JOURNAL OF

THE ROYAL SOCIETY

OF

WESTERN AUSTRALIA

INCORPORATED

VOLUME 42 (1959)
PART 1

PUBLISHED 19TH MARCH, 1959

REGISTERED AT THE G.P.O., PERTH FOR TRANSMISSION BY POST AS A PERIODICAL

THE

ROYAL SOCIETY

OP

WESTERN AUSTRALIA

INCORPORATED

COUNCIL 1958-1959

President

Past President ....

Vice-Presidents

Joint Hon. Secretaries

Hon. Treasurer
Hon. Librarian
Hon. Editor
Hon. Assistant Editor

E. P. Hodgkin, D.Sc., F.R.E.S.

A. J. Millington, D.Sc. (Agric.).

R. T. Prider, B.Sc., Ph.D., M.Aust.I.M.M.,

F.G.S.

N. H. Brittan, B.Sc., Ph.D.

D. P. Drover, B.Sc., Ph.D.

L. E. Koch, B.Sc.

R. D. Royce, B.Sc. (Agric.)

G. G. Smith, M.Sc.

J. E. Glover, B.Sc., Ph.D.

K. Sheard, D.Sc.

Alison M. Baird, M.Sc.

C. F. H. Jenkins M.A.

R. J. Little.

L. W. Samuel, B.Sc., Ph.D., F.R.I.C., F.R.A.C.I.
A. R. Tomlinson.

A. F. Wilson, D.Sc., F.G.S.

Journal
of the

Royal Society of Western Australia
Vol. 42 Part 1

1.— The Potential of Some Native West Australian Plants as Pasture

Species

Presidential Address, 1958

By A. J. Millington, D.Sc. (Agric.)*

Delivered 21st July, 1958

It is in the tradition of this Society that
first consideration should be given to the things
which are ours. The rocks which underlie us,
the soils which develop on those rocks, the plants
which grow on those soils and the animals
which eat those plants have been the subject of
previous Presidential addresses to this Society.
The most recent of the addresses on geology
was that of the immediate past-President, Dr.
Wilson. Professor Teakle in 1938 made the first
detailed attempt to regionalise West Australian
soils and in 1942 Mr. Gardner’s address related
the native vegetation to the soils and climate
of the State. More recently Professor Grieve
(1956) has discussed the physiology of the native
plants, particularly in respect to drought re-
sistance and Dr. White (1958) has reviewed
them as sources of drugs of economic importance.
It is their potential as forage plants that it is
proposed to examine tonight.

On maps showing the Centres of Origin of
Cultivated Plants, Australia is a conspicuous
blank. This is partly due to biological chance,
but also, and quite importantly, probably, to the
fact that the Australian native never interested
himself in agriculture. The great civilisations
of the world followed the domestication of wild
species. The Mayas in Mexico used maize, the
Incas of South America«depended on the potato,
while the civilisations of Asia including our own
and those of China and India were built upon
the use of cereals, principally wheat and rice.
By contrast, no very serious attempt was made
to use any indigenous Australian plant for
human food, although a number are probably
not inferior in productivity and nutritive value
to the wild ancestors of many species cultivated
elsewhere. In the words of Charles Darwin
“primitive man ate anything which he could
chew and swallow” and the Australian native
never rose above fern-like nardoo.

The agriculture and much of the pastoral
industry of Australia is dependent, therefore, on
the use of introduced plants, developed by older
civilisations, with no serious attempt to domesti-

* Institute of Agriculture, University of Western Aus-
tralia, Nedlands, Western Australia.

cate, or even to preserve, the indigenous flora.
Many species have become either totally or very
nearly extinct, and, unfortunately, the palatable
ones, with the greatest agricultural potential,
are those most likely to be exterminated by
rabbits and man’s grazing animals.

The position of Australian plants in relation
to extinction is not unique for it is likely that
many of the common forage plants have survived
only because recurrent wars and pestilence de-
populated at fairly frequent intervals, the
countries in which they originated. This gave
the plants opportunities to adapt themselves to
man and his grazing animals.

By contrast Australian plants have had no
such opportunities. Sheep numbers were high
sixty years ago while the modern plough and

Sheep numbers in Australia

1890 — 97 million

1940 — 125

1946 — 95

1957 — 150

the tractor have subjected plants to more
frequent and thorough cultivations than were
possible in earlier civilisations. The lesson of
evolutionary biology is that failure to compete
and adapt to changing climatic and other con-
ditions results in extinction, but practically
nowhere in the world do we find plants which
have the innate capacity for adaptation to the
cataclysmic changes which come with modern
land development. By the same token, never
before have so many tools been available to
achieve, in the words of the Russian scientist
Vavilov, “evolution by the will of man”.

The rich and unique flora of Australia appears
to be destined for extinction either by overgraz-
ing or by competition from introduced plants,
an eventuality which most Australians appear to
contemplate with complete equanimity.

Occasionally our attention' is directed to the
fame which our Eucalypts have achieved over-
seas, or, as in South Africa, a tannin bark
industry has been developed on the basis of an
Australian plant, the wattle.

1

Following its accidental introduction as an
impurity in commercial Rhodes grass seed an
Australian grass, Dicanthium sericeum syn.
Andropogon sericeus has become dominant in
parts of Texas and local ranchers are now
gathering seed for extensive plantings. This
particular grass has been “eaten out” over
extensive areas in its native habitat in Queens-
land, but research work is now being undertaken
at the Gatton Agricultural College with a view
to selecting superior strains and three have been
distributed for regional testing.

In the agricultural areas development was
dependent on introduced cereals and with the
increasing importance of pastures, it has been
the most practicable procedure to seek grazing
plants from the same source. While these plants
have evolved in areas of similar climate, they
have developed, for the most part, on soils,
which, for geological reasons, are of much higher
inherent fertility than those used for agriculture
in this continent. In Western Australia, the
lateritic soils, which cover three quarters of
the agricultural areas already developed and
characterise the ten or fifteen million acres
remaining, are extremely poorly supplied with
plant nutrients. Before introduced plants can
be grown on these soils, massive and expensive
applications of superphosphate and trace ele-
ments are required and there is evidence that
on deep sands, potash fertiliser will be required.
Within a very short space of time, decisions in
respect to considerable areas will need to be
taken as to whether they are to be worked at a
high, or a low plane, of plant nutrients. Whether
it. will be more profitable to spend heavily on
fertilisers and farm at a high level of productiv-
ity, or economise and carry many fewer sheep,
can only be determined on the basis of experi-
mental data, but there can be little doubt that
the cost of fertilisers will be of paramount
importance on the millions of acres of sandplain
soil at present in use, or about to be used, in
the more favoured rainfall areas of this State.

By contrast to the introduced legumes, the
native plants grow and thrive with little or none
of the expensive diet of nutrients applied as
fertilisers. For a State, such as Western Aus-
tralia, which has an annual fertiliser cost of at
least £10,000,000 this is of importance. To
approach the climatic potential of the State,
an annual outlay on fertilisers of twenty to
thirty million pounds will be required each year.

Any decision to develop species for economic
purposes should be made on the basis of such
data as are available from practical experience
and scientific research.

The pastoral industry depends on native plants
but overgrazing by sheep and rabbits, has greatly
reduced the carrying capacity of these regions.
This has lead to the belief, that native species
will not withstand grazing, but investigations
by the Department of Agriculture in the north
of this State have clearly demonstrated that
given relatively simple management, in the form
of deferred grazing, the native plants of these
areas can be made as productive as ever (Nunn
and Suijdendorp 1954). Where over-grazing
has proceeded to the point of extermination,

such as around watering places, there is the
opportunity to introduce superior strains of local
species.

Assuming that it appears to be worthwhile to
consider the problems likely to be encountered
in domestication they can be summarised as
(i) collection, classification, crossbreeding and
selection, (ii) small scale trials to make a first
assessment of the agronomic potential of the
various strains and species, (iii) seed increase
with its associated problem of seed gathering
and (iv) controlled large scale trials under
practical conditions with the most promising
types. A reasonable approach could be made at
a level of annual expenditure of £30,000-£50,000
per annum over a period of 10-20 years, or a
total, at its highest level of annual expenditure
and maximum duration of less than 10% of one
year’s fertiliser bill.

Ail agricultural countries are interested in
legumes, not only as pioneer species on new and
worn out land, but also for their high protein
content. Of the native legumes, the Swainsona
species are at present, probably the most im-
portant. An investigation of their economic
potential was made by A. W. Humphries as part
of a programme of research commenced at the
University of Western Australia, Institute of
Agriculture, under Professor E. J. Underwood’s
direction in 1950. This programme resulted from
the belief that native legume species and par-
ticularly those from the wheatbelt and pastoral
areas had, in view of their adaption to the
climate, a potential as economic plants. Some
of the 52 species of Swainsona, native to Aus-
tralia, are toxic but S', occidentalis, known as
“purple vetch”, is an important fodder species
in the Murchison region and 5. canescens in the
north-east Goldfields area of this State. (Fig. 1).

The second genus of legumes investigated in
this programme, the Kennedy a- is confined, except
for one species Kennedya prorepens to the agri-
cultural and dairying areas of the State. All
are perennials of high palatability to livestock
and are prominent in a disturbed habitat such
as that following clearing and burning. They
usually do not persist under the subsequent
grazing and a factor contributing to this is the
80% or so of hard seeds which do not germinate
for some years, so that there is no immediate
regeneration despite heavy seeding (Silsbury
1956).

Replicated sward trials were planted at
Meckering in 1952 to compare the productivity
of seven Kennedya ecotypes relative to lucerne,
sub-clover, peas and vetches. All the perennials
were cut back in May, 1953 and the plots sampled
in November, 1953 and again in November, 1954

TABLE I

Meckering Yield Trial

Species

Yield cwts./acre (dry

weight)

May, 1953

Nov. 1953

Nov. 1954-

K. prosttra&a (Northam)

15-0

22-5

20-0

K. stirlingii

3-7

11*4

16-2

Lucerne

0-6

2-0

0 • 0

Dwalganup sub-clover

11-5

2

for yields which showed that some of the native
plants tested were comparable and even superior
to the introduced ones in productivity (Silsbury
1958). Yield data for the two most productive
Kennedy a types, relative to lucerne and sub-
clover, are given in Table I.

Fig. 1 . — Swainsona oroboides growing at Cook on the
Nullabor Plains where the average annual rainfall is
six inches.

Trials were conducted also, at Mer redin Re-
search Station to obtain data on the effect of
various times of cutting on the Northam strain
of K. prostrata. Comparative trials with intro-
duced legumes on the lighter soil types at
Merredin proved abortive because these failed
to nodulate and regenerate.

TABLE II

Merredin Research Station 1953-54
K. prostrata planted May, 1952

Time of cutting

Yield cwt./acre (dry matter)

3rd June, 1953 .

6-8

3rd September, 1953

9-7

3rd November. 1953

(10-3 plus 1 ■() seed) 17-9

3rd March, 1954

5-9

The lower yield of the March cut was due to
the loss of foliage following seeding. This trial
was on a relatively small scale and border effects
became apparent due to the depletion of the
subsoil moisture to the maximum depth of
sampling, 42 inches. The seeding re-establish-
ment was relatively poor but despite the dry
seasons the Kennedya appears to have become
stabilised and in 1958 there was a considerable
germination of seedlings in mid- June.

As Silsbury has pointed out, Kennedya is one
of the few perennial legumes which are adapted
to survive in a Mediterranean climate and in
view of his demonstration of its capacity to pro-
duce commercial yields, the development of
suitable methods of management may well be
justified. (See Fig. 2).

While some Kennedya species may have a place
in the general agriculture of this State, native
species have already demonstrated their value
in reclaiming salt affected soils. It has been
calculated that 5% of the agricultural areas of
the State are affected by salt and although this
is a small percentage of the total, it amounts to
a million or so acres. The problem has various
manifestations, but the continued utilisation of
these soils is dependent on the use of salt-
tolerant plant species.

Research by the Department of Agriculture
showed that for seepage areas a grass , P asp alum
vaginatum obtained by the Waite Institute from
South Africa, was very satisfactory, but as it
set no seed, it could be established only from
cuttings. This method of establishment is not
easily achieved over large areas and investiga-
tions were made at the University Institute of
Agriculture by Carpenter (1958) with a view to
developing a free seeding type. He found that
P. vaginatum was native also to the Queensland
coast and that this type did set a little seed
under Perth conditions.

Fig. 2 . — Kennedya prostrata (Crawley ecotype) has a
depth of root penetration of over six feet compared
with 15-18 inches for sub-clover (right in above photo).
This enables it to bring moisture and nutrients from
a considerable depth.

3

Material forwarded from Cheyne Beach near
Albany by Col. Bleechmore was also self -sterile,
but by crossing the different types, relatively
good seed setting was obtained. It may well be
that the grasses collected from Albany are native
to the region.

TABLE III

Paspalum vaginatum

Type Fertile Flowers

South African selfed

, s x Cheyne Beach
„ ,, x Queensland

Queensland selfed

,, x Cheyne Beach
x South African
Cheyne Beach selfed

,, x South African

o ,, x Queensland

Per cent.
0
32
13
11
50
41
i)

32

45

The salt and blue bushes, Atriplex and Kochia
respectively, are important genera in the
pastoral areas of Australia. Working with funds
provided by a New South Wales foundation, the
George Aitken Pastoral Research Trust, A. W.
Humphries, while a Research Officer of the
Institute of Agriculture, asembled a collection
of these and related genera. This collection
showed that within each species there is a range
of variability which could well be the basis for
the development of superior strains for use in
re-seeding “eaten out” areas.

dm*

Fig. 3 .— Kochia brevifolia being vised to reclaim salt
affected land in the West Australian wheatbelt.

Investigations of a number of ecotypes of
another native salt tolerant grass, Sporobolus
virginicus have been made at the Institute of
Agriculture by Frith (1957) and these have shown
that they are variable according to source of
collection, but free seeding. The problem of
establishing grasses on salt affected seepage
areas from seed is therefore now largely a matter
of commercial seed production.

Fig. 4.— The inherent variability in wild species is of
great importance in a breeding and selection pro-
gramme. One plant of Old Man Saltbush (A. num-
milaria ) made exceptional growth relative to others of
the same species in the collection at Merredin Research

Station.

Fig. 5 . — Glycine tabacina, a native perennial legume,
growing on the roadside near Bruce Rock in Western
Australia. This plant has the capacity, which may
have agricultural value, to regenerate from roots cut

well below the surface and exposed to sunlight.

More recently the Department of Agriculture
and Mr. B. Parker of Kulin have demonstrated
the value of Kochia brevifolia for the reclamation
of salt land. Not only does this perennial
colonise the eroded areas, but it provides a
reserve of very nutritious green fodder for use
in periods of summer drought, so that there is
a marked improvement in both the quantity and
the quality of feed available on otherwise un-
productive land (Fig. 3).

Kochia brevifolia is widely distributed over
southern Australia and is not confined to salt-
affected soils. Experimental work dating from
1937 at Merredin Research Station on the local
ecotype included a series of feeding stuffs

analyses from material harvested during the
period from August, 1941, to March, 1942. These
investigations by the Department of Agriculture
showed that the crude proteins ranged from 22%
in October to 32% in March with figures as
high as 35% for new growth. The vitamin A
content during the early summer has been shown
(Underwood and Conochie 1943) to be 12 mg/ 100
gr. on a dry basis compared with less than
2mg/100 gr. for the mature annuals in the
pasture. Blue bush is very low in fibre and
therefore should balance the normal dry feed,
but D. H. Curnow has directed attention to its
oxalate content of 6% on a dry weight basis.
From these data it appears that K . brevifolia
may well have a place on every wheat farm as
a source of high protein and vitamin rich sup-
plementary fodder, during the long dry summers
and the Department of Agriculture is undertak-
ing a seed increase programme to make it more
freely available to interested farmers (S. T.
Smith, personal communication).

While the native flora is already making a
contribution and has a considerable potential,
the problems associated with its domestication
are considerable.

It is for this reason that the Royal Society
has advocated the establishment of a Botanic
Garden. To many such a Garden should not
be a graveyard where the last sad vestiges of
a once great flora would be preserved from total
extinction. Rather, it should serve as a centre
from which a vigorous programme of research
and development, as well as preservation, could
be inspired and co-ordinated. The legislation
governing the conservation and utilisation of our
flora is for the most part dated 1895, at least
in concept, if not in enactment and a review of
the position in the light of modern developments
is long overdue.

