Earth's Magnetic Field Strength and the Cretaceous Normal Superchron: New Data From Costa Rica
Abstract Constraining the long‐term variability and average of the Earth's magnetic field strength is fundamental to understanding the characteristics and behavior of the geomagnetic field. Questions remain about the strength of the average field, and the relationship between strength and rever...
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| Format: | Article |
| Language: | English |
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Wiley
2021-04-01
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| Series: | Geochemistry, Geophysics, Geosystems |
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| Online Access: | https://doi.org/10.1029/2020GC009605 |
| _version_ | 1797638052679516160 |
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| author | A. Di Chiara L. Tauxe H. Staudigel F. Florindo M. Protti Y. Yu J.‐A. Wartho P. van den Bogaard K. Hoernle |
| author_facet | A. Di Chiara L. Tauxe H. Staudigel F. Florindo M. Protti Y. Yu J.‐A. Wartho P. van den Bogaard K. Hoernle |
| author_sort | A. Di Chiara |
| collection | DOAJ |
| description | Abstract Constraining the long‐term variability and average of the Earth's magnetic field strength is fundamental to understanding the characteristics and behavior of the geomagnetic field. Questions remain about the strength of the average field, and the relationship between strength and reversal frequency, due to the dispersion of data from key time intervals. Here, we focus on the Cretaceous Normal Superchron (CNS; 121‐84 Ma), during which there were no reversals. We present new intensity results from 41 submarine basaltic glass (SBG) sites collected on the Nicoya Peninsula and Murcièlago Islands, Costa Rica. New and revised 40Ar/39Ar and biostratigraphic age constraints from previous studies indicate ages from 141 to 65 Ma. One site with an age of 135.1 ± 1.5 Ma (2σ) gave a reliable intensity result of 34 ± 8 µT (equivalent to a virtual axial dipole moment, VADM, value of 88 ± 20 ZAm2), three sites from 121 to 112 Ma, spanning the onset of the CNS, vary from 21 ± 1 to 34 ± 4 µT (53 ± 3 to 87 ± 10 ZAm2). These results from the CNS are all higher than the long‐term average of ∼42 ZAm2 and data from Suhongtu, Mongolia (46–53 ZAm2) and are similar to the Troodos Ophiolite, Cyprus (81 ZAm2, reinterpreted in this study). Together with the reinterpreted data, the new Costa Rica results suggest that the strength of the geomagnetic field was approximately the same both before and after the onset of the CNS. Therefore, the data do not support a strict correlation between polarity interval length and the strength of the magnetic field. |
| first_indexed | 2024-03-11T12:58:08Z |
| format | Article |
| id | doaj.art-09c6e09194f34316a49913a0403221fa |
| institution | Directory Open Access Journal |
| issn | 1525-2027 |
| language | English |
| last_indexed | 2024-03-11T12:58:08Z |
| publishDate | 2021-04-01 |
| publisher | Wiley |
| record_format | Article |
| series | Geochemistry, Geophysics, Geosystems |
| spelling | doaj.art-09c6e09194f34316a49913a0403221fa2023-11-03T16:55:42ZengWileyGeochemistry, Geophysics, Geosystems1525-20272021-04-01224n/an/a10.1029/2020GC009605Earth's Magnetic Field Strength and the Cretaceous Normal Superchron: New Data From Costa RicaA. Di Chiara0L. Tauxe1H. Staudigel2F. Florindo3M. Protti4Y. Yu5J.‐A. Wartho6P. van den Bogaard7K. Hoernle8Istituto Nazionale di Geofisica e Vulcanologia Rome ItalyScripps Institution of Oceanography La Jolla CA USAScripps Institution of Oceanography La Jolla CA USAIstituto Nazionale di Geofisica e Vulcanologia Rome ItalyObservatorio Vulcanológico y Sismológico de Universidad Nacional de Costa Rica Heredia Costa RicaDepartment of Geological Sciences Chungnam National University Daejeon KoreaGEOMAR Helmholtz Centre for Ocean Research Kiel Kiel GermanyGEOMAR Helmholtz Centre for Ocean Research Kiel Kiel GermanyGEOMAR Helmholtz Centre for Ocean Research Kiel Kiel GermanyAbstract Constraining the long‐term variability and average of the Earth's magnetic field strength is fundamental to understanding the characteristics and behavior of the geomagnetic field. Questions remain about the strength of the average field, and the relationship between strength and reversal frequency, due to the dispersion of data from key time intervals. Here, we focus on the Cretaceous Normal Superchron (CNS; 121‐84 Ma), during which there were no reversals. We present new intensity results from 41 submarine basaltic glass (SBG) sites collected on the Nicoya Peninsula and Murcièlago Islands, Costa Rica. New and revised 40Ar/39Ar and biostratigraphic age constraints from previous studies indicate ages from 141 to 65 Ma. One site with an age of 135.1 ± 1.5 Ma (2σ) gave a reliable intensity result of 34 ± 8 µT (equivalent to a virtual axial dipole moment, VADM, value of 88 ± 20 ZAm2), three sites from 121 to 112 Ma, spanning the onset of the CNS, vary from 21 ± 1 to 34 ± 4 µT (53 ± 3 to 87 ± 10 ZAm2). These results from the CNS are all higher than the long‐term average of ∼42 ZAm2 and data from Suhongtu, Mongolia (46–53 ZAm2) and are similar to the Troodos Ophiolite, Cyprus (81 ZAm2, reinterpreted in this study). Together with the reinterpreted data, the new Costa Rica results suggest that the strength of the geomagnetic field was approximately the same both before and after the onset of the CNS. Therefore, the data do not support a strict correlation between polarity interval length and the strength of the magnetic field.https://doi.org/10.1029/2020GC009605Ar/ArCosta RicaCretaceous Normal SuperchronPaleointensity |
| spellingShingle | A. Di Chiara L. Tauxe H. Staudigel F. Florindo M. Protti Y. Yu J.‐A. Wartho P. van den Bogaard K. Hoernle Earth's Magnetic Field Strength and the Cretaceous Normal Superchron: New Data From Costa Rica Geochemistry, Geophysics, Geosystems Ar/Ar Costa Rica Cretaceous Normal Superchron Paleointensity |
| title | Earth's Magnetic Field Strength and the Cretaceous Normal Superchron: New Data From Costa Rica |
| title_full | Earth's Magnetic Field Strength and the Cretaceous Normal Superchron: New Data From Costa Rica |
| title_fullStr | Earth's Magnetic Field Strength and the Cretaceous Normal Superchron: New Data From Costa Rica |
| title_full_unstemmed | Earth's Magnetic Field Strength and the Cretaceous Normal Superchron: New Data From Costa Rica |
| title_short | Earth's Magnetic Field Strength and the Cretaceous Normal Superchron: New Data From Costa Rica |
| title_sort | earth s magnetic field strength and the cretaceous normal superchron new data from costa rica |
| topic | Ar/Ar Costa Rica Cretaceous Normal Superchron Paleointensity |
| url | https://doi.org/10.1029/2020GC009605 |
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