Contents

Contents

  Preface
1 The physics of magnetism
 1.1 What is a magnetic field?
 1.2 Magnetic moment
 1.3 Magnetic flux
 1.4 Magnetic energy
 1.5 Magnetization and magnetic susceptibility
 1.6 Relationship of B and H
 1.7 A brief tour of magnetic units in the cgs system
 1.8 The magnetic potential
 1.9 Origin of the geomagnetic field
 1.10 Problems
2 The geomagnetic field
 2.1 Components of magnetic vectors
 2.2 Reference magnetic field
 2.3 Geocentric axial dipole (GAD) and other poles
 2.4 Plotting magnetic directional data
  2.4.1 D,Itransformation
  2.4.2 Virtual geomagnetic poles
  2.4.3 Virtual dipole moment
 2.5 Problems
3 Induced and remanent magnetism
 3.1 Magnetism at the atomic level
 3.2 Induced magnetization
  3.2.1 Orbital contribution and diamagnetism
  3.2.2 Role of electronic spins and paramagnetism
 3.3 Ferromagnetism
 3.4 Problems
4 Magnetic anisotropy and domains
 4.1 The magnetic energy of particles
  4.1.1 Exchange energy
  4.1.2 Magnetic moments and external fields
  4.1.3 Magnetocrystalline anisotropy energy
  4.1.4 Magnetostriction - stress anisotropy
  4.1.5 Magnetostatic (shape) anisotropy
  4.1.6 Magnetic energy and magnetic stability
 4.2 Magnetic domains
 4.3 Thermal energy
 4.4 Putting it all together
 4.5 Problems
5 Magnetic hysteresis
 5.1 The “flipping” field
 5.2 Hysteresis loops
  5.2.1 Uniaxial anisotropy
  5.2.2 Magnetic susceptibility
  5.2.3 Cubic anisotropy
  5.2.4 Superparamagnetic particles
  5.2.5 Particles with domain walls
 5.3 Hysteresis of mixtures of SP, SD and MD grains
 5.4 First order reversal curves
 5.5 Problems
6 Magnetic mineralogy
 6.1 Iron-oxides
  6.1.1 Titanomagnetites Fe3-xTixO4
  6.1.2 Hematite-Ilmenite Fe2-yTiyO3
  6.1.3 Oxidation of (titano)magnetites to (titano)maghemites
 6.2 Iron-oxyhydroxides and iron-sulfides
 6.3 FeTi oxides in igneous rocks
 6.4 Magnetic mineralogy of soils and sediments
 6.5 Problems
7 How rocks get and stay magnetized
 7.1 The concept of dynamic equilibrium
 7.2 Essential N�el theory
 7.3 Viscous remanent magnetization
 7.4 Thermal remanent magnetization
 7.5 Chemical remanent magnetization
 7.6 Detrital remanent magnetization
  7.6.1 Physical alignment of magnetic moments in viscous fluids
  7.6.2 Post-depositional processes
  7.6.3 Inclination Error
 7.7 Isothermal remanent magnetization
 7.8 Thermo-viscous remanent magnetization
 7.9 Natural remanent magnetization
 7.10 Artificial remanences
 7.11 Problems
8 Applied rock (environmental) magnetism
 8.1 Images
 8.2 Critical temperatures
 8.3 Magnetic susceptibility
  8.3.1 Measurement of magnetic susceptibility
  8.3.2 Temperature dependence
  8.3.3 Frequency dependence
  8.3.4 Outcrop measurements
 8.4 Magnetization
  8.4.1 Magnetic interactions: IRM and ARM techniques
  8.4.2 IRM “unmixing”
  8.4.3 Combining thermal and isothermal information for rock magnetic characterization
 8.5 Hysteresis parameters
  8.5.1 The building blocks of hysteresis loops
  8.5.2 Hysteresis behavior of mixtures
 8.6 Trends in parameters with grain size
 8.7 Ratios
 8.8 Applications of rock magnetism
  8.8.1 Paleoclimatic information from lake sediments
  8.8.2 Paramagnetic contributions to magnetic susceptibility
  8.8.3 Separation of two superparamagnetic particle size distributions
  8.8.4 Identification of biogenic magnetite in natural samples
 8.9 Concluding remarks
 8.10 Problems
9 Getting a paleomagnetic direction
 9.1 Paleomagnetic sampling
  9.1.1 Types of samples
  9.1.2 Orientation in the field
  9.1.3 A note on terminology
 9.2 Measurement of magnetic remanence
 9.3 Changing coordinate systems
 9.4 Demagnetization techniques
 9.5 Estimating directions from demagnetization data
 9.6 Vector difference sum
 9.7 Best-fit lines and planes
 9.8 Field strategies
 9.9 Problems
10 Paleointensity
