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The Global Archeomagnetic Database: Updates to GEOMAGIA50

Abstract : Compilations of archeomagnetic data are fundamental to our understanding of the evolution of Earth’s magnetic field on centennial to millennial time scales. From the earliest studies of the Thelliers, Aitken, Nagata and others in the 1950s and 1960s, who obtained directional and paleointensity data from artefacts from Europe, the Near East, Asia and South America, archeomagnetic data have been vital for extending our knowledge of the field prior to observational measurements. Today, many thousands of archeomagnetic data allow us to explore the geomagnetic field in more detail than ever before. Both regional time series of archeomagnetic data and their inclusion in time-varying global spherical harmonic field models have revealed a range of newly discovered field behavior. An ever increasing number of archeomagnetic data have the potential to improve our understanding of these observations. This includes the evolution of the South Atlantic Anomaly and its possibly recurrent nature, how low the field can get during these anomalies, bounds on how quickly paleointensity can change, e.g., the Levant geomagnetic spike, the upper limits of paleointensity during such spikes, and the geographic range of these anomalies. Since the previous release of GEOMAGIA50 in 2017, we have compiled 1716 new and legacy archeomagnetic entries spanning the past 10 ka from 109 publications. For this time, the database now contains 9083 archeomagnetic entries from 663 studies published up to May 2019 (10,446 entries from 794 studies if volcanic data are included). A special focus was placed on adding data from the southern Hemisphere, the Tropics and the Levant (and surrounding areas). Southern Hemisphere archeomagnetic entries have increased by 155 to a total of 430; however, this is still only 5% of all archeomagnetic entries for the past 10 ka. The majority of Southern Hemisphere data are from South America, with a smaller contribution from southern Africa. For the Tropics, 379 entries were added, now totaling 907 entries. In the Levant and surrounding region (ranging from Georgia to Egypt), 363 entries have been added, totaling 1319 entries for this area, with 1194 being archeointensities. These new data will be essential for addressing how low, how high and how quickly the field can change on centennial to millennial time scales.
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Contributor : Isabelle Dubigeon <>
Submitted on : Wednesday, January 8, 2020 - 11:11:39 AM
Last modification on : Wednesday, April 15, 2020 - 1:22:32 AM

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  • HAL Id : insu-02431865, version 1

Citation

Maxwell Christopher Brown, Gwenaël Hervé. The Global Archeomagnetic Database: Updates to GEOMAGIA50. American Geophysical Union Fall Meeting 2019, American Geophysical Union, Dec 2019, San Francisco, United States. pp.GP34A-07. ⟨insu-02431865⟩

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