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Possible links between long-term geomagnetic variations and whole-mantle convection processes

A Corrigendum to this article was published on 29 July 2012

Abstract

The Earth's internal magnetic field varies on timescales of months to billions of years. The field is generated by convection in the liquid outer core, which in turn is influenced by the heat flowing from the core into the base of the overlying mantle. Much of the magnetic field's variation is thought to be stochastic, but over very long timescales, this variability may be related to changes in heat flow associated with mantle convection processes. Over the past 500 Myr, correlations between palaeomagnetic behaviour and surface processes were particularly striking during the middle to late Mesozoic era, beginning about 180 Myr ago. Simulations of the geodynamo suggest that transitions from periods of rapid polarity reversals to periods of prolonged stability — such as occurred between the Middle Jurassic and Middle Cretaceous periods — may have been triggered by a decrease in core–mantle boundary heat flow either globally or in equatorial regions. This decrease in heat flow could have been linked to reduced mantle-plume-head production at the core–mantle boundary, an episode of true polar wander, or a combination of the two.

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Figure 1: Records of geomagnetic polarity reversal frequency and dipole moment since the Cambrian period.
Figure 2: Representative cases of a mantle flow model showing the effects of subducted slabs on core–mantle boundary (CMB) heat flow.
Figure 3: Average reversal frequency and eruption ages20 of large igneous provinces (LIPs; offset by +50 Myr) that have not yet been subducted.
Figure 4: True polar wander (TPW) as produced by a mantle flow model (case 2) subject to two major perturbations in subduction flux which affected the fractional CMB heat flow in the equatorial region.
Figure 5: Analysis of possible effects of observed TPW on equatorial CMB heat flow (and hence reversal frequency).

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References

  1. Jonkers, A. R. T. Discrete scale invariance connects geodynamo timescales. Geophys. J. Int. 171, 581–593 (2007).

    Google Scholar 

  2. Hulot, G. & Gallet, Y. Do superchrons occur without any palaeomagnetic warning? Earth Planet. Sci. Lett. 210, 191–201 (2003).

    Google Scholar 

  3. Jonkers, A. R. T. Long-range dependence in the Cenozoic reversal record. Phys. Earth Planet. Inter. 135, 253–266 (2003).

    Google Scholar 

  4. Jones, G. M. Thermal interaction of the core and the mantle and long-term behavior of the geomagnetic field. J. Geophys Res 82, 1703–1709 (1977).

    Google Scholar 

  5. Mcfadden, P. L. & Merrill, R. T. Lower mantle convection and geomagnetism. J. Geophys. Res. 89, 3354–3362 (1984).

    Google Scholar 

  6. Biggin, A. J. & Thomas, D. N. Analysis of long-term variations in the geomagnetic poloidal field intensity and evaluation of their relationship with global geodynamics. Geophys. J. Int. 152, 392–415 (2003).

    Google Scholar 

  7. Courtillot, V. & Besse, J. Magnetic-field reversals, polar wander, and core-mantle coupling. Science 237, 1140–1147 (1987).

    Google Scholar 

  8. Courtillot, V. & Olson, P. Mantle plumes link magnetic superchrons to Phanerozoic mass depletion events. Earth Planet. Sci. Lett. 260, 495–504 (2007).

    Google Scholar 

  9. Eide, E. A. & Torsvik, T. H. Paleozoic supercontinental assembly, mantle flushing, and genesis of the Kiaman Superchron. Earth Planet. Sci. Lett. 144, 389–402 (1996).

    Google Scholar 

  10. Gaffin, S. Phase difference between sea-level and magnetic reversal rate. Nature 329, 816–819 (1987).

    Google Scholar 

  11. Haggerty, S. E. Superkimberlites — a geodynamic diamond window to the earths core. Earth Planet. Sci. Lett. 122, 57–69 (1994).

    Google Scholar 

  12. Larson, R. L. & Kincaid, C. Onset of mid-Cretaceous volcanism by elevation of the 670 km thermal boundary layer. Geology 24, 551–554 (1996).

    Google Scholar 

  13. Larson, R. L. & Olson, P. Mantle plumes control magnetic reversal frequency. Earth Planet. Sci. Lett. 107, 437–447 (1991).