It is visualised that a function of the Garden
would be to provide funds, to enable the various
organisations to conduct specific research pro-
jects, as part of continuing programmes of
domestication and conservation.

The collection and maintenance of as many
species as possible is an extremely urgent one,
for delay will reduce the chances of ultimate
success in plant domestication by restricting the
range of material available. Already the list of
native plants which are believed to be extinct is
formidable and the heath flora is still disappear-
ing at the rate of hundreds of thousands of acres
per year. There is evidence that any uncultivated
areas on farms will not persist, for sheep need
roughage to balance a predominantly sub-clover
diet. When Silsbury began his collection of
species of Kennedya he was unable to locate
one species and he had great difficulty in finding
others which were, from botanical accounts,
common and widespread during the earlier days
of settlement. Within a few years great sections
of our flora outside the forest reserves will be
extinct and among them will be many with the
greatest potential for economic development.

The need for a range of plants of any species
is shown in the development of a disease resist-
ant strain of the red-flowering gum, Eucalyptus
ficifolia (Cass-Smith, personal communication).
Only one tree in about four hundred carries the
heredity for immunity to the fungal wound

parasite which causes the die-back in trees of
this species. It would be easy, therefore, to test
one thousand trees without obtaining the desired
immune one.

In addition to the urgent and immediate need
for plant collection and preservation, research
will be required into the problems of manage-
ment, germination and nutrition. At the Uni-
versity Institute of Agriculture programmes of
investigation on seed germination have been
undertaken with some Kennedya species, Atriplex
and Kocliia genera. Most species have evolved
controls which, while they make them well
adapted to survive under natural conditions,
create difficulties in respect to their use in agri-
culture, for the conditions under which seed will
germinate obviously affects establishment.

With Kennedya Silsbury demonstrated that by
scarification alone, germination could be in-
creased from 15% to 62% which would be
satisfactory for establishment. Firing gave no
improvement in germination. Salt tolerant
species are apt to germinate slowly and poorly.
With the salt tolerant grass, Sporobolus
virginicus, Frith found at the Institute of
Agriculture, that germination was aided by both
light and the fertiliser, potassium nitrate. He
suggested that by planting the seed in narrow
furrows with potassium nitrate, good germina-
tion and establishment should be obtained.

Establishment difficulties due to poor germina-
tion are usual with salt and blue bushes. In-
vestigations by D. G. Wilcox at the University
Institute of Agriculture have shown that seed
disinfection with a fungicide such as organic
mercury and planting in late autumn can
markedly improve germination.

These studies apart from their direct value,
have served to show that many of the serious
barriers to the domestication of our native plants
can be overcome by research.

The reliance on introduced winter growing
annuals has resulted in the development of
systems of grazing management to which the
native perennials are not well adapted, for the
scarcity of green feed during the summer can
result in their being exposed to extremely high
stocking rates. Every green supplement, high
in protein and vitamin A is particularly valuable.
When it is appreciated that on most wheat farms,
about one half of the wool is grown during the
four or so months of green feed, the value of
such a supplement may be to achieve more than
just the maintenance of the sheep in good health.
Yields obtained by Silsbury with Kennedya, and
Mr. B. Parker with blue -bush suggest that the
quantity of fodder produced would be consider-
able.

It is likely that for native legumes controlled
grazing will be necessary during the summer
months but with K. brevifolia, protection from
stock appears to be necessary only in the year
of establishment. Consequently a few acres of
Kocliia in each paddock would provide a valuable
summer supplement at very small cost.

Although the general experience is that native
species do not persist under grazing, this may
be a result of insufficient ecotypes being tested.
It has been observed by Silsbury that Kennedya
prostrata if heavily grazed will shoot from below
the crown, while a glycine from near Shackleton

5

has been observed to regenerate from a root cut
eight inches below the surface (Fig. 5). With
Swainsona beasleyana at Mukinbudin, rabbits
regularly cut the plants back to an inch or more
below ground level without killing them.

At Kukerin Mr. A. R. Abbott has Kennedya
Vrostrata which has persisted in a paddock that
has been cropped and grazed for 40 years, while
K. prorepens has survived 30 or so years of
farming at Ghooli east of Southern Cross.

Before large scale grazing trials can be con-
ducted, it will be necessary to obtain seed in
commercial quantities. Dehiscence at maturity
is a characteristic of wild species, but non-
shattering types would greatly simplify seed
collection. Such forms have been developed for
most cultivated species and mutation induction
by irradiation could be used if no suitable plants
were found in nature. Plant breeders now have
a wide range of chemical and other techniques
for inducing variation, so that, given time, almost
any plant could be tailored for domestication.

In considering the implementation of a new
policy towards our native plants, the Royal
Society is mindful that the National Parks Board
of Western Australia is the organisation nomin-
ated by Parliament in the Act of 1895 to manage
parks and reserves vested in the Crown. This
Act instructs the Board to “Otherwise improve
or ornament such parks or reserves and do all
such things as are calculated to adapt such parks
and reserves to the purposes of public recreation,
health and enjoyment”. While the demand for
recreational areas is becoming greater each year,
the need for an organisation with adequate funds
and staff to ensure the preservation of our flora
as well as its exploitation, is urgent and prefer-
ably its headquarters should be located, with
the Herbarium, in a Botanic Garden.

It is only by having in existence such an
organisation that adequate parks, both regional
ones in the country and others in the city, could
be created and maintained to serve the recrea-
tional as well as the economic needs of the
community. The need to co-ordinate and
classify research in such diverse fields as
pharmacology and the physiology of salt tolerant
grasses is self-evident, while there is little of
tourist interest in this State once the wild flowers
have disappeared. The Royal Society has
prompted the Government to enquire into the
possibilities of establishing such a Garden and
related organisation and I feel sure that, as in
the past, our leaders in public life today are
statesmen who will give the proposals the careful
and urgent consideration which they merit.

References

Carpenter, J. A. (1958). — Production and use of seed in
sea-shore paspalum. J. Aust. Inst. Agric. Sci.
24: 252-256.

Frith, J. L. (1951). — The germination of Sporobolus
virginicus. J. Aust. Inst. Agric. Sci. 23: 69-75.
Grieve, B. J. (1956). — Studies in the water relations of
plants. I. Transpiration of Western Aus-
tralian (Swan Plain) sclerophylls. J. Roy.
Soc. W. Aust. 40: 15-30.

Nunn, W. W., and Suijdendorp, H. (1954). — Station
management — the value of “deferred graz-
ing”. J. Dep. Agric. W. Aust. 3: 585-587.
Silsbury, J. H. (1956). — Studies in the genus Kennedya
Vent. M.Sc. (Agric.) Thesis, Univ. W. Aust.

(1958). — Agricultural potentialities of the

genus Kennedya Vent, in Western Australia.
J. Aust. Inst. Agric. Sci. 24: 237-242.
Underwood, E. J., and Conochie, J. (1943). — Vitamin A
in the nutrition of sheep in Western Aus-
tralia. 2. The carotene content of pasture
species. Aust. Vet. J. 19: 37-42.

White, D. E. (1958). — Recent advances in the chemistry
of Western Australian plants. Presidential
address, 1956. J. Roy. Soc. W. Aust. 41: 1-11.

6

2. — Permian Stratigraphy of the Woolaga Creek Area, Mingenew District,

Western Australia

By G. Play ford*

Manuscript accepted — August 1st, 1958

The Permian stratigraphy of the Woolaga
Creek area, in the northern part of the Perth
Basin, has been investigated in detail. The
succession is similar to that in the classical
Irwin River area, 18 miles farther north. There
are, however, some significant facies variations
between the two areas; in particular, the Irwin
River Coal Measures are notably less carbona-
ceous at Woolaga Creek than in the type area.
The sequence in the Woolaga Creek area, from
the base upwards, is: Nangetty Formation,

Holmwood Shale, High Cliff Sandstone, Irwin
River Coal Measures, Carynginia Formation,
Wagina Sandstone. A new unit, the Woolaga
Limestone Member of the Holmwood Shale,
is proposed formally herein. The member con-
tains an abundant marine fauna including
two goniatites, which indicate a Sakmarian
age.

Notable features of the Woolaga Creek sec-
tion include: the abundance of thin, lenti-
cular beds of limestone in the Holmwood Shale;
the presence of a marine fauna in the basal
part of the High Cliff Sandstone; well-devel-
oped slumping in the Irwin River Coal
Measures; conspicuous sandy intercalations
within the Carynginia Formation; a single plant
fossil locality in the Wagina Sandstone; and
the sporadic recurrence of erratic boulders in
all the formations overlying the Nangetty
Formation, with the exception of the Wagina
Sandstone. The Fossil Cliff Formation and the
Beckett Member, well-known in the Irwin River
section, are not represented at Woolaga Creek.
The Irwin River Coal Measures and the Wagina
Sandstone are considerably thicker than in the
type area. The strata are believed to be of
Sakmarian and Artinskian age. They record
a sequence of marine and non-marine environ-
ments, including two distinct periods of barred
basin deposition.

The sediments are on the down-thrown,
western side of the Darling Fault, the major
structural feature of the area. A gentle east-
erly tilt characterizes the strata, except in the
vicinity of the Darling Fault, where they are
deformed synclinally against the Archaean
metamorphic complex. The Darling Fault at>-
pears to have a vertical or near-vertical dip.
Small, usually antithetic, gravity faults are
common within the Permian strata.

The lateritic surface of the flat-topped hills
and tablelands in the area is representative
of the once continuous, but now extensively
dissected Victoria Plateau.

Contents

Introduction

Previous Investigations
Physiography
General Geology
Introduction

Archaean

Permian

Epi-Permian

Page

7

9

9

10

10

11

11

13

♦Department of Geology, University of Western Aus-
tralia, Nedlands, Western Australia. Present ad-
dress: Sedgwick Museum, University of Cambridge,
England.

Contents — continued

Page

Permian Succession 13

Nangetty Formation 13

Holmwood Shale .... 14

High Cliff Sandstone 17

Irwin River Coal Measures 20

Carynginia Formation 23

Wagina Sandstone 24

Structure 25

Geological History 26

Acknowledgements 27

References 27

Introduction

The Woolaga Creek area, as mapped in de-
tail by the author, comprises approximately 20
square miles and is situated 200 miles north of
Perth and 12 miles east of Mingenew (see
Fig. 1). The area lies in the Victoria Sub-
division of the South-West Land Division of
Western Australia. It is situated within the
following limits of latitude and longitude: —
lat. 29° 09' S. and 29° 15' S., long. 115° 36' E.
and 115° 43' E.

The Permian sediments of the Mingenew dis-
trict have been the object of geological investi-
gation and interest since the middle of the
last century. Most of this work, however, was
confined to the classical exposures in the Irwin
River area, largely because of the economic
possibilities of the Irwin River Coal Measures.
The southern or Woolaga Creek area has been
comparatively neglected and previously pub-
lished work on this area is only on a broad
reconnaissance scale.

The present investigation was undertaken to
examine in detail the Permian stratigraphy of
the Woolaga Creek area and to correlate the
strata, as far as possible, with the well-known
sequence in the Irwin River area, 18 miles
to the north. The environment of deposition of
the sediments has been studied as an integral
part of the investigation.

In all, ten weeks were spent in the field,
during which time the detailed mapping of the
area was carried out and all outcrops were
visited and examined. Palaeontological and
lithological material was collected for subse-
quent laboratory examination. The detailed
petrography is included in the author’s thesis
from which this paper was compiled; this thesis
is in the library of the Department of Geology,
University of Western Australia.

Vertical air photographs, supplied by the De-
partment of Lands and Surveys, Perth, were
used in the field mapping, together with the

7

Fig. 1. — Locality Map.

Pintharuka one-mile-to-the-inch Army sheet.
Information was obtained also from the maps
of Campbell (1910) and Johnson, de la Hunty
and Gleeson (1954).

The Army map was photographically en-
larged approximately to air photograph scale
and transferred to “Kodatrace” for use in the
field. This was not satisfactory for a final
geological map because many of the topographic
features on the Army map had not been accu-
rately positioned. Therefore, it was found
necessary to redraft the base for the geological
map of the area from the air photographs, laid
out under satisfactory control. The Army grid

was imposed on the geological map (Map 1)
and all localities cited in the text are referred
to this grid. Under this system the first three
figures of the grid reference represent eastings,
and the last three figures represent northings.
For example, Red Hill has an east-west read-
ing of 64.7 and a north-south reading of 83.8.
Its grid reference is then given as (647838). A
geological interpretation map (Map 2) and cross
section (Fig. 3) were compiled on the basis of
the geological map.

A tacheometer and staff were used in the
detailed measurement of the Woolaga Creek
stratigraphic section.

8

Previous Investigations

Reviews of previous geological investigations
in the Mingenew district have been given in
recent publications, notably in Clarke, Prender-
gast, Teichert and Fairbridge (1951), in John-
son et al. (1954), and in McWhae, Playford,
Lindner, Glenister and Balme (1958). The fol-
lowing discussion on previous work will be con-
fined to those papers having obvious application,
or containing specific reference, to the area
under consideration.

The work of Campbell (1910) was an
outstanding contribution to the knowledge
of the geology of Western Australia. As
an Assistant Geologist with the Geologi-
cal Survey of Western Australia, Camp-
bell mapped a total area of 4,500 square miles,
paying particular attention to the distribution
and stratigraphy of the “Carboniferous and
Permo-Carboniferous” rocks; many of his con-
clusions are still accepted and with considerable
respect. For example, he was the first to recog-
nize the glacial sequence in the area. The geolo-
gical map compiled by Campbell embraces the
Woolaga Creek area, although most of his refer-
ences in the text are to the Irwin River section,
because of its possible economic potential. How-
ever, he notes the presence of “carbonaceous
seams” on Woolaga Creek, and his map shows
two outcrops of erratic boulders to the east of
the area mapped by the present author.

Woolnough and Somerville (1924) were con-
cerned mainly with the valley of the Irwin River,
and referred only briefly to the Woolaga Creek
area. They suggested a probable correlation
between the Woolaga Creek “bituminous seams”
mapped by Campbell (1910) and the well-known
coal seams on the North Irwin River. The
“Main Glacial Horizon” was traced by these
authors more or less continuously from the
Irwin Valley to a point about 3 miles south-
west of Mt. Budd.

A comprehensive review of the Permian
stratigraphy of the Irwin River area is con-
tained in the 1951 paper of Clarke and his co-
authors. The structural hypothesis presented
in this paper was based largely on air photo-
graph studies by Fairbridge. Large-scale step
faulting was considered the major structural
pattern, as opposed to the old anticlinal hypo-
thesis. Although containing only a brief refer-
ence to the Woolaga Creek locality, the im-
portance of this publication to the present
author is that it represents the first concise
account of the Irwin River succession, with
which a correlation of the southern section will
necessarily be attempted.

In May, 1950, a party of senior students from
the University of Western Australia carried out
some plane table geological mapping at Woolaga
Creek, under the direction of Dr. R. W. Fair-
bridge. This was not a detailed survey, and
the most significant observations are to be found
in Fairbridge (1952).

Two species of Permian ammonoids, Meta-
legoceras campbelli and Uraloceras irwinense,
from the Holmwood Shale of the Mingenew
district were described by Teichert and Glenis-
ter (1952), who recognized their Sakinarian af-
finities. The type locality was in the Irwin

River area, but the authors stated that the
two species were also found in a limestone band
“in the southern part of the Irwin Basin south
of the Lockier River,” i.e. in the Woolaga Creek
area. Their geological map shows the outcrop
of the band in this locality.

In 1949, W. Johnson, L. E. de la Hunty and
J. S. Gleeson, of the Geological Survey of West-
ern Australia, mapped an area of 1,950 square
miles, mainly by reconnaissance methods, in
the Yandanooka, Mingenew and Eradu dis-
tricts; the Woolaga Creek area was included
in the survey. Their work was published in
1954. The object of this investigation was to
determine the economic value of the Permian
coal seams. Sufficient evidence was put for-
ward in the publication to negate the com-
mercial possibilities of this coal. Johnson et al.
(1954) modified the rock unit nomenclature of
the Permian succession proposed by Clarke and
his co-authors and favoured a broad anticline
as the overall structural feature, with accom-
panying modification by faulting. Theirs was
the first attempt to trace the established forma-
tions of the Irwin River section into the little-
known southern section at Woolaga Creek. A
notable discovery was the marine fauna in the
basal part of the High Cliff Sandstone at
Woolaga Creek. Of necessity, their survey was
on a regional scale, but they recognized the
desirability of a more detailed study of the
Woolaga Creek area in light of the excellent
exposures in the locality and the probability
of so gaining a more complete picture of the
Permian succession in the Irwin River district.
As outlined above, that is precisely the aim of
the present investigation.

