Dating of Holocene western Canadian Arctic sediments by matching paleomagnetic secular variation to a geomagnetic field model

摘要

A recently recovered ～6-m long Holocene sedimentary sequence (piston Core 2004-804-650) collected from the Beaufort Sea (western Canadian Arctic) was dated by combining the paleomagnetic secular variation (PSV) and a time-varying spherical harmonic model of the geomagnetic field (CALS7k.2). A u-channel-based paleomagnetic study reveals the presence of a stable, single component of magnetization (MAD <5°) carried by low-coercivity ferrimagnetic minerals (most likely magnetite) in the pseudo-single domain grain size range. An age-depth model spanning the last ～6000. cal. BP was established from nine paleomagnetic tie points obtained by comparing the magnetic declination profiles of Core 650 and the CALS7k.2 model output. In order to verify the robustness of the method, both the magnetic inclination and the relative paleointensity (RPI) records of Core 650 were then compared with western North American lacustrine and volcanic Holocene PSV records, as well as with previously published RPI records from the Beaufort and Chukchi Seas. Several common magnetic inclination features and similar millennial-scale fluctuations are detected among the records, supporting a common geomagnetic origin of the records, and implying consistency of the derived age model. These results show the potential of using both the CALS7k.2 model output and PSV of the geomagnetic field as a practical dating tool.