The Intensity of the Ancient Geomagnetic Field: A Review and Analysis

Summary In this review all palaeomagnetic determinations of the intensity of the ancient geomagnetic field known to the author at 1966 June are brought together and analysed. The lists of data cover determinations from both historic (archaeomagnetic) and geological specimens. The problems encountered in the determination of ancient field intensities from rocks, especially that of rock alteration during the formation of artificial remanence and that of the presence of secondary components of magnetization, are discussed, and methods used to overcome them are described. Experimental techniques used hitherto are briefly summarized. Methods of treating data are reviewed; and suggestions for comparing data from different latitudes are made. The main conclusions drawn from an analysis of both the field intensity data and the problems involved in obtaining this data are: (i) that the problem of rock alteration during the heating necessary to induce an artificial TRM may be overcome by heating selected naturally highly-oxidized specimens in air; (ii) that the effects of secondary components of magnetization may be avoided by utilizing that part of the primary moment which remains after the removal of secondary moments by thermal or a.c. demagnetization; (iii) that the geomagnetic dipole is not constant within any given polarity but fluctuates in strength, possibly with a period of the order of lo4 years; (iv) that because of these fluctuations and non-dipole field variations no conclusions regarding the mean strength of the geomagnetic dipole at any given time may be made if only a few rock samples are measured, and hence that future workers should use sufficient samples to average out these effects; (v) that the limited data from transition zones suggest that during a field reversal the dipole moment reduces to zero but the non-dipole field remains.

[1]  N. Watkins,et al.  Correlation of Petrology and Natural Magnetic Polarity in Columbia Plateau Basalts , 1967 .

[2]  PETER J. Smith The Intensity of the Tertiary Geomagnetic Field , 1967 .

[3]  J. Briden Estimates of Direction and Intensity of the Palaeomagnetic Field from the Mugga Mugga Porphyry, Australia , 1966 .

[4]  R. Wilson Palaeomagnetism and rock magnetism , 1966 .

[5]  M. Lewis,et al.  Reversed Partial Thermo-Magnetic Remanence in Natural and Synthetic Titano-Magnetites , 1965 .

[6]  E. Irving,et al.  Magnetism in Heard Island rocks , 1965 .

[7]  P. Smith,et al.  The Petrology, Curie Points and Natural Magnetizations of Basic Lavas , 1965 .

[8]  R. Doell,et al.  Long period variations of the geomagnetic field , 1964 .

[9]  E. Irving,et al.  A statistical model of the geomagnetic field , 1964 .

[10]  K. Momose studies on the variations of the earth's magnetic field during Pliocence time , 1963 .

[11]  T. Nagata,et al.  Secular Variation of the Geomagnetic Total Force during the Last 5000 Years , 1963 .

[12]  D. W. Powell Significance of Differences in Magnetization Along Certain Dolerite Dykes , 1963, Nature.

[13]  I. Mcdougall Potassium-argon age measurements on dolerites from Antarctica and South Africa , 1963 .

[14]  A. L. Hales,et al.  The Palaeomagnetism of the Stormberg Lavas, II. The Behaviour of the Magnetic Field During a Reversal , 1962 .

[15]  D. W. Allan,et al.  On the behaviour of systems of coupled dynamos , 1962, Mathematical Proceedings of the Cambridge Philosophical Society.

[16]  Takesi Yukutake,et al.  The Westward Drift of the Magnetic Field of the Earth , 1962 .

[17]  K. Creer The dispersion of the geomagnetic field due to secular variation and its determination for remote times from paleomagnetic data , 1962 .

[18]  A. Cox Analysis of Present Geomagnetic Field for Comparison with Paleomagnetic Results , 1962 .

[19]  T. Yukutake 14. Archaeomagnetic Study on Volcanic Rocks in Oshima Island, Japan , 1961 .

[20]  R. Wilson The Thermal Demagnetization of Natural Magnetic Moments in Rocks , 1961 .

[21]  P. A. Sheppard Handbook of Geophysics , 1960 .

[22]  P. Blackett,et al.  An analysis of rock magnetic data , 1960, Proceedings of the Royal Society of London. Series A. Mathematical and Physical Sciences.

[23]  R. Doell,et al.  REVIEW OF PALEOMAGNETISM , 1960 .