The most recent work in the Mingenew dis-
trict, prior to that undertaken by the present
author, was carried out by geologists of West
Australian Petroleum Pty. Ltd., as part of a
comprehensive, semi-detailed survey of the
Perth Basin. Their work on the Permian sedi-
ments is summarized by P. E. Playford and S.
P. Willmott in McWhae et al. (1958). The
nomenclature of Playford and Willmott modifies
slightly that of Clarke et al. (1951) and is fol-
lowed in this paper.

Physiography

The Woolaga Creek area consists of sharply
defined flat-topped uplands rising abruptly from
broad sweeping lowlands, drained by narrow in-
termittent watercourses.

The flat-topped landforms of the area are
characteristic of the northern part of the Perth
Basin, and represent remnants of a once con-
tinuous plateau, the Victoria Plateau of John-
son et al. (1954). These uplands owe their
preservation to the existence of a protective
capping of duricrust, developed on the softer
Permian strata and associated with the old Vic-
toria Plateau; the transition of the larger ex-
panses of the plateau to mesas and ultimately
to buttes represents successive stages in cir-
cumdenudation. The highest hills in the area
studied are Mt. Budd (598858) and Beere Hill
(634856), at respective heights above sea level
of 930 feet and 934 feet. Mt. Budd (Plate 1,
1) is a butte, whereas Beere Hill is a mesa. The

9

perfect example of a butte in its ultimate form
is Red Hill (647838), a symmetrical cone-shaped
hill (see Plate 1, 3).

The soft sediments of the Holmwood Shale
underlie the western part of the Woolaga Creek
area. Being highly susceptible to erosion these
sediments give rise to a gently undulating low-
land topography. Farther east, however, the
greater durability of succeeding rock units re-
sults in a somewhat more rugged terrain, in-
cluding relatively numerous and extensive flat-
topped remnants of the Victoria Plateau. The
cuesta in the vicinity of (632826) is a graphic
illustration of the abrupt stratigraphic change
from soft to generally more resistant rock
types. This prominent feature, upon which is
the site of the old “Glendevon” homestead, is
composed of High Cliff Sandstone, which suc-
ceeds directly the soft Holmwood Shale.

Most of the area studied is drained by
Woolaga Creek, a tributary of Green Brook,
which in turn flows into the Lockier River.
Ebano Creek passes through the north-eastern
part of the area and is a tributary of the up-
per Lockier River. Several lesser streams em-
anate from the long line of breakaways in the
south-western part of the area and find their
way eventually into Green Brook. All of the
streams in the area are dry for most of the
year, flowing for a short time only after heavy
falls of rain. Woolaga and Ebano Creeks and
their tributaries provide fine exposures of the
Permian strata in which they are incised.

The lower part of Woolaga Creek flows to-
ward the south-west, perpendicular to the strike
of the underlying sediments. Higher in its
course, however, there is an abrupt change in
direction so that upper Woolaga Creek has a
subsequent character, flowing parallel to the
strike direction.

In its upper reaches, Woolaga Creek receives
several tributaries flowing from the east and
traversing the Darling Fault high in their
courses. One of these, entering the main creek
at (655821), is of particular interest. In the
upper part of its course this stream has cut a
fairly deep, V-shaped gorge in the Precambrian
terrain and has a moderate grade. To the
west, on crossing the Darling Fault, the stream
exhibits an immediate and striking change in
character. It begins to meander freely and at-
tains a notably lower gradient. This pro-
nounced change in stream character, which is
well-shown by the air photographs, can be re-
lated directly to a similar change in the nature
of the underlying rocks— from the highly re-
sistant Precambrian metamorphic complex on
the east to the soft abutting sediments of the
Permian Carynginia Formation on the west
side of the Darling Fault.

In contrast to Woolaga Creek, the lower and
upper parts of Ebano Creek are respectively
parallel and transverse to the strike of the
Permian strata. The change in direction of
Ebano Creek occurs stratigraphically just be-
low the boundary between the Wagina Sand-
stone and the softer, underlying Carynginia
Formation. The suddenly acquired subsequent
character of the creek appears to be, therefore,
the direct result of the equally sudden change
in the durability of the strata. Ebano Creek

does not change significantly in character on
passing westwards over the Darling Fault. This
is because the resistance to erosion of the mas-
sive Wagina Sandstone, which is truncated
by the Darling Fault in this vicinity, does not
differ markedly from that of the adjacent
Archaean rocks.

Johnson et al. (1954, p. 33) considered it pro-
bable that river capture had occurred between
Woolaga and Ebano Creeks. However, there
is no geomorphological evidence in the area to
support this suggestion. The relatively high-
level, undissected strip of country separating
upper Woolaga Creek from lower Ebano Creek
could scarcely be considered the site of a former
gorge or water gap; this would necessarily be
the situation if the two watercourses were once
connected.

Water supply is a problem for many farming
properties in the Woolaga Creek area, and there
is a continual search for supplies of potable or
even semi-potable ground water. The position
is generally worse in the western lowlands,
underlain mainly by the impervious, saline
Holmwood Shale. Four unsuccessful bores were
drilled recently in the western part of the area.
Three of the bores, at (635824), (638821) and
(654805), penetrated High Cliff Sandstone be-
fore passing into Holmwood Shale in which
they were abandoned. The other bore, sited
at (629823), penetrated Holmwood Shale for
its entire depth. However, there are some wells
in the western lowlands that yield good supplies
of useful water. None of these penetrates the
Holmwood Shale and they are generally located
on the higher slopes of the lowlands. For
example, at (620845) and at (636827), good
supplies of excellent stock water are obtained
from sandstones stratigraphically higher than
the Holmwood Shale. Also, at “Milford” home-
stead in the south-western part of the area,
abundant water for stock and domestic pur-
poses is obtained from a well penetrating fine
yellow sandstone of the Nangetty Formation,
which is stratigraphically below the Holmwood
Shale. Ebano Spring (640861) provides the
best supply of ground water, both quantita-
tively and qualitatively, in the whole of the
area. The water in this instance is derived
from the Wagina Sandstone, the uppermost
unit of the Permian succession.

General Geology

Introduction

In Western Australia the Permian System is
developed in the Perth Basin, the Collie, Muja
and Wilga Basins, the Carnarvon Basin, the
Canning Basin and probably also in the
Bonaparte Gulf Basin. Permian sediments are
known from the Perth Basin only in its northern
part, where the thickest and most continuous
sequence occurs in the Mingenew district.

The Darling Fault is the outstanding structural
feature of West Australian geology. McWhae
et ah (1958) state that it extends meridionally
for approximately 600 miles from the south
coast to near the south end of the Carrandibby
Range. On geophysical evidence, Thyer and
Everingham (1956) considered that the Darling
Fault has “a maximum throw of perhaps 30,000

10

feet or more.” It represents the well-defined
eastern boundary of the Perth Basin, marking
generally the junction between the sediments
and the Archaean rocks. Thus, from the vicinity
of Arrino, through the Mingenew district to as
far north as Mullewa, the Permian sediments are
bounded on their eastern margin by the Darling
Fault. The West Australian Precambrian Shield
extends eastward from the fault line to form the
Darling Plateau.

In the Woolaga Creek and Irwin River areas,
the relationship of the Permian to the underlying
rocks is not visible. However, to the south, in
the Yandanooka area, the basal part of the
Permian succession overlies unconformably the
Yandanooka Group of Proterozoic or early
Palaeozoic age. Where Permian rocks overlie
the Archaean complex directly, Johnson et al.
(1954, p. 42) have noted that the actual contact
is always obscured by alluvium.

Archaean

The stable crystalline complex, which abuts the
Permian sediments along the Darling Fault, is
composed of high-grade metamorphic rocks of
Archaean age.

The north-north-westerly trending Yandan-
ooka Hills, several miles south-west of the area
studied, are composed of Archaean metamorphics.
This prominent structural feature was termed
the Mullingarra Axis by Woolnough and Somer-
ville (1924). Archaean rocks also crop out in
the Brockman Hills, some 5 miles west of Mt.
Budd, immediately north of the Mingenew-
Morawa, road; as stated by Woolnough and
Somerville, this small Archaean inlier represents
a northerly continuation of the Mullingarra Axis.

Between the Darling Fault and the Archaean
Mullingarra Axis, later sediments obscure the
down-thrown basement. Thus, in the Woolaga
Creek area, Archaean rocks are presumed to
underlie the Permian strata at considerable
depth.

Beyond the Darling Fault, adjacent to the
area studied, the outcrop on the Archaean terrain
is generally poor, and there is widespread de-
velopment of laterite. The major rock types
observed were granitic gneisses and hornblende
gneisses cut by quartz-feldspar pegmatites and
dolerite dykes. The foliation of the gneisses dips
steeply, generally to the west, with an average
strike of 140°. This conforms closely to the
usual north-west tectonic trend of the Central
Province of Prider (1952), who considered that
the Archaean rocks of this province had been
isoclinally folded on north-westerly trending
lines. Reliable lineation data could not be
obtained; the few readings taken indicated a
wide variability.

The fault contact between the Permian strata
and the Archaean metamorphics is rarely exposed
in the area, although the air photographs display
the Darling Fault strikingly as a pronounced
north-north-westerly trending line. It is an
example of a major geological structure, the
nature and extent of which is clearly evident
when viewed from the air, but which is not
immediately perceptible when inspected at close
quarters. From an examination of the air
photographs supplemented by field observations,
it is apparent that a number of factors have been

effective, both individually and collectively, in
accentuating the line of the Darling Fault on
this large scale. The following is a brief account
of these factors: —

(i) Two tributaries of upper Ebano Creek
have excavated the fault line in the north-
eastern part of the area.

(ii) A marked change in the character of
streams traversing the Darling Fault is apparent
in one locality; this has been described under
Physiography.

(iii) Several tracks formed by both human
and animal agencies follow parts of the Darling
Fault line. The most striking of these is a
vehicular track which extends south from the
Mingenew-Morawa road, half a mile east of
Ebano Spring, closely following the fault line
for two miles.

(iv) A prominent escarpment marks the Darl-
ing Fault in the vicinity of (664833). This
feature, which may be classed as a resequent
fault line scarp (Cotton 1945, p. 178), has resulted
from the preferential erosion of the soft
Carynginia Formation adjacent to the Archaean
metamorphics.

The Wagina Sandstone, stratigraphically above
the Carynginia Formation, offers more resistance
to erosion. Consequently, farther north, where
this sandstone formation abuts the Archaean
complex, no such escarpment has developed,
although here other factors serve to emphasize
the fault line.

(v) In some places, the Darling Fault line is
marked on the air photographs by a thin, white
line, other than a track. When examined on
the ground this is generally found to be a narrow
zone of steeply dipping Permian strata, im-
mediately adjacent to the fault. At one locality
(679799), the fault line is marked by a low ridge
of travertine, which is about 15 yards wide.

(vi) Plant distribution accentuates the trace
of the Darling Fault in many places. The line
of the fault itself generally supports a prolific
growth of shrubs and trees, which is particularly
noticeable in areas of sparse vegetation. In
such areas, the Darling Fault is displayed on the
air photographs as a dark, narrow line of timber,
surrounded on either side by areas of scattered
vegetation. Also, the composition and density
of the flora often differ notably on either side
of the fault line.

(vii) Abrupt changes in soil type on passing
from one side of the Darling Fault to the other,
are usually shown by the air photographs as
subtle, but equally abrupt variations in “tone”.
This is, of course, restricted to localities of
subdued topography where the soils are mainly
residual over the Permian and adjacent Archaean
rocks.

For edaphic reasons, factors (vi) and (vii) are
closely inter-related, the one augmenting the
other.

Permian

The Woolaga Creek and Irwin River areas
provide the two best sections of Permian strata
in the Perth Basin. Elsewhere in the basin,
Permian rocks are known from bores and poor
surface exposures in the Yuna-Eradu district, *
where they are largely covered by horizontal
Jurassic sediments. The basal unit of the

11

Permian succession, the Nangetty Formation,
is found overlying the Proterozoic or early
Palaeozoic Yandanooka Group as far south as
Three Springs.

The present author has been able to confirm
the presence in the Woolaga Creek area of a

stratigraphic sequence which is essentially
similar to that developed in the well-known
Irwin River section (see Fig. 2). A notable
difference between the two sections is the absence
of the Fossil Cliff Formation in the Woolaga
Creek area; this formation is a well-known unit

WOOLAGA CREEK IRWIN RIVER

VAGINA SANDSTONE 300'+

CARYNGINIA FORMATION 800'

IRWIN RIVER COAL MEASURES 217'

HIGH CLIFF SANDSTONE 79'
FOSSIL CLIFF FORMATION 86 7

IT

O

K

o

o

o

</l

BECKETT MEMBER 130'

Co

r\j

O

NANGETTY FORMATION 1,500'+

G.P. 1958

Fig. 2— Columnar stratigraphic sections of the Permian System as developed in the Woolaga Creek and Irwin
River areas. The Woolaga Creek section was measured in detail by the present author The Irwin River section
is based on thicknesses given by Clarke et al. (1951) and by McWhae et al. (1958).

12

of the Irwin River section. Also, the Beckett
Member, which contains the large goniatite
Metalegoceras jacksoni in the Irwin River area,
does not crop out in the area under consideration.
Both the Irwin River Coal Measures and the
Wagina Sandstone attain considerably greater
thicknesses at Woolaga Creek than in the type
area. A new unit, the Woolaga Limestone
Member of the Holmwood Shale, is proposed
formally in this paper.

In summary, the Permian succession of the
Woolaga Creek area (from top to bottom) is as
follows: —

(6) Wagina Sandstone: Massively bedded,
white and occasionally red sandstone
and rare conglomerate, with plant-
bearing intercalations of siltstone and
shale near the top.

Thickness: 796 feet (plus).

(5) Carynginia Formation: Predominantly
grey and black jarositic siltstone, with
interbedded yellow, reddish-brown and
white sandstones and siltstones;
■‘dumped” erratic boulders occur at the
base.

Thickness: 844 feet.

(4) Irwin River Coal Measures: Interbedded
very fine to coarse-grained sandstones,
siltstones, and claystones containing
abundant plant fossils.

Thickness: 404 feet.

<3) High Cliff Sandstone: Massively bedded
white sandstone and rare conglomerate.
In the basal part, marine fossils occur
in lenses of red-brown ferruginous
sandstone.

Thickness: 102 feet.

(2) Holmwood Shale: Grey clayey siltstone
containing abundant jarosite and gyp-
sum, with thin, lenticular beds of lime-
stone. The Woolaga Limestone Member
contains a rich marine fauna, whereas
the other limestone beds are sparsely
fossiliferous.

Thickness: 435 feet (plus).

( 1 ) Nangetty Formation : Yellow siltstone
and fine-grained silty sandstone, often
containing pebbles, cobbles and boulders
of gneiss, quartzite, chert and dolerite.

Thickness: Indeterminable.

The strata are believed to fall entirely within
the Sakmarian and Artinskian Stages of the
Permian System.

Epi-Permian

Superficial deposits overlie the Permian strata
in many parts of the Woolaga Creek area. They
occur on both lowlands and uplands and rarely
attain a thickness exceeding 35 feet. The age
of these deposits, apart from being obviously
post-Permian, is not known.

(i) Victoria Plateau Beds . — These rocks were
originally termed the “Plateau Beds” by Wool-
nough and Somerville (1924) and were later
referred to as the Victoria Plateau Beds by
Fairbridge (1952) and Johnson et al. (1954).

The Victoria Plateau Beds have only minor
and restricted occurrence in the Woolaga Creek
area. Lithologically, they are not unlike the
Wagina Sandstone, and consist of massively
bedded, medium-grained, white sandstone, which
is sometimes mottled red. The beds are ap-
parently horizontal and rest unconformably on
the Permian strata. They are affected by
lateritization. Outcrops of the Victorian Plateau
Beds are to be seen at various places high on
the peripheral breakaways of a large tableland in
the north-western part of the area. Typical
outcrops occur at (604872), (613866), (618865),
and (606866).

