High‐Resolution Paleomagnetic Secular Variation Since ∼13 ka From a Loess Section in Northwest China and a Regional Geomagnetic Directional Model for East Asia

Abstract

AbstractPaleomagnetic secular variation (PSV) records provide important information for the dynamic processes of the Earth's geomagnetic field, and also can be used for regional stratigraphic correlation. We conducted a paleomagnetic study on a high sedimentation rate Holocene loess section (the Minle section) with precise 14C age constraints in Northwest China. Rock magnetic results indicate that single domain and pseudo‐single‐domain magnetites are the main magnetic carriers of the natural remanent magnetization. Combining the alternating field demagnetization and thermal demagnetization results, we obtained a high‐resolution PSV record with both absolute declination and inclination since ∼13 ka. Combining with previously published sedimentary records in East Asia, we developed an East Asian PSV reference curve over the past 14 ka (EASed14k) by relocating all the data to a common location (30ºN, 108ºE) and averaging them through Fisher statistics. We further generated a regional geomagnetic directional model spanning the past 14 ka for East Asia (SCHA.EAS14k), using the in situ PSV records and applying the revised spherical cap harmonic analysis in space and cubic B‐spline in time. The predicted directional curves from this model at the common location are consistent with the EASed14k curves, which represent the first‐order variation of the geomagnetic field in this area. The established reference curve and regional model for East Asia in this study will be used for regional and global comparison of the geomagnetic field.