    Google Scholar 

  14. Pétrélis, F., Besse, J. & Valet, J.-P. Plate tectonics may control geomagnetic reversal frequency. Geophys. Res. Lett. 38, L19303 (2011).

    Google Scholar 

  15. Zhang, N. & Zhong, S. J. Heat fluxes at the Earth's surface and core-mantle boundary since Pangea formation and their implications for the geomagnetic superchrons. Earth Planet. Sci. Lett. 306, 205–216 (2011).

    Google Scholar 

  16. Ricou, L. E. & Gibert, D. The magnetic reversal sequence studied using wavelet analysis: a record of the Earth's tectonic history at the core-mantle boundary. CR Acad. Sci. II A 325, 753–759 (1997).

    Google Scholar 

  17. Vogt, P. R. Evidence for global synchronism in mantle plume convection, and possible significance for geology. Nature 240, 338–342 (1972).

    Google Scholar 

  18. Jones, G. M. Thermal interaction of core and mantle and long-term behavior of geomagnetic-field. J. Geophys. Res. 82, 1703–1709 (1977).

    Google Scholar 

  19. Loper, D. E. & Mccartney, K. Mantle plumes and the periodicity of magnetic-field reversals. Geophys. Res. Lett. 13, 1525–1528 (1986).

    Google Scholar 

  20. Torsvik, T. H., Burke, K., Steinberger, B., Webb, S. J. & Ashwal, L. D. Diamonds sampled by plumes from the core-mantle boundary. Nature 466, 352–355 (2010).

    Google Scholar 

  21. Van der Meer, D. G., Spakman, W., van Hinsbergen, D. J. J., Amaru, M. L. & Torsvik, T. H. Towards absolute plate motions constrained by lower-mantle slab remnants. Nature Geosci. 3, 36–40 (2010).

    Google Scholar 

  22. Constable, C. G. Modelling the geomagnetic field from syntheses of paleomagnetic data. Phys. Earth Planet. Inter. 187, 109–117 (2011).

    Google Scholar 

  23. Korte, M. & Holme, R. On the persistence of geomagnetic flux lobes in global Holocene field models. Phys. Earth Planet. Inter. 182, 179–186 (2010).

    Google Scholar 

  24. Hoffman, K. A. & Singer, B. S. Magnetic source separation in Earth's outer core. Science 321, 1800–1800 (2008).

    Google Scholar 

  25. Christensen, U. R. Geodynamo models: Tools for understanding properties of Earth's magnetic field. Phys. Earth Planet. Inter. 187, 157–169 (2011).

    Google Scholar 

  26. Kutzner, C. & Christensen, U. R. Simulated geomagnetic reversals and preferred virtual geomagnetic pole paths. Geophys. J. Int. 157, 1105–1118 (2004).

    Google Scholar 

  27. Buffett, B. A. in Core Dynamics Vol. 8 Treatise on Geophysics (ed. Olson, P.) Ch. 12, 345–358 (Elsevier, 2007).

    Google Scholar 

  28. Cande, S. C. & Kent, D. V. Revised calibration of the geomagnetic polarity timescale for the Late Cretaceous and Cenozoic. J. Geophys. Res.-Sol. Ea. 100, 6093–6095 (1995).

    Google Scholar 

  29. Tominaga, M., Sager, W. W., Tivey, M. A. & Lee, S. M. Deep-tow magnetic anomaly study of the Pacific Jurassic Quiet Zone and implications for the geomagnetic polarity reversal timescale and geomagnetic field behavior. J. Geophys. Res.-Sol. Ea. 113, B07110 (2008).

    Google Scholar 

  30. Sager, W. W., Weiss, C. J., Tivey, M. A. & Johnson, H. P. Geomagnetic polarity reversal model of deep-tow profiles from the Pacific Jurassic Quiet Zone. J. Geophys. Res.-Sol. Ea. 103, 5269–5286 (1998).

    Google Scholar 

  31. Tominaga, M. & Sager, W. W. Revised Pacific M-anomaly geomagnetic polarity timescale. Geophys. J. Int. 182, 203–232 (2010).

