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Reconstructing the Phanerozoic Geodynamo

Reconstructing the Phanerozoic Geodynamo. Whole-Earth approach (mantle + core + time) to geodynamo history CMB heat flux from two models of the Phanerozoic mantle: M antle convection with mobile plates and continents (model HF1 by Zhang & Zhong , 2011)

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Reconstructing the Phanerozoic Geodynamo

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  1. Reconstructing the Phanerozoic Geodynamo • Whole-Earth approach (mantle + core + time) to geodynamo history • CMB heat flux from two models of the Phanerozoic mantle: • Mantle convection with mobile plates and continents • (model HF1 by Zhang & Zhong, 2011) • Present-day lower mantle seismic heterogeneity • Core evolution determined by CMB heat flux, including • Inner core growth • Chemical differentiation (Fe-Le) • CMB heterogeneity • Tidal breaking (via increase in length of day) • Calculate dynamo time average magnetic fields and polarity reversals over 5 Myr long stages • Tune dynamos to present-day (0-5 Ma) reversal rate

  2. Box Model: Core Evolution ~ 700 Myr Thermodynamic Parameters CMB Heat Flow Q(t) T(r,0), C(r,0), rICB(0) T(r,t,) C(r,t) rICB(t) 3D Model: Numerical Dynamo ~ 5 Myr stages CMB Heat Flux q(x) W(t) Transport Parameters T(x,t,) C(x,t) B(x,t) GPTS Reversals

  3. Phanerozoic Core Evolution (thanks to Renaud!) HF1 Variable evolution Driver: mantle reconstruction HF1 (Zhang & Zhong, 2011) Regular assembly Pangea breakup Regular evolution Driver: constant CMB heat flow total ICB Compositional CMB heat flow

  4. Parametric Core Evolution Ma E/E(0) HF1 Ma Regular Ra/Ra(0)

  5. Present-day (0-5 Ma) Reversal Records

  6. Polarity Reversal Record Comparison

  7. GPTS (5.4 Myr)

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