A detailed paleomagnetic record between 2.1 and 2.75 Ma at IODP Site U1314 in the North Atlantic: Geomagnetic excursions and the Gauss-Matuyama transition

• Published in: Geochemistry Geophysics Geosystems
• Main Authors: Ohno, Masao, Hayashi, Tatsuya, Komatsu, Fumiki, Murakami, Fumi, Zhao, Meng, Guyodo, Yohan, Acton, Gary, Evans, Helen F., Kanamatsu, Toshiya
• Other Authors: Institut de Physique du Globe de Paris (IPGP), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Université de La Réunion (UR)-Institut de Physique du Globe de Paris (IPG Paris)-Centre National de la Recherche Scientifique (CNRS)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2012
• Subjects: [SDU]Sciences of the Universe [physics]; North Atlantic
• Online Access: https://hal-insu.archives-ouvertes.fr/insu-03583351; https://hal-insu.archives-ouvertes.fr/insu-03583351/document; https://hal-insu.archives-ouvertes.fr/insu-03583351/file/Geochem%20Geophys%20Geosyst%20-%202012%20-%20Ohno%20-%20A%20detailed%20paleomagnetic%20record%20between%202%201%20and%202%2075%20Ma%20at%20IODP%20Site%20U1314%20in%20the.pdf; https://doi.org/10.1029/2012GC004080

International audience This study investigated the detailed geomagnetic field variation between 2.1 and 2.75 Ma from a sediment core (IODP Site U1314) with high sedimentation rate (≥10 cm/kyr) and good age control. Characteristic remanent magnetization directions were well resolved by stepwise alternating field demagnetization. As a proxy of relative paleointensity, natural remanent magnetization (NRM) normalized by anhysteretic remanent magnetization (ARM) was used after testing that the influence of magnetic interaction in ARM is negligible. As a result, the following features of the geomagnetic field in the studied period have been revealed. During the transition of the Gauss-Matuyama (G-M) reversal and the Réunion Subchron, the paleointensity decreased to the value lower than 20% of the average intensity in the whole studied interval. In addition to these lows, eight paleointensity lows were found associated with large directional changes that satisfy the definition of a geomagnetic excursion. Four of these have ages close to ages reported for geomagnetic excursions in prior studies, whereas the other four excursions have not previously been observed. In our results, we confirm that the G-M transition occurred in marine isotope stage 103 even if we consider the shift in depth due to the lock-in process of magnetic particles. The temporal variation in paleointensity showed asymmetric behavior associated with the G-M transition, with a gradual decrease prior to the transition and a rapid recovery after the transition.