    Google Scholar 

  32. Gradstein, F. M., Ogg, J. G. & Smith, A. G. A Geologic Time Scale 2004 589 (Cambridge Univ. Press, 2004).

    Google Scholar 

  33. Ogg, J. G. in A Geological Time Scale 2004 (eds Gradstein, F. M., Ogg, J. G. & Smith, A. G.) 307–339 (Cambridge Univ. Press, 2004).

    Google Scholar 

  34. Ogg, J. G., Coe, A. L., Przybylski, P. A. & Wright, J. K. Oxfordian magnetostratigraphy of Britain and its correlation to Tethyan regions and Pacific marine magnetic anomalies. Earth Planet. Sci. Lett. 289, 433–448 (2010).

    Google Scholar 

  35. Gee, J. S. & Kent, D. V. in Geomagnetism Vol. 5 Treatise on Geophysics (ed. Kono, M.) Ch. 12, 455–507 (Elsevier, 2007).

    Google Scholar 

  36. He, H., Pan, Y., Tauxe, L., Qin, H. & Zhu, R. Toward age determination of the M0r (Barremian–Aptian boundary) of the early Cretaceous. Phys. Earth Planet. Inter. 169, 41–48 (2008).

    Google Scholar 

  37. Granot, R., Tauxe, L., Gee, J. S. & Ron, H. A view into the Cretaceous geomagnetic field from analysis of gabbros and submarine glasses. Earth Planet. Sci. Lett. 256, 1–11 (2007).

    Google Scholar 

  38. Tauxe, L. & Yamazaki, T. in Geomagnetism Vol. 5 Treatise on Geophysics (ed Kono, M.) Ch. 13, 510–563 (Elsevier, 2007).

    Google Scholar 

  39. Qin, H., He, H., Liu, Q. & Cai, S. Palaeointensity just at the onset of the Cretaceous normal superchron. Phys. Earth Planet. Inter. 187, 199–211 (2011).

    Google Scholar 

  40. Tarduno, J. A. & Smirnov, A. V. in Timescales of the Paleomagnetic Field Vol. 145 Geophys. Monogr. Series (eds Channell, J. E. T., Kent, D. V., Lowrie, W. & Meert, J. G.) 328 (AGU, 2004).

    Google Scholar 

  41. Granot, R., Dyment, J. & Gallet, Y. Geomagnetic field variability during the Cretaceous Normal Superchron. Nature Geosci. 5, 220–223 (2012).

    Google Scholar 

  42. Prévot, M., Derder, M. E., Mcwilliams, M. & Thompson, J. Intensity of the Earths magnetic-field — evidence for a Mesozoic dipole low. Earth Planet. Sci. Lett. 97, 129–139 (1990).

    Google Scholar 

  43. Valet, J. P. Time variations in geomagnetic intensity. Rev. Geophys 41, 1004 (2003).

    Google Scholar 

  44. Perrin, M. & Shcherbakov, V. Paleointensity of the earth's magnetic field for the past 400 Ma: Evidence for a dipole structure during the Mesozoic Low. J. Geomagn. Geoelectr. 49, 601–614 (1997).

    Google Scholar 

  45. Tarduno, J. A. & Cottrell, R. D. Dipole strength and variation of the time-averaged reversing and nonreversing geodynamo based on Thellier analyses of single plagioclase crystals. J. Geophys. Res. B-Sol. Earth 110, 1–10 (2005).

    Google Scholar 

  46. McElhinny, M. W. & Larson, R. L. Jurassic dipole low defined from land and sea data. Eos Trans. AGU 84, 362 (2003).

    Google Scholar 

  47. Biggin, A. J., van Hinsbergen, D., Langereis, C. G. G. B., S., & Deenen, M. H. L. Geomagnetic secular variation in the Cretaceous Normal Superchron and in the Jurassic. Phys. Earth Planet. Inter. 169, 3–19 (2008).

    Google Scholar 

  48. McFadden, P. L. & Merrill, R. T. Evolution of the geomagnetic reversal rate since 160 Ma: Is the process continuous? J. Geophys. Res.-Sol. Ea. 105, 28455–28460 (2000).