The age of the Victoria Plateau Beds has
always been conjectural owing to the apparent
absence of fossils, and various authors have
considered them to be of either Jurassic or
Tertiary age.

(ii) Duricrust and Sand-Plain. — The surface
of the Victoria Plateau is marked by a hard,
horizontal capping of duricrust, frequently over-
lain by sand, on the flat-topped hills and table-
lands in the area. This resistant surface gives
rise to the familiar breakaway topography, and
its veneer of quartz sand supports the usual low
sand-piain scrub. The duricrust is mainly
lateritic, but in several localities a highly siliceous
variety (“billy”) is developed. The process of
laterization has caused a general hardening,
leaching and colour mottling of the underlying
Permian strata to a depth of 30 feet or more
below the upper ferruginous, concretionary zone.

(iii) Travertine. — Travertine (or caliche) has
been observed as a sporadically developed surface
capping on both the Permian and Archaean
terrains, around the uppermost reaches of
Woolaga Creek. An extensive outcrop occurs in
the vicinity of (668809) where large, horizontally
disposed slabs of this white, lime-rich rock are
exposed along the banks and in the bed of
Woolaga Creek. The ridge of travertine, crop-
ping out along the Darling Fault line at (679799),
has been noted above. On the Darling Plateau,
about three miles east of Ebano Spring, there
is another large outcrop of travertine, forming
a low bouldery mound, 200 yards south of the
Mingenew r -Morawa road.

(iv) Consolidated Alluvium. — Superficial de-
posits of reddish, ill-sorted conglomerates and
coarse-grained sandstones are exposed in some
places along the watercourses. They contain
laterite pebbles, together with fragments of
Permian and Archaean rocks, and are loosely
cemented by ferruginous clay. These beds repre-
sent lithified river alluvium.

Permian Succession

Nangetty Formation

This formation was originally termed the
“Nangetty Glacial Formation” by Clarke et al.
(1951) and has since been amended to its
present title by P. E. Playford and S. P. Will-
mott (in McWhae et al. 1958). The type
locality is in the Nangetty Hills in the Irwin
River area, where the formation comprises a
poorly exposed sequence of tillite, boulder beds
(containing many striated and faceted erratics),
sandstones, conglomerates, siltstones and shales,
and attains a thickness of about 1,500 feet.

13

The Nangetty Formation crops out in the ex-
treme south-western part of the area studied. As
in the Irwin River area, exposures are poor and
it was not possible to measure a stratigraphic
section or to delineate the relationship with
the overlying Holmwood Shale. The formation
consists of poorly sorted yellow siltstone and
fine-grained silty sandstone, often containing
pebbles, cobbles and boulders of gneiss, quart-
zite, chert and dolerite up to 2i feet in diameter.
These weather out readily as a superficial
gravelly accumulation. The dip of the strata
is indeterminable owing to their massive
nature; however, they appear to be approxi-
mately horizontal.

To the east of the Woolaga Creek area, there
are several prominent patches of erratic
boulders representative of this formation.
Farther south, in the Yandanooka area, the
Nangetty Formation rests unconformably either
on Archaean gneiss or on the Yandanooka
Group of Proterozoic or early Palaeozoic age.
In the Irwin River area, the formation is con-
formable with the overlying Holmwood Shale.

The glacial origin of the Nangetty Formation
was first postulated by Campbell (1910) on the
evidence of the striated boulders, and has been
confirmed by subsequent workers. P. E. Play-
ford and S. P. Willmott (in McWhae et al.
1958) discovered varved shales in the formation
in the Mullewa district, pointing to the fact
that it is at least partly terrestrial.

In the Woolaga Creek area the Nangetty
Formation appears to be unfossiliferous. Else-
where, the only fossils obtained from the
formation are pollen grains and spores from
the Kockatea Creek bores in the Eradu district.
These suggest a Sakmarian age for at least
part of the Nangetty Formation (McWhae
et al. 1958).

High Cliff Sandstone (102 feet)

Holmwood Shale (435 feet +):

Unit Thickness

feet

11. Siltstone, dark grey weathering pale
grey and brown, clayey; contains
abundant yellow jarosite as bands,
small nodular concretions and irregu-
lar masses together with less frequent
layers and concretions of gypsum
which is often associated with alunite.

Plates of gypsum (selenite) up to 1£
feet in diameter and £ inch thick

were noted 89

10. Limestone, dark grey weathering pale

grey, hard, dense. Bouldery outcrop. 1

9. Siltstone, as in unit 11. Sporadic

outcrop 8

8. Limestone, grey weathering pale grey,
hard, dense; thin section showed the
presence of scattered pyrite, also
rare microfossils including calcareous
spicules, indeterminate foraminifera
and woody plant material with well-
preserved cellular tissue. Bouldery

outcrop 2

7. Siltstone, as in unit 11. Sporadic

poor outcrop. 81

6. Woolaga Limestone Member (proposed
herein). Limestone, grey weathering
pale grey, hard, dense; vugs of chal-
cedony and of recrystallized calcite are
common; contains a rich fauna in-
cluding the small goniatites Meta-
legoceras campbelli and Uraloceras
irwinense, together with crinoids,
nautiloids, brachiopods, pelecypods,
gastropods, conulariids and serpulids;
the fossils are often silicified.

Bouldery outcrop 3

5. Siltstone, as in unit 11. Poor out-
crop 10

4. Limestone, grey weathering pale grey,
hard, dense; rare microscopic spicu-
lar material (as in unit 8) was seen
in thin section. Bouldery outcrop. 3

3. Siltstone, dark grey weathering pale
grey and brown, clayey, jarositic,
rarely gypseous. Sporadic poor out-
crop 80

2. Limestone, grey weathering pale grey,
hard, dense, abundant clear recrystal-
lized calcite. Bouldery o\;tcrop 1

1. Siltstone, as in unit 3. Sporadic

poor outcrop. 157 +

Base of formation not exposed.

Holmwood Shale.

(i) Stratigraphy . — The Holmwood Shale was
named by Clarke et al. (1951) after Holmwood
pastoral station in the Irwin River area, on
which the formation has extensive development.
P. E. Playford and S. P. Willmott (in McWhae
et al. 1958) nominated Beckett’s Gully as the
type section. These authors measured a thick-
ness of 1,820 feet in this locality. Included in
their section is the Beckett Member which they
proposed as a unit of limestone beds occurring
630 feet above the base of the Holmwood Shale.
Within the Beckett Member is the biostrati-
graphically important band containing the
goniatite Metalegoceras jacksoni.

In the distance of 18 miles from the type
section to the Woolaga Creek section, the
Holmwood Shale exhibits little facies variation —
the lithological similarities are marked between
the two localities, although along Woolaga
Creek only the upper part of the formation is
exposed.

The reference section along Woolaga Creek,
commences at (617819) and continues to
(629829). The following is a description of

this section.

The Holmwood Shale occurs in the western
part of the Woolaga Creek area. Scattered,
poor exposures are characteristic, and are
limited to breakaway slopes and to the more
deeply incised watercourses. The formation
consists predominantly of grey, clayey siltstone
containing, as secondary minerals, abundant
jarosite and gypsum and some alunite.

As stated by Clarke et al. (1951), the jarosite
and alunite have almost certainly resulted from
the chemical breakdown of pyrite or marcasite
in the original sediment. These authors con-
sidered that the gypsum could have originated
only as a primary precipitate during sedimenta-
tion, and claimed to have found some primary
bands of the mineral. However, a more pro-
bable explanation is that the gysum also is
secondary, and could have resulted from a reac-
tion between primary calcium carbonate and
sulphuric acid produced by the oxidation of the
pyrite (or marcasite) in the sediments.

A good outcrop of gypsum, associated with
alunite, is in a small watercourse at (636811),
where the minerals occur as bands and irregu-
lar masses in jarositic Holmwood Shale. Grey,
concretionary limestone is present also at this
locality.

14

Several large boulders of Frecambrian rock
up to 5 feet in diameter, and possibly of glacial
origin, were noted in cultivated country around

(644796). , , .

A striking feature of the Holmwood Shale
is the presence of thin bands of limestone, which
become particularly frequent towards the top.
Some of these may be merely large, irregular
concretions. They outcrop characteristically
as lines of loose boulders consisting of hard,
dense, crystalline limestone, which is grey,
weathering to pale grey. Usually they can be
traced only for a limited distance along the
strike. This fact, together with their general
distribution as shown by field mapping, points
to lenticularity.

The most continuous and significant of these
limestones is a moderately richly fossiliferous
band which can be traced for two and a quar-
ter miles along the strike. Its fauna includes
crinoids, brachiopods, pelecypods, gastropods,
conulariids, nautiloids, serpulids and two small
goniatites Metalegoceras campbelli and Uralo-
ceras irwinense, which, according to Teichert
and Glenister (1952), indicate a Sakmarian age.
Serpulids are particularly abundant in the lime-
stone in the vicinity of (636807). The Woolaga
Limestone Member is the name proposed for
this fossiliferous limestone band, which attains
an approximate thickness of 3 feet, and occurs
181 feet below the top of the Holmwood Shale
at lat. 29° 12' 8" S., long. 115° 39' 6" E.

Of the numerous other limestone beds dis-
tributed freely within the upper 280 feet of
the Holmwood Shale two, occurring at (644808)
and (597856), contain rare small gastropods,
pelecypods and crinoid stems, whereas the re-
mainder appear unfossiliferous. In thin sec-
tion, however, these limestones are usually seen
to contain microscopic calcareous spicules which
are not abundant and which cannot be identi-
fied precisely, together with indeterminable
organic matter and rare foraminifera. After
both macroscopic and thin section study of
specimens of limestones (apart from the
Woolaga Limestone Member) throughout the
Holmwood Shale, it was found that only two
lenses were lacking in fossils of some descrip-
tion.

A general paucity, in both individuals and
species, is characteristic, therefore, of the
faunas present in the thin lenticular limestones
of the Holmwood Shale, with the notable
exception of the Woolaga Limestone Member.

Clarke et al. (1951) refer to a “serpulid reef
limestone” found in 1949 by Mr. L. de la Hunty
of the Geological Survey of Western Australia
at a locality four and a half miles south-east
of Mt. Budd. They state that “further surveys
here (by Fairbridge) have proved the extension
of these lenticular outcrops over four miles
along the strike.” This is the first reference in
the literature to the limestone band here
termed the Woolaga Limestone Member. As
mentioned previously, the present author was
able to trace the member for a distance of only
two and a quarter miles.

The limestone was considered by Clarke and
his co-authors to be identical with the lime-
stone exposed at Macaroni Hill in the Irwin
River area. It is doubtful, however, whether a

valid correlation can be made between the
Macaroni Hill occurrence and the Woolaga
Limestone Member. Even if serpulids were a
sound basis for correlation, they are abundant
in reef -like proportions only in one part of the
member (at 636807).

A fossiliferous limestone band was discovered
in the Irwin River area on the 1949 excursion
from the Geology Department of the University
of Western Australia. According to Clarke et al.
(1951), this band occurs about 550 feet below
the top of the Holmwood Shale. It contains a
marine fauna which includes the two small
goniatites Metalegoceras campbelli and Uralo-
ceras irwinense, which are present also in the
Woolaga Limestone Member. Thus, since both
these bands have a markedly similar fauna and
both consist of hard, grey, chalcedonised lime-
stone, it would appear that they can be cor-
related with some certainty.

The Beckett Member in the Irwin River area,
which contains Metalegoceras jacksoni , does not
crop out in the Woolaga Creek area.

As mentioned previously, the stratigraphic
relationship of the Holmwood Shale with the
underlying Nangetty Formation is not evident
in the Woolaga Creek area, but it is probably
a conformable one, as it is farther north, in
the Irwin River area. The lenticular Fossil
Cliff Formation, conformably overlying the
Holmwood Shale in the Irwin River area, does
not appear to be represented at Woolaga Creek.
Here, the Holmwood Shale is overlain with
apparent conformity by the High Cliff Sand-
stone.

McWhae et al. (1958) quote 1,820 feet as the
thickness of the Holmwood Shale in the Irwin
River area. At Woolaga Creek, the present
author measured a thickness of 435 feet, which
however cannot be compared with the Irwin
River section, since base is not exposed.

(ii) Biostratigraphy. — The goniatite species,
Metalegoceras jacksoni , Metalegoceras campbelli
and Uraloceras irwinense, indicate that the
Holmwood Shale is of Sakmarian age (Teichert
and Glenister 1952). Dr. B. F. Glenister
(personal communication) correlates M. jack -
soni with faunal assemblage 4 (Ruzhencev
1952) of the lower Tastubian in the southern
Urals, and consequently assigns the Beckett
Member to the early part of the Sakmarian
Substage. (Note that according to current
Russian nomenclature, the Sakmarian Substage
represents the upper part of the Sakmarian
Stage proper, as distinct from the lower part
which is termed the Asselian Substage). In a
forthcoming paper on the Permian ammonoids
of Australia, Dr. Glenister will assign Metale-
goceras jacksoni and Metalegoceras campbelli
to the typical Sakmarian genus Juresanites, on
the basis of their primitive sutures.

Four samples of spoil derived from the Holm-
wood Shale were collected, one from each of
four bores (mentioned previously under Physio-
graphy) in the Woolaga Creek area, which
penetrate the upper part of this formation.
These samples were submitted for palynological
examination to Mr. B. E. Balme, who ascribed
a Lower Permian age to their microflora.

15

The following information about the samples
is contained in a written communication by Mr.
Balme to the author.

“Sample 39247* yielded no recognisable spores
or pollen grains but fairly diverse and basically
similar microfloras were obtained from the
other three samples (39248, 39249, and 39250).
In none, however, were the plant microfossils
well-preserved and precise identification of the
individual spore and pollen specimens was often
difficult. Poor preservation appears to be a
characteristic of the microfloras from the
Holmwood Shale not only in the Woolaga Creek
area but also in the Irwin River area and in the
Kockatea Creek district to the north of
Mingenew. Probably this is due to the activities
of anaerobic bacteria during the deposition of
the Holmwood Shale.

“The following spore and pollen species were
identified in the three productive samples:

Group Triletes

Punctatisporites gretensis Balme and
Hennelly.

Acanthotriletes tereteangulatus Balme and
Hennelly.

Acanthotriletes n. sp.

Granulatisporites n. sp. A.

Verrucosisporites pseudoreticulatus Balme
and Hennelly.

Group Zonales

Cirratriradites cf. splendens Balme and
Hennelly.

Cirratriradites spp.

cf. Reinchospora sp.

Group Precolpates

Marsupipollenites sp.

Group Monocolpates

Entylissa cf. cymbatus Balme and Hennelly.

Group Saccites

Nuskoisporites sp.

cf. Sal mites sp.

? Sahnites sp.

cf. lllinites sp.

Lueckisporites limpidus Balme and Hen-
nelly.

Lueckisporites ampins Balme and Hennelly.

Lueckisporites multistriatus Balme and
Hennelly.

Pityosporites ? n. sp. A.

V estigisporites cf. rudis Balme and Hen-
nelly.

“Occasional small spinose organisms, prob-
ably hystrichosphaerids, were also present,
suggesting a marine or near-marine environ-
ment.

“Discussion: The Lower Permian age of this
microfloral assemblage is attested by the pre-
sence of Punctatisporites gretensis , Verrucosis-
porites pseudoreticulatus, Entylissa cf. cymbatus,
V estigisporites cf. rudis, ? Sahnites sp. and the
abundance of species of Cirratriradites . These
forms all characterise the Greta Coal Measures
in New South Wales, the Lower Coal Measures
at Mersey, Tasmania and the Grant Formation
in the Fitzrov Basin of Western Australia.
Similar microfloras have also been found in

♦Catalogue number in the collections of the Depart-
ment of Geology, University of Western Australia.

sediments from the Lake Phillipson Bore, South
Australia* and in the upper part of the Lyons
Group in the Carnarvon Basin.

“The resemblance is particularly close be-
tween this assemblage and those from the
Grant Formation in the Kimberley Downs 67-
mile Bore and in the B.M.R. No. 3 water bore
in the eastern part of the Fitzroy Basin. It is
heightened by the presence in assemblages
from the Holmwood Shale and the Grant
Formation of the forms cf. Reinchospora sp.
and cf. lllinites sp., neither of which has been
found in separations from any other strati-
graphical units.”

