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1



LIBRARY

OF THE

UNIVERSITY OF CALIFORNIA.

,

Class



THE STUDENT'S HANDBOOK



OF



STRATIGRAPHICAL GEOLOGY






The Publisher intends this book
to be sold to the Public at the
advertised price, and the terms
on which it is supplied to the
Trade will not allow of discount.




THE STUDENT'S HANDBOOK



OF



STRATIGRAPHICAL GEOLOGY



BY



A. J. JUKES-BROWNE, B.A., F.G.S.


LATE OF THE GEOLOGICAL SURVEY OF ENGLAND AND WALES ; AUTHOR

OF THE 'STUDENT'S HANDBOOK OF PHYSICAL GEOLOGY,'

THE 'BUILDING OF THE BRITISH ISLES,' ETC.



ILLUSTRATED WITH MAPS, DIAGRAMS, AND FIGURES OF FOSSILS



Y
'OF THE

UNIVERSITY

OF



LONDON: EDWARD STANFORD

12, 13, 14 LONG ACRE, \V.C.

1902

All rights reserved



GENERAL






PEEFACE

THIS volume is based on the Student's Handbook of Histoi'ical
Geology, published by Messrs. G. Bell and Sons, and may be
regarded as a second edition of that book, but it has been
entirely re-written, and its title is altered from Historical
Geology to Stratigraphical Geology, because it is considered
that the latter is the more customary designation of the
subject, though the former is, strictly speaking, the more
accurate and comprehensive term.

Great advances have been made in Geology during the
last fifteen years, and a much larger mass of information has
to be considered by the compiler of such a handbook as this
than was available prior to 1886. The labour of compilation
is consequently greater, and yet there are still many parts of
Great Britain which have not yet been completely explored,
and there are still important questions upon which authorities
differ, questions not only of nomenclature and grouping, but
also regarding the actual age and correlation of certain rock-
groups. Hence what was written on this point in 1886
remains equally true at the present time, and may be con-
veniently repeated, for " under these circumstances the com-
piler of a student's handbook frequently finds it difficult to
decide whether he should follow some one authority or
endeavour to extract truth and justice from conflicting state-
ments, and often he is forced to form his own opinion on the

104731



vi STRATIGRAPHICAL GEOLOGY

facts brought forward by different observers." In many cases,
however, I have mentioned the existence of an opinion differ-
ing from the one which I have adopted.

The general plan of the original book has been retained,
but new features in the present volume are :

1. The expansion of the chapters dealing with the
Palaeozoic rocks.

2. The insertion of small geological maps of some of the
more important districts in England and Wales. These are
in black and white, but every reader can colour them for
himself, and he should approximate his colours to those used
by the Geological Survey.

3. An increased number of other illustrations, both of
fossils and of the diagrams which are usually called "hori-
zontal sections."

Most of the maps have been prepared in Mr. Stanford's
establishment from sketches supplied by myself, and where
other sources are not mentioned they are based on the maps
of the Geological Survey.

Many of the figures of fossils are borrowed from those in
the sixth edition of Sir A. C. Ramsay's Physical Geology and
Geography of Great Britain, and many of the other illustrations
are figures which have appeared in the publications of the
Geological Society and the Geologist's Association ; for the
use of these my thanks are due to the Councils of both
Societies, and to the authors of the papers from which they
are taken.

The sections on Palseogeography have been brought up to
date, but most of them have been abridged because this part
of the subject has been dealt with in a separate volume
entitled the Building of the British Islands, of which a second
edition was issued in 1892, and is still purchaseable.



