Post on 29-Nov-2014
LIBRARYOF THE
UNIVERSITY OF CALIFORNIA.Class
GEOLOGY FOB ENGINEERS.
Demy
8vo.
Handsome
Cloth.
STRATIGRAPHICAL GEOLOGY AND PALEONTOLOGY,ON THE BASIS OF PHILLIPS. BY ROBERT ETHERIDGE, F.R.S.,of the Natural Hist. Department, British Museum, late Palaeontologist to the Geological Survey of Great Britain, Past President of the Geological Society, etc.
With Map, Numerous"If Prof.
Tables,
and Thirty-sixits
Plates.
originality and the breadth of its views, Mr ETHERIDGE fully justifies the assertion made in his preface that his book Must take HIGH RANK differs in construction and detail from any known manual.
SEKLEY'S volume was remarkable for
.
.
.
AMONG WORKS OP REFERENCE."
A thenceum.
SIXTH EDITION, Thoroughly Revised.
With
Illustrations.
Cloth.
AIDS IN
PRACTICAL GEOLOGY:WITH A SECTION ON PALEONTOLOGY. BY PROFESSOR GRENVILLE COLE, M.R.I. A., GENERAL CONTENTS.I
F.G.S.
Part III. Examination of Rocks. Part I. Sampling of Earth's Crust. Part IV.- Examination of Fossils. Part II. Examination of Minerals. "That the work deserves its title, that it is full of AIDS.' and in the highest degree PRACTICAL,' will be the verdict of all who use it." Nature.|
'
'
With 12
Full-page Illustrations from Photographs. SECOND EDITION, Revised.
Cloth.
OPEN-AIR STUDIES IN GEOLOGY:AN INTRODUCTION TO GEOLOGY OUT-OF-DOORS. BY GRENVILLE A. J. COLE, F.G.S., M.R I.A.,Professor of Geology in the Royal College of Science for Ireland, and Examiner in the University of London. "The FASCINATING 'OPEN-AiR STUDIES' of Prof. COLE give the subject a GLOW OF ANIMATION cannot fail to arouse keen interest in geology." Geological Magazine. "A CHARMING BOOK, beautifully illustrated." A thenceum.. ..
In Crown 8vo.
Handsome
Cloth.
Fully Illustrated.
A HANDBOOK ON
THEODOLITE SURVEYING AND LEVELLING.FOR THE USE OF STUDENTS IN LAND AND MINE SURVEYING. BY PROFESSOR JAMES PARK, F.G.S.
"A
book which should prove as usefulNature.
to the
professional surveyor
as
to
the
student."
SECOND EDITION,
Revised.
Crown
8vo.
Handsome
Cloth.
Illustrated.
MINING GEOLOGY.Professor of Mining and Director of the Otago University School of Mines late Director Thames School of Mines, and Geological Surveyor and Mining Geologist to the Government of New Zealand.;
A TEXT-BOOK FOR MINING STUDENTS AND MINERS. BY PROFESSOR JAMES PARK, F.G.S., M.Inst.M.M.,
"A work which should find a place Mining World.
in the library of every
mining engineer."
LONDON
:
CHARLES GRIFFIN &
Co., LIMITED,
EXETER
ST.,
STRAND.
GEOLOGY FOR ENGINEERS
BY
LIEUT. -CoL.
R. F.
SORSBIE,
R.E.
mattb nearly 100 ^figures.
LONDON:CHARLES GRIFFIN & COMPANY, LIMITED,PHILADELPHIA:J. B.
L1PPINCOTT COMPANY.
7
PREFACE.IN these days of specialising in " watertight compartments," the bearing of geology in relation to almost every branch of engineer-
A knowledge of very frequently neglected or ignored. of the first importance to the practical geology is, however,ingis
engineer, but
it is difficult
for
him
to study the application of this
science to his requirements without having recourse to a large
number
of different textbooks
and other works.
References to
geology which are often of the greatest practical importance are often almost hidden away or treated in an obscure fashion, whereas the engineer requires the needful information to be
him
in a clear
and concise manner.
To meet
this
want
put before I have
endeavoured to compile the requisite information in one volume,in theI
hope that
it
may
serve as a
handy book
of reference.
greatly indebted to the various authors and publishers of the books mentioned in the accompanying list for so kindly allowing me to take such extracts as I required, and desire to record
am
my
grateful thanks to Professors Lapworth, Cole,
and Bauerman,
and Mr Hayden of the Geological Survey help and encouragement.
of India, for their kind
These extracts are referred to by a number at the end of each quotation corresponding with the number in the accompanyinglist.
R.
F.
SORSBIE.
January 1911.
226185
AUTHORITIES CONSULTED.1
Author.
Geology in Systematic Notes and Tables, by Wintour F. Allmann & Sons, 67 New Oxford Gwinnell, F.G S. ; 2nd edition. Street, 1889. 3 An Intermediate Textbook of Geology, by Charles Lapworth, F.R.S. William Blackwood & Sons, 1899.
2
Geology: Chemical, Physical, and Stratigraphical, vol. i., Chemical and Physical, by Joseph Prestwich. Clarendon Press, 1 886. 5 Geology : A Manual for Students in Advanced Classes and for General Readers, by Charles Bird, B.A. Lond., F.G.S. Longmans,
4
Green6
&
Co., 1894.
Manual of
Geology,
Theoretical
and
Practical,
by John
LL.D., F.R.S., Part I. Physical Geology and PalceonCharles Griffin & Co., 1885. tology, by H. G. Seeley, F.R.S. 7 Physical Geology, by A. H. Green, M.A., F.G.S. Longmans,Phillips,
& Co., 1898. filoxam's Chemistry (a few definitions only). 9 Physical Geology, by Ralph Tate, Weale's series. Lockwood & Son, 1907.Green8
Crosby,
The Standard English Dictionary (a few definitions). Economic Geology, by David Page, LL.D., F.G.S. Blackwood & Sons, 1874.11
10
Wm.
12 Textbook of Systematic Mineralogy, F.G.S. Longmans, Green & Co., 1903.13
by Hilary Bauerman,
Elementary Course of Geology, Mineralogy, and Physical Geography, by D. T. Ansted. John Van Voorst, 1856. 14 Textbook of Descriptive Mineralogy, by Hilary Bauerman, F.G.S. Longmans, Green & Co., 1902. 15 Aids in Practical Geology, by Grenville A. S. Cole, M.R.I. A., F.G.S. Charles Griffin & Co., 4th edition, 1902. 16 The Study of Rocks, by Frank Rutley, F.G.S. Longmans, Green & Co., 6th edition, 1894.
Vlll
GEOLOGY FOR ENGINEERS.
Vol. ii. of Prestwich's Geology (see No. 4). Historical Geology, by Ralph Tate, Weale's series. Crosby, Lockwood & Sons. 19 How to Observe: Geology, by H. T. de la Beche, F.R.S., etc. Charles Knight, 1835. !0 A Guide to Analysis in Geological and Agricultural Chemistry,18
17
by an21
Officer of the
First Book of William Collins & Sons.22
A
Bengal Engineers.Mineralogy,
by
J.
H.
Collins,
F.G.S.
The Principles of Waterworks Engineering, by J. H. T. Tudsbery, D.Sc., and A. W. Brightmore, D.Sc.; 3rd edition. E. & F. N. Spon, 1905. 23 The Water Supply of Cities and Towns, by W. Humber.Crosby, Lockwood & Sons, 1876. 24 Sanitary Engineering, by Vernon
Harcourt.
Green
Co., 1907'. 25 Treatise on Waterworks,
&
Longmans,
&
by
S.
Hughes.J.
Crosby, Lockwood
Sons, 1875.26
Quarrying and Blasting Rocks, by SirCrosby, Lockwood
Burgoyne, Weale's
series.
&
Sons, 1895.
27 Treatise on Building and Ornamental Stones of Great Britain and Foreign Countries, by Edward Hall. Macmillan & Co., 1872. 28 Charles Road-making and Maintenance, by T. Aitken. Griffin & Co., 1900. 29 Appendix by R. Mallet in Dobson's Brick and Tile Making, Weale's series. Crosby, Lockwood & Sons. 30 Calcareous Cements, by G. R. Redgrave and Charles Spackman. Charles Griffin & Co., 1905. 31 Limes, Cements, Mortars, etc., by G. R. Burnell, Weale's
series.32
Lockwood & Sons. 33 Road-making andGriffin
Crosby, Lockwood & Sons. Pioneer Engineering, by E. Dobson, Weale's
series.
Crosby,
Maintenance,
by
T.
Aitken.
Charles
&
Co., 1900.
34 The Construction of Roads, Paths, and Sea Defences, by Frank Latham, C.E. The Sanitary Publishing Company, Ltd.,
"Elementary Essay on Road-making," Art of Constructing Roads, by H. Law, C.E., Weale's series. Crosby, Lockwood & Sons. 36 An article on "Broken Stone Roads," by Reginald Ryves in Engineering, 1905, pp. 76 and 205. 37 The Rudiments of Civil Engineering, by H. Law, C.E., Weale's series. Crosby, Lockwood & Sons, 1882.quoted in Rudiments ofthe
1903. 35 Professor Mahon's
AUTHORITIES CONSULTED.S8
IX
Hydraulic Tables, by Nathaniel Beardmore.
Waterlow
&
Sons, 1852. 39 The General Principles of Mineralogy, by J. H. Collins, Wm. Collins & Sons. F.G.S. 40 Tidal Rivers, by W. H. Wheeler, M.I.C.E. Longmans, Green & Co., 1893. 41 Coast Erosion and Foreshore Protection, by J. S. Owens, M.D., A.M.I.C.E., F.R.G.S., and G. 0. Case. St Bride's Press, 1908. 42 An article on "Coast Erosion and Reclamation," in The
Engineer of 27th April 1906, and subsequent numbers.In addition to the above works from which extracts have been taken the following authorities have been consulted:
Geikie's Textbook of Geology.
" Geology Processes and their Results," Encyclopaedia Britannica. Chambers^ Encyclopaedia. Stevenson's Principles of Canal and River Engineering. Etc.
Class-book of Geology. Field Geology. Lyell's Elements of Geology. Murchison's Siluria. Dana's Manual of Geology. Penning's Field Geology. Marker's Petrology for Students. Hatch's Textbook of Petrology.:
Chamberlin and Salisbury
:
.
CONTENTS.INTRODUCTIONmaking, adopted:
Practical
Earthwork
Uses Water-supply, Building, RoadBranches of Geology Arrangement1_2
PARTINTRODUCTORY REMARKS
I.
DYNAMICAL AND STRUCTURAL GEOLOGY,3
CHAPTER I. CHANGES ON THE EARTH'S SURFACE.AGENCIES
DENUDATIONSectionI.
