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Early Cambrian renewal of the geodynamo and the origin of inner core structure

Author

Listed:
  • Tinghong Zhou

    (University of Rochester)

  • John A. Tarduno

    (University of Rochester
    University of Rochester
    University of Rochester)

  • Francis Nimmo

    (University of California)

  • Rory D. Cottrell

    (University of Rochester)

  • Richard K. Bono

    (Florida State University
    University of Liverpool)

  • Mauricio Ibanez-Mejia

    (University of Arizona)

  • Wentao Huang

    (Chinese Academy of Sciences)

  • Matt Hamilton

    (University of Oklahoma)

  • Kenneth Kodama

    (Lehigh University)

  • Aleksey V. Smirnov

    (Michigan Technological Univ.
    Michigan Technological Univ.)

  • Ben Crummins

    (University of Rochester
    ERM)

  • Frank Padgett

    (University of Rochester
    BAE Systems)

Abstract

Paleomagnetism can elucidate the origin of inner core structure by establishing when crystallization started. The salient signal is an ultralow field strength, associated with waning thermal energy to power the geodynamo from core-mantle heat flux, followed by a sharp intensity increase as new thermal and compositional sources of buoyancy become available once inner core nucleation (ICN) commences. Ultralow fields have been reported from Ediacaran (~565 Ma) rocks, but the transition to stronger strengths has been unclear. Herein, we present single crystal paleointensity results from early Cambrian (~532 Ma) anorthosites of Oklahoma. These yield a time-averaged dipole moment 5 times greater than that of the Ediacaran Period. This rapid renewal of the field, together with data defining ultralow strengths, constrains ICN to ~550 Ma. Thermal modeling using this onset age suggests the inner core had grown to 50% of its current radius, where seismic anisotropy changes, by ~450 Ma. We propose the seismic anisotropy of the outermost inner core reflects development of a global spherical harmonic degree-2 deep mantle structure at this time that has persisted to the present day. The imprint of an older degree-1 pattern is preserved in the innermost inner core.

Suggested Citation

  • Tinghong Zhou & John A. Tarduno & Francis Nimmo & Rory D. Cottrell & Richard K. Bono & Mauricio Ibanez-Mejia & Wentao Huang & Matt Hamilton & Kenneth Kodama & Aleksey V. Smirnov & Ben Crummins & Frank, 2022. "Early Cambrian renewal of the geodynamo and the origin of inner core structure," Nature Communications, Nature, vol. 13(1), pages 1-7, December.
    • Handle: RePEc:nat:natcom:v:13:y:2022:i:1:d:10.1038_s41467-022-31677-7
    DOI: 10.1038/s41467-022-31677-7
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    References listed on IDEAS

    as
    1. N. Flament & S. Williams & R. D. Müller & M. Gurnis & D. J. Bower, 2017. "Origin and evolution of the deep thermochemical structure beneath Eurasia," Nature Communications, Nature, vol. 8(1), pages 1-9, April.
    2. Gary A. Glatzmaier & Robert S. Coe & Lionel Hongre & Paul H. Roberts, 1999. "The role of the Earth's mantle in controlling the frequency of geomagnetic reversals," Nature, Nature, vol. 401(6756), pages 885-890, October.
    3. Fenglin Niu & Lianxing Wen, 2001. "Hemispherical variations in seismic velocity at the top of the Earth's inner core," Nature, Nature, vol. 410(6832), pages 1081-1084, April.
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    Cited by:

    1. Lauren Waszek & Jessica Irving & Thanh-Son Phạm & Hrvoje Tkalčić, 2023. "Seismic insights into Earth’s core," Nature Communications, Nature, vol. 14(1), pages 1-3, December.
    2. Yong-Xiang Li & John A. Tarduno & Wenjun Jiao & Xinyu Liu & Shanchi Peng & Shihua Xu & Aihua Yang & Zhenyu Yang, 2023. "Late Cambrian geomagnetic instability after the onset of inner core nucleation," Nature Communications, Nature, vol. 14(1), pages 1-8, December.

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