PKEFACE Vil

I am indebted to many friends and correspondents for
suggestions and assistance in the preparation of the book,
and especially to Mr. J. E. Marr for reading the manuscript
of the Palaeozoic chapters, and to Mr. H. Woods for reading
the first proofs of the whole work, and for many valuable
suggestions and emendations, particularly in regard to palseon-
tological matters. I desire also to express my acknowledg-
ments for information and assistance given by Dr. Wheelton
Hind, Mr. W. A. E. Ussher, Professor Lloyd Morgan, Professor
H. S. Reynolds, Mr. F. W. Manner, Mr. F. A. Bather, Mr.
Bernard Hobson, and Mr. J. G. Goodchild.

A. J. JUKES-BROWNE.

TORQUAY, January 1902.



CONTENTS

CHAPTEE I

INTRODUCTION

PAGE

Scope of the subject The succession of stratified rocks Table of

the classification of animals . ... . . . 1

CHAPTER II

ORIGIN AND SUCCESSION OF SPECIES

Origin of species Imperfection of the geological record Succession

of life-forms . . . . 7

CHAPTER III

THE CLASSIFICATION OF ROCK-GROUPS

Systems Nomenclature Definition and delimitation of systems

Stages and their subdivision . . . . . . . 15

CHAPTER IV

THE CORRELATION OF ROCK-GROUPS

Distribution of marine creatures Zoological provinces Inferences

Synchronism and homotaxis ...... 27

CHAPTER V

THE LITERATURE OF HISTORICAL GEOLOGY

Maps Publications on Stratigraphy, on Palaeontology, on Palaeo-

geography 34

ix



x STKATIGRAPHICAL GEOLOGY

CHAPTER VI

PRE-CAMBRIAN SYSTEMS

PAGE

General remarks Stratigraphy, Scotland, Ireland, Wales, Shrop-
shire, Malvern Hills, Warwick, and Leicester Foreign Pre-
Cambrian rocks Origin and method of formation ... 43

CHAPTER VII

THE CAMBRIAN SYSTEM

Nomenclature of Lower Palaeozoic rocks Classification of Cam-
brian rocks Life of the period Stratigraphy in England,
Scotland, and Ireland Continental equivalents Volcanic
rocks Physical geography of the period .... 64

CHAPTER VIII

THE OKDOVICIAN SYSTEM

Nomenclature Life of the period Stratigraphy in England,
Scotland, and Ireland Continental equivalents Ordovician
volcanoes Geography of the British region . . . . 97

CHAPTER IX

THE SILURIAN SYSTEM

Nomenclature Life of the period Stratigraphy in England, Scot-
land, and Ireland Volcanic rocks Continental equivalents-
Physical and geographical conditions 133

CHAPTER X

DEVONIAN AND OLD RED SANDSTONE SYSTEM

Classification and subdivisions A. DEVONIAN TYPE : Life of the
period Stratigraphy in Belgium and England. B. OLD RED
SANDSTONE TYPE : Fossils Stratigraphy in England, Scot-
land, and Ireland Volcanic rocks Geography of the period . 169

CHAPTER XI

THE CARBONIFEROUS SYSTEM

A. LOWER CARBONIFEROUS SERIES : Range and relation to under-
lying rocks Life of the epoch Stratigraphy in England,



CONTENTS xi

.Scotland, and Ireland Volcanic rocks. B. UPPER CARBON-
IFEROUS SERIES : Subdivisions Coal-fields Life of the epoch
Stratigraphy in England, Scotland, and Ireland Russia
Physical and geographical conditions of Carboniferous time 203



CHAPTER XII

THE PERMIAN SYSTEM

Classification and nomenclature Life of the period Stratigraphy
in England and Ireland Permian of Europe and Asia
Physical and geographical conditions . . . 276

CHAPTER XIII

THE TRIASSIC SYSTEM

A. TRIAS OF THE ALPINE REGION. B. TRIAS OF GERMANY AND
BRITAIN: Triassic fossils Stratigraphy of German Trias-
Stratigraphy of British Trias Volcanic rocks Physical con-
ditions of the British region .... 296