Dickens (1957) has examined several speci-
mens of the Woolaga Limestone Member, from
which he identified <( Sanguinolites ,f sp. and
“Dielasma” sp. ind. He was unable to draw
any conclusions regarding the correlation of
this fauna but he does consider it distinct from
the fauna in the overlying fossiliferous basal
part of the High Cliff Sandstone.

Both Johnson et al. (1954) and particularly
Clarke et al. (1951) refer to the presence of
“dwarf” or “restricted” faunas in the limestones
of the upper Holmwood Shale. However, Tasch
(1953) in a lengthy paper on faunal dwarfism
justifiably emphasises that before any fauna
may be validly designated as “dwarf” or
“depauperate,” it is necessary to apply exhaus-
tive criteria based on wide, intensive collecting,
detailed descriptions of faunal elements, and
ecological studies.

The statements of Clarke and Johnson and
their respective co-authors concerning the sup-
posed faunal dwarfing are not supported by
any such detailed studies and hence may not
be well-founded.

It is true that Metalegoceras campbelli and
Uraloceras irwinense, with a conch diameter
averaging 10 to 15 mm in diameter, are small,
particularly in comparison with M. jacksoni,
but the associated faunal elements in the
W’oolaga Limestone Member appear to be of
normal dimensions. Teichert and Glenister
(1952) remarked on the close similarity of
immature stages of M. jacksoni with specimens
of M. campbelli of corresponding diameters, and
were aware of the possibility of M. cainpbelli
being a stunted, juvenile development of M.
jacksoni due to an unfavourable environment.

However, one of the specimens of M. camp-
belli (39070) collected by the present author
from the Woolaga Limestone Member appears
to negate this possibility, since at a shell
diameter of 6 mm it exhibits a crowding of the
adoral sutures, which is generally accepted as
indicating maturity or geronticism in an
ammonoid (Miller 1947, p. 18).

Two of the other limestones in the Woolaga
Creek area contain small rare specimens of
gastropods, pelecypods and crinoids which may
be dwarfed.

(iii) Environment of Deposition. — There is
little doubt that the Holmwood Shale accumu-
lated in a marine environment of restricted
circulation. Woolnough (1937, 1938) initiated

♦Balme, B. E. (1957). — Upper Palaeozoic microfloras in
sediments from the Lake Phillioson Bore, South
Australia. Aust. J. Sci. 20: 61-62.

16

the hypothesis that the formation was deposited
in a barred basin, and although some details
of his original theory are debatable, subsequent
authors are in general agreement with the basic
concept advanced.

In the Woolaga Creek and Irwin River areas,
the Holm wood Shale contains abundant jarosite,
together with gypsum and alunite. These three
minerals are almost certainly of secondary
origin, resulting from the breakdown of primary
pyrite (or marcasite).

In outcrop, always considerably weathered,
the Holmwood Shale is pale grey to greyish-black,
and does not generally appear to be carbonaceous.
However, spoil from bores in the area shows it
to be black and appreciably carbonaceous.

Most black shales are believed to have accumu-
lated under conditions of restricted circulation
(Twenhofel 1950, p. 337) . Under such conditions,
iron sulphide is precipitated in the stagnant
waters deoxygenated by the bacterial decay of
organic matter; benthonic life is usually absent.

Thus, on the evidence of its barrenness of
fossils, and its almost certain primary content of
pyrite (or marcasite) and carbonaceous matter,
the Holmwood Shale was deposited in a basin
that did not communicate freely with the sea,
i.e. a barred basin.

Woolnough (1937, 1938) maintained that the
absence of fossils in the formation was due to
the high salinity of the basin, resulting from a
contemporary arid climate. According to him,
the presence of Metalegoceras jacksoni (in the
Beckett Member) was due to a single catas-
trophe such as a violent storm breaking over the
bar. Clarke et. al. (1951) considered that the
Holmwood Shale was deposited in a barred basin
under cool climatic conditions, although they
thought it probable that the sea became shal-
lower and warmer in late Holmwood times with
evaporation resulting in the primary precipita-
tion of gypsum.

There is no need to invoke, and there is no
evidence for, the prevalence of a hot arid climate,
particularly when the likelihood is considered of
the gypsum being secondary in origin. While
excessive salinity could account for a restriction
or absence of animal life, so equally could the
toxic, reducing conditions of a barred basin.
Erratic boulders in the Holmwood Shale in the
area under consideration point to deposition by
floating ice and hence to a cool climate.

The Woolaga Limestone Member records a
brief, unique stage in the faunally unfavourable
Holmwood history. It represents a time during
which a normal marine fauna was able to estab-
lish itself in fairly quiet waters or in lime muds
accumulating there. The fossil debris appears
to be biocoenotic because there is little evidence
of abrasion of the fossils and because of the
presence of abundant serpulids. The matrix in
which the fossils are enclosed was probably a
fine, highly calcareous mud, which has, however,
undergone profound diagenetic changes. These
include intrastratal solution (producing vugs),
authigenesis (resulting in reorganization of
primary calcite) and diagenetic metasomatism
(silicification) .

The member was probably deposited under
normal shallow-water, marine conditions. Waves
and currents must have been sufficiently active

to cause some penecontemporaneous erosion of
the lime muds (as evidenced by intraformational
pebbles and granules) and the dissociation of the
crinoidal skeletons, and to provide sufficient
aeration to fulfil the needs of a thriving inverte-
brate fauna.

The other limestones occurring stratigraphic -
ally above and below the Woolaga Limestone
Member, are far less continuous and appear to
represent similar, but more localized interludes
of lime mud deposition. They were accompanied
by few organisms — viz. sponges, foraminifera,
gastropods, pelecypods and crinoids. Some of
the limestones may be merely large irregular
calcareous concretions. They have not been
diagenetically altered to the same extent as the
Woolaga Limestone Member.

The structural framework of the postulated
barred basin, and its precise boundaries and
dimensions, are rather obscure at present. To
the north, the Greenough Block of the
Northampton-Geraldton district, and the Car-
randibby Range at the south-eastern end of
the Carnarvon Basin, are both prominent
occurrences of Archaean rocks. Furthermore,
geophysical work has shown them to be con-
nected by a belt of shallow basement (McWhae
et al. 1958). Hence, the basin was probably
landlocked to the north. The eastern boundary
of the basin was marked by the Archaean com-
plex to the east of the Darling Fault. However,
any theories regarding the western and south-
ern limits of the basin, and its connection to
the open ocean, must be regarded, at this stage,
as purely conjectural.

High Cliff Sandstone

(i) Stratigraphy . — Clarke et al. (1951) pro-
posed the name High Cliff Sandstone for an
unfossiliferous sandy sequence, which is well-
exposed at High Cliff (on the North Irwin River) ,
where the type section is located. According to
P. E. Playford and S. P. Willmott in McWhae
et al. (1958), the formation attains a thickness
of 79 feet at the type locality.

An outstanding characteristic of the High
Cliff Sandstone in the Woolaga Creek area is
the presence of an abundant fauna of marine
invertebrates in its basal part. A boulder bed,
discovered in the middle of the formation, is
another feature of interest. The High Cliff
Sandstone is thicker along Woolaga Creek than
in the type area.

The reference section along Woolaga Creek
extends from (629829) to (632832). The follow-
ing is a description of this section.

Irwin River Coal Measures (404 feet)

High Cliff Sandstone (102 feet):

Unit. Thickness

feet.

3. Sandstone, quartzose, argillaceous, white
with occasional minor red mottling; pre-
dominantly medium- and fine-grained,
less commonly coarse-grained; moder-
ately to well-sorted; quartz grains sub-
rounded; poorly bedded, rarely cross-
bedded; indurated vertical joints
common in variable directions; weathered
surface ferruginized, pale brown in
colour; sporadic bands up to 6 inches
thick of white, very coarse-grained, ill-
sorted sandstone and conglomerate; a #

17

boulder bed occurs 24 feet above the
base of the unit as a rubbly outcrop of
boulders, cobbles and pebbles of gneiss,
quartzite, pegmatite, chert, and silici-
fied breccia, which are enclosed within
a matrix of very coarse-grained sand-
stone; the thickness of this bed is about
5 feet; 58 feet above base of unit is a
normal fault (exposed high on the
north bank of Woolaga Creek at 632831)
of indeterminate but probably not large
displacement; the fault plane is silici-
fied, striking at 137° with an north-
easterly dip of 63°. Outcrop varies from

loose boulders to cliff exposures 71

2. Sandstone, red-brown, ferruginous, feld-
spathic, fine- to medium -grained; fairly
well sorted; sub -rounded to angular
grains; massively bedded; ferruginous
concretions up to 9 inches in diameter;
many boulders fossiliferous, some of
them richly so, containing brachiopods,
pelecypods, gastropods, bryozoans and
corals; fossils ferruginized. Bouldery

outcrop 27

1. Sandstone, pale yellowish-grey, fine-
grained, silty, micaceous, poorly bedded;
thin band of brown ferruginous sand-
stone at base of unit 4

Holmwood Shale (435 feet +).

As described above, the fossiliferous ferru-
ginous part of the High Cliff Sandstone crops
out as loose boulders in the reference section
along Woolaga Creek. However, in the eroded
track at (632826), adjacent to the site of the
demolished “Glendevon” homestead, the fos-
siliferous sandstone occurs as six thin, red-
brown, lenticular beds intercalated within the
fine- to medium -grained white sandstone which
is characteristic of -the bulk of the formation.
This basal part of the High Cliff Sandstone
crops out along the strike only as boulders of
the ferruginous, fossiliferous sandstone on the
western slope of the cuesta — immediately south
of the eroded track and also, farther north,
between the same track and Woolaga Creek. It
is apparent, therefore, that the ferruginous,
fossiliferous sandstone is more resistant to
erosion than the white sandstone with which
it is interbedded. The prominent cuesta prob-
ably owes its form to this resistant basal part
of the High Cliff Sandstone immediately over-
lying the much softer Holmwood Shale, and it
is noteworthy that the fossiliferous lithology
is practically unknown beyond the extent of
this striking landform. At (626833), the most
northerly expression of the cuesta, fossils are
less frequent in the boulders, which are also
less ferruginous than farther south. The
fossiliferous High Cliff Sandstone has been
traced for one and a quarter miles along the
strike

Elsewhere, at (596864) and at (651806), the
basal part of the formation consists of unfos-
siliferous, white sandstone, although a precise
contact with the Holmwood Shale is not
exposed.

The question arises: is the fossiliferous,

ferruginous sandstone simply a southerly facies
variant of the richly fossiliferous Fossil Cliff
Formation of the Irwin River area, or may it
be validly assigned to the basal part of the
High Cliff Sandstone?

Fairbridge (1952) considered that this fos-
siliferous sandstone at Woolaga Creek and also
the “Mingenew Beds” (now elevated to forma-

tion status in McWhae et al. 1958), cropping
out on Erregulla Springs property near
Mingenew, were equivalents of the Fossil Cliff
Formation. However, Fairbridge does not put
forward any evidence for his correlation.

Johnson et al. (1954), while including the fos-
siliferous sandstone at Woolaga Creek in the
High Cliff Sandstone, were aware of the pos-
sibility that its contained fauna may be equiva-
lent to that of the Fossil Cliff Formation.

McWhae et al. (1958), without explanation
or discussion, assign the fossiliferous unit in
question to the base of the High Cliff Sand-
stone.

In addition to the fact that the actual fos-
siliferous facies is sandy, it is intercalated with-
in the white sandstone, typical of the High
Cliff Sandstone in both the Woolaga Creek and
Irwin River areas. Thus, an assignment of
the unit in question to the High Cliff Sand-
stone is indicated.

Further, Dickins (1957) believes that the
Woolaga Creek fauna contains forms that
are younger than those from the Fossil Cliff
Formation.

If the equivalent of the Fossil Cliff Forma-
tion is indeed absent from the Woolaga Creek
area, one might expect to find here a discon-
formity between the Holmwood Shale and the
High Cliff Sandstone. However, the relation-
ship between the two formations appears to be
one of conformity at both exposures of the
contact (629829 and 632826). A significant
point in this connexion is that, in the type
area, the Fossil Cliff facies is rather lenticular
and has lithological similarities with the under-
lying Holmwood Shale. Indeed, Johnson et al.
(1954) rejected the Fossil Cliff Formation as
a valid formation, and included it within the
Holmwood Shale. Thus, it could be that the
Fossil Cliff Formation, where present, is simply
a rather large fossiliferous lenticle in the up-
per part of the Holmwood Shale, representative
of a period during which conditions favoured
the establishment of a prolific marine fauna.
Farther south, however, in the Woolaga Creek
area, the contemporary environment could have
been unfavourable for abundant life, and as a
result the Fossil Cliff Formation could be repre-
sented here by comparatively barren Holmwood
Shale. Under these circumstances, a conform-
able relationship between the Holmwood Shale
and the High Cliff Sandstone would not be un-
expected.

On the evidence available, therefore, it is
justifiable to include the fossiliferous sand-
stone within the basal part of the High Cliff
Sandstone.

Current opinion (based on the work of Mr.
J. M. Dickins) is that the Mingenew Forma-
tion is the youngest unit in the Permian suc-
cession of the Irwin River area (McWhae et al.
1958). The fauna of the formation is Artins-
kian in age.

A conformable contact between the High Cliff
Sandstone and the overlying Irwin River Coal
Measures is exposed in a small creek in the
reference section at (632832). At this point,
a minor strike fault with east-block-down move-
ment has slightly affected both the basal
Irwin River Coal Measures and the underlying

18

High Cliff Sandstone. In three localities
(638819), (597865) and (613854) the two forma-
tions have been brought into abutment by fault-
ing. At (638819), a prominent ferruginized
fault zone is exposed on the breakaway slope.
On the west side of the fault, medium- and
coarse-grained, white and red sandstones (High
Cliff Sandstone), exhibiting minor cross-bed-
ding, dip at 17° to the north-east. On the
eastern side, sediments of the Irwin River Coal
Measures consisting of pure white, well-bedded
siltstones and fine- to medium-grained sand-
stones have a north-easterly dip of 30° adjacent
to the fault zone; 55 feet farther east their at-
titude has flattened out to a dip of 8° in the
same direction. There was some doubt whe-
ther these latter sediments belonged to the
Irwin River Coal Measures as they look rather
similar to the adjacent High Cliff Sandstone,
but the chocolate siltstones underlying them in
gullies below the breakaway are typical Coal
Measures lithology. Thus, this fault, with a
trend of 168° has an east-block-down move-
ment. At (597865), a fault occupies a nar-
row elongate topographic low between an out-
crop of cross-bedded, white High Cliff Sand-
stone on the northern slope of a small hill,
and a breakaway, immediately north of this
hill, which exposes typical plant-bearing sedi-
ments of the Irwin River Coal Measures on
its western point. On two small adjacent low
rises at the immediate base of this breakaway,
the sandstones, carbonaceous shales and silt-
stones of the Coal Measures show strong evi-
dence of upturning against the* fault with an
average north-north-easterly dip of 40°. The
exposure at (613854) is poor, but appears to
represent another fault contact between the
two formations.

Along the reference section described above,
the measured thickness of the High Cliff Sand-
stone is possibly somewhat lower than the true
thickness on account of the effect of strike
faulting. Thus, the fault at (632831) would
have the effect of lessening the exposed thick-
ness of the formation. However, the figure
given for the section, viz. 102 feet, is less than
half that stated by Johnson et al. (1954) for
the thickness of the formation at Woolaga
Creek, and the present author finds their figure
(250 feet) quite untenable.

A water bore, sited at (638821) close to the
top of the High Cliff Sandstone, penetrated
116 feet of this formation before passing into
the Holmwood Shale, and was abandoned at a
depth of 124 feet. Two other unsuccessful
bores for water at (635824) and (654805) passed
through 106 feet and 68 feet respectively of
High Cliff Sandstone before encountering the
Holmwood Shale in which they were abandoned
at respective depths of 108 feet and 80 feet.
As the dip of the High Cliff Sandstone is only
of the order of 6°, the above vertical depths
closely approximate to stratigraphical thick-
nesses.

