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BY THE SAME AUTHOR.
The Foraminifera
An Introduction to the Study of the Protozoa
by
FREDERICK CHAPMAN, A.L.S., F.R.M.S.
This book has been written with a view of meeting a demand which
has arisen for a concise account of the Foraminifera, suited to the
requirements of the student of Natural History and Palaeontology.
With 14 plates and 42 illustrations in the Text.
DEMY 8vo. CLOTH, 10s. 6d.
[Illustration: The Keystone Printing Co., 552-4 Lonsdale St., Melb.]
[Illustration: =A FOSSIL CRINOID=
(Helicocrinus plumosus), about 5/6 nat. size, in Silurian Mudstone,
Brunswick, Victoria.
(_Spec. in Nat. Mus., Melbourne_).
]
Australasian Fossils
A Students' Manual of Palaeontology
By FREDERICK CHAPMAN,
Palaeontologist to the National Museum, Melbourne.
Formerly Assistant in the Geological Department of the Royal College of
Science, London.
Assoc. Linnean Soc. [Lond.], F.R.M.S., etc.
Author of "The Foraminifera," "A Monograph of the Silurian Bivalved
Mollusca of Victoria," "New or Little-known Victorian Fossils in the
National Museum," etc.
With an Introduction by
PROFESSOR E. W. SKEATS, D.Sc., F.G.S.
GEORGE ROBERTSON & COMPANY PROPY. LTD.,
Melbourne, Sydney, Adelaide, Brisbane and London.
1914.
To
PROFESSOR JOHN WESLEY JUDD
this work is dedicated as a slight tribute of esteem, and in grateful
acknowledgement of kindly help and encouragement through many years.
CONTENTS.
Page
Preface 10
Introduction by Professor E. W. Skeats, D.Sc., F.G.S. 13
PART I.--GENERAL PRINCIPLES.
Chap. I.--Nature and uses of Fossils 21
" II.--Classification of Fossil Animals and Plants 34
" III.--The Geological Epochs and Time-range of Fossils 41
" IV.--How Fossils are Found, and the Rocks They Form 51
PART II.--SYSTEMATIC PALAEONTOLOGY.
Chap. V.--Fossil Plants 82
" VI.--Fossil Foraminifera and Radiolaria 95
" VII.--Fossil Sponges, Corals and Graptolites 107
" VIII.--Fossil Starfishes, Sea-lilies and Sea-urchins 133
" IX.--Fossil Worms, Sea-mats and Lamp-shells 152
" X.--Fossil Shell-fish 174
" XI.--Fossil Trilobites, Crustacea and Insects 220
" XII.--Fossil Fishes, Amphibians, Reptiles, Birds and Mammals 257
Appendix.--Notes on Collecting and Preserving Fossils 315
Index 321
LIST OF ILLUSTRATIONS.
Fig. Page
1. Fossil Shells in clay 22
2. Tracks, probably of Crustaceans 22
3. Structure of Silicified Wood in tangential section:
_Araucarioxylon Daintreei_, Chapm. 24
4. Portrait of William Smith 26
5. Raised Beach: Brighton, England 28
6. Raised Beach: Torquay, Victoria 28
7. Marine Fossils in Volcanic Tuff: Summit of Snowdon 29
8. Kitchen Middens: Torquay, Victoria 30
9. Submerged Forest on the Cheshire Coast 30
10. _Pecten murrayanus_, Tate. A fossil shell allied to
a living species 32
11. Cliff section: Torquay, Victoria 42
12. Diagram of superposition of Strata 42
13. Diagram of the Range-in-time of Australasian Fossils 50
14. _Diprotodon_ skeletons in situ: Lake Callabonna, S. Australia 51
15. Bird remains on sand dunes: King Island, Bass Strait 52
16. Impression of Bird's feather in Ironstone: Western Victoria 52
17. A Fossil Turtle: _Notochelone costata_, Owen sp. 52
18. A Ganoid Fish: _Pristisomus crassus_, A. S. Woodward 54
19. A fossil Insect in amber (_Tipula sp._) 54
20. A fossil Crustacean: _Thalassina emerii_, Bell 55
21. An Ammonite: _Desmoceras flindersi_, McCoy sp. 55
22. Belemnites: _Belemnites diptycha_, McCoy 56
23. A Group of Lamp-shells: _Magellania flavescens_, Lam. sp. 56
24. Zoarium of a living Polyzoan: _Retepora_ sp. 58
25. A fossil Polyzoan: _Macropora clarkei_, T. Woods sp. 58
26. Fossil Worm-tubes: (?) _Serpula_ 60
27. A living Sea-urchin: _Strongylocentrotus erythrogrammus_, Val. 60
28. A fossil Sea-urchin: _Linthia antiaustrails_, Tate 60
29. A fossil Brittle-Star: _Ophioderma egertoni_, Brod. sp. 60
30. A fossil Crinoid: _Taxocrinus simplex_, Phillips sp. 62
31. Graptolites on Slate: _Tetragraptus fruticosus_, J. Hall sp. 62
32. A Stromatoporoid: _Actinostroma_ 63
33. Corals in Devonian Marble: _Favosites_ 64
34. Siliceous Skeleton of a living Sponge: (?) _Chonelasma_ 64
35. Spicules of a fossil Sponge: _Ecionema newberyi_, McCoy sp. 65
36. Nummulites: _N. gizehensis_, Ehr. var. _champollioni_, De
la Harpe 65
37. Cainozoic Radiolaria 66
38. Radiolaria in Siliceous Limestone 67
39. Travertin Limestone, with leaves of Beech (_Fagus_) 67
40. Freshwater Limestone with shells (_Bulinus_) 68
41. Hardened mudstone with Brachiopods (_Orthis_, etc.) 69
42. Diatomaceous Earth 72
43. _Lepidocyclina_ Limestone 73
44. Coral in Limestone: _Favosites grandipora_, Eth. fil. 74
45. Crinoidal Limestone 74
46. Turritella Limestone 75
47. Ostracodal Limestone 75
48. _Halimeda_ Limestone 77
49. Tasmanite: a Spore Coal 77
50. Kerosene Shale 77
51. Bone Bed 77
52. Bone Breccia 79
53. Cainozoic Ironstone with Leaves (_Banksia_) 80
54. _Girvanella conferta_, Chapm., in Silurian Limestone 83
55. Palaeozoic Plants 83
56. Restoration of _Lepidodendron_ 84
57. Stem of _Lepidodendron (Lepidophloios)_, showing leaf-scars 84
58. Upper Palaeozoic Plants 85
59. Map of Gondwana-Land 87
60. Mesozoic Plants 88
61. Cainozoic Plants 90
62. Eucalyptus leaves from the Deep Leads 92
63. Palaeozoic and Mesozoic Foraminifera 97
64. _Lepidocyclina marginata_, Mich. sp. Sections of shell
showing structure 99
65. Cainozoic Foraminifera 100
66. Fossil Radiolaria 103
67. Palaeozoic Sponges and Archaeocyathinae 108
68. Cainozoic Sponges 111
69. Silurian Corals 111
70. Upper Palaeozoic Corals 116
71. Cainozoic Corals 118
72. Stromatoporoidea and Cladophora 121
73. Lower Ordovician Graptolites 125
74. Lower Ordovician Graptolites 125
75. Upper Ordovician and Silurian Graptolites 127
76. Fossil Crinoids 135
77. Fossil Starfishes 140
78. _Protaster brisingoides_, Gregory, in Silurian Sandstone 142
79. _Gregoriura spryi_, Chapm., in Silurian Mudstone 143
80. Cainozoic Sea-urchins 145
81. Cainozoic Sea-urchins 147
82. Fossil Worms 153
83. Palaeozoic Polyzoa 156
84. Cainozoic Polyzoa 157
85. Lower Palaeozoic Brachiopods 159
86. Silurian and Devonian Brachiopods 161
87. Carbopermian Brachiopods 163
88. Mesozoic Brachiopods 165
89. Cainozoic Brachiopods 167
90. Lower Palaeozoic Bivalves 176
91. Palaeozoic Bivalves 179
92. Carbopermian Bivalves 180
93. Lower Mesozoic Bivalves 181
94. Cretaceous Bivalves 183
95. Cainozoic Bivalves 185
96. Cainozoic Bivalves 186
97. Fossil Scaphopods and Chitons 188
98. Lower Palaeozoic Gasteropoda 192
99. Silurian Gasteropoda 194
100. Upper Palaeozoic Gasteropoda 195
101. Mesozoic Gasteropoda 197
102. Cainozoic Gasteropoda 199
103. Cainozoic Gasteropoda 200
104. Late Cainozoic and Pleistocene Gasteropoda 201
105. Palaeozoic Cephalopoda 206
106. Mesozoic and Cainozoic Cephalopoda 208
107. Diagram restoration of an Australian Trilobite (_Dalmanites_) 224
108. Cambrian Trilobites 226
109. Older Silurian Trilobites 228
110. Newer Silurian Trilobites 230
111. Carboniferous Trilobites and a Phyllopod 232
112. Silurian Ostracoda 236
113. Upper Palaeozoic and Mesozoic Ostracoda 238
114. Cainozoic Ostracoda 239
115. Fossil Cirripedes 242
116. Cirripedes. _Lepas anatifera_, Linn.: living goose
barnacle, and _L. pritchardi_, Hall: Cainozoic 242
117. _Ceratiocaris papilio_, Salter 244
118. Ordovician Phyllocarids 245
119. Silurian Phyllocarids 245
120. Fossil Crabs and Insects 247
121. Silurian Eurypterids 249
122. _Thyestes magnificus_, Chapm. 259
123. _Gyracanthides murrayi_, A. S. Woodw. Restoration 260
124. Teeth and Scales of Palaeozoic and Mesozoic Fishes 260
125. _Cleithrolepis granulatus_, Egerton 263
126. Tooth of _Ceratodus avus_, A. S. W., and phalangeal
of a carnivorous Deinosaur 264
127. Scale of _Ceratodus ? avus_ 265
128. The Queensland Lung-fish: _Neoceratodus forsteri_, Krefft 266
129. _Leptolepis gregarius_, A. S. W. 266
130. Cretaceous and Cainozoic Fish-teeth 268
131. Cainozoic Fish remains 270
132. _Bothriceps major_, A. S. W. 273
133. _Ichthyosaurus australis_, McCoy 277
134. Fossil Reptiles 278
135. Impression of Bird's feather, magnified, Cainozoic: Victoria 281
136. _Cnemiornis calcitrans_, Owen 284
137. _Dinornis maximus_, Owen. Great Moa 284
138. _Pachyornis elephantopus_, Owen 285
139. Skeleton of _Sarcophilus ursinus_, Harris sp. 288
140. Skull of fossil specimen of _Sarcophilus ursinus_ 288
141. _Thylacinus major_, Owen. Hind part of mandible 289
142. _Phascolomys pliocenus_, McCoy. Mandible 290
143. Cainozoic Teeth and Otolith 291
144. Skeleton of _Diprotodon australis_, Owen 291
145. Right hind foot of _Diprotodon australis_ 292
146. Restoration of _Diprotodon australis_ 292
147. Skull and mandible of _Thylacoleo carnifex_, Owen 293
148. _Wynyardia bassiana_, Spencer 294
149. Tooth of _Scaldicetus macgeei_, Chapm. 297
150. Impressions of footprints in dune sand-rock, Warrnambool 301
Map of Australia, showing chief fossiliferous localities.
