ixalgoorlie Series (con- 
sirlere<l to be the oldest grou]) of rocks in Westc'rn Australia (24). 
The other rocks of more limited disti'ibiition ar(' Late Ar<*haeozoic 
Younger Granite (12, )>. XXV), Late Proterozoic or Lower (kimbrian quartz 
dolerite dykes (24) and a superficial dejiosit of Tertiary laterite. This 
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