EFFECTS
SUB-HEADS
....Weathering,
4
The Work
of the Atmosphere.
(i)
Air.
(ii)
Changes of Temperature JEolian Action Transportive Action and Constructive Effects Loess, Sand-drift, Sand-dunes Rain Chemical A ction. Destructive ActionOxidation, Deoxidation, Carbonation, Hydration tive Effects Soil and Subsoil
Destructive
Action
4.7
Construc-
7_8
(iii)
Rain
Mechanical Action. Destructive Action Transport of Particles Earth Pillars Disintegration Constructive Effects Talus, Screes, Rain-wash
....... .
8-9
Section II.Source(i)
Underground Water.9-10Destructive Effects
AmountProcesses
Chemical Action.
Subterranean10-11
Channels, Caverns, and Swallow-holes(ii)
Constructive Effects.
Stalactites, Stalagmites, Petrifying Springs
Mechanical
Action.
Destructivexi
Effects
Landslips.
Con.
structive Effects
11-12
Xll
GEOLOGY FOR ENGINEERS.
Section III.Source(i)
Running Water.
Mechanical Action
Chemical Action
........; .
Erosion.(1)
Methods of Excavation Rate of Erosion depends on Nature of channel, (2) Rock formation, (3) Climate De-
(ii)
Transportation.
(iii)
velopment of Valleys Chemical Transporting Power Materials Composition Alluvium Occurrence of Deposits: (a) Alluvial Deposition. fans or cones (b) Alluvial plains (c) River terraces (d) Marine deltas (e) Lake deltas (/) Bars
.........;
;
;
;
Section IV.(i)(ii)
Glacial Agencies.Protective Action
Frost
and Snow. Destructive Action Formation Glaciers and Ice-sheets.
Movement
of Glaciers
Work of Glaciers Erosion Transportation and Deposition, Moraines, Perched blocks, Roches moutonne'esSection V.Gradation(i)
Marine Action.Breakers
Oceanic Movements.
Wave
-
action
Erosion(ii)
Transportation
Deposition
Under-tow Ocean CurrentsPelagic Deposits
Oceanic Deposits.
Terrigenous Deposits
Globigerina Ooze
Red Clay
Section VI.(i)
Organic Action.Constructive Action Constructive Action
Vegetable.
Destructive ActionDestructive Action
(ii)
Animal.
CHAPTER
II.
CHANGES WITHIN THE EARTH.Heat Hot Springs Pressure Water Internal Forces. Volcanic Products Lava, Rock - fragments, Bombs, Volcanoes. Decline of Volcanic Volcanic Vents Tuff Lapilli, Ash,Activity Mud Volcanoes Mud Springs Variation in the Sea-level Elevation and SubCrust Movements. sidence of Land Causes of Secular Movements
....Effects:
Cause Effects Earthquakes. Pressure Changes in Rocks. Cause Heat, Water,:
Trans-
formation,
Plication,
Consolidation
.........Metamorphism,Foliation,
Cleavage
CONTENTS.
Xlll
CHAPTER III. STRUCTURAL CHARACTERS OF ROCKS.INTRODUCTORY REMARKSSectionDefinitionI.
PAQB33
Igneous Rocks.
Extrusive and Intrusive
Contemporaneous or Extrusive Rocks.Subsequent or Intrusive Rocks. Laccolites BossesJoints.
Nature Cause Hexagonal Structure of Ice, Haematite, and quartz Columnar Structure of Basalt
........Sills
Lava Fragments Necks Veins and Dykes
...
33-34 3435
36-37
Section II.Changes(i)
Aqueous Rocks.37
after Deposition
Stratification.
Forms of BeddingStrata
Interposed
Laminae, Strata, False-bedding Character of Strata Alternation of
Beds(ii)
37-39
Inclination of Rocks.Inliers
Dip and Strike TJnconformability OverlapPlication
Outcrop
Outliers
and40-42
(iii)
Curvature or Flexure.clinal,
or Folds
Anticlinal,
Syn.
Monoclinal, etc
Nature, Sandstone, Clay, Limestone Master Joints Faults Throw Hade Reversed Faults (v) Dislocation. Step and Trough Faults Shift Fault-line Dyke Vein . .(iv) Joints.
42-43 43-44
44-45
Section III.Nature of Alteration
Altered and Metamorphic Rocks
Causes
...........
45-464647
Hydro-metamorphism. Action Results Thermo- or Contact Metamorphism. Action Effects Dynamo- or Regional Metamorphism. Cleavage Joints Foliation Relation between Igneous, Aqueous, and Metamorphic Rocks
47-50
PARTINTRODUCTORY REMARKS
II.
ROCKS AND MINERALS.51
CHAPTER IV. THE STUDY OF MINERALS.SOIL, ROCK,
AND MINERALS
52
XIV
GEOLOGY FOR ENGINEERS.SectionI.
Mineral Chemistry.CompoundEarthRadicle
PAQK
Definitions.
ElementSalt
Compound
AcidMetall oid
Base
Oxide
Terminations
Metal
Monad, Dyad, Triad, Tetrad, Organic Radicles Anhydride Elements Compounds Water Constituents of Earth. BeChemical Characters. Taste Odour Solubility in AcidsQuantivalence. .
.
.
.
52-54 54-5657
haviour (B.B.)
Section II.
Mineral Forms.Crystalline.
Mode of
Occurrence.
Amorphous
phous States Colloidal The Crystal Crystal Forms.SystemsModified Forms
Vitreous
.....Massive
Amor57-58
Crystallography
Axes
Crystal
Irregular Grouping of Crystals
Pseudomorphism
58-62
Cleavage. Structure.
Section III. Physical Characters. Laws of Cleavage Quality of Cleavage Columnar Lamellar Granular Imitative Shapes.. .
.
62-63
GlobularAcicularFracture.
ReniformStalactitic
Botryoidal
Mammillary
Filiform
DrusyConchoidal, Even, UnevenFriable
63-65
Form
of Surface
SurfaceTenacity.
Smooth, Splintery, Hackly, Earthy
....
Nature of65
Frangibility, Tough, Brittle, Soft,
Hardness.Touch.
Ductility Malleability Scale
Sectility . Rigidity, Flexible, Elastic
65-6666
Soapy
MeagreColour
Harsh
.
Specific Gravity.
Translucency
Definitions, Density, Specific gravity Kinds Intensity Streak Lustre.
.....
66 66 66-68
CHAPTER V. ROCK-FORMING MINERALS.Classification.
Native Elements
Sulphides
Fluorides
ChloridesSilicates
Anhydrous Oxides Hydrous SilicatesTitanateAbbreviations.
Hydrous OxidesCarbonates
Anhydrous
Sulphates
Phosphates69
HydrocarbonsApatite
Testing Minerals Andalusite Anhydrite List of Minerals.
69-70AragoniteCalcite
AsphaltCelestine
Epidote Felspars Garnet Glauconite Graphite GypGalena Fluor-spar Leucite Kaolin Iron Compounds sum Magnesite Manganese Compounds Micas and Talcs Nepheline Olivine Rock Salt Silica Series Sphene Sulphur TourmalineZeolites
Augite Hornblende group Copper Pyrites Dolomite
Barytes
Zinc-blende
70-93
CONTENTS.
XV
CHAPTER
VI.
THE STUDY OF ROCKS.DEFINITIONCLASSIFICATIONPAGE 94
SectionIgneous Rocks. Aqueous Rocks.AlteredPlutonic
I.
Mode
of Origin.
Volcanic
Hypabyssal
Arenaceous
and Metamorphic
Argillaceous Calcareous Hocks. Igneous Rocks Arenaceous.
.... ...
94-959595
Argillaceous
Calcareous
SectionGeneral Terms Igneous
II.
Chemical and Mineralogical Composition.96
Rocks.
Groups
Acid
Intermediate
Basic.
Ultra-basic
Chemical Constituents
Mineral Constituents
Aqueous Rocks. Arenaceous Argillaceous Calcareous Altered and Metamorphic Rocks. Principal Changes
... ....
.
96-9797
98
Section III.General Terms Igneous Rocks.Granitic
Structure.
98
Porphyritic
Felsitic
Matter
Columnar1.
Spheroidal
Drusy
Banded:
Structure.
Group
Dis-
tinctly Holocrystalline Rocks Pegmatitic or Graphic Gneissic Ophitic Orbicular. Group 2. Lithoidal
Fluidal
Rocks
1
:
Horny. Group 3. Glassy Rocks Perlitic Spherulitic Lithophyse Fluidal Pumiceous and Scoriaceous Amygdaloidal. Group 98-101 4. Volcanic Fragmental Rocks Agglomerate Brecciatad Aqueous Rocks. Group 5. Coarsely Fragmental Rocks Brecciated Stratified Rocks Conglomerate. Group 6. Ordinary Oolitic Pisolitic Laminated Pebbly Concretionary 101-102 Psammitic Altered and Metamorphic Rocks. Group 7. Rocks retaining tracesHemicrystallineMicrocrystalline:
Scoriaceous
:
.
:
:
Fluidal structure. Bedding Crystallisation Cleavage Foliation EyeGroup 8. Foliated or Schistose Rocks structure Granulitic. Mylonitic Group 9. Amorphous 102-103 Rocksof: :
Section IV.HardnessFracture
Physical Characters.StreakFeel
Colour and Lustre
and Smell
.
104-105
XVI
GEOLOGY FOR ENGINEERS.
CHAPTEREOCKS.INTRODUCTORY REMARKSSectionPlutonic Rocks.I,
VII.
PAGE 106
Igneous Rocks.PorphyryGranite Porphyry..
Granites
Syenites
Gabbro 106-109 109-111 Trachyte Andesites Basalt Rocks Volcanic Sands Volcanic Agglomerates Volcanic Fragmental Rocks. or Coarse Tuffs Tuffs and Ashes 111-112Quartz- Porphyry Volcanic Rocks. RhyoliteFelspar- PorphyryDiorite
Section
II.
Aqueous Eocks.
Fragmental or Clastic Rocks. (i) Arenaceous: Sand Sandstone Grit Conglomerate Greywacke Arkose BlueQuartzite Shale Mudstone Marl stone, 112-116 (ii) Argillaceous: Clay Rocks formed by Chemical or Organic Agencies. (i) Calcareous Limestone Dolomite Rock-Salt Gypsum, (ii) Siliceous Flint and Chert, Phosphatite Bone-beds (iii) Phosphatic Humus Peat Guano, (iv) Carbonaceous Coprolitic 116-122 (v) Ferruginous: Ironstones Lignite Coal,.
:
:
:
:
.
.
.
Section III.Classification
Altered and Metamorphic Eocks.122
Quartzite Lydian-stone Spotted Shale Purcellanite Slate 123-124 Serpentine. Crystalline Limestone Gneiss Mica Schist Classification Distinctly Foliated Rocks.