    Google Scholar 

  49. Langereis, C. G., Krijgsman, W., Muttoni, G. & Menning, M. Magnetostratigraphy — concepts, definitions, and applications. Newslett Stratigr. 43, 207–233 (2010).

    Google Scholar 

  50. Pavlov, V. & Gallet, Y. A third superchron during the Early Paleozoic. Episodes 28, 78–84 (2005).

    Google Scholar 

  51. Pavlov, V. & Gallet, Y. Middle Cambrian high magnetic reversal frequency (Kulumbe River section, northwestern Siberia) and reversal behaviour during the Early Palaeozoic. Earth Planet. Sci. Lett. 185, 173–183 (2001).

    Google Scholar 

  52. Kouchinsky, A. et al. The SPICE carbon isotope excursion in Siberia: a combined study of the upper Middle Cambrian-lowermost Ordovician Kulyumbe River section, northwestern Siberian Platform. Geol. Mag. 145, 609–622 (2008).

    Google Scholar 

  53. Pavlov, V. & Gallet, Y. Variations in geomagnetic reversal frequency during the Earth's middle age. Geochem. Geophys. Geosys. 11, Q01Z10 (2010).

    Google Scholar 

  54. Aubert, J., Labrosse, S. & Poitou, C. Modelling the palaeo-evolution of the geodynamo. Geophys. J. Int. 179, 1414–1428 (2009).

    Google Scholar 

  55. Driscoll, P. & Olson, P. Effects of buoyancy and rotation on the polarity reversal frequency of gravitationally driven numerical dynamos. Geophys. J. Int. 178, 1337–1350 (2009).

    Google Scholar 

  56. Driscoll, P. & Olson, P. Superchron cycles driven by variable core heat flow. Geophys. Res. Lett. 38, L09304 (2011).

    Google Scholar 

  57. Olson, P. Gravitational dynamos and the low-frequency geomagnetic secular variation. Proc. Natl Acad. Sci. USA 105, 20159–20166 (2007).

    Google Scholar 

  58. Wicht, J., Stellmach, S. & Harder, H. in Handbook of Geomathematics (eds Freeden, W., Nashed, M. Z. & Sonar, T.) (Springer, 2010).

    Google Scholar 

  59. Olson, P. & Christensen, U. R. Dipole moment scaling for convection-driven planetary dynamos. Earth Planet. Sci. Lett. 250, 561–571 (2006).

    Google Scholar 

  60. Pozzo, M., Davies, C., Gubbins, D. & Alfè, D. Thermal and electrical conductivity of iron at Earth's core conditions. Nature 485, 355–358 (2012).

    Google Scholar 

  61. Christensen, U. R. & Aubert, J. Scaling properties of convection-driven dynamos in rotating spherical shells and application to planetary magnetic fields. Geophys. J. Int. 166, 97–114 (2006).

    Google Scholar 

  62. Glatzmaier, G. A., Coe, R. S., Hongre, L. & Roberts, P. H. The role of the Earth's mantle in controlling the frequency of geomagnetic reversals. Nature 401, 885–890 (1999).

    Google Scholar 

  63. Olson, P. L., Coe, R. S., Driscoll, P. E., Glatzmaier, G. A. & Roberts, P. H. Geodynamo reversal frequency and heterogeneous core-mantle boundary heat flow. Phys. Earth Planet. Inter. 180, 66–79 (2010).

    Google Scholar 

  64. Pétrélis, F., Fauve, S., Dormy, E. & Valet, J. P. Simple mechanism for reversals of Earth's magnetic field. Phys. Rev. Lett. 102, 144503 (2009).

    Google Scholar 

  65. Wicht, J., Stellmach, S. & Harder, H. in Geomagnetic field variations — Space–time structure, processes, and effects on system Earth. (eds Glassmeier, K. H., Soffel, H. & Negendank, J.) 107–158 (Springer, 2009).

    Google Scholar 

  66. Lay, T., Hernlund, J. & Buffett, B. A. Core-mantle boundary heat flow. Nature Geosci. 1, 25–32 (2008).

    Google Scholar 

  67. Van der Hilst, R. D. et al. Seismostratigraphy and thermal structure of Earth's core-mantle boundary region. Science 315, 1813–1817 (2007).

