Logging the Chalk
Published on 31. May 2014
Book
Hardback
352 pages
978-1-4822-4671-1 (ISBN)
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.
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.
More details
Language
English
Place of publication
Oakville
Canada
Target group
College/higher education
Professional and scholarly
Dimensions
Height: 229 mm
Width: 152 mm
Weight
1542 gr
ISBN-13
978-1-4822-4671-1 (9781482246711)
Copyright in bibliographic data and cover images is held by Nielsen Book Services Limited or by the publishers or by their respective licensors: all rights reserved.
Schweitzer Classification
Person
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.
Content
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
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