Altered Rocks.
.
.
Chlorite Schist
Talc Schist
Hornblende Schist
Calc Schist.
Mylonite
Granulite
Flaser gneiss
Augen
gneiss
,
124-128
Section IV.Igneous RocksSilicates
Eock Decomposition.
Felspars
Origin of Clays Decomposition of other Origin of Quartzose Sands and Sandstones Extent
Sedimentaryrocks
of Disintegration Strata. Alteration
128-132of.
Argillaceous
Freestones Colour Green Deoxidisation Bleached gravels 132-134.
CONTENTS.
XV11
PAKTINTRODUCTION
III.PAGE135
HISTORICAL GEOLOGY.
CHAPTER VIII. PRINCIPLES OF STRATIGRAPHY AND PALAEONTOLOGY.SectionFormations-TableI.
I.
Classification of Stratified Rocks.136-138 138-143 144-147 148-149150 151 152
Periods and Systems Sedimentary Strata in Great BritainClassified List of the Chief
.
.
.
.
Table
II.
AmericaTable III. Table IV.
........... .
Groups of Strata in North
List of the Formations in IndiaList of the
Sedimentary and Metamorphic Strata of.
AustraliaList of the Sedimentary Strata of New Zealand Table V. List of the Sedimentary Strata of South Africa Table VI.
.
SectionDefinitionsClassification of
II.
Palaeontology.
152-153 Spongida Coslenterata Echinodermata Annulosa or Vermes Arthropoda or Articulata Molluscoida 153-160 Mollusca Fishes Amphibia Reptilia Birds Mammals. 160-162 Vertebrata. 162 Classification of Plants 162 Phanerogams. Angiosperms GymnospermsInvertebrata.
Animals
......Thallophyta..
Protozoa
.
Cryptogams.
Pteridophyta
Bryophyta
.
162
CHAPTER IX. THE GEOLOGICAL SYSTEMS.CLASSIFICATION OF STRATA163
SectionIntroduction
I.
Anthropozoic or Quaternary Period.163
Recent or Post-glacial Formations.depositsPleistocene or Glacial Formations.
Human
Relics
Non-glacial
163-165Glacial Deposits
Continental EuropeAustralasia
North America
Great Britain Asia Africa
165-168II.
SectionIntroduction
Cainozoic or Tertiary Period.GreatBritain
Fossils
Continental
North America
Asia
Australasia
...
Europe.
168-171
XV111
GEOLOGY FOR ENGINEERS.Section III.
171 Great Britain Continental Europe North America South America Asia Africa Australasia 172-174 Great Britain Continental Europe Fossils Jurassic System. North America South America Asia Africa Australasia 174-175 Fossils Great Britain Triassic System. Continental TypesCretaceous SystemFossils.
Introduction
...........Mesozoic or Secondary Period.World-wide Distribution
PAGE
.
Europe
175-177
Section IV.Introduction
Palaeozoic Period177
Dyas
or
Great Britain Fossils Permian System. Continental Asia Africa Europe North America South America
Australasia
177-179Fossils
Continental Europe North America Asia Africa Australia 179-181 Fossils Great Britain Continental Europe Devonian SystemCarboniferous System.
Great Britain
.....
North AmericaSilurian System (Upper).Fossils
181-182Great BritainAustraliaFossils
Europe
North America
Asia
.....
Continental
182-184 184-185
Ordovician System (Lower Silurian).
Great Britain
Con-
North America Asia Australasia tinental Europe Cambrian System. Fossils Great Britain Continental Europe Asia North America Australasia
185-186
Section V.Britain
Eozoic Period.IntroductionFossils
Archaean and Pre-Cambrian Rocks.
Continental Europe Asia America Africa Australasia .
North America.
Great South.
186-188
PARTINTRODUCTORY REMARKS
IV.
GEOLOGICAL OBSERVATION.189
CHAPTERHammer
X.
OUTDOOR WORK.Equipment.Chisel
Bag and BeltAbney's Level
Walking-stickNote.
Compass book
Tape-measure
Pocket-leiis
190-191
CONTENTS.
XIX
SectionPreliminary Remarks
.........I.
Geological Surveying.
PAGE
Maps.
Contours
Tracing Boundary Lines..
191-192 192-194
Geological Sections
.
.
.
.
.
.
,
.
Section II.
Introductory Remarks Strata and their Inclination.Strike
.........Tracing Faults.
Structural Characters of Rocks.
195
Measurement
Dip and Principle of Stratification Curvatureof Thickness of Strata195-199. .
Overlap Unconformity Dislocation. Presence of a Fault
.199-200
Section III.Selection of Specimens.
Determination of Rocks.. . .
Rock-specimens. Structure Hardness Feeling SmellEffervescence Colour and Lustre Table VII. Easily Distinguishable Characters of RocksEasily distinguishable Characters..
Position
200
StreakFracture 200-202..
203-206
CHAPTER
XI.
INDOOR WORK.SectionI.
Further Examination of Rocks.
Hardness Specific Gravity Physical Characters. Detection of Carbonates Chemical Examination.Material
....
207-209
Summary
Preparation of of determinative Chemical Analysis of a
Rock
Fusibility
209-212
Section II.Mechanical Analysis.
Isolation of Constituents.
Crushing
Densetions
Liquids
Washing Magnetic Separation Use of Acids Determination of Propor213-218
Section III.
Determination of Minerals..
Mode
of Occurrence
Extraction
218
External
Form.
Preliminary
Examination
MeasuringHardnessSolubility
Crystal
AnglesPhysical Characters.
218-219Determina-
Determining Cleavage tion of Specific Gravity Fracture Chemical Characters. Taste and OdourSolvents
219-224Actionof.
224-226
XX
GEOLOGY FOR ENGINEERS.Section IV.
Blowpipe Examination..
PAGE
Apparatus and Reagents. Apparatus Reagents Use of Blowpipe 226-229 Blowpipe Operations. Assay Observation of Flame -col oration Observation of Fusibility First Operation (Closed Tube) Second Operation (Open Tube) Third Operation (Reactions on Charcoal) Fourth Operation (Cobalt) Fifth Operation (with Soda) Sixth Operation (Borax Bead) Seventh Operation (Microcosmic Salt) Eighth Operation Test for Sulphur 229-236 Table VIII. Colours of Beads 233-234.
PARTINTRODUCTORY REMARKS.
V.
PRACTICAL GEOLOGY.237
CHAPTERSectionRainfall. FallI.
XII.
WATER-SUPPLY.RainQuantity of Rain
Rainfall and Evaporation. Estimation of Mean AnnualFall
Maximum and Minimumand Absorption.
238-241
Evaporation
Effect
on
Evaporation from Surfaces of Water
Water-Supply Loss Dry Weather Flow
.
241-243
Section II.UndergroundWater.
Underground and Surface Waters.Water-slopeSaturation and
Imbibition.
Capacity of Rocks for Waterof Water
Surface
Waters.
Porosity of Rocks Surface of Saturation
Water-bearing Strata Yield Bournes Quality of Water 243-251Conditionsof
Flow251-253
Forests
Section III.
Springs and Wells.
Springs. Ordinary Springs Intermittent Springs Line of SaturaFault Springs Artesian Springs Springs as a Source tionof Supply
253-260Causes of Success or FailureQuality of Water.. .
Wells.
Shallow Wells Deep Wells Wells as a Source of Supply
260-262
Section IV.
Rivers.Strata
Flow of Water Quality of Water dependent on Schemes Flow of Streams and RiversTable IX.
River
Summer
Discharge of Rivers
263-266 266
CONTENTS.Section V.
XXI
Lakes and Impounding Reservoirs.Area
PA GE
Comparative Advantages Drainage Areas. Source of Supply Size of Catchment Available Rainfall Tendula ProjectLakes.
267
AdvantagesReservoirs. Sites
267-270 270. .
Impounding
Geological Features
.
271
CHAPTERINTRODUCTIONSectionGranitesI.
XIII.
BUILDING-STONES.272-273
Granites and Granitoid Rocks.Constituentsof
and
Syenites.
GranitesBritish
Qualities
Geological
Age
of Granite
Syenite
Granites and
Syenites
European GranitesGneiss
European SyenitesSerpentine
Table X.
Analyses Granitoid Hocks.Schists
273-279
PorphyryBasalt
Crystalline
Trap Hocks.
Greenstone
Lavas
Table XI. Analyses
.
279-281 281-287
Section II.
Sandstones, Limestones, and Argillaceous Rocks.. ..
Sandstones.
287-289 Weathering Properties of Sandstones and Limestones Old Lithological Character Cambrian and Silurian Red Sandstone Carboniferous Permian Triassic Jurassic Cretaceous Tertiary Table XII. Analyses of Sandstones 289-293.
Limestones.
Lithological Character
Marbles
ArchaeanJurassic
Silurian
DevonianTertiary
Carboniferous
Permian
Cretaceous
293-299Shales, and Clays). Silurian Devonian
Argillaceous Hocks (Slates, Characters CambrianSelection of Quarry
Lithological
Carboniferous...
Table XIII. Analyses
299-304
CHAPTERKaolin and FelspathicBritish ClaysFire-clays,
XIV.
BRICKS AND CLAYS.Clays.
Mud Loam,Qualities
Colouringetc.
Fire-bricks,
Floating BricksScience of Brick -making.
Fire-clays Terra-cottas
Shales, Marls, etc. Brick and Tile Clays 305-309 Dinas Bricks Firestones.
309-311
NormalColours
Choice of Clay Clays Foreign Bodies Constituents Laws of Induration Contraction
Table XIV. Analyses
.
.
.
.
.
.
311-317
XX11
GEOLOGY FOR ENGINEERS.
CHAPTERLIMES, CEMENTS,
XV.
AND PLASTERS.PAGE. .
DEFINITION OF CEMENTS AND LIMES INTERMEDIATE LIMES 318-319 Combination of Lime with Water Quicklime Slaked Lime Limes. Lime slowly recombines with Carbonic Acid Classification of Limes 319-321 The Influence of Clayey Matters Artificial Hydraulic Limes. Admixture of Clayey Matters Pozzuolana, Trass, etc. Influence of Heat on the Silicates 321-322
...........
Limestones.
Subdivisions
Chemical Nature of Stones furnishing.
different Sorts of
Calcination.
Lime Kilns and Fuel
.
322-323Results of
Admixture with AshesBerthier's
CalcinationTesting Limes
323-324
and Limestones.
Mode
of Analysis.
The.
Treatment with Muriatic Acid Influence of Calcination Roman Cement Energy Portland, Selenitic, and Magnesium Cements of America Sesvage Sludge Cements Plasters. Plaster of Paris Keene's and Parian Cements General Laws Probable Position of Different Geological Distribution. Materials Lias Lime British Limestones . .Condition of the SilicaCements...
