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Intensity of the Earth's magnetic field: Evidence for a Mid-Paleozoic dipole low.
Hawkins, Louise M A; Grappone, J Michael; Sprain, Courtney J; Saengduean, Patipan; Sage, Edward J; Thomas-Cunningham, Sheikerra; Kugabalan, Banusha; Biggin, Andrew J.
Afiliação
  • Hawkins LMA; Geomagnetism Laboratory, Department of Earth, Ocean and Ecological Sciences, University of Liverpool, Liverpool L69 7ZE, United Kingdom; louisemahawkins@gmail.com.
  • Grappone JM; Geomagnetism Laboratory, Department of Earth, Ocean and Ecological Sciences, University of Liverpool, Liverpool L69 7ZE, United Kingdom.
  • Sprain CJ; Geomagnetism Laboratory, Department of Earth, Ocean and Ecological Sciences, University of Liverpool, Liverpool L69 7ZE, United Kingdom.
  • Saengduean P; Department of Geological Sciences, The University of Florida, Gainesville, FL 32611.
  • Sage EJ; Geomagnetism Laboratory, Department of Earth, Ocean and Ecological Sciences, University of Liverpool, Liverpool L69 7ZE, United Kingdom.
  • Thomas-Cunningham S; Department of Geophysics, Colorado School of Mines, Golden, CO 80401.
  • Kugabalan B; Geomagnetism Laboratory, Department of Earth, Ocean and Ecological Sciences, University of Liverpool, Liverpool L69 7ZE, United Kingdom.
  • Biggin AJ; CGG Satellite Mapping, Edenbridge TN8 6SR, United Kingdom.
Proc Natl Acad Sci U S A ; 118(34)2021 08 24.
Article em En | MEDLINE | ID: mdl-34404726
ABSTRACT
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.
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Texto completo: 1 Coleções: 01-internacional Base de dados: MEDLINE Tipo de estudo: Prognostic_studies / Qualitative_research Idioma: En Revista: Proc Natl Acad Sci U S A Ano de publicação: 2021 Tipo de documento: Article

Texto completo: 1 Coleções: 01-internacional Base de dados: MEDLINE Tipo de estudo: Prognostic_studies / Qualitative_research Idioma: En Revista: Proc Natl Acad Sci U S A Ano de publicação: 2021 Tipo de documento: Article