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

Paleomagnetic 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 similar to 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. The geomagnetic field plays an important role in maintaining the Earth's habitability by shielding harmful energetic particles from the universe and serves as a window to the Earth's deep interior. Studying the variation patterns of the geomagnetic field is useful for detecting the geometry of the field, revealing the dynamic process of the Earth as well as stratigraphic correlation and dating. Continuous information of the geomagnetic field can be obtained by performing magnetic measurements on lake, marine and loess sediments. In this study, we conducted paleomagnetic study on a high sedimentation rate Holocene loess section in Northwest China and recovered directional variation of the geomagnetic field since similar to 13 ka. And then, we compiled the sediment data and calculated a composite geomagnetic directional reference curve spanning the past similar to 14 ka for East Asia. We further established an East Asian regional geomagnetic directional model with the new and compiled data, which can predict variations of the field direction at any point in the region within a spherical cap of 25 degrees centered at 30oN, 108oE in East Asia. The established composite curve and regional model in this study provide local reference field for global comparison of the geomagnetic field and space physics study. A high-resolution PSV record includes both absolute declination and inclination since similar to 13 ka from a loess section in the Northwest China A composite PSV reference curve over the past 14 ka (EASed14k) based on sediment data A regional geomagnetic directional model (SCHA.EAS14k) over similar to 14 ka was established for East Asia with compiled sediment data in the region