CHAPTER XIV

THE JURASSIC SYSTEM

Xomenclature and divisions. A. THE LIAS OR LOWER JURASSIC
SKRIES : Lower Jurassic life Stratigraphy in England, Scot-
land, and Ireland. B. MIDDLE JURASSIC SERIES : Subdivisions
Life of the period Stratigraphy in England and Scotland.
C. UPPER JURASSIC SERIES : Subdivisions Life of the epoch
Stratigraphy in England and Scotland Physical geography
of Jurassic time ...... 339



CHAPTER XV

THE CRETACEOUS SYSTEM

Subdivisions Relation to underlying rocks Life of the Cretaceous
period. A. LOWER CKETACEOUS SERIES : Characteristic fossils
Stratigraphy in France and Switzerland ; in England.
B. UPPER CRETACEOUS SERIES : Characteristic fossils Strati-
graphy in England, Ireland, Scotland, and France Geo-
graphical and physical conditions of Cretaceous time . 393



xii STRATIGRAPHICAL GEOLOGY

CHAPTER XVI

TERTIARY TIME THE PALAEOGENE SYSTEM

PAGE

Nomenclature and divisions Life of the Palaeogene period.
A. EOCENE SERIES : Extent and English subdivisions
Characteristic fossils Stratigraphy in England, Ireland, .and
Scotland Continental equivalents Physical and geographical
conditions. B. OLIGOCENE SERIES : Divisions Characteristic
fossils Stratigraphy in England, Belgium, France, and
Switzerland Physical and geographical conditions . . 458

CHAPTER XVII

THE NEOGENE SYSTEM

A. MIOCENE SERIES : Life of the epoch Stratigraphy in France,
Belgium, Switzerland, Austria, Italy, and Greece. B. PLIOCENE
SERIES : Life of the epoch Stratigraphy in England, Belgium,
and Holland Physical geography of the British area in Mio-
cene and Pliocene times ........ 506

CHAPTER XVIII

THE NEOGENE SYSTEM continued

C. PLEISTOCENE SERIES : Life of the epoch. The Glacial Deposits :
Stratigraphy in East Anglia, Lincolnshire, and Yorkshire,
north-west of England, Northern England, Scotland, Ireland.
The Non-Glacial Deposits : Cave-deposits, River-gravels, Raised
beaches, Alluvial levels Geographical and climatal conditions
of Pleistocene time ........ 538

INDEX 575




CHAPTER I

INTRODUCTION

Scope of the Subject. In most manuals of Geology this
branch of the subject is called Stratigraphical Geology because it
chiefly consists in the description of the great stratified series of
rocks which make up the mass of the earth's crust. It is some-
times called Historical Geology, because it should comprise not
only a description of the various rocks which were formed during
each period of the world's history, but also some account of the
forms of life which are entombed in these rocks, with a sketch of
the physical geography of the earth during each period, and a notice
of the changes in the relative position of land and sea which took
place from time to time ; all this should be made as complete as
the imperfection of the geological documents will allow.

Neither designation is quite satisfactory, but either of them
may be used so long as it is understood to mean a geological history
a collation of the knowledge acquired in all the other depart-
ments of the Science, and its application to elucidate the history
of the earth, or of a portion of the earth, from the earliest time
of which any records exist down to the time of human history.

At present there are only a few limited areas of the earth's
surface about which we have anything like a full Stratigraphical
knowledge, and much remains to be learnt even in the areas about
which we know most. Geological History, therefore, is yet in its
infancy ; but enough is now known of the Stratigraphical geology
of Europe to make it possible to give an outline of its geological
history, and American geologists are rapidly making it possible to
do the same for North America. In this volume, however, we
shall not travel beyond the limits of the British Islands, except
where our own records are deficient, or where some knowledge of
continental geology is necessary to the proper understanding of the
changes that took place in Britain.

