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Carbonate Sediments and Rocks
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Carbonate Sediments
and Rocks
A Manual for Earth Scientists
and Engineers
Colin J. R. Braithwaite
Division of Earth Sciences, University of Glasgow
Whittles Publishing
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Typeset by
Mizpah Publishing Services, Chennai, India
Published by
Whittles Publishing,
Dunbeath Mains Cottages,
Dunbeath,
Caithness KW6 6EY,
Scotland, UK
www.whittlespublishing.com
© 2005 C. J. R. Braithwaite
ISBN 1-870325-39-7
All rights reserved.
No part of this publication may be reproduced,
stored in a retrieval system, or transmitted,
in any form or by any means, electronic,
mechanical, recording or otherwise
without prior permission of the publishers.
Printed by Interprint Ltd., Malta
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Contents
Introduction: Why Study Carbonate Sediments and Rocks? 1
Acknowledgements 2
Chapter 1: The Mineralogy and Compositions of Carbonate
Rocks and Sediments 3
Introduction 3
1.1 The Mineralogy of Common Carbonate Minerals 3
1.2 Geochemistry 8
Chapter 2: Characteristics of Carbonate Sediments 12
Introduction 12
2.1 Carbonate-Forming Organisms and Structures of Biogenic Grains 12
2.2 Production and Transport of Biogenic Grains 16
2.3 Chemically Generated Grains 17
Chapter 3: Marine Carbonate Environments 21
Introduction 21
3.1 Beaches 23
3.2 Tidal Margins 24
3.3 Restricted Shelves and Lagoons 26
3.4 Open Shelves 27
3.5 Oolite Shoals 28
3.6 Grapestones and Hardgrounds 29
3.7 Reef Systems 30
3.8 Milankovitch and Sea-Level Change 35
3.9 Platform Margins and Slopes 36
3.10 Pelagic Sediments: Carbonate Muds and Chalks 39
3.11 Temperate-Water Carbonates 41
Chapter 4: Evaporites Associated with Carbonates 43
Introduction 43
4.1 Evaporite Models 43
4.2 Physical Properties of Evaporites 44
Chapter 5: Continental Carbonate Environments 45
Introduction 45
5.1 Weathering, Erosion and the Dissolution of Limestones 45
5.2 Calcrete 45
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CARBONATESEDIMENTSANDROCKS
5.3 Cave and Stream Deposits 46
5.4 Carbonate Lakes 47
5.5 Aeolian Deposits 50
Chapter 6: Classification of Carbonate Sediments and Rocks 52
Introduction 52
6.1 Classification of Carbonate Sediments 52
6.2 Classification of Carbonate Rocks 53
6.3 Classification of Porosity of Carbonate Rocks 57
Chapter 7: Carbonate Diagenesis: from Sediment to Rock 60
Introduction 60
7.1 Crystal Growth and Cements 60
7.2 Diagenetic History 63
7.3 Metamorphism and Marbles 80
7.4 Silicification of Limestones 81
7.5 Return to the Surface 81
Chapter 8: Dolomites 83
Introduction 83
8.1 Conceptual Models of Dolomitisation 83
8.2 Geometry of Dolomite Bodies 86
8.3 Dolomite Petrography 86
Chapter 9: Calcrete 88
Introduction 88
9.1 Geochemistry 89
9.2 Mechanism of Formation 89
9.3 Morphology of Calcretes 90
9.4 Profiles and Catenas 92
Chapter 10: Limestones, Dolomites and Karst 93
Introduction 93
10.1 Dissolution of Limestones 93
10.2 Karst Landforms 96
10.3 Caves 101
10.4 Precipitation 102
10.5 Biogenic Facies 103
10.6 Karst and Sea-Level Change 104
10.7 Paleokarst 104
Chapter 11: Karst Hydrology 106
Introduction 106
11.1 Water and Porosity 106
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CONTENTS
11.2 Darcy’s Equation and Groundwater Flow 106
11.3 Springs 109
11.4 Water Quality 110
Chapter 12: Engineering Properties of Carbonate Sediments
and Rocks 111
Introduction 111
12.1 Engineering Properties of Carbonate Sediments 111
12.2 Engineering Properties of Calcrete 112
12.3 Physical Properties of Limestones and Dolomites 113
Chapter 13: Methods of Extraction of Carbonate Sediments
and Rocks 119
Introduction 119
13.1 Dredging 119
13.2 Quarrying 120
13.3 Processing 121
Chapter 14: Engineering Case Histories: The Hazards of Karst 122
Introduction 122
14.1 Detection 122
14.2 Collapse of Buildings 123
14.3 Dam Construction 123
14.4 Railways, Roads, Bridges and Airports 126
14.5 Water Supply 126
14.6 Hazards of Evaporite Karst 128
Chapter 15: Hydrocarbons, Mineral Deposits and Carbonates 129
Introduction 129
15.1 Mineral Deposits 129
15.2 Carbonates and Hydrocarbons 132
Chapter 16: Carbonates and Conservation 139
Introduction 139
16.1 Quarrying 139
16.2 Landscapes 139
16.3 Caves 140
16.4 Fossils 141
References 142
Index 159
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Introduction
Why Study Carbonate Sediments
and Rocks?
Carbonate rocks, limestones and dolomites for the geologist and earth scientist, and a pre-
have a disproportionate economic and engin- dictive framework for engineering works in
eering importance. Although they represent areas occupied by them. The environments
only about 15% of rocks forming continental considered include the tidal margins, shallow
areas today, limestones are the fundamental lagoons, coral reefs, continental shelves, the
ingredient in the manufacture of cement and deep oceans and cool-water carbonates in the
provide both building stones (dimension stones marine realm, together with cave, stream and
and cladding) and aggregates. They have been lake deposits, and the special issues of calcretes
used in the construction of many of the archi- in land-based systems.
tectural wonders of the world, including Discussion of the changes that take place in
St Peters in Rome, the Taj Mahal in India and carbonate sediments on burial, leading to the
the Great Pyramid at Giza in Egypt. They offer formation of rocks, offers an understanding
some of our most startling landscapes and in ofthe processes of compaction, the growth of
these have the additional dubious distinction of cements, and the concomitant evolution of
generating some of the most intractable hydro- porosity and strength. A section devoted to the
logical and foundation problems. Limestones study of dolomites reflects on their importance
and dolomites together provide the reservoirs as host rocks for hydrocarbons and mineral
for some 40% of the World’s oil reserves and deposits but is also of value for the light they
are the host rocks to a variety of ore deposits shed on the issues of migration of the fluids
including lead-zinc-barite-fluorite and copper involved in diagenetic change. Schematic classi-
deposits, as well as bauxite and phosphorites. fications that simplify the description of car-
The carbonate sediments from which lime- bonate sediments and rocks and of porosity are
stones originate dominate present-day tropical included and explained. Together these data
coastal and shelf environments, and locally provide information for the earth scientist and
form a significant proportion of shelf sediments a reference framework in which the practising
in temperate seas. They are of substantial envir- engineer unfamiliar with the terms is able to
onmental significance but also act as the foun- understand and evaluate reports provided by
dations for a wide range of coastal works and experts from other fields.
offshore structures. The geomorphology and hydrology of karst
The geological background to carbonate regions revolve around the peculiarities of the
sediments and rocks includes basic information landforms developed on rocks that are rela-
on the compositions, origins and distributions tively soluble, but also bear on a number of
of carbonate sediments. Descriptions of the economic issues. The engineering properties of
varied environments in which these sediments carbonate sediments, limestones and dolomites
form offer conceptual models of such systems are discussed together with the difficulties of
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