Intensity of the Earth's magnetic field: Evidence for a Mid-Paleozoic dipole low

Hawkins, Louise MA, Grappone, J Michael ORCID: 0000-0001-5004-8561, Sprain, Courtney J, Saengduean, Patipan, Sage, Edward J, Thomas-Cunningham, Sheikerra, Kugabalan, Banusha ORCID: 0000-0002-4500-123X and Biggin, Andrew J ORCID: 0000-0003-4164-5924 (2021) Intensity of the Earth's magnetic field: Evidence for a Mid-Paleozoic dipole low. Proceedings of the National Academy of Sciences, 118 (34). e2017342118-e2017342118.

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Official URL: http://dx.doi.org/10.1073/pnas.2017342118

Abstract

<jats:p>The Mesozoic Dipole Low (MDL) is a period, covering at least ∼80 My, of low dipole moment that ended at the start of the Cretaceous Normal Superchron. Recent studies of Devonian age Siberian localities identified similarly low field values a few tens of million years prior to the Permo-Carboniferous Reverse Superchron (PCRS). To constrain the length and timing of this potential dipole low, this study presents paleointensity estimates from Strathmore (∼411 to 416 Ma) and Kinghorn (∼332 Ma) lava flows, United Kingdom. Both localities have been studied for paleomagnetic poles (Q values of 6 to 7), and the sites were assessed for their suitability for paleointensity from paleodirections, rock magnetic analysis, and microscopy. Thermal and microwave experiments were used to determine site mean paleointensity estimates of ∼3 to 51 μT (6 to 98 ZAm<jats:sup>2</jats:sup>) and 4 to 11 μT (9 to 27 ZAm<jats:sup>2</jats:sup>) from the Strathmore and Kinghorn localities, respectively. These, and all the sites from 200 to 500 Ma from the (updated) Paleointensity database (PINT15), were assessed using the Qualitative Paleointensity criteria (Q<jats:sub>PI</jats:sub>). The procurement of reliable (Q<jats:sub>PI</jats:sub> ≥ 5) weak paleointensity estimates from this and other studies indicates a period of low dipole moment (median field strength of 17 ZAm<jats:sup>2</jats:sup>) from 332 to 416 Ma. This “Mid-Paleozoic Dipole Low (MPDL)” bears a number of similarities to the MDL, including the substantial increase in field strength near the onset of the PCRS. The MPDL also adds support to the inverse relationship between reversal frequency and field strength and a possible ∼200-My cycle in paleomagnetic behavior relating to mantle convection.</jats:p>

Item Type:	Article
Uncontrolled Keywords:	dipole, dipole moment, paleointensity, Paleozoic
Divisions:	Faculty of Science and Engineering > School of Environmental Sciences
Depositing User:	Symplectic Admin
Date Deposited:	15 Dec 2021 12:23
Last Modified:	18 Jan 2023 21:19
DOI:	10.1073/pnas.2017342118
Related URLs:	Author Publisher
URI:	https://livrepository.liverpool.ac.uk/id/eprint/3145405