B



2 STRATIGRAPHICAL GEOLOGY

The Succession of Stratified Bocks. The general
principles on which historical geology is founded are easily
understood, and the manner in which the order and succession of
rock-groups is established will now be briefly explained. The
mere succession of strata in any district or country, however, is
one thing, and the grouping of such strata into larger systems,
representing definite geological periods, is another thing, and one
which requires consideration from several points of view. A
subsequent chapter, therefore, will be devoted to a discussion of
the principles upon which divisional lines may be drawn in
any established succession of rock-groups.

The two principal tests by which the relative age of different
strata is determined are (1), Superposition ; (2), Fossil contents.

The conclusions to be drawn from the superposition of strata are
explained in most text-books of physical geology, and the law of
vertical succession which forms the basis of the whole fabric of
historical geology may be stated as follows : " In any succession
of beds each one represents the conditions which prevailed over a
certain area for a certain length of time, the lowest is the oldest,
the uppermost is the newest, and the relative age of the others is
indicated by their relative position." If the strata are inclined, the
right order is ascertained by making a geological survey of the
district, and constructing a section at right angles to the general
strike of the beds.

Again, by tracing any one set of strata horizontally along their
strike from one part of a district to another, where perhaps there
are other rocks of a different kind, we obtain a datum of reference
by which to determine whether the rocks in the second area are
newer or older than those in the first.

So long as there is physical and geological continuity between
the different portions of a district, i.e. so long as some one member
of a conformable series of strata can be followed continuously, such
a survey generally affords sufficient data for ascertaining the relative
position of the rocks which occur in the district, and for constructing
a table of their vertical succession. But when either geographical
or geological continuity is interrupted that is, when a district or
country is separated from others of like structure either by the sea
or by tracts of totally different rocks then we must begin all over
again, and construct an independent table of strata for the new
district. For example, Wales is a district to all parts of which one
system of classification and nomenclature can be applied. Similar
groups of rocks occur in Ireland on the one hand, and in Cumberland
on the other ; but Wales is physically separated from Ireland by
the Irish Sea, and geologically separated from Cumberland by the



INTRODUCTION 3

Triassic plains of Cheshire and Lancashire ; hence the same system
of nomenclature could not be used in the other districts, the vertical
succession had to be determined independently, and local names
given to the different subdivisions in each district before they
could be in any way compared with one another.

But, it may be asked, when two such districts have been inde-
pendently investigated, how are we to correlate the two tables of
strata, and ascertain which rocks or rock-groups were approxi-
mately contemporaneous ? It is here that a knowledge of fossils
(Paleontology) comes to our aid, and enables us to identify rocks by
their fossil contents, so that strata in different districts and of
different lithological characters may be included in the same natural
group or system, because they contain the same or closely similar
species of fossils. This was the principle discovered and applied at
the beginning of this century by Dr. William Smith, who is often
called the Father of British Geology, and who was certainly the
founder of that branch of the science which is the subject of the
present volume.

The book in which Smith recorded his discovery of the strati-
graphical use of fossils was entitled Strata identified by Organised
Fossils, and was published in 1816. He had previously made
out the succession of the strata which occur near Bath, and had
observed that each well-marked group of beds contained a special
assemblage of fossils. As his acquaintance with English rocks be-
came larger he noticed that there was a similar succession elsewhere,
and thus (in the words of his nephew and biographer 1 ) "he inferred
that each of the separate periods occupied in the formation of the
strata was accompanied by a peculiar series of the forms of organic
life, that these forms characterised those periods, and that the differ-
ent strata could be identified in different localities and otherwise
doubtful cases by peculiar embedded organic remains."

The experience of subsequent observers confirmed and established
this inference, which has become a guiding principle in stratigraphical
geology. Further research, moreover, has brought out the more
definite conclusion that there has been a continuous succession of
life-forms, that species and genera and families, and even whole
orders of beings, have come into existence, have flourished, and have
then gradually died out, never to recur. It is this non-recurrence of
species which gives a special value to fossils as a test of age and as
a means of correlation. The same kind of rock has been formed
again and again during the history of the world, but when once a
species has died out it has never appeared again.