325-326
326-328 328-329329-332
.
.
CHAPTER
XVI.
ROADS AND CANALS.SectionI.
Road-making.KnowledgeDetermination
Selection of Route. Value of Geological of Route Laying out Roads
New
333-334
Road
Construction.
Road-cuttings
Side-slopes
Methods of Drain334-338
ageSubsoil DrainageMountain Roads.DescentCrossing Watersheds.. .
Mountain Passes. .
.
....
Line of.
338-341
Section II.
Road
Materials.
. . Classes of Roads Water Influence of Weather. " Materials for Wearing" Roads. Local Circumstances
.341-343343-344 345-346 346-347 347-348
Suitable
Road MetalLimestone Gravel Materials for Weather-resisting Roads. Binding Material. Choice On Main Roads On By-roads. . .
.
Paving Materials.
Asphalt
Selection of Materials. Durability of
Tar-macadam Requisites in a Road Stone Physical Tests Road Stones Coefficients of Quality 348-351. .
CONTENTS.Section III.Level Surface General
xxiii
Canal-making.Leakage-
PAQE
Natural Feeder
Strata passed through
Remedy
351-353
CHAPTER
XVII.
RIVERS.Motion of Water in Rivers. Motion of Water Retarding Force Velocity Contour Rotary Motion of Particles Dynamic Action 354-358 The Transporting Power of Water. Transport of Material Erosion Quantity of Material Motion of Particles of Matter in Suspension Effect of Alteration in Dimensions of Channel 358-362 Proportion of Deposit carried Material transported The Physical Condition of Tidal Rivers. Origin and Description of Rivers Agents of Maintenance Regime of Rivers Junction of Rivers with the Sea Source of Detritus in Rivers Effect of obstructing the Free Flow of the Tide 362-365 Bars at the Mouth of Rivers. Description Bars composed of Hard Material not affected by the Scour of the Current Bars due to the Deposit of Alluvial Matter Bars at the Mouths of Sandy Estuaries Formation of Sandbars Channels where Bars are absent Theories as to the Cause of Bars 365-368 River Improvement Schemes. 368 Geological Formation of River Bed Land Reclamation. Embanking and Warping 368-369..
......
.
....
.
CHAPTERINTRODUCTORY REMARKSSectionOutlineI.
XVIII.
COAST EROSION.370
Coast-lines
and their
Origin.Inlets
Influence of Altitude
Minor Features
Headlands
The ShoreSectionWaves.FreeII.
Sea-cliffs
370-373
Forces acting on Coast and Sea-bed.Wavesof Translation
Waves
Forced Waves
Close
Overtaking of One Wave by Another Direction of Waves Oblique Waves 373-378 Tidal Action. Slow Rise and Fall Tidal Currents . . 379-380 Joint Action of Waves and Currents. Movement of Material 380 . Wind-formed Currents. Effect of Wind Undercurrents Alongshore Currents . 380-381.
to the Breaker Line
Breakers
Percolation
.
.
.
XXIV
GEOLOGY FOR ENGINEERS.Section III.
Coast Erosion and Eeclamation.
PAQE
Subsidence and Upheaval of the Physical Causes of Denudation. Earth's Crust Physical Causes of Sea Encroachment RiverDetritusProtective Works.
Effect of Deposits
of Littoral Drift to
on the Deep-sea Bed Relation 381-384 Eroded Material Deep-sea Erosion.
.
Impossibility of Entire Prevention of Erosion Effect of Protective Works on Adjoining Coast-line National Aid in Coast Protection Effect of Pier Works and other
Artificial Projections Littoral Drift. Effects of Coast Contour Effects of Tide and Wind
384-387
and River Estuaries
Sea Watts and Groynes.
Se* Walls
Groynes
....
387-388 388-390
CHAPTER
XIX.
USES OF MINERALS.Distribution of Valuable Minerals and Rocks. Coal Silver Platinum Mercury Tin Copper
....Iron
Gold
391-393393-394
Other Useful Minerals.
Barytes
Anhydrite
Gypsum
Asbestos
Mica Mineral Pigments.Ultramarine
Reddle Umber Metallic Pigments Table
Ochre
Bole
....Whiting.
394-396
INDEX
397-423
LIST OF ILLUSTRATIONS.PIG.1.
PAGEMillstone grit, Yorkshire6
6
2.3.
Rocks passing up into
soil 1919.
8
4. 5.6.
Section of ossiferous cavern with stalactites and stalagmites Fan at Tigar in Nubra at Ladakh 6
11
16
The Mer de Glace 6 Diagram of crag andVolcanic dykes19
tail
419
.192119
18
7.8. 9.
Action of the sea on the rocks of the coast
Columnar structure9
of basalt
.......6
353737
10. Jointed structure of granite11. False-bedding12.
19
38
Lenticular, interposed, and divided beds 6 13. Exchange or alternation of beds14. Section of outlier15. 16. 17.18.6.-
.3940 40 40
39
.
Map
of outlier6
6
Mapofinlier
....
Section of inlier
6
40
Unconformity of stratification 19. Diagram of overlap 620. Anticlinal dip66
.........6
4141
42 429
21. Synclinal dip 22. Breadth and throw of a fault23.
4444
Dislocation of strata6
6
24. Dislocation of vein 25.26.
45456. .
Reversed fault
6
27.28. 29.
Showing that cleavage does not pass through a bed of sandstone 6 Parallel cleavage in contorted strata of North Devon.
48 48
.
Ideal section
6.
Cubic system 13 30. Tetragonal system31.
.
.
.
39
50 59 60606161
Rhombic systemOblique system
13
32. 33.
*>
1313
Doubly oblique system
........
XXVIF *G 34.-
GEOLOGY FOR ENGINEERS.13
Hexagonal system
...........
PAGE61
35. Imitative shapes 36. Nummulites 6
64 153
37.
Monograptus (MurcMson)17
154 154
38. Diplograptus 17 39. Didymograptus 40. Rastrites (Lyell) 41. Lithostrotion 3 42. Calceola3
154. ..
.154154 154155
43.44.
Madrepora
3.
Favosites ( Murchison)
.
.
.
.
.
.
.
.155155 155
45. Heliolites
46. Syringopora 47. Pentacrinus48.
(Dana) (Dana)63.
155. ..
Encrinus
liliiformis
.'
.
.
.
49. Cypris 15 50. Estheria
.,
.
.
.
.155 .156156
3 17
51. Eurypterus 3 52. Olenellus
...''.
.
..'..'."
.
53. Paradoxides (Murchison) 15 54. Fenestella 55. Spirifer 56. Rhynchonella57.15"
.
.156 .157 .157.
15. .
.
Productus3
15.
.
58. Terebratula
6.
..........'
^.'
.
..
.
,.
.
.
.
157 157 158158 158
'
.
.
.
.
.
.
.158
59. 60.61.
62.
63.
Gryphsea 3 . Cyrena 3 Hippurites Gasteropods (a) Bellerophon 3 (d) Paludina Nautilus 6
....
.
.
.
^
.
.
.158158;
:
;
(b)
Limnaea
;
(c)
Planorbis (Lyell)
64. Goniatites (Lyell)65.
.
.
.
.
v
. .
'...,..159..
159 159
.
..
Ceratites
3..
.
.
.
.
,
.159159.
66.
Ammonites3
6
67. Turrilites68. Scaphites
3 3.
69. Orthoceras
70. Belemnites71. 72.
15
....ls 9
.
v
.
.,.
...".. ... .....
'
.
.
159 159
.
.
.
160160
.
.
.160\197 198
Hamites (Geikie) Measurement of dip
73. Calculating thickness of strata 74. Thoulet's 75. 76. 77.78.
washing apparatus
15
.
........214,..
.
.
.
Hollow collecting water ^ Spring arising from water falling on outcrop
Spring at outcrop of permeable stratum
w
23
Syphon
action
23
254 254 254 255
LIST OP ILLUSTRATIONS.FIG.
XXV11
79.
at outcrop of permeable between * 80. Inclined line of saturation
Water
81. Inclined line of saturation82. Origin of
two kinds of springs
83. Spring in valley caused84.85.
86.
by fault ^ Spring on hill caused by fault thrown out by a dyke w Spring Water held down in porous bed by superimposed imperviousstratum 23 Natural fissure givingrise to artesian
87.88.
Surface of saturation near a river
89. 90.
Road-cuttings in mountain pass
Road-cutting in mountain pass 91. Oscillation of particles of water92.
Action of oblique waves 41 41 . 93. Erosion by parallel waves 94. Joint action of waves and currents
....... ....... ..... ...... ....... ....... .......... ...... ...... ....... ........ ...... ......two impermeable beds.
*
256 256257
25
*
.
.
25
257 258 258
259 259
^.
spring
w
32
259 263 340341
^41
.
.
.
.
.
.
41
374 378 379 380
GEOLOGY FOR ENGINEERS.INTRODUCTION.the science which investigates the history of the nature and formation of the rocks which form the solid framework of the globe ; of the agents which produce changes in these rocks ; and of the history of the past 2 life, whose remains (fossils) are buried in them. Practical Uses. The advantages to engineers of a knowledgeis
GEOLOGY
earth.
It treats of the
and
be palpable to all who study their profession, employed abroad, who often must win from Nature the materials with which they may eventually defy her destructive efforts. The following are some of the practicalof this science will
especially to those
l uses of a knowledge of geology It explains the natural drainage of a district, etc. Water-supply, both surface and subterranean ; and it shows where artesian wells are possible, as also where fissures and faults exist. It affords indispensable information as to (1) the Building. composition of various rocks fit for particular uses, e.g. for:
building -stone, for bricks, for mortar and cement, for tiles and the way in which the rock has been affected by the weather, where exposed in cliffs and quarries, affords a valuable guide as to its durability ; (2) the areas covered by rocks yielding these materials, and their relative position among other strata, and how best worked. Road-making. It is of great importance in guiding the engineer (1) as to the choice of a line of road, so as to ensure its proper drainage, and prevent slipping: this will depend on the nature and succession of the strata and their dip ; (2) as to roadmetal what rocks are obtainable, what rocks are preferable, and what rocks are unsuitable. Earthwork. To the engineer making tunnels, cuttings, andslates: :
1
,
^ -3
HJg g0} of a comb. heterocercal (with unequal lobes), or homocercal (with symmetrical3
lobes).
The vertebral column is straight throughout, and its terminal portion is symmetrically surrounded by the caudal fin. In the others this terminal portion is bent obliquely upwards, and the lower part of the caudal fin is, 3 developed into a distinct lobe, so that the tail becomes bilobed in form.-
*
SECT.
II.]
PRINCIPLES OP STRATIGRAPHY AND PALAEONTOLOGY.