    Google Scholar 

  68. Garnero, E. J., Lay, T. & McNamara, A. in Plates, plumes, and planetary processes Vol. 430 Geol. Soc. Am. Special Paper (eds Foulger, G. R. & Jurdy, D. M.) 79–101 (2007).

    Google Scholar 

  69. Machetel, P. & Thomassot, E. Cretaceous length of day perturbation by mantle avalanche. Earth Planet. Sci. Lett. 202, 379–386 (2002).

    Google Scholar 

  70. Fukao, Y., Widiyantoro, S. & Obayashi, M. Stagnant slabs in the upper and lower mantle transition region. Rev. Geophys. 39, 291–323 (2001).

    Google Scholar 

  71. Van der Voo, R., Spakman, W. & Bijwaard, H. Mesozoic subducted slabs under Siberia. Nature 397, 246–249 (1999).

    Google Scholar 

  72. Van der Hilst, R. D., Widiyantoro, S. & Engdahl, E. R. Evidence for deep mantle circulation from global tomography. Nature 386, 578–584 (1997).

    Google Scholar 

  73. Grand, S. P., Van der Hilst, R. D. & Widiyantoro, S. Global seismic tomography: A snapshot of convection in the Earth. GSA Today 7, 1–7 (1997).

    Google Scholar 

  74. Goes, S., Capitanio, F. A. & Morra, G. Evidence of lower-mantle slab penetration phases in plate motions. Nature 451, 981–984 (2008).

    Google Scholar 

  75. Steinberger, B. M. & Torsvik, T. H. A geodynamic model of plumes from the margins of large low shear velocity provinces. Geochem. Geophys. Geosys. 13, Q01W09 (2012).

    Google Scholar 

  76. Čížková, H., van den Berg, A. P., Spakman, W. & Matyska, C. The viscosity of Earth´s lower mantle inferred from sinking speed of subducted lithosphere. Phys. Earth Planet. Inter. http://dx.doi.org/10.1016/j.pepi.2012.1002.1010 (in the press).

  77. Labrosse, S. Hotspots, mantle plumes and core heat loss. Earth Planet. Sci. Lett. 199, 147–156 (2002).

    Google Scholar 

  78. Gonnermann, H. M., Jellinek, A. M., Richards, M. A. & Manga, M. Modulation of mantle plumes and heat flow at the core mantle boundary by plate-scale flow: results from laboratory experiments. Earth Planet. Sci. Lett. 226, 53–67 (2004).

    Google Scholar 

  79. Nakagawa, T. & Tackley, P. J. Deep mantle heat flow and thermal evolution of the Earth's core in thermochemical multiphase models of mantle convection. Geochem. Geophys. Geosys. 6, Q08003 (2005).

    Google Scholar 

  80. Thorne, M. S., Garnero, E. J. & Grand, S. P. Geographic correlation between hot spots and deep mantle lateral shear-wave velocity gradients. Phys. Earth Planet. Inter. 146, 47–63 (2004).

    Google Scholar 

  81. Tan, E., Leng, W., Zhong, S. J. & Gurnis, M. On the location of plumes and lateral movement of thermochemical structures with high bulk modulus in the 3-D compressible mantle. Geochem. Geophys. Geosys. 12, Q07005 (2011).

    Google Scholar 

  82. Burke, K., Steinberger, B., Torsvik, T. H. & Smethurst, M. A. Plume generation zones at the margins of large low shear velocity provinces on the core-mantle boundary. Earth Planet. Sici. Lett. 265, 49–60 (2008).

    Google Scholar 

  83. Burke, K. Plate tectonics, the Wilson Cycle, and mantle plumes: geodynamics from the top. Annu. Rev. Earth Planet. Sci. 39, 1–29 (2011).

    Google Scholar 

  84. Larson, R. L. Latest pulse of Earth — evidence for a midcretaceous superplume. Geology 19, 547–550 (1991).

    Google Scholar 

  85. Bryan, S. E. & Ernst, R. E. Revised definition of large igneous provinces (LIPs). Earth-Sci. Rev. 86, 175–202 (2008).