It must not be supposed, however, that the stratigraphical
1 Memoirs of William Smith, by John Phillips, F.R.S., 1844.



4 STRAJIGRAPHICAL GEOLOGY

succession of rocks presents us with a complete record of the
history of the earth, or that it will ever supply us with examples
of all the species which have lived upon the earth's surface. On
the contrary, the records preserved to us are very incomplete, and
many pages are wanting in every chapter of the great volume, so
that Stratigraphical Geology cannot be denned as a history of the
earth; it would be more correctly described as scenes from the
history of the earth.

The causes which have produced this "imperfection of the
record" will be indicated in the next chapter. The reader will
then be prepared to enter more fully into the principles on which
the long succession of formations has been divided into systems,
and the grounds on which these systems have been subdivided into
rock-groups of fairly equivalent value. Finally, a few words on
the distribution of species at the present day will explain some
limitations in the application of palaeontological evidence, and
prepare him for the distinction between synchronism and homotaxis
in correlating the rock-groups of different countries.

From the above remarks it will be obvious that some previous
knowledge of physical geology and of zoology is a necessary
preparation to the study of Stratigraphical Geology. The reader
may gain the first from any elementary manual of geology or from
the author's Handbook of Physical Geology (G. Bell and Sons) ; and
Woods's Elementary Palaeontology (Cambridge Univ. Press) will
furnish him with a good introduction to the palaeontology of the
Invertebrata.

For the purpose of convenient reference an outline of the general
classification of the animal kingdom is here appended, the
arrangement of the Invertebrate classes being substantially that
to be found in Zittel's Paleontology and in Woods's Elementary
Palaeontology, except that in the classification of the Echinoderma I
have followed Messrs. Bather and Gregory. The arrangement of
the Vertebrata is based on that given in A. S. Woodward's Outlines
of Vertebrate Palaeontology.



INTRODUCTION



Sub-kingdoms.
PROTOZOA

CCELENTERA .



ECHINODERMA .



WORMS "



MOLLUSCOIDEA



MOLLUSCA



ARTHROPODA .



Classes.


Orders found fossil.


"


/ Foraminifera.


Rhizopoda .


\Radiolaria.


Infusoria .
Sporozoa .


[-(No fossil forms).
iCalcarea.


Porifera


Hexactinellidae.




Demospongia.


Anthozoa or Actinozoa


Zoantharia.
Alcyonaria.


Hydrozoa .


( Hydrocorallinae.
-! Stromatoporoidea.
[Graptolitoidea.


'


/Protoblastoidea.


Blastoidea .


'\Eublastoidea.


Cystidea .


/Amphoridea.
\Rliombifera.


Edrioasteroidea.




< Crinoidea .


/Monocyclica.
' (Dicyclica.




( Asteroidea.


Stelleroidea


\ Ophiuroidea.


Echinoidea


/Regularia.
'\Irregularia.


Holothuroidea .


. Occasionally fossil.


{Platyhelmia
Nemerti


}No fossil forms.


Rotifera




Annelida .


. Chsetopoda.


Bryozoa
Brachiopoda


. Gymnolsemata.
/Inarticulata.
\Articulata.


Pelecypoda or
Lamellibranchi a


| Prionodesmacea.
\ Anomalodesmacea.
' ^Teleodesmacea.


Scaphopoda
Amphineura


. (Dentalium, etc.)
. Polyplacophora.


Gastropoda


fStreptoneura.
"\Euthyneura.


Cephalopoda


/Tetrabranchiata.
' \ Dibranchiata.




?Trilobita.




J Entomostraca.


Crustacea .


' | Malacostraca.




[Cirripedift,




/Merostomata.


Acerata


\Arachnida.


Myriapoda


. Rare as fossils.




Apt era.




Orthoptera.




Neuroptera.


