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Sci Adv. 2017 Feb 15;3(2):e1602306. doi: 10.1126/sciadv.1602306. eCollection 2017 Feb.

Intrinsic paleointensity bias and the long-term history of the geodynamo.

Author information

1
Department of Geological and Mining Engineering and Sciences, Michigan Technological University, 1400 Townsend Drive, Houghton, MI 49931, USA.; Department of Physics, Michigan Technological University, Houghton, MI 49931, USA.
2
Centre for Earth Evolution and Dynamics, University of Oslo, N-0315 Oslo, Norway.
3
Department of Geological and Mining Engineering and Sciences, Michigan Technological University, 1400 Townsend Drive, Houghton, MI 49931, USA.

Abstract

Many geodynamo models predict an inverse relationship between geomagnetic reversal frequency and field strength. However, most of the absolute paleointensity data, obtained predominantly by the Thellier method from bulk volcanic rocks, fail to confirm this relationship. Although low paleointensities are commonly observed during periods of high reversal rate (notably, in the late Jurassic), higher than present-day intensity values are rare during periods of no or few reversals (superchrons). We have identified a fundamental mechanism that results in a pervasive and previously unrecognized low-field bias that affects most paleointensity data in the global database. Our results provide an explanation for the discordance between the experimental data and numerical models, and lend additional support to an inverse relationship between the reversal rate and field strength as a fundamental property of the geodynamo. We demonstrate that the accuracy of future paleointensity analyses can be improved by integration of the Thellier protocol with low-temperature demagnetizations.

KEYWORDS:

Geomagnetism; Thellier method; geodynamo; geomagnetic field; paleointensity; paleomagnetism

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