161
Groups of Fishes. (1) Teleostei (perfect-boned), with the whole of the internal skeleton osseous and the tail homocercal ; e.g. most
modern(2)
fishes.;
Ganoidei
ganoid
and heterocercal
tails, e.g.
scales, osseous or cartilaginous skeleton, Palgeozoic fishes.
(3) Elasmobranchii (plate-gilled) include sharks and rays, skin unprotected or with scattered, isolated scales, cartilaginous skeleton ; e.g. Hybodus, Acrodus. (4) Dipnoi (double breathers) include mud-fishes ; e.g. Ceratodus. (5) Marsipobranchii (pouch-gilled) include the Ostracodermi or
shell-skinned, Cephalaspis
and Pteraspis.
These have the character of fishes in the young or Besides the tadpole stage, and of reptiles in their adult state. Batrachians, frog, toad, etc., and the recent tailed forms, newt, etc., there were Labyrinthodonts, bone-clad forms with peculiar teeth, and often of colossal size, Mastodonsaurus, found only in 2 Carboniferous, Permian, and Triassic rocks. can be distinguished from Amphibians by the articulaReptilia
Amphibia.
tion of the skull to the vertebrse, the complexity of the lower jaw, and by the teeth having one fang. 5 Of the ten orders known only four still live:
and turtles, dating from Jurassic times. Snakes and serpents, unknown before Tertiary times. (3) Lizards, including the Permian Proterosaurus (the earliest known reptile), the Triassic Telerpeton, and the gigantic Cretaceous Mosasaurus.(1) Tortoises(2)
(4) Crocodiles, including the Stagonolepis of the Trias, Teleosaurus of the Oolite, and Goniopholis of the Cretaceous.
The
(5) Ichthyosauria,
chief extinct orders, all Mesozoic only, are from the Trias to Chalk.
:
(6) Plesiosauria, Trias to Chalk. (7) Ornithosauria or Pterosauria, flying reptiles, Pterodactylus,etc.,
from the Lias to Chalk.;
Dinosauria, huge reptiles Atlantosaurus (100 feet long). 2(8)
Iguanodon,
Megalosaurus,
The earliest known form is Archceopteryx of the Upper with a long bony tail, toothed and very like a reptile. Bird fossils are never abundant, but are fairly common in Tertiary strata. 2 Mammals. (1) Marsupials; having pouches for carrying the young. (2) Cetaceans ; whales, porpoises, dolphins.Birds.Oolites,
(3) Sirenians (4)
; manatee, etc. Edentates (toothless) ; armadillo, Glyptodon, Megatherium.;
(5) Insectivores(6) Bats.
mole, Stereognathus.
u
162(7)
GEOLOGY FOR ENGINEERS.Rodents;
[PT.
III.
CH.
VIII.
beaver, hare, mouse, etc.tapir, Palceo-
(8) Ungulates, including horse, pig, rhinoceros, therium ; also the Ruminants, ox, elk, deer, etc. ;
and Probosci-
deans, elephant, Mastodon, Dinotherium. (9) Carnivores ; lion, cat, dog, bear, hyaena.(10) Primates ; monkeys, apes, and man. Plants have been arranged by Classification of Plants. botanists into two main divisions or sub-kingdoms namely, the Phanerogams or flowering plants; and the Cryptogams or non32
flowering plants.order.
The
following arrangement
is
in
descending
PHANEROGAMS.Angiosperms. True flowering plants, often bearing bright bells or brilliant clusters of bloom, and always having their seeds enclosed in some more or less conspicuous form of enveloping fruit.Plants with two cotyledons or seedDicotylce or Dicotyledons. also called Exogens from their mode of growth outwards lobes forming annual rings of growth, as in all our shrubs and forest trees.in Tertiary strata. Plants with one seed-lobe, inMonocotyledons or Endogens. Ex., grasses, palms, lilies, creasing by additions in the interior. arums. They date from Carboniferous age. Gymnosperms. Plants with naked seeds, i.e. not contained in a seed-vessel; mode of growth exogenous, like that of the dicotyledons. Cycads, palm-like plants with hard leaves, easily preserved. They date from Permian times. Firs, pines, yews, etc., with resinous wood (the fibres Conifers.of
They date from Upper Cretaceous and abound
which have peculiar markings) and usually cone-shaped These date from Devonian.CRYPTOGAMS.
fruits.
Pteridophyta or Fern-plants. Lycopods or Club-mosses, the most abundant of Carboniferous plants. Equisetites or Horse-tails,with pointed stems.
abundant and
Ex., Calamites, Equisetum. Ferns, often of tree-like size, from Devonian or Silurian times.1
Ex., Cyclopteris, Neuropteris, etc. Bryophyta or Moss-plants.
Mosses
form
beds
of
peat
;
Sphagnum, the bog-moss Thallophyta. FungiAlgce
;
Liverworts. 1
Mushrooms,
lichens, etc.
rare as fossils.
Sea-weeds, etc., occur fossil from Cambrian period. Some, which secrete mineral matter, form rock-deposits, e.g. Corallines and Nullipores, with calcareous incrustation ; Diatoms, with beautiful siliceous cases, and Chara, with encrusted stems and fruits, 1
SECT.
I.]
CHAPTER
IX.
THE GEOLOGICAL SYSTEMS.Classification of Strata.If classed as to their place
and mode
of formation strata are terrestrial, lacustrine, fluviatile, or marine. Terrestrial deposits on old land surfaces are marked by tree-
stumps
in position as they grew, with tree-stems, leaves, fruits, land-shells, insects, etc., in the old soil round their roots. Lacustrine deposits in old lake beds and Fluviatile deposits in old
river beds are(a)
marked by
:
of shell-marl or limestone, full of fresh-water shells. shells or insects, leaves, fruits, etc. (b) Clay containing these Iron-stained sand, gravel, and conglomerate with fresh(c)fishes, etc.2
Beds
water and land plants,sea-shells,
Marine deposits on old sea bottoms are marked by sea-weeds,echinoderms, corals, foraminifera,I.
etc.
Section
Anthropozoic or Quaternary Period.all
that time which elapsed between the and the present day. There is no break either stratigraphical or palseontological between the Tertiary and the Quaternary, but the latter is signalised by the It is not possible to commencement of the Glacial epoch. arrange the Quaternary accumulations in strict chronological order, because their relative antiquity is so often indeterminable. In the glaciated regions of the northern hemisphere the various Glacial deposits are grouped as the older division under the name of Pleistocene, and the younger accumulations which lie above them are named Recent or Post-Glacial. 8
This period includes
close of the Tertiary period
RECENT OR POST-GLACIAL FORMATIONS.
Human Relics. In most of the non-glacial deposits we find evidence of the existence of man, in the form of implements of stone, bone, etc., and the study of this special branch of geology163
164
GEOLOGY FOR ENGINEERS.
[PT.
III.
CH. IX.
shades insensibly into the science of archaeology. 1 The following is the chronological classification of the deposits yielding traces of
human workmanship whichlogistsTT:.
is
generally employed by archaeoof
('
(
(
Prehistoric
3 Pecopteris, Glossopteris, Cycads and Conifers. Great Britain. There are two sections the Lias and the the former consisting typically of dark shales alternating Oolite with thin beds of blue or grey limestone, and the latter of alternations of massive calcareous rocks with thick sheets of softpods, Terebratula(fig.
58),
3 grey clays and marls.
The Liassic strata stretch across England in a narrow strip, varying from 1 to 20 miles wide, from Lyme Regis to Whitby and the mouth of the Tees. The Oolitic strata form a wider tract directly to the east of the Lias. 5 The Lias is marine throughout, but affords beds of iron-ore in Yorkshire (Cleveland) ; the Lower Oolites are marine and estuarine towards the north ; while the Middle Oolites are invariably The Upper Oolite is best developed at Swanage and marine. Portland, and shows fresh-water beds in its upper zones (Purbeck). Outliers of the Lias occur in England at Needwood, Whitchurch, and Carlisle in Ireland in the county of Antrim, and also in ScotIn Skye and Ramsay the Lias is 1200 feet thick, and is land. At followed by the Inferior Oolite, Great Oolite, and Oxfordian. Brora estuarine beds of Jurassic age have been worked for coal. 3 Continental Europe. The formations of the English Jurassic are continued into France and Germany, and are well displayed round the Paris basin, in the Franco-Swabian area, and N.W. Germany. In these areas the same divisions and fossil zones are recognisable as those in England, but the nomenclature is that of;
SECT.
III.]
THE GEOLOGICAL SYSTEMS.
175
In the Jura and in Provence the strata are rich in but are greatly folded. The Jurassic formations extend along the whole course of the Alps, but vary in thickness and lithological members, the Upper Oolite being the most widely The Russian type of the Jurassic covers much of Russia extended. and Siberia, and forms a broken zone round the (north) polar
D'Orbigny.
limestones,
regions.
In Swabia petroleum occurs in the Upper Lias marls ; Products. seams of coal of the Yorkshire Jurassic type occur in Bohemia and in Hungary. Lithographic slabs are procured from the limestones of Solenhofen in Germany. 3 North America. In the United States Jurassic rocks cover broad areas in Nevada, Dakota, Utah, and Colorado. In the western districts, especially in Colorado, they have afforded a remarkable series of reptilian forms. 3 South America. Jurassic beds occur in the Andes of Chili and Peru. 17 In India a thick development of Oolite rocks more than Asia. 6000 feet thick occurs in Cutch. The upper divisions (Rajmahal,etc.) of
the great fresh- water
Gondwana
series of Central India are
3 also of Jurassic age. Upper Jurassic strata are also represented in Punjab and the Himalayas. 17
consists of
of South Africa, which saliferous strata, sandstones, limestones, shales, and 17 conglomerates, represents the whole of the Jurassic series.
Africa.
The Uitenhage formation
land,
The Burrum Coal Measure formations of QueensAustralasia. 3 the Wainamatta series of argillaceous shales and thick sandstones of New South Wales, and the Carbonaceous formation of Victoria, which is 5000 feet thick, are of Jurassic age. 17 A massive series of marine and fresh-water beds with coals occurs in New Zealand. 3TRIASSIC SYSTEM.
Types.facies:
(1)
There are three fairly distinct types or paleeontological the Marine type of the Alps ; (2) the Mixed or semi-
marine, semi-continental type of the German Trias; (3) the inland or continental type of Great Britain, South Africa, and Eastern North America. 3Fossils.
The advent of Mammals and Ammonites.
Vertebrata.
Fishes Elasmobranchs, Hybodus, Acrodus ; Ganoids, Palceoniscus ; andDipnoids, Ceratodus. Of Amphibia LabyrinthoOf Reptiles Lizards, donts, Mastodonsaurus, Trematosaurus.Ichthyosaurus, Notosaurus, Telerpeton, Rhyncosaurus ; creatures with crushing teeth, Placodus ; Crocodiles, Stagonolepis. Of Anomodonts (in S. Africa) the mammalian-toothed Galeosaurust
Of
176theequal-toothed
GEOLOGY FOR ENGINEERS.Pariasaurus,etc.