PREFACE.
The more important discoveries of fossils in the southern hemisphere
have received, as a rule, very meagre notice in many of the text-books
of Geology and Palaeontology published in England, Germany and America,
and used by Australasian students. It is thought, therefore, that the
time has arrived when an attempt should be made to collect the main facts
bearing upon this subject, in order to present them from an _Australasian_
standpoint. With this in view, references to fossils occurring in the
northern hemisphere are subordinated, seeing that these may be easily
obtained on reference to the accepted text-books in general use.
The present work does not presume to furnish a complete record of
Australasian palaeontology, since that would mean the production of a much
more extensive and costly volume. Sufficient information is here given,
however, to form a groundwork for the student of this section of natural
science, and a guide to the collector of these "medals of creation."
The systematic portion of this book has been arranged primarily from the
biological side, since Palaeontology is the "study of ancient life."
Taking each life-group, therefore, from the lowest to the highest types,
all the divisions represented by fossils are dealt with in turn, beginning
with their occurrence in the oldest rocks and ending with those in the
newest strata.
If a commendation of the study of fossils, apart from its scientific
utility, were needed, it could be pointed out that palaeontology as a
branch of geology is, _par excellence_, an open-air study: and since
it requires as handmaids all the sister sciences, is a subject of
far-reaching interest. Microscopy and photography are of immense value
in certain branches of fossil research, the former in the examination of
the minute forms of mollusca, foraminifera and ostracoda, the latter in
the exact portraiture of specimens too intricate to copy with the brush,
or too evanescent to long retain, when out of their matrix, their clean
fresh surfaces. With geology or palaeontology as an objective, a country
walk may be a source of much enjoyment to its students, for "in their hand
is Nature like an open book"; and the specimens collected on a summer
excursion may be closely and profitably studied in the spare time of the
winter recess.
The author sincerely trusts that students may share the same pleasure
which he has derived from the study of these relics of past life; and that
the present attempt to show their relationship both in geological time and
biological organisation, may be the means of inducing many to make further
advances in this fascinating subject.
In the production of this work several friends and collaborators have
materially assisted, their aid considerably increasing its value. It is
therefore with grateful thanks that the author acknowledges the help and
encouragement given by Professor E. W. Skeats, D.Sc., who has not only
been good enough to write the Introductory passages, but who has carefully
gone over the MS. and made many helpful suggestions. Mr. W. S. Dun,
F.G.S., Palaeontologist to the Geological Survey Branch of the Department
of Mines, Sydney, has also rendered generous help in giving the benefit
of his full acquaintance of the palaeontology of his own State. To the
Trustees of the National Museum the author is under special obligations
for permission to photograph many unique fossil specimens in the Museum
collection, comprising Figs. 3, 16-18, 20-22, 28-31, 35, 39, 40, 45, 46,
51-54, 57, 62, 78, 79, 127, 133, 136, 147 and 148. The author's thanks
are also due to Dr. E. C. Stirling, M.D., M.A., F.R.S., for permission to
use Figs. 143, 144 and 145, whilst similar privileges have been accorded
by Prof. A. G. Seward, F.R.S., Dr. F. A. Bather, F.R.S., and Mr. C. L.
Barrett. Prof. T. W. Edgeworth David, F.R.S., has kindly cleared up
some doubtful points of stratigraphy and further increased the author's
indebtedness by the loan of a unique slide of Radiolaria figured on p. 69.
Mr. Eastwood Moore, to whom special thanks are due, has greatly added to
the pictorial side of this work by his skillful help in preparing many of
the illustrations for the press, as well as in the drawing of the several
maps. The grouped sets of fossils have been especially drawn for this work
by the author. They are either copied from authentic specimens or from
previously published drawings; references to the authorities being given
in the accompanying legends. Dr. T. S. Hall has kindly read the section
on Graptolites and Mammalia. For many helpful suggestions and the careful
reading of proofs, thanks are especially owing to Mr. W. E. G. Simons, Mr.
R. A. Keble, and to my wife.
INTRODUCTION.
Geological Department,
The University, Melbourne.
William Smith, the Father of English Geology, used to apologize for the
study of palaeontology by claiming that "the search for a fossil is at
least as rational a proceeding as the pursuit of a hare." Those of us who
are accustomed to take the field, armed with a hammer, in the search for
"medals of creation" and from time to time have experienced the sporting
enjoyment of bringing to light a rare or perfect specimen are quite
prepared to support his claim. But the student of fossils needs the help
of a text book to guide him to the literature on the subject, to help
him with his identifications or to indicate that some of his finds are
new and hitherto undescribed. European and American workers have long
been provided with excellent books treating generally of fossils, but the
illustrations have been quite naturally taken mainly from forms occurring
in the Northern Hemisphere. Our own fossil forms both plants and animals
are numerous, interesting and in many cases peculiar, but the literature
concerning them is so widely scattered in various scientific publications
that a warm welcome should be given to this book of Mr. Chapman's, in
which the Australian evidence is brought together and summarised by one,
whose training, long experience, and personal research qualify him to
undertake the task. Especially will teachers and students of Geology and
Palaeontology value such an undertaking. Workers in other countries who
have only partial access to the Australian literature on the subject
should also find this a valuable book of reference.
In the study of fossils we are concerned with the nature, evolution
and distribution of the former inhabitants of the earth. The study of
Palaeontology may be justified as a means of scientific discipline, for
the contributions the subject makes to the increase of natural knowledge
and the unfolding of panoramas of ancient life. It also provides perhaps
the most positive evidence in the story of evolution. So, too, the student
of the present day distribution of animals and plants finds the key to
many a problem in zoo-geography in the records of past migrations yielded
by the study of fossils in different lands. The stratigraphical geologist
is of course principally concerned with two important aspects of the study
of fossils.
The masterly generalisation of William Smith that strata can be identified
by their fossil contents established by close study of the rocks and
fossils of the British Oolites has been confirmed generally by subsequent
work. The comparative study of the fossil contents of rocks in widely
separated areas has proved to be the most valuable means by which the
correlation of the rocks can be effected and their identity of age
established. In some cases the recognition of a single fossil species
in two areas separated, perhaps, by thousands of miles may suffice to
demonstrate that the rocks are of the same age. For example, a graptolite
such as _Phyllograptus typus_ is found in many parts of the world, but has
only a very restricted range in time. It has been found only in rocks of
Lower Ordovician age. Its occurrence in Wales and in the rocks of Bendigo
practically suffices to establish the identity in age of the rocks in
these widely separated areas.
Generally, however, much closer study and a more detailed examination of a
large number of the fossils of a rock series are required before the age
of the rocks can be surely established and a safe correlation made with
distant localities.
The stratigraphical generalisations to be made from the study of fossils
however must be qualified by certain considerations. Among these are the
fact that our knowledge of the life forms of a given geological period is
necessarily incomplete, that the differences in the fossil contents of
rocks may depend not only on differences of age but also in the conditions
under which the organisms lived and the rocks were accumulated, and that
forms of life originating in one area do not spread themselves immediately
over the earth but migrate at velocities depending on their mode of life
and the presence or absence of barriers to their progress.
Our incomplete knowledge of the forms living in remote geological periods
arises partly from the fact that some forms had no permanent skeleton
and were therefore incapable of preservation, partly to the obliteration
of the skeletons of organisms through subsequent earth movements in the
rocks or through the solvent action of water. Many land forms, too,
probably disintegrated on the surface before deposits were formed over
the area. Apart from these causes which determine that a full knowledge
of the fossils from ancient rocks in particular, will never be acquired,
our knowledge is incomplete by reason either of difficulty of access to
certain areas or incomplete search. As a result of later discoveries
earlier conclusions based on incomplete evidence as to the age of a rock
series, have not infrequently been modified.
The study of the present distribution of animals and plants over the
earth is a help in the attempt to decide how far the fossil differences
in the sets of rocks are due to differences in the ages of the rocks or
to differences in the conditions under which the organisms lived. The
present, in this, as in many other geological problems, is the key to the
past.
We know, for instance, that differences of climate largely control the
geographical distribution of land animals and especially of land plants,
and for that reason among others, fossil plants are generally less
trustworthy guides to geological age than fossil animals.
In the distribution of marine animals at the present day we find that
organisms of simple structure are generally more wide-spread and less
susceptible to changes in their environment than are the more complex
organisms with specialised structures. Hence we find, for instance, a
fossil species of the Foraminifera may persist unchanged through several
geological periods, while a species of fossil fish has in general not only
a short range in time but often a restricted geographical extent. If we
consider the marine organisms found at the present day we find a number
of free-swimming forms very widely distributed, while a large number are
restricted either by reason of climate or of depth. Certain organisms
are only to be found between high and low tide levels, others between
low tide level and a depth of thirty fathoms, while many quite different
forms live in deeper waters. If we confine our attention to shallow-water
marine forms we note that certain forms are at the present day restricted
to waters of a certain temperature. We find, therefore, a contrast between
arctic and tropical faunas, while other types characterize temperate
latitudes. Climatic and bathymetrical differences at the present day
therefore lead to distinct differences in the distribution of certain
organisms, while other forms, less sensitive to these factors, range
widely and may be almost universally distributed. Similar conditions
obtained in past geological times, and therefore in attempting to
correlate the rocks of one area with those of another those fossils which
are most wide-spread are often found to be the most valuable.
Attention should also be paid to the conditions under which the deposits
accumulated, since it is clear that rocks may be formed at the same time
in different areas and yet contain many distinct fossils by reason of
climatic or bathymetrical differences. Among living marine organisms we
find certain forms restricted to sandy or muddy sea-bottoms and others
to clear water, and these changes in the conditions of deposition
of sediment have played their part in past geological periods in
determining differences in the fossil faunas of rocks which were laid
down simultaneously. We not infrequently find mudstones passing laterally
into limestones, and this lithological change is always accompanied by
a more or less notable change in the fossil contents of the two rock
types. Such facts emphasize the close connection between stratigraphy
and palaeontology, and indicate that the successful tracing out of the
geological history of any area is only possible when the evidence of the
stratigrapher is reinforced by that provided by the palaeontologist. The
fact that species of animals and plants which have been developed in a
particular area do not spread all over the world at once but migrate
very slowly led Huxley many years ago to put forward his hypothesis of
"homotaxis." He agreed that when the order of succession of rocks and
fossils has been made out in one area, this order and succession will be
found to be generally similar in other areas. The deposits in two such
contrasted areas are homotaxial, that is, show a similarity of order,
but, he claimed, are not necessarily synchronous in their formation. In
whatever parts of the world Carboniferous, Devonian and Silurian fossils
may be found, the rocks with Carboniferous fossils will be found to
overlie those with Devonian, and these in their turn rest upon those
containing Silurian fossils. And yet Huxley maintained that if, say,
Africa was the area in which faunas and floras originated, the migration
of a Silurian fauna and flora might take place so slowly that by the time
it reached Britain the succeeding Devonian forms had developed in Africa,
and when it reached North America, Devonian forms had reached Britain and
Carboniferous forms had developed in Africa. If this were so a Devonian
fauna and flora in Britain may have been contemporaneous with Silurian
life in North America and with a Carboniferous fauna and flora in Africa.
