DEPARTMENT OF THE INTERIOR

HUBERT WORK, Secretary

UNITED STATES GEOLOGICAL SURVEY

GEORGE OTIS SMITH, Director

Bulletin 769

THE GEOLOGIC TIME CLASSIFICATION OF THE UNITED 

STATES GEOLOGICAL SURVEY COMPARED WITH

OTHEB CLASSIFICATIONS

ACCOMPANIED BY

THE ORIGINAL DEFINITIONS OF ERA, PERIOD 

AND EPOCH TERMS

A COMPILATION 

BY

M. GRACE WILMARTH

 a « » 

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WASHINGTON

GOVERNMENT PRINTING OFFICE

1925
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CONTENTS

Page

Preface, by T. W. Stanton_______ _ ._______ v

Introduction ________________________ . 1

Purpose of the work______ ____________________ 1

Scope of the work__________ _________________ 1

Builders of the time table_________________________ 2

Time terms and rock terms_ _________________ 8

Length of the time divisions __ .____ ________ 4

Thickness of the sedimentary rocks_________ ______ 6

Breaks in the geologic record __, __ ___ 7

Acknowledgments____________________________ 7

Use of quotation marks____ __ __ _____ 8

The era terms______ ___ __--_____ ________ 8

Cenozoic era_ _ _ _ _______ _ 8

" Psychozoic era "_____ _____ __________ _ 9

Mesozoic era _ 9

Paleozoic era_____ _ ____ ______ 10

Pre-Cambrian era terms 14

"Agnotozoic era " _ 14

"Archeozoic era "_ __ _ ,_________ 17

"Azoic era "______ ___ _________ 20

" Collozoic age "______ _ _ _ ________ 26

" Eobiotic era " and " Eomorphic era " _________ _ 27

" Eozoic era " __ _ ________ 27

" Hypozoic era "_________ __ _________ 80

" Progonozoic " and "Progonic" _ _____ 30

Proterozoic era _ __ _ 31

" Protozoic era "__ _ _ _____ 42

" Prozoic era "_____________________________ 43

The period and epoch terms _ 43

Quaternary period (or system) _ 43

Recent epoch (or series) 46

Pleistocene epoch (or series) '. _ 47

Tertiary period (or system). _ 49

Pliocene epoch (or series) . 51

Miocene epoch (or series) ___ _ 53

Oligocene epoch (or series) __ 53

Eocene epoch (or series)_ _ __ 54

'^Paleocene " 54

Cretaceous period (or system) 56

Gulf epoch (or series) ' 59

Comanche epoch (or series) ; 59

Shasta epoch (or series) 61

Jurassic period (or system) 62

Triassic period (or system) 64

in
TV CONTENTS

The period and epoch terms Continued. Page

Carboniferous period (or system) . 65

Permian epoch (or series) _ 70

Pennsylvanian epoch (or series)__ ____ 72

Mississippian epoch (or series) 73

"Tennessean system"- _ 74

" Waverlyan system " ____ _ 75

"Anthracolithic " ____________ ________________- 78

Devonian period (or system)____________ _ 78

Silurian period (or system)___ __ . 80

" Ontario system "__.__________________ 81

"Alexandrian series " __ 82

Ordovician period (or system) 83

Cincinnatian epoch (or series)_ ______ _ 85

Mohawkian epoch (or series) 86

"Canadian period (or system)" 87

" Champlainic system "____ _ _______ 88

Proposed Ozarkian system of E. O. Ulrich 89

Cambrian period (or system) _ 92 

"Saratogan" epoch (or series) (discarded name for Upper

Cambrian) -____ __ ____ _____ 96

St. Croixan epoch (or series) (Upper Cambrian)________ 97

Acadian epoch (or series) (Middle Cambrian)__________ 98 

"Georgian" epoch (or series) (discarded name for Lower

Cambrian) __________ ______________________ 100

Waucoban epoch (or series) (Lower Cambrian)_________ 100

" Taconic system "_____ __ __ _______ 101

Algonkian period (or system) 103

Keweenawan epoch (or series) __ _ _____ ____ 104

Huronian epoch (or series) 105

Other provincial series terms____________________ 108

Belt series _____ _______________ 108

Glenarm series 112

Grand Canyon series___________ ___________ 113

Grenville series__ ____ 114

Llano series _____ 120

" Killarney revolution " ______ 121

" Algoman revolution " _ ________ 123

" Timiskamian series "_________________________ 124

" Sudburian "______________________________ 125

Archean period (or system) _ _____________ 127

Laurentian epoch (or series)___ ________________ 127

Keewatin epoch (or series)_____________________ 128

" Coutchiching series "_______________________ 132

" Loganlan " ___--____________________________ 135

Index. , __________ 137

ILLUSTRATION

Geologic time classification of United States Geological Survey compared 

with other classifications________________________ In pocket
PREFACE

By T. W. STANTON

With the intensive study of the geology of a country as large as 

the United States the stratigraphic classification has necessarily become very complex and the number of formation names has been 

greatly multiplied. However much this complexity and multiplicity 

may be deplored, it is the inevitable result of detailed study and especially of detailed mapping in disconnected regions. Further, as 

the geologic history and development of different areas have differed, 

so must the stratigraphic units recognized and their grouping differ.

In recent years the increased emphasis given by many geologists 

to the results of diastrophism of the movements of the earth's 

crust as the basis of classification has caused the proposal of several major changes in classification, both by interpolating new systems or periods and by changing the boundaries of those already 

recognized, but the geologists who have proposed innovations have 

differed among themselves, so that several American classifications 

are now current, all of which depart to a greater or less extent from 

that used in the publications of the United States Geological Survey. That the Geological Survey has been conservative, perhaps 

overconservative, in its classification is shown by the fact that it 

still uses essentially the same scheme that it adopted for the Geologic Atlas of the United States, as printed in the Twenty-fourth 

Annual Report of the Director in 1903. The classifications current in Europe also differ somewhat from one another and from those 

current in America.

With the rapid progress of detailed geologic investigation throughout the world and the shift in viewpoint as one phase or another 

of the complex subject is emphasized, changes in classification must 

necessarily be made as rapidly as enough evidence is presented to 

convince the majority of geologists that they are desirable.

In the accompanying chart (compiled by Miss M. Grace Wilmarth, secretary of the committee on geologic names) the United 

States Geological Survey's classification is compared'with the classifications of Chamberlin and Salisbury, Ulrich, Schuchert, Clarke,
VI PREFACE

and Grabau for the United States and of De Lapparent, Haug, 

and Geikie for Europe. The accompanying text quotes the original 

definitions of the major terms and gives brief statements showing 

the changes they have undergone, which, taken in connection with 

the correlation chart, give a fair general idea of the history of each 

term. The bulletin includes also a table showing several modern 

estimates of the measure of time included in the several geologic 

periods and epochs. It is believed that the material thus assembled 

in compact form will be useful to professional geologists, to students of geology, and possibly to that larger circle of readers who 

have an intelligent interest in general geology.

This chart will not fully meet the demand for correlation tables 

showing the relations of all the many hundreds of geologic formations in the United States that have been described and named, 

but when it 'is supplemented by a stratigraphic lexicon, which Miss 

Wilmarth now has in preparation, most of the information desired will be ayailable in more useful and more accurate form than 

could be given in detailed correlation tables except those for restricted areas, which may be prepared from time to time.
THE GEOLOGIC TIME CLASSIFICATION OF THE UNITED 

STATES GEOLOGICAL SURYEY COMPARED WITH OTHER 

CLASSIFICATIONS AND ACCOMPANIED BY THE ORIGINAL DEFINITIONS OF ERA, PERIOD, AND EPOCH TERMS

By M. GRACE WILMARTH

INTRODUCTION

Purpose of the work. The United States Geological Survey receives many requests for its time classification, for information as to 

the relations of its time classification to those of other geologic 

authorities, and for the definitions of its time terms and of certain 

European time terms. The Survey has never published a comprehensive list of definitions of the time terms, nor any table or text 

explaining wherein its time classification differs from other time 

classifications. To supply the demand represented by these requests 

this bulletin is published.

Scope of the* work. In assembling the definitions of the time terms 

it became apparent that the original definitions should be published, 

in order that the reader might determine for himself wherein they 

differ from or agree with those that have grown out of studies made 

during more than a century and a half. The original definitions are 

quoted literally, except that those in foreign languages have been 

translated. In these definitions footnotes that have been inserted by 

the compiler are inclosed in brackets; other footnotes are part of the 

matter quoted. For practical reasons all footnotes, whether quoted 

or not, are numbered consecutively throughout the bulletin.

Most of the original definitions are founded on the geology of 

Europe, and in order that the reader may understand the relation 

of the Survey's time classification to that employed in Europe, the 

European classification, as interpreted by three European geologists, 

De Lapparent, Haug, and Geikie, has been incorporated in the accompanying chart, for comparison with that of the United States 

Geological Survey.

In recent years several American geologists and paleontologists 

have proposed important changes in the current time classification 

by introducing new periods and by changing the boundaries of old 

ones. The changes advocated by some of these geologists are also 

shown in the chart.

1
2 GEOLOGIC TIME CLASSIFICATION

Builders of the tim& taW&. The first time classification was that 

of Arduino, an eminent Italian scientist, who in 1760 divided the 

rocks of the earth into three major divisions, which he called Primitive (the oldest), Secondary, and Tertiary (the youngest). In this 

classification the more recent surficial deposits of the earth, to which 

the name Quaternary is now applied, were ignored. Of these 

earliest time terms " Primitive " (also called " Primary ") and " Secondary " have long since fallen into disuse, but Tertiary is still in 

general use. The perpetuation of the term is a fitting tribute to a 

distinguished pioneer in geology as well as other sciences. Similarly, 

Quaternary remains, a relic of an early modification of Arduino's 

classification, by Desnoyers (1829) and Keboul (1833).

The names of some of the distinguished men who followed Arduino 

and helped to establish the geologic time classification now generally 

recognized in Europe and America are given in the following list:

Cenozoic era: Phillips (England), 1840 and 1841.

Quaternary period: Desnoyers (France), 1829; Eeboul (France), 1833. 

Recent epoch: Lyell (England), 1833.

= "Modern Group" of De la Beche (England), 1831. 

Pleistocene epoch: Lyell (England), 1889; Forbes (England), 1846. 

= "Erratic Block Group" of De la Beche (England), 1831. 

= "Diluvium" of Buckland (England), 1823. 

Tertiary period: Arduino (Italy), 1760.

= "Newest Floetz" of Werner (Germany), 1787-1817. 

Pliocene epoch: Lyell (England), 1833. (As originally defined included Pleistocene.)

Miocene epoch: Lyell (England), 1833. 

Oligocene epoch: Beyrich (Germany), 1854. 

Eocene epoch: Lyell (England), 1833. (As originally defined included

Oligocene.) 

Mesozoic era: Phillips (England), 1840 and 1841.

= "Secondary" of Arduino (Italy), 1760. 

Cretaceous period: Omalius d'Halloy (Belgium), 1822. 

Gulf epoch: R. T. Hill (United States), 1887. 

Comanche epoch: R. T. Hill (United States), 1887. Shasta epoch:

Gabb (United States), 1869.

Jurassic period: A. von Humboldt (Germany), 1799; Wm. Smith (England), 1815 and 1817; Conybeare and Phillips (England), 1822. 

Triassic period: Albert! (Germany), 1834. 

Paleozoic era: Sedgwick (England), 1838. Included in "Primary" of Arduino

(Italy), 1760.

Carboniferous period: Conybeare and Phillips (England), 1822. (As originally defined included Devonian and excluded Permian.) 

Permian epoch: Murchison (England), 1841. 

Pennsylvanian epoch: H. S. Williams (United States), 1891.

= "Coal Measures" of Conybeare (England), 1822. 

Mississippian epoch: A, Winchell (United States), 1869, and H. S.

Williams (United States), 1891.

= "Carboniferous limestone" of Conybeare (England), 1822. 

Devonian period: Sedgwick and Murchison (England), 1839.

= "Old Red sandstone" of Conybeare (England), 1822.
INTRODUCTION 3

Silurian period: Murchison (England), 1835. (As originally defined included all of Ordovician except the Beekmantown.) 

Ordovician period: Lap worth (England), 1879.

Cincinnatian epoch: Meek and Worthen (United States), 1865; N. H.

Winchell and E. 0. Ulrich (United States), 1897. 

Mohawkian epoch: Clarke and Schuchert (United States), 1899. 

Cambrian period: Sedgwick (England), 1835. (As originally defined included the basal part of the Ordovician, or the rocks now known as 

Beekmantown, and some Archean rocks.) 

Upper Cambrian epoch: Sedgwick (England), 1835. 

= "Saratogan" of Walcott (United States), 1903. 

= St. Croixan of Walcott, 1912, which replaces " Saratogan"

(inappropriate name). 

Middle Cambrian epoch: Sedgwick (England), 1835.

= Acadian of Dawson (Canada), 1868. 

Lower Cambrian epoch: Sedgwick (England), 1835. 

= "Georgian" of Walcott (United States), 1903. 

= Waucoban of Walcott, 1912, which replaces " Georgian" (inappropriate name). 

Proterozoic era: Emmons (United States), 1888, and Van Hlse (United States),

1908. Included in "Primary" of Arduino (Italy), 1760. 

= "Protozoic era," Sedgwick (England), 1838. 

Algonkian period: Powell (United States), 1890; used but not defined by

Walcott in 1889.

Keweenawan epoch: T. B. Brooks (United States), 1876. 

Huronian epoch: Logan (Canada) and Hunt (United States), 1855. 

Archean period: Dana (United States), 1872. (As originally defined included Algonkian.)

Laurentian epoch: Logan (Canada), 1854." 

Keewatin epoch: Lawson (Canada), 1885.

Time terms and rock terms. As shown in the accompanying chart, 

the geological eras of the earth's history are divided into smaller 

time units, generally called periods, and the periods are divided into 

still smaller time units called epochs. In the nomenclature adopted 

by the Geological Survey the rocks formed during a geologic period 

constitute a geologic system, and the rocks formed during a geologic 

epoch constitute a series. Or the explanation may be reversed, and 

we may say that the time covered by a geologic system constitutes a 

geologic period, and the time covered by a geologic series constitutes 

a geologic epoch. This technical usage of the terms period, system, 

series, and epoch is not, however, universal, as the headings in the 

chart will reveal. The rock element, and not the time element, appears to have been dominant in the minds of most of the geologists 

who defined the terms, for most of the subdivisions are defined as 

rock units rather than as time units. It is, therefore, the rocks themselves that are described in most of the definitions, rather than the 

time during which the rocks were formed. The rock idea and the 

time idea are, however, so interwoven that any description of a time 

unit almost automatically resolves itself into a description of the

1146 25 2
4 GEOLOGIC TIME CLASSIFICATION

rocks of the interval. To this fact is due the seeming mixture of the 

two ideas in the quotations that follow.

For purposes of mapping and stratigraphy the series are divided 

into smaller units called formations, and many formations are divided into members and lentils. Several formations may also be 

assembled into a group. It might be useful to have a separate time 

term corresponding to each of these rock units, but no such terms have 

yet been adopted, and in Geological Survey publications the single 

term epoch is used for all subdivisions of periods, whether they correspond to series, groups, formations, or members.

The chart also shows that the epochs (or series) into which some 

of the periods (or systems) are divided have been given geographic 

names, while the epochs of other periods (or systems), equally important, are designated simply Upper, Middle, and Lower. The 

latter terms, however, have served to indicate quite as definitely the 

epochs of geologic history, which are based chiefly on changes in life 

as indicated by fossils, but in part on the character of the rocks and 

their relations to preceding and succeeding beds.

Length of the time divisions. The age of the earth is an unsolved 

problem. Many geologists and physicists have, from time to time, 

worked on this problem, especially on estimates of the time represented in the geologic record since the earth attained approximately 

its present condition. Among them are such well-known European 

scientists as Lyell, Croll, Darwin, Sir William Thomson (Lord 

Kelvin), Tait, Geikie, Huxley, Harker, Mellard Reade, A. Holmes, 

Joly, Goodchild, Sollas, and Penck. Among American geologists 

who have contributed to the subject may be mentioned Clarence 

King, T. C. Chamberlin, R. D. Salisbury, W J McGee, J. M. 

Clarke, H. S. Williams, J. D. Dana, W. D. Matthew, G. K. Gilbert, 

G. F. Becker, C. D. Walcott, Charles Schuchert, F. W. Clarke, and 

Joseph Barrell. The problem has been attacked from different 

angles, and as the methods employed all involve unknown and imperfectly known elements they must give widely varying results. 

The calculations have been based on the rate of development of life 

on the earth throughout the ages, on the quantity of salt in the 

seas, on earth temperatures, on the rate of deposition of sediments 

of various kinds adjusted to the maximum known thicknesses of 

such sediments on the earth, on the rate of denudation or wearing 

away of the land, and on the heat delivered by the sun. More recent 

calculations have been based on radioactivity that is, on estimates 

of the length of time required to produce given proportions of certain elements through the disintegration of the more complex elements uranium and thorium.

For purposes of comparison the estimates of Williams (1893), 

Sollas (1909), Schuchert (1910). and Matthew (1914), all of which
INTRODUCTION

are calculated on other bases than radioactivity, have been considered together, and the minimum and maximum mentioned by any 

one of them is given in the second column of the following table, 

which is adapted from a tabular statement published by Barrell in 

1917. In the third column of the table the estimates made by 

Goodchild in 1896 are given. Goodchild's estimates, like some of the 

others, are based on a detailed study of the stratigraphic sequence 

of the rocks, but his results differ widely from the estimates of others 

on a similar basis and approach closely the figures derived by 

Barrell from the study of radioactivity. Barrell's figures are given 

in the fourth column of the table. The table shows that these 

modern estimates of the age of the earth since the geologic record 

began range from 48,380,000 years to 1,710,000,000 years. The estimates based on radioactivity have been considered by many 

scientists excessive, but recently published opinions x express the belief that readjustments and recalculations of the estimates based on 

geology, biology, and astronomy will greatly increase the figures 

heretofore obtained on those bases, and will tend to bring those results more into harmony with the results based on radioactivity.

Estimates of geologic time, in years 

[Adapted from Joseph Barrell (Oeol. Soc. America Bull., vol. 28, pp. 884-885,1917)]

Time divisions

Upper Cretaceous epoch.... 

Lower Cretaceous or CoFigures obtained by methods other 

than radioactivity

Composite of Williams 

(1893), Schuchert 

(1910), Sollas (1909), 

and Matthew (1914)

2,100,000-10,800,000 

100,000- 1,000,000 

2, 000, 000- 9, 800, 000 

500,000- 1,300,000 

500,000- 3,000,000' 

500, 000- 2, 000, 000 

500, 000- 3, 500, 000 

6, 300, 000- 9, 950, 000 

3, 800, 000- 4, 700, 000 

2, 000, 000- 2, 700, 000

1,800,000- 2,000,000\ 

800,000- 3,000,000/ 

1,700,000- 2,250,000 

12, 480, 000-45, 860, 000 

4, 700, 000- 6, 860, 000 

1, 200, 000- 2, 000, 000 

1, 500, 000- 2, 160, 000 

2, 000, 000- 2, 700, 000 

1, 980, 000- 5, 000, 000 

1, 500, 000- 4, 000, 000 

1,700,000-15,000,000 

2, 600, 000-15, 000, 000

20, 880, 000-66, 610, 000 

27,500,000 (Walcott) 

17,500,000 (Walcott) 

10, 000, 000? (Walcott)

48, 380, 000-94, 110, 000

Goodchild 

(1896)

93,400,000 

16, 000, 000

77,400,000 

191, 500, 000

31, 400, 000

72, 600, 000

87,500,000 

419,300,000 

139, 300, 000 

45, 000, 000 

31,800,000 

62, 500, 000 

125, 000, 000 

56, 000, 000 

57,000,000 

42, 000, 000

704, 200, 000

Figures obtained by Barrell 

on radioactivity

55,000,000- 65,000,000 

1,000,000- 1,500,000 

54, 000, 000- 63, 500, 000 

6,000,000- 7,500,000 

12,000,000- 14,000,000 

16, 000, 000 

20,000,000- 26,000,000 

135,000,000-175,000,000 

65,000,000-85,000,000 

40, 000, 000- -50, 000, 000

25,000,000- 35,000,000 

35,000,000-45,000,000 

' 35,000,000- 45,000,000 

350,000,000-470,000,000 

100,000,000-140,000,000 

25,000,000-40,000,000 

35, 000, 000- 50, 000, 000 

40, 000, 000- 50, 000, 000 

50,000,000 

40, 000, 000 

90,000,000-130,000,000 

70,000,000-110,000,000

540,000,000-710,000,000 

700, 000, 000-1, 000, 000, 000

1, 240, 000, 000-1, 710, 000, 000

1 Chamberlin, T. C., Clarke, J. M., and Brown, B. W., in a symposium on the age of the 

earth: Am. Phllos. Soc. Proc., vol. 61, No. 4, pp. 247-28-3, 1922.
6 GEOLOGIC TIME CLASSIFICATION

Thickness of the sedimentary rocks. As- an example of the kind 

of data used in estimates of geologic time the thickness of the sedimentary rocks may be considered. This thickness, to be sure, varies 

from place to place, for nowhere is there a complete section with all ' 

the geologic systems in complete development. Not only does the 

thickness of each system vary greatly, even within small areas, but ) 

in most places some of the systems are unrepresented. In addition, 

where the rocks of some systems are thickest the rocks of others are ^ 

thinnest or absent, having either been deposited and afterward 

eroded away, or never deposited because the region at the1 time stood 

above the sea. In order to estimate the length of time required to 

form the sediments the scientist must consider the sum of the maximum known thicknesses of the various kinds of rocks deposited during each period, he must determine the average rate at which each 

kind of rock is deposited, and he must make allowances for erosion 

and for great time gaps. The following table showing the maximum 

known thicknesses of the sedimentary rocks of the earth is compiled 

from the estimates of several European and American geologists, 

supplemented for some units by more recently published sections:

Maximum knoim thicknesses of existing sedimentary rocks of the earth

Feet 

Cenozoic_______________-___________ 70,300

Quaternary system 4,000 - 

Tertiary system ___ ___ ______ _ __ 66,300 

Pliocene series (California)______ _ 10,500- 

Miocene series (California)___________ 20,800 

Oligocene series (12,000 feet in Italy; 10,000

feet in California)_______________ 12,000 

Eocene series (23,000 feet in Wyoming, including 

the "Paleocene" rocks, which have an, aggregate thickness of about 10,000 feet; 20,000 feet , \ 

in Oregon) ___ ______ 23,000

Mesozoic __________________ 74,900

Cretaceous system 46,400

Upper Cretaceous series (Wyoming) 20,400

Lower Cretaceous series (California) 26,000

Jurassic system (Alaska) 15,000

Triassic system (Alps, Nevada, British Columbia) 13,500

Paleozoic______ 161, 500

Carboniferous system 52,500 tPermian series (Australia) 13,000

Pennsylvanian series (Oklahoma) 24,500

Mississippian series (Britain) 15,000

Devonian system (Britain) 37,000

Silurian system (Scotland) 15,000

Ordovician system (Britain) 17,000

Cambrian system (British Columbia) 40,000
INTRODUCTION 7

Feet

Pro.terozoic ___________________________ ( ?) 

Algonkian system (Superior region, 82,000 feet sediments, 22,000 feet volcanic rocks) ________ 82,000 

Keweenawan series _ __ __ __ 50,000 

Huronian series ___________________ 32, 000 

Archean system. Purely conjectural. Few sediments. 

Has been estimated at- __ __ ___________ 94,000

Breaks in the geologic record. Many time breaks occur in the 

geologic record, which is like a book in which leaves and even chapters are missing here and there. These time breaks mark boundaries 

between eras, between periods, and between epochs of both long and 

short duration. Some of them are of great magnitude and cover 

enormous periods of time, when the rocks that had already been 

formed were raised above the sea and subjected to the destructive 

action of the elements. Some of them are of smaller magnitude, and 

still others represent only minor oscillations of the sea. It is not 

always easy to determine the value of a particular time break. A 

break that is considered by one geologist of such magnitude as to 

form an appropriate boundary between periods or systems may seem 

to another equally competent geologist to be of minor importance. 

Hence the discrepancies shown in the classifications given on the 

chart.

Acknowledgnients. Most of the books cited in this bulletin are in 

the library of the Geological Survey. Two were loaned to the Survey 

by the Library of Congress, namely, Annales des sciences naturelles, 

volume 16, 1829, and Bulletins de la Societe" vaudoise des sciences 

naturelles, volume 4, 1856. The books mentioned in the following 

list are very rare, and no copies of them are known to be in the 

libraries of Washington, but copies were generously loaned to the 

Survey as follows-:

John Crerar Library, Chicago, 111. : 

[\ Penny Cyclopaedia, vol. 17, 1840.

TJeber die Stellung der hessischen Tertiar-bildungen : K. preuss. Akad.

Wis. Berlin Monatsber., November, 1854.

Library of the Museum of Comparative Zoology at Harvard College : 

Ge"ologie de la pgriode quaternaire, by Heuri Reboul, Paris, 1833. 

Yale University Library:

» French translation of Charles Lyell's Elements of geology, Paris, 1839, 

, containing an appendix not in the original English edition. 

Dr. George P. Merrill, Washington, D. C. :

Geological essays, by Richard Kirwan, 1779.

The compiler is indebted to members of the United States Geological Survey for most of the translations and for valuable suggestions 

T and criticism.

f

J

/
8 GEOLOGIC TIME CLASSIFICATION

Use of quotation marks. The terms printed with quotation marks 

in this compilation have not been adopted by the United States Geological Survey.

THE ERA TERMS

CENOZOIC ERA 

J. Phillips, 184O (Penny Cyclopaedia, vol. 17, pp. 153-154).

Supposing, as we think likely, that general terms for stratified rocks, thus 

formed upon a consideration of their organic contents, which appear to follow 

a great law of succession, will be .preferred to others based on a view of 

their mineral qualities, which are certainly subject to repetition, there will 

be no other difficulty in their construction or application than what may be 

overcome by the progress of investigation. As many systems or combinations 

of organic forms as are clearly traceable in the stratified crust of the globe, 

so many corresponding terms (as Palaeozoic, Mesozoic, Kainozoic [Cenozoic], 

&c.) may be made, nor will these necessarily require change upon every new 

discovery. For instance, the term Palaeozoic may be retained, though it 

should be found that the application of it ought to be extended so as to include the carboniferous rocks or even the magnesian limestone (" Zechstein " 

of Germany). This indeed is not unlikely, for the following reasons. * * *

J. Phillips, 1841 (Palaeozoic fossils of Cornwall, Devon, and West Somerset: 

Great Britain. Geol. Survey Mem., p. 160).

[See under Paleozoic era, J. PMllips, 1841]

It is probable that the terms " Kainozoic" and " Cainozoic'" 

(Cenozoic) as introduced by Phillips in 1840 and 1841 included the 

"Newer Pliocene" of Lyell, although Lyell in 1839 replaced that 

term by Pleistocene and restricted Pliocene to his " Older Pliocene." 

The United States Geological Survey includes the Recent and Pleistocene in the Cenozoic era, but, as shown on the accompanying chart, 

some authorities exclude from it the Recent, and still others exclude both Recent and Pleistocene. The meaning of the word is 

recent life.

The Cenozoic era contains more loose and uncompacted rocks 

than the other geologic eras. Its fossils, which are animals and 

plants of modern types, as a rule differ from those of the preceding 

Mesozoic era, although some Mesozoic forms persist even to the 

present time. The Quaternary period of the Cenozoic era has been 

believed to mark the advent of man on the earth, and it is therefore 

popularly known as the "age of man." Although mammals made 

their first appearance early in the Mesozoic era they reached their 

maximum development, in numbers and in size, during the Eocene 

epoch of the Tertiary period. The Tertiary is therefore popularly 

known as the " age of mammals."

\
^n 

j 

'

THE ERA TEEMS 9

"PSYCHOZOIC ERA" 

J. Le Conte, 1877 (Am. Jour. Set., 3d ser., vol. 14, p. 114).

III. Historic value of the Present time. Most geologists regard the Present 

as one of the minor subdivisions of the Cenozoic Era, or even of the Quaternary 

period. More commonly the Quaternary and Present are united as one age 

the age of man of the Cenozoic Era. The Cenozoic is thus divided into two 

ages ; the age of mammals commencing with the Tertiary and the age of man 

commencing with the Quaternary; and the Quaternary subdivided into several 

epochs, the last of which is the Present or Recent. But if the views above 

expressed in regard to critical periods, be correct, then the Present ought not to 

be connected with the Quaternary as one age, nor even with the Cenozoic as 

one era, but is itself justly entitled to rank as one of the primary divisions of ' 

time, as one of the great eras separated like all the other eras by a critical 

period ; less distinct it may be, at least as yet, in species than the others, the 

inaugurating change less profound, the interval less long, but dignified by the 

appearance of man as the dominant agent of change, and therefore well entitled to the name Psychogoic sometimes given it. The geological importance 

of the appearance of man is^not due only or chiefly to his transcendent dignity, 

but to his importance as an agent which has already very greatly, and must 

hereafter still more profoundly modify the whole fauna and flora of the earth. 

It is true that man first appeared in the Quaternary ; but he had not yet established his supremacy; he was still fighting for mastery. With the establishment of his supremacy the reign of man commenced. An age is properly characterized by the culmination, not the first appearance, of a dominant class. As 

fishes existed before the age of fishes, reptiles before the age of reptiles, and 

mammals before the age of mammals, so man also appeared before the age 

of man.

We, therefore, regard the Cenozoic and Psychozoic as two consecutive eras, 

and the Quaternary as the critical, revolutionary or transitional period between. But since the record of this last critical period is hot lost and we must 

place it somewhere, it seems best to place it with the Cenozoic Era and the 

mammalian age, and to commence the Psychozoic Era and age of man with the 

completed supremacy of man, i. e. with the Present epoch.

The interval covered by the term " Psychozoic era " is treated by 

the United States Geological Survey as >a part of the Genozoic era.

MESOZOIC ERA

J. Phillips, 1840 (Penny Cyclopiedla, vol. 17, pp. 153-154).

[See quotation under Cenozoto era]

J. Phillips, 1841 (Palaeozoic fossils of Cornwall, Devon, and "West Somerset t 

Great Britain Geol. Survey Mem., p. 16O).

[See quotation under Paleozoic era]

As originally defined in the foregoing publications the Mesbzoic 

era included the Cretaceous, "Oolitic" (later renamed Jurassic), 

and " New Red sandstone "- (later replaced by Triassic and in part 

by Permian). In the same year that Mesozoic was thus defined by 

Phillips (1841) Murchison introduced the term Permian to include 

the lower " New Red sandstone " and £he " Magnesian limestone "
10 GEOLOGIC TIME CLASSIFICATION

*

(the latter included in the Paleozoic by Phillips), and assigned the 

Permian to the Paleozoic era. This restricted the term Triassic to the 

upper part of the " New Ked sandstone " and abbreviated Phillips's 

definition of Mesozoic by the exclusion of the lower part of the 

" New Ked sandstone." This is the commonly accepted definition 

of the term to-day, but, as shown in the accompanying chart, there 

is some disagreement among geologists as to just where the Mesozoic 

should end and the Cenozoic begin. -^ 

The meaning of Mesozoic is middle life. The time covered by it \r 

marks the rise and culmination of shellfish with complexly cham- N 

bered coiled shells, called ammonites, of huge land reptiles called ^ 

dinosaurs, and of great swimming and flying reptiles. For this 

reason it is commonly known as the " age of reptiles." It also 

marks the first appearance of birds (in the Jurassic) and of mammals, and the great development of cycads, an order of palmlike 

plants (in the Triassic), and of angiospermous plants, to which belong palms and hardwood trees (in the Cretaceous). Mesozoic fossils differ greatly from those of the preceding Paleozoic era and the r 

succeeding Cenozoic era, although some forms of life are common 

to all three eras. (l

PALEOZOIC EBA / 

Rev. A. Sedgwick, 1838 (Geol. Soc. London Proc., vol. 2, Jio. 58, pp. 684 685).

Class II., or Palcsozoic series

This class includes all the groups of formations between Class I [see p. 25] 

and the old red sandstone; and is subdivided as follows: 

1. Lower Cambrian System. All the Welsh series under the Bala limestone. 

The two great groups of green roofing slate and porphyry on the north and

south side of -the mineral axis of the Cumbrian mountains. A small part of 

the slates of Cornwall and South Devon? A part of the slate series of the Isle 

of Man, etc., etc.

2. Upper Cambrian System. A large part of the Lammermuir chain on 

the south frontier of Scotland. A part of the third Cumbrian group, commencing with the calcareous slates of Coniston and Windermere. The system of 

the Berwyns and South Wales. The slates of Charwood forest? All the North 

Devon and a part of the South Devon series. The greater part of the Cornish 

series.

3. The Silurian System. The upper part of the third Cumbrian group, chiefly 

expended in Westmoreland and Yorkshire. The flagstone series of Denbigh 

shire. The hills on both sides of Llangollen. The region east of the Berwyn 

chain. The regions described in the papers of Mr. Murchison, from which 

the types of the system are derived. The lowest part of the culmiferous 

series?

Over all the preceding comes the Old Red Sandstone divided into three 

great natural groups in the country bordering the Silurian types of Mr. Murchison; in the northern counties developed in a less distinct manner, chiefly in 

the form of great unconformable masses of conglomerate, appearing at irregular intervals between the preceding groups and the carboniferous series.

\,
THE ERA TEEMS 11

Little notice is taken in the memoir of the crystalline unstratified rocks 

associated with the several series. Any questions of classification, bearing on 

their geological epoch, can only be determined by the effects, produced by them 

on the stratified series, which mark the period of their first protrusion; but 

for the present this subject is not touched on by the author.

J. Phillips, 184O (Penny Cyclopaedia, vol. 17, pp. 153-154).

PALEOZOIC SERIES. The fossiliferous strata of earlier geological date than 

the carboniferous system, and the mountain limestone, are thus designated 

in the article ORGANIC REMAINS. One of the greatest impediments to a clear 

exposition of geological truths, is the difficulty of choosing proper general 

terms to suit classifications founded on limited researches. The ancient terms 

of Primary, Secondary, and Tertiary Rocks will probably retain their popularity and applicability, because of the simplicity of the truly general idea 

which they contain in common the sequence of geological time. In characterizing and naming the subdivisions of these great groups of rocks, geologists 

have only partially followed out the same principle; every geological investigation of sufficient extent includes, as a principal point, the discovery 

of the relative antiquity of the subdivisions of Primary, Secondary, and 

Tertiary strata, but there is seldom an opportunity to frame a corresponding 

nomenclature, owing to the circumstance that general names, already and indeed 

long since proposed and adopted by the great body of geologists, cannot .without 

great inconvenience be changed, even when new discoveries or wider generalizations demand their correction.

The term " Transition " was applied to a large section of the Primary rocks, 

or else used to designate them as a separate class, at a time when true characters, could by no means be assigned to them. Among Transition rocks, 

" Grauwacke " was frequently seen. Hence the term Grauwacke System was 

commonly used to express a large portion (the upper) of the Primary series 

of strata.

In progress of rigorous investigation, the absence of organic fossils from 

the gneiss and mica-schist rocks, and the occasional or ordinary presence of 

them in the grauwacke series, became generally admitted, and hence the convenient classification of Mr. De la Beche of " Fossiliferous" and " Nonfossiliferous" Primaries, the former being in fact an equivalent term for 

"Transition Strata." Recent researches into the organization of the fossil 

plants and animals of those antient strata have produced very strong evidence 

for believing that, from the Snowdonian Slates, placed by Professor Sedgwick 

in the lower part of the Cambrian system, to the lower beds of the old redsandstone (at least), one system of organic life prevails characterised by the 

preponderance of corals, such as Catenipora and Favosites, shells of Brachiopoda and Cephalopoda, and Crustacea of the trilobitic types. It is true that 

when separate strata, included within the limits of geological time just stated, 

are compared in respect of their organic contents, distinctions more or less 

marked appear (as for example, conspicuously in the strata of the Silurian 

system), yet these mostly turn on nice differences of some of the analogous 

forms, and may perhaps have only a local value, as we know to be the case 

in the instance of the oolitic strata.

On the contrary, if we compare the whole series of organic forms found in 

these Palaeozoic Strata, as they are exhibited in Wales or Cumberland, with 

the whole series of fossils discovered in the carboniferous system of the north 

of England or the border of Wales, we find not more than 1, 2, or 3 per cent.
12 GEOLOGIC TIME CLASSIFICATION

of intimately related species. The distinction between the Silurian fossils 

and those of the mountain limestone is of the same order as that which 

obtains between the latter series and the fossils of the magnesian limestone. 

Struck with this fact, Mr. Murchison has suggested for the early groups of 

strata the title of "protozoic rocks," which (beside one chance of ambiguity 

from the meaning attached in zoology to the word " Protozoa ") seems to assert 

more than is necessary, perhaps more than is known. We prefer therefore to 

apply to the same strata the title of Palaeozoic, which seems liable to no 

objection, and which has, we believe, been occasionally employed by Professor 

Sedgwick.

Supposing, as we think likely, that general terms for stratified rocks, thus 

formed upon a consideration of their organic contents, which appear to follow 

a great law of succession, will be preferred to others based on a view of their 

mineral qualities, which are certainly subject to repetition, there will be no 

other difficulty in their construction or application than what may be overcome 

by the progress of investigation. As many systems or combinations of organic 

forms as are clearly traceable in the stratified .crust of the globe, so many corresponding terms (as Palaeozoic, Mesozoic. Kainozoic [Cenozoic], &c.), may be 

made, nor will these necessarily require change upon every new discovery. 

For instance, the term Palaeozoic may be retained, though it should be found 

that the application of it ought to be extended so as to include the carboniferous rocks or even the magnesian limestone ("Zechstein" of Germany). 

This indeed is not unlikely, for the following reasons. First, it is the opinion 

of eminent living geologists (Professor Sedgwick, Mr. Murchison, and others) 

that in strata which correspond in age to the old red-sandstone, there occur 

groups of organic remains intermediate in forms and combinations between 

the types of the Silurian and carboniferous aeras. Secondly, it is ascertained 

that a large proportion of the forms of zoophyta, mollusca, and fishes, which 

appear in magnesian limestone, are extremely analogous to or even identical 

with some of the more numerous species of the mountain limestone. At present the Palaeozoic series of rocks includes the following formations, placed in 

the order of position, according to the most recent views:

Old Red-Sandstone This in whole or in part is supposed by Mr. Murchison 

and others to be represented by the calcareous, arenaceous, and argillaceous 

rocks of North and South Devon, Cornwall, part of Brittany, the Harz, Westphalia; and they prefer to call the series Devonian, from the country where 

it is supposed to be best developed.

Silurian Rocks. Mr. Murchison ranks these in four formations, viz. Ludlow 

Rocks, Wenlock Rocks, Oaradoc Rocks, Llandeilo Rocks.

Cambrian Rocks. Professor Sedgwick subdivides them into Plynlymmon 

Rocks, Bala Limestone, and Snowdon Rocks.

It is supposed, but perhaps has not been perfectly ascertained, that the 

rocks of Skiddaw, &c., which come next in order below, are deficient of 

organic remains. May we propose for these and other lower stratified rocks 

the term "Hypozoic Series?"

J. Phillips, 1841 (Palaeozoic fossils of Cornwall, Devon, and West Somerset i 

Great Britain Geol. Snrvey Mem., p. 160).

I have suggested* the propriety of extending the application of this term 

[Palaeozoic] so as to make it include not only the " Silurian " group, but all 

the newer types of organization up to the magnesian limestone; and following 

out this plan of nomenclature, have presented an outline of a general classia " Penny Cyclopaedia," articles Geology, Palaeozoic rocks, Saliferous system, etc.
THE ERA TERMS 13

flcation on the evidence of organic remains, which fortunately clashes very 

little with the ordinary scheme founded on structural, mineral, and chemical 

analogies of the rocks.

As this classification will be employed in some of the following pages, it 

is here offered in the original form: 

Proposed Titles depending 

on the Series of 

Organic Affinities. Ordinary Title.

Upper=Pleiocene Tertiaries.

Cainozoic [Cenozoic] Strata Middle=Meiocene Tertiaries.

Mesozoic Strata.

Palaeozoic Strata <

Lower=Eocene Tertiaries. 

Upper=Cretaceous System. 

Middle=0olitic System. 

Lower=New Red formation.

(Magnesian Limestone formation. 

Upper? =|carboniferous System.

Middle? = (Eifel and South Devon).

[Transition Strata. 

Lower =|primary Strata.

(The terms are founded on ,the verb faw or fww to live, combined with 

Kau>6s recent [Cenozoic], ftecos medial or middle [Mesozoic], and ira\ai6s 

ancient [Paleozoic].)

As originally defined, in 1838, the Paleozoic included only the 

Cambrian, Ordovician, and Silurian periods (or systems) of the 

present classification. The definition of 1840 added to it the " Old 

Red sandstone " (Devonian of the present day), and also suggested 

the inclusion of the overlying Carboniferous, but as the term Carboniferous was then used it did not include Permian. The definition 

given by Phillips in 1841 added to the Paleozoic not only the Carboniferous as then recognized but the overlying " Magnesian Limestone formation " as well. In 1841 and 1845 the term Permian was 

introduced by Murchison, De Verneuil, and Von Keyserling to include the " Magnesian limestone " and the lower part of the " New 

Red sandstone," and the Permian was assigned to the Paleozoic era. 

This definition of Paleozoic is the one almost universally employed 

to-day.

The meaning of the word is old or ancient life. In the rocks of the 

oldest, or Cambrian, period of the Paleozoic era no traces of land 

animals have been found, brachiopods and the marine crustaceans 

known as trilobites being the most characteristic animals entombed 

in the Cambrian rocks, but seaweeds were abundant. In the next 

period, the Ordovician, shell-forming sea animalsj especially cephalopods and brachiopods, became abundant, the culmination of the 

trilobites was reached, and the first trace of insect life appeared. In 

the succeeding Silurian period shell-forming sea animals became 

dominant, especially those related to the nautilus (cephalopods). 

The Silurian also witnessed the rise and culmination of the marine 

animals sometimes known as sea lilies (erinoids), and of giant
14 GEOLOGIC TIME CLASSIFICATION

*

scorpion-like crustaceans (eurypterids), as well as the rise of fishes 

and reef-building corals. In the Devonian period fishes became 

abundant, and hence the Devonian is known as the " age of fishes." ^ 

The Devonian also witnessed .the rise of amphibians and land plants. 

In the closing period of the Paleozoic era, the Carboniferous, club 

mosses (lycopods) and plants of horsetail and fern types dominated 

the floral life, while primitive flowering plants and the earliest conebearing trees appeared. Among marine animals brachiopods were -.. 

still the most common invertebrates, and primitive sharks were the 

most abundant fishes. Reptiles and insects also appeared, and amphibians increased to such an extent that the Carboniferous period 

is known as the " age of amphibians." ~"

PBE-CAMBBIAN EBA TERMS

The pre-Paleozoic rocks have been classified in many ways, and 

opinion regarding their classification is still divided, as shown by 

the accompanying chart and by the pages that follow.

The classification of these rocks on a life basis has led to the introduction of many terms ending in "zoic," regarding the use of 

which there has been and still is great diversity of opinion. Each v 

one of these zoic terms has, in fact, been applied to both the whole c ( 

and to one or more parts of the pre-Paleozoic rock assemblage, as 

shown by the following quotations, which are arranged in the alpha- V 

betic order of the terms. Although these quotations have been assembled after considerable research, they are not offered as a com- t: 

plete resume of the literature bearing on the subject. They will, 

however, serve to show the diverse usages of the pre-Cambrian zoic 

terms. The United States Geological Survey classifies all pre-Cambrian rocks under one zoic term, namely, Proterozoic era.

"AGNOTOZOIC ERA"

R. D. Irvingr, 1887 (Am. Jour. Set., 3d ser., vol. 34, p. 373).

The general term to be used to cover the great pre-Cambrlan interval should 

then express the existence of this early life, and our present ignorance with 

regard to its nature. During the year and a half that such an addition to 

geological nomenclature has been under discussion between myself and several 

of my fellow-geologists, many terms have been proposed and discussed. Some 

of these-have been rejected because, though sufficiently appropriate, they have 

already been too generally used in other connections. Others again seemed inadmissible because, while expressing well the idea to be presented, they were 

made up of derivatives from the Greek not ordinarily met with in the English 

language, and were too cumbersome and pedantic in sound. Others again, like 

Proterozoic '(irp6repos, earlier), suggested by Mr. Emmons, while simple and 

made from a Greek word of not too uncommon use, seemed to fail in covering 

the ground sufficiently. I have therefore been disposed to return to a term early 

proposed by Professor T. C. Chamberlin, to whom indeed is to be assigned the
THE BRA TERMS 15

first suggestion of the use of a single name to cover all of the pre-Cambrlan 

fragmentals. I would advocate, therefore, the use of the term Agnotozoto 

(&YI/WTOS, unkno^vn; fan?, life), to cover all of the geological interval lying between the base of the Cambrian and the summit of the Archean crystallines.

R. D. Irving, 1888 (U. S. Geol. Survey Seventh Ann. Kept., pp. 453-454).

It seems, therefore, desirable that a new term should be introduced of equal 

classificatory rank with Paleozoic, indicating that these great Pre-Cambrian 

and Post-Archaean series are zoic in character and that they cannot, as yet 

at least, be admitted to the Paleozoic series proper. In an article in the American Journal of Science for 1887 (page 373) I advocated the adoption of the 

term Agnotozoic (Hyvuros, unknown; fwij, life), indicating at once the presence of life and its unknown character. A recognized objection to this 

term may be based upon the consideration that if definite faunas shall be 

discovered in these formations or in any of them the term Agnotozoic would 

be inapplicable. To this it may be replied that it is improbable that such 

discoveries will be made in all of the formations included under this term and 

that it will still be needed for the residue. If definite faunas are found in any 

of them and these prove to be Paleozoic in character, the formation containing 

them will simply be transferred to the Paleozoic series and the remainder of 

the formations left under the term Agnotozoic. If, on the other hand, the 

faunas prove to be diverse from the Paleozoic, a new zoic group bearing a name 

appropriate to the discovered life will be required in any case, whether the 

term Agnotozoic or any other imaginable term be now applied to the formation. 

Some of my colleagues upon the survey, however, prefer the more noncommittal term Eparchsean, signifying simply the position of these formations 

upon the Archsean. To this term the same objection applies as to the preceding, 

that the discovery of a definite fatma would necessarily call for an appropriate 

zoic classification, under the canons of good nomenclature. In short, it may 

be safely remarked that, while there is an imperative demand for a separate 

term adapted to the present needs of the science, any term now proposed must 

be held subject to future limitation or entire replacement, if any sufficiently 

distinctive paleontological discoveries shall be made.

The following table shows the arrangement of formations suggested, in 

which the terms Agnotozoic and Eparchsean are both introduced: 

Systems Groups Systems

Carboniferous

Devonian Paleozoic > Silurian

Agnotozoic

or

Eparchsean

Cambrian (Lower Silurian)

Kevveenawan

Huronian

(other groups?)

Paleozoic

fLaurentian (including 1 Archsean | Upper Laurentian) JArchsean.

T. G. Chamberlin, 1888 (Am. Jour. Sci., 3d ser., vol. 35, p. 254).

Prof. 11. D. Irving has advocated the adoption of the term "Agnotozoic" as 

a comprehensive designation for the fragmental rocks which lie between the 

base of the Cambrian formations and the summit of the Archsean crystallines, 

and has credited me with the authorship of the term and the early advocacy of 

the desirableness of a distinct name for these formations. Concerning this I 

wish to file a disclaimer; not that I do not fully concur with Professor Irving
16 GEOLOGIC TIME CLASSIFICATION

* in this advocacy, for I do most cordially, nor because I suppose it to be a

matter of consequence to Professor Irving, since I know that he holds all 

questions of priority or proprietorship in nomenclature in little esteem, if 

not in light contempt. I wish to file the disclaimer not because of this special 

case but out of respect for a general principle in nomenclature, which I hope to 

see adopted to the displacement of a purely technical and indiscriminative application of the law of priority. I hold that nomenclature of the class in 

question should rest, not with some individual, who, standing by and looking 

upon the work'of others, may see, perchance before they do, whereunto their 

labors are growing; nor with some one, who, on the basis of superficial ob- ,.. 

servation and hasty conjecture, throws out first to the world a tentative 

nomenclature, leaving it to the future and to the labors of others to justify 

or reject; but on the contrary, I hold it should rest witli the patient and 

thoroughgoing investigator, who by careful and comprehensive study develops 

an adequate basis for nomenclature, 'properly sanctioned by a broad and trustworthy array of facts. I have been in some senses a student of the formations 

to be embraced under the proposed term, but in no such sense as to give me the 

right of nomenclature under this principle. If, therefore, this term shall be 

adopted, as I sincerely trust it may, I earnestly desire that it shall stand to 

the credit of some one who has had a larger part in the actual development of 

the facts upon which its adoption 'must rest, among whom I know of no one 

who has contributed more than Professor Irving.

J. W. Dawson, 18SS (Geol. Soc. London Quart. Jour., vol. 44, p. SOS, footnote). /

Irving has proposed to call all the formations between the Laurentian and i 

the base of the Cambrian " Agnotozoic;" but the term Huronian seems sufficient at present for this purpose. i

E. Kayser, 1893 (Textbook of comparative geology, translated, and edited 

by Philip Lake, pp. 10, 13, 15).