[PT.
III.
CH. IX.
Dicynodon (rordonia,Microlestes.
and the double dog-toothed Of Mammals the teeth and jaws of
Nautilus
Cephalopoda are abundant, Ceratites (fig. 65), 63), Orthoceras (fig. 69), and a few Ammonites. Crinoids are also abundant, Encrinus liliiformis (fig. 48). LamelliInvertebrata.(fig.
branchiatacontorta.
are numerous, Myophoria, Gervillia, and Avicula Gasteropoda occur. Of Crustacea, Estheria (fig. 50),
and Brachiopods, Terebratula, are representative. Flora. Pecopteris, Equisetum, Conifers and Cycads. Great Britain. The Triassic system is most fully developed in the central parts of South Britain, and varies from 750 to 5000 feet in thickness. The Lower Trias or Bunter is formed of the Upper and Lower Variegated Sandstones, with the intermediate Pebblebeds and the Upper Trias or Keuper is made up of the Keuper marls and waterstones. The Bunter series is almost barren of fossils, except in its intermediate zones, where the derived pebbles;
The Keuper is equally contain a few fossils of pre-Triassic age. barren in organic remains. Triassic strata occur also in the basins of the Sol way, the Moray Firth, upon the western coasts and islands of Scotland, and in some of the counties of North-East " Ireland. The Rhsetic or " passage beds occur as a thin band from north of Yorkshire to the Dorset coast. 2 Continental Europe. Triassic rocks occupy the greater part of Germany the Bunter locally affords beds of dolomite, and sandThe distinct central member, the stones with plant remains. Muschelkalk, which is absent in Britain, is generally rich in fossils, while the lower half of the Keuper is marked by impure coal and the upper half by its abundant gypsum beds. The marine development of the Trias is typified by the thickbedded limestones, dolomites, and calcareous shales of the Eastern The individual beds Alps, rich in invertebrata of all types. cannot be paralleled with the German formations, but on the whole are their equivalents in time. 3 World-wide Distribution. The marine strata of the pelagic or Alpine facies of the Trias are of almost world-wide distribution they occur in the Maritime Alps, Apennines, Spain, Balkan Peninsula, Turkestan, Himalayas, and practically surround the Pacific Ocean, being met with in Peru, Colombia, Nevada,;:
California, British Columbia, Alaska, Japan, New Caledonia, and Zealand ; they also occur in Siberia and Spitzbergen. In all these regions their limestones yield the Ammonoid forms Ceratites,
New
Trachyceras, and the Lamellibranchs Daonella, etc. Triassic beds of the continental type occur in South Africa (Karoo series), where they yield the rich reptilian fauna already
SECT. IV.]
THE GEOLOGICAL SYSTEMS.
177
described.
They occur also in South India (Panchet beds), where they yield a few of the same forms. In the coastal regions of North-East America the Trias is represented by red sandstones and shales with abundant footprints of Dinosaurs (Connecticut), with local sheets of melaphyre (Palisades, etc.) and with plantremains (Virginia). Similar Triassic strata occur also in SouthAmerica (Argentina). 3Section IV.Palaeozoic Period.
The Primaryoflife,
all
strata are marked by Palaeozoic or ancient forms the species and all but sixteen genera then existing
being now extinct, as also certain whole families, viz. Graptolites, Rugose Corals, Cystideans, Trilobites and Eurypterids, OrthoCrinoids or ceratites and Labyrinthodont (or frog-like) reptiles. Encrinites and Brachiopod shells were then very abundant in number, and very varied in form. It was the age of Brachiopods. The fishes had heterocercal (unequally-lobed) tails, but no true bony skeleton, though often covered with bony plates. The land plants were chiefly Ferns, giant Lycopods, and Conifers. Note. Entire absence of flowering plants, birds, and mammals. 2
DYAS OR PERMIAN SYSTEM.The Carboniferous system in Britain is overlain by a great thickness of red sandstones, shales, limestones, and marls which was formerly considered to be one system and was named the New
Red Sandstone.
Subsequently,
it
was found to be composed
of
two
distinct systems, the older of which is known as Permian and is 3 of Palseozoic age ; the younger, as Triassic, of Mesozic age. The advent of reptiles. Fossils are nearly confined to Fossils.
the marl, slate, and limestone bands. There are but few distinctive forms, most being mere survivals from the Carboniferous, which are of ordinary size in the lower beds but higher up become stunted
and
finally disappear.
2 3-
Vertebrata.slate,
Fishes
:
Palceoniscus,
and
copper
shales.
Platysomus, in the marl Labyrinthodonts JSranchiosaurus,:
Lepidotosaurus, and a true reptile (lizard), Proterosaurus. The Polyzoan Fenestella retiformis (fig. 54) ; Invertebrata. the Brachiopods, Productus (fig. 57) ; Spirifer (fig. 55) ; the Lamellibranchs, Bakevellia, Avicula, etc. Gasteropods are rare.
The Cephalopod Nautilus
(fig.
63).
In Great Britain and Europe Callipteris and Walchia Flora. are characteristic ; in Central India and southern hemisphereGlossopteris
and other Mesozoic types. 312
178Great Britain.
GEOLOGY FOE ENGINEERS.
[PT.
III.
CH. IX.
the east side of England, from the coast to the plains of the Trent, the Permian rocks consist of a great central mass of limestone ; but on the west side of the Pennines, and extending southwards into the centralof
On
Northumberland
counties, the calcareous zone disappears and we have a great accumulation of red, arenaceous, and gravelly rocks. The Lower division is typically developed in the Vale of Eden, where it consists of brick-red sandstones and breccias; the red rocks extend into the valleys of the Nith and Annan in Scotland, and the breccias, further south in Staffordshire, attain a thickness of 400 feet. The Upper division is best seen at St Bees, near Whitehaven. The Permian rocks of North Ireland consist of fossiliferous magnesian limestone with red marls at its base, and at the city of Armagh, of boulder beds and limestone breccias.
Products.
Some
of the finest building-stones of the country,
such as the Mansfield sandstones and the magnesian limestones of Durham, York, and Nottingham ; marls for brickmaking and a thick bed of rock-salt. 3 Continental Europe. In Northern Germany the Permian is made up of the Zechstein and Rothliegende, which constitute the so-called Dyassic type of the system. The Rothliegende occurs also in Bohemia, Saxony, the Saar district in S.W. Germany, and at many localities in Central France. In the typical Russian district of Perm the Permian strata cover vast areas, and consist of sandstones, limestones, and marls and shales in repeated In the Alps the Permian is represented by the alternation. Verrucano, and in the Tyrol by the sandstone and quartzporphyry series of Botzen, and by the richly fossiliferous marine In Carinthia and Sicily the entire series Bellerophon limestone.is
Copper-bearing deposits of Germany and Persia and coal-seams in France. North America. Permian rocks are rare. The highest division (the so-called Barren Measures) of the Coal Formation of the Alleghany region have been referred to the Permian, and contain an admixture of Coal Measure and Permain forms, In together with genera characteristic of the Jurassic period. Texas certain mottled clays, sandstones, and limestones, overlying the local Coal Measures, are referred to the Permian. Marine rocks of this age also occur in Spitzbergen? South America. Strata of the Indian Gondwana type with the GlossOpteris flora have been met with on the east of the Andes in Brazil and Argentina? Asia. In Southern India the Permian beds consist of great thicknesses of sandstones and shales, with fresh-water and
marine. Products.
many workable
SECT. IV.]terrestrial
THE GEOLOGICAL SYSTEMS.
179
the plants include Glossopteris and other fossils ; Mesozoic types, which are sometimes so abundant as to constitute valuable seams of coal. They form the lower half of the Gondwana series and comprise the Talcher, which is distinguished by its remarkable conglomerates or boulder beds (which are met with not only south of the Nerbudda River but in the Salt Range of the Punjab) and the Damuda with workable coal-seams. 3 The beds in South Africa are similar to those of Africa. South India. A group of sandstones and shales (Lower Karoo or Ecca beds), with local coal-seams, affords examples of Glossopteris and shows at its base a remarkable boulder bed (Dwyka) which has been compared with the Indian Talcher. 3 Similar beds to those of Southern India and Australasia. South Africa occur in Australia, hence it has been suggested thatthese three widely separated regions formed part of a single Permian continent. At Bacchus Marsh and elsewhere in Victoria sandstones and shales with the Glossopteris flora, associated with boulder conglomerates with striated pebbles, like those of the The Upper or Newcastle division of the Talcher, are met with.of
workable Coal Measures of New South Wales is also, probably, Permian age. In Queensland the local Permian is made up of a lower marine series with abundant Brachiopods and Cephalopods, and an upper fresh-water series with Glossopteris, etc. 3
CARBONIFEROUS SYSTEM.Fossils.
The age
of
Cryptogamic plants, Corals, and Crinoids.
the coal-bearing strata are marine, estuarine, and The marine forms are generically related to those terrestrial. of the Carboniferous Limestone, viz. abundant Corals, Encrinites,fossils of
The
Brachiopods, Cephalopods with rare Eurypterids, Phyllopods and Trilobites and occasionally Sponges, Annelids, and Scales and teeth of large Elasmobranch fishes are not Protozoa. uncommon. The estuarine forms include mussel-like forms, such as Anthrocosia. The terrestrial forms embrace rare forms of Articulata, such as scorpions, beetles, crickets, may-flies, etc., but the most abundant are plants including many Cryptogams and a few Gymnosperms. Among the Cryptogams are tree-like Lycopods,Polyzoa,3 Ferns, and Equisetums. Great Britain. This great system attains a maximum thickness of 20,000 feet and is made up of limestones, grits, Calcareous strata with sandstones, shales, coals, and ironstone. marine fossils prevail generally in the lower half of the system, and sandy and shaly strata with abundant land-plants in the upper half. The Upper Carboniferous or series of Coal Measures is djvide4
180
GEOLOGY FOR ENGINEERS.
[PT.
III.