[24]  S. Runcorn Statistical methods in rock magnetism , 1960 .

[25]  I. Kushiro,et al.  Natural Occurrence of Titanomaghemite and Its Relevance to the Unstable Magnetization of Rocks , 1960 .

[26]  E. Irving Palaeomagnetic Pole Positions, Part I. , 1960 .

[27]  S. Runcorn On the hypothesis that the mean geomagnetic field for parts of geological time has been that of a geocentric axial multipole , 1959 .

[28]  Naotune Watanabe Secular Variation in the Direction of Geomagnetism as the Standard Scale for Geomagnetochronology in Japan , 1958, Nature.

[29]  D. W. ALLAN,et al.  Reversals of the Earth's Magnetic Field , 1958, Nature.

[30]  T. Rikitake,et al.  Oscillations of a system of disk dynamos , 1958, Mathematical Proceedings of the Cambridge Philosophical Society.

[31]  H. F. Finch,et al.  The Earth's Main Magnetic Field—Epoch 1955.0 , 1957 .

[32]  W. Elsasser Hydromagnetism. II. A Review , 1956 .

[33]  R. King THE REMANENT MAGNETISM OF ARTIFICIALLY DEPOSITED SEDIMENTS , 1955 .

[34]  Edward Bullard,et al.  The stability of a homopolar dynamo , 1955, Mathematical Proceedings of the Cambridge Philosophical Society.

[35]  J. Clegg,et al.  LXVI. The remanent magnetism of some sedimentary rocks in Britain , 1954 .

[36]  R. Fisher Dispersion on a sphere , 1953, Proceedings of the Royal Society of London. Series A. Mathematical and Physical Sciences.

[37]  F. Lowes,et al.  The analysis of the geomagnetic secular variation , 1951, Philosophical Transactions of the Royal Society of London. Series A, Mathematical and Physical Sciences.

[38]  Edward Bullard,et al.  The westward drift of the Earth's magnetic field , 1950, Philosophical Transactions of the Royal Society of London. Series A, Mathematical and Physical Sciences.

[39]  E. Johnson,et al.  Pre‐history of the Earth's magnetic field , 1948 .

[40]  Takesi Nagata,et al.  1. The Natural Remanent Magnetism of Volcanic Racks and Its Relation to Geomagnetic Phenomena , 1943 .

[41]  J. Koenigsberger Natural residual magnetism of eruptive rocks , 1938 .

[42]  R. Chevallier L’aimantation des laves de l’Etna et l’orientation du champ terrestre en Sicile du XIIe au XVIIe siècle , 1925 .

[43]  Henry. Gellibrand A discourse mathematical on the variation of the magneticall needle , 1969 .

[44]  S. Malin,et al.  An Analytical Representation of the Estimated Geomagnetic Field and its Secular Change for the Epoch 1965.0 , 1965 .

[45]  S. Sasajima Geomagnetic Secular Variation Revealed in the Baked Earths in West Japan (part 2) Change of the Field Intensity , 1965 .

[46]  N. Kawai,et al.  Counterclockwise Rotation of the Geomagnetic Dipole Axis Revealed in the World-Wide Archaeo-Secular Variations , 1965 .

[47]  E. J. Schwarz,et al.  Archeomagnetic Intensity Studies of South and Central America , 1965 .

[48]  S. P. Burlatskaya Archeomagnetic Evidence for the Earth's Magnetic Field near Tiflis during the Past , 1961 .

[49]  A. Holmes A Revised Geological Time-Scale , 1960, Nature.

[50]  T. Katsura,et al.  Magneto-Chemical Study of the Generalized Titanomagnetite in Volcanic Rocks , 1959 .

[51]  E. Thellier,et al.  Sur l'intensite du champ magnetique terrestre dans le passe historique et geologique , 1959 .

[52]  S. McEnroe,et al.  Remanent Magnetism , 1958, Nature.

[53]  T. Katsura,et al.  Magnetic Properties of TiFe2O4-Fe3O4 System and Their Change with Oxidation , 1957 .

[54]  S. Uyeda,et al.  Reverse Magnetization of Rocks and Its Connection with the Geomagnetic Field , 1954 .

[55]  Constantino Galbar-Puertas Variacion secular del campo geomagnetico , 1953 .