This could only be true if the time taken for the migration of faunas
and floras was so great as to transcend the boundaries between great
geological periods. This does not appear to be the case, and Huxley's idea
in its extreme form has been generally abandoned. At the same time certain
anomalies in the range in time of individual genera have been noted, and
may possibly be explained on such lines. For instance, among the group of
the graptolites, in Britain the genus _Bryograptus_ occurs only in the
Upper Cambrian and the genus _Leptograptus_ only in the Upper Ordovician
rocks. In Victoria these two genera, together with typical Lower
Ordovician forms, may be found near Lancefield preserved on a single slab
of shale. In the same way, in a single quarry in Triassic rocks in New
South Wales, a number of fossil fish have been found and described, some
of which have been compared to Jurassic, others to Permian, and others to
Carboniferous forms in the Northern Hemisphere.
Another point which the palaeontologist may occasionally find evidence for
is the existence of "biological asylums," areas which by means of land or
other barriers may be for a long period separated from the main stream
of evolution. We know that the present fauna and flora of Australia
is largely of archaic aspect, as it includes a number of types which
elsewhere have long ago become extinct or were never developed. This
appears to be due to the long isolation of Australia and, as Professor
Gregory happily puts it--its "development in a biological backwater." We
have some evidence that similar asylums have existed in past geological
periods, with the result that in certain areas where uniform conditions
prevailed for a long time or where isolation from competition prevented
rapid evolution, some organisms which became extinct in other areas,
persisted unchanged in the "asylum" into a younger geological period.
The broad generalizations that rocks may be identified by their fossil
contents and that the testimony of the rocks demonstrates the general
order of evolution from simple to complex forms, have only been placed
on a surer footing by long continued investigations. The modifications
produced by conditions of deposit, of climate and of natural barriers
to migration, while introducing complexities into the problems of
Palaeontology, are every year becoming better known; and when considered
in connection with the variations in the characters of the rocks, provide
valuable and interesting evidence towards the solution of the ultimate
problems of geology and palaeontology, which include the tracing out of
the evolution of the history of the earth from the most remote geological
period to that point at which the geologist hands over his story to the
archaeologist, the historian, and the geographer.
ERNEST W. SKEATS.
PART I.
GENERAL PRINCIPLES.
CHAPTER I.
NATURE AND USES OF FOSSILS.
=Scope of Geology.--=
The science of GEOLOGY, of which PALAEONTOLOGY or the study of fossils,
forms a part, is concerned with the nature and structure of the earth, the
physical forces that have shaped it, and the organic agencies that have
helped to build it.
=Nature of Fossils.--=
The remains of animals and plants that formerly existed in the different
periods of the history of the earth are spoken of as fossils. They are
found, more or less plentifully, in such common rocks as clays, shales,
sandstones, and limestones, all of which are comprised in the great series
of Sedimentary Rocks (Fig. 1).
According to the surroundings of the organisms, whether they existed on
land, in rivers, lakes, estuaries, or the sea, they are spoken of as
belonging to terrestrial, fluviatile, lacustrine, estuarine, or marine
deposits.
[Illustration: =Fig. 1.--Fossil Shells Embedded in Sandy Clay.=
About 3/4 nat. size. Of Cainozoic or Tertiary Age (Kalimnan Series).
Grange Burn, near Hamilton, Victoria.
(_F.C. Coll._)
(G = Glycimeris. L = Limopsis. N = Natica).]
[Illustration: =Fig. 2.--Tracks probably of Crustaceans (Phyllocarids).=
About 3/4 nat. size. Impression of a Slab of Upper Ordovician Shale.
Diggers' Rest, Victoria.
(_F.C. Coll._)
]
The name fossil, from the Latin 'fodere' to dig,--'fossilis,' dug out,--is
applied to the remains of any animals or plants which have been buried
either in sediments laid down in water, in materials gathered together
by the wind on land as sand-dunes, in beds of volcanic ash, or in cave
earths. But not only remains of organisms are thus called fossils, for the
name is also applied to structures only indirectly connected with once
living objects, such as rain-prints, ripple-marks, sun-cracks, and tracks
or impressions of worms and insects (Fig. 2).
=Preservation of Fossils.--=
In ordinary terms, fossils are the durable parts of animals and plants
which have resisted complete decay by being covered over with the deposits
above-named. It is due, then, to the fact that they have been kept from
the action of the air, with its destructive bacteria, that we are able to
still find these relics of life in the past.
=Petrifaction of Fossils.--=
When organisms are covered by a tenacious mud, they sometimes undergo no
further change. Very often, however, moisture containing mineral matter
such as carbonate of lime or silica, percolates through the stratum which
contains the fossils, and then they not only have their pores filled with
the mineral, but their actual substance may also undergo a molecular
change, whereby the original composition of the shell or the hard part is
entirely altered. This tends almost invariably to harden the fossils still
further, which change of condition is called petrifaction, or the making
into stone.
[Illustration: =Fig. 3. Thin Slice of Petrified or Silicified Wood in
Tangential Section.=
Araucarioxylon Daintreei, Chapm. = Dadoxylon australe, Arber; × 28.
Carbopermian: Newcastle, New South Wales.
(_Nat. Mus. Coll._)
]
=Structure Preserved.--=
Petrifaction does not necessarily destroy the structure of a fossil. For
example, a piece of wood, which originally consisted of carbon, hydrogen,
and nitrogen, may be entirely replaced by flint or silica: and yet the
original structure of the wood may be so perfectly preserved that when
a thin slice of the petrifaction is examined under a high power of the
microscope, the tissues with their component cells are seen and easily
recognised (Fig. 3).
=Early Observers.--=
Remains of animals buried in the rocks were known from the earliest times,
and frequent references to these were made by the ancient Greek and Roman
philosophers.
Xenophanes.--
Xenophanes, who lived B.C. 535, wrote of shells, fishes and seals which
had become dried in mud, and were found inland and on the tops of the
highest mountains. The presence of these buried shells and bones was
ascribed by the ancients to a plastic force latent in the earth itself,
while in some cases they were regarded as freaks of nature.
Leonardo da Vinci.--
In the sixteenth and seventeenth centuries Italian observers came to
the fore in clearly demonstrating the true nature of fossils. This was
no doubt due in part to the fact that the Italian coast affords a rich
field of observation in this particular branch of science. The celebrated
painter Leonardo da Vinci (early part of the sixteenth century), who
carried out some engineering works in connection with canals in the north
of Italy, showed that the mud brought down by rivers had penetrated into
the interior of shells at a time when they were still at the bottom of the
sea near the coast.
Steno.--
In 1669, Steno, a Danish physician residing in Italy, wrote a work on
organic petrifactions which are found enclosed in solid rocks, and showed
by his dissection of a shark which had been recently captured and by a
comparison of its teeth with those found fossil in the cliffs, that they
were identical. The same author also pointed out the resemblance between
the shells discovered in the Italian strata and those living on the
adjacent shores. It was not until the close of the eighteenth century,
however, that the study of fossil remains received a decided impetus.
It is curious to note that many of these later authors maintained the
occurrence of a universal flood to account for the presence of fossil
shells and bones on the dry land.
[Illustration: =Fig. 4.--William Smith (1769-1839.)=
"The Father of English Geology," at the age of 69.
(_From Brit. Mus. Cat._)
]
=Fossils an Index to Age.--=
A large part of the credit of showing how fossils are restricted to
certain strata, and help to fix the succession and age of the beds, is due
to the English geologist and surveyor, William Smith (Fig. 4). "The Father
of English Geology," as he has been called, published two works[1] in the
early part of last century, in which he expressed his view of the value of
fossils to the geologist and surveyor, and showed that there was a regular
law of superposition of one bed upon another, and that strata could be
identified at distant localities by their included fossils. Upon this
foundation the work of later geologists has been firmly established; and
students of strata and of fossils work hand in hand.
[Footnote 1: "Strata identified by Organised Fossils," 1816-1819; and
"Stratigraphical System of Organised Fossils," 1817.]
=Stratigraphy.--=
That branch of geology which discusses the nature and relations of the
various sediments of the earth's crust, and the form in which they were
laid down, is called Stratigraphy. From it we learn that in bygone times
many of those places that are now occupied by dry land have been, often
more than once, covered by the sea; and thus Tennyson's lines are forcibly
brought to mind--
"There where the long street roars hath been
The stillness of the central sea."
=Elevated Sea-beds.--=
A striking illustration in proof of this emergence of the land from
the sea is the occurrence of marine shells similar to those now found
living in the sea, in sea-cliffs sometimes many hundreds of feet above
sea-level. When these upraised beds consist of shingle or sand with
shore-loving shells, as limpets and mussels, they are spoken of as Raised
Beaches. Elevated beaches are often found maintaining the same level along
coast-lines for many miles, like those recorded by Darwin at Chili and
Peru, or in the south of England (Fig. 5). They also occur intermittently
along the Victorian coast, especially around the indents, where they have
survived the wear and tear of tides along the coast line (Fig. 6). They
are also a common feature, as a capping, on many coral islands which have
undergone elevation.
[Illustration: =Fig. 5.--A Raised Beach at Black Rock, Brighton, England.=
(_Original_).
]
[Illustration: =Fig. 6.--Raised Beach (a) and Native Middens (b)=
Torquay, Victoria.
(Original).
]
[Illustration: =Fig. 7.--Marine Fossils (Orthis flabellulum, Sowerby.)=
About nat. size. In Volcanic Tuff of Ordovician Age. From the Summit of
Snowdon, North Wales, at an elevation of 3571 feet above sea level.
(_F.C. Coll._)
]
=Sea-beds far from the Present Coast.--=
Marine beds of deeper water origin may be found not only close to the
coast-line, but frequently on the tops of inland hills some miles from
the sea-coast. Their included sea-shells and other organic remains are
often found covered by fine sediment forming extensive beds; and they
may frequently occur in the position in which they lived and died (Fig.
7). Although it is well known that sea-birds carry shell-fish for some
distance inland, yet this would not account for more than a few isolated
examples.
=Raised Beaches as Distinct from Middens.--=
Again, it may be argued that the primitive inhabitants of countries
bordering the coast were in the habit of piling up the empty shells of
the edible molluscs used by them for food: but these "kitchen middens"
are easily distinguished from fossil deposits like shelly beaches, by the
absence of stratified layers; and, further, by the shells being confined
to edible species, as the Cockle (_Cardium_), the Blood-cockle (_Arca_),
the Mussel (_Mytilus_), and the Oyster (_Ostrea_) (Fig. 8).
[Illustration: =Fig. 8.--Remains of Edible Shell Fish=
(Kitchen-midden--native, mirrn-yong)
in Sand Dunes near Spring Creek, Torquay, Victoria.
(_Original_).
]
[Illustration: =Fig. 9.--Part of a Submerged Forest=
seen at low water on the Cheshire coast at Leasowe, England.