[See quotation under "Azoic era"] 

E. Hang, 19O8 (Traite de geologic, tome 2, pp. 5GG-58G).

Agnotozoic era:

Algonkian period. In America divided into

Keweenawan.

Huronian. 

Archean period. In America divided into

Laurentian.

Keewatin.

C. R. Van Hise, 1908 (Geol. Soc. America Bull., vol. 19, pp. 27-28).

[Proposes Proterozoic, Instead of "Agnotozoic," to include all pre-Cambrian time. See 

quotation under Proterozoic era]

C. R. Van Hise and C. K. Leith, 19O9 (U. S. Geol. Survey Bull. 36O, pp. 19-21).

[Propose Proterozoic, instead of "Agnotozoic," to include all pre-Cambrian time. See 

quotation under /Proterozoic era]

" Agnotozoic" is derived from the Greek words iiyvuiTos (unknown) and fat (life). The time covered by it, in both its narrow 

and its broad sense, is included in the Proterozoic era by the United 

States Geological Survey. In its original (narrow) usage it cor-
THE ERA TEEMS 17

responds to the Algonkian period. In its broad usage it includes 

both the Algonkian and Archean periods and corresponds to the 

Proterozoic era of the United States Geological Survey.

" ARCHEOZOIC ERA " 

J. D. Dana, 1872 (Corals and Coral Islands, App., p. 373).

Geological history begins with what has been called Azoic time, azoic signifying ttie absence of all life. But the rocks supposed to be Azoic have 

been found to afford evidence of the existence of the simplest kinds of life 

during their formation; and the era they represent, is, therefore, more correctly styled the Archeozoic, from the Greek for beginning and life. The 

other grand subdivisions of geological time, are as follows: Palaeozoic time 

(named from the Greek for ancient life) * * *.

K. A. von Zittel, 1880 (Handbuch der Palteontologie, Bd. 1, Abt. 1, p. 24).

Palaeozoic period: 

» * s.- 

Silurian formation at base (including Cambrian).

Archeozoic period:

Primitive slate formation. 

Laurentian gneiss formation. 

Primitive gneiss formation.

J. D. Dana, 1802 (Am. Jour. Scf., 3d Her., vol. 43, pp. 460-461).

[Proposes the same classification as that given in the next quotation, from the 1895 

edition of his Manual of geology. In addition he states:]

The Algonkian (or Agnotozoic) beds belong either to the Archaean or to 

the Paleozoic.

The Archaean division of geological time is of the same category with the 

Paleozoic, Mesozoic, and Cenozoic; all are grand divisions based on the progress 

of life, and they include together its complete range. There is no room for 

another grand division between Archaean and Paleozoic any more than for one 

between Paleozoic and Mesozoic. In contrast, the Algonkian division is not 

above the Cambrian in grade, it being based on series of rocks. Its true 

biological relations are in doubt, because fossils representing the supposed 

life of the period are unknown, or imperfectly so.

J. D. Dana, 1895 (Manual of geology, 4th ed., pp. 4O4-413, 44O 153).

[Geologic time is divided into] four primary divisions, the Archaean, Paleozoic, 

Mesozoic, and Cenozoic. [Page 404.]

I. Archaean Time. The beginning of Archaean time was without life; but 

before it closed conditions had been reached that admitted of the existence of 

pvotophytic and protozoic life. [Page 407.]

I. Archcean Time. There are the two divisions, the Azoic and the Archwozoic, but they are not distinguishable in the rocks. The rocks have been 

divided into 

1. Laurentian. [Bottom.]

2. Huronian. [Top.] [Page 407.] 

[Archaean time is divided as follows:]

Archceozoic ceon. Life in its lowest forms of existence:

Era of first animal life.

Era of first plants.
18 GEOLOGIC TIME CLASSIFICATION

Azoic (eon. Without life: 

Oceanic era. 

Lithic era.

Astral won, as it has been called, or that of the fluid globe having a 

heavy vaporous envelope containing the future water of the globe or 

its dissociated elements, and other heavy vapors or gases. [Pages 

440-441.]

The subdivision of Archaean time into Azoic and Archseozoic, here used, is 

the same as that of the edition of 1874, except that Archseozoic is substituted 

for Eozoic. The limiting temperature of Archseozoic time is doubtful for 

several reasons, and especially because of the uncertainty as to the destructive excess of carbonic acid in the air and waters, and, therefore, as to the 

possibility of the existence of life. [Page 442.]

Subdivisions of the Archsean terranes, and the rocks. Two subdivisions 

have general acceptance: 

I. The Laurentian.

II. The Huronian era. [Page 445.]

The Keweenaw formation is without fossils, and hence is of uncertain age; 

but its relations appear to be probably Paleozoic. [Page 447.]

Although fossils, according to present knowledge, are absent from Archsean 

rocks, or are of questionable character, the existence during the later part of 

the Archsean of aquatic life in its simplest forms is rendered almost certain 

by the fact that the temperature of the waters was favorable to it, and by 

the occurrence among the stratified rocks of beds of limestone; by the 

abundance in many limestones, and other rocks, of graphite, which constitutes 

20 per cent of some layers in Canada; and by the presence in the Huronian 

of carbonaceous shales or slates containing 40 per cent of carbonaceous materials. The life belonged to that division of Archsean time which is designated, 

on page 441, the Archseozoic seon; and the Huronian rocks represent the latter 

part of this seon, if not the whole of It [Page 453.]

J. Le Conte, 19O3 (Elements of geology, revised and partly re-written by 

H. L. Falrchlld, 5th ed., pp. 293, 294, 295).

Archseozoic era:

Algonkian age. Evidences of life.

Huronian period. 

Archsean age. No evidences of life.

Laurentian period.

T. C. Chamberlln and R. D. Salisbury, 1906 (Textbook of geology, vol. 2, 

pp. 137-138, 162).

On the planetesimal hypothesis, the oldest rocks to which we might hope to 

gain access would be those referred to the Extrusive eon, during which more 

or less sedimentary rock was mingled with the volcanic. On this hypothesis, 

as on the preceding, no sharp line of demarkation would be expected between 

dominantly sedimentary rocks above, and dominantly non-sedimentary rocks 

below.

The rock-formations now most widely exposed at the surface are sedimentary, and were therefore formed during the time of atmospheric and hydrospheric dominance, that is, during the great Gradational eon. In not a few 

places, however, formations of dominantly extrusive-igneous or meta-igneous 

origin are found, either beneath the prevailing sedimentary rocks, or projecting up through them in such relations as to show their greater age. In
THE ERA TEEMS 19

many cases these inferior rocks were thoroughly metamorphosed, and in essentially their present condition, before the deposition of the overlying beds, for 

masses of metamorphic rock derived from them are included in the nonmetamorphic series above. These igneous and meta-igneous formations which 

antedate the oldest known series of rocks made up chiefly of sediments, are 

the oldest rock-formations known, and the era during which they were formed 

is therefore the first era of which there is definite record in the accessible 

formations of the earth.

These rocks consist of a very complex series of formations, embracing lava 

outflows, volcanic tuffs, igneous intrusions of various types and exceptional 

extent, together with some sedimentary deposits, all usually metamorphosed 

and notably deformed. Distinct fossils have not been found in these rocks, 

but the occasional presence of (1) carbonaceous shales very similar to 

younger shales which derived their carbon from organic sources, (2) ironore beds similar to those which owe their origin to plant action, and (3)

occasional limestones and cherts which, as a class, are usually the products

of organic action, are thought to imply the existence of life, and to warrant 

placing the era when these rocks were formed in the " zoic" group. This 

view is supported by the theoretical probability that life extended back 

through a vast period unrecorded by fossils, since the earliest fossils yet 

found imply a very prolonged antecedent evolution. The era during which, 

or during the later part of which, this oldest system of accessible rock formation was made, is the Archeozoic era.

Under the planetesimal hypothesis, the oldest known rocks may be confidently referred to the Archeozoic era. * * *

It has been thought by leading geologists especially engaged in the investigation of these formations, that the pre-Cambrian systems of dominantly sedimentary rocks should be separated from the dominantly igneous or metaigneous complex below.8 Following their lead, these pre-Cambrian systems of 

rock, composed .chiefly of sediments, are here separated from the Archean, 

and designated Algonkian or Proterozoic. * * * [Pages 137-138.]

To the Proterozoic 4 era is assigned the time that elapsed between the close 

of the formation of the igneous complex and the beginning of the lowest 

system which is now known to contain abundant well-preserved fossils; or in 

other words, the time between the close of the Archean and the beginning of 

the Paleozoic. [Page 162.]

E. Kuyser, 1011 (Lelirbnch der Geologic, p. 12).

Eozoic or Proterozoic group (Algonkian). 

Azoic or Archeozoic group (Archean).

B. Kayser, 1012 (Lelirlmch der allgemelnen Geologic, 4th ed., p. 138).

Eozoic or Archseozoic rock group (Algonkian). 

Azoic or Archean rock group (Urgebirge).

V

T. C. Chamberlln, 1914 (Cong. g6ol. Internal., 12th sess., Toronto, Compt.- 

rend., p. 425).

[Explains the basis on which he divides pre-Paleozoic time into two eras Proterozoic 

and Archeozoic. See quotation under Proterozoic era]

A. P. Coleinan, 1015 (Problems of American geology, Yale University Pub., 

p. 90).

[See quotation under Proterozoic era]

8 Irvlng, Seventh Ann. Kept., U. S. Geol. Surv., pp. 448-454, and Van Hise, Bull. 86, 

U. S. Geol. Surv., pp. 491-493. 

* Proterozoic, as here used, is a synonym for Algonkian. as used by the U. S. Geol. Surv.
20 GEOLOGIC TIME CLASSIFICATION

C. Schuchert, 1915 (Textbook of geology, pp. 444 445, 540).

[See quotation under Proterozoic era]

H. F. Cleland, 1916 (Textbook of geology, >pp. 384, 383).

[See quotation under Proterozoic era] 

A. Grabau, 1921 (Textbook of geology, p. 20).

[See quotation under Proterozoic era] 

J. Walther, 1921 (Geologic von Dentschland, 3d enlarged, ed., p. 48).

Palaeozoic:

* * *

Silurian at base. 

Archseozoic: 

Cambrian. 

Algonkian. 

Crystalline rocks.

K. A. von Zlttel, 1921 (Grundziige der Paleeontologle, Abt. 1, chart opp, 

P. 8).

Palaeozoic group:

* * *

Cambrian at base (Upper, Middle, and Lower Cambrian). 

Archseozoic=Eozoic group (pre-Cambrian, Proterozoic, Algonkian). 

Azoic group=Archsean, Urgebirge.

J. Stiny, 1922 (Technische Geologic, pp. 554-559).

Cambrian (Upper, Middle, and Lower). 

Algonkian (Eozoic, Archeozoic). 

Archaean (Urgebirge).

A. P. Coleman and W. A. Parks, 1922 (Textbook of geology, p. 154).

[S'ee quotation under Proterozoio era] 

C. Scb.ncb.ert, 1924 (Textbook of geology, 2d ed., -vol. 2).

[See quotation under "Eozoic era"]

"Archeozoic" is derived from the Greek words dpxcuoj (ancient, 

primitive) and fwi? (life). The time covered by it, as variously 

used by different authors (except those who include the Cambrian 

in it), is included in the Proterozoic era by the United States Geological Survey. As originally used it included all pre-Paleozoic time. 

In later usages it has been applied (1) to the Algonkian period only, 

(2) to the Archean period only, and (3) to the Cambrian, Algonkian, 

and Archean periods.

" AZOIC ERA "

R. I. Mnrcblson, E. de Verneuil, and A. von Keyserling, 1845 (The geology 

of Europe and the Ural Mountains, p. 10*).

To the crystalline masses which preceded that Paleozoic succession to which 

our researches were mostly directed, we apply the term "Azoic," not meaning thereby dogmatically to affirm, that nothing organic could have been in 

existence during those earliest deposits of sedimentary matter, but simply 

as expressing the fact, that in as far as human researches have reached,
THE ERA TERMS 21

no vestiges of living things have been found in them, so also from their 

nature they seem to have been formed under such accompanying conditions 

of intense heat and fusion, that it is hopeless to expect to find in them 

traces of organization. * * * In the term' Azoic rocks, we include all 

the crystalline masses belonging to the ancient group of gneiss, together with 

ancient granitic and plutonic rocks by which they have been invaded. * * * 

[In footnote:] Hypercritically, it may be said that this word might also be 

applied to other deposits! of subsequent age, in which the organic remains are 

also obliterated, and thus be merged with Hypogene of Lyell. But in our 

sense the word azoic is synonymous with pro-zoic, or before the recognizable 

traces of life. Professor Phillips has applied the word Hypozoic to the 

same rocks which we term Azoic.

J. W. Foster and J. D. Whitney, 1851 (Am. Assoc. Adv. Set. Proc., -vol. 5, 

P. 4).

The term Azoic (from A-, negative, and fan}, life) was first applied by 

Murchison and de Verneuil, to designate a class of crystalline rocks, which 

occur around the Gulf of Finland, whose geological position is below the 

Silurian System. In it, they include not only gneiss and mica slate, but 

the igneous rocks, such as granite and diorite, by which they are invaded. 

We adopt the term, but limit its signification, by applying it to a class of 

rocks supposed to be detrital in their origin, and to have been formed before 

the dawn of animal or vegetable life. It comprises the most ancient of the 

strata which form the crust of the earth, and occupies a distinct position in 

the geological column; being below the Potsdam sandstone.

J. \V. Foster and J. D. Whltney, 1851 (Report on the geology of the Lake 

Superior land district, pt. 2, p. 3).

Below all the fossiliferous rocks of this [Lake Superior] region, there 

is a class of rocks, consisting of various crystalline schists, beds of quartz 

and saccharoidal marble, more or less metamorphosed, which we denominate 

the Azoic system. This term was first applied by Murchison and de Verneuil 

to designate those crystalline masses which preceded the palaeozoic strata. 

In it, they include not only gneiss, but the granitic and plutonic rocks by 

which it has been invaded. We adopt the term, but limit its signification 

to those rocks which were detrital in their origin, and which were supposed to have been formed before the dawn of organized existence.

A. d'Orblgny, 1852 (Cours elementaire de paleontologle et de geologic 

stratlgraphlques, tome 2, fa.sc. 2, pp. 263 et seo.).

Paleozoic (Silurian at base).

Azoic. The Azoic stratified rocks preceded the appearance of animal 

life on the globe.

D. Page, 1854 (Introductory textbook of geology, p. 30).

Palaeozoic period (ancient life) : 

* * *

Silurian at base. [Includes Cambrian.] 

Azoic period (void of life) :

Non-fossiliferous epoch, or Metamorphic system.

J. 1). Dana, 1863 (Manual of geology, 1st ed., pp. 130, 131, 134, 142, 145-146} 

also editions of 1864, 1868, and I860, same pages).

Preceding these [the "Age of Mollusks, or Silurian," including Potsdam at 

base], there is the Azoic era, the name being derived from the Greek
22 GEOLOGIC TIME CLASSIFICATION

*

&- and fwij, life, and signifying the absence of life. The Azoic rocks are mostly 

crystalline. [Pages 130, 131.]

The Azoic age is the age in the earth's history preceding the appearance of ^ 

animal life. The fact of the existence of the globe at one time in a state of 

universal fusion is placed beyond reasonable doubt. And whatever events 

occurred upon the globe from the era of the elevated temperature necessary to ^M 

fusion, down to the time when the climate and waters had become fitted for 

animal life, are events in the Azoic age. The age must, therefore, stand as the 

first in geological history, whether science can point out unquestionably the 

rocks of that age or not. [Page 134.] ^

The Azoic rocks in North America at present include all that are older than ^ 

the Potsdam sandstone of New York, the first of the Silurian. [Page 134.] 7

The Azoic rocks of Canada are divided by Logan into the Laurentian / 

[including Keewatin], including the great part of the system, and embracing all the regions to which we have above particularly alluded, and the 

Huronian, comprising a narrow band on the borders of Lake Superior and 

Lake Huron. [Page 142.]

The term " azoic," as here used, implies absence of life, but not necessarily 

of the lowest grades.

The reasons in favor of the existence of life of some kind are 

1. The formation of limestone strata in the Azoic age like those of the Silurian, in connection with the fact that Silurian and later limestones are known 

to be mainly made from organic, relics. * * *

2. The occurrence of graphite in the limestone and other strata, graphite , 

being known to be a common result of the exposure of mineral coal or charcoal to a high heat, and, in certain rocks of Rhode Island and Massachusetts, ^ 

having undoubtedly been made from vegetable remains. * * * ,

3. The occurrence of anthracite in small pieces in the iron-bearing rocks of V 

Arendal, Norway, which rocks are probably Azoic in age. [Pages 145-146.]

E. Hitchcock and O. H. Hitchcock, 1868 (Elementary geology, pp. 41-43, 

60, 63).

Palaeozoic (ancient type of organic life) : 

* <s *

Cambrian or Huronian series at base. [Pages 43, 63.] 

Azoic (Interzoic and Hypozoic or Laurentian). The term Azoic signifies 

unfossiliferous. and is the most satisfactory appellation for these 

crystalline rocks, which are not only the oldest rocks upon the globe, 

but are also found among the higher groups. The term Hyposoic 

signifies that the rocks embraced in the system lie beneath those containing fossils. * * * The term Laurentian applies only to the 

lower part of the Azoic rocks, the upper part forming the Huronian 

system. 

Unstratified or igneous rocks:

Below the Azoic series are the unstratified rocks, which extend to 

unknown depths.

H. Credner, 1872 (Elemente der Geologic, 1st ed., pp. 264-288).

Paleozoic group (Silurian the basal system). 

Azoic group (Primitive, pre-Silurian, Eozoic) :

Huronian slate formation (including Cambrian formation in part).

Laurentian gneiss formation.
J"

THE ERA TERMS 23

H. Credner, 1876 (Elemente der Geologic, 3d ed., pp. 353-384) ; 1879 (Trait 6 

de geologic et de paleontologle, 3d ed., pp. 338-365) j and 1887 (Elemente 

der Geologic, 6th ed., pp. 877-408).

Palaeozoic group (Silurian the basal subdivision).

Archean group (Primitive, pre-Silurian, Azoic or Eozoic). The word

Archean, which does not prejudice the question of the appearance of

life on the earth, is preferred to the two others [Azoic and Eozoic].

It is composed of *

Huronian or formation of crystalline slates (including Cambrian

formation in part). 

Laurentian or formation, of primitive gneiss.

J. D. Dana, 1875 and 1880 (Manual of geology, 2d ed., pp. 138-139; 3d ed., 

pp. 140-1GO).

The following subdivisions of geological time are here adopted:

I. Archwan time. The beginning, including a very long era without life, and,

finally, that in which appeared the earliest and simplest forms of plants and

animals.

.II. Silurian age, or age of invertebrates. * * * [Pages 138-139.] [According to table on p. 142 and the text his Silurian included Cambrian.] 

The subdivisions of geological time are, then, 

I. Archaean time, including an Azoic and an Eozoic era, though not yet distinguished in the rocks.

1. Azoic age. [Bottom.]

2. Eozoic age. [Top.]

II. Paleozoic time. * * * [Page 140.]

Archaean time includes strictly, at its commencement, an Azoic age, or the 

era in which the physical conditions were incompatible with the existence of 

life. But this era, so far as now known, is without recognizable records ; for 

no rocks have yet been shown to be earlier in date than those which are now 

supposed to have been formed since the first life began to exist. About this 

early era there is, therefore, little known. By following the lead of ascertained 

law in physics and chemistry, and the suggestion of astronomy, and also analogies from later geological history, some probable conclusions may be reached. 

But this is not the place for their discussion, except so far as to state the principal steps of progress. There must have been, 

I. A first era, after that of the original nebula, if such there was, in which 

the earth was a globe of molten rock, like the sun in brightness and nature, 

enveloped in an atmosphere containing the dissociated elements of the future 

waters and whatever else the.heut at the surface could throw into a state of 

vapor.

II. A second era, in which cooling went forward until the exterior became 

solid from cooling, and probably as a crust over a liquid interior. * * *

III. A third era, or a continuation of the preceding, carrying forward the 

cooling to 80° or 100° C. (175° to 212° F.), or to a, temperature admitting of 

the existence of the simplest forms of vegetable life. * * *

IV. A fourth era, commencing with the beginning of life on the globe, 

which beginning was possible, judging from known facts, when the temperature 

of the waters had cooled down at least to 200° F. It has been supposed that 

all the Archaean rocks open to view over the earth's surface are those of this 

last era. But more investigation is required, before it can be regarded as an 

established fact that none of earlier time are open to investigation. From 

these rocks in America, two principal periods have been indicated, with other 

subdivisions. * * * [Pages 147-148.]
24 GEOLOGIC TIME CLASSIFICATION

This formation in North America was first distinctly recognized in its 

true importance in the Report of Foster and Whitney on the Lake Superior 

region, in which it was named the Azoic system. Dawson, after his announcement of the animal nature of the Eozoon, suggested the name Eozoic (from 

i)wj, dawn, and fw^, life). As the supposed Eozoon may be of mineral nature, f< 

its use here is objectionable. * * * [Page 148.] 3

II. Periods of the Archoean era. In Canada, where these rocks in North " 

America are most fully represented, two periods have been recognized: 1, The 

Laurentian, the older, so named from the river St. Lawrence; and 2, the 

Huronian. The estimated thickness of the rocks of the Laurentian period is V 

30,000 feet; of the Huronian, from 10,000 to 20,000 feet. [Page 151.] (

No distinct remains of plants have been observed. The occurrence of ~i 

graphite in the rocks, and its making 20 per cent of some layers, is strong , 

evidence that plants of some kind, if not also animals, were abundant. * * * * 

[Page 157, under heading life (of Laurentian period).]

Animals of the lowest division of animal life, that of Bhizopods among 

Protozoans, were probably abundant. * * * [Page 158, under heading 

life (of Laurentian period).] Whatever may be the final decision with regard to Eozoon, there can be little doubt that Rhizopods existed in Archaean 

time. [Page 159, under heading life (of Laurentian period).]

As the original Huronian has no fossils, there is no basis for a satisfactory 

determination of its equivalents. It is quite possible that it is Cambrian or '* 

Primordial. [Page 160.]

C. Vogt, 1879 (Lehrfouch der Geologic und Petrefnctenknnde, pp. 225 235).

Palaeozoic group (Cambrian at base). >. 

Lowest formation (Archaean system, Primitive formation, Azoic system, Laurentian and Huronian, Bottom-rocks). L>

K. A. von ZIttel, 1883 (Trait6 de palfiontologle, tome I, pt. 1, p. 22).

Palaeozoic era or group: 

* * *

Cambrian system at base. 

Azoic era or group:

System of primitive schists. 

System of Laurentian gneiss. 

System of fundamental gneiss.

J. D. Whitney and M. E. Wads-worth, 1884 (Mns. Comp. Zool. Harvard Coll. 

Bull., vol. 7, Geol. »er., vol. 1, No. 11, p. 562).

Proposed chronological arrangement of crystalline rocks: 

Azoic:

Pelodlan (argillites).

Glacian (conglomerates).

Taconian (limestones).

Crystallian (quartzites, quartz schists).

Montalban (mica schists).

Huronian (diorites, diabases, melaphyrs, chlorite schists).

Porphyrian (porphyrites).

Arvonian (felsite, quartz porphyry, petrosilex, jaspilite).

Norian (gabbro, coarse diabases and diorites).

Ophian (peridotites, including serpentines).

Siderian (magnetite, hematite, menaccanite).

Laurentian (granites, gneisses, syenites).
THE ERA TEEMS 25

J. D. Dana. 1892 (Am. Jour. Set, 3d Her., vol. 48, pp. 460-461) and 1895 

(Manual of geology, 4th ed., pp. 44O-441).

Archaean:

Archseozoic aeon (life in its lowest forms of existence) :

Era of first animal life.

Era of first plants. 

Azoic aeon (without life):

Oceanic era

Lithic era 

Astral aeon, as it has been called, or that of the fluid globe having

a heavy vaporous envelope containing the future water of the

globe or its dissociated elements, and other heavy vapors or

gases.

E. Kayser, 1893 (Textbook of comparative geology, translated and edited 

by Philip Lake, pp. 10, 13, 15).

Azoic or Archaean group: Under the head of Archaean we group together all 

those rocks which are older than the lowest beds of the Cambrian, and which 

extend from these as their upper limit to the deepest, so-called Laurentian, 

gneiss. The terms fundamental or Primitive (terrain primitif of the French), 

Azoic or Agnotozoic, and Pre-Cambrian have also been used with the same 

signification.

The Archaean rocks must be considered unfossiliferous, since it has been 

shown that the supposed fossils found towards the middle of the century in 

Canada and afterwards in Scotland, Scandinavia, and Bohemia, are of inorganic origin. These supposed fossils occur in crystalline limestone in the 

gneiss and form nodular masses consisting chiefly of serpentinous material 

divided by numerous tubes swelling out into cells. They were described as 

giant Foraminifers under the name Eozoon, but have been shown, thanks especially to the minute microscopic researches of Mo'bius, to be inorganic. On 

account of this absence of fossils the name Azoic (first used by Murchison in 

1845 for the old crystalline mass of Scandinavia) has been applied to these 

rocks. * * * The strongest evidence of the existence of organized life 

during the Archaean period, is to be found in the relatively high organization of 

the oldest known fauna, the Cambrian. The high development of this fauna 

indeed necessarily forces us to the conclusion that it was preceded by one or 

more, probably a whole series, of older faunas, the remains of which we may 

expect in time to find in the Archaean. So long, however, as such remains have 

not been found, it is advisable instead of the as yet unwarranted term Eozoic, 

to keep to the expression Archaean introduced by Dana (1874).

K. A. von Zlttel, 1903 (Gmintlziige der Palteontologle, Abt. 1, pp. 5-O).

Palaeozoic group (Cambrian system at base). 

Archean (or Azoic) group:

Primitive slate system.

Gneiss system.

A. B. Tftraebohm and A. Hennlg, 1904 (Sverigres geologiska TJndersSkiiing, 

ser. Al, a, p. 6).

Palaeozoic series (Cambrian at base). 

Azoic series:

Algonkian.

Urberg.
26 GEOLOGIC TIME CLASSIFICATION

K. A. von Zittel, 191O (Grundztige der Paleeontologle, Abt. 1, pp. 5-6).

Palaeozoic group: 

* * *

Cambrian system (Upper, Middle, and Lower) at base. 

Archean (or Azoic) group: 

Primitive slate system. 

Gneiss system.

E. Kayser, 1911 (Lehrbnch der Geologic, p. 12).

Eozoic or Proterozoic group (Algonkian). 

Azoic or Archeozoic group (Archean).

K. Kayser, 1912 (Lehrbnch der allgemeinen Geologic, 4th ed., p. 138).

Eozoic or Archseozoic rock group (Algonkian). 

Azoic or Archean rock group (Urgebirge).

H. Credner, 1912 (Elemente der Geologic, llth revised ed., pp. 360-380)..

Proterozoic group:

Algonkian complex. 

Azoic or Archean group.

K. A. von Zittel, 1921 (Grundzilge der Palceontologie, Abt. 1, chart opp. 

P. 8).

Palaeozoic group (Cambrian at base).

Archseozoic = Eozoic group (pre-Cambrian, Proterozoic, Algonkian).

Azoic group = Archtean, Urgebirge.

J. Stlny, 1922 (Technlsehe Geologic, pp. 564-559).

Cambrian (Upper, Middle, and Lower). 

Algonkian (Eozoic, Archeozoic). 

Archaean (Urgebirge).

C. Schnchert, 1924 (Textbook of geology, 2d ed., vol. 2).

[See quotation under " Eozoto era"]

" Azoic " is derived from the Greek a- (without) and f0017 (life) and 

means having no trace of life. The time covered by it in its different 

usages is included in the Proterozoic era by the United States 

Geological Survey. In its earlier and in some of its later usages 

the term was applied to all pre-Paleozoic time. In other later 

usages it has been applied (1) to all pre-Potsdam time, (2) to the 

Huronian epoch and the Archean period, (3) to the Archean period 

only, and (4) to a hypothetical interval preceding all known rocks.

"COLLQZOIC AGE"

A. C. Lane, 1917 (Am. Jour. Set., 4th ser., vol. 43, p. 46, pi. 1).

For a time the early ocean might remain as acid as iron chloride is, and 

in such an acid or fresh ocean no animals would tend to secrete hard parts 

until the concentration of salts reached and passed the optimum for some 

cell activity, when the extra lime would be secreted as a pathological reac-
THE ERA TERMS 27

tion. They would be jelly-like (colloidal) and this would be a Collozoic age,8 

but for that very reason might easily and rapidly evolve in various directions.

In the chart forming Plate I of the volume cited above the following subdivisions are given:

Collozoic:

Animikian series.

Algoman revolution (granite and gneiss).

Huronian system.

Laurentian revolution (granite and gneiss).

Grenville series. 

Azoic:

Keewatin series.

Coutchiching series.

" Collozoic" is derived from the Greek words xoXXa (glue or 

gelatine) and fcoi? (life) and means protoplasmic life. The time 

covered by it is included in the Proterozoic era by the United States 

Geological Survey.

" EOBIOTIC ERA " AND " EOMORPHIC ERA "

G. H. Hitchcock, 1888 (Interimt. Gong. Geol., American committee reports, 

Philadelphia, p. A14$ P. Frazer, reporter).

Prof. Hitchcock suggests Eobiotic in place of Eozoic, as it is better to use the 

Greek word signifying animal life; and also because of a previous use of 

Eozoic. He thinks it would be better still to say Eomorphic in allusion to 

the fact that the Huronian beds are almost the first which show the existence 

of sedimentation.

Eo is derived from the Greek qws (dawn); biotic from /3twru6s 

(pertaining to life); and morphic from noppy (form). The time 

covered by these terms is included in the Proterozoic era by the 

United States Geological Survey.

" EOZOIC ERA "

J. W. Dawson, 1808 (Acadian greologry, 2d ed., p. 658) and 1891 (4tli ed., 

p. 658).

The Huronian and Laurentian periods. The formations last described carry 

us far back through the long ages of the earth's geological history to the beginning of the Palaeozoic period; but still older rocks, indicating still earlier 

periods, are known to geologists. These, until lately, were regarded as azoic, 

or destitute of remains of life; but the discovery of Eozoon Canadense now entitles them to the name Eozoic, or those that indicate the morning of tnat great 

creative day in which the lower forms of animal life were introduced upon our 

planet. * * *

6 Collozoic is a synonym for Huronian, or Eozoic, nearly, denoting the stratified rocks 

before the Cambrian in which the existence of life may. be inferred, and connoting the 

fi-upposition that the absence of ordinary fossil remains in them Is due to the fact that 

the animals had not yet developed hard parts,, (for the reason as I have supposed that 

the concentration of base had not passed the physiologic optimum, and the ocean water 

was soft or acid,) and were yet colloidal or jelly-like.

1146 25 3
28 GEOLOGIC TIME CLASSIFICATION

B. von Cotta, 1872 (Die Geologic der Gegenwart dargestellt -and fcelenchtet, 

pp. 80-98).

Cambrian. 

Eozoic:

Crystalline schists (including, in Canada, quartzite and talc slates, 

Laurentian rocks, and crystalline schists interbedded with Eozoonbearing granular limestone and serpentine).

J. D. Dana, 1875 and 1880 (Manual of geology, 2d ed., pp. 138-139; 3d ed., 

pp. 14O-160).

Paleozoic time. 

Archaean time:

Eozoic age.

Azoic age.

[See quotation under " Aeoio era "]

J. Le Ctmte, 1882 (Elements of geology, pp. 280, 281, 282) and 1891 (Elements of geology, pp. 282, 283).

Archaean or Eozoic 8 era: 

Huronian. 

Laurentian.

J. W. Dawsoii, 1888 (Iiiternat. Cong. Geol., American committee reports, 

Philadelphia, p. AG; P. Frazer, reporter).

Sir J. W. Dawson prefers the term "Eozoic" [to Archean], and would have 

it include all the Pre-Cambrian strata.

A. Winchell, 1889 (Geological studies- or elements of geology, 3d ed., pp. 

361-369).

Eozoic Great System. Eozoic, unlike Azoic (formerly employed), can never 

become inapplicable through the progress of discovery. The rocks next before 

the Eozoic were perhaps strata now melted away. The divisions of the Great 

System:

Keweenian system.

Huronian system.

Laurentian system.

J. Walther, 1910 (Lehrbuch der Geologie von Dentschland, p. 40).

Eozoic era: 

Cambrian. 

Algonkian. 

Crystalline schists.

E. Kayser, 1911 (Lehrbuch der Geologie, p. 12).

Eozoic or Proterozoic group (Algonkian). 

Azoic or Archeozoic group (Archean).

E. Kayser, 1912 (Lehrbnch der allgemeinen Geologie, 4th ed., p. 138).

. Eozoic or Archseozoic rock group (Algonkian). 

Azoic or Archean rock group (Urgebirge).

8 Dawn of animal life.
THE EEA TERMS 29

A. Tornquist, 1913 (Grundziige der geologlschen Formations- nnd GcbSrgskunde, p. 41).

Upper Eozoic:

Jotnian formation.

Jatulian formation. 

Middle Eozoic:

Kavelian formation.

Lodogian and Bottnian formations. 

Lower Eozoic (Azoic) :

Granite, gneiss, and crystalline schists.

J. Park, 1914 (Textbook of geology, pp. 306-307).

Eozoic' era. This group includes all the rocks of pre-Cambrian age that 

reach the surface or have been laid bare by denudation. * * *

In the Lake Superior region of North America, where the Eozoic has' fts"- 

greatest and perhaps most typical development, the succession recognized by 

American geologists is as follows, the name Archaean being restricted to the 

lower highly crystalline complex of altered rocks: 

Algonkian:

(1) Keweenawan (Copper-bearing series). . Unconformity.

(2) Huronian:

Upper.

Unconformity.

Middle:

Unconformity.

Lower.

Unconformity. 

Archaean:

(3) Keewatin. 

Eruptive unconformity.

(4) Laurentian.

A. Grabam, 1921 (Textbook of geology, p. 2O).

[See quotation under Proterozoic era] 

C. Schuchert, 1924 (Textbook of geology, 3d ed., vol. 2).

Proterozoic:

Killarney revolution (granites). 

Algonkian:

Keweenawan series. 

Huronian series. 

Timiskamian:

Algoman revolution (granites).

Sudburian-Dor6an series. (The pre-Huronian position of theseformations is not yet definitely established, according to 

Leith.) 

Archeozoic or Archean:

Laurentian revolution (granites). 

Loganian:

Keewatin-Coutchiching series.

7 Gr. Bos=thc dawn, and zoe=llfe.
30 GEOLOGIC TIME CLASSIFICATION

Classification hypothetic; no known rock record. 

Eozoic. (Dawn of unicellular life.) 

Azoic. (Lifeless.) Includes oceanic era, lithic era, and astral era

of Dana. 

Cosmic or astronomic time.

The time covered by " Eozoic era," as thus variously used, is included in the Proterozoic era by the United States Geological 

Survey. As originally defined " Eozoic " was applied to all prePaleozoic time. In its later usages it has been applied (1) to all 

Cambrian and pre-Paleozoic time, (2) to pre-Paleozoic time only, 

(3) to the Algonkian period only, (4) to Huronian and Laurentian 

(including Keewatin) time, (5) to a part only of the Algonkian 

period, and (6) to a hypothetical pre-Keewatin interval.

J. Phillips, 1855 (Manual of geology, pp. 76-89).

In the following description of strata, we shall retain the general titles of 

Primary, Secondary, and Tertiary Strata, combining with them a parallel set 

of names Hypozoic, Palaeozoic, Mesozoic, and Cainozoic strata and divide 

them into several systems and formations according to certain properties, or 

in agreement with their elective associations. [Page 76.]

Hypozoic Strata: These strata, which have the aspect of being derived from 

decomposed granitic rocks, with several subordinate and associated strata all 

devoid of organic remains, constitute, according to the concurring testimony 

of geological observers, the_ lowest group of the whole series of Neptunian 

deposits. [Page 80.]

The limestone associated with the truly ancient gneiss and mica slate is 

destitute of organic remains. The gneiss and mica system may therefore be 

considered as hypozoic, or beneath the strata which contain reliquiae of 

palwozoic life. [Page 87.] There are strong grounds for believing that what 

we now call liypozoic strata were really formed when no organic life was 

manifested on the globe. [Page 88.]

[In table on page 624 the pre-Paleozoic is called Prozoic? period.]

Hypozoic: A term proposed in the former edition of this work for the 

lowest primary strata, such as gneiss, mica schist, &c., found below all those 

which contain organic remains, viro, below [or under], fwij, life=Azoic (Mur.J. 

[Page 655.]

The time covered by the term " Hypozoic" is included in the 

Proterozoic era by the United States Geological Survey. The term 

was probably first published by J. Phillips in 1840, in the Penny 

Cyclopaedia.

" PROGONOZOIC " AND " PROGONIC "

J. J. Sederholm, 1914 (Cong. g£ol. intermit., 12th sess., Toronto, Compt.- 

rend., pp. 383-384).

POSSIBILITY OF THE USE OF GROUP NAMES WITH THEORETICAL MEANINGS

As long as it is impossible to correlate the Pre-Cambrian series in different 

parts of the world with approximate certainty, the introduction of terms of 

group rank and world-wide significance for divisions of this complex is more
THE EBA TEEMS 31

a theoretical than a practical question. Obviously, the name Algonkian, which 

is analogous in form to the names applied to systems, cannot always continue 

to be applied to a division of group rank. The Algonkian and Archaean are, 

no doubt, at least of the same magnitude as the younger groups, and may 

possibly even comprise several groups. Various names with theoretical meanings have been proposed, such as Eparchcean, Proterozoic, Archeozoic, Eozoic, 

Agnotozoic, etc. Chamberlin and Salisbury regard Archeozoic as an older 

group than the Proterozoic, while Van Hise and Leith, in their important 

work, " The Pre-Cambrian Geology of North America," the vade-mecum of 

every Pre-Cambrian geologist, recognize only one pre-Palseozoic group, the 

Proterozoic. If we add to the Palaeozoic, which already means something old, 

an older ProterozoiOs and an even more ancient Archeozoic, the form of this 

terminology, with almost as many comparatives as ultra-hyper-super-dreadnought, seems to violate the principles of good word-building. Why should the 

Pre-Cambrian be added as appendices to the classification of the younger 

groups, when they form a realm of no less chronological importance?

Moreover, the " zoic " character is proved in few cases, which makes a general use of most of these words difficiilt. This reason induced Irving to propose the word Agnotozoic, which has lately been adopted also by Haug. But, 

as I have pointed out before, this word implies a contradictio in adjecto, the 

organisms being either wanting, in which case the group is not zoic, or existing, 

in which case the term agnotus is not justified. I have tried to eliminate these 

difficulties by proposing the term Progonozoic, the group of the ancestral 

organisms; this can also be used in the modified form Progonic. However, I 

feel most inclined to propose the introduction of the latter term, not as a designation of the youngest Pre-Cambrian, but as an equivalent for Pre-Cambrian, 

that would mean a declaration of independence on the part of Pre-Cambrian 

geology against the geology of the younger groups. This seems justified by 

the fact that such different methods are employed in the investigation of these 

respective fields of inquiry. The Progonic could in such case be further subdivided, as I have proposed before, into Neo-Progonic, Meso-Progonic and 

Archeo-Progonic.

But these proposals are new and have not yet undergone the ordeal of criticism, hence it would be unwise to propose now the adoption of any such term. 

For my part I think it, would be better to leave to the future the adoption of any 

theoretical names for the different Pre-Cambrian groups, or for the whole of the 

Pre-Cambrian. But if the Congress should prefer to take any action on this 

point, I hope that it will consider the terms which I have proposed.

No action was taken by the Congress. The United States Geological Survey's term Proterozoic era corresponds to the time interval 

for which Sederholm suggested the term " Progonozoic " or 

" Progonic.'''

PROTEROZOIC ERA

S. F. Emmons. 1888 (letter to Persifor Fru/.er, dated May 25, 1SS7, published in Intern at. Geol. Cong., American committee reports, Philadelphia, pp. A58-AOO).

With Irving, Chamberlin, and Walcott I think that the Huronian, Keweenawian, and Grand Canon series, and whatever other clastic formations occur 

between the Cambrian and the Archean, should be included in one grand group 

of equivalent rank with the Archean, Paleozoic, etc., and since the term 

Paleozoic has by long use become so indelibly impressed upon geological
32 GEOLOGIC TIME CLASSIFICATION

classification that it would be difficult to give it up, I would suggest that the 

name Proterozoic should be given to this new group, signifying that its life 

was earlier than that of the other groups, without committing ourselves as 

yet to the statement that it was the first to appear upon the earth. [Page 59.]

S. F. Emmons, 1888 (Internat. Geol. Couft'., American committee reports, 

Philadelphia, p. 13; P. Frazer, reporter).

Dr. [S. F.] Emmons suggests that the beds referred to by Irving [those 

between the Cambrian and the Archean], be grouped together as " Proterozoic.''

This name seems preferable to Agnotozoic, both because to select our ignorance of a terrane as a means of identifying it is to select that which all the 

terranes have most certainly in common; and also because the term Proterozoic is elastic and better adapted to serve as a temporary scaffolding until 

more of the true history of the earlier rocks becomes known. But Eozoic or 

Eobiotic seems better than either.

[On page 42 of the foregoing report, under the " Conclusions " of the Congress, it was provided that the name for the division between the Laurentian 

and the Cambrian should be one of the following: " Eozoic, Proterozoic, Eobiotic, Eomorphic, Agnotozoic, etc."]

C. R. Van Hlse, 1892 (IT. S. Geol. Survey Bnll. 86, pp. 492-493) and 1896 (TJ. S. 

Geol. Survey Sixteenth Ann. Kept., pt. 1, pp. 701-702).

It is, however, necessary to recognize that the carrying downward of the 

term Cambrian to cover not only the great thicknesses of rocks which are 

now included in it, but all pre-Cambrian elastics, will probably make the 

Cambrian as great as or greater than all the subsequent periods put together. 

That this is inadvisable is plain, and the clastic rock masses below thel 

Olenellus fauna are so enormous that the proposal to introduce a general 

term like Agnotozoic as the equivalent of Paleozoic, Mesozoic, and Cenozoic, 

to cover this great group, is a conservative one. Irving foresaw that the 

term would be objected to, because sooner or later the life will become to a 

greater or less degree known, and he suggested as an alternative for Agnotozoic, Eparchean, in contradistinction to Archean, which was reserved by him 

to cover the Basement Complex. As the character of the life of this group 

is already beginning to be known, it seems to me that the term Proterozoic, 

considered for the place by Irving (7th Ann. Kept. U. S. G. S. for 1885-86, p. 

454), but rejected, is preferable to either Agnotozoic or Eparchean.

In a conference of the members of the United States Geological Survey, 

called by the Director at Washington (Tenth Ann. Rept. U. S. Geol. Surv., for 

1888-89, Report of the Director, p. 66) these terms were discussed with reference to atlas-sheet mapping, although there was no question on the part of 

anyone as to the necessity for some such term. Recognizing the impracticability of the certain correlation with one another of the one or more preCambrian clastic series which occur in the various regions, and recognizing 

the fact that for use in mapping a uniform plan must be adopted, som6 one 

suggested that a term of the same class as Cambrian, Silurian, and Devonian 

should be selected for rocks here included, and to occupy this place the term 

Algonkian was proposed and accepted. The proposed general scheme of 

classification for the lower part of the geological column is as follows: 

Paleozoic:

Carboniferous.

Devonian.

Silurian.

Cambrian.
THE ERA TERMS 33

\

Proterozoic:

Algonkian. 

Archean: 

Archean.

A. Gelkie, 1893 (Textbook of geology, 3d ed., pp. 680, 684) and 1003 (Textbook of geology, 4th ed., pp. 867-868).

The Geological Record is classified into five main divisions: (1) Pre-Cambrian, also called Archaean, Azoic (lifeless), Bozoic (dawn of life), or Proterozoic (earliest life) ; (2) Palaeozoic (ancient life) or Primary. [Page 680.]

Various terms have been proposed for this complex assemblage of rocks, 

such as Primitive, Proterozoic, Azoic, Agnotozoic or Archaean. * * * To 

prove that any region of crystalline schists may be " Primitive," " Azoic," or 

" Archaean " we must first find these rocks overlain by the oldest fossiliferous 

formations. Where no evidence of this kind is available, the use of precise 

terms, which are meant to denote a particular geological era, is undesirable. 

There seems good reason to believe that the asserted " Archaean " age of many 

tracts of schistose and granitoid rocks rests on no better basis than mere 

supposition, and that as the study of regional metamorphism is extended, the 

so-called "Archaean" areas will be proportionately contracted. Several distinct systems of mineral masses can be shown in some regions to exist beneath 

the base of the Palaeozoic formations, differing so greatly in petrological characters, in tectonic relations, and probably also in mode of formation, that they 

cannot, without a very unnatural union, be arranged in one definite stratigraphical series. For the present it seems to me least objectionable to adopt 

some vague general term which nevertheless expresses the only homotaxial 

relation about which there can be no doubt. For this purpose the designation 

" Pre-Cambrian," already in use, seems suitable. The rocks which I would 

embrace under this epithet may include a number of separate systems or 

formations which have little or nothing in common, save the fact that they 

are all older than the base of the Cambrian rocks. Until our knowledge of 

these ancient masses is much more extensive and precise than it is at present 

I think it would be of advantage to avoid the adoption of any general 

terminology that would involve assumptions as to their definite place and 

sequence in the geological record, their mode of origin, their relation to the 

history of plant and animal life, or their identification in different countries. 

tPage 684.]

T. C. Chamberliii and R. D. Salisbury, 1O06 (Textbook of geology, pp. 137- 

138, 162).

[See quotation under "Archeozoic era"]

A. P. Coleman, 1906 (Jonr. Geology, vol. 14, pp. 62-63).

Now that it has been proved that water-formed sediments, sometimes in 

large amounts, belong to the basal complex and are older than the Laurentian 

eruptives in the Great Lakes region, where these rocks have been most 

widely studied, should not the western geologists revise their point of view 

and drop either the " Proterozoic" or the "Azoic," or both, from their 

nomenclature?

C. R. Van Hisc, 19O8 (Geol. Soc. America Bull., vol. 19, pp. 16-19, 26-28).

The wisdom of the conclusions of the geologists who selected the terms 

Algonkian and Archean for the two major divisions of the pre-Cambrian has 

since been confirmed by considerations which have developed since the adoption 

of the terms. As has' been seen, when the terms Agnotozoic and Proterozoic
34 GEOLOGIC TIME CLASSIFICATION

were proposed by Irving in the sense now conveyed by Algonkian, it was known 

that the rocks there placed contained positive evidence of life, but it was 

supposed that the inferior group of the pre-Cambrian contained no evidence of 

the existence of life. It has since been ascertained that in the Archean all 

the evidences of life shown by the Algonkian exist, with the exception of the 

few imperfect fossils which are now known in the latter group. Thus there 

arises, if zoic terms are to be used, the necessity for the introduction of 

another zoic term for the Archean (and, as has been seen, Archeozoic has been 

suggested) ; or, if this be not done, it is necessary to extend one zoic term to 

cover all of the pre-Cambrian rocks to the base of the earth formations.

The objection to a dual zoic division for the pre-Cambrian rocks is that their 

life is not known to be different. When we say Paleozoic and Mesozoic, we 

understand the terms to indicate a great known fauual difference. We think 

not so much of the rocks, their lithological contrasts and the differences of the 

physical conditions of their formation, as of the life contrast. The rocks which 

contain a Paleozoic fauna are Paleozoic; those which contain a Mesozoic 

fauna are Mesozoic. The separation of the rocks of the pre-Cambrian into 

Proterozoic and Archeozoic premises a fundamental difference in the fauna of 

the two eras for which there is no evidence. In short, the zoic division is an 

unverified assumption which the future may or may not justify.

On the other hand, this objection can.not be raised against the terms Algonkian and Archean. Their use is justified by the facts in the field, which 

inevitably lead to the dual classification of the pre-Cambrian formations on a 

physical basis. The above gives sufficient reason for continuing to adhere to 

them.

However, the great physical contrasts of the Archean and Algonkian and 

the profound unconformity separating the two, marking one of the greatest 

physical revolutions of the world, doubtless; does correspond to great life 

changes. There has been a tendency to place more and more emphasis on the 

physical breaks between the Paleozoic and the Mesozoic, and the Mesozoic and 

the Cenozoic, and too regard the differences of life of these eras as largely due 

to physical revolutions; consequently we should expect the great physical 

revolution separating the Archean and Algonkian to have resulted in important 

life changes; and while I shall use the terms Algonkian and Archean because 

they correspond by definition to the physical facts on which the dual division 

of the pre-Cambrian is made, if others prefer the terms Proterozoic and Archeozoic, I shall not quarrel with them, after having pointed out that fossil 

evidence can not be given to justify this life classification, and that the use of 

these terms is based on faith in future progress rather than on achieved results.

The Archean is a series dominantly composed of igneous rocks, largely 

volcanic and for extensive areas probably submarine. Sediments are subordinate. The Algonkian is a series of rocks which is mainly sedimentary. 

Volcanic rocks are subordinate. * * *

To the dual division of the pre-Cambrian emphasized it has been objected 

that it can not everywhere be applied. To this objection instant agreement 

is made. It may be equally well said that the Paleozoic can not everywhere 

be separated from the pre-Paleozoic. * * *

In the classification of the Algonkian presented by Willis for China he 

introduces into the nomenclature of -the pre-Cambrian the words " NeoProterozoic" and " Eo-Proterozoic." I wish to question this suggested practice, since I can see no philosophical basis on which such a division can be 

made; nor do the facts as described seem to me to require any such division. 