CH. IX.
of the Millstone grit, The Middle or Grey which, however, is absent in the Midlands. Coal Measures afford the richest and most valuable seams of coal mined in the British coal-fields. Three of the chief British coalfields occur in the neighbourhood of the Bristol Channel ; six in the Midlands and the Welsh border ; five in the Pennine region ; three in Central Scotland ; and three in Ireland. In Southern Britain coal-measures have been proved to exist below some of the more recent formations. The Lower or Carboniferous Limestone series is typically developed in the Southern Pennines, where the Yoredale group of shales, limestones, and sandstones is from 1500 to 4500 feet thick and the limestone from 2000 to 4000. The same series recur in North Wales. In South Wales, Mendip Hills, and the Forest of Dean the Yoredale rocks are wanting. Passing northwards the limestone is gradually replaced by a series of sandstones, grits, and shales with occasional bands of limestone, which develops into the Calciferous group of sandstones, shales, and cement stones with a series of workable coals overlain by the Carboniferous Limestone, in the north of Scotland and north of Ireland. In Central Ireland the whole of the Lower Carboniferous is practically represented by limestones ; but in the extreme south of the island it becomes replaced by cleaved grits, sandstones, and In the central parts of Devonshire the whole of the shales. Lower and perhaps some of the Upper Carboniferous is represented by a mixed group of greywackes, flags, shales, and thin bands of limestone of the "Culm" type. 3 Continental Europe. Carboniferous strata of the Pennine type occur in Belgium and North France ; of the Culm type in West and North Germany, Central Europe, and the Alps ; and of The the Limestone (S. Wales) type in Russia and the Urals. chief European coal-fields are those of France and Belgium, Westphalia, Saarbriick, Silesia, Bohemia, and Russia, Central3 France, and Northern Spain. North America. Carboniferous rocks are grandly developed Their lower divisions in Nova Scotia and the United States. (sub-Carboniferous) are typically limestones, with abundant marine fossils ; and the beds of their highest division, which form the rich coal-fields of Nova Scotia, Pennsylvania, and the basins of the Ohio and Mississippi, are prolific in terrestrial plants
from the Lower by the arenaceous formation
and
afford
many remarkable
terrestrial Articulata. 3
Asia.
Carboniferous rocks,
covering large
areas,
occur
in
Northern China; they are made up of limestones below, with Fusulina, etc., rich coal-measures in the middle, and marine sandstones above. 3 Coal and Carboniferous limestone occur in
SECT. IV.]
THE GEOLOGICAL SYSTEMS.
181
Japan. Coal of this period is also found is some islands of the Indian Archipelago and in Borneo. 1 ^ Africa. Rocks with Carboniferous fossils occur in the Sahara and in Egypt? Coal has been noticed on the banks of the Zambesi, and occurs in the Transvaal and Orange River Colony. Natal coal is of Triassic or Permian age. 17 The Carboniferous rocks of New South Wales are Australia. formed of two distinct divisions, both containing workable coals. 3
DEVONIAN SYSTEM.There are two distinct types of strata: (1) the Types. Fresh-water or Old Red Sandstone, and (2) the Marine or Devonian. The age of Fishes and Eurypterids. Fossils.
Old Red Sandstone.
The Fauna is remarkable for the predominance of tishes. Their skeletons were cartilaginous, and their tails either diphyTheir bodies were sometimes naked, but more or hetero-cercal. 2 generally protected by an armour of plates, or a covering of granules, ganoid, or placoid scales, and in some cases were even provided with various protective spines (Ichthydorulites). The Old Red fishes included lamprey - like forms (Palceospondylus), fishes shell - skinned Ganoids (Ostracodermi), joint -necked (Coccosteus), fringe-finned Ganoids (Holoptychius, etc.), Dipnoids or mud-fishes (Dipterus, etc.), and shark -like Elasmobranchsthese fishes occur the giant Crustacea or Arachnoids Eurypterus (fig. 51), Pterygotus, and Stylonurus. The Flora are few in the Lower series and include Psilophyton and other marsh plants those of the Upper Old Red Sandstone;
(Acanthodes, etc.). Associated with
3
are
more common and embrace Lycopods and Ferns.Devonian.
Graptolites die out; a peculiar sponge, (?) Stromatopora, as do Corals (Favosites, fig. 44 ; Heliolites, fig. 45 ; " " Calceola, fig. 42), which form the Madrepore marble of Torbay and Plymouth. Trilobites are few, but large allied Crustaceans Brachiopod and Lamelli(Eurypterus, Pterygotus) continue. branch bivalve shells, and the Cephalopods, Orthoceras, Clymcnia, 2 Goniatites, Nautilus, are the most abundant fossils. Great Britain. The Old Red type occurs from the Bristol
abounds,
182
GEOLOGY FOE ENGINEERS.
[PT.
III.
CH. IX.
Channel through Wales, Central and North-East Scotland to the Shetlands j and also largely in Ireland. Everywhere a great break occurs between the Upper and Lower groups. It consists of lake deposits (in Lakes Orcadie, Lome, Caledonia, Cheviot, and Welsh lake), and in Scotland often abounds in fish remains and There, too, interbedded volcanic rocks occur, more land-plants. than 6000 feet thick, and form the Pentland, Ochil, and Sidlaw " the basal wrecks of extinct volcanoes." hills, which are The Devonian type occurs only to the south of the Bristol Channel, and consists of a great thickness of grey and blue slates, 2 schists, sandstones, and limestones rich in corals. Continental Europe. Old Red Sandstone strata occur in Northern Russia with typical fishes, in Norway with remarkable igneous rocks, and in Spitzbergen and Bear Island with abundant Devonian strata sweep almost uninterruptedly plant remains. Europe from Calais to the Urals. In Belgium and the through Rhine provinces all three divisions are present in great thickness and rich in characteristic fossils. In Russia they are almost horizontal, and interbedded with red sandy strata with Old Red In Bohemia they consist of limestones rich in Orthoceratites fishes. and Goniatites. Devonian rocks are also met with in many other3 parts of Europe.
North America. Old Red Sandstone beds are met with in Gaspe and New Brunswick, containing Lycopods, Calamites, Ferns, and even a few Conifers, often in such abundance as to form seams of coal. In the United States Devonian rocks include a Lower division of sandstones and limestones (Oriskany and Corniferous), with Brachiopods and plants a Middle division of black shales and limestones (Hamilton) with Goniatites and Productus; and an Upper division (Chemung) which is formed, in some districts, of limestones rich in Clymenia, and in others 3 of red sandstone (Catskill\ with Upper Old Red Sandstone fishes. strata are the source of immense The Devonian Products. supplies of petroleum which, it is thought, has distilled from decomposing animal matter in the limestones, such as fishes, crustaceans, and mollusca, whose hard parts are embedded in it;
in great abundance. bitumen. 5
This
is
also the source of the deposits of
(UPPER) SILURIAN SYSTEM.Fossils.
The age
of
and Trilobites ; and Insects. Scorpions,Encrinites,
Brachiopods ; advent of
abundanceVertebrates
of:
Corals,
Fishes,
The
Pteraspis,
Fishes are Elasmobrancliii or Ostracodermi (Cephalaspis^ The Arachnida or forms of scorpions appear. etc.).
SECT.
IV*.]
THE GEOLOGICAL SYSTEMS.
183
Amongare
Crustacea, Trilobites are abundant, Phacops, Calymene, and
Homalonotus being commonest.
Cephalopoda and Gasteropoda
Orthoceras and Betterophon (fig. 62). represented by Brachiopoda are the most prevalent and characteristic of the The Echinodermata system, especially Pentamerus and Spirifer. the are represented by star-fishes and crinoids, and of Of the Ccelenterata both Actinozoa and Hydrozoa are abundant. former the Corals are chiefly rugose, while in the latter the great group of Graptolites becomes extinct within the limits of the
system.
Of Flora but little is known ; but both Lycopods and Ferns 3 appear to have been in existence. Great Britain. The typical area is that of Shropshire, and the same type is prolonged south-westward along the Welsh border (where an older formation the Lower Llandovery makes its appearance at the base of the system), and south-eastward and eastwards into the areas of Woolhope, the Malvern Hills, and South Staffordshire, etc.strata of the greywacke type sweep through the parts of Wales from Cardigan to Denbigh, the Llandovery being represented to the south by great thicknesses of grits, and to the north by a few bands of graptolitic shales, while the equivalents of the Wenlock and Ludlow are more or less barren grits and shales, which thicken northwards (Denbigh Grits and Flags}. The same is the case in Westmoreland, where the Skelgill and Browgill Shales answer to the Llandovery, the Coniston Grits and Flags to the Wenlock, and the Bannister Slates and Kirkby Moor Flags to the Ludlow formations. Rocks of the greywacke type floor almost the whole of the Scottish uplands. The most widespread formation is the Gala Group (Tarannon), which is underlain by the thin but richly graptolitic formation of the Birkhill Shales (Llandovery), and overlain by another In greywack^ formation, the Riccarton Beds (Wenlock). Ireland, Silurian rocks of the Shropshire type occur in Galway and Kerry, and of the types of those of Birkhill and Gala of the
Silurian
central
southern uplands, in Londonderry, Cavan, and Down. 3 Continental Europe. In Northern Europe the Silurian rocks are usually limestones, as in Norway, Central Sweden, Gothland, and Esthonia, but are locally intermixed with or replaced by carbonaceous shales with graptolites, as in Scania and Dalecarlia. In Bohemia two lithological members occur, an Upper or CalIn France and careous series and a Lower or Graptolitic division. Belgium the Ludlow is partly represented by marls, and all the formations below by grey and black shales with graptolites. 3 North America. The majority of the rocks remind us both of
184
GEOLOGY FOR ENGINEERS.
[PT. III. CH. IX.
The Llandovery is reprethose of Shropshire and Scandinavia. sented by sandstones and shales (Oneida and Medina], the Wenlock by shales and calcareous beds (C'Union and Niagara], and the Ludlow by three formations the Salt Group of Onondaga, the Water-lime with Eurypterus, and Lower Helderberg limestones with abundant forms of Pentamerus. 3 Lower Silurian rocks occur in the Salt Range and Simla Asia. area, while in the great chain of the Himalayas, Silurian rocks, flanked by Secondary formations, form part of the central axis of the range. In China, Silurian Graptolites and Orthoceratites have been met with. Similar formations spread over large tracts in Southern Siberia, in the Altai Mountains, and in Asia Minor. 17 Australia. Silurian fossils occur in Southern and Western Australia, and it is in the highly metamorphosed Silurian rocks that auriferous quartz-veins so frequently occur. 17ORDOVICIAN OR LOWER SILURIAN SYSTEM.Silurian strata cover a wider extent of the earth's surface and are more uniform in nature of deposits and fossils than any other
group.