(_From Seward's "Fossil Plants"_)
]
=Submerged Forests.--=
Evidence of change in the coast-line is shown by the occurrence of
submerged forest-land, known as "fossil forests," which consist of the
stumps of trees still embedded in the black, loamy soil. Such forests,
when of comparatively recent age, are found near the existing coast-line,
and may sometimes extend for a considerable distance out to sea (Fig. 9).
From the foregoing we learn that:--
_1.--Fossils afford data of the various Changes that have taken place
in past times in the Relative Positions of Land and Water._
=Changes of Climate in the Past.--=
At the present day we find special groups of animals (fauna), and plants
(flora), restricted to tropical climates; and others, conversely, to the
arctic regions. Cycads and tree-ferns, for example, seem to flourish best
in warm or sub-tropical countries: yet in past times they were abundant
in northern Europe in what are now temperate and arctic regions, as in
Yorkshire, Spitzbergen, and Northern Siberia, where indeed at one time
they formed the principal flora.
The rein-deer and musk-sheep, now to be found only in the arctic regions,
once lived in the South of England, France and Germany. The dwarf willow
(_Salix polaris_) and an arctic moss (_Hypnum turgescens_), now restricted
to the same cold region, occur fossil in the South of England.
In Southern Australia and in New Zealand, the marine shells which lived
during the earlier and middle Tertiary times belong to genera and species
which are indicative of a warmer climate than that now prevailing; this
ancient fauna being like that met with in dredging around the northern
coasts of Australia (Fig. 10.)
[Illustration: =Fig. 10.--A Fossil Shell (Pecten murrayanus, Tate).=
Of Oligocene to Lower Pliocene Age in Southern Australia; closely allied
to, if not identical with, a species living off the coast of Queensland.
About nat. size.
(_F.C. Coll._)
]
From the above evidence we may say that:--
_2.--Fossils teach us that in Former Times the Climate of certain
parts of the earth's surface was Different from that now existing._
=Fossils as Guides to Age of Strata.--=
In passing from fossil deposits of fairly recent origin to those of older
date, we find the proportion of living species gradually diminish, being
replaced by forms now extinct. After this the genera themselves are
replaced by more ancient types, and if we penetrate still deeper into
the series of geological strata, even families and orders of animals and
plants give place to others entirely unknown at the present day.
From this we conclude that:--
_3.--Fossil Types, or Guide Fossils, are of great value in indicating
the Relative Age of Geological Formations._
=Gradual Evolution of Life-forms from Lower to Higher Types.--=
As a general rule the various types of animals and plants become simpler
in organisation as we descend the geological scale. For example, in the
oldest rocks the animals are confined to the groups of Foraminifera,
Sponges, Corals, Graptolites, Shell-fish and Trilobites, all back-boneless
animals: whilst it was not until the Devonian period that the primitive
fishes appeared as a well-defined group; and in the next formation, the
Carboniferous Series, the first traces of the Batrachians (Frog-like
animals) and Reptiles are found. Birds do not appear, so far as their
remains are known, until near the close of the Jurassic; whilst Mammals
are sparsely represented by Monotremes and Marsupials in the Triassic and
Jurassic, becoming more abundant in Cainozoic times, and by the Eutheria
(Higher Mammals) from the commencement of the Eocene period.
It is clear from the above and other facts in the geological distribution
of animal types that:--
_4.--The Geological Record supports in the main the Doctrine of
Evolution from Simpler to more Complex types; and fossils throw much
light upon the Ancestry of Animals and Plants now found Living._
CHAPTER II.
THE CLASSIFICATION OF FOSSIL ANIMALS AND PLANTS.
An elementary knowledge of the principles underlying the classification of
animals and plants is essential to the beginner in the study of fossils.
=The Naming of Animals.--=
In order to make a clearly understood reference to an animal, or the
remains of one, it is as necessary to give it a name as it is in the case
of a person or a place. Before the time of Linnaeus (1707-1778), it was
the custom to refer, for example, to a shell, in Latin[2] as "the little
spiral shell, with cross markings and tubercles, like a ram's horn;" or to
a worm as "the rounded worm with an elevated back." Improvements in this
cumbersome method of naming were made by several of the earlier authors
by shortening the description; but no strict rule was established until
the tenth edition of Linnaeus' "Systema Naturae" (1758), when that author
instituted his binomial nomenclature by giving each form enumerated both
a generic and specific name. In plain words, this method takes certain
life-forms closely related, but differing in minute particulars, and
places them together in a genus or kindred group. Thus the true dogs
belong to the genus _Canis_, but since this group also includes wolves,
jackals, and foxes, the various canine animals are respectively designated
by a specific name; thus the dog (_Canis familiaris_), the dingo (_C.
dingo_), the wolf (_C. lupus_), the jackal (_C. aureus_), and the fox (_C.
vulpes_). The generic name is placed first. Allied genera are grouped
in families, (for example, Canidae), these into orders (ex. Carnivora),
the orders into classes (ex. Mammalia), and the classes into phyla or
subkingdoms (ex. Vertebrata).
[Footnote 2: The Latin description was used more commonly than it is at
present, as a universal scientific language.]
Plants are classified in much the same way, with the exception that
families and orders are, by some authors, regarded as of equal value, or
even reversed in value; and instead of the term phylum the name series is
used.
Classification of the Animal Kingdom.
NAME OF PHYLUM. | FORMS FOUND FOSSIL
----------------------+-------------------------------------------------
I.--PROTOZOA | Foraminifera, Radiolaria.
|
II.--COELENTERATA | Sponges, Corals, Stromatoporoids, Graptolites.
|
III.--ECHINODERMATA | Crinoids, Starfishes, Brittle-stars, Sea-urchins.
|
IV.--VERMES | Worms (tube-making and burrowing kinds).
|
V.--MOLLUSCOIDEA | Polyzoa or Sea-mats, Brachiopods or Lamp-shells.
|
VI.--MOLLUSCA | Shell-fish: as Bivalves, Tusk-shells,
| Chitons or Mail-shells, Gasteropods or
| Snails, Pteropods or Sea-butterflies;
| Cuttle-fishes.
|
VII.--ARTHROPODA | Joint-footed animals: as Trilobites, Cyprids,
| Crabs and Lobsters, Centipedes, Spiders
| and Insects.
|
VIII.--VERTEBRATA | Fishes, Amphibians, Reptiles, Birds and Mammals.
Classification of Animal Kingdom.
The first seven groups of the above classification are back-boneless
animals or Invertebrata; the eighth division alone comprising the animals
with a vertebra or backbone.
=Characters of the Several Phyla.--=
In the first group are placed those animals which, when living, consist
of only one cell, or a series of similar cells, but where the cells were
never combined to form tissues having special functions, as in the higher
groups.
PROTOZOA.--
The _Amoeba_ of freshwater ponds is an example of such, but owing to its
skin or cortex being soft, and its consequent inability to be preserved,
it does not concern us here. There are, however, certain marine animals
of this simple type of the Protozoa which secrete carbonate of lime to
form a chambered shell (Foraminifera); or silica to form a netted and
concentrically coated shell held together with radial rods (Radiolaria);
and both of these types are found abundantly as fossils. They are mainly
microscopic, except in the case of the nummulites and a few other kinds of
foraminifera, which are occasionally as large as a crown piece.
COELENTERATA.--
The second group, the Coelenterata, shows a decided advance in
organisation, for the body is multicellular, and provided with a
body-cavity which serves for circulation and digestion. The important
divisions of this group, in which the organisms have hard parts capable of
being fossilised, are the limy and flinty Sponges, the Corals, and allied
groups, as well as the delicate Graptolites which often cover the surface
of the older slates with their serrated, linear forms, resembling pieces
of fret-saws.
ECHINODERMATA.--
The third group, Echinodermata, comprises the Sea-lilies (Crinoids),
Starfishes and Sea-urchins, besides a few other less important types; and
all these mentioned are found living at the present day. Their bodies are
arranged in a radial manner, the skin being strengthened by spicules and
hardened by limy deposits ultimately forming plates. They have a digestive
canal and a circulatory system, and are thus one remove higher than the
preceding group.
VERMES.--
The fourth group, Vermes (Worms), are animals with a bilateral or
two-sided body, which is sometimes divided into segments, but without
jointed appendages. Those which concern the student of fossils are the
tube-making worms, the errant or wandering worms which form casts like the
lob-worm, and the burrowing kinds whose crypts or dwellings become filled
with solid material derived from the surrounding mud.
MOLLUSCOIDEA.--
Group five, the Molluscoidea, contains two types; the Flustras or Sea-mats
(Polyzoa) and the Lamp-shells (Brachiopoda). They are at first sight
totally unlike; for the first-named are colonies of compound animals,
and the second are simple, and enclosed between two valves. They show in
common, however, a bilateral symmetry. The mouth is furnished with fine
tentacles, or with spirally rolled hair-like or ciliated processes.
MOLLUSCA.--
The sixth group, the Mollusca, includes all shell-fish. They are
soft-bodied, bilaterally symmetrical animals, without definite segments.
The shells, on account of being formed of carbonate of lime on an organic
basis, are often found preserved in fossiliferous strata.
ARTHROPODA.--
The seventh group, the Arthropoda, or joint-footed animals, are
distinguished by their segmented, lateral limbs, and by having a body
composed of a series of segments or somites. The body and appendages are
usually protected by a horny covering, the 'exoskeleton.' The group of the
Trilobites played an important part in the first era of the formation of
the earth's crust; whilst the other groups were more sparsely represented
in earlier geological times, but became more and more predominant until
the present day.
VERTEBRATA.--
The great group of the Vertebrata comes last, with its chief
characteristic of the backbone structure, which advances in complexity
from the Fishes to the Higher Mammals.
=A Simplified Classification of the Vegetable Kingdom.=
SERIES. | FORMS FOUND FOSSIL.
---------------------+----------------------------------
I.--THALLOPHYTA |Sea-weeds: as Corallines and
| Calcareous Algae.
|
II.--BRYOPHYTA |Mosses, Liverworts.
|
III.--PTERIDOPHYTA |Fern-like plants, as Horse-tails,
| Club-mosses and true Ferns.
|
IV.--PTERIDOSPERMEAE|Oldest Seed-bearing plants,
| with fern-like foliage.
|
V.--GYMNOSPERMEAE |Plants with naked seeds, as Cycads
| (Fern-palms), Ginkgo
| (Maiden-hair Tree), and
| Conifers (Pine trees).
|
VI.--ANGIOSPERMEAE |Flowering plants, as Grasses,
| Lilies and all ordinary trees
| and plants.
=Characters of the Plant Series.=
THALLOPHYTA.--
The first series, the Thallophytes, are simple unicellular plants, and
occupy the same position in the vegetable kingdom as the Protozoa do in
the animal kingdom. Fossil remains of these organisms seem to be fairly
well distributed throughout the entire geological series, but, owing to
the soft structure of the fronds in most of the types, it is often a
matter of doubt whether we are dealing with a true thallophyte or not.
Many of the so-called sea-weeds (fucoids) may be only trails or markings
left by other organisms, as shell-fish and crustaceans.
BRYOPHYTA.--
The second series, the Bryophytes or moss plants, are represented in the
fossil state by a few unimportant examples.