Indeed, no adeauate reason is advanced or even suggested for the selection of
THE EEA TERMS 35

one unconformity rather than another of those in the Algonkian as the basis 

of the division. If the use of these terms results in the practice becoming 

at all general, it will be believed by the students beginning geology and soon 

oy the geologists themselves that Eo- and Neo-Algonkian or Proterozoic in 

one region correspond with those of the other, and this would be certain to 

lead to error. I know of no region in which emphasis on one break in .the 

Algonkian more than others is justified, and if this be not the case, the division is purely theoretical rather than factitious. In short, I foresee confusion 

and no advantage in the arbitrary introdtiction of the two proposed terms which 

have no philosophical basis or definite facts in the field which justify them; 

for their use amounts to .the introduction of zoic terms for the divisions of the 

Proterozoic, and thus the objection made (pages 16-17) to Proterozoic and 

Archeozoic for the major divisions of the pre-Cambrian applies with much 

greater force to Eo and Neo divisions of the Proterozoic.

CONCLUDING STATEMENT

In view of the foregoing considerations I present the following classification 

of the pre-Cambrian as representative of the best current views:

I One or more series in various geological provinces separated 

gon lan j ^y unconformities. To' this series local names are applicable. 

Unconformity.

(Keewatin. 

Archean__| Eruptive unconformity.

I Laurentian.

Whether the physical contrasts which separate the Archean and Algonkian 

are such as to justify the belief that corresponding to them are two life groups 

which may be called the Proterozoic and Archeozoic, I leave the future to determine, and adhere to the terms which have arisen as a result of inductive 

studies of pre-Cambrian geology. ^

Those who decline to accept a dual zoic division of the pre-Cambrian may 

still favor a single zoic term to comprise the two groups. Thus Emile Haug, 

professor of geology in the University of Paris, in his textbook on geology, 

which has just appeared, so uses the term Agnotozoic. But if the consensus 

of opinion turns in this direction, it would be better, I think, to use Proterozoic 

rather than Agnotozoic as the life term. If the term Proterozoic be decided 

on for all pre-Cambrian rocks, for the two major divisions of the Proterozoic, 

the terms Algonkian and Archean clearly have precedence and right of way 

from every point of view, and this Haug recognized by making them the major 

divisions of his Agnotozoic. This clearly emphasized the standing these terms 

have gained and to which their clear definitions and general applicability 

entitle them.

It has also been suggested, but, so far as I know, never in print, that the 

term Proterozoic be extended to the bottom of the column, and that the two 

divisions of the Proterozoic thus defined be Earlier and Later. This proposal 

would amount to an indirect dual division of the pre-Cambrian emphasized in 

this paper. Such usages would simply introduce other terms for the major 

divisions of the pre-Cambrian having a meaning equivalent to that of Archean 

and Algonkian. The only result of the acceptance of the proposals, so far as I 

can see, would be the avoidance of these terms. The ideas of those who as a y,-»

result of many years' work have formulated the fundamental principles upon 

which the division of the pre-Cambrian is based would be taken, but their

1146 25 4

 

, 1-f
36 GEOLOGIC TIME CLASSIFICATION

terms rejected and other terms introduced in their stead, which, as terms / 

merely, are very objectionable.

In closing I wish to express my strong belief that the dual division of the 

pre-Cambrian into two great groups of rocks seems now as firmly established 

as the division between any other two groups; indeed, the major contrasts 

between the Archean and Algonkian, in the character of the rocks and the 

earth conditions which they represent, are probably greater than between any ./ 

other two. The only other two which have anything like such contrasts are <{ 

the Algonkian and the Paleozoic, and this difference is not in the nature of 

the materials or the physical conditions obtaining during their depositions, but A 

in the absence of definitely recognized life forms in the older and the presence 

of a highly developed fauna in the newer. Also the division of the Archean 

into Laurentian and Keewatin is firmly established, and Archean is entitled to 

a group place in the geological column.

It is also clear that the Algonkian should have the place of a group in the 

geological column.

C. R. Van Hise, 19O9 (Jour. GeologT, vol. 17, pp. 121-122). (Discussing F. D. 

Adams's paper in same journal.)

I fully discussed the major classification of the pre-Cambrian in my presidential address before the Geological Society a year ago, and gave reasons for 

the primary divisions of the pre-Cambrian into the Archean and Algonkian. 

In that address I gave objections to a zoic classification, similar to but not ^ 

identical with that which Dr. Adams adheres to. His proposed major classification is eo-proterozoic, meso-proterozoic, and neo-proterozoic. These terms 

imply that the pre-Cambrian had three distinctive life periods, an eo, a meso. 

and a neo. This may be the case, but until fossils are found in the preCarnbrian in sufficient abundance to justify a zoic classification, there can be 

no sufficient warrant for proposing that the major divisions of the pre-Cambrian be made upon a zoic basis.

C. R. Van Hise and <?. K. Leith, 1009 (IT. S. Geol. Survey Bull. 36O, pp. 19-21).

The United States Geological Survey has since 1889 recognized a dual 

division of the pre-Cambrian into Archean and Algonkian. The senior author 

has favored the term Proterozoic (earlier life) as the era equivalent to the 

Algonkian. His proposed classification of the pre-Cambrian as given in the 

first edition of this bulletin (Bulletin No. 86) and repeated in the Sixteenth 

Annual Report of the United States Geological Survey, except that "Agnotozoic " is omitted, reads as follows:

Era or group. Period or system. 

Paleozoic______________________Cambrian and others 

Agnotozoic or Proterozoic__________________Algonkian 

Archeain________________________._-___Archean

When it was proposed to use "Agnotozoic " or Proterozoic as the equivalent 

of Algonkian it was not known that the Archean contained sediments.

A few fossils had been found in Algonkian rocks. Thus there was a certain 

basis for using the term Proterozoic as equivalent to Algonkian. But carbonaceous shales, limestones, and iron formation rocks extend to the very 

bottom of the known geological column, suggesting existence of life in the 

earliest rocks. However, the life remains of the pre-Cambrian are far too 

scant to warrant any attempt at subdivision of the pre-Cambrian on the 

" zoic" basis. The major classification of the pre-Cambrian has been made 

upon a physical and not a paleontological basis. For this reason, therefore.

i
THE ERA TERMS 37

the writers prefer to use the terms Archean and Algonkian, without separate 

" zoic " equivalents. 

Our proposed classification of the pre-Cambrian is as follows:

One or more series in various geological provinces,

Algonkian _- separated by unconformities. To these series local names

are applicable. 

Unconformity.

Keewatin. 

Archean___- Eruptive unconformity. 

Laurentian.

Chamberlin and Salisbury, in their textbook of geology, have proposed 

the divisions Proterozoic and Archeozoic for the rocks which we here call 

Algonkian and Archean, but such " zoic " division is not founded on evidence 

furnished by fossils and represents a hope of the future rather than achieved 

results. It seems probable from the great physical contrasts in the Archean 

and Algonkian that this proposed " zoic" division would be justified if we 

could know the life of these two eras, though this is yet a speculative belief 

based upon general principles.

iEmile Hang, realizing the difficulty of dividing the pre-Cambrian on the 

" zoic " basis, has proposed to use only a single " zoic " term for all of the 

pre-Cambrian rocks. For this term he has chosen the word "Agnotozoic," 

which he separates into Archean and Algonkian. If Professor Haug's plan 

be followed, it seems to us that the preferable term for this place is Proterozoic rather than "Agnotozoic."

However, since the. proper choice of " zoic" terms can be made only by 

future development of knowledge, and there is no consensus of opinion on 

the matter, we shall avoid introducing the " zoic" nomenclature into this 

discussion, confining ourselves, as has been said, for the major subdivisions 

of the pre-Cambrian to.the terms Algonkiau and Archean, the forms of which 

correspond with the physical basis upon which the separation is actually made.

F. D. Adams, 1909 (Jour. Geology, vol. 17, p. 115).

Pre-Cambrian:

Neo-Proterozoic:

Keweenawau-Athabasca series.

Upper Huronian or Animikie-Nastapoka series. 

Meso-Proterozoic:

Middle Huronian.

Lower Huronian. 

Eo-Proterozoic:

Keewatin series.

Laurentian system.

E. Knyser, 1911 (Lehrbmch rter Geologic, p. 12).

Eozoic or Proterozoic group (Algonkian). 

Azoic or Archeozoic group (Archean).

H. Credner, 1912 (Elemente den- Geologic, llth revised ed., pp. 36O-38O>.

Palaeozoic group (Cambrian at base). 

Proterozoic group:

Algonkian complex. 

Azoic or Archean group.
38 GEOLOGIC TIME CLASSIFICATION

T. C. Chamberlin, 1914 (Congr. g-gol. internal., 12th seas., Toronto, Com.pt.- 

reiid., p. 425).

T. C. Chamberlin (Chicago), stated briefly the grounds on which the PreCambrian is divided into Proterozoic and Archeozoic, to which allusion had 

been made. A portion of the Pre-Cambrian sediments present the products of 

mature disintegration, while the earlier portions are usually characterized 

by partial or immature disintegration. The former are best typified by the 

great beds of quartzite, that imply the complete disintegration of large quantities of quartz-bearing rock and the subsequent assortment and reduction of 

its quartz particles. The shales and schists imply the same process, but in 

their metamorphosed condition they are less easily and safely distinguished 

from pyroclastic and other material of different origin. Mature disintegration 

implies some restraining agency that held the rock in place while the slow 

weathering process completed its work; otherwise the products of incomplete 

disintegration would have mingled with quartz and given an arkose or equivalent product. In the later ages the chief restraining agency was the 

mantle of vegetation, so that this view favours the existence of a vegetal 

covering of the land as far back as great terranes of quartzite occur. By 

hypothesis the classification thus comes to have a semiorganic basis; but this 

is not essential to the classification which is based on the dominant processes 

attending the sedimentation. The Proterozoic is thus made to include terranes that bear great quartzite formations. The earlier formations not so 

characterized are grouped into the Archeozoic.

W. G. Miller and C. W. Knlgltt, 1914 (Canada Bar. Mines Kept., vol. 22, 

pt. 2, pp. 3, 125).

The crystalline limestones and other Grenville sediments in southeastern 

Ontario constitute a series of great thickness, and are found to be of preLaurentian age. The great volume of the sediments older than the Laureritian 

appears not to justify the separation of the Laurentian. and earlier rocks from 

those of later pre-Cambrian age. In other words, a dual subdivision of the preCambrian into an upper characteristically sedimentary group above the 

Laureutian and a lower igneous complex, including the Grenville, is not 

logical. Hence the writers do not make use of the terms Algonkian and 

Archean, or Proterozoic and Archeozoic, employed by many authors. * * *

In the author's opinion there appears to be no logical reason for a dual 

subdivision of the pre-Cambrian into Archean and Algqnkian, or Archeozoic 

and Proterozoic, either on the basis of proportion of sediments or on that of 

life development. As regards metamorphism, there is a normal progression 

downward from that of the younger to the older groups, Fig. 60 [photograph]. 

The Temiskamian rocks are more highly metamorphosed than are the Animikean, and less metamorphosed than the Grenville. Moreover, the thickness 

of the pre-Laurentian sediments is great.

C. Seliijcliert and J. Ban-ell, 1914 (Am. Jour. Sci., 4tli ser., vol. 38, pp. 18-19).

To >note in descending order certain of the problems presented in'the present 

table: the attention may be turned first to the use of the names Proterozoic and 

Archeozoic, with their popular rendition as the Age of Primitive Marine Invertebrates and the Age of Unicellular Life. The reason for this usage is the 

desire for conformity with the system of classification used for the later geologic ages. The Proterozoic, however, is broken here into an early and a. late 

division, separated by a period of profound diastrophism, following a use
THE EEA TEEMS 39

made by Coleman in the Dana Memorial Lectures on the Silliman Foundation, 

given' at Yale University in December, 1913, and to be published during 1914 

by the Yale University Press. The limitations of these divisions are thus 

structural rather than biologic, but this is true in a measure also of the later 

eras, as argued by Chamberlin.8 As the names of successive great divisions 

of earth history, to be applied in widely separated regions, these terms Archeozoic and Proterozoic imply a less definite correlation than the more localized 

terms of Paleolaurentian, Neolaurentian, and Algonkian, used here for the 

Canadian Shield. For this reason these " zoic" names appear to have real 

value, as well as for the fact that by their use harmony is maintained through 

the whole scheme of geologic chronology. The nature of the faunas of the Proterozoic and Archeozoic is unknown, as is also the time in earth history when 

the Metazoa first rose to dominance over the Protozoa. The dividing line 

therefore cannot be drawn from biologic evidence; but even if a fair knowledge 

of the life of these times was possessed, it is probable that it would be found 

gradational to a considerable degree, and these broad names as here used could 

still apply without doing violence to the biotas of the Paleo and Neolaurentian.

W. G. Miller and C. W. Knight, 1015 (.Tour. Geology, vol. 23, p». 5O1-593).

A dual subdivision ,of the pre-Cambrian, as shown in Table II, is employed 

by many authors. It is purely arbitrary, and is now' known to be based 

on a misconception as to the relations of the rocks. It was believed, or 

assumed, that the greatest unconformity within the pre-Cambrian is that 

at the base of the "Lower Huronian," as the term is used by the U. S. Geological Survey. Such, however, has not proved to be the case. There is no 

proof that the unconformity at the base of the Timiskamian is of less magnitude than that at the base of the Animikean, of the author's classification, 

or vice versa. According to Coleman, the various sedimentary series of the 

Timiskamian, his Sudbury series, where most fully developed, appear to have 

an approximate aggregate thickness of 29,000 feet. Elsewhere these sediments are also known to have great thickness.

The term "Eparchean Interval," concerning which there has been so much 

discussion in the past, should now be discarded. The so-called Lower and 

Middle Huronian rocks of the classic area of Lake Huron lie above and not 

beneath it. There are now known to be two great " intervals" in the preCambrian, that beneath our Animikean and that beneath our Timiskamian, 

and not merely one as has been assumed.

Moreover, a dual subdivision of the pre-Cambrian cannot be justified on 

the basis of differences in metamorphism or other characteristics of the rocks. 

Normally there is a gradual increase in degree of metamorphism from the 

youngest to the oldest. In the province of Ontario the Animikean rocks are 

only slightly metamorphosed or disturbed, while the Timiskamian are disturbed and frequently rendered schistose, and the Loganian are highly metamorphosed.

Sediments, Grenville, occur in great volume in the Loganian. Hence the 

" Archean " cannot be said to be essentially igneous, as assumed at one time. 

Moreover, ordinary stratigraphic methods, which have been cited as a test 

as to whether certain groups of rocks should be classed as Archean or otherwise, can be applied in studying the Grenville. This has been shown by the 

author's work in southeastern Ontario.

8 Van Hise and Leith, Pre-C'ambrian Geology of North America, Bull. 360, U. S. Geol. 

Surv., 1909, p. 21.
40 GEOLOGIC TIME CLASSIFICATION

Briefly, it may be said that the discovery of the true relations of the 

Timiskamian destroys the argument for a dual classification of the preCambrian.

[They give (p. 598) the following classification for Ontario:]

Pre-Cambrian of Ontario: f 

Keweenawan epoch (deposition). 

Animikean epoch (deposition). 

Algoman epoch (intrusive granites). 

Timiskamian epoch (deposition).

Laurentian (granite intrusions). \ 

Loganian. r 

Grenville epoch (deposition). - Keewatin (largely basic volcanic rocks).

A. P. Coleman, 1915 (Problems of American geology, Yale Univ. Pub., p>. 90).

Late Proterozoic: <, 

Keweenawan. 

Upper Huronian 1 

Lower Huronian JTypical Huronian.

Early Proterozoic:

Laurentian granite and gneiss.

Sudburian=Temiscaming, Pontiac, etc. 

Archseozoic: ,

Granite eruptive through lower series.

Keewatin and Grenville.

C. Schuchert, 1915 (Textbook of geology, pp. 444-445, 540^541).

Late Proterozoic era (primitive life) : ^ 

Algonkian major division: \ 

Keweenawan period. 

Animikian period. 

Huronian period. 

Early Proterozoic era (primitive life) :

Neo-laurentian major division: ,* 

Algomian revolution. 

Sudburian period.

Archeozoic era (primal life; age of unicellular life) : 

. Paleo-laurentian major division:

Laurentian revolution and igneous invasion. 

Keewatin period 1 Coutchiching period jGrenvilleIn regard to the use of the names Archeozoic and Proterozoic, for the Age of 

Unicellular Life, and the Age of Primitive Marine Invertebrates, respectively, 

the following should be stated. As the post-Proterozoic eras are marked by an 

abundance of life preserved as fossils, it is highly desirable to bring out this 

fact in the names through the ending zoic, which means life. In the pre- J 

Cambrian eras, however, fossils are exceedingly scarce and a classification of / 

the formations on this basis cannot be developed, yet it is established that life l-W" 

existed throughout the Proterozoic and in all probability the Archeozoic as \ 

well. Therefore, the usage of zoic in these names is also desirable and har- T 

monizes them with those used for the later ages, even though the classification (^, 

of the rocks in the older eras is by geologic structure rather than by fossils. 

Because no direct and accepted evidence of life has been found in the Archeozoic era some geologists prefer to call it Archean (means very old), a noncom-
THE ERA TERMS 41

mittal term once applied to all pre-Cambrian formations. Azoic (without life) 

and Eozoic (dawn life) are other terms which have been used, but in this book 

Archeozoic is preferred because it means oldest or primal life, a significance in 

harmony with our present conception.

A. C. Law8on, 1916 (Cullfornla Univ. Dept. Geology Ball., vol. 10, \o. 1, 

chart opp. p. 18).

Paleozoic? era.

Algonkian (period, system).

Keweenawan (epoch,series). 

Animikian (epoch, series). 

Eparchean interval. 

Archean era.

Algoman revolution.9 

Huronian (period, system).

Temiskamian (epoch,series). 

Bruce (epoch, series). 

Epilaurentian revolution. 

Laurentian revolution.9 

Ontarian (period, system). 

Grenville (epoch, series). 

Keewatin (epoch, series). 

Coutchiching (epoch, series).

H. F. Cleland, 1916 (Textbook of geology, pp. 384, 388}.

Paleozoic era and group. 

Pre-Cambrian eras:

Proterozoic era and group (early life). 

Upper Proterozoic (Keweenawan). 

Middle Proterozoic (Upper Huronian). 

Lower Proterozoic: 

Middle Huronian. 

Lower Huronian.

Archeozoic era and group (beginning of life) : 

Laurentian. 

Keewatin.

A. Grnlmu, 1921 (Textbook of geology, p. 20).

Proterozoic era (Primary in part; Algonkian) :

Keweenawan system.

Animikean system.

Huronian system. 

Eozoic era (Primary in part; Arcluean in part) :

Algoman revolution.

Sudburian system. 

Archseozoic era (Primary in part; Archaean in part) :

Laurentian system.

Keewatin system. .

8 Adams (Problems of American Geology, p. 63) takes exception to placing the Laurentian and Algoman granites In the sequence of formations on the ground that they are 

intrusive masses and not members of the stratlgraphlc succession. It may be urged, 

however, that th© sequence is chronological as well as strattgraphic and In the standard 

scale we need a term for these two periods of batholithic development. Perhaps the 

terms Laurentian revolution and Algoman revolution used In the tabulation will meet 

the objection.
42 GEOLOGIC TIME CLASSIFICATION

A. P. Colemnn and W. A. Pavks, 1^22 (Textbook of geologry, p. 154).

Archean or pre-Cambrian: 

Proterozoic era:

Late Proterozoic period: 

Keweenawan epoch. 

Animikie epoch. 

Huronian epoch. 

Early Proterozoic period: 

Algoman epoch.

Sudburiari or Timiskamian epoch. 

Archeozoic era:

Laurentian epoch.

Keewatin and Grenville epochs.

C. Schuchert, 1924 (Textbook of geology, 2(1 ed., vol. 2).

[See quotation under "Eozoic era"]

Proterozoic is derived from the Greek words Trporepos (earlier, 

former, anterior, fore) and fcoi? (life). A shorter form (" Protozoic") was introduced by Sedgwick in 1838, to apply to all preCambrian time in case the rocks should be found to contain organic 

remains. (See definition of "Protozoic era," which follows.) The 

term Proterozoic was originally applied to the Algonkian period 

only. In later usages it has been, by different authors, applied (1) 

to all pre-Paleozoic time and (2) to the Algonkian period only. 

The United States Geological Survey has since 1907 applied the term 

to all pre-Paleozoic time represented by rocks visible for study.

" PROTOZOIC ERA " 

Rev. A. Sedgwick, 1838 (Geol. Soc. London Proc., vol. 2, No. 58, p. 684).

Class I. Primary stratified groups. Gneiss, mica slate, etc. etc. Highlands 

of Scotland and the Hebrides. Crystalline slates of Anglesea and the S. W. 

coast of Carnarvonshire.

The series generally without organic remains; but should organic remains 

appear unequivocally in any parts of this class, they may be described as the 

Protozoic system.

Class 1. (a). The crystalline slates of central Skiddaw forest, and the upper 

Skiddaw slate series. The whole is inorganic and intermediate between Class 

I and Class II. [The Skiddaw slates are now known to be of Ordovician age, 

and not intermediate between the Paleozoic and the " Protozoic," as originally 

supposed.]

Class II., or Palaeozoic series. This class includes all the groups of formations between Class I. and the old red sandstone; and is subdivided as follows: 

* * * [See under Paleozoic era.]

J. Phillips, 1855 (Manual of geology, p. 658).

Protozoic. The strata containing the earliest of the forms of life; the 

supposed first series of animals and plants. Trpuros (first), fwij (life) = 

primordial. .
THE PERIOD AND EPOCH TEEMS 43 

A. Stoppanl, 1873 (Corso di geologla, vol. 2, pp. 101-175).

Palaeozoic era (Cambrian at base). 

Protozoic era:

Huronian (strata with Eozoon canadense),

Laurentian 

Azoic era:

Intermediate Azoic terrain.

The term " Protozoic," introduced by Eev. A. Sedgwick in 1838, 

was suggested as 'a name for the pre-Cambrian rocks in case they 

should be found to contain organic remains. The word is derived 

from the Greek Trpwros (first) and $"0017 (life). Since this term was 

introduced the younger pre-Cambrian rocks, or those in America 

now commonly called Algonkian, have yielded fossils, consisting of 

crustaceans, brachiopods, and seaweeds, but the older pre-Cambrian 

rocks, or those now commonly called Arche'an, have not yielded any 

indisputable fossils, although many geologists and biologists are of 

the opinion that a low order of life existed during the Archean 

period.

" PpOZOIC ERA "

J. Phillips, 1S55 (Manual of geology, p. 624).

[On pages 76-89 the term " Hypozoic " is applied to the pre-Paleozoic rocks, 

but in the table on page 624 the pre-Paleozoic is called " Prozoic? period."]

F. M. Emllich, 1878 (U. S. Gcol. and Geogr. Survey Terr. Tenth Ann. Kept., 

p. 103).

Prozoic. In preference to the word " azoic," I use the term " prozoic." It 

presents a more ready definition than the former of the idea that it is intended to convey. Many groups of geological epochs are " azoic," but by no 

means was their genesis, as such, prior to the appearance of life upon the 

earth. * * * It often becomes a matter of considerable difficulty to discriminate between prozoic and metamorphic rocks.

" Prozoic " is derived from the Greek words irpb (before) and fco?; 

(life) and means " belonging to the period before the appearance 

,,of life on the earth." The time thus designated is included in the 

Proterozoic era by the United States Geological Survey.

THE PERIOD AND EPOCH TERMS

QUATERNARY PERIOD (OR SYSTEM)

J. Desaoyers, 182O (Observations sur un ensemble de depdts marina plus 

rccens a«e les terrains tertlalres (flu bassin <le la Seine, et constltuant 

une formation s'6olof?iq.ue tllstiucte; prficgdSes d'nn apercn de la non 

simultaneity ties basslns tertlalres: Annnles sci. nut., vol. 16, pp. 171 

214, 402-491).

What I wish especially to prove is that the series of Tertiary deposits 

continued, and even began in the more recent basins, a long time perhaps after 

the basin of the Seine had been entirely filled up, and that these later formations,
44 GEOLOGIC TIME CLASSIFICATION

Quaternary,10 so to speak, should not retain the name alluvial any more than 

the true and ancient Tertiary formations from which they must also be 

distinguished.

The rocks described by Desnoyers in the foregoing paper included 

marine, diluvial, alluvial, lacustrine, and volcanic deposits, the most 

recent of which were said to belong to the " actual and contemporary 

period."

Henri Rebonl, 1833 (GSologie de la pgriode qnaternalre, pp. 1 5, Paris).

The fossil remains of the Tertiary terranes almost all belong to extinct 

species. One encounters only a few analogues of species still living under other 

latitudes and in other places than those where fossil species are found. This 

is why we should call Quaternary 11 the subsequent period, the terranes of 

which are characterized by animal and vegetable species like those actually 

living in the same places. The names N§omastonian and Anthrope'ian are 

suitable also to this period, since it is conspicuous principally by the appearance 

of new mammals and especially of quadrupeds and of man. * * *

This period, considered in its connection with the succession of time, is 

divided naturally into two epochs; one, pre-historic, which embraces all the 

time anterior to the most ancient monuments of human societies; the other, 

which commences with these monuments and merits alone the name historic. 

The geognosy of the times occupied by the history of peoples is very limited 

and of slight interest. But this science alone remains to throw some light on 

the series of events that took place during the pre-historic epoch when men 

lived without leaving other monuments of their presence than the osseous 

debris or the products of some rude industry.

10 This expression is used here merely for the sake of brevity, and not to establish a 

sharp boundary between these more recent Tertiaries and the older, hitherto recognized; 

there being in my opinion no real boundary between them, and there being perhaps a 

more marked boundary between the lower and the middle group of deposits more recent 

than those of the Seine. For fear that my opinion in this respect may be considered as 

unsound, or exaggerated, I have abandoned the word Quaternary, which I wished at first 

to apply to all the deposits more recent than those of the Seine basin. [Page 193.]

11 M. J. Desnoyers is, I think, the first who proposed the name " Quaternary terranes," 

but those to which he applied it (the shell marls, the crags, the terranes of Herault) are 

only a division of the Tertiary class. If this division was admitted the 'Nfomastonian or 

Anthropgian. sediments should be called quinurius. The Tertiary terranes are then reduced to a few isolated basins, analogous, or supposedly analogous, to that of Paris.
THE PERIOD AND EPOCH TERMS 45

[Table opp. p. i] 

Table of geologic periods and epochs

Periods

 4 Quaternary of Ne'omastonian

:3. Tertiary or Palaio-mastonian

 2. Secondary or Ammonean

1. Primary

Epoch

Historic

Anti-historic

Alluvium

Upper

Lower

Upper

Middle

Lower

Upper

Lower

Subdivisions of terranes

Lacustrine

Marine

Lacustrine 

Marine

Cretaceous 

Oolitic or Jurassic

Liassic 

Keuper 

Peneon 

Pcecilian

Houiller [coal measures] 

Intermediate Protozoic

A. Morlot, 1856 (Notice snr le auaternaire en Snisse: Soc. vaudoise set. 

nat. Bull., vol. 4, i»i>. 41-45; read March 15, 1854).

In the paper cited above Morlot recognized the following subdivisions of the Quaternary period: First glacial epoch, diluvian epoch, 

second glacial epoch, and modern epoch.

These earliest definitions of Quaternary included in it the deposits 

now classified as Recent and Pleistocene or " Glacial," which is the 

definition adopted by the United States Geological Survey. The 

meaning of the word is " of the fourth order or rank." At the time 

of its introduction the preceding divisions of geologic time were 

 called Tertiary, Secondary, and Primary. " Secondary " and " Primary " have long since become obsolete, but Tertiary and Quaternary are still in common use.

The Quaternary period is characterized by animals and plants of 

modern types, and is commonly called the " age of man."

The present practice of most geologists includes all of the glacial 

epoch in the Quaternary period, and recognizes in it five ice stages 

separated by four interglacial stages, or intervals when the ice
46 GEOLOGIC TIME CLASSIFICATION

retreated and vegetation returned. To these glacial and interglacial 

stages the following names have been given in America, from areas 

where the record left by the ice of each stage is well shown or the 

soils of the interglacial stages are well developed:

Wisconsin stage of glaciation (the latest).

Peorian stage of deglaciation.

lowan stage of glaciation. 

Sangamon stage of deglaciation.

Illinoian stage of glaciation.

Yarmouth stage of deglaciation.

Kansan stage of glaciation.

Aftonian stage of deglaciation.

Nebraskan stage of glaciation, also called pre-Kansan stage (the oldest).

The correctness of including all the, glacial deposits of these successive ice stages in the Pleistocene epoch of the Quaternary period 

is not beyond question. In some unglaciated areas there have been 

found marine, fluviatile, and lacustrine deposits which .appear to 

correspond in age to glacial deposits of glaciated areas but which 

contain fossils (Sicilian) that paleontologists are inclined to class 

as of upper Pliocene age.

The names applied to the ice stages of Europe are given in the 

classification of Haug, the third on the accompanying chart. In 

the present state of knowledge the authorities on glacial geology 

correlate the Wurmian stage of Europe with the last, or Wisconsin, 

stage of America, the Kissian stage of Europe with the Illinoian 

stage of America, the Mindelian stage of Europe with the Kansan 

of America, and the Gunzian of Europe with the pre-Kansan of 

America.

Some geologists who have made a specialty of glacial geology are 

now of the opinion that the Kecent epoch, in which we are living, 

may be but an interglacial stage of the Pleistocene, and not a distinct epoch in the earth's history.

RECENT EPOCH (OR SERIES)

C. Lyell, 1833 (Principles of geology, vol. 3, pp. 52-53).

SUBDIVISIONS OF THE TERTIARY EPOCH

Recent formations. We shall now proceed to consider the subdivisions of 

tertiary strata which may be founded OB the results of a comparison of their 

respective fossils, and to give names to the periods to which they each belong. 

The tertiary epoch has been divided into three periods in the tables; we shall, 

however, endeavour to establish four, all distinct from the actual period, or 

that which has elapsed since the earth has been tenanted by man. To the 

events of this latter era, which we shall term the recent, we have exclusively 

confined ourselves in the two preceding volumes. All sedimentary deposits, 

all volcanic rocks, in a word, every geological monument, whether belonging
THE PEBIOD AND EPOCH TEEMS 47

to the animate or inanimate world, which appertains to this epoch, may be 

termed recent. Some recent species, therefore, are found fossil in various 

tertiary periods, and, on the other hand, others, like the Dodo, may be extinct, 

for it is sufficient that they should once have co-existed with man, to make 

them referable to this era.

Some authors apply the term contemporaneous to all the formations which

have originated during the human epoch; but as the word is so frequently in

use to express the synchronous origin of distinct formations, it would be a

source of great inconvenience and ambiguity, if we were to attach to it a

' technical sense.

We may sometimes prove, that certain strata belong to the recent period by 

aid of historical evidence, as parts of the delta of the Po, Rhone, and Nile, 

for example; at other times, by discovering imbedded remains of man or his 

works; but when we have no evidence of this kind, and we hesitate whether 

to ascribe a particular deposit to the recent era, or that immediately preceding, 

we must generally incline to refer it to the latter, for it will appear in the 

sequel, that the changes of the historical era are quite insignificant when contrasted with those even of the.newest tertiary period.

Although from the arrangement of headings in the foregoing 

quotation the Recent formations seem to be included in the Tertiary 

" epoch," on page 61 Lyell gives a " Synoptical table of Recent and 

Tertiary formations," in which the Recent is treated as distinct from 

and younger than the Tertiary. As above defined, however, Recent 

includes the Pleistocene and Recent of the present classification, as 

explained by Lyell in the 1873 quotation under Pleistocene epoch. 

The Pleistocene as now understood was removed from the Recent 

by Forbes in 1846 and by Lyell in 1873, as explained in the quotations from their papers that are given under Pl&istocene epoch. ">

PLEISTOCENE EPOCH (OR SERIES)

"" C. Lyell, 1839 (Elements of geology, French translation, appendix, pp. 

) 016-021, Paris, 1839).

; [See Lyell's explanation below, wluch is essentially a translation of the French passage

cited above]

C. Lyell, 1839 (Charleswortli's Mag. Nat. Hist., vol. 3, p. 323, footnote).

J~ In the Appendix to the French translation of my " Elements of Geology,"

4 I have proposed, for the sake of. brevity, to substitute the term Pleiocene for

} Older Pleiocem, and Pleistocene for Newer Pleiocene, from the Greek TrXeforoj,

most, and KeuwSs, recent. I have been induced to make this innovation, because

in proportion as the progress of science calls for subdivisions of these periods,

^

the longer terms have become more inconvenient. We have often for example, 

to speak of the older and neiver portion both of the older and newer pleiocene 

epochs. To the pleiocene period I have referred those strata which contain 

 ^ between 40 and 70 per cent of recent species of shells; to the pleistocene those 

in which the percentage exceeds 70. [In introducing the term Pliocene in 1833 

Lyell spelled the name Pliocene, and not as here quoted by him.]

Lyell's original definition of " Newer Pliocene " is quoted under 

PUocene epoch. The above original definition of Pleistocene applied 

the term to older deposits than are now included in it, as explained
48 GEOLOGIC TIME CLASSIFICATION

by Lyell in 1873 (see quotation given beyond). The following definition by Forbes is the commonly accepted definition of the present 

day:

Edward Forbes, 1S46 (On the connexion between the distribution of theexisting fauna and flora of the British Isles, and the geological changes 

which haye affected their area, especially during the epoch of the 

Northern Drift: Great Britain Geol. Survey Mem., vol. 1, pp. 4O2-403).

Throughout this essay I have used the epithet " glacial," in connexion with 

the words " epoch," " beds," and " formation," in a sense W'hich purists in 

geological phraseology may consider objectionable. I have used it, however, 

for want of a better, and as an expression of convenience, always intending toexpress by the phrase " Glacial epoch " that section of geological time which 

was typically distinguished by the .prevalence of severe climatal conditionsthrough a great 'part of the northern hemisphere, and during which those 

marine accumulations, in part truly sedimentary deposits, which have been 

called " Northern drift," were formed. I have selected the word " glacial," 

in order to remind the geologists of the ice-charged condition of our seas during 

that epoch, conditions which probably did not prevail during its earlier stage, 

and the gradual disappearance of which marked its conclusion. As, however, 

it appears almost certain that the " Glacial epoch," and that of the deposition 

of Sicilian and Rhodian tertiaries were synchronic it would be advisable to 

adopt some term to express that geological period as a whole, and by which 

to designate the formations of that period. Mr. Lyell's term, " pleistocene," 

would, perhaps, best serve the purpose, as that of " newer pliocene" is not 

sufficiently distinctive, and may lead to confusion. In this case, among English 

tertiaries, the ctoraline crag would rank as meiocene, the red crag as pleiocene, 

the glacial beds as pleistocene, and the megaceros freshwater marls and marine 

raised beaches as two stages of post-tertiary.

In 1873 Lyell withdrew his definition of Pleistocene (which applied to a late Pliocene division) and adopted Forbes's 1846 definition (which applied to deposits of early post-Tertiary age), as shown 

in the following quotation:

C. Lyell, 1873 (Antiquity of man, 4th ed., pp. 3-4).

Nomenclature. Some preliminary explanation of the nomenclature adopted 

in the following pages will be indispensable, that the meaning attached tothe terms Recent, Pleistocene or Post-Pliocene, and Post-Tertiary may be correctly understood. In the first edition of my " Principles of Geology," in 

1830 [vol. 3, first published in 1833] I divided the whole of the Tertiary formations into three groups; the Eocene, Miocene, and Pliocene, characterized 

by the percentage of extinct shells, or shells then unknown as living, which 

they contained. I then again subdivided the Pliocene into Older and Newer 

Pliocene. All strata of later age than these, or such as contained none but 

recent shells, I termed " Recent," and these strata were subsequently subdivided into Recent and Post-Pliocene, united under the general term PostTertiary.

In 1839 I proposed the term Pleistocene as an abbreviation for Newer 

Pliocene, and it soon became popular, because adopted by the late Edward 

Forbes in his admirable essay " On the Geological Relations of the existing 

Fauna and Flora of the British Isles; " but he applied the term almost precisely in the sense in which I have hitherto used Post-Pliocene, and not as
THE PERIOD AND EPOCH TEEMS 49

short for Newer Pliocene. In order, therefore, to prevent confusion, I 

thought it best entirely to abstain from the use of Pleistocene in future; but 

in a note to my " Elements of Geology," I advised such geologists as wished 

to retain Pleistocene to use it as strictly synonymous with Post-Pliocene. 

This was done by many, and has been found so convenient that it has now 

been very generally adopted; therefore, as the term Post-Pliocene has many 

inconveniences, especially that of being often confounded with Post-Tertiary, 

I propose, in this volume, to adopt the term Pleistocene for the lower subdivision of the Post-Tertiary, retaining only sometimes in brackets the word 

Eost-Pliocene, to remind the reader who is accustomed to that term that 

Pleistocene is used as its synonym.

As recognized by the United States Geological Survey and most 

other geologic authorities, the pre-Recent or Pleistocene epoch includes the deposits of the Great Ice Age, as it is popularly known, 

and contemporaneous marine, fluviatile, lacustrine, and volcanic 

rocks. In some areas it also probably includes some preglacial deposits and some postglacial deposits older than those of the Eecent 

epoch. (Seg further explanation under Quaternary period, where 

the names of the ice stages of the Pleistocene epoch are given.)

TERTIARY PERIOD (OR SYSTEM)

Giovnuiii Ardnino, 176O (Nnova raccolta (11 opuscoli scientific! e filologicf 

del itadre abate An/?iolo Caloglerfi, torn. 6, pi». 142 143, Venice, 1760).

To the most illustrious Sig. Cav. Antonio Valisuieri, Professor of Natural 

History in the University of Padua; second letter from Giovanni Arduino, 

Veronese-Vicentino:

On his various observations made in diverse parts of the territory of 

"Viceuza and elsewhere, concerning the theory of the earth and mineralogy. 

* » $

The tertiary mountains, or rather hills, are formed of a succession of strata 

of hard limestone of consolidated or unconsolidated sand and gravel, and of 

rock, and vitrified earth (but different from that of the primary mountains) 

and of earth of various colors.

These especially ought to be called tertiary, not only because they are 

seen in superposition on the slopes of the secondaries where the same hills 

terminate, but also because the greater part of their materials are shells, fragments, and comminuted sea shells; and fragments, flints, sand and mud derived 

from the disintegration of a great part of the primary and secondary mountains that evidently were once much higher and much less or perhaps not at 

all dissected and free from so many gullies, valleys, and ravines that are 

formed by the running of water.

As shown by the foregoing quotation, the original definition of 

the Tertiary system was contained in a letter written by Arduino to 

Antonio Valisuieri, professor of natural history in the University 

of Padua, and published in 1760, in vol. 6 of the " New collection 

of the scientific and philologic tracts of Father Abbot Angiolo Calogiera," a copy of which is in the Royal Library Vittorio Emanuele, 

at Rome, Italy, shelf number 79, A 15.
50 GEOLOGIC TIME CLASSIFICATION

Arduino's pioneer researches were followed by those of Cuvier, 

Brongniart, and Deshayes in the Paris Basin, of D'Halloy in Belgium, and of Webster, Buckland, and Lyell in> England. Large 

numbers of fossils were collected by these geologists in the different 

regions in which they worked. Upon the basis of their combined 

fossil studies Lyell in 1833 (see quotation under Pliocene epoch] 

divided the Tertiary into three " periods," to which he applied the 

names Eocene (the oldest), Miocene, and Pliocene (the youngest). 

The latter he divided into " Newer Pliocene " and " Older Pliocene." 

In 1839 Lyell restricted Pliocene to his " Older Pliocene," and introduced the new name Pleistocene for his "Newer Pliocene." (See 

quotation under Pleistocene epoch.) In 1846 Forbes adopted the 

term Pleistocene for the glacial deposits, evidently in the belief that 

Lyell had included these deposits in his Pleistocene " period." (See 

quotation from Forbes's report, under Pleistocene epoch.) Lyell, 

however, intended the term Pleistocene to apply to the latest Tertiary marine, lacustrine, and fluviatile deposits. But Forbes's application of the name to the glacial deposits became so popular that 

Lyell ceased to use Pleistocene for the " Newer Pliocene " sediments 

for which he had proposed it, and in 1873 (see quotation under Pleistocene epoch) he withdrew the name in that sense and adopted 

Forbes's application of it to the glacial deposits.

Lyell's subdivisions of the Tertiary (Eocene, Miocene, and Pliocene) continued to be the recognized divisions until 1854, although 

as studies of the Tertiary had progressed it was found that contemporaneous deposits were being called upper Eocene by some 

workers and lower Miocene by other workers. In 1854, therefore, 

Beyrich introduced the name Oligocene for the time interval 

covered by this series of transitional deposits. Thus a fourth term 

came to be added to the time divisions of the Tertiary period. 

These four epochs of the Tertiary are now recognized the world 

over.

As the Eocene deposits came to be better known the fossil plants 

contained in their basal part were believed by Schimper to differ 

sufficiently from those found higher in the Eocene to justify the 

separation from the Eocene of the rocks containing them. In 1874, 

therefore, he introduced the term " Paleocene " for the time interval 

covered by these rocks. Whether these deposits should be separated 

from the Eocene, and, if separated, whether they should be included 

in whole or only in part in the Tertiary, are questions upon which 

geologists and paleontologists are not even to-day fully agreed.

Although Lyell's names Eocene, Miocene, and Pliocene and Beyrich's Oligocene are recognized and used the world over, the 

modern conception of these Tertiary subdivisions is not strictly in
THE PERIOD AND EPOCH TERMS 51

accord with Lyell's conception of them. Most modern geologists 

and paleontologists do not draw the boundaries between these 

epochs on the basis of percentages of living species contained in the 

deposits, but on the general character of the fossils and on the 

stratigraphic and structural relations of the rocks containing them. 

The Tertiary period was characterized by the great numbers and 

large size of its mammals, for which reason it is commonly known 

as the " age of mammals." It also witnessed the rise and development of the highest order of plants, and was distinguished by great 

volcanic activity, as shown by the occurrence of great masses of 

Tertiary volcanic rocks in all parts of the world.

PLIOCENE EPOCH (OR SERIES)

C. Lyell, 1833 (Principles of geology, vol. 3, pp. 52-55. 57-58). 

SUBDIVISIONS OF THE TERTIARY EPOCH

Newer Pliocene period. This most modern of the four subdivisions of the 

whole tertiary epoch we pro°pose to call the Newer Pliocene, which, together 

with the Older Pliocene, constitute one group in the annexed tables of M. 

Deshayes.

We derive the term Pliocene from irXeluv, major, and Katv6s, recens, as the 

major part of the fossil testacea of this epoch are referable to recent species.12 

Whether in all cases there may hereafter prove to be an absolute preponderance 

of recent species, in every group of strata assigned to this period in the tables, 

is very doubtful; but the proportion of living species, where least considerable, 

usually approaches to one-half of the total number, and appears always to 

exceed a third; and as our acquaintance with the testacea of the Mediterranean, 

and some other seas, increases, it is probable that a greater proportion will be 

identified.

The newer Pliocene formations, before alluded to, pass insensibly into those 

of the Recent epoch, and contain an immense preponderance of recent species. 

It will be seen that of two hundred and twenty-six species, found in the Sicilian 

beds, only ten are of extinct or unknown species, although the antiquity of 

these tertiary deposits, as contrasted with our most remote historical eras, is 

immensely great. In the volcanic and sedimentary strata of the district round 

Naples, the proportion appears to be even still smaller.

Older Pliocene period. These formations, therefore, and others wherein the 

plurality of living species is so very decided, we shall term the Newer Pliocene, 

while those of the tertiary period immediately preceding may be called the 

Older Pliocene. To the latter belong the formations of Tuscany, and of the 

Subapennine hills in the north of Italy, as also the English Crag.

It appears that in the period last mentioned, the proportion of recent species 

varies from upwards of a third to somewhat more than half of the entire 

number; but it must be recollected, that this relation to the recent epoch is 

only one of its zoological characters, and that certain peculiar species of 

testacea also distinguish its deposits from all other strata. The relative posi12 In the terms Pliocene, Miocene, and Eocene, the Greek diphthongs ei and ai are 

changed into the vowels i and e, in conformity with the idiom of our language. Thus 

we have Encenia, an inaugural ceremony, derived frem b and /cau>6s recens; and as examples 

of the conversion of ei into i, we have icosahedron. * * *
52 GEOLOGIC TIME CLASSIFICATION

 

tion of the beds referable to this era has been explained in diagrams Nos. 3

and 4, letter f, chapter II.

Miocene period. The next antecedent tertiary epoch we shall name Miocene, 

from peluv, minor, and KO.IVOS, recens, a minority only of fossil shells imbedded 

in the formations of this period, being of recent species. The total number 

of Miocene shells, referred to in the annexed tables, amounts to 1021, of which 

one hundred and seventy-six only are recent, being in the proportion of rather 

less than eighteen in one hundred. Of species common to this period, and to 

the two divisions of the Pliocene epoch before alluded to, there are one hundred and ninety-six, whereof one hundred and fourteen are living, and the 

remaining eighty-two extinct, or only known as fossil.

As there are a certain number of fossil species which are characteristic of 

the Pliocene strata before described, so also there are many shells exclusively confined to the Miocene period. We have already stated, that in Touraine 

find in the South of France near Bordeaux, in Piedmont, in the basin of 

Vienna, and other localities, these Miocene formations are largely developed, 

and their relative position has been shown in diagrams Nos. 3 and 4, letter e, 

chapter II.

Eocene period. The period next antecedent we shall call Eocene, from 

i7&s, aurora, and K<uvsb, recens, because the extremely small proportion of living 

species contained in these strata, indicates what may be considered the first 

commencement, or daum, of the existing state of the animate creation. To 

this era the formations first called tertiary, of the Paris and London basins, 

are referable. Their position is shown in the diagrams Nos. 3 and 4, letter d, 

in the second chapter.

The total number of fossil shells of this period already known, is one 

thousand two hundred and thirty-eight, of which number forty-two only are 

living species, being nearly in the proportion of three and a half in one 

hundred. . Of fossil species, not known as recent, forty-two are common to 

the Eocene and Miocene epochs. In the Paris basin alone, 1122 species have 

been found fossil, of which thirty-eight only are still living.

The geographical distribution of those recent species which are found fossil 

in formations of such high antiquity as those of the Paris and London basins, 

is a subject of the highest interest. * * * [Pages 52-55.]

If intermediate formations shall hereafter be found between the Eocene and 

Miocene, and between those of the last period and the Pliocene, we may still 

find an appropriate place for all, by forming subdivisions on the same principle 

as that which has determined us to separate the lower from the upper Pliocene 

groups. Thus, for example, we might have three divisions of the Eocene 

epoch, the older, middle, and newer; and three similar subdivisions, both of 

the Miocene and Pliocene epochs. In that case, the formations of the middle 

period must be considered as the types from which the assemblage of organic 

remains in the groups immediately antecedent or subsequent will diverge. 

* * * [Pages 57-58.]

In 1839 Lyell 13 restricted the term Pliocene to the " Older Pliocene " of his 1833 definition, and introduced the term Pleistocene 

for the " Newer Pliocene." But the use of Pleistocene for the 

u Newer Pliocene" was abandoned by him in 1873 (see quotations 

under Pleistocene epoch, p. 48), and he, as well as others, returned

13 Lyell, C., On the relative ages of the Tertiary deposits commonly called " crag" in 

the counties of Norfolk and Suffolk: Charlesworth's Mag. Nat. Hist., new ser., vol. 3, p. 

323, footnote, 1839.
THE PERIOD AND EPOCH TERMS 53

to his original definition of Pliocene, and adopted Forbes's definition 

of Pleistocene (1846) for the early post-Tertiary glacial deposits. 

(See further explanation under Tertiary period.}

MIOCENE EPOCH (OR SERIES)

C. Lyell, 1833 (Principles of geology, vol. 3, pp. 52-55, 57-58).

[See quotation under Pliocene epoch and explanation under Tertiary period]

OLIGOCENE EPOCH (QR SERIES)

ID. Bcyrich, 1854 (Ueber die Stellung der hesslsclien Tertlttr-blldunff en t 

K. preuss. Akiad. Wiss. Berlin Monatsber., November, 1854, pp. 6G4 066).

In conclusion I list below in a schematic summary the accepted sequence of 

the corresponding observed German and Belgian Tertiary beds. I consider it

 expedient to introduce a new name to designate the Tertiary time interval 

whose beds are primarily the subject of the discussion, that is, for the Tertiary 

deposits which exist between the two Tertiary time intervals which are generally known by the names introduced by Lyell; Eocene and Miocene. The 

need to associate under one common designation, as a narrow unit related

 within itself, the particular aggregate lying within these boundaries has often 

"been felt by those who have devoted their attention to the Tertiary beds. To 

fill the need sometimes the name Lower Miocene and sometimes Upper Eocene 

has been used. Lyell uses Upper Eocene; I myself heretofore have used Lower 

Miocene. In a memoir on the Tertiary formations of the Basin of the Mayence, 

Hamilton, of the English geologists, has declared himself against Lyell for the 

name Lower Miocene. The new name Oligocene may be interposed between 

the older Eocene and younger Miocene.

 SUMMARY OF TERTIARY BEDS OF MAYENCE BASIN, MIDDLE AND NORTH GERMANY, 

AND CORRESPONDING BEDS OF BELGIUM

A. Miocene

Belgium: Bolderian system.