Apart from the presence of marine fossils in
its basal part and of the boulder bed strati-
graphically higher in the section, the exposures
of the High Cliff Sandstone in the Woolaga
Creek area are lithologically similar to those
of the type area. Characteristically, the forma-

tion consists of medium-, fine-, and sometimes
coarse-grained white sandstone, which contains
occasional conglomeratic lenses. Cross-bedding
is less a feature of the High Cliff Sandstone at
Woolaga Creek than in the Irwin River area.

(ii) Bio stratigraphy . — Specimens from the

fossiliferous, basal 30 feet of the High Cliff
Sandstone, collected by the present author and
by parties of senior students from the Depart-
ment of Geology, University of Western Aus-
tralia, were examined recently by Mr. J. M.
Dickins of the Bureau of Mineral Resources,
Canberra.

The results of his studies of the brachiopods,
pelecypods and gastropods — which are the
dominant groups in the fauna — are embodied
in an unpublished report (Dickins 1957).

The following identifications are listed in this
report :

Brachiopoda

Linoprcductus (Cancrinella) cf. lyoni (Prendergast)
1942.

Linoproductus (Cancrinella) sp.

Linoproductus (Cancrinella) sp. ind.

Aulosteges cf. ingens Hosking 1931.

Aulosteges sp. ind.

“Chonetes ,> sp.

Permorthotetes sp.

‘Dielasma’ > sp. nov. A.

“Dielasma” sp. nov. B.

“Martiniopsis” sp. A.

Phricidothyris ? sp.

Cleiothyridina sp.

Cleiothyridina sp. ind.

Spiriferidae sp. nov.

Neospirifer sp. nov. A.

Neospirifer sp. nov. A. ?

Neospirifer sp. nov. B.

Neospirifer sp. ind.

Pelecypoda

Parallelodon sp. nov.

Parallelodon sp. ind.

Astartila ? sp. nov.

Astartila ? sp. ind.

Stutchburia cf. variabilis Dickins, in press.

Stutchburia ? sp. ind.

Atomodesma cf. mytiloides Beyrich 1865.

Schizodus sp.

Oriocrassatella cf. stokesi Etheridge Jnr. 1907.

Streblochondria sp. ind.

Streblochondria ? sp.

• Aviculopecten cf. tenuicollis (Dana) 1847.

Gastropoda

j S eller ophon sp.

Bellerophon sp. ind.

Baylea ? sp.

Dickins notes the distinctiveness of this fauna
from that of the Woolaga Limestone Member
of the Holmwood Shale. Further, he considers
that the High Cliff Sandstone fauna as a whole
is distinct from both the fauna of the Mingenew
Formation and the fauna from Carynginia
Gully, which was assigned recently to the
Fossil Cliff Formation by Dickins and Thomas
(1957).

Dickins states that the fauna of the High
Cliff Sandstone contains fossils which are
younger than those from the Fossil Cliff Forma-
tion, and concludes that it is probably repre-
sentative of a marine horizon intermediate be-
tween the Callytharra Formation (equivalent
to the Fossil Cliff Formation) and the Made-
line Formation which are both developed in the
Carnarvon Basin.

Thus the High Cliff Sandstone is of Artins-
kian age.

(iii) Environment of Deposition . — Factors

which are important when synthesizing the de-

19

positional environment of the High Cliff Sand-
stone are as follows: —

1. The fossiliferous, basal part of the forma-
tion, though lenticular, indicates a marine en-
vironment during at least early High Cliff times.

2. Although sorting may be classed as only
moderate in its lower part, the High Cliff Sand-
stone is in general notably well-sorted. This
degree of size -sorting is suggestive of the rather
prolonged activity of waves and currents as in
a near-shore marine environment. Stetson and
Upson (1937, p. 57) state an average coefficient
of sorting of 1.45 foj* well-sorted, near-shore
sediments; and in fact the sorting coefficients
obtained for two typical specimens of High
Cliff Sandstone (39279 and 39280) are remark-
ably close to this value (1.44 and 1.41 respec-
tively).

3. Sediments of similar lithology and strati-
graphic position occur elsewhere in the
Permian of Western Australia. These forma-
tions, with which the High Cliff Sandstone is
correlated, are the Moogooloo Sandstone of the
Carnarvon Basin and the Poole Sandstone of
the northern part of the Canning Basin. Such
a laterally extensive sequence of well-sorted
quartzose sands could be reasonably ascribed
only to the shallow-water marine conditions of
a stable shelf. It is significant also that
McWhae et al. (1958) report the presence of
a marine fauna of brachiopods and bryozoans
in the basal part of the Moogooloo Sandstone.

Although inconclusive in themselves, these
factors taken together constitute strong evidence
that the High Cliff Sandstone was deposited in
a shallow-water marine environment.

The presence of allogenic feldspar in the
basal part and its absence higher in the forma-
tion (where quartzose sandstones predominate)
suggests a decrease in relief of the hinterland
concomitant with the advancement of High Cliff
time.

The ferruginization of the lenticular, fossili-
ferous sandstone is almost certainly an effect
of lateritization. It appears that, in Western
Australia, lime-bearing sediments are particu-
larly susceptible to replacement by iron. P. E.
Playford (1954) has described the pronounced
effect of lateritization on the Newmarracarra
Limestone which occurs in the Geraldton dis-
trict. Similarly, the fossiliferous High Cliff
Sandstone is completely leached of calcium
carbonate, with the fossils represented only by
haematitic moulds and with the matrix of the
rock heavily impregnated with iron. It would
appear that, prior to lateritization, these fossili-
ferous lenticles consisted of calcareous, argil-
laceous sandstone.

Irwin River Coal Measures

(i) Stratigraphy . — The formation name Irwin
River Coal Measures was first proposed by
Clarke et al. (1951) for the succession of
“shales and sandstones with some interbedded
coal seams” resting conformably between the
High Cliff Sandstone and the Carynginia
Formation. The type section is along the North
Irwin River. Subsequently the usage of Clarke
and his co-authors was modified by Johnson
et al. (1954), who encountered difficulties in
separating the Irwin River Coal Measures from

the Carynginia Formation particularly in the
Woolaga Creek area. Johnson and his co-
authors proposed to combine the two units into
the one formation, which they termed the Irwin
River Coal Measures.

P. E. Playford and S. P. Willmott in McWhae
et al. (1958) reaffirm the validity of the nomen-
clature of Clarke et al. (1951), and record a
thickness of 217 feet for the type section of
the Irwin River Coal Measures.

Although the boundary between the Irwin
River Coal Measures and the Carynginia
Formation is transitional in the Woolaga Creek
area, the present author considers that the
two units are sufficiently distinctive in this area
to justify their recognition as separate forma-
tions. A satisfactory contact was discovered at
(641832). The author cannot agree with
Johnson et al. (1954, p. 49) that the two units
were deposited in a similar environment.

In the Woolaga Creek area, the Irwin River
Coal Measures are notably less carbonaceous,
and attain a greater thickness than in the type
locality.

The Woolaga Creek reference section of the
Irwin River Coal Measures commences at
(632832) and continues to (641832). The
following is a description of this section.

Carynginia Formation (844 feet)

Irwin River Coal Measures (404 feet) :

Unit Thickness

Feet

28. Composite lithological unit. Sand-
stone, mottled red, grey and yel-
low, ferruginous, micaceous, fine- to
medium-grained, friable, moderately
sorted, commencing at 6 feet above
base of unit are lenticular intercala-
tions of siltstone, grey-black, carbona-
ceous (increasing towards top) and
of siltstone, red and yellow, ferru-
ginous, resistant; an ill-sorted lenti-
cular band of conglomerate occurs
20 inches below the top of the unit;
the uppermost part of the unit com-
prises a resistant 4-inch band of ir-
regularly intercalated yellow and
grey, medium-grained sandstone,
bright red siltstone and black, car-
bonaceous, clayey siltstone; weathered
cobbles and boulders occur within
the upper 6 inches of the unit. ... 9

27. No outcrop 16

26. Interbedded sandstone, pale brown,
fine-grained, and siltstone, yellow,
purplish-red, brown and chocolate,
ferruginous, jarositic. Rubbly out-
crop 1

25. Sandstone, yellow to brownish-yellow,
micaceous, ferruginous, fine- to
medium-grained, friable, moderately
sorted, poorly bedded, sometimes crcss-
bedded; some relatively resistant hori-
zons of sandstone, brown, ferrugi-
nous, micaceous; irregular thin in-
tercalations of carbonaceous material
(plant remains), and red-brown, fine-
grained sandstone and siltstone as
resistant bands up to 2 inches thick;
the upper 10 feet of the unit is
non -carbonaceous; rounded erratic
boulders up to 24 feet in diameter
occur 3 feet above base and else-
where sporadically in the unit 20

24. Rhythmically alternating sequence.
Predominantly siltstone, chocolate,
micaceous carbonaceous, shaly, rich
in plant fossils; intercalated with
more or less regular bands (up to
4 inches thick) of sandstone, yellow-
brown, ferruginous, micaceous, quartz-
ose, very fine to medium -grained,
friable, poorly sorted, some plant fos-
sils, and sandstone, pale grey, mica-

20

ceous, quartzose, fine-grained, friable,
well -sorted; unit becomes slightly
less carbonaceous, less silty, and
more ferruginous towards top; promi-
nent joints trending 10° with a west-
erly dip of 80°, and 90° with a south-
erly dip of 80° 6

Unit 24 and the lower part of unit
25 exhibit large-scale slumping pheno-
mena (Plate 1, 2). This is particu-
larly well shown by the broadly un-
dulating boundary between the two
units. Individual beds within the
slumped strata show a high degree
of contortion.

23. No outcrop 58

22. Siltstone, brownish-grey, micaceous,
ferruginous, friable, thin-bedded,

cross-bedded. 8

21. Siltstone, black, clayey, ofter highly
carbonaceous, with thin yellowish
sandy ferruginous bands; grading up
into a less carbonaceous, ferruginous
siltstone, brownish-grey with thin
black bands, friable; plant fossils;
thin-bedded with cross-bedding on

minor scale 6£

20. Sandstone, grey and yellow, ferrugi-
nous, fine-grained, friable 1£

19. Sandstone, greyish-white, chocolate
and yellowish-brown, silty, micaceous,
ferruginous, very fine grained, friable,
thin-bedded; intercalated irregularly
with siltstone, greyish-black and
chocolate, carbonaceous, micaceous,
friable, plant fossils; brown ferrugi-
nous concretions (up to 1 inch in
diameter) in upper part; 2^ -inch band
of friable, highly weathered, black
coaly material constitutes the upper-
most part of unit; outcrop has white,

salty incrustation. 6

18. No outcrop 6

17. Siltstone, yellow, micaceous, ferru-
ginous, friable, thin -bedded; passing
into claystone, black, red and white,
carbonaceous, ferruginous, massively
bedded, ferruginous bands resistant

and concretionary 3

16. Claystone, red and white, very
soft, massively bedded, containing
plant fossils, with thin lenses of

black, carbonaceous siltstone 2\

15. Sandstone, white, quartzose, coarse-
grained, friable, moderately sorted,
sub-angular grains, cross-bedded; con-
tains small, irregularly shaped frag-
ments of grey siltstone. 6

14. Claystone, grey, red and white, car-
bonaceous, ferruginous, friable, mas-
sively bedded, rich in plant fossils 2\

13. Siltstone, alternating cholocate-grey
and yellow-brown, shaly, carbona-
ceous and ferruginous, thin-bedded,

containing plant fossils. 10£

12. Sandstone, greyish-white, micaceous,
fine-grained, friable, moderately sorted,

cross-bedded. ... 21

\1. Shale, chocolate-grey, micaceous, car-
bonaceous, thin-bedded, containing
plant fossils; thin intercalated bands
of siltstone, yellow, red and brown,
ferruginous, resistant, rich in plant
fossils; 4 feet above base of unit is
a 4-inch band of sandstone, white,
feldspathic, coarse-grained, poorly
sorted, massively bedded, angular

grains. 6

10. Sandstone, greyish-white with minor
pale brown mottling, micaceous, fine-
grained, friable, moderately sorted,
poorly bedded; thin (up to 1 inch)
bands of grey siltstone near top of

unit 3

9. Sandstone, greyish-white and pale
yellow-brown, micaceous, ferruginous,
fine-to very fine-grained, with inter-
calated silty horizons, cross-bedded,

friable. ‘ 16

8. Shale, black, carbonaceous, thin-bed-

ded, rich in plant fossils 6

7. No outcrop 18

6. Siltstone and sandstone, very fine-
grained, grey, greyish-white and yel-
low, micaceous, friable, thin-to thick-

bedded, plant fossils in many hori-
zons; rare thin, lenticular, sandy

bands. 61

5. Sandstone, very pale brown, feld-
spathic, coarse- to very coarse-grained,
ill-sorted, angular grains, massively
bedded; uppermost 8 inches of unit
consists of siltstone, purplish-red,
sandy, feldspathic, non-friable, poorly
sorted, ripple-marked with long axes
of ripple-marks trending 35°, forms a

resistant slabby capping to unit 7

4. Sandstone, yellow-brown, ferruginous,
micaceous, very fine-grained, friable,

cross-bedded. 3

3. No outcrop 60

2. Sandstone, white, weathering pale

brown, quartzose, medium- to fine-
grained, friable, moderately sorted,
sub-rounded grains, massively bedded,
locally cross-bedded; minor thin
(3-inch) bands of coarse sandstone. 37

1. Siltstone, greyish-black, carbonaceous,
friable, thin-bedded, containing
abundant plant fossils; thin inter-
calations of siltstone, yellow and
brown, ferruginous, weathering to
small thin slabs, and of sandstone,
pale yellow and brown, medium- to
coarse-grained, quartzose, friable,
poorly sorted, often lenticular; at
base of unit is a thin (3-inch) band
of siltstone, reddish-brown, ferru-
ginous, resistant, bearing plant fossils. 17

High Cliff Sandstone (102 feet).

The Irwin River Coal Measures in the Woolaga
Creek area comprise a remarkably varied
sequence of interbedded very fine to coarse-
grained sandstones, siltstones and claystones
containing plant fossils at many horizons. The
sandstones are generally ill-sorted, frequently
cross-bedded, occasionally ripple-marked, and
are white, yellow, grey and red in colour. The
siltstones and claystones are sometimes shaly,
frequently micaceous, ferruginous and carbon-
aceous, with varying colours of white, grey,
chocolate, yellow, brown, red and black.

Rapid lateral and vertical changes in lithology
characterize the Irwin River Coal Measures,
particularly in the lower part. Excellent ex-
posures occur along Woolaga Creek and its
tributaries in the general vicinity of (638834).
Also, the formation is well-exposed along the
breakaways at (643820), whereas farther south
outcrops are intermittent and generally poor.
To the north of Woolaga Creek, good outcrops
occur on the northerly slopes of the mesa at
(629837), and on breakaways north of Mt. Budd
in the north-western part of the area.

The sequence is decidedly less carbonaceous
than in the type area. Richly carbonaceous
facies are restricted to two thin beds, each about
1 foot in thickness, which crop out on a sub-
sidiary rise below the breakaway at (643820);
and to a thin seam of coaly material (top of
unit 19 of the reference section) in an undercut
cliff exposure at (636835), a prominent bend in
Woolaga Creek.

Plant fossils, mainly leaf impressions, occur
abundantly throughout the formation. Good
plant fossil localities include (634834) (632832)
(629837), (632835), 635835), (636832),’ (639827)
(643820), (638834) and (596866). The only other
fossils found in the Irwin River Coal Measures
were worm tracks occurring at (627845), where
they form a ramifying network in reddish-brown
fine-grained sandstone.

21

The upper Irwin River Coal Measures show
large-scale slumping along Woolaga Creek in the
vicinity of (638834). This occurs in siltstones
and fine-grained sandstones (units 24 and 25 of
the reference section). The strata are broadly
folded with resultant marked variations in strike
(Plate 1, 2) and merge upwards into undeformed
strata. Furthermore, there is extreme contortion
of the laminae within individual beds of the
slumped strata. Hence we have penecontempor-
aneous soft-sediment folding on both large and
small scale.

Erratic boulders of gneiss, granite and quartz-
ite occur in the upper Irwin River Coal Measures.
These erratics are found on the east bank of
Woolaga Creek at (639834) in unit 25 of the
reference section. They are as much as 2J feet
in diameter and are not associated with boulder
clay. Fairbridge (1952) noted the presence of
“dumped” erratics in the Irwin River Coal
Measures and concluded that they had been
depOwSited from floating vegetation rather than
from floating ice.