The age of Graptolites, Trilobites, and Cystideans. Fossils. Graptolites are the characteristic fossils ; they are found in more or less abundance in strata of all lithological types, but are most Of Trilobites the prevalent in the thin-bedded black shales. primordial genera Olenus, etc., die out, and Asaphus, Calymene,
2
and Ogygia Buchii first appear. Corals were few, but Brachiopods and Cystidean Echinoderms swarmed. Gasteropods first appear, also Cephalopod-chambered shells. 3 ex. Bellerophon Great Britain. The typical area is North Wales. The Arenig beds, containing enormous sheets of volcanic rocks, sweep round the Merionethshire anticlinal, forming the ranges of Cader Idris, the Arans, and the Arenigs, etc. They are succeeded by a great thickness of barren, dark shales, representative of the Llandeilo. The final division is made up of grey flagstones and shales with the typical Bala limestone near the base, and the Hirnant limeThe upper of the two volcanic groups of stone near the summit. the Ordovician of North Wales is comparatively thin near Bala, but expands to an enormous thickness, and forms the mountainIn the Lake District ranges of Snowdon and Penmaenmaur, etc. the two volcanic series are connected by intermediate masses of This lava and ashes and form collectively the Borrowdale series. is underlain by the Skiddaw slates and overlain by the Coniston In the Girvan district of South Scotland the lowest limestone. Ordovician rocks are the Ballantrae volcanic series. The Llandeilo;
SECT. IV.]
THE GEOLOGICAL SYSTEMS.
185
seems to be represented by the Stinchar group of conglomerates and limestones, and the Bala by the Ardmillan series of flagstones and shales. At Moffat, etc., the Upper Llandeilo and Bala beds are represented by the Glenkiln and Hartfell shales of the thinbedded Moffat series. In Tyrone In Ireland Ordovician rocks occur in many areas. and Mayo they are of the Girvan type in Down and Cavan they have a Moffat facies at Kildare and elsewhere in Central Ireland in they call to mind the Bala beds of the Lake District Wicklow and Wexford they are of the type of the sedimentary and volcanic rocks of North and South Wales. 3; ; ;
The Ordovician rocks attain their widest Continental Europe. Scandinavia and Esthonia, where they are thin, horizontal, and rich in fossils ; their calcareous members have a far more varied fauna than those of Britain, but their graptolitic members agree with ours almost specifically. The same is also the case in Belgium, but the rocks are more disturbed. Important beds occur in Western France and in Bohemia* North America. The Ordovician strata are of two main types the calcareous type of the central regions, including the Calciferous sandstone, the Chazy and Trenton limestones, and the Utica and Hudson River (Cincinnati group) shales and the greywacke and black-shale type of the Hudson River and the lower reaches of the St Lawrence, including the graptolite-bearing Quebec group (Point Levis beds) and the Marsouin and Norman's Kill shales,extension in;
etc. 8
Asia. Lower Silurian rocks occur in the Salt Range and the Simla area of India. 11 Ordovician strata with abundant Arenig and Australasia. Llandeilo graptolites are found in Australia (Victoria) and alsoin
New
Zealand. 3
CAMBRIAN SYSTEM.This system consists of a vast succession of reddishgrits, con-
glomerates, shales, slate, and quartzite ; but there is no gneiss, and there are few schists and fewer limestones. It is divided into5 Upper, Middle, and Lower zones.
Fossils.
The
genus Olenellus(fig.
(fig.
characteristic fossils are Trilobites, of which the 52) characterises the Lower, Paradoxides
The chief 53) the Middle, and Olenus the Upper Cambrian. invertebrate groups which occur, in addition, are Cephalopoda,Gasteropoda, Lamellibranchiata, Pteropoda, Brachiopoda, Asteroidea, Vertebrata are very doubtCrinoidea, Hydroida, and Sponges. fully represented ; and of plants only sea-weeds are known to
186
GEOLOGY FOR ENGINEERS.
[PT.
III.
CH. IX.
Great Britain. The Cambrian rocks of Merionethshire have been estimated at 15,000 feet in thickness. They consist of the Tremadoc slates, Lingula flags, Menevian beds, and Harlech series. At St David's (9000 feet thick) the Upper Cambrian is represented by the Tremadoc beds and Lingula flags, the Middle by the Menevian beds and Solva group, and the Lower by the Caerfai group, with evidences of Olenellus. In Shropshire the Cambrian consists of three members the
Wrekin quartzite at the base, the Cornley sandstone, and the Shineton shales. In the Malvern Hills the Cornley or Hollybush sandstone lies at the base of the Cambrian, and is followed by black shales with Dolgelly trilobites and green shales with In the Nuneaton district there are two members Dictyonema. In the Norththe Hartshill quartzite and Stockingford shales. west Highlands of Scotland a band of Cambrian strata ranges from Eriboll almost to Skye, comprising (1) Eriboll quartzite; (2) Fucoid beds; (3) Salterella grit; (4) Durness limestone. Near Bray Head in Ireland occur certain coloured slates and grits 3 usually referred to the Cambrian. Cambrian rocks are well displayed in Continental Europe. Scandinavia and North- West Russia ; they are usually horizontal and of no great thickness, but yield a rich fauna, the characteristic genera of the Lower, Middle, and Upper Cambrian being all Cambrian rocks occur in Bohemia, Bavaria, France, present.Belgium, Spain, and Sardinia. Asia. In India, Lower Cambrian fossils occur in the Salt Range of the Punjab, and Higher Cambrian fossils are met with in Northern China. 3 North America. Well developed in North America. The Lower Cambrian or Olenellus zone is shown in the Rocky Mountains, the Alleghanies, the Taconic Ranges, and in NewThe typical Middle Cambrian fossils are most foundland.3
abundant in New Brunswick (Acadia), Massachusetts, and Newfoundland. The Upper Cambrian (Potsdam sandstone, etc.) formations occur in Canada and in the basin of the Mississippi and the highest Cambrian or Dictyonema beds in the valley of;
the St Lawrence. 3 Australasia. Olenellus has been found in Western Australia.
Section V.
Eozoic Period.
ARCH^AN AND PRE-CAMBRIAN ROCKS.All rocks of greater antiquity than the oldest fossil-bearing strata of the Cambrian are grouped together as Pre-Cambrian or
SECT. V.]
THE GEOLOGICAL SYSTEMS.
187
Archaean. These rocks, unlike those of the subsequent fossiliferous systems, have not yet been satisfactorily divided into formations and systems. They present themselves under three types (a) coarsely crystalline gneisses and schists associated with plutonic igneous rocks ; (6) finely crystalline schists and gneisses associated with more or less metamorphosed sedimentaries and volcanics ; and (c) unaltered sediments and contemporaneous lavas, ashes,:
and
tuffs.
3
fossils yet obtained from the worm-burrows and worm-tracks. The crystalline limestone of the original Laurentian of North America have yielded the problematic fossil Eozoon Canadense, some of the more or less metamorphosed groups of the Huronian type, a few traces of Annelids, sponges, and plants and the unaltered 3 formations, forms of Protozoa, Mollusca, and Molluscoidea. Great Britain. In the North-West Highlands occur the Leivisian, which consists of coarsely crystalline gneisses and schists more or less inclined above which and unconformably rests the Torridonian, composed of masses of chocolate-coloured sandstones and conglomerates approximately horizontal. In Ireland there are gneissic rocks with micaceous and chloritic schists associated with granite in Wicklow, and gneisses and serpentinous limestones in Galway and Donegal, in all probability of Archaean age. In Wales occur the Dimetian, composed of granites and gneiss, covered by the Arvonian strata of volcanic rocks, and on the latter rest unconformably the Pebidian strata of slates and shales,
Fossils.
The only undisputedof Britain are
Pre-Cambrian rocks
\
;
etc.
Pre-Cambrian rocks occur in Anglesea, Shropshire (the Long-
myndian and Uriconian series), in the Malvern and at Charnwood Forest in Leicestershire. 3
Hills, at
the Lizard,
Continental Europe. Pre-Cambrian rocks of all the British types cover large areas in Scandinavia and Finland, occur also in France and Spain, and in the cores of the great European 3 mountain-ranges. " massifs " of Asia. In India there are two great gneissic and rocks the one forms the extensive upland and crystalline plateau tracts that extend from Ceylon through the Madras, Bengal, and Bundelkhand districts to Assam ; the other constitutes the colossal framework of the Himalayas. These Archaean gneisses are succeeded unconformably by a series 2000 feet thick ofquartzites, conglomerates, schists, slates, breecias, and limestones, associated with contemporaneous bedded igneous rocks. 17 North America. These rocks occupy a connected area of two million square miles, having Hudson Bay as its centre. They
188
GEOLOGY FOR ENGINEERS.
[PT.
III.
CH.
IX.
comprise a lower or Basement complex consisting of coarsely gneissose types, which was formerly called Laurentian, and an upper division known as AlgonJcian or Proterozoic which is divided into a Keewenawan, resting on an Upper and a Lower Huronianall of finer crystalline schists
South America.of Brazil,
and sediments, etc. 3 These rocks range through the greater part Guiana, and Venezuela and occur again in the Andes of
Pre-Cambrian rocks form considerable rocks tracts in 17 Algeria and on the eastern borders of Egypt. Australasia. Gneissic and crystalline rocks occupy large tractsin
Chili." Africa.
South -Western Australia.Zealand. 17
New
They
are also well developed in
PARTWHILE
IV.
GEOLOGICAL OBSERVATION.a theoretical knowledge of geology,as set forth verybriefly in the three preceding parts of this book, is of great value to the engineer as a necessary groundwork to any study of the
In the practical application of geology to engineering, which is the subject of the concluding part of this book, it is essential that the geological factors should be based on the most reliable data. Hence all geological observation must be carried on in the most accurate and careful manner possible. Every fact which throws light on the area observed must be carefully noted and the record must be both full and accurate. The observer should train himself not to jump to conclusions, but to view every bit of evidence with regard to the nature and structure of the rocks which are concealed from view, and must learn to interpret rightly such facts as are patent, without minimising their value or too greatly^
subject, the methods of geological observation, with in this part, are of fundamental importance.
which are dealt
exaggerating
it.
1
189
PT. IV. CH. X.
CHAPTER
X.
OUTDOOR WORK.EQUIPMENT.
equipment or outfit for the field should be one can do good work of any kind with a regular "Christmas tree" slung round him. The following instruments are, however, indispensable hammer, knife, lens, 1 compass and clinometer, note-book, and tape or other measure. Hammer. The most important implement of the geologist.ITis
essential that the
as light as possible.
No
:
It may be light or heavy, short- or long-handled, according to the nature of the work to be done and the fancy of the individual, but it must be heavy enough to break up any ordinary rock
which is met with. Most geologists recommend a square face with a chisel-shaped tail end, the cutting edge of the chisel being Sir A. Geikie at right angles to the axis of the handle shaft. considers a hammer weighing one pound, or a few ounces more, quite sufficient for the ordinary purposes of a field geologist but, when it is intended to collect specimens, a hammer weighing two or three pounds or even more will be required, and a small chipping or trimming hammer as well. If, therefore, the engineer has time and opportunity to devote to geological observation he will do well to collect rock specimens for future reference, and should 1 provide himself with both hammers. Chisel. geologists prefer to dispense with a Though many chisel, there is no doubt of its convenience where blocks of rock have to be worked out from a cliff-face, or in any place where t