North Germany: Dark sandy loams near Winterswyk in Holland and near 

Bocholt in Westphalia; at Bersenbriick north of Bramsche on the Hase; at 

Eversen and Feuerschiitzenbostel near Celle; at Luneburg; Reinbeck; Sylt. 

Eastern occurrence near Giihlitz north of Perleberg in the Priegnitz region. 

Middle Germany: None. 

Mayence Basin: None.

B. Oligocene

1. Belgium: None.

North Germany: Sands, in which occur the " mussel rocks " of Sternberg,

not yet definitely identified in eastern portion. Loamy sand rich in mussel

shells known from borings near Crefeld. 

Middle Germany: Upper yellow marine sands near Cassel, Guntersen, Luithorst, Alfeld, Hildesheim, Bunde, Osnabruck. 

Mayence Basin: None.

2. Belgium: Upper rupelian system. Loam of Boom.

North Germany: Septaria loam of Walle near Celle; Hohenwarthe on the

Elbe below Magdeburg; Burg; Gorzig near Kb'then, in the Mark province

near Herrnsdorf, Freienwalde, Bukow, Joachimsthal; on the Oder River

near Stettin. 

Middle Germany: The same loam at Ober-Kaufungen near Cassel; Eckardroth west of Schliichtern. 

Mayence Basin: None.
54 GEOLOGIC TIME CLASSIFICATION

3. Belgium: Lower rupelian system. Sand with scallops and clay with Nucula

near Kleyn-Spauwen. 

North Germany: None.

Middle Germany: Clay with iron ore near Rheinhardts\valde. 

Mayence Basin: None.

4. Belgium: Upper tongrian system. Brackish-water deposits. 

North Germany: None.

Middle Germany: Fresh-water deposits with lignite. 

Mayence Basin: Entire succession of brackish-water and fresh-water beds

(Gyrene marl, limestone containing land molluskfc [snails] and Cerithia-;

Littorinella limestone, lignite beds, sandstone bearing fossil leaves, bone

sand of Eppelsheim).

5. Belgium: None.

North Germany: None.

Middle Germany: None.

Mayence Basin: Lower marine sand of Absei.

6. Belgium: Lower tongrian system.

North Germany: Glauconitic loamy sands and sandy loams above the lignite

near Westeregeln, Biere, Calbe a. S.; Osterweddingen. 

Middle Germany: None. 

Mayence Basin: None.

7. Belgium: None.

North Germany: Lignite-bearing Tertiary beds of the lowlands of northeast

Germany.

Middle Germany: None. 

Mayence Basin: None.

C. Eocene

Belgium: From the Laekenian system downward.

Absent in Germany north of the Alps and farther east north of the Carpathian Mountains.

The Oligocene deposits were originally included in the Eocene 

epoch, as explained on page 50, under Tertiary period. The word is 

of Greek derivation, from 6X170? (small, little) and KO.IVOS (new, 

recent).

EOCENE EPOCH (OR SERIES) 

C. Lyell, 1833 (Principles of geology, vol. 3, pp. 52-55, 57-58).

For the original definition of Eocene see the quotation under 

Pliocene epoch. As originally defined by Lyell the term applied to 

all pre-Miocene Tertiary deposits. The recognition of Oligocene and 

" Paleocene " is mentioned under Tertiary period, on page 50.

" PALEOCENE " 

W. P. Schimper, 1874 (TraitS de paleontologie vegetale, vol. 3, pp. G8O-682).

VIII. Tertiary epoch. 

I. Paleocene period.

Sands of Bracheux, ancient travertines of Sezanne, lignites and sandstones 

of Soissonais (Suessonian).

I have grouped all the vegetation of the Tertiary into five distinct floras, 

which does not mean that I consider the five floras as independent of one
THE PERIOD AND EPOCH TEEMS . 55

another. All these floras are interrelated in time as our local floras are in 

space. But in spite of the evident continuity in the evolution of the organic 

kingdom through the geologic ages there can nevertheless be distinguished 

in this continuous and progressive movement a constant change in the grouping 

and relative development of types, a change which enables us to identify for 

each epoch, and even for each geologic period, a group of forms constituting 

what we call the organic character of the epoch or of the period.

The group of plants or the flora of the period now under discussion, although allied closely with the Heersian flora, which is the continuation of the 

Cretaceous flora, and still more directly with the Eocene, has, nevertheless, 

an aspect peculiar to itself, which distinguishes it at a glance. It has in 

common with the preceding Cretaceous period the tropical and subtropical 

types of ferns (Cyathea, Alsophila, Hemitelia), to which are united others 

resembling more closely our types of temperate climates, such as Blechnum, 

Aspleniiim, Athyrium. The Pandanaceae are represented by the genus Nipadites and a new type, which perhaps has its analogy in the Carludovica, 

which exists at the present time in the tropical regions of America. Palm 

trees are also found, but they resemble more closely the sabals than those of 

the Cretaceous terrane. The Myricacese, Cupulifersa, Saliciaceae, Lauracese, 

Ampelideaa, Araliacese, Magnoliaceae, and Juglandaceae persist, but with more 

or less pronounced specific modifications; the Tiliacese, under a form analogous 

to the Grewia, a genus indigenous to the tropics of the Old and New World; 

genera of Malvaceae, the Pterospernum, an Indian type, and the Sterculia, 

which inhabit the same zones as the Aralia, constitute a new element, the 

same as the Moracese, with the genera Protoficus and Artocarpoides, and the 

Sapotacese with the type Symplocos. Some of the families which have made 

their appearance during the last period are in process of development, as the 

Cupuliferse, which are enriched by the genera Carpinus and Quercus, not to 

mention the genera Fagus and Castanea, whose right of citizenship is not yet 

beyond doubt; the Saules are becoming more numerous and the family itself 

is augmented by the genus Populus. The figs and the laurels already show 

rather varied types; the latter are even represented by five genera, of which 

four have their principal representatives in Asia, and one, the Sassafras, in 

North America. The Araliacew, which in the Eocene flora showed such great 

development, enrich the tropical aspect of this luxuriant vegetation by more 

numerous forms. I say luxuriant because nearly all the trees of this first 

Tertiary flora, even some of those which have remained European, such as 

Viburnum, Juglans, and Cornus, are distinguished by an extraordinary richness of foliage. It is true that we know only the remnants of two local floras, 

that of Sezanne and that of the Soissonnais Basin, and it is possible that 

these forests owed their exceptional splendor to local circumstances only 

much humidity coupled with tropical temperature. This humidity appears to 

be proved at least for Sezanne, where there was a lake on the banks of 

 which were deposited the travertines which have transmitted to us the 

imprints of the leaves derived from the surrounding vegetation.

An interesting thing to note for this flora is the considerable number of plant 

types now belonging to the Northern Hemisphere and in part to the European 

flora; in the Cretaceous flora, on the contrary, the types of the Southern 

Hemisphere predominate; the forms of the most extreme points of our globe 

are assembled in it, while the Paleocene flora already shows a tendency-to 

differentiation, in the sense that it concentrates more on the types which must 

later dominate in the Northern Hemisphere. A glance at the plate which 

follows will suffice to convince one of this curious fact.
56 GEOLOGIC TIME CLASSIFICATION

I have said that the Paleocene flora is represented only by fragments in tworather restricted localities, one of which is at the Grottos near Sezanne 

(Champagne) and the? other in the neighborhood of So»issons (sands of 

Bracheux, lignites and sandstones of Soissonnais). Perhaps the lower 

liffnites of Provence (lower Ventabren, Belcodeme, Auriol) form a part of thesame geologic horizon; the small number of determinable plant remains known 

of this formation does not permit a decision of this question. [Flora listed.}

The status and limits of " Paleocene " as now understood by vertebrate paleontologists were briefly stated by W. D. Matthew 14 m 

1920, as follows:

The term Paleocene has been revived by several vertebrate paleontologists 

in recent years to cover the faunal zones previously known as Basal Eocene. 

Upon evidence of the vertebrate faunas it is entitled to rank as a distinct 

epoch, coordinate with the Eocene and Oligocene. ; It includes the Puerco, 

Torrejon, Fort Union, and probably certain less known vertebrate faunasin this country, and the Cernaysian in France. Its upper limit is marked 

by the first appearance of the principal modern orders of mammals and of 

certain modern groups of reptiles simultaneously in Western America and in 

Western Europe. The lower limit is more doubtfully fixed by the first appearance of placental mammals. The evidence of marine invertebrates and of 

plants does not at present appear to support the distinction of the Paleocene 

as a separate epoch. It is possible, however, that it covers the gap between 

the Cretaceous and Tertiary insisted upon by many stratigraphers and paleobotanists, and there are other possible interpretations that might reconcile the 

evidence. The writer believes that the epoch may also prove to include the 

Lance and certain other dinosaur-bearing formations, and that it may belong 

rather to the Cretaceous than to the Tertiary period. No final conclusions 

are in order until the evidence in different fields has been satisfactorily 

reconciled.

"Paleocene" is derived from the Greek] TraXcuos (ancient) and 

KCUVOS (recent). The United States Geological Survey has not yet 

adopted the term.

J. J. d'Omallns d'Halloy, 1822 (Observations snr uu essai de carte gfeologrlque de la France, des Pays-Has et des contrees volsines: Annales des 

mines, vol. 7, pp. 373-374).

Here, then, are the names that I propose to give to the five groups that I 

have thought best to establish in the Secondary terrains.

I would call the first Peneen terrains, words which are only, so to speak, the 

translation of Todteliegende, and which may also be considered as recalling 

the circumstance that the most characteristic beds are ordinarily poor in 

fossil remains.

The second group will be designated by the name of Ammoneen terrains, 

words which will recall that all the systems of which it is composed have been 

formed during one epoch, in which existed the remarkable animals known as 

ammonites.

"Matthew, W. D., Status and limits of the Paleocene: Geol. Soc. America Bull., vol. 

31, p. 221, 1920.
THE PEKIOD AND EPOCH TEEMS 57

The third, which corresponds to what has already been called the chalk 

formation, will be designated by the name of Cretaceous terrain.15

The name Mastozootic, applied to the fourth group, -will recall that in the 

midst of these terrains there are found the bones of mammals, the study of 

which has given birth to the beautiful work which has, as it were, created 

geology among us.

Finally, the fifth group will be designated by the name of Pyroide, which, 

without indicating anything definite as to the manner in which these terrains 

were formed, implies that they all resemble those that have a demonstrated 

Igneous origin.

The essay above cited was reprinted in 1823 as a separate volume, 

accompanied by a geologic map, the explanation of which is as follows:

Pyroide terrains, comprising the products of present volcanoes, as well as 

the basaltic and trachytic terrains.

Mastozootic terrains, comprising all the terrains later than the chalk, the 

aqueous origin of which is undisputed.

Cretaceous terrains, corresponding to the formation of the chalk, with its 

tufas, its sands, and its clays.

Ammoneen terrains, comprising the Jurassic limestone, the Quader sandstone 

[now assigned to Cenomanian], the Muschelkalk [now assigned to Middle 

Triassic], the mottled sandstone, and the Zechstein [now included in Permian].

Peneen terrains, comprising the Macigno, the red sandstone, and the Todteliegende.

Primordial terrains, comprising the transitional terrains and the primitive 

terrains.

As thus defined D'Halloy's Cretaceous terrain applied to all deposits between the Tertiary and the Jurassic, and thus became a 

general term to include the French " craie," the English " chalk," 

and the German " Kreide " or " Kreidegebirge." It excluded the 

Quader sandstone of Germany, which was soon transferred to the 

Cretaceous, after its fossils had become better known. With that 

exception the original definition of Cretaceous corresponds with the 

definition generally used to-day.

The term was introduced into the geology of America by S. G. 

Morton, in 1834, in his " Synopsis of the organic remains of the Cretaceous group of the United States," a book of more than 100 

pages, with descriptions of fossils and 19 plates of figures of the 

fossils. On pages 7-8 of this book Morton says:

CKETACEOUS GROUP OF THE UNITED STATES EQUIVALENTS IN EUBOPE

Ferruginous Sand. Mr. Vanuxem was the first to detect the analogy between 

this deposit and the chalk formation of Europe; although, as mentioned in the

16 It is to be remarked that in a division less appropriate to the physical geography of 

France there might be reason to unite this little group to the preceding, and that in this 

case the denomination Ammoneen terrains may all the better be preserved, as there still 

existed ammonites when the chalk was formed. This name and that of Peneen terrains 

may also be preserved in case the Zechstein and the mottled sandstone should pass into 

the first group; because these two systems are not ordinarily very rich in animal 

remains.
58 GEOLOGIC TIME CLASSIFICATION

preface, he did not refer it to any particular division of the chalk. My first 

essay (Journ. Acad. Nat. Science, Vol. VI, p. 97,1827), published simultaneously 

with Mr. Vanuxem's, suggests its analogy to the lower mass of the cretaceous 

group, called by the French la craie inferieure ou ancienne, which in England 

is designated as the Green Sand Formation, or Ferruginous Sand Series.19

My subsequent researches during seven years have fully confirmed the preceding opinion.

Calcareous Strata. These were first noticed by myself in the year 1829. A 

careful examination of a great number of organic remains has induced me to 

consider these beds as of the same age as the white chalk of Europe: but as 

the American strata contain, as will be shown hereafter, some Tertiary shells, 

a positive decision must be deferred, until sanctioned by further observation.

In Europe two major divisions of the Cretaceous were early 

recognized, but the boundary between them has been placed differently from time to time and by different geologists. At first only 

the White Chalk was assigned to the Upper Cretaceous, and all the 

underlying rocks were called Lower Cretaceous; but later the 

boundary between Upper and Lower Cretaceous most generally accepted by continental geologists has been the boundary between 

Cenomanian and Albian, or Gault. In England it has been customary to refer the Gault to the Upper Cretaceous. To some 

geologists a threefold division of the Cretaceous has seemed more 

satisfactory. For example, Haug has grouped Albian, Cenomanian, 

and Turonian together to form Middle Cretaceous.

It was long supposed that the marine Cretaceous of the United 

States is all of Upper Cretaceous age, but in 1869 Gabb recognized 

the Lower Cretaceous age of the rocks in California which he named 

the Shasta group, now called the Shasta series. In 1887 K. T. Hill 

proved that a thick series of Cretaceous rocks in Texas, which he 

named the Comanche series, is older than the previously better 

known Cretaceous of the Gulf and Atlantic Coastal Plain, which he 

named the Gulf series. The two series are characterized by distinct 

faunas, and are at least locally separated by an unconformity, which 

Hill believed to be important. On account of this unconformity 

and the distinctness of the fauna Chamberlin and Salisbury later 

raised Comanchean to the rank of a system, in which they included 

the Shasta series and other Lower Cretaceous rocks. They have 

been followed in this method of treatment by a considerable number 

of geologists. The United States Geological Survey, however, still 

uses Comanche as the name of a provincial series of early Cretaceous rocks in Texas and neighboring regions. The name Cretaceous is derived from the Latin creta (chalk) and the suffix -aceus 

(of the nature of).

18 Conybeare and Phillips describe the Ferruginous sand of England as composed of 

these four subdivisions, counting from below: 1, Ironsand ; 2, Weald clay; 3, Green 

sand; 4, Chalk Marl. (Geol. pp. 60, 120, &c.) The whole series, embracing the White 

Chalk, is now very generally called the Cretaceous Group.
THE PERIOD AND EPOCH TERMS 59

R. T. Hill, 1887 (Am. Jour. Scl., 3d ser., vol. 33, pp. 298, 3OO).

As shown in the table on page 298 of the volume above cited, the 

Gulf series included Upper Cretaceous and so-called Middle Cretaceous deposits unconformably overlying the Comanche series 

(Lower Cretaceous). On the same page Hill subdivided the Gulf 

series from Elmo, Kaufman County, to Millsap, Parker County, Tex.. 

as follows, in descending order: Navarro beds, Dallas limestone, 

Eagle Ford shales, and Timber Creek group. In 1889 17 and in later 

reports, however, Hill made the term synonymous with Upper Cretaceous. Upper Cretaceous being extended to include the " Middle 

Cretaceous " deposits of his earlier report. Since 1889 the recognition of a so-called " Middle Cretaceous" has been almost universally discontinued, and all Cretaceous deposits overlying the 

Comanche series of the Gulf Coastal Plain have been recognized as 

belonging to the Gulf series, or Upper Cretaceous. The importance 

of the unconformity between the Gulf and Comanche series is also 

now questioned.

The name Gulf sei4es, as now recognized, is a provincial series term 

applied to the upper part of the marine Cretaceous rocks of the 

southwestern part of the United States, the lower part of the Cretaceous rocks of that region being known as the Comanche series. 

The Gulf series was named for it's extensive development along the 

Coastal Plain of the Gulf of Mexico. For additional explanation see 

under Cretaceous period.

COMANCHE EPOCH (OR SERIES) 

R. T. Hill, 18ST (Am. Jour. Sci., 3d ser., vol. 33, p. 298, April, 1887).

Comanche series (Lower Cretaceous). This series is one of unbroken 

sedimentation and faunal continuity from base to top. Subdivisions are temporarily designated by horizons of prominent fossils. Many species continue 

throughout the entire series.

On the page cited above Hill divided the series into the Upper 

or Washita division and the Lower or Fredericksburg division, 

with subdivisions temporarily designated by horizons of prominent 

fossils, and showed it resting on "Dinosaur sand" and unconformably overlain by the Gulf series. The importance of this unconformity is, however, now questioned.

In April, 1887,18 C. A. White included the "Dinosaur sand" 

(Trinity group of later reports) in the Comanche series, and that

17 Hill, R. T., Relation of the uppermost Cretaceous beds of the eastern and southern 

United States: Am. Jour. ScL, 3d ser., vol. 38, p. 469, 1889.

18 White, C. A., On the Cretaceous formations of Texas and their relation to those of 

other portions of North America : Acad. Nat. Sci. Philadelphia Proc., vol. 39, p. 40, 1887.

1146 25 5
60 GEOLOGIC TIME CLASSIFICATION

extended definition was adopted by Hill in October, 1887,19 and has 

since been used by all writers. The series was named for Comanche, 

Comanche County, Texas, as stated by Hill in the First Annual 

Report of the Texas Geological Survey, page 117, 1890.

T. C. Chamberlin and R. D. Salisbury, 19OO (Geology, vol. 3, pp. 1O7 137).

The formations of the Cretaceous system are commonly divided into two 

main series, the Lower and Upper. To the former are referred the deposits 

of the earlier and lesser submergence, and to the latter, those of the later 

and more extensive submergence. The distinctness of the Lower and Upper 

Cretaceous is however so great that it seems, on the whole, in keeping with 

the spirit of the classification here^ adopted, to regard the two series as 

separate systems, and the corresponding divisions of time as separate periods. 

From the physical standpoint, the distinction between the Upper and Lower 

Cretaceous is greater than that between the different parts of any Paleozoic 

system, as commonly classified, if the Mississippian. and the Pennsylvanian 

be regarded as separate systems, and greater than that between the Cambrian 

and the Ordovician, or between the Devonian and Mississippian. The paleontological phase of the question is discussed elsewhere. If the Lower 

Cretaceous be separated from the Upper, it may be called the Comanchean 

or Shastan system.20 The propriety of this classification becomes the more 

striking, since it is equally applicable to other continents.

This classification involves no new idea. Hill, who has made a special study 

of the North American Cretaceous where both the Lower and Upper systems 

are developed, has repeatedly emphasized their distinctness, and Neumayer, 

after reviewing the relevant evidence, drawn chiefly from the phenomena of 

the old world, concludes that if the distinctness of the Lower and Upper Cretaceous had been known when the accepted time-divisions were established, 

they would have been made separate divisions of equal rank with the Triassic, 

Jurassic, etc. The Lower and Upper Cretaceous are therefore here considered 

as two somewhat associated periods, coordinate with the Triassic and Jurassic.

THE COMANCHEAN (SHASTIAN, LOWER CRETACEOUS) SYSTEM

The warping which marked the opening of the Comanchean period occasioned 

the development of extensive lakes or other basins of non-marine deposition in 

some parts of the continent, while other parts were depressed beneath the sea. 

The Comanchean deposits of the Atlantic and Eastern-Gulf coastal plains, and 

in certain parts of the western interior, are non-marine; those of the western 

Gulf region, extending as far north as the Ouachita Mountains and even a little 

beyond, are chiefly marine, while those of the Pacific coast are wholly so. From 

the distribution of the marine strata of the system, it is clear that by far the 

larger part of the continent was above sea level during the period, unless the 

deposits have been extensively removed by erosion, and this does not appear 

to be the case. * * * [Pages 107-108.]

The later Cretaceous period (which will herafter be called the Cretaceous) 

may be said to have been ushered in, so far as North America is concerned, by 

a notable encroachment of the sea on the land. [Page 137.]

The name Comanche series is applied to a provincial scries of marine deposits constituting the lower part of the Cretaceous rocks of

19 Hill, R. T., The Texas section of the American Cretaceous: Am. JoiiP. Sci., 3d ser., 

vol. 34, p. 288, 1887.

20 The first of these terms has been applied to the Lower Cretaceous of .Texas (Hill), 

and the second, by Le Conte and others, to the Lower Cretaceous of California.
THE PERIOD AND EPOCH TERMS 61

the southwestern part of the United States, the overlying Cretaceous 

rocks of that region being known as the Gulf series. The lower 

part of the marine Cretaceous rocks as developed along the Pacific 

coast comprises another provincial series, to which the name Shasta 

series has been given. The reason for the use of the two names, Comanche series and Shasta series, for approximately contemporaneous 

deposits in western America is that they were deposited in different 

seas, between which there was no known connection, and their 

faunas and floras are so different that exact con-elation has not been 

established. The Comanche sea covered parts of the States of Texas, 

Oklahoma, Arkansas, Kansas, Colorado, New Mexico, and Arizonaf 

(See additional explanation under Cretaceous period.)

SHASTA EPOCH (OR SERIES)

W. M. Gabb, 1869 (California Geol. Survey, Paleontology, vol. 2, pp. vll, 

xlv, 129, 133).

In the preface J. D. Whitney states:

The present volume is devoted to the Tertiary and Cretaceous paleontology, 

and is entirely the work of Mr. Gabb. [Page vii.]

The Shasta Group is a provisional name, proposed to include a series of 

beds of different ages, but which, from our imperfect knowledge of the subject, can not yet be separated; it includes all below the Chico Group. It contains fossils, seemingly representing ages from the Gault to the Neocomien. 

inclusive, and is found principally in the mountains west and northwest of 

the Sacramento Valley. Two or three of its characteristic fossils have been 

found in the vicinity of Monte Diablo, and one of the same species has been 

sent from Washington Territory, east of Puget Sound. 'Few, or none, of its 

fossils are known to extend upwards into the Chico Group. [Page xiv.]

Gabb states:

Shasta Group. For reasons which will be detailed in their proper place, I 

consider the group, for which I here propose this name, to be the equivalent, 

or at least the nearest representative, of the Neocomien. It has been heretofore included, for want of positive grounds for separation, as a provisional 

member of the " Division A," of the California Cretaceous. * * * [Page 129.]

The absolute age of the Cretaceous strata of the northern part of the State 

has,not yet been fully determined, but, as will be explained in the proper place, 

it seems not improbable that representatives of both the Gault and Lower 

Green Sand will be found included in what has here been provisionally termed 

the Shasta Group. [Page 133.]

The fauna of the Shasta " group " is described on succeeding pages 

of the book cited. Most of the fossils were collected in Shasta 

County, Calif., whence the derivation of the name.

The name Shasta series is a provincial series term, applied to the 

lower part of the marine Cretaceous rocks as developed on the Pacific 

coast. 
62 GEOLOGIC TIME CLASSIFICATION

JURASSIC PERIOD (OR SYSTEM) 

A. von Humboldt, 1799 ("Ueber die unterirdisehen Gasarten, p. 39).

No copy of the above book is known in this country, but in Kosmos, 

volume 4, page 632, Stuttgart, 1858, Humboldt makes the following 

statements:

Upon a geological trip which I made in 1795 through southern France, western Switzerland, and northern Italy, I became convinced that the JuraKalkstein [Jura limestone], which Werner assigned to his Muschelkalk [the 

middle division of the Trlassic], was a distinct formation. In my paper 

"Ueber die unterirdischen Gasarten," which my brother Wilhelm von Humboldt published in 1799, during my absence in South America, the formation is 

for the first time mentioned as the Jura-Kalkstein (p. 39). The establishing of 

this new formation was at once made known in the widely read Karsten's 

Mineralogische Tabellen (1800, p. 64 and introduction, p. vii). I named none 

of the fossils which characterize the Jura formation, and which Leopold von 

Buch described in 1839; but I erred in the age which I attributed to the Jura ' 

formation; on account of their proximity to the Alps, which were regarded as 

Zechstein, I regarded them as older than the Muschelkalk. In Buckland's 

first tables of the superposition of strata in the British Islands the Jura limestone of Humboldt is placed as Upper Oolite. [Refers to Humboldt. Essai 

geognostique sur le gisement des roche^jl.823, p. 281.]

Although the name Jurassic had its inception with the Jura limestone of Humboldt (first published in 1799), Humboldt applied that 

name to only a small part of the Jurassic system of present usage, 

or to a part of the "Upper Oolite." (See accompanying chart.)

The following quotations from Zittel 21 give, briefly, the origin of 

the definition as it is now understood:

In the very beginning of the nineteenth century the fundamental features of 

the Jurassic succession had been so securely established by William Smith 

[of England] that subsequent observers had little to amend. The Jurassic 

deposits have attained a remarkably typical and perfect development in 

England. No serious obstacles of any kind are interposed in the path of the 

observer; no great tectonic disturbances, foldings, fractures, or high inclinations 

of the strata; no sudden changes of facies, and no gaps in the sedimentary 

series. The straightforward aspect of the stratigraphical relations, together 

with the characteristic lithological development of each individual member of 

the series, and the extraordinary wealth * of fossil remains, has rendered 

England the classic ground of the Jurassic system.

William Smith at first treated the successive strata as equal in rank, and 

although he afterwards (1815 and 1817) united them into groups, these were 

not well defined and underwent modifications before they were received into the 

literature. Conybeare and W. Phillips t22 ] comprised under the name of Oolitic 

series all the strata between the ferruginous sand (lowest Cretaceous) and 

the red marl (Triassic). The same geologists classified the Lias as an independent basal formation in the Oolitic series and sub-divided the Oolitic formation above the Lias into three groups the Lower Oolites, beginning with the

21 Zittel, K. A. von, History of geology and paleontology, pp. 497-502, 1901. 

f 22 Conybeare, Rev. W. D., and Phillips, William, Outlines of geology of England and 

Wales, pp. 59, 165-277, 1822.]
THE PERIOD A<ND EPOCH TERMS 63

marly sandstone and concluding with the Cornbrash; the Middle Oolites, embracing the rocks from the Kellaways sandstone to the Coralrag; the Upper 

Oolites, embracing the rocks from the Kimmeridge .Clay to the Purbeck marls 

and limestones [both inclusive]. * * * [Pages 497-498.]

/ In 1795, when Humboldt travelled through Bavaria and Switzerland on his 

way to Upper Italy, he described a thick series of limestones "between the 

old Gypsum (of the Zechstein formation) and the newer sandstone (Bunter 

sandstone)," both in the Pranconian Alps and the Swiss Jura Chain, and he 

applied the name of " Jura Limestone" to this massive development. Ami 

Bou6 in 1829 defined the stratigraphical position of the " Jura Limestone" 

more accurately; he limited the term to the limestone above the Lias and 

below the Wealden formation. In the same year Brongniart had selected the 

term Terrain Jurassique for the sedimentary deposits comprised within almost 

the same limits. * * * [Page 499.] 

In two memoirs, published 1832 and 1836, Thurmann gave an admirable

r exposition of the stratigraphy of the Bernese Jura. Voltz in Strasburg 

rendered willing assistance in identifying the fossils and determining the 

parallelism of the rocks with foreign equivalents.

, ? Thurmann distinguished the following sub-divisions in the Terrain Jurassique:

C. Upper Jurassic or Portland Group.

15. Portland Limestone with Eooogyra virgula, etc.

14. Kimmeridge Marl of Le Banne, very fossiliferous (Exogyra

virgula, Pteroceras Oceani, Mytilus Jurensis, etc.). 

i. B. Middle Jurassic. 

F (b) Corallian group. 

( 13. Astarte Limestone. 

12. Nerinea Limestone. 

\ 11. Coral Oolite. 

} 10. Coral Limestone. 

( (a) Oxford group.

9. Terrain a chailles.

^ 8. Oxford Clay and Kellaways Rock. 

A. Lower Jurassic or Oolite Group.

7. Dalle nacr6e (= Cornbrash?).

6. Calcaire roux sableux (=Forest Marble?) with Ostrea

Knorri.

^ 5. Great Oolite (Plagiostoma elongata, etc.). 

' 4. Marls with Ostrea aciiminata (=Fullers' Earth?). 

3. Compact Oolite. 

2. Ferruginous Oolite.

1. GrSs superliasique (marly Sandstone). * * * [Pages 

500-501.]

The General Survey of the OrograpMc and Geognostic Relations of NorthWestern Germany, a work published in 1830 by Friedrich Hoffmann, described 

the Jurassic succession in that district in greater detail than a previous 

contribution by Hausmann (1824). Roemer, Koch, and Dunker made the 

German Jurassic fossils the subject of palasontological monographs, and their 

results, taken in conjunction with the geological map and sections of Hoffmann, 

showed that the equivalents of the English Jurassic formations were well 

represented in North-Western Germany. Thus it seemed as if the English 

development of the Oolitic and Liassic formations could be regarded also as
64 GEOLOGIC TIME CLASSIFICATION

a standard for the leading features of the Terrain Jurassique in France, 

Switzerland, and North Germany. [Page 502.]

The present boundaries of the Jurassic (see accompanying chart) 

are as described in the foregoing quotation, except that geologists 

and paleontologists are not all in agreement as to whether the 

Rhsetic should be included in the Jurassic or the Triassic. The 

United States Geological Survey and many other authorities still 

include Rhsetic time in the Triassic period.

The name is derived from the development of the rocks in the 

Jura Mountains of France and Switzerland.

ST. von Albert!, 1834 (Beitragr zra einer Monographic des Buntcn SamtRsteins, 

Ulnscnellfcallcs, und Kenpers rand die Verbindnnjar dieser G-eMlde aa einer 

Formation, pp. 323 324 sand columnar section, forming pi. 2).

Whoever examines more closely the foregoing analysis and tabulates all 

the fossils of the three hitherto separate formations; whoever examines, further, the transition of the different forms one into the other, and, indeed, considers the entire structure of the mountains and the decidedly different character of the fossils of the Zechstein [late Permian] from those of the Lias 

[Lower Jurassic], will realize that the Bunter sandstone, Muschelkalk and 

Keuper are the result of one period, their fossils, to use E. de Beaumont's 

words, being the thermometer of a geological period; that their separation 

into three formations is not appropriate, and that it is more in accord with 

the concept of a " formation " to unite them into a single formation, which I 

shall provisionally name Trias.

The columnar section in the publication cited above divided the 

Triassic into (descending order) Keuper group, Lettenkohlen 

group, Muschelkalk group, and Bunter sandstone group, and gave 

in detail the lithologic description of each group and the fossils 

from many different horizons of each division. The fossils of each 

group are also listed in the text. The Lettenkohlen group is the 

lower part of the Keuper.

As shown by the accompanying chart, the Triassic period and 

system as generally recognized to-day correspond with this original 

definition, for Alberti included in the Keuper, and hence in the 

Triassic, the deposits later named Ehsetic (or Rhetian). Some 

geologists, however, especially the French, assign the B-hsetic to the 

Jurassic.

In America there are three facies of the Triassic, namely, (1) the 

marine facies of the Pacific coast, extending as far east as Idaho 

and Utah in early Triassic time; (2) the red beds continental facies 

of the Interior; and (3) the continental Newark facies of the 

Atlantic border.

The name is derived from the three divisions that were originally 

included in the period, as explained in the above quotation.
THE PERIOD AND EPOCH TEEMS 65

CARBONIFEROUS PERIOD (OR SYSTEM)

Some encyclopedias credit the first use in geology of the term 

Carboniferous to Kirwan's " Geological essays," 1779. Kirwan, 

however, did not use the term in a stratigraphic or time sense; but 

in view of the fact that his " Geological essays " is a very rare book, 

and difficult to obtain, the following brief quotation from it is here 

given, in order to show the sense in which he did use the term.

Richard Kirwan, 1770 (Geological essays, pp. 20O-291).

Chap. I, § 1. Of Carboniferous Soils and their attendant circumstances. 

By carboniferous soils I mean the various sorts of earth or stone among or 

under which coal is usually found. These soils are either chiefly argillaceous 

or arenilitic, or both together, or of the trap kind, or calcareous.

Rev. W. D. Conybeare and W. Phillips, 1822 (Outlines of the geology of 

England and Wales, pp. vil, 278, 32O-364).

A synoptical and comparative view of the arrangement proposed in the 

present work and those of former writers is subjoined.

Character

1. Formations (chiefly of sand & clay) 

above the chalk.

2. Comprising 

a. Chalk, 

b. sands & clays beneath the chalk. 

c. calcareous freestones (oolites'), & 

argillaceous beds. 

d. New red sandstone, conglomerate & 

magnesian limestone.

3. Carboniferous rocks, comprising 

o. Coal-measures, 

b. Carboniferous limestone, 

c. Old red sandstone.

4. Roofing slate, &c. &c.

5. Mica slate. 

Gneiss. 

Granite, &c.

Proposed names

Superior order.

Supermedial order.

Medial order.

Submedial order.

Inferior order.

Wernerian names

Newest floatz class.

Floetz class.

Other writers

Tertiary class.

Secondary class.

Sometimes referred to the preceding 

sometimes to the succeeding class by 

writers of these schools; very often the 

coal-measures are referred to the former 

 the subjacent limestone and sandstone to the latter.

Transition class.

Primitive class.

Intermediate class.

Primitive class.

[Page vii.]

BED MAKLE, OB NEW BED SANDSTONE 

[Permian and Triasslc of the present classification]

This Chapter will conclude our view of the formations above the great and 

important deposits of coal, and comprise the beds between the lias and those 

deposits: these are entirely referable to two formations very intimately connected together, viz. 1st. a series of marly and sandy beds intermixed with 

conglomerates derived from older rocks, containing gypsum and rock salt, 

and in one instance amygdaloidal trap: and 2ndly, a calcareous formation 

often brecciated and characterized by containing a considerable portion of
66 GEOLOGIC TIME CLASSIFICATION

magnesia: this lies beneath, or at least in the lower portion of the above 

series. The former deposits are commonly known by the name of Red marie 

or New -red sandstone; the latter as the Magnesian limestone. * * * 

[Page 278.]

MEDIAL OB CARBONIFEROUS ORDER

t> Chapter I

General view of the formations comprised in this order 

Section I. Introductory notice

It is intended to comprise, in the present book, an account of the rocks associated together in the districts which afford the principal deposit of fossilcoal, and indeed the only one capable of being applied to purposes of extensive 

utility which appears to exist in the whole geological series.

The class of rocks thus constituted will contain not only the great coaldeposit itself, but those of the limestone and sandstone also on which it reposes; which, though entitled to the character of distinct formations, are yet 

so intimately connected with the above, both geographically and geologically, 

that it is impossible to separate their consideration.

This series of rocks is by some geologists referred to the floetz, by others 

to the transition class of the Wernerians: we have preferred instituting a 

particular order for its reception, a proceeding justified by its proportional 

importance in the geological scale, its peculiar characters, and the many inconveniences arising from following either of the above conflicting examples. For 

this order we have proposed the name of Medial, wishing to adopt an appellation entirely free from theory, and indicating only the central place of this 

groupe in the five-fold division of the geological series which results from 

assigning to it a separate class. The epithet carboniferous is of obvious 

application to this series.

Had we been obliged to refer it either to the floetz or transition class of the 

Wernerians, we shoufd not have hesitated in preferring the latter branch of 

the alternative; since at least ten characters will be found in common between the carboniferous and transition class, for one which would lead to an 

opposite arrangement: for instance, 1st, in those countries (as England and 

the Netherlands) where all the beds above this series really deserve, from 

their generally horizontal position, the name of floetz rocks, the carboniferous 

strata are most frequently much inclined, and exhibit every variety of contortion and disturbance, agreeing in these respects with the transition rocks, 

but being entirely unconformable with the more recent. * * * [Pages 

823-324.]

The following general principles may be laid down, to guide us in our order 

of treating this subject. In the first place, the series of rock formations which 

ought to be considered together with coal-measures, should be taken as including the four following subordinate series. I. Coal-measures. II. Millstone grit and shale. III. Carboniferous or Mountain limestone. IV. Old 

red sandstone. These are so much associated together in the same districts 

(entering as component parts into the same chain of hills, &c.), that in describing any extensive tract of country, they must be kept together under the 

view, or an inextricable confusion will result. * * * [Pages 325-326.]
THE PERIOD AND EPOCH TERMS 67

Section II. Of the Coal-Measures, or Great CoakFormation

Preliminary remarks on the limitation of this term, and the relations of this 

and other carbonaceous deposits

In speaking of the coal-formation, we must be understood as applying that 

term emphatically to the great and principal deposit of that mineral, interposed between the newer red or saliferous sandstone, and the great carboniferous limestone and older sandstone formations; or, where these are 

absent, resting on transition rocks. This is the deposit distinguished by the 

Wernerians as the Independent coal-formation.

It may be useful here to observe that, besides this great deposit, thin seams 

of carbonaceous matter may be traced in several other geological positions, 

and that such are sometimes, though very rarely, sufficiently productive to be 

worked for fuel; yielding however generally a coal of very inferior quality. 

* * * [Pages 326-327.]

Section III. Millstone-grit and shale

(a) Chemival and external characters. The coal-measures generally repose 

on a series of beds which are usually designated by the name of Millstonegrit and Shale. The millstone-grit is most commonly seen under the form of 

a coarse-grained sandstone, consisting of quartzose particles of various sizes 

(often sufficiently large to give the rock the character of a pudding-stone) 

agglutinated by an argillaceous cement. This sandstone differs from those 

which accompany the coal-measures, principally by its greater induration. It 

has every appearance of a rock mechanically formed from the detritus of 

pre-existent materials; and rounded particles of felspar may occasionally be 

traced in it. It sometimes, however (though comparatively seldom), assumes a.finer texture, in which the mechanical structure becomes less evident, and even passes into a hard and solid cherty rock. * * * [Page 349.]

Section IV. Carboniferous or mountain limestone

(a) Chemical and external characters. The series jtist described reposes on 

that important assemblage of calcareous strata (occasionally alternating with 

beds of a different composition, e. g., shale-grit and amygdaloid) which has been 

often described by the name of mountain limestone, from its usually forming 

considerable hills; of metalliferous limestone, from its mineral riches; and 

of entrochal or encrinal limestone, from its organic remains. We prefer to 

all these that of carboniferous limestone, derived from its association in the 

coal districts, as expressing a character more constant and more peculiar than 

any of the former. * * * [Page 352.]

Section V. Old Red Sandstone

[Devonian of present classification]

The Carboniferous limestone is sometimes separated from this rock by a 

thick shale much resembling that associated with the millstone-grit; this may 

be distinguished as the lowei' limestone shale.

(a) Chemical and external characters. The old red sandstone is a coarsegrained, micaceous sandstone^ evidently of mechanical origin, constituted 

apparently of abraded quartz, feldspar and mica, and containing fragments 

of quartz, clay-slate, flinty-slate, &c.; sometimes passing into the state of 

a quartzose conglomerate, sometimes possessing a structure coarsely schistose 

(and thus affording slates for paving), and sometimes, particularly towards its

1146 25 6
68 GEOLOGIC TIME CLASSIFICATION

lower regions, becoming finely schistose, and passing into a fine-grained micaceous sandstone slate. It alternates with argillaceous beds, sometimes soft but 

more usually indurated and often slaty; the colour is usually dirty iron-red 

or dark brown, but sometimes passing into grey. It approaches in its lowest 

beds very nearly to the characters of the greywacke upon which it reposes, 

and indeed graduates insensibly into that rock; so that the line of separation 

between them is frequently only an imaginary and arbitrary1 demarcation. 

This rock contains in several places calcareous concretions, which produce a 

rock of a pseudo-brecciated appearance, known by the name of Comstone; and 

has also some unimportant beds of limestone subordinate to it.

The superior consolidation of many of the beds of this rock will generally 

serve to distinguish it without much difficulty from the newer red sandstone, 

when a tract of any extent is examined; for although doubt may often remain 

from the examination of a single quarry, more extensive observation of the 

general features of a district will seldom leave any. Rock formations usually 

bear external marks of their relative antiquity, which the eye of the experienced geologist readily perceives. It. is more difficult to distinguish this 

rock from the sandstones of the millstone-grit series, and those alternating 

with mountain limestone; and in fact it can only be considered as a lower 

link in the great chain of beds to which those belong; its prevalent and characteristic colour forms its best distinction. * * *

(c) Organic remains. It is generally destitute of organic remains; but 

towards its lower regions, where it approaches the limestone of the transition 

series, some beds of micaceous sandstone-slate occur, containing anomiae and 

encrinites similar to those in the transition limestone, which will be described 

hereafter. Vegetables similar to those of the coal are said in some instances 

to occur. [Pages 362-363.]

As thus defined the Carboniferous excluded the Permian rocks and 

included the " Old Ked sandstone." The rocks now known as Permian, together with the rocks now known as Triassic, were included 

in the " New Eed sandstone " and " Magnesian Limestone," which 

were said to overlie unconf ormably the Carboniferous in England 

and the Netherlands, and the " Old Red sandstone " was said not to 

have any sharp line of demarcation from the overlying Carboniferous 

limestones. The typical locality of the Carboniferous system of 

rocks is in the Pennine Range of England, and it is not fully represented in any other section of England. In the Pennine Range the 

"New Red sandstone" (a part of which belongs to the Permian) 

caps the " Coal Measures."

In 1839 the " Old Red sandstone " was, because of its fossil contents, excluded from the Carboniferous by Sedgwick and Murchison, 

and made a distinct system, under the name Devonian system. In 

1841 Murchison introduced the name Permian system for the rocks between the Triassic above and what was then called Carboniferous 

below. Although in England, Germany, and the Netherlands the 

Permian rocks usually unconf ormably overlie the " Coal Measures," 

in some sections of England and America there is no sharp division 

line between them, and in India their relations are so close that
69

William Waagen introduced the term "Anthracolithic" to include 

his Carboniferous and the Permian.

An examination of the chart will show that geologists do not 

agree in the use of the term Carboniferous, and that some would 

abandon the,name altogether. In America there is a widespread 

time break between the upper Mississippian and the Pennsylvanian, 

but this break is much greater in some areas than in others, and 

geologists are not agreed as to its time value. It is more frequently 

represented by the absence of early Pennsylvanian rocks than by 

the absence of late Mississippian beds. Whether the absence of the 

rocks is due to nondeposition or to erosion is not yet established. 

And whether this break represents a systemic boundary or a boundary of less importance is a debated question. , Many paleontologists regard the invertebrate fossils contained 

in the Mississippian, Pennsylvanian, and Permian rocks as constituting a major life unit, of the order of a period (or system), 

and comparable in rank to the Devonian life unit, although the 

rocks deposited during Carboniferous time are of much greater 

thickness than those deposited during Devonian time. Sonle other 

paleontologists would separate the Carboniferous into three life 

units, each of which they regard as of the rank of a geologic period 

(or system), but which the Survey classifies as of the rank of a geologic epoch (or series). Still others would separate the Mississippian 

into two geologic periods (or systems).

Regarding the invertebrate life of the Carboniferous rocks of 

America, paleontologists who use Carboniferous in the sense that 

the Survey uses it state that the early Mississippian invertebrates 

are naturally rather closely related to the late Devonian invertebrates, but that the late Mississippian (Chester) invertebrates are 

much more closely related to the Pennsylvanian invertebrates than 

they are to those of the late Devonian, and that there is a progressive evolution from the early Mississippian invertebrates to 

those of the late Mississippian; also that the Pennsylvanian invertebrates are closely related to but still distinct from the Permian 

invertebrates, which are without question more closely related to 

the Pennsylvanian invertebrates than they are to those of the succeeding Triassic period.

The Mississippian, Pennsylvanian, and Permian floras of America 

are reported to be related, but reasonably distinct. The late Mississippian (Chester), floras are more closely related to the Pennsylvanian floras than they are to the late Devonian floras, but the early 

Mississippian floras are rather closely related to the late Devonian 

floras, and the early Permian floras are more closely related to the 

Pennsylvanian floras than to those of the Triassic.
70 GEOLOGIC TIME CLASSIFICATION

Carboniferous rocks the world over are characterized by the abundance and great variety of brachiopods of the genus Productus. 

Brachiopods of this genus occur in all three subdivisions of the Carboniferous the Mississippian, the Pennsylvanian, and the Permian 

and they became extinct with the Permian epoch. Productus, therefore, is a reliable indicator that the rocks containing it are of Carboniferous age, but the genus alone does not determine to which epoch 

of the Carboniferous period they belong. It frequently happens that 

other evidence of the age of the rocks is not obtainable in the allotted 

time, and the most definite opinion the geologist or paleontologist 

can form, therefore, is that they are of Carboniferous age.

The meaning of Carboniferous is coal-bearing, from the Latin 

carbo (coal, carbon) and fero (bear). The Pennsylvanian rocks in 

many parts of the world contain large quantities of commercial coal. 

The Permian rocks of many regions also yield coal, and the Mississippian rocks of northern England, Scotland, and certain parts of 

the United States and other countries contain some productive coal 

seams.

PERMIAN EPOCH (OR SERIES) 

R. I. Mnvchisoii, 1841 (Pliilos. Mag-., 3d ser., vol. 19, p. 419).

The carboniferous system is surmounted, to the east of the Volga, by a 

vast series of beds of marls, schists, limestones, sandstones and conglomerates, 

to which I propose to give the name of " Permian System," because, although 

this series represents as a whole, the lower new red sandstone (Rotlie todte 

liegende) and the magnesian limestone or Zechstein, yet it cannot be classed 

exactly (whether by the succession of the strata or their contents) with either 

of the German or British subdivisions of this age. Moreover the British 

lithological term of lower new red sandstone is as inapplicable to the great 

masses of marls, white and yellow limestones, and gray copper grits, as the 

name of old red sandstone was found to be in reference to the schistose black 

rocks of Devonshire.

To this " Permian System " we refer the chief deposits of gypsum of Arzamas, of Kazan, and of the rivers Piana, Kama and Oufa, and of the environs of 

Orenbourg; we also place in it the saline sources of Solikamsk and Sergiefsk, 

and the rock salt of Iletsk and other localities in the government of Orenbourg, as well as all the copper mines and the large accumulations of plants 

and petrified wood, of which you have given a list in the " Bulletin " of your 

Society (anno 1840). Of the fossils of this system, some undescribed species 

of Producti might seem to connect the Permian with the carboniferous sera; 

and other shells, together with fishes and Saurians, link it on more closely 

to the period of the Zechstein, whilst its peculiar plants appear to constitute 

a Flora of a type intermediate between the epochs of the new red sandstone 

or " trias " and the coal-measures. Hence it is that I have ventured to consider this series as worthy of being regarded as a " System."

The overlying red deposits which occupy a great basin in the governments 

of Vologda and Niijni Novogorod, have not as yet been found to contain any 

organic remains except minute Cyprides and badly preserved Modiolse; but 

when we take into consideration their thickness, geological position, and 

mineral-characters, we are disposed to think that they may at some future day
THE PEKIOD AND EPOCH TERMS 71

be identified with a portion of the "Trias" of German geologists. I am 

strengthened in this opinion by Count Keyserling's discovering, during our 

tour at Monte Bogdo, certain fossils which are unknown in other parts of 

Russia, but which are associated with the Ammonites Bogdoanus already 

described by Von Buch, and which that distinguished geologist refers to the 

type of the muschelkalk.

R. I. Murchlson, E. de Verneuil, and A. von Keyserllng, 1845 (Geology of 

in Europe and the Ural Mountains, pp. 7° 8, 140 141).

* * * and thirdly, after describing a peculiar form of the carboniferous 

system and giving a detailed account of the coal-bearing tracts in the empire, 

by establishing under the name of " Permian " a copious series of deposits 

which form the true termination of the long palaeozoic periods.

This last-mentioned system has not hitherto obtained the attention to which 

it is entitled. In France it is known only as a deposit of red sandstone with 

a few plants; in Belgium it is a mere conglomerate (the " P6neen " or sterile 

group of M. d'Omalius d'Halloy). In England and Germany, where its members are much more expanded in the form of red sandstone and conglomerate, 

magnesian limestone, copper slate, etc., the strata have never received a collective name, nor have they till recently been united as a natural group,03 distinguishable from the inferior formations by peculiar species, though connected! 

with them by the general aspect of their fauna, and entirely different in all 

their organic contents from the overlying or triassic system.

Finding that this supracarboniferous group was not only spread over a region 

of enormous dimensions in Russia, extending from the Volga to the Ural 

Mountains on the east, and from the Sea of Archangel to the southern steppes 

of Orenburg, but that among certain fossils characteristic of the Zechstein in 

other parts of Europe, it also contained many new species of shells and a fauna 

somewhat differing from that of the carboniferous age, we have ventured to 

apply to it a collective name derived from the ancient kingdom of Permia, 

which was situated iu the centre of the vast territories overspread by these 

deposits. * * * [Pages 7*-8.]