Ferruginous concretions occur in white silt-
stone and fine-grained sandstone in a creek at
(621843). These sub-spherical bodies average
3 inches in diameter, and are composed of yellow-
brown iron oxide, with a central core of finely
oolitic jarosite and minor gypsum. They appear
to be a product of weathering, resulting from the
chemical decomposition of concretionary pyrite
or marcasite.

Strike faults having small throws are fairly
common. The most important are those, already
described, which have thrown the High Cliff
sandstone against the Coal Measures. Rather
poorly exposed, lateritized siltstones of the
Irwin River Coal Measures are deformed into
a drag syncline within a distance of one quarter
of a mile adjacent to the Darling Fault. This
structure occurs in the south-eastern part of
the area and is displayed exceptionally well by
the air photographs.

The contact between the Irwin River Coal
Measures and the underlying High Cliff Sand-
stone is conformable in the reference section.
In two localities (641832) and (595873), the
Irwin River Coal Measures are overlain transi-
tionally and conformably by the Carynginia
Formation.

The Irwin River Coal Measures attain a
thickness of 404 feet in the Woolaga Creek
area. This is almost twice the thickness of the
formation in its type area.

(ii) Biostratigraphy. — The plant fossils of
the Irwin River Coal Measures are typical
representatives of the Permian Gondwana flora.
Glossopteris is the most abundant genus, and
other genera identified by the author include
Splienopteris, Sphenophyllum, Bothrodendron,
Phyllotheca and Gangamopteris. All of these
genera have been recorded from the type area
of the Irwin River Coal Measures (Clarke et al.
1951).

Palynological studies reported by McWhae
et al. (1958) on the rich microflora present in
the formation suggest an Artinskian age. These
authors correlate the Irwin River Coal Measures
with the Collie Formation of the Collie and
Muja Basins.

(iii) Environment of Deposition. — The Irwin
River Coal Measures are considered to repre-
sent a composite fluviatile and paludal deposit,
which possibly accumulated as the topset com-
ponent of a delta.

This mode of origin is suggested by the
following attributes of the formation: — The
remarkably rapid alternation of rock types and
their individual lateral impersistence has al-
ready been discussed; this feature is charac-
teristic of fluvial sediments. The abundance of
plant material throughout and the absence of
marine fossils is strong evidence for a con-
tinental environment of deposition. Added
confirmation of this is found in the fact that
the plant fossils are mainly well-preserved
leaves, which obviously could not have survived
much transportation and must therefore have
been deposited close to their habitat. The
large-scale cross-bedding and ripple -marking
developed by the Irwin River Coal Measures
are further characteristic of fluviatile deposits.
Worm tracks present in the formation point
to shallow-water conditions.

The typical yellow, brown and red colours of
some of the strata are due to their content of
trivalent iron compounds. A significant point
in this connexion is that bore samples of the
Irwin River Coal Measures are generally grey
or black, and sometimes contain pyrite
(Johnson et al. 1954, pp. 94-100). This suggests
that the bright colours of the sediments in out-
crop have probably resulted mainly from
weathering processes. With abundant organic
matter present in the depositional environment
it is probable that conditions would have been
favourable for the precipitation of iron sul-
phide, particularly in swamps on the flood
plain. Furthermore, primary pyrite (or mar-
casite), when subjected to weathering, would
readily decompose to form ferric compounds.
Thus, although no marcasite or pyrite were
found in outcrop, many of the sediments con-
taining abundant plant impressions are also
rich in ferric compounds. Some ferruginous
concretions present in the formation appear to
be pseudomorphous after pyrite or marcasite.
On the other hand, some of the iron could have
been deposited primarily as ferric hydroxide
(limonite) and iron carbonate, together with
the iron sulphide, under paludal conditions. It
should also be mentioned that the red-brown
colour of sediments lying close to the Victoria
Plateau level may usually be attributed to the
effects of lateritization.

The prevailing easterly dip is due to subse-
quent tectonism and is not a primary feature
of the Coal Measures sediments, which must
have been almost horizontal when deposited.
Hence if the environment was deltaic, as is
indicated, the sediments could only represent
topset beds within this environment.

The upper part of the Irwin River Coal
Measures has smaller scale cross-bedding and
greater lateral and vertical persistence of
strata, which are of somewhat finer grain.
This seems to suggest a transition to shallow-
marine or lagoonal conditions in late Coal
Measures time. The interesting but problemati-

22

•cal erratic boulders in the formation may have
been deposited from either floating ice or float-
ing vegetation.

The generally well stratified nature of the
formation and its well-sorted sandy inter-
calations suggest that most of the sediment has
been transported some considerable distance
and distributed in successive layers over the
delta. The rarity of conglomerate, or even
conglomeratic sandstone, also indicates a
distant source for the sediments, while the
presence of fresh feldspar in the sandstones
is evidence of fairly rapid erosion in the source
area.

Carynginia Formation .

(i) Stratigraphy . — Clarke et al. (1951) origin-
ally termed this formation the “Carynginia
Shale.” However, as there is little shale in the
unit, P. E. Playford and S. P. Willmott (in
McWhae et al. 1958) have altered the name to
Carynginia Formation. According to Clarke
and his co-authors, the Carynginia Formation
attains a thickness of 800 feet in the type
locality, which is situated in Carynginia Gully,
a tributary of the North Irwin River.

The Carynginia Formation appears .to be
more sandy and better exposed at Woolaga
Creek than in the Irwin River area. It is
interesting to note that, in both areas, erratic
boulders occur in the basal part of the forma-
tion. The Carynginia Formation is somewhat
thicker in the Woolaga Creek area than in the
type area. Lithologically, the unit often
resembles the Holmwood Shale.

The reference section in the Woolaga Creek
area extends from (641832) to Red Hill
(647838). The following is a description of this
section.

Wagina Sandstone (796 feet +)
Carynginia Formation (844 feet) :
Unit

7. Siltstone, chocolate -black weathering
pale grey, jarositic, micaceous, clayey,
thin-bedded; bands (up to 1 foot
thick) of sandstone, white and grey,
medium-grained, silty, fairly well
sorted, rounded grains; thin inter-
calations of siltstone, yellow-brown,

ferruginous, resistant

6. No outcrop

5. Composite lithological sequence, with
small-scale slumping in lower part
Interbedded siltstone, grey and choco-
late-black, weathering pale grey jaro-
sitic, micaceous, shaly, thinly to
massively bedded; fine- to very fine-
grained sandstone and siltstone, grey,
yellow and red-brown, ferruginous,
micaceous, friable and non -friable,
locally cross-bedded, often fissile; where
richly ferruginous, the sandstones and
siltstones are very resistant to weather-
ing and stand out as projecting
ledges. Commencing 53 feet above
base of unit are thin (9-inch), freely
intercalated, often lenticular bands of
sandstone, white, feldspathic, coarse-
grained to conglomeratic, non-fnable
to friable, fairly well sorted, sub-
rounded grains, massively Redded,
often broadly ripple -marked. Striking
differential compaction effects are
seen with sandstone and associated
siltstone. Seventy feet above base of
unit is a prominent 2 -inch band of
ferruginous siltstone bearing worm
tracks and oscillation ripple-marks,

Thickness
Feet

84

123

the ripple-marks have a wave length
of 9 inches, amplitude of £-inch, and

trend 10° —

4. Siltstone, grey, chocolate-black and
brown, jarositic, micaceous, clayey,
friable, thin -bedded; minor thin in-
tercalations of siltstone, red-brown,
ferruginous, micaceous, resistant,
weathering to small thin slabs; rare
lenticular bands (up to 2 feet thick)
of sandstone, pale brown and yellow,
slightly ferruginous, medium- to

coarse-grained, moderately sorted,
rounded grains, massively bedded.

Sporadic outcrop .. 427

3. Sandstone, brown, pale grey and
red, feldspathic, silty, fine- to very
coarse- grained, well-sorted, sub-
rounded grains, massively bedded;
freely and irregularly intercalated
with siltstone, chocolate-black weather-
ing grey, jarositic, carbonaceous con-
taining thin lenses of siltstone, red,
ferruginous, resistant. Unit more

more sandy in upper part 9

2. Shale, chocolate-black, weathering
grey, richly jarositic, carbonaceous,
micaceous, silty, thin-bedded (0.5
cm.); with intercalated regular bands
(up to inches thick) of siltstone,
bright red and yellow-brown, ferru-
ginous, resistant, composing about
one-tenth of unit; also minor lenses
of sandstone, red and yellow, ferru-
ginous, medium- to coarse-grained,
friable, poorly sorted, insignificant in

upper part of unit. 28

1. Interbedded bands and lenses of
siltstone, chocolate-black, richly jaro-
sitic, carbonaceous, micaceous, clayey,
greasy feel, pungent odour when
freshly cut, massively bedded; and
sandstone, yellow-brown, ferruginous,
medium- to fine-grained, friable,
moderately sorted, massively bedded,
less resistant than the siltstone. In
upper part of unit is a lenticular
band (with maximum thickness of
2 feet) of sandstone, mottled white,
red and yellow, ferruginous, coarse-
grained, friable, poorly sorted, mas-
sively bedded. Pebbles, cobbles and
boulders of gneiss, granite and doler-
ite, often highly weathered, and with
maximum diameter of 1.2 feet, occur
in lower 4 feet of unit. “Dumping”
is suggested by the fact that the bed-
ding of the enclosing sediments
curves below the boulders 5

Irwin River Coal Measures (404 feet).

In the Woolaga Creek area, the Carynginia
Formation consists predominantly of grey and
black jarositic siltstones with interbedded
yellow, reddish-brown and white sandstones
and siltstones; “dumped” erratic boulders oc-
cur at the base. The jarositic siltstones are
carbonaceous in the lower part of the formation
and in places contain minor amounts of
gypsum. Ripple-marking and rather small-
scale cross-bedding are fairly common in the
unit.

The Carynginia Formation is extensively
developed and generally well exposed in the
area under consideration. There are some
particularly fine exposures along two large
adjacent tributaries of upper Woolaga Creek
in the south-eastern part of the area. Also,
where these two tributaries enter Woolaga
Creek (at 655821), the west bank of the latter
constitutes an impressive cliff section extend-
ing almost continuously along the strike for
three-eighths of a mile. The narrow elongated
mesa at (623852), immediately north of the
Mingenew-Morawa road, is composed of

23

Carynginia Formation. An excellent exposure
of the typical greyish -black, richly jarositic
siltstones of the formation occurs on the
northern point of this hill. The deep erosion
gullies in the vicinity of (638835) provide
numerous fresh exposures of the formation.
The reference section, described above, com-
prises the most nearly complete exposure of
the Carynginia Formation in the area.

In the south-eastern part of the Woolaga
Creek area, the strike of the sediments is de-
flected through a maximum angle of 145°
within one half a mile marginal to the Darling
Fault, so that here the Carynginia Formation
abuts against the Precambrian complex.

Contrasting with its transitional relationship
with the underlying Irwin River Coal Measures,
the Carynginia Formation is overlain abruptly,
but conformably, by the Wagina Sandstone.
Indeed, the contact between the Carynginia
Formation and the Wagina Sandstone is the
most readily mappable geological boundary in
the area. It is well-exposed near the top of
Red Hill (Plate 1, 3) and at several points along
a breakaway immediately to the north. The
trend of the contact at these localities is 158°
However, in the south-eastern part of the area
the same contact is markedly deflected in con-
formity with the change in strike of the sedi-
ments noted above. Thus the trend of the
Wagina Sandstone-Carynginia Formation boun-
dary is 43° along the southern escarpment at
(661832), adjacent to the Darling Fault.

The thickness of the Carynginia Formation
is 844 feet in the Woolaga Creek reference
section, which is 44 feet greater than the type
thickness in the Irwin River area.

(ii) Biostratigraphy . — The Carynginia Forma-
tion is practically unfossiliferous. Worm tracks
are sometimes present in the strata, and a
single indeterminable cast of a pelecypod
(specimen 39303) was found in greyish-white,
sandy siltstone cropping out at (653823).

The Permian age of the Carynginia Forma-
tion is unquestionable by virtue of its strati-
graphical position between the Irwin River Coal
Measures and the Wagina Sandstone, both of
which contain diagnostic Permian plant fossils.
McWhae et oL (1958) ascribe an Artinskian age
to the Carynginia Formation without present-
ing any conclusive biostratigraphical evidence.

(iii) Environment of Deposition. — The simi-
larity between the Carynginia Formation and
the Holmwood Shale indicates a similar en-
vironment of deposition for the two formations.

The Carynginia Formation contains abund-
ant jarosite and rare gypsum and is car-
bonaceous, particularly in the basal part. All
these features, as with the Holmwood Shale,
suggest that the formation accumulated under
conditions of restricted circulation, i.e., within
a barred basin.

The depositional environment was almost
certainly marine. This is indicated by the
presence of hystrichosphaerids (McWhae et al.
1958) and of a single pelecypod, discovered by
the present author. The relatively uniform
lithology of the Carynginia Formation and its
marked resemblance to the marine Holmwood
Shale also suggest marine conditions.

The erratic boulders in the basal part of
the formation pose the familiar problem as to
whether they have been deposited by floating
vegetation or by icebergs. The occurrence of
boulders in a similar stratigraphical position
in the Woolaga Creek and Irwin River sections
suggests that they have been dumped from ice-
bergs during a brief recurrence of glacial con-
ditions in early Carynginia time.

The Carynginia Formation contains inter -
bedded sandstones, which are unknown in the
Holmwood Shale. The sandstones are cross -
bedded, ripple-marked, generally well-sorted,
often feldspathic, and locally contain worm
tracks. Collectively, these factors suggest the
activity of waves and currents in a shallow -
water sea, into which both fine and subordinate
coarse sediment were being deposited.

It would seem that the “bar” responsible for
the euxinic conditions within the basin was not
as effective as in Holmwood times.

Wagina Sandstone

(i) Stratigraphy . — The name Wagina Sand-
stone was proposed by Clarke et al. (1951) for
the sequence of white and red sandstones over-
lying the Carynginia Formation. These authors
measured a maximum thickness of 300 feet in
the type section, which is located on the south
branch of the Irwin River, near Wagina Well.

The Wagina Sandstone is much thicker in
the Woolaga Creek area than in the type area.
The upper limit of the formation is unknown
as it is everywhere truncated by the Darling
Fault, or by the Victoria Plateau surface.

Plant fossils are found profusely in the
Wagina Sandstone, at a single locality in the
Woolaga Creek area (Plate 1, 4). Apart from
this occurrence, which is described below in
the reference section, the formation appears
to be unfossiliferous. Farther north, in the
Irwin River area, exceptionally well preserved
plant fossils are recorded from another isolated
horizon in the otherwise unfossiliferous Wagina
Sandstone (Clarke et al. 1951, p. 67).

The reference section in the Woolaga Creek
area commences at Red Hill (647838) and
extends eastward to the axis of the drag
syncline (654845) adjacent to the Darling

Fault. The following is a description of this
section.

Wagina Sandstone (796 feet +):

Unit Thickness

Feet

5. No outcrop. White sandy soil 202

4. Sandstone, mottled purple and white,
ferruginous, very fine-grained, non-
friable, massively bedded (basal 9
inches); succeeded by sandstone, red
with minor white banding, ferru-

ginous, quartzose, medium-to coarse-
grained, non-friable, moderately well
sorted, sub-rounded grains, massively

bedded. 12

3. Rapidly alternating sequence. Sand-
stone, white with minor yellow band-
ing, argillaceous, quartzose, coarse-
grained, sometimes conglomeratic,
poorly sorted, sub-angular grains, mas-
sively bedded; occurs in bands and
lenses ranging from £-inch to 2 feet,
but averaging 6 inches in thickness.

