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

Abstract

[1] 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 Copyright 2012 by the American Geophysical Union 1 of 16 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.

Precise ages of the Réunion event and Huckleberry Ridge excursion: Episodic clustering of geomagnetic instabilities and the dynamics of flow within the outer core

“…Nevertheless, the level of uncertainty indicates a maximum duration of ∼10 kyr. Ohno et al (2012) observed a number of lows in relative paleointensity between 2.8 and 2.1 Ma in a sedimentary record from the North Atlantic. These lows were accompanied by directional changes that lasted between 1 and 4 kyr.…”

“…Magnetic polarity of lava indicated by: open bars reversed; filled bars normal; striped bars transitional. Astrochronologic age models from Channell et al (2003), Ohno et al (2012), and Channell and Guyodo (2004) show VGP latitude vs. age. VGP data from Horng et al (2002) is uncertain due to anomalous declination measurements arising from deformation of the core during its retrieval; their reported age of the "Réunion subchron" is highly uncertain at the older limit.…”

“…Using sediment core MD97423 from the Philippine Sea, Horng et al (2002) places a normal polarity subchron at 2.133-2.118 Ma, but the very low sedimentation rate of 1.5 cm/kyr, coarse spacing of the discrete samples, and a sandy layer near the base of the core limit the temporal resolution around the time of the Réunion event. Similar ages were assigned to normal polarity subchrons found in cores from the North Atlantic (Channell and Guyodo, 2004;Ohno et al, 2012). The most highly resolved normal polarity chronozone in sediments, occurring from 2.153 to 2.115 Ma, is recorded in the Feni Drift at ODP site 981, where high sedimentation rates (peaking at 18 cm/kyr) give an expanded, high-fidelity record (Channell et al, 2003;Fig.…”

Re-evaluation of the age model for North Atlantic Ocean Site 982 – arguments for a return to the original chronology

“…5), which compares favorably (within 5 cm) with the shipboard-derived depth of the G/M chronozone reversal boundary in Hole A (57.24 mcd). This depth in the original age model (= interglacial MIS 103; Channell and Guyodo, 2004) corresponds well to our understanding of the temporal relationships between the G/M chronozone reversal and records of benthic δ 18 O (Ohno et al, 2012) (Figs. 2, 5).…”

Recent progress on rock and paleomagnetism by means of deepsea drilling

“…1 10 nm , , e.g., Kopp andKirschvink, 2008 TEM 2000 first-order reversal curve FORC e.g., Roberts et al, 2000ARM IRM e.g., Egli, 2004Yamazaki, 2008Egli et al, 2010;Li et al, 2012;Chang et al, 2014Roberts et al, 2011, 2012Yamazaki, 2012;Yamazaki and Ikehara, 2012 e.g., Yamamoto et al, 2003;Paterson et al, 2014;Cromwell et al, 2015 ARM, IRM 1990 e.g., Tauxe, 1993 90 / 80 Sint-800; Guyodo and Valet, 1999 IODP e.g., Karlin, 1990; Ohno et al, 2012) and Site U1308 (gray, Channell et al, 2016) in the North Atlantic, and (lower) the EPAPIS-3000 stack from equatorial Pacific piston cores (Yamazaki and Oda, 2005 Suganuma et al, 2010;Ménabréaz et al, 2012;Horiuchi et al, 2016 10 Be Granot et al, 2012 e.g., Channell et al, 1998;Yamazaki, 1999;Thouveny et al, 2004Xuan et al, 2008Valet et al, 2011Kitaba et al, 2013 Kono, 1980;Tarduno et al, 2003 Expedition 330 Koppers et al, 2012aKoppers et al, 2012bSteinberger et al, 2004Hassan et al, 2016 anisotropy of magnetic susceptibility, AMS AMS AMS AMS AMS …”