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DOI	10.1073/pnas.2017342118
	Intensity of the Earth’s magnetic field: Evidence for a Mid-Paleozoic dipole low
	Hawkins L.M.A.; Grappone J.M.; Sprain C.J.; Saengduean P.; Sage E.J.; Thomas-Cunningham S.; Kugabalan B.; Biggin A.J.
发表日期	2021
ISSN	0027-8424
卷号	118 期号:34
英文摘要	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 ZAm2) and 4 to 11 μT (9 to 27 ZAm2) 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 (QPI). The procurement of reliable (QPI ≥ 5) weak paleointensity estimates from this and other studies indicates a period of low dipole moment (median field strength of 17 ZAm2) 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. © 2021 National Academy of Sciences. All rights reserved.
英文关键词	Dipole moment; Paleointensity; Paleozoic
语种	英语
scopus关键词	article; bear; Carboniferous; dipole; magnetic field; Mesozoic; microscopy; microwave radiation; nonhuman; thermodynamics; United Kingdom
来源期刊	Proceedings of the National Academy of Sciences of the United States of America
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/238934
作者单位	Geomagnetism Laboratory, Department of Earth, Ocean and Ecological Sciences, University of Liverpool, Liverpool, L69 7ZE, United Kingdom; Department of Geological Sciences, The University of Florida, Gainesville, FL 32611, United States; Department of Geophysics, Colorado School of Mines, Golden, CO 80401, United States; CGG Satellite Mapping, Edenbridge, TN8 6SR, United Kingdom; School of Physics and Astronomy, University of Glasgow, Glasgow, G12 8QQ, United Kingdom
推荐引用方式 GB/T 7714	Hawkins L.M.A.,Grappone J.M.,Sprain C.J.,等. Intensity of the Earth’s magnetic field: Evidence for a Mid-Paleozoic dipole low[J],2021,118(34).
APA	Hawkins L.M.A..,Grappone J.M..,Sprain C.J..,Saengduean P..,Sage E.J..,...&Biggin A.J..(2021).Intensity of the Earth’s magnetic field: Evidence for a Mid-Paleozoic dipole low.Proceedings of the National Academy of Sciences of the United States of America,118(34).
MLA	Hawkins L.M.A.,et al."Intensity of the Earth’s magnetic field: Evidence for a Mid-Paleozoic dipole low".Proceedings of the National Academy of Sciences of the United States of America 118.34(2021).