Siltstone and shale, mainly chocolate,
also grey and black, carbonaceous,

24

jarositic, micaceous, thin- to thick-
bedded. plant fossils abundant; oc-
curs in bands ranging from £-inch
to 6 feet in thickness, commonly 1|
feet thick. Minor thin intercala-
tions of shale, yellow-brown, ferru-
ginous, jarositic, thin-bedded, resist-
ant, rich in plant fossils. Twelve
feet above base of unit is 1^-foot
band of conglomerate, white, sandy,
ill-sorted, containing pebbles of
gneiss and quartzite; a similar con-
glomeratic band, 2 feet thick, occurs

33 feet above base of unit 56

2. Sandstone, white, with occasional
minor red mottling, quartzose,
clayey, dominantly fine-grained, also
medium-grained, non-friable, gener-
ally well-sorted, sub -rounded to
rounded grains, massively bedded, oc-
casionally cross-bedded on small scale
in restricted bands, sometimes irregu-
larly jointed; minor lenses (up to 9
inches thick) of sandstone, white,
silty, coarse-grained, poorly sorted;
rare thin bands of siltstone, white,

clayey, micaceous, bedded 522

1. Sandstone, red, ferruginous, silty,
fine- to medium-grained, non-friable,
moderately sorted, sub-rounded grains,
massively bedded. 4

Carynginia Formation (844 feet).

The Wagina Sandstone is a rather
monotonous sequence of massively bedded,
white and occasionally red sandstone and rare
conglomerate, with plant-bearing intercalations
of siltstone and shale near the top.

In the north-eastern part of the area, the
Wagina Sandstone crops out extensively on the
breakaway slopes, which appear conspicuously
white even when viewed from some distance.
Also, the formation is well-exposed immedi-
ately north of the Mingenew-Morawa road for
some distance along Ebano Creek, to the east
of Ebano Spring. The country underlain by
the Wagina Sandstone has a characteristic
white sandy soil.

The Wagina Sandstone rests conformably
upon the Carynginia Formation. Although the
contact between the Wagina Sandstone and
the Archaean rocks is not exposed, it can gen-
erally be established with precision from the
air photographs (see General Geology).

The Wagina Sandstone attains a thickness
of 796 feet along the Woolaga Creek reference
section, in contrast to the type section in the
Irwin River area which is only 300 feet thick.

(ii) Biostratigraphy.— The only fossils dis-
covered in the Wagina Sandstone in the area
under consideration were plant impressions
from unit 3 of the reference section (see Plate
1, 4). These include Glossopteris , Gangamop-
teris, and Vertebraria, all of which are charac-
teristic genera of the Gondwana flora, and
hence indicate a Permian age for the formation.

McWhae et al. (1958) believe that the
Wagina Sandstone is of Artinskian age.

(iii) Environment of Deposition. — The abrupt
change from the jarositic siltstones of the
marine Carynginia Formation to the argil-
laceous quartz sandstones of the Wagina
Sandstone suggests a radical change in condi-
tions of sedimentation. Furthermore, the
relatively uniform lithology of the Wagina
Sandstone is evidence that these new conditions

persisted practically unchanged throughout the
remainder of the documented Permian in the
Woolaga Creek area.

The present author is in agreement with
P. E. Playford and S. P. Willmott (in McWhae
et al. 1958) that the environment of deposition
was probably continental. However, the
evidence for this is by no means conclusive.

The intercalations of plant-bearing siltstone
and shale near the top of the exposed Wagina
Sandstone point to continental deposition, but
the remaining bulk of the formation, consist-
ing of unfossiliferous, massive, white sandstone
offers little corroborative evidence for either
a marine or a non-marine environment. How-
ever, the general lack of fossils in such a
sequence does suggest that it is continental
rather than marine. Active reworking of the
sediment in a stable environment of low relief
is indicated by the well-sorted nature of the
sandstone and its lack of feldspathic constitu-
ents.

Structure

The Permian sediments of the Woolaga Creek
area are on the down-thrown, western side of
the meridional Darling Fault, which is the
major controlling structural feature of the
area. The strata have a gentle easterly tilt and
are deformed against the Archaean rocks along
the Darling Fault. Proceeding eastwards, then,
we encounter rocks progressively higher in the
Permian succession, from the Nangetty Forma-
tion in the extreme south-western part of the
area to, ultimately, the Wagina Sandstone
adjacent to the fault line in the north-eastern
portion.

The dip of the sediments increases eastward
toward the Darling Fault, where the down-
throw movement has been greatest. Thus, the
dip in the Holmwood Shale, in the western part
of the area, is generally about 4° to the east,
whereas farther east an easterly dip of 10° is
usual in the Irwin River Coal Measures. At
Red Hill, the contact between the Carynginia
Formation and the Wagina Sandstone dips east
at 12°. The easterly dip in the Wagina Sand-
stone one quarter of a mile west of the Darling-
Fault is 18° (see Plate 1, 4.)

Synclinal drag effects cause westerly dips in
strata close to the Darling Fault. At (649857),
the westerly dip of the Wagina Sandstone
decreases (from east to west) from 60° to 17°
in a distance of 20 yards. This outcrop is on
the south bank of Ebano Creek, 300 yards west
of the Darling Fault line.

In the eastern part of the area, the forma-
tions are bent against the Darling Fault, so
that, to the south, they effectively enclose the
marginal syncline. Hence the syncline is
plunging north, and at a fairly low angle. Thus,
the Wagina Sandstone (in the north), the
Carynginia Formation and, finally, the Irwin
River Coal Measures (in the south) are found
successively along the Darling Fault line in
abutment with the Archaean rocks. Field
mapping shows that the prominent boundary
between the Carynginia Formation and the

25

Wagina Sandstone is deflected through 145°
within a distance of one half a mile marginal
to the Darling Fault.

An excellent exposure of the marginal drag
effect is seen in breakaways in the general
vicinity of (652844), south of the Mingenew-
Morawa road. Here, the elongate, curving
shapes of the hills reproduce faithfully the
western limb of the syncline and its southerly
closure, and the trends are illustrated strikingly
by the air photographs.

A small isolated basin, truncated abruptly on
its eastern margin by the Darling Fault, is
developed in lateritized strata of the Irwin
River Coal Measures. This structure, which
is also very well delineated on the air photo-
graphs, has a meridional extent of three-
eighths of a mile and is one-eighth of a mile
wide. It is more precisely described as a
doubly plunging syncline (Billings 1954, p.
49), and its restricted form 'has evidently re-
sulted from a local change in the general
northerly plunge of the synclinal axis adjacent
to the Darling Fault.

From Plate IV in Johnson et al. (1954) it
appears that the synclinal axis undergoes
repeated and somewhat irregular reversals of
plunge to the north of the Woolaga Creek area,
with the Wagina Sandstone or immediately
underlying formations thrown against the
Archaean rocks.

Away from the Darling Fault, the strike of
the sediments throughout most of the area
averages 145°, although in the general vicinity
of Mt. Budd, the prevailing strike is about 110°.

The Darling Fault has a uniform trend of
155° in the Woolaga Creek area. The factors
responsible for the clarity with which this
major structure is visible on the air photo-
graphs, have been discussed previously under
General Geology. The almost perfectly linear
trace of the fault, virtually independent of
topography, indicates a vertical or near-vertical
dip. As viewed from the air photographs, the
Darling Fault appears to have a very steep
westerly dip at two localities (666827) and
(676806). However, at (673813), the dip appears
to be steeply to the east.

The throw of the Darling Fault can be esti-
mated only within very broad limits. It must
be not less than the total thickness of the
Permian strata, and would seem to be very
much greater when the immense thickness of
the Yandanooka Group is taken into considera-
tion.

The last movement on the Darling Fault in
the Woolaga Creek area was post-Permian, pre-
lateritization, and probably pre-Jurassic. Other
active phases of the Darling Fault, however, are
believed to date back to Precambrian times
(Clarke et al. 1951, p. 69).

The Permian strata have been disturbed by
relatively minor gravity faulting. The faults
have small lateral extent, are usually parallel
to the strike of the sediments, and generally
appear to cause only minor displacements. In
most instances, the down-thrown block is to the

east. That is, the faults are generally anti-
thetic with respect to the Darling Fault, and
consequently result in loss of stratigraphic
section. They are recognizable in the field
commonly as narrow, often ferruginized or
silicified zones of relatively steeply dipping
strata.

A good example, previously described, occurs,
in unit 3 of the High Cliff Sandstone.

At (646873) in the north-eastern part of the-
area, the Wagina Sandstone is fractured by a
fault adjacent and parallel to the Darling Fault.
It is an antithetic, normal fault dipping very
steeply to the east and is well-displayed by the-
air photographs.

As noted previously, the contact between the
High Cliff Sandstone and the Irwin River Coal
Measures is a fault plane in three separate-
localities.

A small strike fault of westerly throw is.
exposed at (634836) in siltstones and sand-
stones of the Irwin River Coal Measures. The
fault plane stands out as a resistant fer-
ruginized zone dipping to the west at 57°.

There is no evidence of compressive folding
in the Permian strata of the Woolaga Creek
area.

Geological History

Previous palaeogeographic interpretations, in-
cluding those given by Woolnough and
Somerville (1924), Woolnough (1937), Clarke
et al. (1951) and Johnson et al. (1954), have been
based mainly on the geological record preserved
in the Irwin River area. It will be seen from
the following paragraphs that the geological
histories of the Woolaga Creek and Irwin River
areas are essentially similar, which is logical in
view of the stratigraphic parallelism in the two-
areas.

The first recorded event in the geological
history of the Woolaga Creek area was the
deposition of glacial and fluvio -glacial sedi-
ments in a frigid climate characteristic of the-
earliest Permian throughout Gondwanaland.
The glacial Nangetty Formation has only minor-
representation in the Woolaga Creek area.

The succeeding Holmwood Shale was de-
posited in a marine environment of restricted
circulation, probably in an extensive landlocked
bight separated from the open ocean by a bar
zone. The location of this “bar” is uncertain,
but it may have been to the west or south. The
climate was apparently cold, though not as
extreme as in the earlier Nangetty times, and
occasional erratic boulders in the formation
suggest “dumping” from contemporary icebergs.
The fossiliferous Woolaga Limestone Member
is evidence of an interlude of normal marine
conditions in the basin, and suggests a period
of ineffectiveness of the barrier. Other lime-
stone beds containing rare fossils represent
scattered localities over the basin floor of lime-
mud deposition associated with somewhat
restricted animal communities.

26

Thus the Sakmarian Stage in the area was
characterized by conditions generally un-
favourable for animal life, due initially to a
frigid climate and later to a euxinic deposi-
tional environment.

In early Artinskian time, the Woolaga Creek
area possibly underwent some emergence, and
the High Cliff Sandstone accumulated under
shallow-water marine conditions of normal cir-
culation. A prolific fauna of marine inverte-
brates thrived in early High Cliff time. The
boulders in the middle of the formation may
have been deposited from floating ice.

A recession of the sea from the area con-
cluded this shallow-marine interlude, and the
Irwin River Coal Measures were next laid down
under fluvial and swampy conditions, perhaps
as the topset beds of an extensive delta. The
land was vegetated by typical representatives
of the Glossopteris flora. The erratic boulders,
which are also present in this formation, may
have been rafted in by either floating vegeta-
tion or icebergs.

The transitional boundary between the Irwin
River Coal Measures and the overlying Caryn-
ginia Formation records a gradual deepening
of the depositional basin and the re-establish-
ment of marine conditions throughout the area.
The Carynginia Formation, with its predomin-
ant jarositic siltstones, represents an interest-
ing recurrence of the stagnant barred basin
environment of Holmwood time. However, the
presence of abundant sandy intercalations with
ripple-marking, cross-bedding and worm tracks
attests to somewhat shallower conditions, with
greater influence of waves and currents than
in Holmwood time. A cold prevailing climate
with contemporary floating ice is again sug-
gested by the “dumped” erratics in the basal
part of the Carynginia Formation.

The abrupt change from the Carynginia
Formation to the succeeding non-marine
Wagina Sandstone points to a sudden dis-
appearance of the sea from the area and a
return to continental conditions. Plant-bearing
siltstones and shales near the top of the Wagina
Sandstone indicate the existence of the Glos-
sopteris flora. The Wagina Sandstone may be
Artinskian in age, and represents the final
fragment of palaeogeographic evidence of the
Permian Period in the Woolaga Creek area.

Large-scale, west-block-down movement oc-
curred along the Darling Fault at some stage
following Wagina times, and certainly prior to
lateritization. This resulted in the easterly tilt
of the Permian strata and their marginal
deformation against the Archaean complex.
Gravity faulting within the Permian rocks may
have preceded the Darling Fault activity, but
it seems more likely to have occurred during
this important tectonism as relatively minor
adjustments of the sediments.

The area was subsequently eroded and
reduced to a peneplain, probably by early
Tertiary times. Arenaceous continental rocks
were deposited sporadically over this surface
of low relief. The area was then elevated and
the resultant plateau subjected to intensive

dissection. The cuirass of duricrust with its
associated sand-plain developed during a cli-
mate having the requisite seasonal distribution
of rainfall. This lateritization resulted in
superficial alteration of both the Permian and
Archaean rocks.

Erosion by the existing river system has
continued through the Quaternary to the pre-
sent day with the removal of much of the
Victoria Plateau surface and the consequent
widespread exposure of the underlying Permian
strata.

Acknowledgments

This investigation was undertaken as a
research project at the Department of Geology,
University of Western Australia. The author
wishes to thank his supervisors, Drs. B. F.
Glenister and J. J. E. Glover, for their ready
assistance and advice and for critically reading
the manuscript; also Professor R. T. Prider,
Mr. B. E. Balme, Mr. C. R. Elkington and Mr.
B. W. Logan. Mr. Balme contributed the por-
tion of this paper on the palynology of the
Holmwood Shale; Mr. Elkington assisted with
the measurement of the stratigraphic section.
The author also wishes to thank Mr. P. E.
Playford, of West Australian Petroleum Pty.
Ltd., for valuable advice and encouragement.
Mr. J M. Dickins, of the Bureau of Mineral
Resources, Geology and Geophysics, Canberra,
kindly identified fossils from the Woolaga Creek
area. Special thanks are due to Mr. F. L. Billing
for assistance in the preparation of the photo-
graphs. The research was carried out during
the tenure of a Hackett Scholarship from the
University of Western Australia.

References

Billings, M. P. (1954). — “Structural Geology.” 2nd Ed.

(Prentice-Hall: New York.)

Campbell, W. D. (1910).— The Irwin River coalfield and
the adjacent districts from Arrino to
Northampton. Bull. Geol. Surv. W. Aust
38: 1-108.

Clarke, E. de C, Prendergast, K. L., Teichert, C., and
Fairbridge, R. W. (1951). — Permian succes-
sion and structure in the northern part
of the Irwin Basin, Western Australia.
J. Roy . Soc. W. Aust. 35: 31-84.

Cotton, C A. (1945). — “Geomorphology.” 4th Ed. (Whit-
combe and Tombs: Christchurch.)

Dickins, J. M. (1957). — Permian fossils from Woolaga
Creek, Irwin Valley. Western Australia. Rec.
Bur. Miner. Resour. Aust. 1957/110.

Dickins, J. M., and Thomas, G. A. (1957). — Permian
fossils from Carynginia Gully, Irwin River
area, Western Australia. Rec. Bur. Miner.
Resour. Aust. 1957/69.

Fairbridge, R. W. (1952).— The Permian of South West-
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Series Gondwana: 136-146.

Johnson, W., de la Hunty, L. E., and Gleeson, J. S.

(1954). — The geology of the Irwin River
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country. Bull. Geol. Surv. W. Aust.
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cas. Mem. Geol. Soc. Amer. 23: 1-114.

27

Playford, P. E. (1954). — Observations on laterite in
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Soc. N.S.W. 58: 67-112.

t

28

29

-Slumping in the Irwin River Coal Measures at (638834), on the west bank of Woolaga Creek.

-Northern aspect of Red Hill, a butte, which consists of Carynginia Formation overlain near the top by a thin capping of Wagina Sandstone. The
breakaways to the left (east) expose Wagina Sandstone.

-Plant fossil locality in the Wagina Sandstone at (651849), on the northern point of a narrow mesa. The strata are dipping comparatively steeply to
the east, and are on the western limb of the drag syncline adjacent to the Darling Fault.

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WOOLAGA CREEK

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31

Fig. 3. — Geological cross section from A-B (Map 1).

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32

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Journal

of the

Royal Society of Western Australia, Inc.

Volume 42

1959

Part 1
Contents

1. The Potential of some Native West Australian Plants. Presidential Address,

1958. By A. J. Millington.

2. Permian Stratigraphy of the Woolaga Creek Area, Mingenew District,
Western Australia. By G. Playford.

Editor: J. E. Glover

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