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Are Paleomagnetic Records From U‐Channels Appropriate for Studies of Reversals and Excursions?

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Philippe, Édouard G. H. et Valet, Jean-Pierre et St-Onge, Guillaume et Thevarasan, Anojh (2018). Are Paleomagnetic Records From U‐Channels Appropriate for Studies of Reversals and Excursions? Geochemistry Geophysics Geosystems, 19 (11). p. 4130-4142.

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Résumé

Sampling of sediment cores using plastic U‐channels has made possible the acquisition of detailed records of paleomagnetic secular variation, geomagnetic polarity, environmental magnetic studies, and relative paleointensity over the past several million years. U‐channel measurements provide the great advantage of rapid measurements of long sediment cores, but the signal resolution is attenuated by the response function of the magnetometer sensors, which therefore restrains the recovery of rapid and large‐amplitude field changes. Here we focus on the suitability of the dynamics of reversals and excursions derived from U‐channel measurements. We compare successive individual paleomagnetic directions of 1.5 cm × 1.5 cm × 1.5 cm cubic discrete samples with those of a 1.5‐m equivalent U‐channel sample train obtained by placing the samples adjacent to each other. We use varying excursion and transition lengths and generate transitional directions that resemble those of the most detailed paleomagnetic records. Excursions with opposite polarity directions recorded over less than 7.5 cm are barely detected in U‐channel measurements. Regarding reversals, U‐channel measurements smooth the signal of low‐resolution records and generate artificial transitional directions. Despite producing misleading similarities with the overall structure of transition records, longer transitional intervals fail also to reproduce the complexity of field changes. Finally, we test the convolution of magnetization by different response functions. The simulation reveals that even small response function changes can generate significant differences in results. -- Keywords : geomagnetic reversals ; geomagnetic excursions ; paleomagnetic measurements.

Type de document : Article
Validation par les pairs : Oui
Information complémentaire : Une version éditée de cet article a été publiée par AGU. Copyright (2018) American Geophysical Union. An edited version of this paper was published by AGU. Copyright (2018) American Geophysical Union. Référence de la publication originale: Philippe, É. G. H., Valet, J.‐P., St‐Onge, G., & Thevarasan, A. ( 2018). Are paleomagnetic records from U‐channels appropriate for studies of reversals and excursions? Geochemistry, Geophysics, Geosystems, 19, 4130– 4142. https://doi.org/10.1029/2018GC007803
Départements et unités départementales : Institut des sciences de la mer de Rimouski (ISMER)
Déposé par : DIUQAR UQAR
Date de dépôt : 16 oct. 2020 17:59
Dernière modification : 16 oct. 2020 17:59
URI : http://semaphore.uqar.ca/id/eprint/1678

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