Paleomagnetic inclination variations during the last 200 kyr in the Okhotsk Sea and their relation to persistent non-axial-dipole field

Abstract Studies on geomagnetic paleointensity using marine sediments revealed that intensity fluctuations contain variations with timescales of 104 years and longer. In contrast, directional secular variations of such timescales were far less studied. In this paper we study inclination variations of longer than a millennial timescale using sediment cores at nine sites in the Okhotsk Sea. Relative paleointensity and magnetic susceptibility variations were used for inter-core correlations and age estimations. The average inclinations of individual cores were close to those of the geocentric axial dipole (GAD) field at the site latitudes. A stacked inclination curve for the last 200 kyr showed intervals of shallower inclinations at about 25–45, 75–90, 110–135, and 185–200 ka. These are synchronous with inclination shifts toward negative previously reported in the western equatorial Pacific, and temporally coincide with paleointensity lows in general. Both the Okhotsk Sea and western equatorial Pacific are within a region of outward directed flux in the persistent non-axial-dipole (NAD) field, and the synchronous inclination shifts may have been caused by a larger contribution of the NAD field when the GAD was weaker. Graphical Abstract .