PTERIDOPHYTA.--
The third series, the Pteridophytes, includes the Ferns found from
the Devonian up to the present day, Horse-tails and allied forms,
like _Equisetites_, and the Club-mosses and _Lepidodendron_ of the
Carboniferous period in various parts of the world.
PTERIDOSPERMEAE.--
The fourth series, the Pteridospermeae, comprises some of the earliest
seed-bearing plants, as _Alethopteris_ and _Neuropteris_. They occur in
rocks of Upper Palaeozoic age as far as known.
GYMNOSPERMEAE.
The fifth series, the Gymnospermeae, contains the most important types of
plants found fossil, especially those of the primary and secondary rocks:
they were more abundant, with the exception of the Coniferae, in the
earlier than in the more recent geological periods.
ANGIOSPERMEAE.--
The sixth series, the Angiospermeae, comprises all the Flowering Trees
and Plants forming the bulk of the flora now living, and is divided
into the kinds having single or double seed-leaves (Monocotyledones the
Dicotyledones respectively). This important group came into existence
towards the close of the Cretaceous period simultaneously with the higher
mammals, and increased in abundance until modern times.
CHAPTER III.
THE GEOLOGICAL EPOCHS: AND THE TIME RANGE OF FOSSILS.
=Superposition of Strata.--=
Fossils are chiefly found in rocks which have been formed of sediments
laid down in water, such as sandstone, shale and most limestones. These
rocks, broadly speaking, have been deposited in a horizontal position,
though really slightly inclined from shore to deep-water. One layer has
been formed above another, so that the oldest layer is at the bottom, and
the newest at the top, of the series (Fig. 11). Let us, for instance,
examine a cliff showing three layers: the lower, a sandstone, we will
Call A; the intermediate, a shale or clay bed, B; and the uppermost, a
limestone or marl, C (Fig. 12). In forming a conclusion about the relative
ages of the beds, we shall find that A is always older than B, and B than
C, provided no disturbance of the strata has taken place. For instance,
the beds once horizontally deposited may have been curved and folded
over, or even broken and thrust out of place, within limited areas; but
occurrences like these are extremely rare. Moreover, an examination of the
surrounding country, or of deep cuttings in the neighbourhood, will tell
us if there is any probability of this inversion of strata having taken
place.
[Illustration: =Fig. 11.--Horizontal Layers of Fossiliferous Clays and
Sands.=
In Sea Cliff, Torquay Coast, Victoria, looking towards Bird Rock.
(_Original_).
]
[Illustration: =Fig. 12.--Cliff-Section to Show Superposition of Strata.=
A = Sandstone. B = Shale. C = Limestone.]
This law of superposition holds good throughout the mass of sedimentary
rocks forming the crust of the earth.
(1). Thus, the position of the strata shows the relative ages of the beds.
=Differences in Fossil Faunas.--=
Turning once again to our ideal cliff section, if we examine the fossils
obtained from bed A, we shall find them differing in the number of kinds
or species common to the other beds above and below. Thus, there will
be more species alike in beds A and B or in B and C. In other words the
faunas of A and B are more nearly related than those of A and C. This is
explained by the fact that there is a gradual change in specific forms as
we pass through the time series of strata from below upwards; so that the
nearer one collecting platform is to another, as a rule, the stronger is
the community of species.
=Guide Fossils.--=
Certain kinds of fossils are typical of particular formations. They are
known as guide fossils, and by their occurrence help us to gain some idea
of the approximate age of rocks widely separated by ocean and continent.
Thus we find fossils typical of the Middle Devonian rocks in Europe, which
also occur in parts of Australia, and we therefore conclude that the
Australian rocks containing those particular fossils belong to the same
formation, and are nearly of the same age.
(2). The included fossils, therefore, give evidence of the age of the
beds.
=Value of Lithological Evidence.--=
The test of age by rock-structure has a more restricted use, but is of
value when taken in conjunction with the sequence of the strata and the
character of their included fossils.
To explain both the valuable and the uncertain elements of this last
method as a determinant of age, we may cite, for instance, the Upper
Ordovician slates of Victoria and New South Wales as an example of uniform
rock formation; whilst the yellow mudstones and the grey limestones of
the Upper Silurian (Yeringian series) of the same states, are instances
of diverse lithological structures in strata of similar age. A reference
in the latter case to the assemblages of fossils found therein, speedily
settles the question.
(3). Hence, the structure and composition of the rocks (lithology), gives
only partial evidence in regard to age.
=Strata Vertically Arranged.--=
The Stratigraphical Series of fossiliferous sediments comprises bedded
rocks from all parts of the world, which geologists arrange in a vertical
column according to age.
A general computation of such a column for the fossiliferous rocks of
Europe gives a thickness of about 14 miles. This is equivalent to a mass
of strata lying edgewise from Melbourne to Ringwood. The Australian
sediments form a much thicker pile of rocks, for they can hardly fall
short of 37 miles, or nearly the distance from Melbourne to Healesville.
This vertical column of strata was formed during three great eras of time.
The oldest is called the Primary or Palaeozoic ("ancient life"), in which
the animals and plants are of primitive types. This is followed by the
Secondary or Mesozoic ("middle life"), in which the animals and plants are
intermediate in character between the Palaeozoic and the later, Cainozoic.
The third era is the Tertiary or Cainozoic ("recent life"), in which the
animals and plants are most nearly allied to living forms. These great
periods are further subdivided into epochs, as the Silurian epoch; and
these again into stages, as the Yeringian stage.
Vertical Column of Fossiliferous Strata, Australia.
ERA. | EPOCHS IN | EQUIVALENT STRATA
| EUROPE. | IN AUSTRALIA.
-------------+---------------+-------------------------------
| HOLOCENE | Dunes, Beaches, and Shell-beds
| | now forming.
| |
| PLEISTOCENE | Raised Beaches, River Terraces,
| | Swamp Deposits
| | with Diprotodon, Cave
| | Breccias, Helix Sandstone.
| |
CAINOZOIC | PLIOCENE | Upper.--Estuarine beds of
or | | bores in the Murray basin,
TERTIARY | | Marine beds of
(Note 1). | | Limestone Creek, Glenelg
| | River, Vic. (Werrikooian).
| |
| | Lower.--Kalimnan red
| | sands (terrestrial) and
| | shell marls (marine) of
| | Victoria, Deep Leads
| | (fluviatile) in part, Upper
| | Aldingan of South
| | Australia.
-------------+---------------+-------------------------------
CAINOZOIC | MIOCENE | Deep Leads in part: Leaf-beds
or | | of Bacchus Marsh,
TERTIARY | | Dalton and Gunning.
(Continued). | | Janjukian Series of C.
| | Otway, Spring Creek, and
| | Table Cape. Batesford
| | Limestone. Polyzoal
| | Rock of Mt. Gambier and
| | the Nullarbor Plains.
| | Older Cainozoic of Murray
| | basin, Lower Aldingan
| | Series of S. Australia,
| | Corio Bay and
| | Bairnsdale Series.
| |
| OLIGOCENE | Shelly clays and leaf-beds
| | of the Balcombian Series
| | at Mornington; also
| | Shell-marls and clays
| | with Brown Coal, Altona
| | Bay, and lower beds at
| | Muddy Creek, W. Vict.
| |
| EOCENE | Probably no representatives.
-------------+---------------+-------------------------------
| |
MESOZOIC | CRETACEOUS | Upper.--Leaf-beds of Croydon,
or | | Q. Desert Sandstone,
SECONDARY | | Q. Radiolarian Rock, N.
| | Territory. Gin-gin Chalk,
| | W.A.
| |
| | Lower.--Rolling Downs
| | Formn., Q. Lake Eyre
| | beds, S.A.
| |
| JURASSIC | Marine.--Geraldton, W.A.
| |
| | Freshwater.--Carbonaceous
| | sandstone of S.
| | Gippsland, the Wannon,
| | C. Otway and Barrabool
| | Hills. Ipswich Series, Q.
| | Mesozoic of Tasmania,
| | Talbragar beds, N.S.W.
| |
| TRIASSIC | Upper leaf-beds at Bald
| | Hill, Bacchus Marsh, Vict.
| | Hawkesbury Series (Parramatta
| | Shales, Hawkesbury
| | Sandstone, Narrabeen
| | beds), N.S.W. Burrum
| | Beds, Q.
-------------+---------------+------------------------------
PALAEOZOIC | PERMIAN and | Carbopermian (Note 2),
or | CARBONIFEROUS,| Coal Measures of New
PRIMARY | UPPER | South Wales, W. Australia,
| | Queensland (Gympie
| | Series) and Tasmania.
| | Gangamopteris beds of
| | Bacchus Marsh, Vict.
| | Upper Carboniferous of
| | Clarence Town, N.S.W.
| CARBONIFEROUS,| Fish and Plant beds,
| LOWER | Mansfield, Vict. Grampian
| | sandstone; Avon
| | River sandstone, Vict.
| | (?) Star beds, Queensland.
| | Lepidodendron
| | beds of Kimberley, W.A.
| | (Note 3).
| DEVONIAN | Upper.--Sandstones of Iguana
| | Creek, with plant remains.
| | Lepidodendron
| | beds with Lingula, Nyrang
| | Creek, N.S. Wales.
| | Middle.--Fossiliferous marbles
| | and mudstones of
| | Buchan, Bindi and Tabberabbera,
| | Vict. Rocks
| | of the Murrumbidgee,
| | N.S. Wales, and of Burdekin,
| | Queensland.
| SILURIAN | Upper.--(Yeringian stage).--Lilydale,
| | Loyola, Thomson
| | River, and Waratah
| | Bay, Vict.; Bowning and
| | Yass (in part), N.S.
| | Wales; Queensland.
| | Lower (Melbournian
| | stage).--Melbourne,
| | Heathcote, Vict.; Bowning
| | and Yass (in part),
| | N.S. Wales. Gordon R.
| | Limestone.
| ORDOVICIAN, | Slates (graptolitic).--Victoria
| UPPER and | and New South
| LOWER | Wales. (?) Gordon River
| | Limestone, Tas., in part
| | (Note 4). Larapintine
| | series of Central Australia.
| CAMBRIAN | Mudstones and limestones
| | of Tasmania,
| | South Australia, Victoria
| | and W. Australia.
| PRE-CAMBRIAN | Fossiliferous rocks doubtful;
| | chiefly represented
| | by schistose and other
| | metamorphic rocks.
1.--The classification of the Cainozoics as employed here is virtually
the same as given by McCoy in connection with his work for the Victorian
Geological Survey. The writer has obtained further evidence to support
these conclusions from special studies in the groups of the cetacea,
mollusca and the protozoa. The alternative classification of the
cainozoics as given by one or two later authors, introducing the useful
local terminology of Hall and Pritchard for the various stages or assises
is as follows:--
TATE AND DENNANT. | HALL AND PRITCHARD.
Stages. | Stages.
|
Werrikooian Pleistocene | Werrikooian Pliocene.
Pliocene |
|
Kalimnan Miocene | Kalimnan Miocene.
|
Janjukian (?) Oligocene | Balcombian Eocene.
|
Balcombian Eocene | Janjukian
| and
Aldingan Eocene | Aldingan Eocene.
