EGU General Assembly 2022
© Author(s) 2023. This work is distributed under
the Creative Commons Attribution 4.0 License.

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

Tinghong Zhou1, John Tarduno1,2,3, Rory Cottrell1, and Francis Nimmo4
Tinghong Zhou et al.
  • 1University of Rochester, Earth and Environmental Sciences, Rochester, New York, United States of America (
  • 2University of Rochester, Physics and Astronomy, Rochester, New York, United States of America
  • 3Laboratory for Laser Energetics, University of Rochester, Rochester, New York, United States of America
  • 4University of California, Santa Cruz, Earth & Planetary Sciences, Santa Cruz, California, United States of America

Seismic anisotropy observations indicate the presence of an innermost and outermost inner core, but the origin of this structure is unknown. Records of the past geomagnetic field provide a means to probe inner core evolution by establishing when growth started. The Ediacaran (~565 million-year-old) geodynamo was near collapse, with a strength 10 times weaker than that of the present-day consistent with model predictions for the field before the onset of inner core nucleation. But the timing of the key transition to stronger intensities typical of the Phanerozoic Eon, needed for establishing an exact onset age, has been unclear. We present single crystal paleointensity results from anorthosites of the early Cambrian (~532 million-year-old) Glen Mountains Layered Mafic Complex (Oklahoma). Data from single plagioclase crystals bearing single domain magnetite and titanomagnetite inclusions yield a time-averaged dipole moment of 3.5 +/- 0.9 x 1022 A m2, 5 times greater than that recorded in the Ediacaran Period. This rapid field recovery is the expectation at the start of inner core growth, as new thermal and compositional sources of buoyancy to power the geodynamo become available. We will discuss thermal models, which together with our new paleointensity results, allow us to constrain growth of the inner core and when its structure may have changed.

How to cite: Zhou, T., Tarduno, J., Cottrell, R., and Nimmo, F.: Early Cambrian renewal of the geodynamo and the origin of inner core structure, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10532,, 2022.

Corresponding displays formerly uploaded have been withdrawn.