Insecta


Hemiptera.
'j Coleoptera.




Diptera.




Lepidoptera.


,


Hymenoptera.



STRATIGRAPHICAL GEOLOGY



Sub-kingdoms. Classes.

CHORDATA . . Tunicata, etc
Agnatha .



Pisces



Amphibia ,



VERTEBRATA . . I



Reptilia



Aves



Mammalia



Orders found fossil.
. Few fossil forms.
t fMarsipobranchii.
' ^Ostracodermi.

fChimseroidei.

I Elasmobranchii.

^ Dipnoi.

iTeleostomi.

/Urodela.
. i Aiiura.
( Labyrinthodonta.

i'Chelonia.
Lacertilia.
Ophidia.
Crocodilia.
Plesiosauria.
' \Ichthyosauria.
JAiiomodontia.
fRliynchocephalia.
[Dinosauria
VPterosauria.

{Archfleornithes.
Odontornithes.
RatitfiB,
Carinatse.
TPrototheria.
Marsupialia.
Edentata.
Sirenia.
Cetacea.
Ungulata.
Rodentia.
Carnivora.
Insectivora.
Cheiroptera.
V Primates.



CHAPTEK II

ORIGIN AND SUCCESSION OF SPECIES

Origin of Species. At the outset of this inquiry we are met
by the question, What is a species ? Before the publication of
Darwin's book on the Origin of Species most people regarded
a species as the result of a special creation of a definite kind of
plant or animal, yet all who studied either plants or animals
were obliged to admit that some species displayed many varieties,
and also that it was difficult to say what amount of difference
should constitute a species.

Lamarck in 1801 was the first to propound the doctrine that
all existing species are descended from other species, but few
naturalists gave credence to his views, and it was not till 1859,
when Darwin published his book, that the world became familiar
with such a doctrine.

On the primary point of the appreciation of differences Darwin
remarks (Origin of Species, sixth edition, p. 41), " Certainly no
clear line of demarcation has yet been drawn between species
and sub-species that is, the forms which in the opinion of. some
naturalists come very near to, but do not quite arrive at, the
rank of species ; or again between sub-species and well-marked
varieties, or between lesser varieties and individual differences ;
and a series [of specimens] impresses the mind with the idea of
an actual passage." Further on he says, " From these remarks
it will be seen that I look at the term species as one arbitrarily
given, for the sake of convenience, to a set of individuals closely
resembling each other, and that it does essentially differ from the
term variety, which is given to less distinct and more fluctuating
forms."

Darwin and Wallace developed their views about the same
time, and both accounted for the existence of so many varieties,
species, and genera of organisms by indicating the various causes
and conditions which influence all kinds of organisms and tend to

7



8 STRATIGRAPHICAL GEOLOGY

modify their habits, forms, and members. They have shown how
the constant struggle for existence and the frequent changes of
environment may have developed or have increased a tendency
to variation, and how this variation results in the formation of
varieties and species. Natural selection (or the selective action
of natural processes) results also in the extinction of many forms
and in the survival of a few namely, of those few which are the
most capable of accommodating themselves to the more rigorous
and changed conditions of existence. This is called the " survival
of the fittest." It is by the infinite repetition of these processes
that species which are now widely different may have been evolved
from a common ancestor.

Another consequence of natural selection is the preservation of
those varieties and species which chance to possess peculiarities
that are useful to them in the struggle for existence. Thus as
Darwin says (op. cit. p. 103), "it leads to the improvement of each
creature in relation to its organic and inorganic conditions of life,
and consequently in most cases to what must be regarded as an
advance in organisation." In other words, it leads to the evolution
of higher and higher forms of life.

Now if the descendants of varieties may become different
species, and if the descendants of different species may in course
of time become so differentiated that most naturalists would rank



Online LibraryAlfred John Jukes-BrowneThe student's handbook of stratigraphical geology → online text (page 1 of 52)