Subduction flux modulates the geomagnetic polarity reversal rate

Hounslow, Mark W and Domeier, Mathew and Biggin, Andrew J (2018) Subduction flux modulates the geomagnetic polarity reversal rate. Tectonophysics, 742-74. pp. 34-49. ISSN 0040-1951

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The cause of variations in the frequency of geomagnetic polarity reversals through the Phanerozoic has remained a primary research question straddling palaeomagnetism and geodynamics for decades. Numerical models suggest the primary control on geomagnetic reversal rate on 10 to 100 Ma timescales is the changing heat flux across the core-mantle boundary, a flux which is expected to be influenced by variations in the lithosphere subducted into the mantle. A positive relationship between the time-dependent global subduction flux and magnetic reversal rate is expected, with a time delay to transmit the thermal imprint into the lowermost mantle. We perform the first test of this hypothesis using subduction flux estimates and geomagnetic reversal rate data back to the early Paleozoic. Subduction area flux is derived from global, full-plate tectonic models, and evaluated against independent subduction flux proxies based on strontium isotopes and age distribution of detrital zircons . A continuous Phanerozoic reversal rate model is built from pre-existing compilations back to ~320 Ma plus a new reversal rate model in the data-sparse mid-to-early Paleozoic. Cross-correlation of the time-dependent subduction flux and geomagnetic reversal rate series reveals a significant correlation with a time delay of ~120 Ma (with reversals trailing the subduction flux). This time delay represents a value intermediate between the seismologically constrained time expected for a subducted slab to transit from the surface to the core-mantle boundary (~150-300 Ma), and the much shorter lag time predicted by some numerical models of mantle flow (~30-60 Ma). Our novel estimate of lag time, encouragingly represents a compromise between them. Important uncertainties in our proposed relationship remain, but the results cast new light on the dynamic connections between the surface and deep Earth, and will help to constrain new models linking mantle convection, the thermal evolution of the lowermost mantle, and the geodynamo.

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21 May 2018 12:58
Last Modified:
16 Sep 2023 01:41