Such then is our apology for the introduction of a new synonym, and in 

the ensuing chapters we shall support our reasons for its use. To render, 

however, the term Permian acceptable to German and English readers, we have 

placed the words Zechstein and Magnesian Limestone as equivalents in the 

Table and Map, thus to point out, that beds similar in structure to them, form 

part of the diversified " Permian System."

In our first announcement of this system we believed 24 that it might comprehend the rothe-todte-liegende of Germany; but we have since seen reason 

to modify this view, and to exclude (for the present) that German deposit 

from our Russian natural group. For, if the rothe-todte-liegende should be 

found to contain (and we believe this to be the case) some of the same species

23 Professor Phillips was the first to maintain, that the fossils of the magnesiaru limestone of England ought to be classed with those of the paleozoic rocks, and our Permian 

researches confirm his view.

24 See Murchison's letter to Dr. Fischer, Moscow, Sept. 1841, when, the term " Permian " 

was first proposed; also Phil. Mag. vol. XIX, p. 417. In suggesting this name, we had, 

we confess, forgotten that our distinguished friend M. D'Omalius D'Halloy had employed) 

the word " Pe"neen " to characterize all the strata between the " terrein houiller " and the 

" hunter sandstein." We adhere, however, to our geographical name, not only because 

it was adopted on the same principle which led to the use of " Silurian " and " Devonian ", but also from our having found to the Permian deposits undeseribed organic 

remains and much mineral wealth, (copper, sulphur, salt, etc.) ; thus rendering the worcB 

" P6neen " or " sterile " quite inapplicable in the present state of our knowledge.
72 GEOLOGIC TIME CLASSIFICATION

of plants as the coal-fields of the surrounding countries, that deposit must certainly be considered the representative of the Carboniferous system in that 

portion of Northern Germany, where no other coal-fields exist. At all events, 

English geologists have not yet been able to point out any natural distinctions 

between the plants of their Lower Red Sandstone and those of the subjacent 

coal measures; and as the identification of this red sandstone with the rothetodte-liegende has been admitted, we are compelled to avow, that a deposit 

.so characterized can form no part of a system in which the plants belong to a 

peculiar type. In a word, therefore, our Permian system embraces everything which was deposited between the conclusion of the carboniferous epoch, 

and the commencement of the Triassic series. [Pages 140-141.]

As stated in the preceding quotation, the name Permian is derived 

from the ancient kingdom of Permia, Russia, (See further explanation under Carboniferous period and Pennsylvanian epoch.)

PENNSYLVANIAN EPOCH (OR SERIES) 

H. S. "Williams, 1891 (Arkansas Geol. Survey Ann. Kept., vol. 4, p. xiii).

The formations of Washington County

System

Carboniferous) 

or Pennine. J

Devonian?

Silurian.

Series

Coal Measures

or Pennsylvanian (H. S.

Williams)

Lower Carbon-1 

iferousorMis-l 

sissippian (H.f

I S. Wms.) J

Group

Boston (Branner).

Qenevieve (H. 

S. Wms).

Osage (H. S 

Wms).

Approximate

Equivalence. 

(H. S.

Williams)

{

"Chester." 1 

"St. Louis." f

"Warsaw." J

("Keokuk." ) 

 {"Burling > 

{ ton. ' ' J

Washington County

Millstone grit.

Kessler limestone (Simonds) . Coal-bearing shale (Simonds). 

Pentremital limestone (Simonds) 

 Washington shale and sandstone

(Simonds). 

Archimedes limestone (Simonds) . Marshall shale (Branner) .

Batesville sandstone (Branner).

Fayetteville shale (Simonds) . Wyman sandstone (Simonds) . Boorre chert and limestone (Branner).

Eureka shale (Branner) .

(Sandstones).

The foregoing table contains the original use of Pennsylvanian. 

The term was introduced, as the table shows, as a geographic name to 

replace the descriptive term " Coal Measures." The book cited does 

not contain any further explanation of the term.

H. S. Williams, 1801 (U. S. Gcol. Survey Bull. 80, pp. 83-1O8).

Chapter IV. The Coal Measures or Pennsylvania [n] series. [Heading on 

p. 83.]

The term " Coal Measures " as in use in 1891 in Pennsylvania, the 

typical area of the Pennsylvanian series, included, in descending order, the following subdivisions: "Upper Barren Measures,"
THE PERIOD AND EPOCH TERMS 73

u Upper Productive Coal Measures," "Lower Barren Coal Measures," " Lower Productive Coal Measures," and Pottsville conglomerate ("Millstone grit"), the Pottsville resting on the rocks 

.1 commonly called "Lower Carboniferous." In the Mississippi 

Valley region the "Coal Measures" included the coal-bearing 

rocks above the Chester group (of Mississippian age). The 

" Upper Barren Coal Measures " of Pennsylvania are the Dunkard 

j group (Dunkard Creek series of I. C. White, 1891), and they contain 

some workable beds of coal. The Dunkard rocks are present only in 

, the southwestern part of Pennsylvania and in adjacent parts of Ohio, 

\ West Virginia, and Maryland. In 1880 they were, on the basis of 

) the fossil plants they contain, assigned to the Permian by Fontaine 

' and White.25 According to the statements on pages 81-82 and 108 

1 of Bulletin 80 of the United States Geological Survey, Williams 

excluded the Permian rocks from his Pennsylvania[n] series and 

'v4 included in it, at the base, the so-called " Coal Measure Conglom- 

\ erate or Millstone grit" (Pottsville formation of present usage). 

That is the definition adopted by the United States Geological 

Survey.

The division line between the Permian and Pennsylvanian in the 

United States is in general a purely paleontologic boundary, though 

i in some sections it seems to coincide with an unconformity. In most 

f areas its precise location remains to be determined.

^ MISSISSIPPIAN EPOCH (OR SERIES) 

\ 

/ A. Wlnchell, I860 M (Am. Philos. Soc. Proc., vol. 11, p. 79).

I propose the use of this term [" Mississippi group"] as a geographical 

0 -designation for the Carboniferous Limestones of the United States which are- 

! so largely developed in the valley of the Mississippi river.

H. S. Williams, 1891 (U. S. Geol. Survey Bull. 80, p. 135).

In the Mississippian province the sedimentation introducing the Carboniferous was strikingly different. A considerable series of limestones and calcareous 

f shales, and a few sandstones intervene between the termination of the Silurian 

 and the base of the coal-bearing strata above. These rocks contain rich and 

varied fossil faunas, and their correlation and classification constitute one of 

the most important chapters in American geology. Rocks containing Devonian 

faunas are found at the base of the series in some parts of the province, but 

in other sections they are missing. The formations resting upon the Devonian

» Fontaine, W. M., and White, I. C., The Permian, or Upper Carboniferous flora of West 

Virginia and southwestern Pennsylvania: Second Pennsylvania Geol. Survey Kept. PP 

\ 1880.

S

26 The date of publication of Wlnchell's paper has been variously slated. The paper 

was read March 5, 1869, and according to a footnote on page 245 of the American Philof -sophlcal Society Proceedings No. 83, volume 11 (which part of vol. 11 was published in 

1870), also according to a footnote on page 385 of volume 11, the first part of Wlnchell's 

paper (the part In which he proposed«the term "Mississippi group") appeared in No. 81 

of the Proceedings of the Society and was published in 1869.
74 GEOLOGIC TIME CLASSIFICATION

where these occur, and in other places upon the Silurian, are characterized ' 

by fossils of Carboniferous age, and have heretofore gone under the names 

" Mountain limestone," " Carboniferous limestone," " Sub-carboniferous," and 

" Lower Carboniferous." No one of these names is satisfactory, and as these 

formations are bound together by a common general fauna and constitute a 

conspicuous feature in the geology of this region, it is proposed to call them 

the Mississippian series. This series may be defined stratigraphically as that 

series of rocks, prevailingly calcareous, which occupies the interval between the 

Devonian system and the Coal Measures, and is typically developed in the 

States .forming the upper part of the valley of the Mississippi River, viz, 

Missouri, Illinois, and Iowa. The name is a slight modification in form 

and usage of a name proposed by Alexander Winchell in 1870 27 [1869].

(See explanation under Carboniferous period.}

" TENNESSEAN SYSTEM " 

E. O. Ulrich, 1911 (Geol. Soc. America Bull., vol. 22, pp. 531-582).

Revision of methods as well as facts of stratigraphic classification. It will 

have been observed that my revision affects the methods as well as the facts 

of stratigraphic correlation. By method, I mean the manner of determining 

what constitutes a geologic period or system, an epoch or series, or a stage or 

group, and, more particularly, how the boundaries of these time and stratigraphic divisions are to be drawn. Concisely stated, the method followed is to 

divide the stratigraphic sequence at the first plane beneath the introduction of 

a new fauna or beneath a marked faunal change that exhibits evidence of 

diastrophic movements. If the plane marks a great faunal break, providing 

the compared faunas invaded from the same oceanic basin, and especially when 

the plane corresponds also to a considerable change in the provincial boundaries 

that had prevailed during the greater part of the preceding period, then it 

seems to me it marks the beginning of a new system. It is on such grounds 

that the old Mississippian is divided into two systems the Waverlyan and the 

Tennessean also, that the Eopaleozoic is divided into four systems instead of 

but two.

Why the Waverlyan and Tennessean are systems and not series. A system 

is divided into series on similar grounds, only in these cases the breaks are 

commonly of a lower order and the change in provincial boundaries less extensive. We may illustrate the difference by comparing the relations of the 

Waverlyan to the Tennessean on the one hand and the interrelations of the 

series divisions of these two systems on the other. Thus, during the Waverlyan, the continental seas were- developed in southeastern North America in 

three fairly well distinguished basins or faunal provinces. Each of these provinces, furthermore, is characterized by its own lithological sequence. At times, 

also, the seas shifted so that only two or perhaps but one of the basins was 

submerged. Named from their characteristic formations, the eastern basin, 

with its shales and sandstones, may be called the Cuyahoga basin; the middle 

area, with its shales and cherty limestones, may be called the Fort Payne basin; 

the western province, with shaly beds beneath and at the top and rather pure 

crystalline limestone in the middle, may be called the Burlington province.

It may be questioned whether all three of these basins contained marine 

waters at any one time during this period. I believe this occurred during the 

Chattanoogan and, to a considerable extenf also, in the New Providence-Fern

a The Marshall group, etc., Am. Phil. Soc., Proe., vol. 11, p. 79.
THE PERIOD AND EPOCH TERMS 75

Glen-upper Cuyahoga age, and again in the Keokuk-Fort Payne-Logan-Grand 

\ Falls age. The point is not of vital importance here. It is enough to know 

' ' that, as a rule, the Waverlyan seas occupied considerable parts of at least two 

of the basins, and that the greatest shifting during the period occurred at times 

marking the close of the series into which the system is divided. Thus, as 

shown in the Waverlyan correlation table, the Chattanoogan ends with its most 

widely distributed stage; the Kinderhookian is characterized by frequent oscillations and ends with its smallest (Chouteau) stage; the Osagian begins with 

the extensive Fern Glen stage, continues with the restricted Burlington stages, 

and ends with another eastward tilt, during which the Keokuk was deposited1 

k in Iowa and Illinois, the Grand Falls in Missouri and the cherty Fort Payne 

limestone in areas to the southeast of these States.

As indicated, the Waverlyan oscillations merely shifted the seas about within

the area covered by the three basins. The movements consisted almost entirely

of simple tilting of the area as a whole. The break between the Keokuk and

the Warsaw stage of the succeeding Tennessean period, however, is marked

i less by tilting than by warping of the surface. The Warsaw, and to a greater

extent the Spergen, disregarded the boundaries of the faunal and lithological

' provinces which prevailed during the Waverlyan and spread with surprising

uniformity of expression from Missouri to Alabama and thence northeastward

in the Allegheny basin to west Virginia and perhaps to Maryland. There was

a change, also, in the northward extent of the seas, none of the Tennessean

stages reaching as far in that direction as did certain Waverlyan formations.

In short, a new set of conditions was introduced in southeastern North America

with the Warsaw that thereafter prevailed with minor oscillations and tilt-

} ing to the close of the Chesterian.

"WAVERLYAN SYSTEM" 

I C. Brisks, Jr., 1838 (Ohio Geol. Survey First Ann. Uept., pi. 1, pp. 74, 79-SO).

/ WAVERLY [ALSO WAVEELEY] SANDSTONE SERIES

The rocks superimposed upon the argillaceous slate (vide D, fig. 4, of the 

plate) appear to have been deposited under conditions no less remarkable than 

the two preceding divisions. Instead of the uniformly tranquil state of the two 

preceding periods ["Great limestone deposit" overlain by 200 to 300 feet of 

" Argillaceous slaty rock, or shale stratum "], the strata bear evidence of having 

been formed in waters alternately quiet and disturbed. Under these circumstances, were deposited the whole series of this division, which consists of alternate layers of fine-grained sandstone and shale, attaining a thickness of not less 

than three hundred feet. The layers of sandstone appear to have been formed 

in a gradually shoaling bay, estuary, or sea, for they are characterized by 

ripple marks, which, it has been stated by Mr. Conrad, can only be made in 

shallow waters. These markings are sometimes so surprisingly regular and 

' beautiful as to appear artificial, rather than natural, slightly resembling the 

flutings on some ornamental columns. But in proof of this, reference need 

only be made to the aquatic vegetables which are found on the surfaces of 

some of the layers; and which were apparently entombed in the place of their 

growth. [Pages 74 to 75.]

Superimposed upon the stratum above described [200 to 300 feet of "Argillaceous slaty rock, or shale stratum"], occurs a series of alternations of sandstone and shale, the thickness of which has not yet been ascertained, but which 

will not probably vary far from 250 to 300 feet. The lower part of this
76 GEOLOGIC TIME CLASSIFICATION

stratum caps the highest elevations near Chillicothe, and it can be studied 

with great advantage on either side of the Scioto valley, from Chillicothe to 

Portsmouth. * * * The fine grained sandstones of this series have been 

quarried at Portsmouth, Piketon, Waverley, Chillicothe, and other places; and 

are favorably known in most of the principal towns in the State. Quarries 

without number may be opened, so that all demands, however great, may be 

supplied. The limits within which these quarries may be opened, will be determined by subsequent detailed surveys.

As some of the most beautiful stones that have been obtained were quarried 

at Waverly, we may, for the present, denominate these rocks the Waverly 

sandstone series.

CONGLOMERATE

Resting on the series last described [Waverly Sandstone Series], occurs a 

stratum which is composed of siliceous sand and pebbles; it varies in thickness, 

where it has been observed, from 40 to 80 feet. [Pages 79 to 80.]

E. O. Ulrich, 1911 (Geol. Soc. America Ball., vol. 22, pp. 581-583, pi. 29).

[See quotation under " Tennessean system"]

For many j^ears the following was generally accepted as the correct sequence of the Mississippian and late Devonian formations of 

Ohio, in descending order:

Maxville limestone.

Logan formation (top formation of Waverly group).

Black Hand formation.

Cuyahoga formation.

Sunbury shale.

Berea grit.

Bedford sTiale (bottom formation of Waverly group).

Cleveland shale.

Chagrin ("Erie") formation. =0hio shale.

Huron shale.

Briggs's report, from which the foregoing original definition of 

Waverly is quoted, covered an area in southern Ohio that included 

" the counties of Scioto, Lawrence, Gallia, Athens, Hocking, and 

Jackson," and during the course of their field work he and his assistants extended their observations into Pike, Ross, Adams, and Highland counties. According to later reports of the Ohio State Survey 

the Waverly rocks of the area covered by these counties include at 

the top the Logan formation; they are underlain by the black Ohio 

shale, and are overlain in some places by the Maxville limestone and 

in other places by the Pottsville rocks.

The base of the Waverly and the boundary between the Mississippian and the Devonian are still debated questions. Briggs's 

original definition of the Waverly placed its lower limit at the top of 

the black to gray slaty argillaceous rocks which, according to Orton, 

were later named Ohio shale. In 1870 Newberry drew the base of the 

Waverly of northern Ohio at the base of the black Cleveland shale,
THE PERIOD AND EPOCH TERMS 77

which has long been believed by many geologists to correspond to the 

upper part of the Ohio shale of southern Ohio. Newberry's 

boundary was subsequently followed by Read (1873,1878), Winchell 

(1874), TJlrich (1911), and Bassler (1911). Orton, however, in 

1879 excluded the Cleveland from the Waverly and drew the base 

of the Waverly at the base of the Bedford shale. In this he was 

followed by Prosser (1901, 1903, 1905, 1912, 1915), Stauffer (1909, 

1911), Hubbard and Bownocker (1911), Hyde (1912), Morse and 

Foerste (1912), Stout (1916), Burroughs (1913), and other geologists. Herrick in 1893 expressed the opinion that the Berea grit " is 

the real floor of the [Waverly] series." In 1911 Ulrich, for the 

reasons given in the quotation under " Tennessean system," elevated 

the Waverly to the rank of a system the " Waverlyan system " 

the base of which he placed at the base of the Cleveland shale, and 

the top at the base of the Maxville limestone, which he included in 

his Tennessean system. He divided his Waverlyan system into (descending order) Osagian, Kinderhookian, and Chattanoogan. With 

the Osagian he correlated the Logan, Black Hand, and upper part of 

the Cuyahoga; with the Kinderhookian he correlated the lower and 

major part of the Cuyahoga; and with his Chattanoogan he correlated the Sunbury, Berea, Bedford, and Cleveland. Subsequent 

studies, however, led him, in 1912, to publish the following as the 

true sequence of the early Mississippian and late Devonian rocks of 

Ohio:

Waverlyan system: 

***

Berea grit. 

Bedford shale. 

Cleveland shale.

Olmsted shale (new name suggested by Chadwick). 

Huron shale. " Most probably younger than Chagrin." 

Devonian:

Chagrin formation.

In 1912 Girty, also Kindle, assigned the Bedford fauna to the 

Devonian. The same year Prosser expressed himself as undecided 

whether the Bedford fauna belonged to the Devonian or the Carboniferous, but stated that the evidence favored drawing the Carboniferous-Devonian boundary at the base of the Berea grit. 

Kindle's studies also led him in 1912 to the conclusion that the 

Huron shale and basal part of the Cleveland shale are contemporaneous with the Chagrin formation. In 1916 and 1917 Verwiebe 

placed the Mississippian-Devonian boundary at the unconformity at 

the base of the Berea. In 1921 Butts published the opinion that the 

Bedford shale is of Kinderhook age, and in this opinion Ulrich also 

concurs.
78 GEOLOGIC TIME CLASSIFICATION

Because of the differences of opinion regarding these matters the 

United States Geological Survey classifies the Bedford sha.le as 

Devonian or Carboniferous.

"ANTHRACOLITHIC "

Waagen's definition of " Anthracolithic," a term' synonymous 

with Carboniferous as used by the United States Geological Survey, is given below.

William Waagren, 1891 (Salt Range fossils: Palieoiitolosia Imlicn, ser. 13, 

vol. 4, pt. 2, p. 241).

The two systems [Carboniferous and Permian] must be kept separate. 

At the same time, however, it is very desirable that the intimate connection 

between the two systems should also find an expression in the nomenclature. 

This can only be done by comprising the two as a group of a higher order 

under one name. The term " carboniferous" cannot here be used again, as 

with this the old confusion [meaning the different senses in which Carboniferous had been used] would again be sanctioned; and yet the most characteristic feature of the two systems is the frequent occurrence of coalseams. Thus, I venture to propose for the whole, for the Carboniferous and 

Permian systems together, the name " Anthracolithic Epoch" * * * My 

" Anthracolithic Epoch " corresponds now to Neumayr's " Upper Palaeozoics."

The word is derived from the Greek av6pa% (coal) and Xi0os 

(stone).

DEVONIAN PEBIOD (OR SYSTEM)

Rev. A. Sedgrwick and R. I. IHnrchison, 1S39 (Geol. Soc. London Proc., vol. 3, 

No. 63, pp. 121-123, abstract).

A paper was then read on the classification of the older rocks of Devon' 

shire and Cornwall, by the Kev. Professor Sedgwick, F. G. S., and Roderick 

Impey Murchison, Esq., F. G. S.

In a communication read in 1837 [and published in 1840 M ], the authors explained their general views respecting the older rocks of Devon and Cornwall, 

but having recently changed one part of their classification, they have 

hastened to place their reasons for doing so upon record, before the Geological 

Society. On three out of four of the essential points in their former communication, the authors' views remain unchanged; they adhere to the belief, 

which they were the first to put forth, that the greater portion of Devonshire 

belongs to the true carboniferous system, and that the succession and lithological characters of the different mineral masses in North and South Devon, 

which they then pointed out, remain unaltered. In proof of this there were 

suspended, during the reading of the paper, the same sections as were exhibited at Bristol in 1836. The change, therefore, which they propose, is to 

remove the lowest rocks from the Cambrian and Silurian systems to the old 

red; and their reason for making this alteration is founded on zoological 

evidence recently obtained, which shows that the organic remains of these deposits are of a peculiar character, approaching in the upper division, the 

fossils of the carboniferous strata, and in the lower, those of the Silurian 

system; as well as upon the previously ascertained regular sequence or pas-

. Soc. London Trans., new ser., vol. 5, pt. 3, pp. 633-687, 1840.]
THE PERIOD AND EPOCH TEEMS 79

sage from the carboniferous strata, through all the subjacent series of 

deposits.

The fossil plants of the culm basin having been formerly determined to be, 

as far as recognizable, true coal measures remains, and the deposit having 

been therefore assigned to the era of the carboniferous system, the order of 

superposition being also clear, the strata underlying the coal basin might 

naturally be referred to the old red sandstone, if the organic remains found 

in them, belonged to a natural group, intermediate between the fossils of the 

carboniferous and Silurian systems. Subsequent examination has proved that 

such is the case, but this distinction could not have been ascertained had not 

Mr. Murchison published his work on the Silurian system. * * *

The authors next gave an approximate list of the fossils, collected by themselves or placed at their disposal by the Rev. R. Hennah, Major Harding, and 

the Rev. D. Williams, referring them to the great mineral groups to which they 

belong, both in North and South Devon. * * *

South Devon. Having thus shown that in North Devon there is a regular 

succession of strata characterized by distinct fossils differing more and more 

in descending order .from the organic remains of the mountain limestone, ana 

approaching those of the Silurian system; the authors pi-oceed to enumerate 

the order of the groups and the imbedded fossils in South Devon and the North 

of Cornwall. They show a similarity of succession of deposits and of organic 

remains in the upper groups, but they state that in consequence of the protrusion of the granite, there is in the lower a considerable difference in mineral 

type, especially south of Dartmoor. They refer, however, to their former 

memoir for ample details respecting these counties, and for proofs that they 

were correct in placing the great calcareous masses of Plymouth and Chudleigh 

on the same parallel as the lowest calcareous strata of North Devon.

In conclusion, the authors show, that the variation in Devonshire and Cornwall from the ordinary type of the old red sandstone in Herfordshire and 

adjoining counties, cannot be admitted as a valid argument against assigning 

the slates and sandstones of these counties to that system, because the variations in composition of other formations within limited areas is equally great. 

They show also that the absence of the true carboniferous limestone in Devonshire cannot disprove their present classification, because in Western Pembrokeshire that limestone is wanting, and the coal measures rest on older formations.

In consequence of mineral character being no longer indicative of age, and 

the term greywacke being lithologically applicable to beds of every class of 

rocks, and as Devonshire affords the best type of the fossils of this intermediate 

system, the authors propose to substitute the term Devonian for old red sandstone; and they hope that the organic remains, discovered in that county, will 

enable continental geologists to detect in their own country, a system of strata 

hitherto supposed to be almost peculiar to the British Isles.

The authors acknowledge the assistance they have received from Mr. J. 

Sowerby; and that Mr. Lonsdale first suggested, from their fossil contents, 

that the limestones of S. Devonshire might prove to be the representatives of 

the old red sandstone.

Rev A. Sedgwick: and R. I. Marclilson, 1840 (Geol. Soc. London Trans., 3d 

ser., vol. 5, pt. 3, pp. 7O1-7O2; read April 24, 1839).

Though the term old red sandstone, when designating great groups of rocks 

like the Cornish killas and Devonian slates should involve no error of classification, still it would, mineralogically, be most inappropriate. We purpose 

therefore, for the future, to designate these groups collectively by the name 

Devonian system, as involving no hypothesis, and being agreeable to analogy.
80 GEOLOGIC TIME CLASSIFICATION

Thus the terms Carboniferous system, Devonian system, Silurian system, and 

Cambrian system, will represent a vast and apparently uninterrupted sequence 

of deposits; each having, as a whole, zoological and (often also) mineralogical 

characters of its own, yet each passing into the system next in order by almost 

imperceptible shades of difference. The old palaeozoic rocks appear, therefore, 

notwithstanding their enormous scale, and the wide diffusion of the same 

organic types, to have been formed in subordination to the same laws which, 

in after periods, produced the more clear succession of our secondary formations.

SILURIAN PERIOD (OB SYSTEM)

R. I. Mnrchison, 1835 (London and Edinburgh Philos. Mag-, and Jour. Sci., 

3d ser., TO!. 7, pp. 46-52).

The names finally adopted, and which will be incorporated in a work now in 

preparation on this subject are,

1. Ludlow rocks, divided into upper and lower Ludlow rocks, with a central 

zone of limestone: in this formation no change of name is proposed.

2. Wenlock limestone and shale (equivalent, Dudley).

3. Caradoc sandstones. This name, supplying the place cf the Horderley 

and May Hill rocks, has been derived from the striking and well-known ridge 

of Caer Caradoc, on the eastern flanks of which, and lying between it and the 

Wenlock Edge, are exhibited those peculiar strata which are the equivalents 

of the shelly sandstones of Tortworth.

4. Llandeilo flags (preferred to "Builth and Llandeilo"). When this table 

is reprinted, there will naturally be found many additions to the organic 

remains, some identifications of British with foreign species, and numerous corrections.

Notwithstanding the adoption of these names, there was still required a comprehensive term by which the whole group could be designated, and at once 

distinguished from the old red sandstone above, and the slaty rocks below. * * * [Page 47.]

To return, however, to the system under review, I was urged by leading 

geologists both at home and abroad to propound an entirely new name for it. 

In consonance, therefore, with those views which have rendered the names 

used by English geologists so current throughout the world, I venture to 

suggest, that as the great mass of rocks in question, trending from south-west 

to north-east, traverses the kingdom of our ancestors the Silures, the term 

" Silurian system " should be adopted as expressive of the deposits which lie 

between the old red sandstone [above] and the slaty rocks of Wales [Tremadoc 

slate and Lingula flags], including, as above detailed, the Ludlow, Wenlock, 

Caradoc, and Llandeilo formations. One of the largest of these formations, 

to which, indeed, the Llandeilo flags are frequently subordinate, has been 

named after the bold and picturesque ridge of Caer Caradoc in Shropshire.

I further propose that the system be subdivided into " Upper " and " Lower 

Silurian rocks," the former embracing the deposits of " Ludlow " and " Wenlock," the latter those of "Caradoc" and "Llandeilo." [Pages 48-49. For 

explanation of the formation names see column by A. Geikie in accompanying 

chart]

As thus defined the Silurian included the rocks later separated 

and named Ordovician. Until within recent years the rocks in the 

United States known as the Eichmond group were considered to be 

the top subdivision of the Ordovician, but some geologists now con-
THE PERIOD AND EPOCH TERMS 81

sider the Richmond rocks and fauna more closely related to the 

Silurian than to the Ordovician, and include them in the Silurian, 

for both faunal and diastrophic reasons. The United States 

Geological Survey and other authorities have, however, not yet 

removed the Richmond from the Ordovician.

Some authors use the name " Ontario system " instead of Silurian 

system. (See definition below.)

"ONTARIO SYSTEM" '

E. Emmoiis, 1842 (Geology of New York, pt. 2, div. 4, Geol. 2d dlst., pp. 

100-1O1, 429).

Following out the plan of nomenclature for the rocks of New-York, I have 

considered that, for purposes of study, they [the rocks of the New-York Transition System] might be arranged in four groups, as follows: Champlain group, 

at the base of the Transition system; Ontario group, comprehending the rocks 

which lie upon its southern border for about fifteen or twenty miles; the 

Helderbergh series; and lastly, the Erie group, which completes the whole of 

the system, extending up to the old red sandstone. * * * The valley of 

Lake Ontario, at its southern extremity, is excavated out of the shales, sandstones and shaly limestones which compose the Ontario group. * * * The 

Ontario group is well developed all along the southern shore of that lake, particularly at Rochester, Lockport, and on the Niagara river. * * * [Pages 

100-101. On page 429 the Ontario group is defined as underlying the Helderberg series (including at base the Pentamerus [Coeymans] limestone), as 

overlying the Champlain group, and as including Manlius limestone at top 

and Medina sandstone at base.]

As above defined the term " Ontario group " is essentially synonymous with Silurian system of present usage.

J. D. Dana, 180O (Geol. Soc. America Bull., vol. 1, pp. 40-41).

The Upper Silurian may conveniently take a new name, but it is not necessary to go for it to the same little land of Wales that has supplied the two, 

Cambrian and Silurian, in honor of Sedgwick and Murchison. We may better 

look elsewhere for the third name. There is the land of Bohemia, where 

Barrande worked out his Silurian and Primordial systems, and there is the 

area of New York and Canada where were laid the foundations of American 

Paleozoic geology, and where our honored president, James Hall, has carried 

on his paleontological labors.

The term Bohemian has been already used for the Upper Silurian by the 

French geologist, M. de Lapparent, in his Treatise of 1883. The name Ontarian 

is suggested by the actual use of the term " Ontario Division " for the lower 

portion of the Upper Silurian by Mather, in his New York Geological Report 

of 1843, and by Emmons, in his Report of 1846. And it is in its favor that 

Upper Silurian rocks prevail over much of Ontario, Canada.

Cambrian, Silurian, Ontarian, would make a satisfactory triplet. Whatever 

name shall be adopted for the Upper Silurian, the working ground of Barrande, or that of Hall, Billings, and others should some way be recognized, 

and to this even the distinguished author of the term Ordovician would not, I 

am sure, enter his dissent.
82 GEOLOGIC TIME CLASSIFICATION 

J. M. Clarke and C. Schnchert, 1899 (Science, new ser., vol. 1O, pp. 875-876).

[Ontario or Siluric era, or system is defined, in the table, as including all 

rocks between the top of the Manlius limestone and the base of the Oneida 

 conglomerate or Shawangunk grit.]

Ontario. Vanuxem placed the base of the Ontario division at the "gray 

sandstone," Hall and Emmons at the [base of the] Medina, Mather at the 

Shawangunk grit. Vanuxem and Hall terminated the division above with the 

Niagara, Emmons included the Salina and waterlime. Any rational grouping 

of these formations must recognize as its base the predominance of coarse sedimentation installing a new cycle. Growing evidence fully endorses Emmons' 

view as to the termination of the group and period with the clearing of the 

Salina sea.

"ALEXANDBIAN SERIES"

T. E. Savage, 1908 (Am. Jour. S«i., 4th ser., vol. 25, pp. 433-434, 442-443).

MIDDLE SELTJBIAN SYSTEM

Alexandrian. The beds referred to this formation are exposed in Alexander 

county to a thickness of 44 feet. They include the Cape Girardeau limestone 

and the overlying beds containing Dalmanites danae and Whitfieldella 'billingsana. The Cape Girardeau limestone is well exposed about two miles south of 

Thebes, in the bank of the river and along the streams in that immediate 

vicinity. It is also seen in a cut along the Illinois Central railroad, and in the 

river's bank, one and one-half miles north of Thebes. In the former locality 

this limestone is nearly 40 feet thick, and consists of black, fine-grained, brittle 

limestone, in thin layers which are often separated by narrow partings of dark, 

calcareous shale. This zone has a rich fauna which appears abruptly at this 

horizon. [Fossils listed.]

At the exposure north of Thebes the Cape Girardeau limestone rests directly 

upon the fossiliferous blue shale (26 of section). This member is succeeded by 

a bed of dark gray limestone, oolitic in the upper part. [Fossils listed.]

There are here no diagnostic fossils of the Richmond. The genera Favosites, 

Stromatopora ; Atrypa, Whitfieldella, Homceospira, Schuchertella and Clor-inda 

do not occur in American Ordovician strata, while Atrypa rugosa and Lichas 

l>reviceps clintonensis are indicative of the Silurian. On the other hand, the 

fauna is not directly related to that of the Clinton, from which formation it 

is separated by a marked erosional unconformity. Schuchert 00 cites a fauna 

from Edgewood, in eastern Missouri, collected by Ulrich, which corresponds 

closely with the above. Since there seems to be no direct time equivalent of 

these beds in the Ordovician or in the Silurian as generally defined, the horizons 3a to Be are classed as Middle Silurian strata that more or less completely 

bridge the lost interval between the Cincinnatian and the Clinton. For these 

beds the time term Alexandrian is proposed, from Alexander county, Illinois, 

where they are well exposed; the term to have the same rank as Cincinnatian, 

which it immediately follows.

On pages 442-443 of the volume cited above the rocks of southwestern Illinois are classified as follows:

Devonian system: 

* * *

Helderbergian. 

A long break in sedimentation.

20 Jour. Geol.,, vol. xiv, pp. 728, 729, 1906.
THE PERIOD AND EPOCH TERMS 83

Upper Silurian or Silurian system:

Niagaran. Correlated with Clinton-Dayton, Ohio Clinton,[ 80 ] Interior 

or Western Clinton. 75 ft. [Details of beds given and fossils 

listed.]

A short break in deposition. 

Middle Silurian system: 

Alexandrian:

3c. Coarse-grained, somewhat oolitic limestone, in layers 12-.1& 

inches thick. Atrypa rugosa, Rhynchotreta sp., Schuchertella subplanus, Whitfieldella billingsana, and Liclias 

breviceps clintonensis are common. 3% ft. 

3b. Fine-grained, dark colored shaly limestone, in layers 4-10 

inches thick, characterized by Rafinesquina mesacosta, 

Schuchertella subplanus and DalmanUes danai. 21/£ ft. 

3a. Cape Girardeau limestone: Fine-grained, black, brittle limestone, layers 1-4 inches thick, separated from each other 

by thin lenses or partings of calcareous shale on the surface of which are exposed Crinoids, Rafinesquina mesacosta, Rhynchotrema sp., Schuchertella missouriensis and 

Cornulites tenuistriata, etc. 33-38 ft. 

A probable short break in sedimentation. 

Lower Silurian or Ordovician system: 

Cincinnatian:

Richmond-Maquoketa. 91 ft.

ORDOVICIAN PERIOD (OR SYSTEM) 

C. Lapworth, 1S79 (Geol. Mag., London, new ser., vol. 6, pp. 12 14).

So long as present systems of nomenclature survive, nothing can disturb the 

application of the title of Cambrian to the rocks of the Primordial Series, and 

that of Silurian to the strata of the Third Fauna. In these systems, as thus 

restricted, the most perversely ingenious partisan could scarcely find room for 

controversy. Within these limits the labours of their respective founders were 

comparatively perfect and complete, and the propriety and harmony of their 

original classifications, though slightly modified in detail by subsequent research, has never been impugned, either by friend or foe. It is vastly different, however, as we have seen, with the intermediate system. From the day 

it was recognized until now, it has been the object of incessant disputes. Its 

co-discoverers both committed the gravest of errors, regarding either its proper 

limits, its relationships, or the sequence and fossils of its component formations. It has been the subject of almost as much passionate argument as the 

Wernerian theory itself; * * *

North Wales itself at all events the whole of the great Bala district where 

Sedgwick first worked out the physical succession among the rocks of the intermediate or so-called Upper Cambrian or Lower Silurian system; and in all 

probability much of the Shelve and the Caradoc area, whence Murchison first 

published its distinctive fossils lay within the territory of the Ordovices; a 

tribe as undaunted in its resistance to the Romans as the Silures. It was indeed the last of the old British tribes to yield to their invincible legions; and

[ 80 In 1913 (Geol. Soc. America Bull., vol. 24, pp. 111-112, 351-376) Savage transferred to his Alexandrian series the " Ohio Clinton " or BrassfleJd limestone, and placed 

its top at the base of deposits of the age of the true or typical Clinton of New York. The 

thickness of the included strata aggregates 140 feet in Illinois.]
84 GEOLOGIC TIME CLASSIFICATION

it is consequently quite as well worthy of scientific commemoration as the 

Silures themselves.

Camden thus refers to the Ordovices: * * * "To the Ordovices belonged 

those countries which are now called in English by new names Montgomeryshire, Merionethshire, Caernarvonshire, Denbighshire, and Flintshire."

Here, then, have we the hint for the appropriate title for the central system 

of the Lower Palaeozoics. It should be called the Ordovician system, after 

the name of this old British tribe.

Whatever arguments may be adduced in support of the term Silurian will 

apply equally well, or even with greater force, to this new title. Like the term 

Silurian, it is classic in origin, but at the same time thoroughly British. It is 

equally euphonious, and far more strictly significant of the geographical area 

where its strata are typically developed. Indeed, the employment of the one 

title almost of itself necessitates the adoption of the other; for only in this 

way is it possible to recognize the systematic equality of the two systems in 

their very designations the one receiving its name from the ruling tribe in the 

south of Wales, the other from the dominant tribe in the north. If there is 

anything specially becoming in commemorating the warlike tribe of the Silures 

in the name of a geologic system, how strikingly appropriate is the title of 

Ordovician in erecting a similar scientific monument to the last and most 

valiant of the old Cambrian tribes.

On this arrangement the Lower Palaeozoic Rocks of Britain stand as 

follows: 

(c) SILURIAN SYSTEM: Strata comprehended between the base of the 

Old Red Sandstone [Devonian system] and that of the Lower 

Llandovery. 

(b) ORDOVICIAN SYSTEM : Strata included between the base of the Loioer

Llandovery formation and that of the Lower Arenig. 

(a) CAMBRIAN SYSTEM: Strata included between the base of the Lower 

Arenig formation and that of the Harlech Grits. * * *

For explanation of the foregoing terms see Geikie's classification 

on accompanying chart.

This original definition of Ordovician includes in the Cambrian 

the Tremadoc slate, which according to Ulrich's 1914 classification 

is of Beekmantown age, but which he now (1924) regards as probably 

representing his Ozarkian system. All American geologists classify 

the Beekmantown as post-Cambrian, and until 1911 it was universally 

included in the Ordovician. In 1911 Ulrich 31 proposed the restriction of Ordovician by the separation of the major part of the Beekmantown as an independent system, for which he employed the name 

" Canadian system." In the same publication he also proposed to 

restrict the Cambrian as previously used in the United States, by 

combining the remaining (lower) part of the Beekmantown and beds 

which he states were erroneously correlated with the upper part of 

the Cambrian, including the Potsdam sandstone of New York, into 

another independent system, for which he proposed the name 

" Ozarkian" as explained in the quotation under that name.

n Ulrlch, B. 0., Revision of the Paleozoic systems: Geol. Soc. America Bull., vol. 22, 

pp. 647-680, pi. 27.
THE PERIOD AND EPOCH TEEMS . 85

Some authors prefer the name " Champlainic system " or " Champlainian system" to Ordovician. (See definition on p. 88.)

CTNCINNATIAN EPOCH (OR SERIES)

F. B. Meek and A. H. Worthen, 1865 (Acad. Nat. Sci. Philadelphia Proc., 

vol. 17, p. 155).

As it is now acknowledged that the rocks along the Hudson river valley, 

to which the name Hudson River Group has been applied, belong, as long 

maintained by Dr. Emmons, to a different horizon from the so-called Hudson 

River rocks of western New York, and the states farther westward, it seems 

to be an awkward misnomer to continue to apply the name Hudson River 

Group to these western deposits. Hence it is certainly desirable that this 

group should receive some appropriate and generally applicable name. Its 

subdivisions, it is true, have already received various lithological names, such 

as "Utica Slate," "Frankfort Slate," "Lorraine Shale," &c.; but as each of 

these names will probably be always directly associated, in the minds of 

geologists, with the particular subdivision to which it was originally applied, 

while neither of them is applicable to the lithological characters of the whole 

series, we cannot, without creating confusion, so extend its signification. It 

has recently been proposed to designate this series as the "Green and Blue 

Shales and Limestones;" this, however, is not a name, but descriptive 

phrase, and has the disadvantage of being based upon lithological characters 

not everywhere characteristic of these beds.

In view of all the facts, we have concluded to propose the name Cincinnati 

Group (which will be adopted in the forthcoming reports of the Illinois 

Geological Survey) for this series. This name possesses the advantage of 

being equally applicable to rocks of any color or composition, while it carries 

the mind to a well-known locality, where the formation referred to is extensively developed, and its fossils so abundant that they have been thence widely 

distributed, both in this country and Europe. Consequently, geologists will 

everywhere at once understand to what particular horizon of the Lower 

Silurian this name refers.

In the early definitions of " Hudson River group " the Utica slate 

was excluded from it and its top was limited by the base of the 

Oneida conglomerate or Shawangunk grit. In 1851 Hall transferred 

the Utica slate to the " Hudson River group." Dana, however, continued to exclude the Utica, as indicated in the editions of his textbook up to and including the edition of 1895.

N. H. Winch ell and E. O. Ulrich, 1897 (Minnesota Geol. and Nat. Hint. Survey Final Rept., vol. 3, pt. 2, pp. cl cv).

Hudson River or Cincinnati period. Under this term we include all the rocks 

lying between the top of the Trenton and the base of the Upper Silurian. 

Space is wanting, nor are we fully prepared to give all our reasons for preferring the term Cincinnati for the period instead of Hudson River group 

or period, Hudson terrane, or that oldest name of them all, the " Gray Sandstones and Shales of Salmon River" as described and named by Conrad In 

1837, in his first report on the geology of the third district of New York. For 

the present it will be sufficient to say that our preference is dominated by a 

sense of its utility and fitness. There is no other locality on the continent that 

deserves so well to be considered the typical locality for the series of strata
86 GEOLOGIC TIME CLASSIFICATION

in question as the region about Cincinnati, Ohio. All the groups into which 

the period may be divided are well represented there, and when it comes totheir faunas and the facilities for collecting fossils, there is no other region 

in America where the fossils are so plentiful and so easy to obtain. Throughout this volume, however, and in all the Minnesota reports the term Hudson 

River has been used, and it is only from a sense of consistency that it is 

placed first in our title. The following subdivisions of the rocks of the " Hudson River or Cincinnati period " were made, enumerated in descending order :

Richmond group.

Lorraine group.

Utica group.

J. M. Clarke and C. Sclmcliert, 1809 (Science, new ser., vol. 10, pp. 876,

877).

Ontaric or Siluric era or system : 

* * *

Oswegan period or group (Paleontaric) : 

Medina sandstone. 

Oneida conglomerate. 

Shawangunk grit.

Champlainic era or system (Lower Silurian and Ordovician) : 

Cincinnatian period or group (Neochamplainic) : 

& Richmond beds (Ohio and Indiana). 

Lorraine beds. 

Utica shale.

Mohawkian period or group (Mesochamplainic) : 

Trenton limestone. 

Black river limestone. 

Lowville limestone.

Cincinnatian. The formations of the Neochamplainic are not as completely 

developed in the State of New York as in Ohio and Indiana. In the latter 

sections the Lorraine fauna is represented, but is followed above by the welldefined fauna of the Richmond beds. Probably in no other region is the succession of these faunas so complete as about Cincinnati, and this fact justifies 

the recognition of the term Cincinnatian, which already has historic value. 

For a full description of the series by Winchell and Ulrich, see Geol. and Nat. 

Hist. Stirv. of Minn., vol. 3, pt. 2, pp. ci-cv, 1897.

The United States Geological Survey employs the term 

natian series as a provincial name for the Upper Ordovician series, 

and ascribes to it the same limits as those given by Winchell and 

Ulrich in 1897 and by Clarke and Schuchert in 1899.

MOHAWKIAN EPOCH (OR SERIES) 

James Hall, 1842 (Am. Jour. Scl., 1st ser., vol. 42, p. 52).

Thus according to the report just quoted, and which in fact gives a very 

accurate account of the rocks of the state [of Ohio], we have in Ohio 

only two limestone formations, whereas in New York we have three very important ones, with some minor beds. These are, 1st. The limestone along 

the Mohawk valley, the principal member of which is termed by Mr. 

Vanuxem, the " Mohawk limestone," a name which with much propriety
THE PERIOD AND EPOCH TEEMS 87

might be applied to the whole mass, forming the Mohawk group. This would 

include the Mohawk, Birdseye, and Trenton limestones, and the calciferous 

sandrock [Beekmantown] might also be included as the lower member of 

the group. 2d. The Niagara group.

As above defined the term " Mohawk group " included the Middle 

Ordovician and the Lower Ordovician of present usage. The name 

"Mohawk system" had previously been applied by Conrad to all 

rocks between the base of the Rochester shale and the base of the 

Potsdam sandstone.

J. M. Clarke and C. Sclinchert, 1899 (Science, new ser., vol. 10, pp. 876,

877^.

Mohawkian Jteriod or group (Mesochamplainic) : 

Trenton limestone 

Black river limestone 

.. Lowville limestone (instead of Birdseye limestone of common use).

Conrad and Vanuxem made use of the term " Mohawk limestone " for certain 

of the calcareous layers beneath the Trenton, but they differed so widely in 

their application of the term that in the summation of their results, the 

geologists decided to abandon it. The name is here revived with a broader 

meaning. [See chart, last column.] The valley and watersheds of the 

Mohawk river afforded typical exposures of all members of the group.

The United States Geological Survey employs the term Mohawkian 

series as a provincial name for the Middle Ordovician' series, and 

ascribes to it the same limits as those given above by Clarke and 

Schuchert that is, from the base of the Lowville.limestone to the 

top of the Trenton limestone.

"CANADIAN PERIOD (OR SYSTEM)"

J. D. Dana, 1874 (Am. Jour. Sci., 3d ser., vol. 8, p. 214). ,

Canadian Period. The fact of the existence of an important Lower Silurian 

formation in Canada, near Quebec, abounding in fossils, arid of about the age 

of the Calciferous sand-rock and the Chazy limestone, is mentioned, in the first 

edition of this work, as one of the discoveries of the Canadian Geological 

Survey, under Sir William Logan. The Reports of the Survey point out the 

close relations in fossils of the Calciferous sand-rock, Quebec group, and Chazy, 

and their rather wide separation from the overlying Trenton limestone, showing 

that they represent, naturally, a distinct period in the Lower Silurian era. 

This is called the Canadian, because the rocks are well displayed in Canada, 

and there the most important part of the facts respecting it were first brought 

to light.

J. D. Dana, 1875 (Manual of geology 2d ed., pp. 142, 163, 182).

Lower Silurian: 

Trenton period: 

Cincinnati. 

Utica. 

Trenton.
8* GEOLOGIC TIME CLASSIFICATION

Canadian period:

Chazy epoch. (Chazy limestone of New York, Canada, etc. 

Part of the crystalline limestone of the Green Mountains in 

Vermont and to the south.)

Quebec epoch. (Levis formation, Canada, near Quebec; Taconic 

slates of Green Mountains; shales, limestones and sandstones, 

Newfoundland. Part of the Knox group, Tennessee.) 

Calciferous epoch. (Calciferous sandrock in New York. Lower 

Magnesian limestone of the Mississippi valley; St. Peters 

sandstone of Wisconsin and Illinois; Knox sandstone, East 

Tennessee; thick limestones (part of the so called Quebec 

group) of Newfoundland.) 

Primordial or Cambrian period: 

Potsdam. 

Acadian. 

Archaean period.

The rocks of the extensive Quebec group were first distinguished and described in Canada by Canadian geologists, and all the subdivisions are well 

represented there; and hence the period Is named the Canadian.

J. M. Clarke and C. Schuchert, 1899 (Science, new ser., vol. 1O, pp. 876,

877).

Champlainic era or system (Lower Siluric and Ordovioian) : 

Cincinnatian period or group. 

* * *

Mohawkian period or group: 

Trenton limestone. 

Black River limestone. 

Lowville limestone.

Canadian period or group. This term has the prestige of time and 

priority.

Chazy limestone. 

Beekmantown limestone 

Cambric or <Taconic era or system: 

Potsdamian. 

Acadian. 

Georgian.

E. O. Ulrlch, 1911 (Geol. Soc. America Bull., vol. 22, pi. 27, pp. 647-679).

Ordovician period or system. * * * [Includes Chazy limestone.] 

Canadian period or system:

Beekmantown (Comprising Divisions E, D, C, and part of B).

Tribes Hill limestone. [Shown as in part contemporaneous with 

lower part of Beekmantown divisions mentioned and in part older.] 

Ozarkian period or system.

" CHAMPLAINIC SYSTEM »

E. Emmons, 1842 (Geology of New York, pt. 2, div. 4, Geology of the 

second district, pp. 10O-1O1, 1O2-126, 429).

As the rocks which constitute the lower part of the mass of the [New York] 

Transition system have hitherto received very little attention, it became necessary not only to investigate with great care their characters and relation, but 

also to provide them with suitable names. After having given them the attention and care they seemed to require, I have, with little hesitation, concluded that they belong *o but one group. Although there is a great diversity
THE PERIOD AND EPOCH TERMS 89

in the lithological character, still the fossils appear to belong to but few 

types, and to those which are strictly related to each other. In this single 

group, the fossils appear to be allied; but when we leave the upper member, 

and pass to the Medina sandstone, we find a distinct change in the character 

of the fossils. * * * The name which appeared the most appropriate to 

this group, is derived from the lake along which they are so well developed, 

(I refer to Lake Champlain) ; hence it becomes the Champlain group. * * * 

[Page 100.] The valley of Lake Champlain is excavated out of the Champlain group. [Page 101.]

