High-resolution relative paleointensities over the last 40 ka from marine sediments in the western equatorial pacific: Magnetic events and interhemispheric correlation
Résumé
Core MD01-2385 retrieved in the western equatorial Pacific (Northwest of Papua-New Guinea) has been sampled every 2 cm for paleomagnetic and radiocarbon measurements. The age model, well constrained by 47 14 C ages (both new and former), indicates that our record spans approximately the last 38 ka. The average sedimentation rate is ~30 cm/ka. Analysis of the magnetic mineralogy revealed that the natural remanent magnetization (NRM) is predominantly carried by magnetite. A relative paleointensity record (RPI) was derived, allowing us to estimate a lock-in depth of approximately 18 cm, corresponding to ~600 years in our case, by comparing it with the CALS10k.2 model. Comparison with two other western Equatorial Pacific RPI, selected for their geographical proximity (~1000 km) and high resolution, allowed us to compile a regional reference record (WEPEQ). Several intervals of lower intensities have been identified and may correspond to the known events of Mono Lake (~34 ka), Rockall (~27 ka), Hilina Pali (~18 ka) and possibly Tianchi (~5-8 ka). Overall, our equatorial curve exhibits strong similarities with RPI curves from mid to low latitudes, such as those from the Iberian Margin and Black Sea. A detailed investigation hints at the presence of non-dipolar structures in the Earth's magnetic field at the shorter time scale, especially during the low intensity intervals. In contrast, notable differences are observed when compared to high-latitude stacks, especially from the North Atlantic (NAPIS). This points to the potential climatic bias that may affect high-latitude records during the glacial maximum and glacial-interglacial transition.
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