    Google Scholar 

  86. Olson, P., Schubert, G. & Anderson, C. Plume formation in the D-layer and the roughness of the core mantle boundary. Nature 327, 409–413 (1987).

    Google Scholar 

  87. Thompson, P. F. & Tackley, P. J. Generation of mega-plumes from the core-mantle boundary in a compressible mantle with temperature-dependent viscosity. Geophys. Res. Lett. 25, 1999–2002 (1998).

    Google Scholar 

  88. Van Hinsbergen, D. J. J., Steinberger, B., Doubrovine, P. V. & Gassmoller, R. Acceleration and deceleration of India-Asia convergence since the Cretaceous: Roles of mantle plumes and continental collision. J. Geophys. Res.-Sol. Ea. 116, B06101 (2011).

    Google Scholar 

  89. Gold, T. Instability of the Earths axis of rotation. Nature 175, 526–529 (1955).

    Google Scholar 

  90. Steinberger, B. & Torsvik, T. H. Toward an explanation for the present and past locations of the poles. Geochem. Geophys. Geosys. 11, Q06W06 (2010).

    Google Scholar 

  91. Tsai, V. C. & Stevenson, D. J. Theoretical constraints on true polar wander. J. Geophys. Res.-Sol. Ea. 112, B05415 (2007).

    Google Scholar 

  92. Steinberger, B. & Torsvik, T. H. Absolute plate motions and true polar wander in the absence of hotspot tracks. Nature 452, 620–626 (2008).

    Google Scholar 

  93. Mitchell, R. N., Kilian, T. M. & Evans, D. A. D. Supercontinent cycles and the calculation of absolute palaeolongitude in deep time. Nature 482, 208–296 (2012).

    Google Scholar 

  94. Torsvik, T. H. et al. Phanerozoic polar wander, paleogeography and dynamics. Earth-Sci. Rev. http://dx.doi.org/10.1016/j.earscirev.2012.06.007 (2012).

  95. Becker, T. W. & Boschi, L. A comparison of tomographic and geodynamic mantle models. Geochem. Geophys. Geosys. 3, 1003 (2002).

    Google Scholar 

  96. Tan, E., Gurnis, M. & Han, L. J. Slabs in the lower mantle and their modulation of plume formation. Geochem. Geophys. Geosys. 3, 1067 (2002).

    Google Scholar 

  97. Biggin, A., McCormack, A. & Roberts, A. Paleointensity database updated and upgraded. Eos Trans. AGU 91, 15 (2010).

    Google Scholar 

  98. Thellier, E. & Thellier, O. Sur l'intensité du champ magnétique terrestre dans la passé historique et géologique. Ann. Géophys. 15, 285–376 (1959).

    Google Scholar 

  99. Hill, M. J. & Shaw, J. Magnetic field intensity study of the 1960 Kilauea lava flow, Hawaii, using the microwave palaeointensity technique. Geophys. J. Int. 142, 487–504 (2000).

    Google Scholar 

  100. Yamamoto, Y., Tsunakawa, H. & Shibuya, H. Palaeointensity study of the Hawaiian 1960 lava: implications for possible causes of erroneously high intensities. Geophys. J. Int. 153, 263–276 (2003).

    Google Scholar 

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Acknowledgements

A.J.B. is funded by a NERC Advanced Fellowship (NE/F015208/1). N.S., A.J.B. and R.H. are funded by a NERC standard grant (NE/H021043/1). A.J.B. acknowledges valuable discussions with Neil Thomas and Mimi Hill. J.A. acknowledges support from program PNP/SEDI-TPS of French Instutut National des Sciences de l'Univers (INSU). T.H.T. acknowledges the European Research Council for financial support.

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A.J.B., B.S. and J.A. prepared the text with contributions from all other authors. B.S. supplied the mantle modelling results. New analyses were performed by A.J.B and B.S. All authors contributed to discussions about the ideas presented.

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Correspondence to A. J. Biggin.

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Biggin, A., Steinberger, B., Aubert, J. et al. Possible links between long-term geomagnetic variations and whole-mantle convection processes. Nature Geosci 5, 526–533 (2012). https://doi.org/10.1038/ngeo1521

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