Logging the Chalk: 1st Edition (Hardback) book cover

Logging the Chalk

1st Edition

By Rory N. Mortimore

Whittles Publishing

352 pages

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Hardback: 9781482246711
pub: 2014-10-13
$190.00
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Description

Chalk has proved to be one of the more difficult rocks to corelog as it breaks up readily during the drilling process leading to core-loss and destructuring, particularly where flints, nodular chalks, and/or fractures are present. One of the greatest difficulties is the identification of chalk engineering grade which relies heavily on fracture aperture. Obtaining the correct grade to define the depth of weathering and the depth at which fractures become closed is essential whether for tunnels in London or wind turbine piled foundations in the offshore chalks. Very few geologists and engineers have had the opportunity to study field sections in the chalk so there is little visual appreciation of the grades or the variation to expect or even what flint bands look like. To partly overcome this difficulty, both field and core sections are illustrated in this book.

Equally important to recognizing chalk grade is the building of conceptual ground models for construction projects. This can only be achieved if the various chalk formations, beds, and marker beds can be identified from cores and then boreholes correlated using the marker beds. The chalk stratigraphy is accordingly covered with key formations and marker beds illustrated, and the best field sections for viewing them identified.

This book is based on the standard lithostratigraphy and method of engineering description of chalk developed over many years. Also important are over 3,000 onshore and offshore chalk-cored boreholes undertaken by the author over more than 30 years. In addition, typical lithologies and weathering profiles representing the chalk formations likely to be encountered in the various onshore and offshore construction projects are illustrated using both field exposures, rotary core samples, and geophysical borehole wire-line logs.

There are geological settings where information on the chalk is poor and unexpected lithologies and stratigraphies may be found. This book will enable geologists to work from first principles to construct a lithostratigraphy and define weathering boundaries.

Table of Contents

Introduction

Acknowledgements

Chapter 1 Describing, classifying and interpreting the Chalk for engineering purposes using field exposures and rock cores

Introduction

Equipment required for logging, engineering description and classification

Describing chalk sediments

Carbonate content and density measurements

Recognising and describing chalk beds

Recognising and describing phosphatic chalks

Recognising and describing marly chalks and marl seams

Recognising and describing flints and flint bands

Synsedimentary and immediately post-sedimentary structures

Using fossils as an aid to logging

 

Chapter 2 A stratigraphic framework for the Chalk: Southern Province

Regional setting

Southern Province Chalk Group

 

Chapter 3 A stratigraphic framework for the Chalk: Transitional Province

Regional setting

Berkshire Downs and Chiltern Hills

Correlation framework from the Chiltern Hills to East Anglia and the Northern Province

Marker beds in the Chalk beneath London

East Anglia

Chapter 4 Chalk formations and marker beds in the Northern Province of England, onshore and offshore

Introduction

Regional setting

Northern Province Chalk stratigraphy

 

Chapter 5 Central Graben and Northern North Sea Chalks

Regional setting

Stratigraphy of the Chalk in the North Sea

Distribution of formations in the UK sector, Central and Northern North Sea

Describing North Sea chalks

North Sea lithologies and core log representation

 

Chapter 6 Logging the Chalk: styles of weathering found in core and field sections, with examples of CIRIA chalk grades in rock core

Introduction

When should chalk be described as weathered?

Discoloured chalk

Smell

Mechanical breakdown, fracturing and CIRIA grade

Influence of geological setting on weathering of the Chalk

Shallow karst weathering in the Chalk

Deeper karst in the Chalk

 

Chapter 7 The future

Introduction

Types of camera log: the optical televiewer and the acoustic televiewer

Geophysical borehole wireline logs

Discussion

Conclusions

 

Appendix A Chalk weathering grades

Appendix B Describing flint sizes

Flint size

Flint type

Appendix C Typical Chalk core logs with examples of weathering and CIRIA grade

Typical Chalk core logs and examples of weathering

Example core sets from East London

Core preparation

Appendix D Cable percussion drilling: logging U100 Chalk samples

About the Author

Rory N. Mortimore is emeritus professor of engineering geology, University of Brighton, UK; visiting professor of engineering geology, University of Leeds, UK; and director, ChalkRock Limited, Lewes, Sussex, UK.

Subject Categories

BISAC Subject Codes/Headings:
SCI031000
SCIENCE / Earth Sciences / Geology
TEC009020
TECHNOLOGY & ENGINEERING / Civil / General