 10.1 Paleointensity with TRMs
  10.1.1 Stepwise heating family of experiments
  10.1.2 Reducing the effect of heating
  10.1.3 Quality assurance and data selection
 10.2 Paleointensity with DRMs
 10.3 Problems
11 Fisher statistics
 11.1 The normal distribution
 11.2 Statistics of vectors
  11.2.1 Estimation of Fisher statistics
  11.2.2 Some illustrations
 11.3 Significance Tests
  11.3.1 Watson’s test for randomness
  11.3.2 Comparison of precision
  11.3.3 Comparing known and estimated directions
  11.3.4 Comparing two estimated directions
  11.3.5 Combining directions and great circles
 11.4 Inclination only data
 11.5 Is a given data set Fisher distributed?
 11.6 Problems
12 Beyond Fisher statistics
 12.1 Non-Fisherian parametric approaches
  12.1.1 The Kent distribution
  12.1.2 The Bingham distribution
  12.1.3 The Bingham-LeGoff approximation
  12.1.4 The Bi-Gaussian distribution
 12.2 The simple (na�ve) bootstrap
 12.3 The parametric bootstrap
 12.4 When are two data sets distinct?
 12.5 Application to the “reversals test”
 12.6 Application to the “fold test”
 12.7 Problems
13 Paleomagnetic tensors
 13.1 Anisotropy of magnetic susceptibility
 13.2 Hext Statistics
  13.2.1 Hext confidence ellipses
  13.2.2 Hext F statistics for significance of eigenvalue ratios
 13.3 Limitations of Hext statistics
 13.4 Bootstrap confidence ellipses
 13.5 Comparing mean eigenvectors with other axes
 13.6 Shape
 13.7 Anisotropy of magnetic remanence
  13.7.1 Anisotropy of ARM and TRM
  13.7.2 Anisotropy of DRM
 13.8 Problems
14 The ancient geomagnetic field
 14.1 Historical measurements
 14.2 Archaeo- and paleomagnetic records
  14.2.1 Pioneers in paleomagnetism
  14.2.2 The last seven millenia
  14.2.3 Westward drift
  14.2.4 The more distant past
 14.3 Time series of paleomagnetic data
  14.3.1 Excursions
  14.3.2 Reversals
 14.4 Geomagnetic polarity time scale – a first look
 14.5 The time averaged field
 14.6 Long term changes in paleointensity
 14.7 Statistical models of paleosecular variation
 14.8 Problems
15 The GPTS and magnetostratigraphy
 15.1 Early efforts in defining the GPTS
  15.1.1 The addition of biostratigraphy
  15.1.2 Astrochronology
  15.1.3 A note on terminology
 15.2 Current status of the geological time scale
 15.3 Applications
  15.3.1 Dating geological sequences
  15.3.2 Measuring rates
  15.3.3 Tracing of magnetic isochrons
 15.4 Problems
16 Tectonic applications of paleomagnetism
 16.1 Essentials of plate tectonic theory
 16.2 Poles and apparent polar wander
 16.3 The Gondwana APWP
 16.4 Inclination shallowing and GAD
 16.5 Paleomagnetism and plate reconstructions
 16.6 Discordant poles and displaced terranes
 16.7 Inclination only data and APWPs
 16.8 Concluding remarks
 16.9 Problems
17 References
Appendices
A Definitions, derivations and tricks
 A.1 Definitions
 A.2 Derivations
  A.2.1 Langevin function for a paramagnetic substance
  A.2.2 Superparamagnetism
 A.3 Useful tricks
  A.3.1 Spherical trigonometry
  A.3.2 Vector addition
  A.3.3 Vector subtraction
  A.3.4 Vector multiplication
  A.3.5 Tricks with tensors
  A.3.6 Upside down triangles,
  A.3.7 The statistical bootstrap
  A.3.8 Directions using a sun compass
B Plots useful in paleomagnetism
 B.1 Equal area projections
  B.1.1 Calculation of an equal area projection
  B.1.2 Plotting directions
  B.1.3 Bedding-tilt corrections
  B.1.4 Reading ternary diagrams
  B.1.5 Quantile-Quantile plots
C Paleomagnetic statistics and parameter estimation
 C.1 Hysteresis Parameters
 C.2 Directional statistics
  C.2.1 Calculation of Watson’s V w
  C.2.2 Combining lines and planes
  C.2.3 Inclination only calculation
  C.2.4 Kent 95% confidence ellipse
  C.2.5 Bingham 95% confidence parameters
 C.3 Paleointensity statistics
D Anisotropy in paleomagnetism
 D.1 The 15 measurement protocol