The " Champlain group " is defined, on the pages cited above, as 

composing the basal group of the " New York system," as overlying 

the " Taconic system " and underlying the " Ontario group," and 

as including Potsdam sandstone, " Calciferous sandrock," Chazy and 

" Birdseye " limestone, marble of Isle La Motte, Trenton limestone, 

Utica slate, Lorraine shale, " Grey sandstone," and " Conglomerate." 

As thus defined it includes the upper part of the Cambrian of present 

usage, all of the Ordovician, and possibly some rocks that are now 

classified as Silurian.

J. M. Clarice and C. Schuchert, 1899 (Science, new ser., vol. 1O, pp. 875, 876).

Champlainic era or system (Lower Silurian and Ordovician). This most 

appropriate designation was introduced by the concurrence of the four geologists [Mather, Emmons, Vanuxern, and Hall] for the formations here [see chart, 

last column] assigned to it (exclusive of the Potsdam sandstone), and it has 

clear right of way over the later application of the name to the period of postglacial alluvium. That the later term has become ingrained in literature 

renders it all the more conspicuous as an infraction of the law and of the 

rights of the men who first proposed it. In the face of Champlain, 1842, the 

term Ordovician has no standing.

Some authors use the term " Champlainian " for the middle part 

only of the Ordovician that is, for the Mohawkian epoch plus the 

Chazy.

PROPOSED OZARKIAN SYSTEM OF E. 0. ULRICH

E. O. TJlrich, 1911 (Geol. Soc. America Bull., vol. 22, pp. 548, 627-629, 640, 643, 

pi. 27).

The Ozarkian system as developed in the southern part of the Appalachian 

Valley, comprises the various magnesian limestone formations which succeed 

the last of the upper Cambrian shales and thin limestones, and precede the 

Canadian limestone, or,-where that is absent, the Stones River limestone of 

the Ordovician system. The whole of this sequence of dolomites and magnesian 

limestones is commonly referred to a single great formation the Knox dolomite. However, this composite Knox varies greatly from place to place in its 

thickness and in the age of the beds contained in it. * * * [Page 548.]

Under the term Ozarkian system I include all the formations in the Appalachian Valley that can be shown to be younger than (1) the top of the upper 

Cambrian Nolichucky shale in northeastern Tennessee and (2) the top of the 

Conasauga shale in southeastern Tennessee, northwestern Georgia, and northeastern Alabama and which are older than the base of the Stonehenge limestone of the Canadian system [Beekmantown group, exclusive of division A 

and part of division B] in southern and central Pennsylvania. Wherever I
90 GEOLOGIC TIME CLASSIFICATION

have seen the contact with the underlying upper Cambrian shale or shaly 

limestone evidence of interrupted sedimentation was noted. * * * The top 

of the system also is everywhere in unconformable relations to succeeding 

deposits.

The most convincing part of the evidence on which it is claimed that an 

important stratigraphic hiatus separates the upper Cambrian in the southern 

half of the valley from the overlying Ozarkian lies in the greatly varying age 

of the beds forming the base of the latter in different localities. Occasionally, 

as in River Ridge, 3 miles northwest of Morristown, Tennessee, the Copper 

Ridge chert rests on the Nolichucky. More commonly the Knox begins with an 

older division 300 to 700 feet thick, while in the vicinity of Montevallo, Alabama, three still older formations, aggregating at a maximum something near 

2,500 feet of dolomite, intervene between the base of the typical Knox and the 

top of the Conasauga. The hiatus between the two systems, therefore, represents locally in east Tennessee over 3,000 feet of known calcareous deposits 

laid down elsewhere in Tennessee and in central Alabama. Even this great 

thickness of lower Ozarkian deposits does not fully measure the time break, 

for a gap is still indicated between the Brierfield dolomite at the base of the 

new system and the top of the upper Cambrian. [Page 628.]

* * * Though much thinner than the Appalachian record, the Missouri 

section makes a more satisfactory type because here the rocks are more fossiliferous and the stratigraphic sequence, in an epitomized way, more complete.

Derivation of the name and the type section. For reasons mentioned the 

term Ozarkian, a modification and restriction of the name " Ozark series," 

suggested by Broadhead some years ago (American Geologist, vol. viii, 1891, 

p. 33) seems highly appropriate. Broadhead was the first to use the geographic 

name Ozark as a stratigraphic term. * * * [Pages 628-629.]

In Missouri, then, the Ozarkian comprises all beds younger than the Elvins 

and older than the base of the Canadian system represented in north Arkansas 

by the Yellville dolomite. [Page 629.]

The Ozarkian in the iipper Mississippi ^Valley. In the upper part of the 

Mississippi Valley the Ozarkian includes four long established formations, 

namely, (1) the Mendota dolomite, (2) the Jordan sandstone (Madison sandstone of Wisconsin), (3) the Oneota dolomite, and (4) the Shakopee dolomite, 

the last including the New Richmond sandstone, which is thought to indicate 

an introductory clastic phase of the Shakopee rather than a distinct formation. * * * [Page 640.82 ]

The Ozarkian is represented in New York by the Potsdam sandstone, the 

Theresa passage beds, the Hoyt limestone, and the Little Falls dolomite. 

* * * [Page 643.]

As thus originally defined, and shown on Plate 27 of the book 

cited, the proposed Ozarkian system included, in its typical area, the 

following formations, named in descending order:

Jefferson City dolomite. 

Roubidoux formation. 

Gasconade dolomite. 

Proctor dolomite. 

Eminence dolomite. 

Potosi dolomite.

[s2 For Ulrich's present views on this and other sections see pp. 91-92.]
THE PEEIOD AND EPOCH TERMS 91

In the dpper Mississippi Valley it included, in descending order:

Shakopee dolomite (including New Richmond sandstone). 

Oneota dolomite.

Jordan sandstone (then supposed to be equivalent to Madison sandstone). 

Mendota dolomite.

In New York it included, in descending order:

Little Falls dolomite. 

Hoyt limestone. 

Theresa formation. 

Potsdam sandstone.

In 1915, after further field studies, Ulrich changed 83 the top of 

his Ozarkian system in its typical region to the top of the Gasconade, transferring the overlying Roubidoux and Jefferson City 

formations to his proposed Canadian system; and the top of the 

Gasconade is where he now (1924) places this boundary in Missouri. 

Further work in the upper Mississippi Valley has led him (unpublished chart) to place the top of his Ozarkian in that region 

at the top of the Oneota dolomite, and he now assigns the overJying Shakopee to his Canadian system.. He also now includes in 

the base of the proposed Ozarkian a recently discovered sandstone, 

to which he has applied 34 the name Devils Lake sandstone, and 

which he considers younger than the true Jordan sandstone. The 

Jordan was formerly erroneously considered to be the same as the 

Madison sandstone, which underlies the Oneota, but is now determined by him to be Upper Cambrian. 34

The rocks Ulrich now includes in his Ozarkian in the southern 

Appalachian region remain as described in his original definition, 

and those now included in it in New York remain unchanged, with 

the exception that some thin beds above the Little Falls dolomite 

are now included (unpublished chart).

The following is Ulrich's present (1924) classification (unpublished manuscript) of the formations originally included in his 

Ozarkian system:

Ozark region, Mo. (type area) :

Jefferson City dolomite ] ,_ , n Roubidoux formation jNow known to be middle Canadian. 

Gasconade dolomite=upper Ozarkian. 

Proctor dolomite=middle Ozarkian. 

Eminence dolomite ] _ Potosi dolomite } =lower OzarkianM As recorded by R. S. Bassler in U. S. Nat. Mus. Bull. 92, pi. 1, 1915. 

84 Ulrich, B. 0., Major causes of oscillations: Washington Acad. Sci. Jour., vol. 10, No. 

3, pp. 73-78, 1920.

1146 25 7
92

Upper Mississippi Valley:

Shakopee dolomite= upper Canadian (New Richmond sandstone

local development and disregarded). 

Oneota dolomite=upper Ozarkian. 

(Middle Ozarkian absent.) _ Madison sandstone. (The Jordan is not the -lo^ver Ozarkian and 

same as Madison sandstone but last of ~ Llttle Falls dol°"

Upper Cambrian.) . Mendota dolomite stone' and Potsdam

mite' ^ liniestone' and Potsdam 

sandstone of New Devils Lake sandstone New " York: Vnrlr xorK' 

Little Falls dolomite 

Hoyt limestone A , _ Theresa formation ^A11 lower OzarkianPotsdam sandstone

Ulrich has in preparation a monographic description of his proposed Ozarkian system and its fauna.

CAMBRIAN PERIOD (OR SYSTEM)

Rev. A. Sedgrwick, 1835 (Edinburgh New Philos. Jour., vol. 10, p. 390, 

August 14; abstract).

Mr. Murchison and Professor Sedgwick gave a lucid and most interesting 

account of their views regarding the older rocks of England and Wales, endeavoring to point out their subdivisions, so as to complete the series from the 

old red sandstone to the oldest slate rocks of Cumberland. Mr. Murchison 

treated of that part of the subject relating to the deposits which occur between 

the old red sandstone and the slaty rocks of Wales. This group of rocks has 

been termed by Mr. Murchison the Silurian System, and has been studied by 

him during the last five years in Herefordshire, Shropshire, Radnorshire, 

Brecknockshire, Monmouthshire, and Caermarthenshire. The detailed results 

of these important investigations will soon be given to the public in the work 

by Mr. Murchison, which is now in preparation. Professor Sedgwick explained 

the conclusions he had deduced from his elaborate and extensive examination 

of the greywacke, or slate series, of the north of England and Wales. Professor 

Sedgwick divides the old transition series into three groups, viz. the Lower 

Cumbrian [Cambrian], consisting chiefly of slates, and containing no organic 

remains; the Middle Cumbrian, composed of slates, conglomerates, and porphyries, and containing fossils; and the Upper Cumbrian, which contains much 

limestone, is fossiliferous, and approaches the lower beds of Mr. Murchison's 

Silurian System.

Rev. A. Sedgwick, 1836; read Ang-inst, 1835 (British Assoc. Adv. Sci. Rept. 

5th meeting-, pp. 5& <J1).

On the Silurian and Cambrian Systems, exhibiting the order in which the 

older Sedimentary Strata succeed each other in England and Wales. By 

Professor SEDGWICK and R. I. MTJBCHISON, V. P. 0. S.

Mr. Murchison described a great group of fossiliferous deposits which rises 

out from beneath the old red sandstone. To these rocks, which he has 

termed in descending order the IsuMow, Wenlock, Caradoc, and Llandeilo 

formations, (each distinguished by peculiar organic remains, and frequently by 

subordinate limestones,) it was found essential to assign a comprehensive
THE PERIOD AND EPOCH TERMS 93

term, since they constitute one natural system interpolated between the old red 

sandstone and the slaty rocks of Wales. He observed that it was well known 

to all practical geologists, that in consequence of the recent advances of the 

science, it was absolutely imperative that the term " transition," under which 

such rocks would formerly have been described, should now be abandoned, since 

it had been so used, both by Continental and English writers, as to embrace 

the whole carboniferous series, from which the system under review was not 

only separated by the vast formation of the old red sandstone, but was 

specially to be distinguished by its fossil contents. Urged, therefore, by many 

geologists to propound an entirely new name for the class of rocks which had 

engaged his attention during the last five years, Mr. Murchison recently suggested (see Lond. and Edinb. Phil. Mag., July 1835, p. 48.) that the group 

should be termed the " Silurian System," the name being derived from the 

ancient British people, the Silures, who under Caractacus made so noble a stand 

against the Romans, and within whose territory the rocks under consideration 

are fully displayed. Mr. Murchison then pointed out, that wherever the limestones and typical characters of particular formations were absent or obscure, 

it was alw£,ys practicable, over a region of 120 miles in length, extending 

from the neighborhood of the Wrekin and Caradoc hills, in Shropshire, to the 

west coast of Pembrokeshire, to separate the groups into two parts, the 

"Ludlow" and "Wenlock" formations, forming the "Upper Silurian," the 

" Caradoc " and " Llandeilo" the " Lower Silurian rocks." He further remarked, that in South Wales he had traced many distinct passages from the 

lowest member of the "Silurian system " into the underlying slaty rocks, now 

named by Professor Sedgwick 'the " Upper Cambrian."

This communication was illustrated by Ordnance Maps extending over large 

parts of eleven counties, coloured in the field by Mr. Murchison.

Professor Sedgwick commenced by pointing out the imperfection of the 

sections exhibited in the North of England, and some portions of North 

Wales, in consequence of the entire want of continuity between the carboniferous series and the inferior schistose groups. Some of the latter are 

fossiliferous both in Denbighshire and Westmorland; but in the interrupted 

sections of those counties it is impossible to tell how many terms are wanting to complete the series to the old red sandstone and carboniferous limestone. In the country described by Mr. Murchison these difficulties do not 

exist, and his sections have filled up a wide chasm in the succession of British 

deposits. Professor Sedgwick then described in descending order the groups 

of slate rocks, as they are seen in Wales and Cumberland [Tremadoc slate and 

Lingula flags], *To the highest he gave the name of Upper Cambrian group. 

It occupies the greatest part of the chain of the Berwyns, where it connected 

with the Llandeilo flags of the Silurian system, and is thence expanded 

through a considerable portion of South Wales. In one part of its course it 

is based on beds of limestone and calcareous slate; but on the whole it contains much less calcareous matter than the Silurian system, and has fewer 

organic remains. Beds of good roofing-slate occur, and a perfect slaty cleavage is often observed in it transverse to the stratification; but other parts 

of it are of a coarse mechanical texture. To the next inferior group he gave 

the name of Middle Cambrian. It composes all the higher mountains of 

Caernarvonshire and Merionethshire, and abounds in fine roofing-slate, alternating with, and apparently passing into, irregularly interstratified masses of 

porphyry. Some portions of it are coarse and mechanical, and it contains 

(for example, at the top of Snowdon,) a few organic remains, and a few examples of highly calcareous slates, but no continuous beds of limestone. The
94 GEOLOGIC TIME CLASSIFICATION

same group, with the same mineral structure, and in the same position, but 

without organic remains, is greatly developed in Cumberland. The Lower 

Cambrian group occupies the S. W. coast of Caernarvonshire, and a considerable portion of Anglesea: it consists chiefly of chlorite schist, passing 

here and there into mica schist and slaty quartz rock, and contains subordinate 

masses of serpentine and white granular limestone. It contains no organic 

remains. Beneath the Middle Cambrian system (above described) there occurs in Cumberland (for example, Skiddaw Forest,) a great formation of darn 

glossy clay slate, without calcareous matter, and without organic remains, it 

passes in descending order into chiastolite slate, mica slate, hornblende slate, 

gneiss, etc., which rest immediately on granite. Whether the Lower Cainbrian was to be placed on the exact parallel of these masses in Skiddaw 

Forest, the Professor did not determine.

Professor Sedgwick explained the mode of connecting Mr. Murchison's 

researches with his own, so as to form one general system. He pointed out 

also the limit, as at present known, of fossils, none having been hitherto 

discovered in the Lower Cambrian schists, and remarked in reviewing the 

general phaenomena, that geological epochs were not effected by shocks, but, 

like everything in nature, \\ere under the dominion of the usual laws of 

causation.

These original definitions of Cambrian included in the Lower 

Cambrian some Archean rocks, and in the Upper Cambrian much 

of the Ordovician of present usage. Subsequent studies, however, 

led to the separation from the Cambrian of the Archean and Ordovician rocks, and to the restriction of the term Cambrian to beds 

characterized by the trilobite genus Paradoxides in what was then 

supposed to be Lower Cambrian, by the trilobite genus Olenellus in 

what was then supposed to be Middle Cambrian, and by the trilobite 

genera Olenus and DicellocepJiaLus in the Upper Cambrian. As 

work on the Cambrian rocks progressed, geographic names' were 

sought for the three subdivisions or series into which the Cambrian 

was divided. Thus the name Potsdam came to be applied 8B to the 

rocks containing the Dicellocephalus fauna, Georgian to the rocks 

containing the Olenellus fauna, and Acadian to the rocks containing 

the Paradoxides fauna.

Owing, however, to the fact that for many years the relations of 

the rocks containing the Paradoxides fauna to those containing the 

Olenellus fauna were misunderstood, not having anywhere been 

found in the same section, the Paradoosides fauna was supposed to 

occur in rocks older than those containing the Olenellus fauna. 

Thus it happened that the Olenellus-\)Q8irmg rocks at Georgia, Vt. 

(the type locality of the "Georgian" Series), were originally supposed to be of Middle Cambrian age, Upper Cambrian fossils having 

been found higher in the section in northern Vermont, but no Paradoxides having been found.

35 Walcott, C. D., The Cambrian faunas of North America: U. S. Geol. Survey Bull. 30, 

1886.
THE PERIOD AND EPOCH TERMS 95

In 1886, therefore, Walcott,38 following the classification made by 

Sir William Logan in 1864, assigned to the Middle Cambrian the 

Olenellus zone, which had been found characteristically developed at 

Georgia, Vt., and applied to it the geographic name Georgia, a name 

that Hitchcock had in 1861 applied to the slate formation at Georgia, 

Vt., which was supposed to be the same as the rocks yielding the Olenellus fauna. The discovery in Sweden, however, of Olenellus kjerulfi 

beneath the Paradoxides zone led Walcott to restudy the Cambrian 

rocks of New York and finally to go, in the summer of 1888, to Newfoundland, where a more complete section of the Cambrian was, 

believed to exist. Manuel's Brook, Conception Bay, Newfoundland,, 

furnished the sought-for section, and definitely settled the relations; 

of the Paradoxides and Olenellw faunas in America. The conform- 

 able succession of rocks at that place proved beyond question that 

the Olenellus fauna is older than the Paradoxides fauna. Walcott, 

therefore, in 1888 87 published the following classification of the 

Cambrian system:

Upper Cambrian (Dicellocephalus or Olenus fauna), represented in

America-by the Potsdam: and other terranes. 

Middle Cambrian (Paradoxides fauna), represented by the St. John,

Avalon, arid Braintree terranes. 

Lower Cambrian (Olenellus fauna), represented by the $eorgia and other

terranes.

In 1891 Walcott 38 modified the name Georgia to Georgian.

The name Potsdam (also Potsdamic) continued to be applied to 

the Upper Cambrian series in America .until 1903, when Walcott 

replaced it by the geographic term " Saratogian," for the reasons 

stated on a later page, in the quotation under " Saratogan " epoch. 

Unfortunately the name Saratoga was found to be preoccupied by a 

Cretaceous chalk in Arkansas, and in 1912 Walcott withdrew " Saratogan " and replaced it with St. Groixan series, the present adopted 

name for the Upper Cambrian epoch or Dicellocephalus and Olenus 

zone. The rocks in the Saratoga region are now regarded by Wal- 

,cott and Ulrich as younger than the typical Upper Cambrian of the 

British Isles.

Dawson's name Acadian is still the approved name for the Middle 

Cambrian epoch or Paradoxides zone.

Walcott's name Georgian continued to be applied to the Lower 

Cambrian epoch or Olenellus zone until 1912, when, because of the

38 Op. clt.

87 Walcott, C. D., The stratlgraphical succession of the Cambrian faunas in North 

America: Nature, vol. 38, p. 551, 1888.

38 Walcott, C. D., The Cambrian group of rocks in North America: U. S. Geol. Survey 

Boll. 81, 1891.
96 GEOLOGIC TIME CLASSIFICATION

varied usage of the name and the conflict with the formation that :, 

had been named Georgia slate by Hitchcock in 1861, Walcott with- . (, 

drew Georgian and replaced it by the present accepted name Waucoban, as explained under Waucoban epoch.

Eecent detailed studies of the Georgia slate region of Vermont by 

Arthur Keith have proved that the typical Georgia slate is of Or- > 

dovician age (probably either Blac.k Kiver or Trenton), and the 

rocks of that region that have been called " Georgia shales," " Geor- I 

gia formation," and "Georgian or Lower Cambrian series" have 

recently yielded fossils of Upper, Middle, and Lower Cambrian ages, 

and have been separated by him into several distinct formations, for 

which new names have recently been introduced. 39

The type locality of the Cambrian system is, as explained in the 

early definitions, the ancient area of Cambria, in North Wales,, 

where, according to Walcott, " the Middle and Upper Cambrian 

faunas occur, and the strata corresponding in position to those con- ' 

taining the Lower Cambrian fauna in America are found beneath 

the Middle Cambrian Zone.''

"SARATOGAS" EPOCH (OR SERIES)

(Discarded name for Upper Cambrian) 

C. D. Walcott, 19O3 (Jour. Geologr, vol. 2, pp. 31&-319).

NEW TEEM FOR THE UPPER CAMBRIAN SERIES I

During a recent revision of the classification of Cambrian formations, in J 

connection with the nomenclature and classification to be used in the geologic \ 

atlas of the United States, it became apparent that the term " Potsdam " or 

"Potsdamic" could no longer be retained as the series name to include the 

various formations referred to the Upper Cambrian. It was used in this sense 

by me in 1891,40 but this usage has led to confusion, owing to the term " Potsdam " being retained for the well-known Upper Cambrian sandstone about the 

Adirondack mountains. In order to avoid further confusion, the term Soratogian is now proposed to include the various formations composing the Upper 

Cambrian series, leaving the term " Potsdam " restricted to its original application, the Potsdam sandstone. We shall then have the terms " Georgian " 

 (Lower Cambrian), "Acadian" (Middle Cambrian), and " Saratogian" *, 

(Upper Cambrian) for the three series of "formations of the Cambrian system.

The type locality of the Saratogian is north and west of Saratoga Springs, 

N. Y. The section has, at the base, about 200 feet of evenly bedded, compact, 

'grayish to yellowish colored sandstone, that rests unconformably against or 

upon spurs or ridges of pre-Cambrian gneiss. At a locality three miles north 

of Saratoga Springs the sandstone is about 40 feet in thickness; it is overlain :

88 Keith, Arthur, Cambrian succession of northwestern, Vermont: Am. Jour. Sci., 5th 

ser., vol. 5, pp. 97-139, 1923. 

40 Bull. U. S. Geol. Surv.,, No. 81, p. 380.
THE PERIOD AND EPOCH TERMS 97

by an oolitic limestone, 30 feet, and a dark gray, evenly bedded limestone 50 

feet in thickness. In this latter limestone the following fauna occurs: 

Cryptozoa, proliferum Billingsia saratogensis 

Obolus (Lingulepis) acuminatus Matthevia, variabilis 

Platyceras minutissimum Dikelocephalus hartti 

Platyceras hoyti Dikelocephalus speciosus 

Metoptoma, cornutiforme Ptychoparia calcifera 

Metoptoma simplex (A.) saratogensis

The Calciferous formation of the New York section rests conformably on the 

Upper Cambrian limestone.

The formations now referred to the Saratogian are as follows:

Type. Sandstones and limestones of the south side of the Adirondacks, 

Saratoga county, N. Y., containing the Upper Cambrian fauna.

Correlated. Upper part of Cambrian limestones of Dutchess county, N. Y., 

and an unknown portion of the limestones of the " Marble Belt" of western 

Vermont.

Upper part of shales of Tennessee (Knox), state of Georgia, and Alabama 

(Connasauga), and the lower part of the Knox dolomite.

Upper part of the sandstones of the Upper Mississippi valley (St. Croix).

Upper Cambrian limestones of South Dakota, Wyoming, Montana, and 

Colorado.

Upper calcareous beds of the Cambrian of northern Arizona (Tonto) and 

central Texas (Katemcy).

Upper Cambrian limestones and shales of Nevada (Hamburg), Idaho, and 

Montana (Gallatin).

Black shales of the upper portion of the New Brunswick and Cape Breton 

Island Cambrian sections.

Upper Cambrian shales and sandstones of Conception Bay, Newfoundland 

(Belle Isle).

The name " Saratogian," later changed to " Saratogan," was in 

1912 replaced by St. Croixan, as explained in the quotation under 

St. Croixan epoch, which follows. The rocks in the Saratoga region 

are now considered by Ulrich and Walcott to be younger than the 

typical Upper Cambrian of the British Isles.

ST. .CROIXAN EPOCH (OR SERIES)

(Upper Cambrian) 

C. D. Walcott, 1012 (Smithsonlan Misc. Coll., vol. 57, No. 10, pp. 306-3O7).

ST. CROIXAN OR UPPER CAMBRIAN tt

When I proposed the name " Saratogian " in 1903 ** for the Upper Cambrian 

group of formations, an examination of several lists of geological formation names failed to show that the name Saratoga had been used by Dr. J. C. 

Branner 43 for a Cretaceous chalk marl in Arkansas, in his description of 

" The Cement Materials of Southwest Arkansas." ** A description of the forma-

« Ulrich, Bull. Geol. Soc. America, Vol. 22, No. 3, 1911, pi. 27, pp. 613 and 614.

« Journ. Geol., Chicago, Vol. II, 1903, pp. 318-319.

43 Dr. John M. Clarke recently (May 27, 1912) called attention to this use of the name 

Saratoga by Branner, and wrote that he was then discussing the history of the name in a 

paper in press.

"Trams, American Inst. Mining Engineers, Vol. 27, 1898,, pp. 52-55.
98 GEOLOGIC TIME CLASSIFICATION

tion is given, with sections illustrating its stratigraphic position. In 1902 a 

Mr. J. A. Taff used the term Saratoga formation in the same, sense as Branner 

and gave illustrations of sections and contained fossils.

In view of the prior use of the name Saratoga by Branner and Taff, I doubt 

the advisability of continuing the use of Saratogan as a group name for the 

Upper Cambrian formations. There is also the fact that the two formations 

of Saratoga County, New York, that are used as the basis for the name, are 

not typically of Upper Cambrian age. A present tendency is to include them 

as passage beds between the Cambrian and the superjacent system of strata, 

or as belonging to the higher systems.40 With the evidence now known to me 

from New York and the Appalachian region to' the southwest I am inclined 

tentatively to refer the fauna as found in New York State to the upper limit 

of the Cambrian. The " Saratogan " would thus be correlated with one of 

the upper horizons of the " St. Croix sandstone" nnd included in the Upper 

Cambrian.47

My present view is that the use of the name Saratoga should be restricted 

to the Cretaceous formation, another name adopted for the group of formations 

included in the Upper Cambrian, and another name for the Potsdam-Hoyt 

fauna if that fauna is considered as distinct from the Upper Cambrian fauna.

When looking up a name for the Upper Cambrian formations in 1903, I 

thought of St. Croixan, but as the name St. Croix had become fixed in geological 

literature for the Cambrian sandstone of the Upper Mississippi Valley 48 I did 

not use it. In 191149 Dr. E. O. Ulrich proposed to use the name St. Croixan 

for the sea in which the St. Croix sandstones were deposited, and in his 

table of correlations of formations (pi. 27) and on pc^ge 614 of the same work 

he uses the term as a collective name for the Upper Cambrian formations. If 

we drop the term " St. Croix" as a formation name for the sandstones of 

Wisconsin and Minnesota containing the Upper Cambrian fauna, then the term 

St. Croixan may be used for the assemblage of formations characterized by 

the Upper Cambrian fauna.

The Upper Cambrian or St. Croixan epoch is characterized by 

fossil remains of trilobites belonging to the genera Olenm and 

DiceUocepkalus. The Upper Cambrian rocks of the St. Croix Valley are now divided into several named formations. (See further 

explanations under " Saratogan " epoch, Cambrian period, and the 

proposed new name " Ozarkian system")

ACADIAN EPOCH (OR SERIES)

(Middle Cambrian) 

J. AV. Dawson, 1868 (Am. Assoc. Adv. Sci. Prpc., vol. 16, pp. 117-118).

ON RECENT GEOLOGICAL DISCOVERIES IN THE ACADIAN PROVINCES OF BRITISH AMERICA. 

BY J. W. DAWSON, OF MONTREAL, CANADA

(Abstract)

The object of the paper was to notice some recent discoveries which, though 

of interest, might have escaped the notice of members of the Association.

«s Twenty-second Ann. Rept. U. S. Geol. Survey, 1902, pp. 714-720.

48 See Ulrich, Bull. Geol. Soc. America, Vol. 22, No. 3, 1911,, pi. 27, and p. 612.

47 See Smithsonian Misc. Coll., Vol. 57, No. 9, 1912, pp. 255, 2v>6, for a fuller discussion 

of this question.

48 See N. H. Winchell,, 1873, Ann. Rept Board of Regents, University of Minnesota. 

First Ann. Rept. Geol. and Nat. Hist. Surv. for 1872, pp. 68-80. 

40 Ulrich, Bull. Geol. Soc. America,, Vol. 22, No. 3, 1911, p. 613.
THE PERIOD AND EPOCH TERMS 99

In New Brunswick, th6 older rocks in the vicinity of the city of St. John 

have been reduced to order, and their probable ages ascertained, principally 

through the labors of Mr. Matthew, Mr. Hartt, and Prof. Bailey. The first 

step toward the knowledge of their precise date was the discovery of a rich 

land Flora in some of the upper beds, next below the lower carboniferous rocks 

which overlie them unconformably. These fossil plants I was enabled to recognize as of the Devonian period, and the zealous researches, more especially of 

Mr. Hartt, have brought to light no less than forty to fifty species, or half of 

the whole number known in the Devonian, of Eastern America, as well as six 

species of insects, four of which have been described by Mr. Scudder-.50 These 

insects are the first ever found in rocks older than the carboniferous.

These rocks, consisting chiefly of hard shales and sandstones, having been 

ascertained to be Devonian, there still remained an immense thickness of 

underlying rocks of uncertain age. In the upper member of these rocks the 

same active observers already mentioned have discovered a rich primordial 

fauna, embracing species of Conocephalites, Paradoxides, Microdiscus, and 

Affnostus, as well as an Orthis and a new type of Cystidian. These fossils 

are regarded by Mr. Hartt and Mr. Billings, as of the age of Barrande's 

" Etage C," and as marking a new and older period of the " Silurian Primordial" 

than any other as yet recognized in America, with the exception of the slates 

holding Paradoxides in Massachusetts, and the similar slates of the " Older 

Slate Formation" of Jukes in Newfoundland. Descriptions of these fossils, 

by Mr. Hartt, will be published in the edition of Acadian geology now in press. 

It is proposed to call this series, represented in New Brunswick by the St. 

John slates, the Acadian Series.

Below these primordial beds are highly metamorphosed rocks, at least nine 

thousand feet in thickness, which have not afforded fossils. A portion of these 

beds, consisting principally of conglomerate and trappose beds, is regarded by 

Messrs. Matthew and Bailey as of the age of the Huronian. The remainder, 

containing much gneiss and a bed of crystalline limestone, they regard as 

Laurentian. If this view is correct, and it certainly seems to be probable, 

these rocks, thus rising through the oldest members of the lower Silurian, and 

forming a stepping-stone between the Laurentian of Newfoundland and that 

of New Jersey, show that the foundations of the north-east and south-west line 

of the east side of North America were already laid in the Laurentian period.

C. D. Walcott, 1891 (TJ. S. Geol. Survey Bull. 81, p. 248).

The name Acadian was proposed by Sir J. W. Dawson in 1867 for the series 

of rocks represented in New Brunswick by the St. John slate of Mr. G. F. 

Matthew.81 In 1868 these observations were reprinted with the statement that 

the discovery adds a new formation to the Paleozoic period in America. He 

says:

" This formation has as yet been known as the ' St. John group,' but I think 

this name unsuitable, both on account of the number of places known as St. 

John and on account of the variety of formations occurring near St. John, in 

New Brunswick, and would propose for the group now under consideration, 

characterized by Paradoxides, Conocephalites, etc., and the oldest known member of the Paleozoic of America, the name Acadian group, by which I hope it

60 Canadian Naturalist and Geologist, 1867.

a On recent geological discoveries in the Acadian provinces of British. America. Proc. 

Am. Assoc. Adv. Sci., vol. 16, 1867, pp. 117-119. [Paper read in 1867,. published in 1868.]

1146 25 8
100 GEOLOGIC TIME CLASSIFICATION

will be known to geologists in whatever part of America it may be recognized." 52

In a recent paper on the fauna of the St. John group, Mr. G. F. Matthew 

limits the term Acadian to his Division 1 of the New Brunswick Cambrian 

section. This includes the fauna of the Paradoxides zone.58

The Middle Cambrian or Acadian epoch is characterized by fossil 

remains of trilobites belonging to the genus Paradoxides. (See 

further explanation under Cambrian period.}

" GEORGIAN " EPOCH (OR SERIES) 

(Discarded name for Lower Cambrian) 

C. D. Walcott, 1886 (IT. S. Geol. Survey Bull. 30).

L'See explanation under Cambrian pwiod]

The name " Georgian " was in 1912 replaced by Waucoban, as 

explained in the quotation under Waucoban epoch, which follows.

C. D. Walcott, 1012 ( Smlthsonlan Misc. Coll., vol. 57, No. 10, pp. 3O5-3O6).

With the development of the mapping of the geological formations of the 

United States, it has increasingly become evident that the use of more than one 

term derived from the same geographic name is faulty in principle and confusing in usage. I have long been guilty of doing it in the use of Georgian 

for the Lower Cambrian series of formations. * * *

WAUCOBAN OR LOWER CAMBRIAN

Under the principle stated in the preceding paragraph, the term Georgian 

as used by. me in 1891 M is in bad form and should be replaced by a geographic 

name that has not been used for any geologic formation or group of formations. 

The history and use of the name Georgia is given in Bulletin 81, cited above, 

on pp. 98-113, 249-250, and 360.

Since the publication of Bulletin 81 in 1891, it has been found that the 

greatest development of the Lower Cambrian terrane is in Esmeralda County, 

Nevada, and the adjoining county of Inyo, California.

The Barrel Spring section of Nevada 55 has several thousand feet of Lower 

Cambrian strata, with a fine Lower Cambrian fauna. The Waucoba M section, 

30 miles to the southwest, in California, is also finely exposed, and it has a 

well-marked Lower Cambrian fauna that extends through 4,000 feet of strata.

In view of the fine section east of Waucoba Springs, on the northeastern 

side of Saline Valley, and the great development of Lower Cambrian strata 

to the north and east in Nevada, the term Waucoban is selected to replace Georgian as a group name for the formations included in the Lower Cambrian.

82 Acadian geology. The geological structure, organic remains, and mineral resources of 

Nova Scotia, New Brunswick, and Prince Edward Islands. 2d ed., London, 1868, p. 638.

88 Illustrations of the fauna of the St John G-roup No*. 5. Trans. Roy. Soc. of Canada, 

vol. 8, 1891, p. 129.

" Bull. U. S. Geol. Survey, No. 81, 1891, p. 360.

SB Smithsonian. Misc. Coll., Vol. 53, No. 5, 1908, pp. 188-189. 

pp. 185-188.
THE PEEIOD AND EPOCH TEEMS 101

The Lower Cambrian or Waucoban epoch is characterized by fossil 

remains of trilobites belonging to the genus Olenellus. (See further 

explanation under Cambrian period.)

Schuchert 57 now treats the Waucoban as a provincial rock series, 

and applies the name " Taconian " to the Lower Cambrian epoch 

and " Taconian series" to the Lower Cambrian rocks of eastern 

North America. He says: 57

The Lower Cambrian is restricted in eastern North America to the Appalachic geosyncline and its rocks will be referred to as the Taconian series. 

The strata of the Cordilleric geosyncline in western North America are embraced 

under the term Waucobian series. * * *

It is only in recent years, through the growth of our science from facts garnered in all parts of the world, that a greater unanimity of opinion has come 

about, and some of the Taconian formations have been seen actually to have 

the age relations that Emmons attributed to them. He held that the Taconian 

rocks are older than the Potsda'm sandstone, a formation now referred to the 

uppermost Cambrian, and that they are at the base of the Paleozoic series, conclusions that are true at least in pairt It is on this residuum that the validity 

of the Taconian rests, and it must be recognized as at least a series term in 

good standing.

" TACONIC SYSTEM »

E. Emmons, 1842 (Geology of Xew York, pt. 2, div. 4, Geol. 2<1 dist., pp. 

135-164, 420).

TACONIC SYSTEM

A group or system of rocks which belong evidently to a position between the 

primary of the Atlantic ranges of mountains, and the New-York system. 

[Page 136.]

The Taconic system, a°s its name is intended to indicate, lies along both sides 

of the Taconic range of mountains?, whose direction is nearly north and south, 

or for a great distance parallel with the boundary line between the States of 

New York, Connecticut. Massachusetts and Vermont. The counties through 

which the Taconic rocks pass, are Westchester, Columbia, Rensselaer, and 

Washington; and after passing out of the State, they are found stretching 

through the whole length of Vermont, and into Canada as far north as Quebec. 

It is, however, in Massachusetts, in the county of Berkshire, that we find the 

most satisfactory exhibition of these rocks. They form a belt whose width is 

not far from fifteen miles along the whole western border, and which extends 

clearly to the western base of the Taconic range. The greatest breadth, therefore, as will be seen by an inspection of any map of this section of country, is 

wider upon the eastern than upon the western side of this range. In Vermont they range along the upper members of the Champlain group, and thus 

become connected with the Second district. * * * The slates and masses 

of the Taconic system are not related to, or connected with, those of the Champlain group. By this I mean that they are not the same rocks in another 

condition; or, in other words, that they are not a part of the former group 

in a metamorphic state. * * [Page 138.]

Comparing the several members of the Taconic system with rocks bearing 

the same name in the Primary, very little doubt remains of their total dissimilarity. * * * Considered geologically, they can be regarded in no other

87 Schuchert, Charles, Textbook of geology, 2d ed., vol. 2, p. 187, 1924.
102 GEOLOGIC TIME CLASSIFICATION

light than as inferior to the Potsdam sandstone, or as having been deposited at 

an era earlier than the lowest member of the New-York Transition system. 

We have in no instance, however, been able to trace a connection in these 

masses, and we have never found the Potsdam sandstone resting upon any of 

the members of the Taconic system. * * * The bare fact that the Potsdam 

sandstone rests on gneiss or granite, without the interposition of any other 

rock, we early pointed out. * * * [Page 140.]

The number of rocks which compose the Taconic system is quite limited; 

this is an important feature, which is not to be lost sight of. It does not, however, follow that it is necessarily thin; on the contrary, it is remarkably thick, 

and hence becomes of more importance than appears from a simple statement of 

the number of rocks of which it is composed.

As a whole, we find granular quartz, slate and limestone to form the entire 

system. But it is to be remarked, that it is necessary to take cognizance of 

two kinds of slate and two of limestone; for although there are many points 

of resemblance in each of the two rocks respectively, still their position and 

lithological differences, though small, require their separation. The full enumeration is as follows:

1. A coarse granular limestone of various colors, which I have denominated 

Stockbridye limestone [ranges in age from Trenton to Lower Cambrian 58 ], 

taking its name from a well-known locality, one which has furnished to different parts of the Union a ]arge proportion of the white and clouded marbles 

which have been so extensively employed for building and ether purposes in 

construction.

2. Granular quartz rock [Cheshire quartzite, of Lower Cambrian age 68 ], 

generally fine-grained, in firm tough crystalline masses of a brown color, but 

sometimes white, granular and friable.

3. Slate, which for distinction I have denominated Magnesian slate [Berkshire schist, of Trenton and Upper Ordovician age 08 ] from its containing magnesia, a fact which is distinctly indicated by the soft feel peculiar to rocks 

when this earth forms a constituent part.

4. Kparry limestone [Ordovician and same as top of Stockbridge limestone 28 ], 

generally known as the sparry limerock.

5. A slate, which I have named Taconic slate [Ordoviciab M ], and which is 

found at the western base of the Taconic range. It lies adjacent to the Lorrain or Hudson river shales, some varieties of which it resembles. In composition, it contains more alumine and less magnesia than the magnesian slates.

In addition to the above rocks, there is sometimes a slate of a dark color, 

and quite siliceous, in the granular quartz. This appears less constant, and 

may be considered as a slaty quartz, or variety of this rock. There are several 

deposits, important in themselves, which strictly belong to this system: the 

hernatitic iron ores, associated sometimes with carbonate of iron, and the 

black oxide of manganese. Subordinate to the rocks, we find milky quartz and 

chlorite, with carbonate and oxide of iron in the magnesian slate.

The following section [text figure], extending from Petersburg!!, Eensselaer 

county, to Adams in Massachusetts, embraces all the rocks in this system. Its 

direction is nearly east and west, or perpendicular to the strike of the system 

over which it passes: [Pages 144 to 145.]

The Taconic rocks appear to be equivalent to the Lower Cambrian of Prof. 

Sedgwick, and are alone entitled to the consideration of belonging to this 

system, the upper portion being the lower part of the Silurian system. [Page 

163.]

[ M According to the studies of Arthur Keith.]
THE PERIOD AND EPOCH TERMS 103

Schuchert, in the second (1924) edition of his textbook of geology, 

applies the name " Taconian series " to the Lower Cambrian rocks of 

eastern North America. (See p. 101, under Waucolmn epoch.}

ALGONKIAN PERIOD (OB SYSTEM)

The name Algonkian was adopted at a meeting of geologists of the 

United States Geological Survey held in Washington on January 28 

to 31, 1889, as explained on pages 62 to 63 of Part I of the Tenth 

Annual Report of the Director. The name first appeared in print? 

but without definition, in 1889, having been used by Walcott in tables 

in a paper read by him before the Philosophical Society of Washington on March 16. 1889, and published in the American Journal of 

Science for May, 1889. The Tenth Annual Report of the Director 

was published in 1890. (See citations below.)

C. D. Wffilcott, 1889 (Am. Jotir. Sci., 3d ser., vol. 37, pp. 383, 384, May, 18S9; 

name used but not defined).

J. W. Powell, 1890 (.17. S. Geol. Survey Tenth Ann. Kept., pt. 1, pp. 19-2O, 

59-61, 6O; letter of transraittal dated July 25, 1889).

The tenth period shall be the time of deposition of clastic rocks older than 

the Cambrian. Its lower delimitation can not be definitely fixed, but its upper 

is definitely determinate as just below the beginning of the Cambrian. The 

period is represented by some rocks which have been referred to the Cambrian, 

many which have been referred to the Hnronian, and some formations which 

have not hitherto been classified. Exception being taken to the term Eparchean, and also to the term Huronian (proposed on the ground that it had been 

previously applied to a part of the rocks, but opposed on the ground that the 

definitions of this period are entirely unlike those accepted for the Huronian), 

the term Algonkian was offered and agreed to as the designation of the period.

The oldest time division shall cover the time of formation of the ancient 

crystalline rocks, and its designation shall be Archean. [Page 66.]

As thus originally defined the Algonkian included all pre-Cambrian clastic rocks. Later work, however, revealed the presence of 

metamorphosed sedimentary rocks in the basement complex to which 

the name Archean had been restricted. The definition of Algonkian 

now recognized by the United States Geological Survey is as follows:

In various parts of the world, below the Cambrian, and usually separated 

from that system by an unconformity, is a great system of rocks to which can 

be applied the ordinary methods of stratigraphy. This system consists dominantly of rocks deposited under substantially the same physical conditions as 

those which obtained during the Cambrian and later periods. That is, these 

rocks are chiefly shales, sandstones, and limestones, and their metamorphosed 

equivalents. Associated with this system of rocks, both as intrusives and extrusives, are igneous rocks, precisely as is the case with the later systems. In 

some regions this older system is represented by two or more series, separated 

by unconformities. While scanty fossils have been found in a few areas, as yet 

they have not been discovered so distributed and in such abundance as to serve 

the purposes of correlation of the series from province to province.
104 GEOLOGIC TIME CLASSIFICATI01SThe characters by which the Algoukian and Archean are discriminated are 

lithologic and structural.18

Within the Algonkian system a number of provincial series are 

discriminated. In the Algonkian of the Great Lakes region two 

great unconformable series are recognized, the Keweenawan series 

above and the Huronian series below, and unconformities of greater 

or less magnitude are recognized within the Huronian series. The 

Algonkian rocks exposed in Montana and northern Idaho have been 

given the provincial series name Belt series, from the Big Belt and 

Little Belt Mountains of central Montana, where they are well exposed. The Algonkian rocks of northern Arizona have been named 

the Grand Canyon series, from their admirable exposures in the 

Grand Canyon of the Colorado. The pre-Cambrian rocks of central 

Texas, which are at least chiefly of Algonkian age, but which may 

include some Archean rocks, are known as the Llano series, from 

Llano County, Tex. The pre-Cambrian rocks of the Adirondack 

Mountains of New York and neighboring parts of Canada have long 

been known as the Grenville series, from their exposures at Grenville, Canada. The series of metamorphosed pre-Cambrian sediments in southeastern Pennsylvania, Maryland, and northern Virginia have recently been named Glenann series, as described on 

page 112.

The name Algonkian is derived from the Algonkian Indians, who 

once inhabited and still occupy in part the Lake Superior-OntarioHudson Bay country, where rocks of this age probably have their 

greatest development. The rich iron and copper deposits that have 

made the Great Lakes region famous in the commercial world are 

contained in these rocks, the iron ores occurring in the Huronian 

series and the copper ores in the Keweenawan series.

KEWEENAWAN EPOCH (OR SERIES) 

T. B. Brooks, 187O (Am. Jour. Sci., 3d ser., vol. 11, pp. 2OG-S11).

We are therefore justified, I think, in regarding the Copper-bearing rocks 

of Lake Superior as a distinct and independent series, marking a definite 

geological period which separates the Silurian from the Huronian ages. 

Should future observations confirm this view, it would be advisable to have 

some more convenient and geologically acceptable name for the series than 

that now in use. Since Keweenaw Peninsula forms one of the most striking 

geographical features in Lake Superior and is the locality where the Copper 

series are best exposed and were first studied, I suggest the name Keweenawian 

for this period.

The foregoing is regarded as the original definition of the 

Keweenawan series, although in 1873 T. Sterry Hunt,60 in a paper

ro U. S. Geol. Survey Twenty-fourth Ann. Kept, p. 26, 1903. 

«°Am. Inst. Min. Eng. Trans., vol. 1, pp. 331-346, 1873.
THE PERIOD AND EPOCH TERMS 105

entitled " The geognostical history of the metals," referred to the 

copper-bearing rocks in the following way:

We may here remark that the late researches of Messrs. Brooks and 

Pumpelly seem to establish that the great copper-bearing series of Keweenaw 

occupies a place between the Huronian schists and the nearly horizontal red 

and white sandstone of the region, which is itself below the Trenton limestone. In all this they have confirmed the previous conclusions of Houghton, 

Whitney, Hall, and Logan. The silver deposits of Thunder Bay and its 

vicinity, including Silver Islet, are in veins traversing a series of dark-colored 

argillites and sandstones, which are as yet known only in this region, and 

are overlaid in slight discordance by red and white sandstone, apparently the 

same with those of the Keweenaw district and the St. Marys River. This 

older series of Thunder Bay and its vicinity, which may be named the Animikie 

group, from the Indian name of the bay, is the lower division of the upper 

copper-bearing series of Logan.

The great Keweenaw group, with its cupriferous amygdaloids, is here absent, 

though met with a few miles to the eastward, and the almost horizontal darkcolored sediments of the Animikie group rest directly upon the edges of the 

crystalline Huronian schists, and are cut by great dykes of diorite. * * * 

[Page 339.]

To a like process we may perhaps ascribe the rich deposits of native copper 

in the Keweenaw amygdaloids and conglomerates which rest upon the ancient 

Huronian schists. * * * [Page 341.]

I may here suggest in a few words as a probable solution, that the horizontal sandstones of Thunder Bay, whether identical with those of the south 

shore or not, and whether paleozoic or mesozoic, are really newer than the 

adjacent cupriferous amygdaloids, and are not 'to be confounded with the 

sandstone strata which, on both sides of the lake, are found interstratified with 

these as integral parts of the more ancient Keweenaw or copper-bearing series. 

[Page 342.]

F. D. Adams, Robert Bell, A. C. Lane, C. K. Lelth, W. G. Miller, and C. R. 

Van Hise, 1OO5 (Report of the special committee for the Lake Superior 

region: Jour. Geology, vol. 18, p. 102).

There is an important structural break at the base of the Keweenawan. 

The term " Keweenawan " should include substantially all of the areas which 

have been thus mapped, or mapped as Nipigon, by the Canadian and United 

States Surveys, and the State Surveys of Michigan, Minnesota, and Wisconsin.

The Keweenawan series, or copper-bearing rocks of the Great 

Lakes region, consists of interbedded eruptive rocks and sediments, 

with basic intrusive rocks, and it unconformably overlies the Animikie group and uncomformably underlies the Cambrian sandstone 

of that area. The rocks were originally believed to be of Cambrian 

age.

HURONIAN EPOCH (OR SERIES)

W. E. Logan and T. S. Hunt, 1855 (Esauisse geologique dn Canada, pp. 

29-31).

CAMBRIAN OB HURONIAN SYSTEM

The shores of Lakes Huron and Superior offer us a series of schists, sandstones, limestones and conglomerates, intercalated with great thicknesses 

of diorite and resting unconformably upon the Laurentian system. As these
106 GEOLOGIC TIME CLASSIFICATION

rocks are beneath the Silurian terrane, and as, moreover, they have not up 

to the present yielded any fossils, they may well be referred to the Cambrian 

system (the Lower Cambrian of M. Sedgwick). The schists of this system on 

Lake Superior are of a bluish color, and contain beds of horny flint with 

limestone bands, the fractures of which are often filled with anthracite 

[graphite?].

These rocks are covered by a considerable thickness of trap, on which are 

superimposed thick strata of white and red sandstone, which sometimes pass 

into conglomerate containing pebbles of quartz an(j jasper. Beds of reddish 

argillaceous limestone are found interposed in these sandstones, which are 

intruded and overlain by a second formation of diorite of great thickness and 

having a columnar structure. This formation, which according to the observations of M. Logan, has a total thickness of nearly 4,000 meters, is cut by 

a large number of trap dikes.