(lower beds | in part
at that loc.) |
2.--Or Permo-carboniferous. As the series is held by some authorities to
partake of the faunas of both epochs, it is preferable to use the shorter
word, which moreover gives the natural sequence. There is, however, strong
evidence in favour of using the term Permian for this important series.
3.--Mr. W. S. Dun regards the _Lepidodendron_ beds of W. Australia, New
South Wales and Queensland as of Upper Devonian age. There is no doubt,
from a broad view of the whole question as to the respective age of
these beds in Australia, that the one series is continuous, and probably
represents the Upper Devonian and the Lower Carboniferous of the northern
hemisphere.
4.--These limestones contain a fauna of brachiopods and corals which, at
present, seems to point to the series as intermediate between the older
Silurian and the Upper Ordovician.
Vertical Column of Fossiliferous Strata, New Zealand.
| EPOCHS IN | EQUIVALENT STRATA
ERA. | EUROPE. | IN NEW ZEALAND.
------------+------------------+----------------------
| HOLOCENE | River Alluvium. Beach
| | Sands and Gravel.
| |
CAINOZOIC | PLEISTOCENE | Raised Beaches. Older Gravel
or | | Drifts.
TERTIARY | | Moraines. Boulder Clays.
| |
| PLIOCENE | Upper.--Petane series. }
| | Lower.--Waitotara } Wanganui
| | and Awatere series. } system.
| |
| MIOCENE | Oamaru series.
| |
| OLIGOCENE | Waimangaroa series.
------------+------------------+---------------------------
| CRETACEOUS | Waipara series (of Hutton).
| |
MESOZOIC | JURASSIC | Mataura and Putataka
or | | series.
SECONDARY | |
| TRIASSIC | Wairoa, Otapiri and Kaihiku
| | series.
------------+------------------+-----------------------------
| PERMIAN | Aorangi (unfossiliferous)
| | series.
| |
| (?)CARBONIFEROUS | Maitai series (with Spirifer
| | and Productus.)
| |
| | (?)Te Anau series (unfossiliferous).
PALAEOZOIC | |
or | SILURIAN | Wangapeka series.
PRIMARY | |
| ORDOVICIAN | Kakanui series (with Lower
| | Ordovician graptolite
| | facies).
| |
| CAMBRIAN | Unfossiliferous. Metamorphic
| | schists of the Maniototo
| | series.
1.--Based for the most part, but with some slight modifications, on Prof.
J. Park's classification in "Geology of New Zealand," 1910.
[Illustration: =Fig. 13.=
Range-in-Time of Fossils in Australasian Sedimentary Rocks.
_E.M., del._]
]
[Illustration: =Fig. 14.--Skeleton of Diprotodon australis, Owen.=
Uncovered in Morass at Lake Callabonna, South Australia.
(_By permission of Dr. E. C. Stirling_).
]
CHAPTER IV.
HOW FOSSILS ARE FOUND: AND THE ROCKS THEY FORM.
As already noticed, it is the hard parts of buried animals and plants that
are generally preserved. We will now consider the groups of organisms,
one by one, and note the particular parts of each which we may reasonably
expect to find in the fossil state.
MAMMALS.--The bones and teeth: as the _Diprotodon_ remains of Lake
Callabonna in South Australia (Fig. 14), of West Melbourne Swamp,
Victoria, and the Darling Downs, Queensland. Rarely the skin, as in the
carcases of the frozen Mammoth of the tundras of Northern Siberia; or the
dried remains of the _Grypotherium_ of South American caves.
[Illustration: =Fig. 15.--Bird Bones.=
Exposed on Sand-blow at Seal Bay, King Island.
(_Photo by C. L. Barrett_).
]
[Illustration: =Fig. 16.--Impression of a Bird's Feather in Ironstone.=
About 2/3 nat. size. Of Cainozoic (? Janjukian) Age. Redruth, Victoria.
(_Nat. Mus. Coll._)
]
[Illustration: =Fig. 17.--Notochelone costata, Owen sp. (Anterior portion
of carapace.)=
About 1/4 nat. size. A Marine Turtle from the Lower Cretaceous of Flinders
River, Queensland.
(_Nat. Mus. Coll._)
]
BIRDS:--Bones: as the Moa bones of New Zealand and the Emu bones of the
King Island sand-dunes (Fig. 15). Very rarely the impressions of the
feathers of birds are found, as in the ironstone occurring in the Wannon
district of Victoria (Fig. 16), and others in fine clays and marls on
the continent of Europe and in England. Fossil eggs of sea-birds are
occasionally found in coastal sand-dunes of Holocene age.
REPTILES.--Skeletons of fossil turtles (_Notochelone_) are found in
Queensland (Fig. 17). Whole skeletons and the dermal armour (spines and
bony plates) of the gigantic, specialised reptiles are found in Europe,
North America, and in other parts of the world.
FISHES.--Whole skeletons are sometimes found in sand and clay rocks, as
in the Trias of Gosford, New South Wales (Fig. 18), and in the Jurassic
of South Gippsland. The ganoid or enamel-scaled fishes are common fossils
in the Devonian and Jurassic, notably in Germany, Scotland and Canada:
and they also occur in the sandy mudstone of the Lower Carboniferous of
Mansfield, Victoria.
INSECTS.--Notwithstanding their fragility, insects are often well
preserved as fossils, for the reason that their skin and wings consist
of the horny substance called chitin. The Tertiary marls of Europe are
very prolific in insect remains (Fig. 19). From the Miocene beds of
Florissant, Colorado, U.S.A., several hundred species of insects have been
described.
[Illustration: =Fig. 18.=
=A Fossil Fish with Ganoid Scales (Pristisomus crassus, A.S. Woodw.).=
About 1/2 nat. size. Trias (Hawkesbury Series), of Gosford, New South
Wales.
(_Nat. Mus. Coll._)
]
[Illustration: =Fig 19.--A Fossil Insect (Tipula sp.) in Amber.=
Nat. size. Oligocene beds; Baltic Prussia.
(_F.C. Coll._)
]
[Illustration: =Fig. 20.--A Fossil Lobster (Thalassina emerii, Bell).=
Slightly reduced. From the Pleistocene of Port Darwin, Northern Territory.
(_Nat. Mus. Coll._)
]
[Illustration: =Fig. 21.--An Ammonite (Desmoceras flindersi, McCoy sp.)=
Half nat. size. Showing complex sutures. L. Cretaceous: Marathon, Flinders
River, Queensland.
(_Nat. Mus. Coll._)
]
CRUSTACEA.--The outer crust, or exoskeleton, of these animals is often
hard, being formed of a compound of carbonate and phosphate of lime on
an organic, chitinous base. The earliest forms of this group were the
trilobites, commencing in Cambrian times, and of which there is a good
representative series in Australian rocks. Remains of crabs and lobsters
are found in the various Cainozoic deposits in Australia (Fig. 20), and
also in the Jurassic in other parts of the world.
MOLLUSCA.--The Cuttle-fish group (Cephalopoda, "head-footed"), is well
represented by the Nautilus-like, but straight _Orthoceras_ shells
commencing in Ordovician times, and, in later periods, by the beautiful,
coiled Ammonites (Fig. 21). The true cuttle-fishes possess an internal
bone, the sepiostaire, which one may see at the present day drifted on to
the sand at high-water mark on the sea-shore. The rod-like Belemnites are
of this nature, and occur abundantly in the Australian Cretaceous rocks of
South Australia and Queensland (Fig. 22).
[Illustration: =Fig. 22. Belemnites (Belemnites diptycha, McCoy).=
1/3 nat. size. Lower Cretaceous. Central South Australia.
(_Nat. Mus. Coll._)
]
[Illustration: =Fig. 23.--A Group of Lamp Shells (Magellania flavescens,
Lam. sp.)=
Attached to a Polyzoan.
About 1/3 nat. size. Dredged from Westernport, Victoria.
(_C.J. Gabriel Coll._)
]
Elephant-tusk shells (Scaphopoda) are frequent in our Tertiary beds: they
are also sparingly found in the Cretaceous, and some doubtful remains
occur in the Palaeozoic strata of Australia.
The shells of the ordinary mollusca, such as the snails, whelks, mussels,
and scallops, are abundant in almost all geological strata from the
earliest periods. Their calcareous shells form a covering which, after the
decay of the animal within, are from their nature among the most easily
preserved of fossil remains. There is hardly an estuary bed, lake-deposit,
or sea-bottom, but contains a more or less abundant assemblage of these
shell-fish remains, or testacea as they were formerly called ("testa," a
shell or potsherd). We see, therefore, the importance of this group of
fossils for purposes of comparison of one fauna with another (_antea_,
Fig. 1).
The chitons or mail-shells, by their jointed nature, consisting of a
series of pent-roof-shaped valves united by ligamental tissue, are nearly
always represented in the fossil state by separate valves. Fossil examples
of this group occur in Australia both in Palaeozoic rocks and, more
numerously, in the Cainozoic series.
[Illustration: =Fig. 24.--Zoarium of a Living Polyzoan. (Retepora)=
2/3 nat. size.
Flinders, Victoria.
(_F.C. Coll._)
]
[Illustration: =Fig. 25.--A Fossil Polyzoan (Macropora clarkei, T. Woods,
sp.)=
About 1/2 nat. size. Cainozoic (Balcombian). Muddy Creek, Victoria.
(_F.C. Coll._)
]
MOLLUSCOIDEA.--The Brachiopods or Lamp-shells consist generally of two
calcareous valves as in the true mollusca (Fig. 23), but are sometimes of
horny texture. Like the previous class, they are also easily preserved
as fossils. They possess bent, loop-like or spiral arms, called brachia,
and by the movement of fine ciliated (hair-like) processes on their
outer edges conduct small food particles to the mouth. The brachia are
supported by shelly processes, to which are attached, in the Spirifers,
delicate spirally coiled ribbons. These internal structures are often
beautifully preserved, even though they are so delicate, from the fact
that on the death of the animal the commissure or opening round the valves
is so tightly closed as to prevent the coarse mud from penetrating while
permitting the finer silt, and more rarely mineral matter in solution, to
pass, and subsequently to be deposited within the cavity. At the Murray
River cliffs in South Australia, a bed of Cainozoic limestone contains
many of these brachiopod shells in a unique condition, for the hollow
valves have been filled in with a clear crystal of selenite or gypsum,
through which may be seen the loop or brachial support preserved in its
entirety.
The Sea-mats or Polyzoa, represented by _Retepora_ (the Lace-coral)
(Fig. 24) and _Flustra_ (the Sea-mat) of the present sea-shore, have a
calcareous skeleton, or zoarium, which is easily preserved as a fossil.
Polyzoa are very abundant in the Cainozoic beds of Australia, New Zealand,
and elsewhere (Fig. 25). In the Mesozoic series, on the other hand, they
are not so well represented; but in Europe and North America they play an
important part in forming the Cretaceous and some Jurassic strata by the
abundance of their remains.
WORMS (VERMES).--The hard, calcareous tubes of Sea-worms, the Polychaeta
("many bristles") are often found in fossiliferous deposits, and sometimes
form large masses, due to their gregarious habits of life; they also occur
attached to shells such as oysters (Fig. 26). The burrows of the wandering
worms are found in Silurian strata in Australia; and the sedentary forms
likewise occur from the Devonian upwards.
ECHINODERMATA.--Sea-urchins (Echinoidea) possess a hard, calcareous,
many-plated test or covering and, when living are covered with spines
(Fig. 27). Both the tests and spines are found fossil, the former
sometimes whole when the sediment has been quietly thrown down upon them;
but more frequently, as in the Shepherd's crown type (_Cidaris_), are
found in disjointed plates, owing to the fact that current action, going
on during entombment has caused the plates to separate. The spines are
very rarely found attached to the test, more frequently being scattered
through the marl or sandy clay in which the sea-urchins are buried. The
best conditions for the preservation of this group is a marly limestone
deposit, in which case the process of fossilisation would be tranquil
(Fig. 28).
[Illustration: =Fig. 26.--Fossil Worm Tubes (? Serpula.)=
Attached to a Pecten.
Slightly Enlarged. Cainozoic (Balcombian). Muddy Creek, Hamilton, Victoria.
(_F. C. Coll._)
]
[Illustration: =Fig. 27.=
=A Regular Sea-Urchin (Strongylocentrotus erythrogrammus, Val.)=
About 2/3 nat. size. Showing Spines attached. Living. Victoria.
(_F. C. Coll._)
]
[Illustration: =Fig. 28.--A Fossil Sea-Urchin (Linthia antiaustralis,
Tate).=
Test denuded of Spines.
About 2/3 nat. size. Cainozoic (Janjukian): Curlewis, Victoria.
(_Nat. Mus. Coll._)
]
[Illustration: =Fig. 29.--Ophioderma egertoni, Broderip, sp.=
About 1/2 nat. size. A Brittle Star from the Lias of Seaton, Devon,
England.
(_Nat. Mus. Coll._)
]
The true Starfishes (Asteroidea), are either covered with calcareous
plates, or the skin is hardened by rough tubercles; and these more lasting
portions are preserved in rocks of all ages. The shape of the animal is
also often preserved in an exquisite manner in beds of fine mud or clay.
The Brittle-stars (Ophiuroidea) have their body covered with hard,
calcareous plates. Their remains are found in rocks as old as the
Ordovician in Bohemia but their history in Australia begins with the
Silurian period (Fig. 29). From thence onward they are occasionally found
in successive strata in various parts of the world.
The bag-like echinoderms (Cystidea) form a rare group, restricted to
Palaeozoic strata. The plates of the sack, or theca, and those of the
slender arms are calcareous, and are capable of being preserved in the
fossil state. A few doubtful remains of this group occur in Australia.
The bud-shaped echinoderms (Blastoidea) also occur chiefly in Devonian and
Carboniferous strata. This is also a rare group, and is represented by
several forms found only in New South Wales and Queensland.
The well known and beautiful fossil forms, the Stone-lilies (Crinoidea)
have a very extended geological history, beginning in the Cambrian; whilst
a few species are living in the ocean at the present day. The many-jointed
skeleton lends itself well to fossilisation, and remains of the crinoids
are common in Australia mainly in Palaeozoic strata (Fig. 30). In Europe
they are found abundantly also in Jurassic strata, especially in the Lias.
[Illustration: =Fig. 30.=
=A Fossil Crinoid (Taxocrinus simplex, Phillips sp.)=
About 1/2 nat. size.
Wenlock Limestone (Silurian), Dudley, England.
(_Nat. Mus. Coll._)
]
[Illustration: =Fig. 31.--Graptolites on Slate (Tetragraptus fruticosus,
J. Hall, sp.)=
Nat. Size. Lower Ordovician. Bendigo, Victoria.
(_Nat. Mus. Coll._)
]
[Illustration: =Fig. 32.=
=Polished Vertical Section of a Stromatoporoid. (Actinostroma).=
Nat. size. Middle Devonian. South Devon, England.
(_F.C. Coll._)
]
HYDROZOA.--The Graptolites ("stone-writing") have a chitinous skin
(periderm) to the body or hydrosome, which is capable of preservation to
a remarkable degree; for their most delicate structures are preserved on
the surfaces of the fine black mud deposits which subsequently became
hardened into slates. In Australia graptolites occur from the base of the
Ordovician to the top of the Silurian (Fig. 31).
Another section of the Hydrozoa is the Stromatoporoidea. These are
essentially calcareous, and their structure reminds one of a dense coral.
The polyps build their tiers of cells (coenosteum) in a regular manner,
and seem to have played the same part in the building of ancient reefs in
Silurian, Devonian and Carboniferous times as the Millepora at the present
day (Fig. 32).
[Illustration: =Fig. 33.--Fossil Corals (Favosites).=
Photograph of a Polished Slab, 2/3 nat. size. In Devonian Limestone,
Buchan, Victoria.]
[Illustration: =Fig. 34.--Siliceous Skeleton of a Living Hexactinellid
Sponge.=
Probably Chonelasma.
× 4. Mauritius. (Viewed in Two Directions.)
(_F.C. Coll._)
]
ANTHOZOA.--The true Corals have a stony skeleton, and this is capable of
easy preservation as a fossil. There is hardly any fossiliferous stratum
of importance which has not its representative corals. In Australia their
remains are especially abundant in the Silurian, Devonian (Fig. 33), and
Carboniferous formations, and again in the Oligocene and Miocene.
SPONGES.--The framework of the sponge may consist either of flinty,
calcareous, or horny material (Fig. 34). The two former kinds are well
represented in our Australian rocks, the first appearing in the Lower
Ordovician associated with graptolites, and again in the Cretaceous and
Tertiary rocks (Fig. 35); whilst the calcareous sponges are found in
Silurian strata, near Yass, and again in the Cainozoic beds of Flinders,
Curlewis and Mornington in Victoria.
[Illustration: =Fig. 35.=
=Spicules of a Siliceous Sponge (Ecionema newberyi, McCoy sp.)=
Highly magnified. Cainozoic Shell-Marl.
Altona Bay Coal-Shaft.]
[Illustration: =Fig. 36.=
=Nummulites (N. gizehensis Ehr. var. champollioni, de la Harpe).=
About nat. size. Middle Eocene Limestone. Cyrene, Northern Africa.
(_Coll. by Dr. J. W. Gregory_).
]
PROTOZOA.--The important and widely-distributed group of the Foraminifera
("hole-bearers") belonging to the lowest phylum, the Protozoa, generally
possess a calcareous shell. The tests range in size from tiny specks of
the fiftieth of an inch in diameter, to the giant Nummulite, equalling a
five shilling piece in size (Fig. 36). Their varied and beautiful forms
are very attractive, but their great interest lies in their multifarious
distribution in all kinds of sediments: they are also of importance
because certain of the more complex forms indicate distinct life zones,
being restricted to particular strata occurring in widely-separated areas.
[Illustration: =Fig. 37.--Siliceous Skeletons of Radiolaria.=
× 58. Late Cainozoic Age. Bissex Hill, Barbados, West Indies.
(_F.C. Coll._)
]
Members of the allied order of the Radiolaria have a flinty shell (Fig.
37); and these organisms are often found building up siliceous rocks such
as cherts (Fig. 38).
PLANTS.--The harder portions of plants which are found in the fossil
state are,--the wood, the coarser vascular (vessel-bearing) tissue of the
leaves, and the harder parts of fruits and seeds.
Fossil wood is of frequent occurrence in Palaeozoic, Mesozoic and
Cainozoic strata in Australia, as, for instance, the wood of the trees
called _Araucarioxylon_ and _Dadoxylon_ in the Coal measures of New South
Wales (see _antea_, Fig. 3).
[Illustration: =Fig. 38.--Radiolaria in Siliceous Limestone.=
× 40. Middle Devonian: Tamworth, New South Wales.
(_From Prof. David's Collection_).
]
[Illustration: =Fig. 39.--Travertin Limestone with Leaves of Beech
(Fagus).=
Nat. size. Pleistocene: near Hobart, Tasmania.
(_Nat. Mus. Coll._)
]
Fossil leaves frequently occur in pipe-clay beds, as at Berwick, Victoria,
and in travertine from near Hobart, Tasmania (Fig. 39). Fossil fruits are
found in abundance in the ancient river gravels at several hundreds of
feet below the surface, in the "deep leads" of Haddon, Victoria, and other
localities in New South Wales, Queensland and Tasmania.
[Illustration: =Fig. 40--Freshwater Limestone with Shells (Bulinus).=
About 4/5 nat. size. Mount Arapiles, Western Victoria.
(_Nat. Mus. Coll._)
]
[Illustration: =Fig. 41.--Fossiliferous Mudstone of Silurian (Yeringian)
Age.=
With Brachiopods. About 2/3 nat. size. Near Lilydale, Victoria.
(_F.C. Coll._)
]
FOSSILIFEROUS ROCKS.
Section I.--ARGILLACEOUS ROCKS.
Under this head are placed the muds, clays, mudstones, shales and slates.
MUDS are usually of a silty nature, that is, containing a variable
proportion of sand (quartz) grains. Such are the estuarine muds of
Pleistocene and Recent age, containing brackish water foraminifera and
ostracoda, and those shells of the mollusca usually found associated with
brackish conditions. Lacustrine mud can be distinguished by the included
freshwater shells, as _Limnaea_, _Coxiella_ (brackish), _Cyclas_ and
_Bulinus_, as well as the freshwater ostracoda or cyprids (Fig. 40).
CLAYS are tenacious mud deposits, having the general composition of a
hydrous silicate of alumina with some iron. When a clay deposit tends to
split into leaves or laminae, either through moderate pressure or by the
included fossil remains occupying distinct planes in the rock, they are
called SHALES.
Clays and Shales of marine origin are often crowded with the remains
of mollusca. The shells are sometimes associated with leaves and other
vegetable remains, if forming part of an alternating series of freshwater
and marine conditions. An example of this type of sediments is seen in the
Mornington beds of the Balcombian series in Victoria.
MUDSTONE is a term applied to a hardened clay deposit derived from the
alteration of an impure limestone, and is more often found in the older
series of rocks. Mudstones are frequently crowded with fossils, but
owing to chemical changes within the rock, the calcareous organisms are
as a rule represented by casts and moulds. At times these so faithfully
represent the surface and cavities of the organism that they are almost
equivalent to a well preserved fossil (Fig. 41).
SLATE.--When shale is subjected to great pressure, a plane of regular
splitting called cleavage is induced, which is rarely parallel to the
bedding plane or surface spread out on the original sea-floor: the
cleavage more often taking place at an appreciable angle to the bedding
plane. The graptolitic rocks of Victoria are either shales or slates,
according to the absence or development of this cleavage structure in the
rock.
Section II.--SILICEOUS ROCKS.
In this group are comprised all granular quartzose sediments, and organic
rocks of flinty composition.
SANDSTONES.--Although the base of this type of rock is formed of quartz
sand, it often contains fossils. Owing to its porous nature, percolation
of water containing dissolved CO_{2} tends to bring about the solution
of the calcareous shells, with the result that only casts of the shells
remain.