In the corresponding formation on the northern shore of Lake Huron there 

are sandstones having a more vitreous aspect and more abundant conglomerates 

than on Lake Superior, associated, however, with some schists and schistose 

conglomerates like those just described, the whole forming a great mass intercalated with diorite. A bed of limestone having a thickness of 16 meters 

forms a part of this series, to which M. Logan ascribed a thickness of more 

than 3,000 meters. M. Logan has shown that the intrusion of these interstratified diorites was followed by that of two systems of diorite dikes and a 

third of granite of an epoch intermediate between the last two. The metalliferous veins belong to a still more recent epoch. The principal kinds of 

veins are native copper, quartz, calcspar, dolomite, fluorite and barite, with 

several zeolites, of which the most abundant is laumontite. One also encounters heulandite, stilbite, thomsonite, apophyllite, and analcite, as well 

as prehnite and datolite. Th'ese veins are not metalliferous except where they 

penetrate the trap.

F. D. Adams, Robert Bell, A. C. Lane, C. K. Leith, W. G. Miller, and C. R. 

Van Hise, 1905 (Report of the special committee for the Lake Superior 

region: Jour. Geology, vol. 13, pp. 103-1O4).

Below the Keweenawan is the Huronian system, which in our opinion 

should include the following series: In the Marquette district, the Huronian 

should include the Upper and Lower Marquette series, as defined in the monographs of the United States Geological Survey, or the Upper, Middle, and 

Lower Marquette series, as given in the previous paragraphs. In the PenokeeGogebic district, the Huronian should include the series which have been 

called the Penokee-Gogebic series proper, and the limestone and quartzite 

which have local development, and which we visited east of the Presque Isle 

River. In the Mesabi district, the Huronian should include the Mesabi series 

proper, and the slate-graywacke-conglomerate series, unconformably below 

the Mesabi series. In the Vermilion district, the Huronian should include the 

Knife slates and the Ogishke conglomerates. In the Rainy Lake district, the 

Huronian should include that part of the Couchiching of the south part of 

Rainy Lake which is limited below by basal conglomerate as shown at Shoal 

Lake. In the Thunder Bay district, the Huronian should include the Animikie and the graywacke series in the Loon Lake area. In the original 

Huronian area, the Huronian should include the area mapped by Logan and 

Murray as Huronian, except that the Thessalon greenstones should probably 

be excluded. * * *
THE PERIOD AND EPOCH TEEMS 107

The following succession and nomenclature are recognized and adopted: 

Cambrian Upper sandstones, etc., of Lake Superior. 

Unconformity. 

Pre-Cambrian:

Keweenawan (Nipigon)."1 

Unconformity. 

Huronian:

Upper (Animikie). 

Unconformity. 

Middle. 

Unconformity. 

Lower.

Unconformity. 

Keewatin. 

Eruptive contact. 

Laurentian.

As originally defined the Huronian included at the top the 

great series of copper-bearing rocks that were later named Keweenawan, as well as the underlying slate, iron-bearing rocks, and quartzite later called upper Huronian and named Animikie group. In 

1876 the copper-bearing rocks were separated from the Huronian 

as a distinct series and named Keweenawan by T. B. Brooks. The 

pre-Cambrian rocks, in which, owing to their highly metamorphosed 

condition, few fossils occur, are characterized by very complex structure. Thus,' in attempting to unravel their history, complications 

were found and disagreements arose among the geologists working 

in different parts of the Great Lakes region, where the pre-Cambrian 

rocks of America have their greatest development. In order to harmonize these differences of opinion and determine the classification 

that would best apply to these rocks, a joint field and office conference of American and Canadian geologists was held in 1904 and 

1905. The definition of the Huronian series adopted by that committee (consisting of F. D. Adams, Robert Bell, W. G. Miller, A. C. 

Lane, C. K. Leith, and C. R. Van Hise) applied the name to the 

rocks unconformably beneath the Keweenawan series and unconformably above the Keewatin series. As thus defined the Animikie 

group is included in the Huronian. Several unconformities were 

recognized within the Huronian series. The one at the base of the 

Animikie group is now regarded by some workers as of greater 

magnitude than the others, and they would exclude the Animikie 

rocks from the Huronian series and make a separate series of them. 

This is still a debated question. (Note the diverse classifications

a Dr. Lane dissents as to the position of the Keweenawan as follows:

" The use of pre-Cambrian above does not imply unanimity in the committee with regard

to the pre-Cambrian correlation of the Keweenawan a topic the committee as such, did

not investigate."
108 GEOLOGIC TIME CLASSIFICATION"

given in the chart and on pages 15-43 under the heading Pre-Cambrian era terms^) In more recent reports some authors have dropped 

the name Huronian altogether and have elevated the middle and 

lower Huronian to series rank, under the names " Timiskamian," 

" Bruce," " Seine," etc., the definitions of which will appear in the 

stratigraphic lexicon now in preparation.

The Huronian series consists of metamorphosed and unmetamorphosed rocks, and includes slates, quartzites, graywackes, finegrained green schists, mica schists, hornblende schists, fine-grained 

gneisses, iron-bearing schists, and interbedded basic and acidic eruptive rocks of various kinds.

As the term Cambrian was generally understood at the time the 

name Huronian was introduced it included some rocks that are now 

classified as pre-Cambrian. This explains the original reference of 

the Huronian rocks to the Cambrian system of Sedgwick, a reference that was corrected many years ago.

The United States Geological Survey recognizes within the Huronian series many local subdivisions (the definitions of which are 

given in the stratigraphic lexicon now in preparation) and the fact 

that it is penetrated by granitic intrusions of different ages.

OTHER PROVINCIAL SERIES TERMS

BELT SERIES 

A. C. Peale, 1893 (U. S. Geol. Survey Bull. 11O, pp. 15-2O).

Cambrian:

Gallatin formation.

Flathead formation [including Flathead quartzite at base]. 

Algonkian ?:

Belt formation.

The Paleozoic section of the Three Forks region, including the beds provisionally assigned to the Algonkian, consists of a series of sedimentary deposits 

of nearly 10,000 feet thickness, resting upon Archean gneiss. Over 8,000 feet 

are shown in the Gallatin section, which does not, however, reach down to the 

Archean. A few miles south of the region shown on the map this thickness 

is reduced to a little over 3,600 feet by the absence of the Belt formation, as 

the Flathead formation [Cambrian] whenever seen there rests unconformably 

upon the Archean gneisses without the interposition of the Belt formation. 

The section of the region to the north, as given by Mr. W. M. Davis, is from 

15,000 to 20,000 feet, the increased thickness being due mainly to the greater 

development of the Belt formation (called by him Lower Cambrian barren 

slates).

The gneisses of our region can not at present be correlated, even provisionally, with the Archean rocks of the east. They are certainly pre-Cambrian, 

if the Flathead formation is of Lower Cambrian age, for included in the lower 

strata of the latter at several localities are fragments of gray and red gneiss 

evidently derived from the underlying Archean, and that they are preAlgonkian is proved by similar occurrences in the Belt formation in the northern portion of our sheet.
THE PERIOD AND EPOCH TERMS 109

The evidence for the reference of the Belt formation to the Algonkian is of 

a somewhat negative character, and will be noted more particularly when the 

included beds are described on a subsequent page. The entire section so far 

as observed is conformable from the base to the top. There is difficulty in 

attempting to define exactly the lines between the formations, even so far as 

the greater divisions are concerned, and the correlation necessarily has not 

been carried any farther, local names being applied to the minor divisions. It 

is a question whether the divisions of the geological scale as made in the eastern United States can ever be recognized in the strata of the Rocky mountain 

region.

ALGONKIAN

Belt formation

The section in the vicinity of the Three Forks begins with a series of beds 

<of littoral formation which was in 1884 provisionally called the East Gallatin

group, so named from the well exposed outcrops occurring along the north 

side of the East Gallatin river near its junction with the West Gallatin, where 

a detailed section of 2,300 feet has been carefully measured. It consists of 

en alternation of coarse micaceous sandstones and conglomerates, with beds 

of hard argillaceous slates, and bands of thin bedded dark-blue siliceous limestones. The latter are very hard and some are slightly magnesian. * * * 

[Analyses.] 

The limestones are developed mainly toward the base of the measured section and occur in bands from 5 to 20 feet in thickness but sometimes reaching 

nearly 50 feet. Many of the beds are very finely laminated, of a dark blue 

almost black color in fresh fractures, and showing light yellowish brown on 

weathered surfaces. About half way up in the section the limestones change 

in their appearance. They are more compact, not so dark in color, but are 

still highly siliceous and layers with peculiar flat round concretions are seen. 

These concretions have been mistaken for fossil turtles by the people living 

in this part of the Gallatin valley. Some of the concretions are very large, 

often measuring several feet in diameter and from 6 to 12 inches in thickness, 

but they average about 6 inches to a foot in diameter with a thickness of only 

3 to 4 inches. Sections of them show no peculiarities.

The indurated clay slates are also most abundant towards the middle and 

base of the measured section, and present a variety of colors yellowish brown, 

olive-green, and bluish black predominating. The beds are very fissile, frequently breaking down into fine splintery debris, generally of a light color, 

and with frequent local bands of a bright red tint, as though the beds had 

been subjected to heat. These appear to be scattered over the country irregularly, and their weathering gives a very bright reel debris. The slates are 

particularly well exposed in the bluffs along the west side of Dry Creek below 

its first canyon.

The sandstones are prominent in the upper and lower parts of the section, 

and occur in heavy beds of 5 to 10 and sometimes 20 or 30 feet in thickness. 

They frequently break into cubical blocks with sharp edges, which increases 

their resemblance to eruptive rocks, for which they have sometimes been mistaken. As seen in hand specimens, their arkose character is evident, and often 

water-rolled pebbles of considerable size are seen, especially in the coarser beds 

near the base of the section.

The name " bastard granite " has locally been applied to them. Some of the 

layers are slightly calcareous, especially near the base, where they are intercalated with numerous thin bands of limestone, and some of the lowest sand-
110 GEOLOGIC TIME CLASSIFICATION

stones are cut by seams of pure dolomite. The beds are generally very coarse 

and in places strongly conglomeratic. That Archean land masses, when they 

were deposited, existed not far to the south is very evident from the general 

character of the beds, and is also proved conclusively when they are compared 

microscopically with the Archean rocks of the adjacent region.

In the Bridger range, where the section is carried lower thati on the East 

Gallatin, they contain many pebbles of Archean rocks, and in the lowest outcrops there are included angular masses of gneiss, showing the immediate 

proximity of the ancient shore line. There is considerable difference between 

the various beds so far as structure is concerned, but all are more or less 

mkuceous and occur in massive layers. They are very similar in color, dark 

greenish gray, steel-gray, and rusty brown tints prevailing. Seen from a 

distance, these sandstones resemble outcrops of eruptive rocks, owing partly 

to their somber appearance and partly to their mode of weathering; in fact,, 

when first seen in 1860, they were so mistaken. * * *

In the Big Belt range, north of the limits of the Three Forks sheet, Mr. W. M. 

Davis. in two sections, found a series of from 10,000 to 12,000 feet of beds, 

which from his description undoubtedly belong to this group. He refers tothem as " a vast series of Lower Cambrian barren slates." * * *

Nowhere in the Gallatin valley have we as yet seen this group in .immediate 

superposition upon the Archean, although we have reason to think that the 

line of junction is nearly reached at the base of the section, as seen in the 

Bridger range. * * *

As to the age of this formation we have no paleontological evidence to 

offer, as careful search in the beds for fossils during several seasons has been 

unsuccessful. liayden, in 1860, in 1871, and 1872, was inclined to regard them 

as representing a portion of the Potsdam sandstone.

In 1S85 they were doubtfully referred to the Middle Cambrian; in 1872 the 

writer suggested the possibility of their Huronian age, and as already noted, 

Davis and Newberry both refer to them as Lower Cambrian.

All that can be said with certainty is that they are post-Archean and probably pre-Cambrian, as they are made up largely of Archean debris and lie 

below beds containing Cambrian fossils. So far as observed, no well-defined

unconformity between them and the overlying Flathead quartzite has been seen ; 

but there is certainly an unconformity by subsidence, which is not always well 

shown and might easily be overlooked. There is no doubt that after the 

Belt formation was deposited there was an orographic movement by which the 

Archean area of nearly the entire region represented on our map south of the 

Gallatin and Three Forks was submerged just prior to the beginning of the 

Cambrian before the Flathead quartzite was deposited. Whether this movement 

occurred immediately after the laying down of the Belt beds or after an 

interval is of course the question to be decided, and the decision can not be 

positively reached with the meager data now at hand. I am inclined to think 

that the subsidence of the Archean continent (or possibly islands) began with 

the first accumulation of the sediments that formed the lower portion of" 

these beds and was coincident with their deposition throughout the entire 

period. It may have been succeeded by an emergence of the land area for a 

brief period, but the probability is that the interruption to the downward' 

movement, if it occurred, was slight. Next the widespread pre-Cambrian 

subsidence preceding the formation of the Flathead quartzite took place, and 

the Cambrian sea covered large areas that had thitherto been above the sea 

level. There is a marked difference in the character of the beds of the two 

groups. Little, if any, induration is seen in the Flathead formation, while the 

licit beds are so altered in most cases as to resemble closely the metamorphkr
THE PERIOD AND EPOCH TERMS 111

 crystalline rocks which underlie them, and from the breaking down of which 

they were derived. Notwithstanding the metamorphism there is no mistaking 

their sedimentary character.

We have, therefore, a nonfossiliferous group of clastic beds, sometimes slightly 

metamorphosed, which lie between the Archean gneisses and a belt of quartzite, above which are beds with Middle Cambrian fossils. From its stratigraphical position this group could be only of Lower Cambrian or of Algonkian 

age.

The possibility that Lower Cambrian fossils may yet be found in the quartzite at the base of the Flatheacl formation; the absence of organic remains in 

the Belt formation; the metamorphosed condition of the latter, and the 

existence of the unconformity between the quartzite and the beds below lead 

us to refer the latter, for the present at least, to the Algonkian.

C. B. Walcott, 1899 (Geol. Soc. America Brail., vol. 10, pp. 199-215, 235).

The results of my investigations were the discovery of a great stratigraphic

unconformity between the Cambrian and the Belt formations; that the Belt 

terrane was divisible into several formations, and that the fossils occurred In 

the Greyson shales nearly 7,000 feet beneath the highest beds of the Belt 

terrane.

The rocks of the Belt terrane are widely distributed in central Montana, the 

best sections being exposed in the Big Belt and Little Belt mountains, in 

Meagher and Broadwater counties. They extend to the north in Cascade, to 

the west in Lewis and Clarke and Jefferson counties, and to the south in Gallatin, Park, and Sweetwater counties, in all covering a known area of more 

than 6,000 square miles. Throughout this area the Cambrian rocks rest unconformably on different members composing the Belt terrane. * * *

I think that an unconformity to the extent indicated is sufficient to explain 

the absence of lower Cambrian rocks and fossils and to warrant our placing 

the Belt terrane in the pre-Cambrian Algonkian system of formations.

C. R. Van Hise, 19O9 <TJ. S. Geol. Survey Bull. 360, pp. 32-83, 39, 41, 46, 350).

The largest area of Algonkian known is that of the Belt series of northern 

Montana, Idaho, and southern British Columbia. The Belt series is subdivided 

lithologically into a number of formations, but represents practically continuous 

deposition. To the south in Montana the Cherry Creek sedimentary rocks are 

assigned to the Algonkian. While their relations to the Belt series are not 

shown by direct contact, the relatively greater metamorphism and deformation 

of the Cherry Creek group indicate its earlier age and probable separation by 

unconformity. The quartzites #>f the Uinta and Wasatch mountains, correlated 

with the Belt series, are essentially structural units. The same Is true of the 

quartzites and slates of Needle Mountains, Colorado. In the Grand Canyon 

of the Colorado there are two groups classed in the Algonkian, separated from 

each other by a minor unconformity. [Pages 32-33.]

The Belt series of Montana also is unconformable upon the Archean with 

marked discordance. [Page 39.]

The Belt series in its now known extent constitutes the greatest area of 

Algonkian on the continent, and it may be that this area should be extended to 

Include Utah, Colorado, and Arizona quartzites. [Page 41.]

If the Animikie group is ever found to be the equivalent of the Belt series 

of British Columbia, as is thought possible, this would make more probable 

the Cambrian age of the Keweenawan lying above the Animikie, in view of 

the fact that in British Columbia the Belt series apparently grades up into the 

Cambrian.
112 GEOLOGIC TIME CLASSIFICATION

Against this evidence of possible conformity and favoring the view here 

held that the Cambrian lies unconformably above the upper Keweenawan are

the following facts: * * * [Page 350.]

«

The United States Geological Survey classifies the Belt as a provincial series belonging to the Algonkian system. The name is 

derived from the extensive development of the rocks in the Big Belt 

and Little Belt mountains of central Montana.

GLENARM SERIES 

E. B. Knopf and A. I. Jonas, 1922 (Geol. Soc. America Bull., vol. 33, p. 110 ji.

The crystalline schists of Baltimore County, Maryland, are Precambrian. 

The base of the section is the Baltimore gneiss, a highly crystallo-blastic 

.paragneiss injected in some places by granitic magma. Overlying the Baltimore gneiss is the Glenarm series of recrystallized sediments, whose thickness 

is provisionally estimated at 8,000 to 10,000 feet. These rocks show a metamorphism whose intensity decreases progressively from highly crystalline 

schists at the base to mildly anomorphosed sediments at the top. The lower 

formations of the Glenarm series are cut by plutonic intrusions, and the upper 

formations contain amphibolite schists that are probably metamorphosed 

volcanics a.nd may be the equivalent of the Precambrian Catoctin lavas.

E. B. Knopf and A. I. Jonas, 1023 (Am. Jour. Sci., 5th ser., vol. 5, pp. 45-40, 

61-62).

Overlying the Baltimore gneiss [of early pre-Cambrian age, according to 

page 61] is a series of pre-Cambrian sediments here named the Glenarm series, 

from its typical development near Glenarm, 13 miles northeast of Baltimore. 

The Glenarm series comprises [ascending order] the Setters formation, the 

Cockeysville marble, the Wissahickon formation, the Peters Creek schist, 

the Cardiff conglomerate, and the Peach Bottom slate. The total thickness 

of the series probably amounts to between 8,000 and 10,000 feet, although 

no accurate estimates can be made, for the middle formations have been repeated by close folding. So far as uow known, deposition of this series was

not interrupted by erosion or by orogenic deformation, although the earlier 

formations are overlapping shore deposits.

The basal formation is the Setters, which overlies the Baltimore gneiss 

unconformably but with no basal conglomerate. * * * In the absence of 

positive evidence of erosion, it seems likely that the irregular thickness of 

the Setters formation and of the Cockeysville marble is due to transgression 

rather than to erosion. * * *

Therefore the presence of Catoctin greenstones in this facies [of the Wissahickon formation] would establish the pre-Cambrian age of the Glenarm 

series. Corroborative evidence is the presence within the lower part of the 

Glenarm series of strongly deformed plutonic intrusions. The known Paleozoic 

rocks of Pennsylvania and Maryland are conspicuously free from all igneous 

material except pegmatites, and these are doubtless genetically associated 

with the Woodstock granite, which is considered on account of its undeformed condition to be younger than the pre-Cambrian intrusives. * * *

The Glenarm series underlies a succession of lower Paleozoic rocks who.se 

outcrop is confined to the northern part of the region.

The United States Geological Survey has adopted the name Glenarm series as a provincial series term for the rocks of later pre-
THE PERIOD AND EPOCH TERMS 113

Cambrian age in southeastern Pennsylvania, Maryland, and northern Virginia.

GRAND CANYON SERIES

o 

J. W. Powell, 1876 (Geology of the eastern portion of the Uinta Mountains,

pp. 43, G1-C2, 70, U. S. Geol. and Ceog. Survey Terr., 2d div.).

Grand Canon grottp. Sandstones, shales and a few limestones. Thickness 

10,000 feet. On -further study this group will probably be subdivided. [Page 

43.]

This group is exposed in the great southern bends of the Grand Cafion, 

where the Colorado River passes the end of the Kaibab Plateau. The best exposure can be seen about ten miles below the mouth of the Little Colorado. 

Many of the lateral streams coming in from the west and north cut through 

this group and afford fine exposures. The best one probably is in Kw&-gunt 

Valley. Some of the members are again exposed at the bottom of the Grand 

Cafion, where it passes the Shi-wits Plateau. [Pages 61-62.]

The Grand CaSon Group rests unconformably upon the crystalline schists. 

The evidence of this is complete, for the lower sandstones and conglomerates 

first filled the valleys and then buried the hills of schistic rocks, and these 

conglomerates at the base of the group are composed of materials derived from 

the raetamorphic hills about; and hence metamorphism was antecedent to the 

deposition of the conglomerates.

The plane of demarkation separating this group from the [overlying] Tonto 

Group is very great. At least 10,000 feet of beds were flexed and eroded in 

such a manner as to leave but fragments in the synclinals. Then followed a 

period of erosion during which beds of extravasated material were poured over 

the fragments, and these igneous beds also were eroded into valleys prior to the 

deposition of the Tonto Group. [Page 70.]

C. D. Walcott, 1894 (U. S. Geol. Survey Fourteenth Ann. Kept., pt. 2, pp. 

518-519).

The period of erosion, represented by the unconformity between the Tonto 

sandstone and the Grand Canyon series, is considered to more than equal 

lower Cambrian time, and to constitute a well-defined boundary between the 

Paleozoic and pre-Paleozoic formations. In my earlier work, in 1883, I referred 

the Grand Canyon and Chuar strata to the Cambrian, but upon further study 

of the Cambrian rocks and their contained faunas, and in view of the extent of 

the time break indicated by the nonconformity by erosion, this was changed in 

1886, and all pre-Tonto strata were referred to a pre-Cambrian series.

In the scheme of nomenclature adopted by the Geological Survey in 1888 the 

clastic rocks beneath the Cambrian and superjacent to the Archean were 

grouped under the term Algonkian of equivalent rank to Cambrian, Silurian, 

etc. In this classification the system name equivalent to Paleozoic, etc. 

was not decided upon; but I am strongly in favor of adopting the name 

" Proterozoic," proposed by Dr. Irving and accepted by Prof. C. R. Van Hise. 

Under this nomenclature the Grand Canyon series will be referred to the 

Algonkian system of the Proterozoic group. * * *

The Grand Canyon series, the Llano series of Texas, and the Algonkian 

series of the Lake Superior region afford an opportunity of comparing the 

stratigraphic succession of somewhat similar lithologic series of strata, but a 

definite correlation can not be made until a more reliable factor is obtained 

than lithologic resemblance of the various formations. It is quite probable 

that the Grand Canyon series and the Keweenawan series of Lake Superior 

represent. the same time interval; also that the strata beneath Packsaddle 

Mountata in central Texas are the equivalent of the Chuar terrane of the Grand
114 GEOLOGIC TIME CLASSIFICATION

Canyon; but until paleontologic evidence is secured it may be said that these 

correlations are little more than possibilities. The Grand Canyon, Llano, and 

Keweenawan series may be referred to the Algonkian, as that system of rocks 

includes the strata of sedimentary origin between^the Archean complex and the 

base of the Cambrian; beyond that any correlation on trustworthy data is 

impossible.

The United States Geological Survey classifies the Grand Canyon 

as a provincial series of late Algonkian age.

GKENVILLE SERIES 

IV. E. Logran, 1863 (Canada Geol. Survey Fifteenth Rept. Prog., pp. 43-45).

In this investigation a single band of limestone, which has been termed the 

Grenville band, varying apparently in thickness from 60 to 1000 feet, and 

averaging perhaps 750 feet, emerging from beneath the Silurian rocks, has 

been traced from Grenville to the Iroquois Chute, fifty miles up the valley of 

the Rouge. It presents the general form of a trough, but its distribution is 

so complicated by subordinate undulations that in a triangular area, of which 

the base extends about twenty-five miles between the Petite Nation seigniory 

and Lachute, and of which the apex is at the Iroquois Chute, the line of calcareous outcrop measures upwards of 200 miles. * * *

From what has been said, it will be observed, that in the present state of the 

investigation, without counting the Proctor's Lake bed, which is too small for 

separate consideration, there appear to be four important bands of crystalline 

limestone in the Laurentian area of which the structure has been partially examined. The wrinkled condition of the strata is such that there are in some 

parts four and five anticlinals in the breadth of a mile, the effect of each of 

which is perceptible in the geographical distribution of the strata, and this 

renders it very difficult to determine with precision the volume of rock in which 

the four calcareous bands are inclosed; but according to the best estimate arrived at, it appears probable that the following would be an approximation to 

the thickness of the various constituent parts of the mass arranged in ascending order:

Feet

1. Orthoclase gneiss composing Trembling Mountain; though

the mass has not been especially examined nor any 

geographical position shewing its inferior limit ascertained, yet the general aspect of the mountain induces 

the supposition that it must be of great thickness, and 

it is presumed that it will exceed the volume here 

given______________________________ 5, 000

2. Crystalline limestone of Trembling Lake__________ 1,500

3. Orthoclase gneiss between the limestone of Trembling

Mountain and that of Great Beaver Lake________ 4, 000

4. Crystalline limestone of Great Beaver Lake and Green 

Lake, including two bands of interstratified garnetiferous rock and hornblendic orthoclase gneiss, which may 

equal half the amount__________i_-__________ 2, 500

5. Orthoclase gneiss intermediate between the limestone of 

Great Beaver Lake and Long Lake, and the Grenville 

limestone on the Rouge at the Iroquois Chute, the 

lower part having several bands of garnetiferous gneiss 

and quartzite, and the upper part much coarse grained 

porphyroid orthoclase gneiss 3,500
THE PERIOD AND EPOCH TERMS 115

Feet

6. Crystalline limestone of Grenville, in some parts interstratified with a band of gneiss. The thickness appears 

to vary from about 1500 feet to 60 feet, and may be 

estimated at about __________ __ _ 750

7. Orthoclase gneiss between the limestone of Grenville and

Proctor's Lake limestone_________________ 1,580

8. Proctor's Lake limestone__________________ 20

9. Orthoclase gneiss passing gradually into anorthosite between Proctor's Lake limestone and the Morin band. 

This would probably include the quartzite of the Quartz 

Mountain, the Orthoclase gneiss above it, and the 

gneiss of passage - 3,400

The nearest geographical approach of the Grenville 

and Morin limestones that has been ascertained is 

about two miles; the present estimate of tlieir stratigraphical separation is 5000 feet, which is not perhaps 

extravagant.

10. Anorthosite above the Morin band of limestone; the thickness is wholly conjectural _____ __ 10, 000

32, 750

W. E. Logan, 1865 (Canada Geol. Survey Sixteenth Rept. Prog., p. 20 and 

map).

A detailed map, showing the distribution of the Laurentian rocks in parts of 

the counties of Ottawa, Ter'rebonne, Argenteuil [typical Grenville area], and 

Two-Mountains; together with portions of the adjacent Lower Silurian formations.

Lower Silurian: 

* * *

Potsdam.

Huronian (wanting). 

Upper Laurentian:

Anorthosite gneiss, etc. 

Lower Laurentian:

Fourth orthoclase gneiss.

Grenville limestone.

Third orthoclase gneiss

Green Lake limestone.

Second orthoclase gneiss.

Trembling Lake limestone.

First orthoclase gneiss.

A. It. C. Selwyii, 1879 (Canada Ocol. Survey Kept. 1877-78, pp. 9A-15A).

Laurentian. ["I I shall now make some observations on the results of the 

recent work of the Survey in unraveling the complications of the stratigraphy 

of the older " crystallines" on the north side of the St. Lawrence Valley. 

Since 1866, Mr. H. G. Vennor, of the Geological Corps, has been occupied in a 

careful examination of the stratigraphical relations of the Laurentian rocks. 

His observations, commencing in Hastings county, north of Lake Ontario, have 

now extended across the Ottawa River, eastward, to Petite Nation and Grenville, embracing a band of country 200 miles in length, with an average breadth

here used applies to all pre-Huronian rocks.]
116 GEOLOGIC TIME CLASSIFICATION

of fifty-five to sixty miles. Throughout this tract of country Mr. Vennor has 

followed and mapped, in all their windings and convolutions, the great series 

of Laurentian limestone bands first investigated and described by Sir W. E. 

Logan in the years from 1853 to 1856, more particularly in the Grenville region, 

and in 1865, by Mr. Macfarlane, in the Hastings region. The results and conclusions of all these earlier examinations are given in detail in the Geological 

Survey Reports. And these shew that the classification then adopted by 

Sir W. E. Logan was regarded by him as provisional. (See Note, p. 93, 

Geological Survey Report, 1866.)

Thus, at the commencement of Mr. Vennor's investigation in 1866, it was 

supposed that the limestones and calcareous schists of Tudor and Hastings 

holding eosoon, together with certain associated dioritic, felsitic, micaceous, 

slaty conglomerate rocks, were a newer series than those already examined and 

described by Sir W. E. Logan, and they were accordingly designated, in the 

report published in 1870, the Hastings series* and it was further supposed, from 

its apparent stratigraphical position and from certain lithological resemblances, 

that it might be of Huronian age. The gradual progress of the work, however, 

from west to east has now, I think, conclusively demonstrated that the Hastings group, together with the somewhat more crystalline limestone and gneiss 

groups above referred to, form one great conformable series, and that this 

series rests quite unconformably on a massive granitoid, or syenitic, red 

gneiss. * * *

We can, however, confidently state that these crystalline limestones and their 

associated strata occupy an unconformable position .between a massive gneiss 

formation below and unaltered Potsdam, or Lower Silurian, rocks above; and 

this may likewise be stated respecting the stratigraphical position of the typical 

" Huronian series" of N the Georgian Bay, which, together with its close 

proximity to the western-most known exposures of the crystalline limestone 

series which we now know, extends from Parry Sound to Lake Mppising, and 

includes some labradorite gneiss, renders it very probable that a connection 

will eventually be traced out, between even these supposed greatly different 

formations, similar to that now, as already stated, proved to exist between the 

Hastings and Grenville series. * * *

In the reconstruction of the geological map of eastern Canada, and in this 

I include the country from Lake Winnipeg to Cape Breton and Labrador 

rendered necessary by the present state of our knowledge, I should propose to 

adopt the following divisions of systems to include the groups enumerated 

[ascending order]:

I. Laurentian: To be confined to all those clearly lower unconformable 

granitoid or syenitic gneisses in which we never find interstratified bands of calcareous, argillaceous, arenaceous and conglomeratic rocks.

II. Huronian: To include 1. The typical or original Huronian of Lake 

Superior and the conformably or unconformably, as the case 

may be overlying upper copper-bearing rocks.

2. The Hastings, Templeton, Buckingham, Grenville and Rawdou 

crystalline limestone series.

3. The supposed Upper Laurentian or Norian.

4. The altered Quebec group, as shewn on the map now exhibited, 

and certain areas not yet defined between Lake Matapedia 

and Cape Maquereau in Gasp .

5. The Cape Breton, Nova Scotia and New Brunswick prePrimordial sub-crystalline and gneissoid groups.
THE PERIOD AND EPOCH TEEMS 117

III. Cambrian: In many of the areas, especially the western ones, the 

base of this is well-defined by unconformity, but in the Eastern 

Townships and in some parts of Nova Scotia it has yet to be 

determined. The limit between it and Lower Silurian is debatable 

ground, upon which we need not enter.

F. D. Adams, 1803 (Jour. Geologry, vol. 1, pp. 328-33O).

The Grenville Series. In certain parts of the Laurentian area, and notably 

in the Grenville district before mentioned, the Laurentian [ M ] has a decidedly 

 different petrographical development. Orthoclase gneiss is still the predominating rock, but it presents a much greater variety in mineralogical composition, 

and is much more frequently well foliated, often occurring in well defined 

bands or layers like the strata of later formations.

Amphibolites are abundant, also hornblende schists, heavy beds of quartzite 

and numerous thick bands of crystalline limestone or marble, all these rocks 

being interbanded or interstratified with one another. In the vicinity of the

limestones the variety in petrographical character is especially noticeable; 

garnets often occur abundantly in the gneiss, the quartzite and the hornblende 

schist, as well as in the limestone itself, beds of pure garnet rock being found 

in places. Pyroxene, wollastonite and other minerals are also abundant, while 

the presence of graphite disseminated through the limestones and their associated rocks, often in such abundance as to give rise to deposits of economic 

value, is of especial significance. This mineral which is not found in the 

Fundamental Gneiss, occurs usually in little disseminated scales but occasionally in veins. The limestones are thoroughly crystalline, generally somewhat coarse in grain and often nearly pure. They usually, however, contain 

grains of serpentine, pyroxene, mica, graphite or other minerals, of which over 

fifty species have been noted. They are often interstratified in thin bands 

with the gneiss, in places are very impure, and may be traced for great distances along the strike, being apparently as continuous as any other element 

of the series. This development of the Laurentian is known as the Grenville 

Series, and has been considered by all observers to be above and to rest upon 

the Fundamental Gneiss. In it are found all the mineral deposits of economic 

value apatite, iron ore, asbestos, etc., which occur in the Laurentian. The 

rocks of this series, though generally highly inclined, over some large areas 

lie nearly horizontal or are inclined at very low angles, but even in such cases 

they show evidence of having been subjected to great pressure, resulting in 

some cases in the horizontal disruption of certain of the beds.

The areas occupied by the Grenville series although of very considerable 

extent, being known to aggregate many thousand square miles, are probably 

small as compared with those underlain by the Fundamental Gneiss. The relative distribution of the two series has not been ascertained except in a general 

way in the more easily-accessible parts of the great Archean Protaxis. The 

Grenville series is known to occupy a large part of its southern margin between 

the city of Quebec and the Georgian Bay, while the discovery of crystalline 

limestone in the gneiss elsewhere at several widely separated points, as for 

instance on the Hamilton River in Labrador, in the southern part of Baffin 

Land and on the Melville Peninsula, makes it probable that other considerable 

areas will, with the progress of geological exploration, be found in the far 

north. Over the greater part of the Protaxis, however, the more monotonous 

development of the Fundamental Gneiss seems to prevail.

[ 03 As here used the term Includes all pre-Huronian rocks.]
118 GEOLOGIC TIME CLASSIFICATION

The question of the origin and mutual relations of the Fundamental Gneiss 

and the Grenville series is one about which, though mucli has been written 

but little is known. * * *

How much of the Fundamental Gneiss really consists of eruptive material 

is not known. * * * The evidence accumulated goes to show that the 

Fundamental Gneiss consists of a complicated series of rocks of unknown 

origin, but comprising a considerable amount of material of intrusive character.

F. D. Adams, A. E. Barlow, A. P. Coleman, H. P. Gushing, J. F. Kemp, and 

C. R. Van Hise, 1907 (Report of a special committee on the correlation 

of the pre-Camforian rocks of the Adirondack Mountains, the " Original 

Laurentian area" of Canada, and eastern Ontario: Jour. Geology, vol. 

15, pp. 215-217).

The committee considers that over the whole area covered by their investigations namely, the Adirondack Mountains, that portion of eastern Ontario 

which they examined, the " original Laurentian area" in the province of 

Quebec and its continuation to the east as far as the. river St. Maurice the 

pre-Cambrian sedimentary development is represented by one great series. 

This series is essentially identical in petrographical character throughout the 

whole region.

The only locality where the possible (Coleman would say probable) existence 

of a second unconformable sedimentary series was suggested by the facts observed, was that on the Queensboro road, east of Madoc, Ontario. It is, 

however, still a matter of uncertainty as to whether the conglomerate here 

developed marks the base of an overlying, infolded, unconfortnable series or not.

In Logan's original classification of the Laurentian this term apart from the 

Upper Laurentian which was proved to be composed essentially of anorthosite 

intrusions included two series differing in character, namely, the Lower 

Orthoclase (Fundamental) Gneiss and the Grenville series. Now that investigations have shown that these two series differ in origin, one being essentially 

a great development of very ancient sediments, and the other consisting of 

great bodies of igneous rock intruded through them, it becomes necessary to 

separate these two developments in drawing up a scheme of classification.

As the great intrusions of gneissic granite, forming what has been termed 

the " fundamental gneiss," have an enormously greater area! development than 

the overlying sedimentary series, constituting, as they do, a very large part of 

the whole northern protaxis, the committee recommend that the term " Laurentian " be restricted to this great development of igneous gneisses. The nomenclature suggested for the pre-Cambrian rocks of this eastern region will thus 

conform, so far as the use of this term is involved, with that suggested by the 

Special Committee for the Lake Superior region.

For the overlying sedimentary series the committee recommend the adoption of the name " Grenville series," as it is the name originally given by 

Logan to the series as typically developed about the township of Grenville in 

the " Original Laurentian area " on the north shore of the Ottawa River, in 

the Province of Quebec, between the cities of Montreal and Ottawa. The term 

" Hastings series " in the opinion of the committee should be abandoned as a 

serial name, seeing that the development to which this name was applied by 

Logan is merely the Grenville series in a less altered form, as Logan in giving 

the name had conjectured Avas probably the case. The committee, however, 

think that it may in some cases be advantageously employed as a qualifying term 

to designate the less highly altered phase of the Grenville series, which may 

thus be referred to as the " Hastings phase " of the Grenville series.
THE PERIOD AND EPOCH TEKMS 119

In Canada this Grenville series everywhere on going north is invaded by

and frays away into the great Laurentian bathyliths, while in the Adirondacks

it is cut to pieces by the great intrusions of that area which, when worked

; out in detail, may prove also to have a more or less similar bathylithic form.

The following succession in this region is therefore recognized and adopted

by the committee:

Cambrian Potsdam sandstones, etc.

(Unconformity) 

Pre-Cambrian:

Grenville series. 

(Intrusive contact). 

Laurentian.

The committee consider that it is inadvisable in the present state of our 

knowledge to attempt any correlation of the Grenville series with the Huronian 

or Keewatin, so extensively developed in the region of the Great Lakes. The 

Grenville series has not as yet been found in contact with either of these, and 

until this has been done and the relations of the several series have been carefully studied, their relative stratigraphical position must remain a mere matter 

of conjecture.

C. R. Van Hise and C. K. Lcith, 1909 (U. S. Geol. Survey Bull. 36O, it. 32).

Part of the Hastings and Grenville rocks of eastern Ontario and western 

-, Quebec are probably Algonkian, but their stratigraphy and correlation are not 

yet solved.

W. G. Miller, 1919 (Geol. Blag., London, dec. 0, vol. 6, pp. 525-526}.

The age relations of another historic series, the Grenville, have also been 

determined only during recent years. Most authors had suggested that the 

Grenville belonged to the so-called Huronian group of sediments, but it has 

proved to be the oldest sedimentary series. The Keewatin rocks, essentially 

schists and greenstones, represent, for the most part, submarine lava-flows. 

On the surface of these flows were deposited the Grenville sediments. While 

the major part of the Grenville is later than the major part of the Keewatin, 

a minor part of one group is contemporaneous with a minor part of the other.

\ C. Schuchert, 1924 (Textbook of geology, 2d ed., vol. 2, pp. 102, 145).

[On page 102 the Grenville series is placed in the "Archeozoic or Archean," 

and opposite the "Keewatin-Coutchiching series," but with the statement: 

' : May not be Archeozoic." On page 145 is the statement that the Grenville 

series "may prove to be Proterozoic (Huronian)."]

The foregoing quotations will serve to show, briefly, the origin 

and history of the name Grenville. The name was originally used 

for one of the limestones forming a part of the Grenville series of 

present usage. The United States Geological Survey treats the 

Grenville as a provincial series of pre-Cambrian metamorphosed 

sedimentary rocks, which it classifies as of Algonkian (?) age. According to Miller (1919, quoted above) the Grenville is chiefly of 

post-Keewatin age, but its basal part corresponds to some rocks 

which the United States Geological Survey classifies as Archean.

The name is derived from the development of the rocks in Grenville Township, Argenteuil County, Ontario.
120 GEOLOGIC TIME CLASSIFICATION

LLANO SERIES 

C. D. Walcott, 1884 (Am. Jour. Sci., 3d ser., vol. 28, pp. 431--432)i

The writer had the opportunity the past season to make a hurried reconnoissance of a portion of the Paleozoic area of Central Texas: the chief object 

in view being the study of the Cambrian section and the collecting of fossils 

from the Texas Potsdam horizon.

At all localities where the base of the Potsdam was observed, it rests, 

unconformably, on a great formation that is stratigraphically the equivalent 

of Powell's Grand Canon series (Grand Canon t 64 ] and Chuar groups). In the 

Gnmd Canon of the Colorado the latter are overlaid by the Tonto group, a 

series of rocks, in both lithologic and paleontologic characters, singularly like 

the Texas Potsdam group.

For this series of Pre-Potsdain strata the local name of Llano group is 

proposed from the best exposures of the group occurring in the county of 

Llano. Outcrops also occur in Burnet, Mason, San Saba, Blanco and Gillespie 

counties.

The finest exposure seen by the writer, in direct contact with the base of the 

Texas Potsdam group, is along the western base of Packsaddle mountain, in 

Llano county. Here the massive reddish colored sandstones of the Potsdam, 

strike north and south with a slight dip to the eastward, and rest on alternating beds of shale, sandy shales, sandstone, limestone and schists that strike 

east and west, dipping south 15° to 40°. The strata exhibit but little evidence 

of metamorphism, being indurated but little more than the beds of the overlying Potsdam and Carboniferous. The section shows the Llano and Potsdam 

groups unaffected by changes subsequent to the consolidation of the Potsdam 

sediments.

Across the valley of Honey Creek, four miles west of Packsaddle mountain, 

the strata of the Llano group have been more metamorphosed, plicated, and 

broken by intrusive dykes of granite. This is along the eastern base of a 

ridge of Potsdam, Silurian and Carboniferous rocks that strike eastward with 

a dip that increases from 10° at the north end of the ridge to 40° at the 

south end. The movement producing this position, as compared with the 

Potsdam beds of Packsaddle mountain, appears to have been at the close of 

the Paleozoic, and to have caused, in part, the metamorphism of the strata of 

the Llano group, but was not accompanied by the intrusive rocks, as they are 

Pre-Potsdam in part contemporary with the deposition of the sediments of 

the Llano group, but more largely the result of extrusions of granite at or near 

the close of the erosion of the Llano group and before the deposition of the 

Potsdam. It is to this age that the great masses of granite observed in western Burnet and all through Llano county belong. At the crossing of the Llano 

river, on the road from Burnet to Honey Creek Cove, fragments of the shales 

and sandstones of the Llano group may be seen imbedded in the granite, and 

on Morgan's creek, Burnet Co., the Potsdam rests directly on the granite.

The thickness of the Llano group was not determined owing to lack of time 

to study it in detail. In Honey Creek valley, from two to three thousand feet 

of shales, sandstone and limestones were observed, and northwest of the town 

of Llano a great mass of reddish sandstone occurs.

On Roessler's map of Llano county, all of the Llano group is referred to as 

" granitic, metamorphic and igneous," and has been considered as Archean. 

The writer did not observe any rocks of undoubted Archean age. No fossils 

were found in the Llano group, but, -from its lithologic character and position

[M Later renamed TJnkar group, to avoid the double use of Grand Canyon, for the series 

and for one of the groups of the series.]
THE PERIOD AND EPOCH TEEMS 121

in relation to the overlying Potsdam, I refer the group to the Paleozoic, and 

correlate it with the Grand Cafion groups, which are of Paleozoic age and 

referred to the Lower Cambrian.

In 1890 Comstock 65 assigned the Llano rocks to the " Eparchean 

group of the United States geologists," and "stated that he considered 

them equivalent to a portion of the Algonkian system. In 1899 

Walcott 66 changed his name Llano group to Llano series, and assigned it to the pre-Cambrian. In 1912 Paige mapped the rocks of 

the typical Llano area, and classified them as Algonkian (?), which 

is the age designation of the United States Geological Survey. 

Paige stated: 67

The Llano series has proved to be a completely metamorphosed series of 

schists, marbles, and gneisses and can be classified as Algonkian in contradistinction to Archean only on the very broadest evidence, such as the preponderance of rnet'amorphic sediments over igneous material. Roessler's 

description of these rocks as granitic, metamorphic, and igneous was therefore 

concise and, possibly except for his reference of the series to the Archean, 

correct.

Llano series is the name applied to the metamorphosed series of schists, 

marbles, and gneisses which represent the pre-Carnbrian sedimentary rocks of 

this region. The series, which is tentatively regarded as of Algonkian age, is 

divided into two formations, the Valley Spring gneiss and the Packsaddle schist.

The name is derived from the exposures of the rocks in Llano 

County, Tex.

" KLLLARNEY REVOLUTION "

W. G. Miller and C. W. Knight, 1914 (Ontario Bar. Mines Kept., vol. 22. 

pt. 2, p. 125 and chart).

The report cited gives the following classification (descending 

order) of the pre-Cambrian rocks of Ontario:

Keweenawan.

Animikean.

Intrusives (Algoman) :

Algoman of Lawson, 1913. '

Laurentian, in part, of some authors and

Huronian granite of others. 

Lorrain granite of Cobalt. 

Moira granite of Hastings county.

Names that have been 

employed for rocks of 

various localities!

Killarney granite of north shore of Lake

Huron.

Temiskamian. Includes part of the Huronian of Logan and Murray and

of many other authors. Part of the Lower Huronian of Van Hise and

Leith (U.S.G.S. Bull. 360). Temiskaming series of Miller. Sudbury

series of Coleman (The Nickel Industry, Mines Branch, Ottawa, 1913).

Intrusives (Laurentian). 

65 Comstock, T. B., Preliminary report on the geology of the central mineral region of 

Texas: Texas Geol. Survey First Ann. Rept, pp. 252, 276-282, 1890.

08 Walcott, C. D., Pre-Cambrian fossillferous formations: Geol. Soc. America Bull., vol. 

10, p. 218, 1899;

07 Paige, Sidney, U. S. Geol. Survey Geol. Atlas, Llano-Burnet folio (No. 183), pp. 2, 3, 

1912.
122 GEOLOGIC TIME CLASSIFICATION

Loganian:

Grenville (sedimentary). Includes most of the Hastings and Grenville of older authors, and the Couchiching of Lawson.

Keewatin complex (igneous).

This name [Algoman], introduced by A. C. Lawson (Int. Geol. Congress, 

1913), appears to the authors to be a good one. Their investigations in southeastern Ontario, as well as at Cobalt and surrounding region, have proved that 

granite and gneiss of post-Temiskaming and pre-Animikie age are of wide extent. Ten years ago the authors gave to granite of this age in the Cobalt area 

the name Lorrain granite, and later they gave to a granite of similar age in 

southeastern Ontario the name Moira. On the north shore of Lake Huron 

granite of similar age has been called Killarney. Algoman now being preferred, 

although not having priority, Lorrain, Moira, and Killarney may be discarded 

or used locally. In the descriptions of many areas Algoman granite and gneiss 

have in the past been classed as Laurentian, age relations not being definitely 

known.

W. H. Colllns, 1922 (Jour. Geology, vol. 3O, pp. 2O4-21O).

The sediments forming these [Lacloche] mountains are Precambrian (Huronian), and the intrusive granitic batholiths are late Precambrian (Killarney). 

[Page 204.]

If intense regional disturbance and batholithic invasion indicate mountainbuilding, it must be concluded that following Timiskamirig time the whole 

region, shown in Figure 3, was mountain-built. The southern portion was long 

afterward involved in the Killarnean mountain-building and, in that part, any 

evidence of this earlier orogeny was pretty completely demolished; but there is 

little doubt that the older mountains extended over the whole region. [Pages 

207-208.]

Following or during the Keweenawan another (third) process of mountainbuilding (Killarnean) took place which affected only the southern portion of 

the region. These Killarnean Mountains were reduced to a state of fairly low 

relief before the Ordovician marine sediments were deposited upon them. [Page 

210.]

The map on page 205 of the journal cited is entitled "Map of 

northeastern Ontario to show the known distribution of the batholithic intrusives, which are of three distinct ages and are related to 

three corresponding processes of mountain-building," and the map 

units are as follows:

Sediments and volcanics.

Killarney granite. <»

Pre-Huronian granite.

Pre-Dorean granite.

C. Sclinchert, 1924 (Textbook of geolo&y* 2d ed., vol. 2, pp. 1O2, 160, 171).

Eras

Proterozoic.

General terms for major 

divisions

Killarney Revolution.

Keweenawan series.

* * *

Lake Superior, after Leith

Keweenawan granite.

Keweenawan formations.

* * *

Lake Hurori-Michipicoten, 

after Leith

Killarnean granite.

Keweenawan (norites).

* * *

(Page 102.]
THE PERIOD AND EPOCH TEEMS 12 3

At the close of this fProterozoic"] era the Killarney mountains arose out of 

the Ontario geosyncline, dividing the vast interior of North America into a 

northern (Canadian Shield) and a southern (United States and Mexico) plain. 

(Page 160.]

Killarney Revolution. Collins (1922) has shown that the whole area of the 

Ontaric geosyncline from at least Sudbury, Ontario, into southern Wisconsin, 

was folded and injected by granite bathyliths, making the Killarney mountains. 

These have long been known as the " Lost Mountains of Wisconsin," and 

Lawrence Martin thinks they may originally have been as high as the present 

Alps. In a northeast direction the Killarney mountains are known to have 

extended at least 1,000 miles, from southwestern Minnesota (Sioux Fulls) to. 

beyond Lake Huron (see map, p. 193). [Page 171.]

"ALGOMAN REVOLUTION"

A. C. Lawson, 1914 (Coiif?. «&ol. Internat., 12th sews., Toronto, Conxjpf.- 

reiul., p. 361).