FLINTS and CHERTS.--These are found in the form of nodules and bands in
other strata, principally in limestone. In Europe, flint is usually found
in the Chalk formation, whilst chert is found in the Lower Greensands,
the Jurassics, the Carboniferous Limestone and in Cambrian rocks. In
Australia, flint occurs in the Miocene or Polyzoal-rock formation of Mount
Gambier, Cape Liptrap and the Mallee borings. Flint is distinguished
from chert by its being black in the mass, often with a white crust,
and translucent in thin flakes; chert being more or less granular in
texture and sub-opaque in the mass. Both kinds appear to be formed as
a pseudomorph or replacement of a portion of the limestone stratum by
silica, probably introduced in solution as a soluble alkaline silicate.
Both flint and chert often contain fossil shells and other organic
remains, such as radiolaria and sponge-spicules, which can be easily seen
with a lens in thin flakes struck off by the hammer.
DIATOMITE is essentially composed of the tiny frustules or flinty cases
of diatoms (unicellular algae), usually admixed with some spicules of the
freshwater sponge, _Spongilla_. It generally forms a layer at the bottom
of a lake bed (Fig. 42).
[Illustration: =Fig. 42.--Diatomaceous Earth. (Post-Tertiary).=
Containing freshwater forms, as Pinnularia, Cocconeis and Synedra. × 150.
Talbot, Victoria.]
Section III.--CALCAREOUS ROCKS.
LIMESTONES FORMED BY ORGANISMS.--Organic limestones constitute by far
the most important group of fossiliferous rocks. Rocks of this class are
composed either wholly of carbonate of lime, or contain other mineral
matter also, in varying proportion. Many kinds of limestones owe their
origin directly to the agency of animals or plants, which extracted the
calcareous matter from the water in which they lived in order to build
their hard external cases, as for example the sea-urchins; or their
internal skeletons, as the stony corals. The accumulated remains of these
organisms are generally compacted by a crystalline cement to form a
coherent rock.
The chief groups of animals and plants forming such limestone rocks are:--
(a) _FORAMINIFERA._--Example. Foraminiferal limestone as the Nummulitic
limestone of the Pyramids of Egypt, or the _Lepidocyclina_ limestone of
Batesford, near Geelong, Victoria (Fig. 43).
[Illustration: =Fig. 43.=
=Limestone composed of Polyzoa and Foraminifera (Lepidocyclina).=
× 6. Cainozoic (Janjukian). Batesford, near Geelong, Victoria.
(_F.C. Coll._)
]
(b) _CORALS._--Ex. "Madrepore limestone," or Devonian marble, with
_Pachypora_. Also the Lilydale limestone, with _Favosites_, of Silurian
age, Victoria (Fig. 44).
[Illustration: =Fig. 44.--A Fossil Coral (Favosites grandipora).=
2/3 nat. size. From the Silurian of Lilydale, Victoria.
(_F.C. Coll._).
]
[Illustration: =Fig. 45.--Polished Slab of Marble formed of Joints of
Crinoids.=
About 2/3 nat. size. Silurian.
Toongabbie, Gippsland, Victoria.
(_Nat. Mus. Coll._)
]
(c) _STONE-LILIES._--Ex. Crinoidal or Entrochial limestone, Silurian,
Toongabbie, Victoria (Fig. 45). Also the Carboniferous or Mountain
limestone, Derbyshire, England.
(d) _WORM-TUBES.-_-Ex. Serpulite limestone of Hanover, Germany. _Ditrupa_
limestone of Torquay and Wormbete Creek, Victoria.
(e) _POLYZOA._---Ex. Polyzoal limestone, as the so-called Coralline Crag
of Suffolk, England; and the Polyzoal Rock of Mount Gambier, S. Australia.
(f) _BRACHIOPODA._--Ex. Brachiopod limestone of Silurian age, Dudley,
England. _Orthis_ limestone of Cambrian age, Dolodrook River, N. E.
Gippsland.
(g) _MOLLUSCA._--Ex. Shell limestone, as the _Turritella_ bed of Table
Cape, Tasmania, and of Camperdown, Victoria (Fig. 46), or the Purbeck
Marble of Swanage, Dorset, England.
[Illustration: =Fig. 46.--Turritella Limestone.=
(T. acricula, Tate); 3/4 nat. size. Cainozoic.
Lake Bullen Merri, near Camperdown, Victoria.]
[Illustration: =Fig. 47.--Limestone composed of the Valves of an Ostracod
(Cypridea).=
Upper Jurassic. × 9.
Swanage, Dorset, England.]
(h) _OSTRACODA._--Ex. Cypridiferous limestone, formed of the minute valves
of the bivalved ostracoda, as that of Durlston, Dorset, England (Fig. 47).
(i) _CADDIS FLY LARVAE._--Ex. Indusial limestone, formed of tubular cases
constructed by the larvae of the Caddis fly (_Phryganea_). Occurs at
Durckheim, Rhine District, Germany.
(j) _RED SEAWEEDS._--Ex. Nullipore limestone, formed by the stony thallus
(frond) of the calcareous sea-weed _Lithothamnion_, as in the Leithakalk,
a common building stone of Vienna.
(k) _GREEN SEAWEEDS._--Ex. _Halimeda_ limestone, forming large masses of
rock in the late Cainozoic reefs of the New Hebrides (Fig. 48).
(l) (?) _BLUE-GREEN SEAWEEDS._--Ex. _Girvanella_ limestone, forming the
Peagrit of Jurassic age, of Gloucester, England.
Section IV.--CARBONACEOUS and MISCELLANEOUS ROCKS.
COALS and KEROSENE SHALES (Cannel Coal).--These carbonaceous rocks are
formed in much the same way as the deposits in estuaries and lagoon
swamps. They result from the sometimes vast aggregation of vegetable
material (leaves, wood and fruits), brought down by flooded rivers from
the surrounding country, which form a deposit in a swampy or brackish
area near the coast, or in an estuary. Layer upon layer is thus formed,
alternating with fine mud. The latter effectually seals up the organic
layers and renders their change into a carbonaceous deposit more certain.
When shale occurs between the coal-layers it is spoken of as the
under-clay, which in most cases is the ancient sub-soil related to the
coal-layer immediately above. It is in the shales that the best examples
of fossil ferns and other plant-remains are often found. The coal itself
is composed of a partially decomposed mass of vegetation which has become
hardened and bedded by pressure and gradual drying.
Spore coals are found in thick deposits in some English mines, as at
Burnley in Yorkshire. They result from the accumulation of the spores of
giant club-mosses which flourished in the coal-period. They are generally
referred to under the head of Cannel Coals. The "white coal" or Tasmanite
of the Mersey Basin in Tasmania is an example of an impure spore coal with
a sandy matrix (Fig. 49).
[Illustration: =Fig. 48.=
=Rock composed of the calcareous joints of Halimeda (a green sea-weed).=
About 2/3 nat. size. Late Cainozoic. Reef-Rock. Malekula, New Hebrides.
(_Coll. by Dr. D. Mawson._)
]
[Illustration: =Fig. 49.--Thin Slices of "White Coal" or "Tasmanite,"
showing crushed Megaspores.=
× 28. Carbopermian. Latrobe, Tasmania.
(_F. C. Coll._)
]
[Illustration: =Fig. 50.--Thin Slice of "Kerosene Shale."=
× 28. Carbopermian. Hartley, New South Wales.
(_F. C. Coll._)
]
[Illustration: =Fig. 51.--Bone Bed, with Fish and Reptilian Remains.=
About 1/2 nat. size. (Rhaetic). Aust Cliff, Gloucestershire, England.
(_Nat. Mus. Coll._)
]
The Kerosene Shale of New South Wales is related to the Torbanite of
Scotland and Central France. It occurs in lenticular beds between the
bituminous coal. It is a very important deposit, commercially speaking,
for it yields kerosene oil, and is also used for the manufacture of gas.
The rock is composed of myriads of little cell-bodies, referred to as
_Reinschia_, and first supposed to be allied to the freshwater alga,
_Volvox_; but this has lately been questioned, and an alternative view is
that they may be the megaspores of club-mosses (Fig. 50).
The coals of Jurassic age in Australia are derived from the remains of
coniferous trees and ferns; and some beautiful examples of these plants
may often be found in the hardened clay or shale associated with the coal
seams.
The Brown Coals of Cainozoic or Tertiary age in Australia are still but
little advanced from the early stage, lignite. The leaves found in them
are more or less like the present types of the flora. The wood is found
to be of the Cypress type (_Cupressinoxylon_). In New Zealand, however,
important deposits of coal of a more bituminous nature occur in the
Oligocene of Westport and the Grey River Valley, in the Nelson District.
BONE BEDS.--The bones and excreta of fish and reptiles form considerable
deposits in some of the sedimentary formations; especially those partly
under the influence of land or swamp conditions. They constitute a kind of
conglomerate in which are found bone-fragments and teeth (Fig. 51). These
bone-beds are usually rich in phosphates, and are consequently valuable
as a source of manure. The Miocene bone-bed with fish teeth at Florida,
U.S.A., is a notable example. The nodule bed of the Victorian Cainozoics
contains an assemblage of bones of cetaceans (whales, etc.).
[Illustration: =Fig. 52.--Bone Breccia, with remains of Marsupials.=
About 3/4 nat. size. Pleistocene.
Limeburners Point, Geelong, Victoria.
(_Nat. Mus. Coll._)
]
BONE BRECCIAS.--These are usually formed of the remains of the larger
mammals, and consist of a consolidated mass of fragments of bones and
teeth embedded in a calcareous matrix. Bone-breccias are of frequent
occurrence on the floors of caves which had formerly been the resort of
carnivorous animals, and into which they dragged their prey. The surface
water percolating through the overlying calcareous strata dissolved a
certain amount of lime, and this was re-deposited on the animal remains
lying scattered over the cave floor. A deposit so formed constitutes a
stalagmite or floor encrustation. As examples of bone-breccias we may
refer to the limestone at Limeburners Point, Geelong (Fig. 52); and the
stalagmitic deposits of the Buchan Caves.
IRONSTONE.--Rocks formed almost entirely of limonite (hydrated peroxide of
iron) are often due to the agency of unicellular plants known as diatoms,
which separate the iron from water, and deposit it as hydrous peroxide
of iron within their siliceous skeletons. In Norway and Sweden there are
large and important deposits of bog iron-ore, which have presumably been
formed in the beds of lakes.
[Illustration: =Fig. 53.=
=Cainozoic Ironstone with Leaves (Banksia ? marginata, Cavanilles).=
Slightly enlarged. Below Wannon Falls, Redruth, Victoria.]
Clay ironstone nodules (sphaerosiderite) have generally been formed
as accretions around some decaying organic body. Many clay ironstone
nodules, when broken open, reveal a fossil within, such as a coprolitic
body, fern frond, fir-cone, shell or fish.
Oolitic ironstones are composed of minute granules which may have
originally been calcareous grains, formed by a primitive plant or alga,
but since replaced by iron oxide or carbonate.
The Tertiary ironstone of western Victoria is found to contain leaves,
which were washed into lakes and swamps (Fig. 53); and the ferruginous
groundmass may have been originally due to the presence of diatoms, though
this yet remains to be proved.
PART II.--SYSTEMATIC PALAEONTOLOGY.