From the foregoing summary of observations, it is obvious that we have to 

deal with the products of two widely separated periods of plutonic activity in, 

the earth's crust, one post-Ontarian [post-Keewatin] and pre-Huronian, umE 

the other post-Huronian and pre-Animikie. The rocks of both periods were at. 

first confused and regarded as all belonging to the Laurentian. In later years,, 

notwithstanding the gradual recognition of the distinctness and time interval, 

between the two irruptive periods, the rocks of both continue to be called 

Laurentian. As long as this practice continues we shall never be able to clear 

up the problems of the Archsean; and the time has come when the second 

great period of batholithic development in the Lake Superior region must 

receive recognition not only in observational records but also in our nomenclature. In a report on the Rainy Lake region for the year 1911, submitted t»> 

the Director of the Geological Survey of Canada, I have proposed that this 

period be called the Algoman, from the old western Ontario district of Algomu, 

in which these plutonics are well displayed and widely distributed.

A. C. Lawson, 1916 (California, Univ. Dept. Geology Bull., vol. 10, Xo. I. 

chart opp. p. IS).

Adams (Problems of American Geology, p. 63) takes exception to placing the 

Laurentian and Algoman granites in the sequence of formations on the ground 

that they are intrusive masses and not members of the stratigraphic succession. It may be urged, however, that the sequence is chronological as well us 

stratigraphic and in the standard scale we need a term for these two periods 

of batholithic development. Perhaps the terms Laurentian Revolution and 

Algoman Revolution used in the tabulation will meet the objection.

W. G. Miller, 1919 (Geol. Mat;., London, dec. C, vol. 6, |>. 525).

The following classification is now employed by the Ontario Bureau of Mines: 

Keweenawan. 

Unconformity. 

Animikean.

Great unconformity. 

Algoman granite and gneiss. j

Timiskamian. 0 f

Great unconformity. * 

Laurentian granite and gneiss. <j|

Loganian: ;

Grenville (sedimentary). Deposited on the Keewatin lavasKeewatin (igneous). '

1140 25 9
124 GEOLOGIC TIME CLASSIFICATION" 

H. C. Cooke, 1920 (Jour. Geology, vol. 2S, pp. 328-329).

A brief discussion of the nomenclature of the granite of Timiskaming district may be added here, as closely related to the main purpose of this paper. 

The term Algoman has recently been applied by Miller, Burrows, and others, 

when referring to granites intrusive into the Timiskaming series but underlying the Cobalt series.68 The term Algoman was first used in the Rainy 

Lake district by A. C. Lawson, and was defined by him as applying to granites 

intrusive into the Middle Huronian but underlying the Upper Huronian or 

Animikie.69 The transfer of this term to Timiskaming district 500 miles to 

the east was made upon a correlation of the Cobalt series with the Animikie, 

since both series are flat lying and overlie a great unconformity, and a secondary decision that the Timiskaming, as a folded sedimentary series lying 

beneath the Anirnikean, was probably Lower Huronian. But with the determination of the Timiskaming series as pre-Huronian in age, while the intrusive granites are found in the Lake Huron area to underlie the -Bruce or 

Lower Huronian, it is clear that the use of the term Algoman is entirely 

unjustified.

In its place the writer would apply the term Laurentian to these granites.

W. G. Miller, 1911 (Eng. and Min. Jour., vol. 92, pp. 647-048).

The article cited gives the following classification (descending 

order) of the pre-Cambrian rocks in the Cobalt and surrounding 

areas of Ontario:

Nipissing Diabase. Quartz diabase of Cobalt sill, etc.

(Intrusive contact.)

Cobalt Series. Lower Huronian conglomerate, etc., of the cobalt silrer 

deposits. Lies in an almost horizontal position.

(Unconformity, erosion.)

Lorrain Granite.

(Intrusive contact.)

Temiskaming Series. Conglomerate, etc., of Kirk, Cross and Temiskaming lakes, etc. Dips at high angles. In previous reports included in 

Keewatin.

(Unconformity, erosion.)

Keewatin.

For the fragmental series, in which the cobalt-silver veins characteristically, 

occur, we propose to employ the name Cobalt Series, which we have heretofore 

used in a general way. For the older, more disturbed conglomerate series, 

which outcrops at Kirk and Cross lakes and in greater volume on Lake 

Temiskaming, outcrops also being known a considerable distance south of 

Cobalt and 90 miles to the northwest at Porcupine, the name Temisk'aming 

will be used. The granite intrusive into the Temiskaming series but not into 

the Cobalt series will be called the Lorrain Granite, a name under which it 

is already known. The quartz diabase of the sill at Cobalt, which is of such 

great economic importance anft is so widespread, not only in that viciru.ty but 

throughout a large territory in the district of Nipissing, will be called the 

Nipissing Diabase. This will serve to distinguish it from diabases of other 

ages that occur in the region.

88 Ont. Bur. Mines, Kept. No. 22,, Part 2, pp. 123-127, 1913. 

69 Geol. Surv. Can. Mem. No. 40, p. 82, 1913.
THE PEBIOD AND EPOCH TERMS 125

W. G. Miller and C. W. Knight, 1014 (Canada Bur. Mines Rept., vol. 22, 

Pt. 2).

The report cited contains the following classification of the preCambrian rocks of Ontario, western Quebec, and southeastern 

Manitoba:

Keweenawan.

Unconformity.

Animikean. (Upper Copper:bearing rocks of Lake Superior; Lower 

group, Geol. Can., 1863. Includes Middle and part of Lower Huronian 

of Lake Huron of various authors (U. S. G. S. Bull. 360). Animikie 

or Upper Huronian of Lake Superior, and of the Sudbury basin, 

Whitewater and Ramsey Lake series. Cobalt series of Cobalt and 

surrounding region.)

Great unconformity.

Algouian (intrusives). (Algoman of Lawson, Int. Geol. Con., 1913. 

Laurentian, in part, of some authors and Huronian granite of others. 

Lorrain granite of Cobalt. Moira granite of Hastings county. Killarney granite of north shore of Lake Huron). [In subsequent reports the latter granite has been assigned to the Keweenawan epoch.]

Temiskamian. (Includes part of the Huronian of Logan and Murray 

and of many other authors. Part of the Lower Huronian of Van Hise 

and Leith (U. S. G. S. Bull. 360'). Temiskaming series of Miller, Eng. 

and Miu. Jour., Sept. 30, 1911, and Ont. Bur. of Mines, vol. XIX, part 

2. Sudbury series of Coleinan, The Nickel Industry, Mines Branch, 

Ottawa, 1913).

Great unconformity.

Laurentian (intrusives). Granite and gneiss.

Loganian:

Grenville (sedimentary). Includes most of the Hastings and Gren-.

ville of older authors, and the Couchiching of Lawson. 

Keewatin (igneous).

A. P. Col cilia 11, 1915 (Problems of American geology: Yale TJiilv. I'ufo., 

pp. 8»-OO).

[See quotation under " Sudburia-H/' below] 

" SUDBURIAN "

A. P. Colemun, 1913 (The nickel industry: Canada Dept. Mines, Mines 

Branch, pp. 0 7).

This report was made " with special reference to the Sudbury 

region, Ontario." The rocks described are all assigned to the preCambrian, and are described as consisting, in descending order, of

Later dykes.

Norite-micropegmatite sheet.

Upper Huronian or Animikie, 8,750 to 9,450 feet.

Middle Huronian absent.

Lower Huronian. " In previous reports described as middle Huronian."

Laurentian.

Acid eruptives of the Sudbury series.

Basic eruptives of the Sudbury series.

Sudbury series.

Grenville series.

Keewatin.
126 GEOLOGIC TIME CLASSIFICATION

The " Sudbury series " is defined as follows:

SUDBURY SERIES

Later in age than the Grenville and Keewatin, but earlier than the Laurentian, is a great series of sediments, chiefly quartzite, but including also arkose, 

greywacke, slate, and some thin sheets of conglomerate. These are steeply 

tilted and sometimes folded, and have been penetrated and partly metamorphosed by acid and basic eruptives. They have hitherto been called lower 

Huronian, but they differ so much in attitude and relationship from the typical 

lower Huronian not far to the west that they probably belong to an earlier 

period, equivalent perhaps to the Timiskaming series, described by Dr. Miller 

and other geologists in the Cobalt region as lower than the Huronian. It is 

proposed to call them the Sudbury series.

The Timiskaming series and the rocks here referred to are not to be looked 

upon as a " Lowest Huronian," beneath the usually recognized bottom of that 

series, but as a new division of the Archaean equal in rank to the Huronian and 

Keewatin.

If these rocks are put in the position suggested it will imply also that the 

conglomerate near Ramsey lake, hitherto called middle Huronian, must be 

lowered one stage and be named lower Huronian. The Ramsey Lake conglomerate is more like the Cobalt and Echo Lake conglomerates of the lower 

Huronian regions hitherto carefully studied than are the sedimentary rocks 

underlying, giving support to the suggested change. * * *

These quartzites have a width of from 3% to 6 miles, and if they have not 

been duplicated by faulting, of which there is no evidence, have a maximum 

thickness of 15,000 or 20,000 feet, making them one of the greatest well defined 

sedimentary formations in Ontario.

Apparently beneath the quartzites there is a thinner, but still important 

bund of greywacke and slate, also well stratified and showing its original 

structures when not too much affected by adjoining eruptives. It has a width 

of two miles or more and a thickness of several thousand feet, and in various 

places it conies in contact with oft'set ore deposits but scarcely touches the 

main nickel range.

A third, and probably lower division of the sediments is more enigmatic, 

since it has undergone much greater changes, largely obliterating its original 

structure. This consists of quartzite or arkose. pink in color and greatly 

recrystallized, running northeast and southwest as a band of hills not more 

than half a mile wide from near Frood mine to a point southeast of Creighton. 

This rock touches Copper Cliff mine and was described earlier as felsite.

The three sedimentary formations may have a total thickness of 30,000 feet.

A. P. Coleman, 1915 (Problems of American greolojfy: Yale Univ. Pub., 

pp. S9-OO).

A Temiscaming Series of sediments very similar to those of Sudbury has 

been set apart by Miller and Knight and Burrows below the Cobalt (Lower 

Huronian) Series eighty miles to the north; and the Pontiac Series of Quebec 

not far to the east, as described by Morley E. AVilson, occupies probably the 

same position.

Since the Sudbury roijks have been longest known, have an estimated thickness of 20,000 feet, and cover a much larger area than the Temiscaming or 

Pontiac Series, the term Sudbury Series or Sudburian may be expanded to 

cover the whole and will have equal standing with the Keewatin below or the 

Huronian above. * * *
THE PERIOD AND EPOCH TERMS 127

As thus worked out, the pre-Cambrism groups may be arranged as follows: 

ISee table on p. 40 of this bulletin.]

ARCHEAN PERIOD (OR SYSTEM) 

.T. D. Dana, 1872 (Am. Jour. Set., 3d ser., vol. 3, p. 253).

3. Archwan rocks. Besides the limestones and Taconic schists and gneiss, 

there is, near Poughquag, in still more intimate connection with the quartzite, 

rocks of the Azoic age, a continuation of the Highland range of New Jersey a 

range recognized as Azoic first by H. D. Rogers, and shown to continue into 

Dutchess county by Logan and Hall (this Journal, II, XXXIX, 96). They 

are probably Laurentian, as stated by Logan and Hall, that is, they are equivalents of the oldest known Azoic rocks of Canada. But as this point is not 

definitely settled, and since the term Azoic has been ruled out by facts proving 

that the era was not throughout destitute of life, I propose to use for the 

Azoic era and its rocks the general term Arclwean (or Archean), from the 

Greek dpxalos, pertaining to the beginning. 

As thus originally defined the name Archean applied to all preCambrian rocks. In 1887 the rocks now designated the Algonkian 

system were separated from the Archean by R. D. Irving, under 

the name "Agnotozoic." In 1888 Irving again suggested for them 

the name "Agnotozoic," also "Eparchean." Both of these names 

were in 1889 discarded by the United States Geological Survey in 

favor of the name Algonkian. The definition of Archean now 

recognized by the United States Geological Survey is as follows:

Below the Algonkian, and separated from it by a profound unconformity 

in the majority of regions, is another system of rocks of radically different character. This system consists dominantly of schists and gneisses, the chemical 

composition of which, so far as tested, corresponds with igneous rocks rather 

than with sedimentary rocks. The lithologic variations of these schists and 

gneisses are exceedingly complex. Usually accompanying this lithologic complexity is exceeding intricacy of structure. In this matter of unparalleled intricacy of structure the system is unique. Many masses of igneous rocks belonging to later systems are intrusive in the ancient schists and gneisses. In 

various parts of the world minor masses of metamorphosed sediments are intimately associated with the remainder of the system."

No indisputable fossils have been found in the sediments of the 

Archean, but there is indirect evidence indicating the existence of 

some form of life, probably both plants and animals, during their 

deposition.

LAURENTIAN EPOCH (OR SERIES) 

W. E. L,ogan, 1S54 (Canada Geol. Survey Rept. Progress 1852-53, pp. 7, 8).

The country which lies between the upper end of the island of Montreal and 

Cape Tourmente on the left side of the St. Lawrence, and occupies the space 

intervening between the river and the flank of the metamorphic hills, to which

70 Whatever part of the Archaean beds are proved to belong to an era in which there was 

life, will be appropriately styled Archeozoic. This term avoids the objection which Eozoic 

derives from the doubtful nature of the Eozoum.

71 U. S. Geol. Survey Twenty-fourth; Ann. Rept., p. 26, 1903.
128 GEOLOGIC TIME CLASSIFICATION

Mr. Garneau in his History of Canada has given the name of Laurentides, has 

a length of about 200 miles, and it gradually widens from a point at Cape 

Tourmente, to about thirty miles at Montreal, having thus an area of about 

3,000 square miles. * * *

The name which has been given in previous Reports to the rocks underlying 

the fossilit'erous formations in this part of Canada is the Metamorphic series, 

but inasmuch as this is applicable to any series of rocks in an altered condition, 

and might occasion confusion, it has been considered expedient to apply to them 

for the future, the more distinctive appellation of the Laurentian series, a 

name founded on that given by Mr. Garneau to the chain of hills which they 

compose.

The geological formations which underlie the district in ascending order 

would thus be as follows:

1. Laurentian series.

2. Potsdam sandstone.

3. Calciferous sandrock.

4. Chazy limestone,

5. Birdseye, Black-River and Trenton limestones.

6. Utica slate.

7. Hudson-River group.

8. Oneida conglomerate.

In 1855 Logan and Hunt 72 divided the ancient rocks of Canada 

into Laurentian system and Cambrian or Huronian system, thus 

applying the name Laurentian to all pre-Huronian rocks. This 

usage continued for many years.

The definition of Laurentian adopted by the joint committee of 

American and Canadian geologists in 1905, and still followed by the 

United States Geological Survey, is as follows:

For the granites and gneissoid granites which antedate of protrude through 

the Keewatin, and which are pre-Huronian, the term " Laurentian" is adopted.

KEEWATIN EPOCH (OR SERIES)

A. C. Lawson, 1885 (Report on the geolog-y of the I^ake of the Woods region, 

 with special reference to the Keewatin. (Huronian?) belt of the 

Arclueau 'rocks: Canada Geol. and Nat. Hist. Survey, 1885, the same 

being part CC of Canada Geol. and Nat. Hist. Snrvey Ann. Rept., new 

ser., vol. 1, 1886, pp. 10CC-13CC, 14CC-15CC).

SEASONS FOR PKOPOSING THE NAME " KEEWATIN "

The belt of schistose rocks which runs through the granitoid gneiss, across 

the northern parts of the Lake of the Woods has, as above stated, been regarded 

as of Huronian age. In this report, upon the first detailed investigation of 

the belt as a whole, I feel it incumbent upon me, at the outset, to say a few 

words on the nomenclature of the series of rocks comprised within it, and 

particularly to question the advisability, in the light of recent investigations, 

of relegating these rocks to a position stratigraphically and geognostically 

equivalent to the typical Huronian of Sir William Logan, as described in the 

Geology of Canada, (1863). It must always be an extremely difficult matter 

to demonstrate the equivalency or non-equivalency of any two widely separated

72 Logan, W. E., and Hunt, T. S., Esquisse geologique du Canada, Si 1'Exposition Universelle de Paris, Paris,. 1855.
THE PERIOD AND EPOCH TERMS 129

sets or series of Archaean rocks, devoid of fossils. Lithological similarity has 

by no means been established as a criterion of geological equivalency, except 

in a very general way of little or no value in specific comparisons of given 

series of rocks. On the other hand, it seems reasonable to suppose (and indeed 

the rocks themselves establish the fact), that volcanic activity played a much 

more important part in the development of the formations of Archaean times 

than in that of later geological ages; and farther, since these volcanic rocks 

were mixed with ordinary aqueous sediments, and the volcanic action was 

intermittent and irregular, we would expect to find series of the same geological 

age, of all gradations of lithological character, from an "almost wholly volcanic 

to an almost wholly sedimentary composition. Thus the extreme dissimilarity 

of series so composed would be no proof of geological disparity. Lithological 

character is only one of several considerations that must be taken into account 

in a question of the correlation of two geological series geographically separated. 

The schistose belt of the Lake of the Woods appears to me to differ from the 

typical Huronian of Sir W. Logan, both lithologically and in other respects.

The typical Huronian of Logan is, from his description of it, essentially a 

quartzitic series, in which the quartzites are true indurated sandstones. The 

schistose belt of the Lake of the Woods is not so characterized. Quartzites 

form an extremely small proportion of the rocks of the Lake of the Woods, and 

then they are only local developments in formations of mica-schist and felsitesehist. Bedded limestones are characteristic of Logan's typical series. On the 

Lnke ol the Woods there are. so far as I have been able to determine, no 

bedded limestones, the nearest approach to them being small segregated bands 

of dolomite, of the character of vein-stones. These two differences alone are 

sufficient to throw doubt on the equivalence of the two series, if lithological 

character is to be regarded as an aid to geological reclassification. There are, 

however, other differences. The basal conglomerate of Logan's Hurouian, on 

Lake Temiscamang, is described as " holding pebbles and boulders, sometimes 

a foot in diameter, of the subjacent gneiss, from which they appear to be 

derived. The boulders display red orthoclase feldspar, translucent, colourless 

quartz, green hornblende and brownish-black mica, arranged in parallel 

layers, which have a direction according with the attitude in which the boulders 

were accidentally enclosed." The rocks on the Lake of the Woods, which are 

in the following pages referred to as " agglomerate-schists," are not basal conglomerates. They are not at the base of the series included in the schistose 

belt, nor are they apparently composed of water-worn fragments, derived from 

the rocks upon which they rest.

No fragments that can be referred to the underlying granitoid gneisses are 

found included in the agglomerate-schists of the Lake of the Woods. All the 

facts connected with them point to a volcanic origin for these agglomerates, 

and the fragments are very frequently sharply angular, often with re-entering 

angles although, for the most part they are elongated and lenticular in shape 

as a result of pressure, and the paste in which they are imbedded does not 

differ from them materially in composition as a rule. In rare instances they 

pass into pebble- or boulder-conglomerate, in which the pebbles are usually of 

a reddish felsitic material and indicate the co-existence of aqueous, with volcanic deposition.

The " green slate rock " conglomerates at the mouth of the Dor6 River, Lake 

Superior, described by Sir W. Logan, supposed by him to be equivalent to the 

rocks of his main Huronian area, appear to resemble the agglomerate-schists 

of the Lake of the Woods. This Dor£ River area of " green slate rocks " is, 

however, geographically distinct, and appears to differ from the series in the
130 GEOLOGIC TIME CLASSIFICATION

typical Hurouian region. The rocks are described as standing in a nearly 

vertical attitude, while those of the latter are comparatively flat. Neither 

sire they associated with beds of quartzites or limestones to a material extent. 

Those differences, with the geographical separation, may, I believe, warrant us 

in considering the possibility of Logan having embraced under one designation 

two distinct series and in regarding as Huronian, for the present, at least, only 

his main Huronian area, which is mapped in detail. ,

As a general rule the basal member of the schistose series of the Lake of 

the Woods is a group-of black hornblende-schists with associated trap-rocks, 

principally altered diabases and diorites. In Logan's Huronian, this formation 

apjtears to be wanting in this stratigraphical position, or fin-ds its analogue 

in "a mass of rather coarse-grained greenstone or diorite, usually interposed 

between the Laurentian gneiss and the recognized Huronian rocks, on the 

Sturgeon, Wahnapitae, and White-fish Rivers; but whether this is an overflow 

constituting the base of the upper formation, or an eruptive mass in the 

form of a dyke intruded at a later period, has not been ascertained.

Mica-schists, hydromica-schists and clay-slates appear to be but sparingly, 

or not at all represented in Logan's typical Huronian series. In the Lake of 

the Woods belt they are extensively developed and form an important constituent of the series.

There is, however, one point of resemblance. In Logan's series there is 

2.000 ft. of " chloritic and epidotic slate, interstratifled with trap-like beds." 

In the Lake of the Woods belt, there is abundance of chlorite. The hornblende-schists, diabases and diorites are generally very much decomposed, 

and the rocks are as a result largely chloritic. In addition to this, there are 

formations particularly interbedded with the hydromica-schists of soft, finely 

fissile, green schists, which appear to be altogether chloritic.

In the face of so many important points of difference, I hesitate to believe in 

the equivalency of the two series, although quite prepared to admit the possibility of two series of geologically the same age having widely different 

lithological characters in geographically separate regions.

There are, moreover, other considerations. There are two conditions which 

appear to be generally characteristic of the Laurentian gneisses of North 

America: 1. They are sharply folded. 2. They are cut by intrusive granites. 

Now the Lake of the Woods belt of schists is folded with the granitoid gneisses 

and is cut by several very large masses of granite and many smaller dykes. 

That is to say, the present schistose rocks of the Lake of the Woods were laid 

down upon the granitoid Laurentian gneisses, whatever may have been the 

orig nal form of these, before the main era of folding was inaugurated and 

before the granites (probably as a concomitant of the folding) were forced up 

from below. It is extremely doubtful that this is true of Logan's Huronian 

series, from his description of it. The series is flat-lying or gently undulating, 

and its basal member contains " boulders of the subjacent gneiss, from which 

they appear to be principally derived."

Further, Logan's mapped area of Huronian is not characterized by the presence of large masses of granite, although in the immediate vicinity of one part 

of this area " the intrusive granite occupies a considerable area on the coast 

of Lake Huron, south of Lake Pakowagaming. It there breaks through and 

disturbs the gneiss of the Laurentian series, and forms a nucleus from which 

emanates a complexity of dykes, proceeding to considerable distances. Aa 

dykes of a similar character are met with intersecting the rocks of the Huronian 

series, the nucleus in question is supposed to be of the Huronian age, as well 

as the greenstone dykes which are intersected by it." Similarly, just beyond
THE PERIOD AND EPOCH TERMS 131

the northern border of Logan's Huronian area, " cliffs of syenite and granite " 

are recorded as observed on the Mississague River, although none are stated to 

cut the Huronian strata in the neighborhood. Logan does not state in so many 

words that the underlying gneisses are folded, but both on his map, by the 

plotted dips, and in his sections 1 and 1 A, he shows that such he conceived to 

be their condition.

It thus appears that while the Lake of the Woods schists are older than 

the time of folding and older than the granites which are intruded through 

them, Logan's typical Huronian has come into existence later than the time 

of folding of the gneiss and possibly also later than the main period of granitic 

irruption. If then we suppose as there is every reason for doing, that the 

time of folding of gneiss and irruption of the granite was in a general way 

the same over this portion of the continent, we have the Huronian series and 

the Lake of the Woods series at once relegated to two Very distinct geological 

ages.

F. D. Adams, Robert Bell, A. C. Lane, C. K. Leith, W. G. Miller, and C. R. 

Van Hise, 10O5 (Report of the special committee for the Lake Superior 

region* Jour. Geology» vol. 13, pp. 1O3-1O4).

4

Unconformably below the Huronian is the Keewatin. The Keewatin includes 

the rocks so defined for the Lake of the Woods area and their equivalents. 

We believe the Kitchi and Mona schists of the Marquette district, the green 

schist (Mareniscan) of the Penokee-Gogebic district, the greenstone series of 

the Mesabi district, the Ely greenstones and Soudan formation of the Vermilion 

district, the part of the area mapped as Keewatin by Lawson in the Rainy Lake 

district not belonging structurally with the Couchiching, and probably the Thessalon greenstone series on the north shore of Lake Huron, to be equivalent to 

the Keewatin of the Lake of the Woods, and, so far as this is true, they should 

be called Keewatin.

In the Rainy Lake district, the Huronian should include that part of the 

Oouchiching of the south part of Rainy Lake which is limited below by basal 

conglomerate as shown at Shoal Lake.

C. R. Van Hise and C. K. Leith, 19O9 (U. S. Geol. Survey Bull. 3«0. pp. 377-

378}.

Keewatin. This name, first applied by Lawson to the greenstones, green 

schists, and iron formation of the Lake of the Woods area, has been by other 

writers applied to green rocks of different ages. In northern Minnesota tho 

term " Keewatin," as used by N. H. Winchell, includes rocks of the basement 

romplex and of the Huronian. Van Hise, believing that the term Keewatin 

was not originally applied to a structural unit, and believing also that its usefulness had been impaired by its promiscuous application to green rocks of 

different ages elsewhere, proposed the term " Mareniscan " to cover the greenstone, green schist, and iron formation portion of the basement complex. 

When Lawson's original Keewatin area of the Lake of the Woods was examined 

by the joint committee of Canadian and United States geologists ["] it \VMS 

ascertained that the Keewatin of this area is a structural unit, and the term 

Keewatin was recommended to cover all of the greenstone, green schist, and 

iron formation portion of the basement complex in place of " Mareniscan." 

This Is the sense in which Keewatin is now generally used.

t 73 Consisting of F. D. Adams, Robert Bell, W. G. Miller, C. K. Leith, A. C. Lane, and 

C. B, Van Hise.]
132 GEOLOGIC TIME CLASSIFICATION

The name is derived from the great development of the rocks in 

the Keewatin district, Canada.

" COUTCHICHING SERIES 5 ' 

A. C. Irfatvson, 1887 (Am. Jour. Sci., 3d ser., vol. 33, pp. 473 48®).

In the Rainy Lake Region there can be distinguished five groups of rock 

formations which are geologically distinct from one another. * * * [Page 

473.]

The group of rocks comprised in the table [petrographic] given above is 

designated geologically as the Laurentian System in accordance with the practice in vogue among geologists of so naming the lowest well-defined system of 

crystalline rocks which is clearly separable from overlying strata. It is not 

intended by the use of this term to imply that the rocks are necessarily of 

the same age as those described as the typical Laurentian by Logan, or as 

those named Laurentian in any other part of the world. For it is manifestly 

at variance with scientific methods to definitely correlate, with reference to 

age, rocks in which there are no criteria for comparison other than their 

petrographical characters. * * * [Pages 475-476.]

Superimposed upon the rocks thus referred to the Laurentian system, the 

splendid exposures of the shores of Rainy Lake reveal, as the next geological 

group a thick series of very distinctly stratiform mica schists and fine grained, 

gray, evenly bedded, often garnetiferous, very quartzose granulitic-gneisses. 

» a * [Page 476.]

This thick series of mica schists and granulitic gneisses attains its greatest 

development so far as has yet been observed in the southern part of Rainy 

Lake, where its thickness in continuous exposure, with the strata at low 

angles which preclude the idea of reversed dips, can be measured for a thickness of over two miles in a low anticlinal. The series is for convenience 

designated the Coutchiching series, from the Coutchiching Rapids at the head 

of Rainy River where the rocks are first met with on entering Rainy Lake 

from the west. They are very sharply and distinctly marked off from the 

lower granites and gneisses of the Laurentian. The geological contact between the Coutchiching series and the Laurentian system is one of neither 

conformity nor unconformity. The break is of an entirely different order, 

and the contact is eminently that of an igneous injection or intrusion of 

the lower through the upper rocks. This series appears to thin out rapidly 

toward the north, and on the north shores' of the southern part of Rainy 

Lake, in the neighborhood of Seine, Swell, Red-gut and Rocky Islet Bays, and 

in the islands of the lake, it is seen to form a trough in which lies folded another higher series of entirely different character. The rocks comprising it 

are for the most part of volcanic origin. They are chiefly black-green, compact, hornblende schists; softer, less compact, and more fissile green schistsin which hornblende is the prevailing constituent, but with chlorite, calcite, 

epidote and other decomposition minerals well represented in them; and, in 

intimate association with these schists and interbedded with them, great 

sheets of "trap" comprising uralitic diabases and gabbros (often called diorites) and other massive altered basic volcanic rocks of less determinate 

characters. These altered traps are sometimes quite massive and sometimes 

schistose to a varying extent, in which case the crushed or stretched condition 

of the rock is so clearly displayed in microscopic sections as to leave no doubt 

that the schistosity is due to pressure and to stretching or pulling forces upon
THE PERIOD AND EPOCH TERMS 133

the rocks after the assumption of a firm crystalline condition. When the 

crushing has been excessive the original character is often almost or completely obliterated, particularly, as the comminution of the rock under such 

forces is accompanied by the development of secondary minerals like quartz, 

calcite, epidote, zoisite, chlorite and albite. Included also in this series are 

dark green, very fissile glossy schists holding water-worn pebbles; green 

volcanic breccias; finer textured clastic rocks or "graywackes;" sericitic 

schistose quartz-porphyries and regular porphyroids; and soft, fissile, nearly 

always much decomposed hydromicaceous schists with which are associated 

yellowish dolomitic segregations.

The breccias, graywackes, and hydromica schists are more commonly met 

with in the northern part of the Rainy Lake Region than on Rainy Lake itself. 

This group of rocks is the same as a large portion of the series described in 

my report en the Lake of the Woods Region as the Keewatin series, and in the 

nortliern part of the Rainy Lake Region can be traced in direct continuity with 

that series. They will therefore be referred to as the Keewatin series of rocks. 

Concerning the geological relations of the Coutchiching and Keewatin series it 

is not possible to make any sweeping statement as to their conformity or unconformity. The Coutchiching rocks do not appear to have been at all disturbed 

prior to the deposition of the Keewatin, and the parallelism of the strike and dip 

of the strata or beds of the two series is. often seen to be perfect. But as 

Geikie points out the geological conformity or unconformity of two sets of strata 

implies a broader question than the mere relations in space of their contiguous 

portions. Strata which are in close contact and show at certain places perfect 

parallelism may sometimes be separated by ages. The appearance of parallelism is often simulated by pressure and folding so that it is not always a criterion 

of continuity of geological history. The very diverse character of the two 

series, the Coutchiching and the Keewatin, is proof of a profound alteration in 

the conditions of rock formation, which implies a geological break, though it 

does not indicate its duration. The Coutchiching series is seen occasionally to 

be cut by intrusions of a certain character which have not been detected traversing the Keewatin rocks. These may possibly be instances of vents from which 

the traps of the Keewatin series were extravasated. In the northern part of the 

Rainy Lake Region the Keewatin series comes into direct contact with the 

Laurentian without the intervention of the Coutchiching series, and the conditions of contact are those which have been described as obtaining in the Lake 

of the Woods Region. The contact of the hornblende schists and altered traps 

with the Laurentian rocks is of the same igneous or brecciated character as that 

observed on the Rainy Lake between the Coutchiching and the Laurentian, the 

direct inference being, of course, that the Laurentian rocks are of more recent 

age as such than either the Coutchiching or Keewatin, although stratigraphically 

they are inferior to both. * * * [Pages 477-478.]

The rocks of the region or their equivalents appear in their eastward 

geographical distribution in the neighborhood of Lake Superior to pass in a 

folded state under the flat lying beds of the Animikie series, the contact 

being one of marked unconformity. The Animikie is, according to the prolonged 

and valuable researches of Prof. R. D. Irving, of the United States Geological Survey, the geological equivalent of the typical Huronian of Logan.

The Animikie or Huronian is, according to the same eminent authority, distinct from and underlies the Keweenawan (Nipigon). Hence the classification 

of the various geological systems or series of rocks in the country west of
134 GEOLOGIC TIME CLASSIFICATION

Lake Superior, so far as our present knowledge goes, is with reference to 

their place in the ideal geological column, as follows:

Keweenawan (Nipigon).

Huronian (Animikie).

Keewatin.

Coutchiching.

Laurentian. 

With reference to their age, as follows:

Keweenawan (Nipigon).

Huronian (Animikie) :

Diabase dykes and gabbro. 

Granite, post-Laurentian.

Laurentian.

Keewatin.

Coutchiching.

F. D. Adams, Robert Bell, A. C. Lane, C. K. Leith, W. G. Miller, and C. R. 

Van Hlse, 1905 (Jour. Geology? vol. 13, pp. 95, 1O3).

In the Rainy Lake district the party observed the relations of the several 

formations along one line of section at the east end of Shoal Lake and at a 

number of other localities. The party is satisfied that along the line of section 

most closely studied the relations are clear and distinct. The Couchiching 

schists form the highest formation. These are a series of micaceous schists 

graduating downward into green hornblendic and chloritic schists, here mapped 

by Lawson as Keewatin, which pass into a conglomerate known as the Shoal 

Lake conglomerate. This conglomerate lies upon an area of green schists and 

granites known as the Bad Vermilion granites. It holds numerous large wellrolled fragments of the underlying rocks, and forms the base of a sedimentary 

series. It is certain that in this line of section the Couchiching is stratigraphically higher than the chloritic .schists and conglomerates mapped as 

Keewatin. * * * [Page 95.]

In the Rainy Lake district, the Huronian should include that part of the 

Couchiehing of the south part of Rainy Lake which is limited below by basal 

conglomerate us shown at Shoal Lake. [Page 103,1

('. K. Lvlth, 1O14 (ToiiK'. jreol. intermit., 12th ses.s.. Toronto, Conipt.-vend., 

pp. 410-411).

A large part of the series which Lawson originally classed as Coutchiching, 

in fact one of the largest ureas he described as typical Coutchiching, he now 

Mdm'ts is later than and unoonformably upon the Keewatin. He calls it the 

Seine series. This part of the Coutchiching he says is nnconformably above 

another part of the original Coutchiching series. From a detailed considerat on of his field work we are doubtful whether he has succeeded in proving, 

this unconformity. * * *

Other parts of the original Coutchiching have been found to be merely 

schistose phases of Keewatin basalts and not sedimentary. These parts 

are now eliminated from the Coutchiching. More such parts are likely to be 

eliminated.

After taking from the Coutchiching the rocks above mentioned, it is doubtful 

how much, if any, of the ser'es is left to meet Lawson's definition of Coutchiching.

If it should prove that there is a residuum of Coutchiching sediments actually beneath the Keewatin of Rainy lake, it remains to be proved that they 

are below the lowest Keewat'n, and that they are not interbedded sediments
THE PERIOD AND EPOCH TERMS 135

in the Keewatin on a somewhat larger scale perhaps than known sediments 

in the Keewatin in the Vermilion- and other districts. * * * In the event 

that some of the Coutchiching sediments being proved to be beneath the Keewatin of this particular locality, the most that can be said is that here are sediments conformably beneath at least a part of the Keewatin, with no evidence 

that they are anywhere near the bottom of the Keewatin, or that they constitute anything more than interlayered sediments.

" LOGANIAN "

W. G. Miller and C. W. Knight, 1914 (Ontario Bar. Mines Kept., vol. 22, 

pt. 2, p. 127).

The Loganian. Since the relation between the Grenville and Keewatin is 

such that, for the most part, they are not separated by an unconformity or an 

eruptive contact, it seems best to group them under one general heading, 

Loganian, giving to the sediments the old name Grenville and to the igneous 

material the name Keewatin. Moreover, since similar sediments to those to 

which Lawson gave the name Couchiching are found as one of the members 

of the Grenville, it does not seem to be necessary to retain the name Couchiching, except for use locally in northwestern Ontario. It is held by Lawson 

that the Couchiching in certain northwestern Ontario localities is older than 

the Keewatin represented there, but the authors are of the opinion that on 

the whole the pre-Laurentian sediments, Grenville and Couchiching, are younger 

than the Keewatin, although a minor part of the Keewatin may be intrusive 

into the sediments. In this connection it should be noted that, especially in 

localities where Temiskamian sediments are absent, certain post-Temiskamian 

igneous rocks may readily be mistaken for Keewatin rocks.

M The name Ontarian was proposed by A. C. Lawson (Bull. G. S. A., Vol. I, pp. 

176-177) for the pre-Laurentian rocks of northwestern Ontario. But the name Ontario, 

introduced In 1843, is employed by the geological survey of an adjoining State, New 

York, as synonymous with Siluric. In order to avoid confusion, it does not seem advisable 

to retain Lawson's name. Since the Grenville, especially, is characteristic of the district 

in southeastern, Ontario and the adjoining part of Quebec first described by Logan, we 

propose the name Loganian for the pre-Laurentian rocks.

INDEX

A Page 

Acadian, term proposed...._ 98-100

Acknowledgments 7 

Adams, F. D., cited........... ...... 37,117-118

and others of committee, cited........... 105,

106-107,118-119,131,134 

"Agnotozolc," term proposed.. .... 14-15

"Agnotozoicera," diverse uses_______ 15-17 

Alberti, F. von, cited___..._...... 64

"Alexandrian," term proposed. -----_. 82-83

"Algoman," term proposed.*____.___ 123 

Algonkian, term adopted and defined........ 103

Algoukian system, divisions__.__..__ 104 

"Anthrncolithic," term proposed.._..._ 78 

Arcbean system, origin and definition of term. 127 

"Archeozoic," term proposed____..._ 17 

"Archeozoic era," diverse uses.............. 17-20

Arduino, Glovanni, cited____.______ 49

time classification...__... .......... 2

"Azoic," term proposed..................... 20-21

"Azoic MU," diverse uses ____.__....... 21-26

B 

. Barrel!, J., with Schuchert, C.,cited........ 38-39

Belt series, term proposed'and defined__ 103-112 

Beyrich, E., cited............................ 53-54

Breaks in the geologic record.... ...... 7

Briggs, C., Jr., cited.. ....... ........ 75-76

Brooks, T.B., cited...-..-.... ......-.... 104

Builders of the time table_.___........ 2-3

C 

Cambrian, .term proposed___......._.. 92

Cambrian period, limits and divisions....... 94-96

"Canadian, "term proposed________ 87 

Carboniferous, term proposed____ _ 65H58 

Carboniferous period, divisions. . . 68-70 

Cennzoic, term proposed________._ 8 

Gcnozoic era, definition _.___.. __ 8 

Chamberlin, T. C., cited.............. 15-16,19,38

and Salisbury, R. D., cited.......... 18-19,60

"Champlainic," term proposed.......__ 88-8'J

Cincinuatian, term proposed.. . .... 85

Cincinnatian series, limits___.__..__ 85-80 

Clarke, J. M., and Schuchert. C., cited... 8tt,88,89 

Classifications, development_ . _. v 

Cleland, H. F., cited.__.....__..._.. 41

Coloman, A. f,., cited... ......... 33.40,125-127

and Parks, W. A., cited................. 42

Collins, W. H., cited........................ 122

' Collozoic," term proposed _____..__ 26-27 

Comancbe series, term proposed.. ... 59-60

use of term.....__ .... 60-61

Conybeare, W. D., and Phillips, W., cited.. 65-68 

Cooke, H. C., cited.............. ......... 12i

Cotta, B. von, cited.-.____ . ._ 23 

"Coatchiching scries," term proposed..-. 132-134 

Credncr,H.,cited..............__... 22,23,26,37

Cretaceous, history of name_....... _ 57-^58

term proposed......... ___.- -.... 58-57

D 

Dana, J.D., cited......................_.. 17-18,

21-22,23-24,25,28.81,87-88,127 

Dawson, J. W., cited.......... T .... 16,27,28,98-99

Desnoyers, J., cited_.___________ 43-44 

de Verneuil, E., with Murchison, R. I., and

Keyserling, A. von, cited.. 20-21,71-72 

Devonian, term proposed-_ _______ 78-80 

D'Halloy, J. J. d'Omalius, cited . . 56-57 

d'Orbigny, A., cited.._......__......... 21

E Page 

Emmons, E., cited.______.. 81,88-89,101-102 

Emmons, S. F.. cited__ _ .... 81-32 

Endlich, F. M., cited........................ 43

"Eobiotic," term proposed. ... . 27 

Eocene, term proposed.............. . 50,52,54

"Eomorpbic," term proposed____._... 27.

"Eozoic era," diverse uses _________ 27-80

term proposed ...____________ 27

F 

Forbes, Edward, cited............._._... 48

Foster, J. W., and Whitney, J. D., cited..... 21

Q 

Oabb, W. M., cited....*..................... 61

Gcikie, A., cited..........._...........__ 83

"Georgian," term proposed_____ 94-fl6,100 

Olaciation, stages._______........__ 45-46

Glenarm series, term proposed ............ 112-113

Orabau, A., cited __..__.___.._.. 41 

Grand Canyon series, origin of name and

age........................... 113-114

Grenville series, origin of name and age.... 114-119

Gulf series, term proposed. . . ... 58,59

H 

Hall, James, cited........................... 86-87

Haug, E., cited.............................. 16

Hennig, A., with TSraebohm, A. E., cited.. 25 

Hill, R. T., cited............................ SO

Hitchcock, C. H., cited.._._._._.__ 27 

Hitchcock, E., and C. H., cited_______ 22 

Humboldt, A. von, cited.. 62 

Hunt, T. Sterry, cited..................... 104-105

with Logan, W. E., cited.............. 105-106

Huronian, term proposed______..... 105-106

Huronian series, limits.........___.__ 106-108

"Hypozoic," term proposed ________ 80

I 

Irving, R. D., cited......................... 14-15

J

Jonas, A. I., with Knopf, E. B., cited - 112 

Jurassic, origin of term....... ............ 62-94

Jurassic period, boundaries.......... .... 64

K

"Kainozoic." SeeCenozoic. 

Kayser, E., cited........._....... 19,25,26,28,37

Keewatin, limits______....______ 131

term proposed... . 128-131 

Keweenawan, limits........__......__ 105

term proposed ... 104 

Keyserling, A. von, with Murchison, R. I.,

and de Verneuil, E., cited. 20-21,71-72 

" Killarney revolution," origin of term.. 121-123 

Kirwan, Richard, cited____.____ .. 65 

Knight, C. W., with Miller, W. G., cited... 88, 

39-40,121-122,125,135 

Knopf, E. B., and Jonas, A. I., cited 112

L 

Lane, A. C., cited....................... . 26

Lapwortb, C., cited.. . .. 83-84 

Laurcntian series, term proposed and defined........... ............... 127-128

Lawson, A. C., cited...._ 41,123,128-131,132-184

Le Conte, J., cited...... ........... 9,18,28

Leith, C. K., dted........................ 134-135

with Van Hise, C. R., cited..... 36-37,119,18i

Llano, term proposed 120-121 

Llano series, age 121

137
138 INDEX

Page Pag*

Logan, W. E., cited............ 114-115,127-128 Recent, term proposed._................... «-47

and Hunt, T. s-terry, cited............ 105-106 Rock terms, divisions.....____............. 3-4

"Txiganian," term proposed. .... .... 135 Rocks, sedimentary, thickness. .._...... ri-r

Lyell, C., cited........ ... 46-49,51-52 " s

M St. Croi\-ars, substitution of term for "SaraMatthew, W. D., cited... . ..... ...... 56 :.oi:!iji"_......................... rc-Os-

.Meek, F. B., aud Worthen, A. 11., cited..... 85 Salisbury, H. I)., with Charnhwlin, T. C.,

Mesozoic, term introduced.........._..... S cited._........................ is-i'.iMesozoicera, limits and life of...__....... 9-10 '.Sar:itogau. M term propost' 1................ 90-97

Miller, \V. G., cited.-.-.. . . 12:5,124 Savage. T. E., cited....... ......... ".'.'.".'." S2-k

and Knight, '..". W.. cited..._.._..... 3St Sehimpev. \V. P., wr.rd...,........_........ ol-se

39-40,121-122,125,135 Sciiudicrt. ('.. dt's'd........ 21K50,10-41,119.122-125

Miocene, term proposed. ..... ...... 52,53 nud Bun-oil, J., cited...................... 3«s--;;<j

Mississippian, term proposed.. .. 73 with Chirk.-, J. M., cited ......... SG.SS,S9, 101

Mississippian epoch, relations of fauna iind Scope of UK-, compilation... __.... v-vi, ]

flora.............. .... 69-70 Sederhohn, .i. J- citoi........................ 3&-31

Mohawkian.term proposed and defined..... 8o-87 Se-Jgwick. A., died...... ........... 10-11,42,92-94

Morlot, A., cited... - ....... 45 and Murchison. K. I., cited.............. 7S-SO

Morion, S. G., cited. ..... ............ 57-58 Selwyn, A. K. '..'.., i-it^d...........__....... 115-117

Murchison. It. I., cited . .... 70-71,80 Shasln, term propostxl....................... r,i

de Vcrneuil, E., and Keyserling, A. von, Shastascrips, tisi- of term..._.............. . f>!

cited..---..-. ......... 20-21,71-72 Silurian system, term proposed and defined 80-81

with Sodgwiek, A., cited................ 7S-80 .Slanton. T. W., Pn;f:i:.v.._.........._....... v-vi

N Sliny, J., cited................................ 20. 2»»

"New red sandstone," stratigraphic place... 65-66 Ht.oppani, A., dtoil................._...... 4:;

O ''Sudburian," term proposed...._....... 125--I27'

"Old red sandstone," stratigraphta plat*. "&"*,67-68 T

Oligocene, term proposed.................... 53-54 "Taconian series," use of teriii............ 101, ;u3

"Outaric," term proposed... ....... 81-82 "Taconic," term proposed................ J01-102

Ordovician, term proposed......... ...... 83-84 "Tennessean system." term proposed....... 74-75

urdcvician system, limits....... .......... 84 Tertiary, term proposed.__.__.......... 4i>

"Ozarkian system" proposed by E. 0. Tertiary flora, divisions.........__..._._ 54-5<i

Ulrich...--.-.-.-----.....-.. 89-91 Tertiary period, divisions.......-.-.--..... SO-51

liinits...........__ .. -......... 90-92 Thickness of the sedimentary rocks......... fi-7

1' Time, geologic, estimates in years........... 4-5

Page, D., cited....... ------__ __. 21 Time terms, correspondence with rock terms. 0-4

Paige, Sidney, cited..-.-.-- .----.. . 121 "Timiskamian series," term proposed....... 124

" Peleocene." term proposed and defined. 50,54-56 Tornebohm, A. E., and Hennig, A., cit.;d... 2o

Paleozoic era, limits and life of........ .... 13-14 Tornquist, A., cited.. .-._....... ..... 29

term introduced.................._.... 10 Trias, term proposed....._....... .. 64

Park, J., cited__....'.... ... .......... 29 Trinssicsystem, American facies ...... ... 04

Parks, W. A., with Coleman, A. I'., cited... 42 limits................................... W

Peale, A. C., cited... ._-__-_____ 108-111 U

Pennsylvanian series, limits........ 72-73 inrich, E- O., cited....... 74-7.1,S8,!j9^'jO,91-W

relatioas of fauna and flora..... . 6SKO w'tn Winchell, N. H., cited ..... 85-86

term proposed..... .... . 72 \T

Perniiun, relations of fauna and flora......... 69-70 Van nise- c- u- cited........ :«-:«, 33-36,111-112

term proposed ............... 68,70-72 an(l **?*> c- K- cited.......... 36-37, !19,131

Phillips, J., cited..... ... 3,11-13,30,42,43 v °6t, C., cited.......-... .. 24

Phillips, W., with Conybcare. \V. D., cited - 65-<i8 ... . . . .. . w

Pleistocene, term proposed and defined 47-49 JJafen> ^JU^a'^:,\"»:,-:""'T'n' '' 1 * . . \\adswcrth, M. K., with Whtney, J. D., Pliocene, term proposed............ ......- .T0-o3 '. ' ->, Powell, J. \V., cited ....... ... . 103,113 ... . ,. ., l'"cu ----- ------------------- -^

" Progonozoic" and "Progonic," terms pro- «"«>" ^ ^ ^^^^^^^^

Prot-rozoic proterozoic.Sp^pos^;-::::::::-::;;: era, diverse uses...... ..... 32-42 ^ ^althcr.J., u. ^^ *<^ > ^ ^ cited....... ............. J0,>

 Troweoic," term proposed.................. 42 Waucoban, term proposed..... ...... 10(1

 Protozoic era," diverse uses.. ......... 42-43 Waverly, term proposed..... 75-76

"Pro»o:c," term proi>osed___.......... . 43 "Waverlyan system." formations eonstitnt-

"Psyrhozoic era," term proposed............ 9 ing.......................... .. 7U-.S

Pu^oseof this bulletin...... .............. 1 Whitney, J. D., cited................ .... ''-1

Q and Wadsworth, M. E., cited........... 24

Qiiatt-rnary, term proposed-.-.... .......... 43-44 with Foster, J. W., cited............... 21

tjUiiicrnary perio<l, subdivisions ..... .. 45-46 Williams, 1.1. S., cited........ .-. .. 72,73-74

(Quotation marks, terms inclosed in........... g Winchell, A., died...... .._ - 28.7::

K Winchell, N. H.. and tflricb, E. O., citeJ .. «-> >

Kiidiouctivity, basis for estimate of geologic Worthen, A. H.. with Meek, F. B., cited... *5

time...... . . ... . 1-5 y,

Krboal, llenri, cited................ ......... 44-45 Zittd, K. A. von. cited ...... 17, 2».'24. 25.26.«2-»:4

O