Field recording mechanism in bioturbated sediments: new insights from 10Be, relative paleointensity, and microtektites

Despite over 70 years of research on sedimentary paleomagnetism, fully quantitative models describing the timing and efficiency of the recording mechanism are not yet available. Here, we present new insights for bioturbated sediments, based on cosmogenic ¹⁰Be records of the global field intensity, relative paleointensity, and the depth distribution of microtektites. The effect of bioturbation on cosmogenic ¹⁰Be and on microtektites is described by a solid diffusion model, with microtektites serving as calibration for the impulse response associated with the diffusion process. The acquisition of a post-depositional remanent magnetization, on the other hand, is governed by a biased rotational diffusion process with bias proportional to the intensity of the magnetic field. The dependence of diffusion on depth yields the relative offset between the impulse responses of ¹⁰Be and relative paleointensity, and thus also the time delay of the latter. The delay expected from this model compares favorably with ¹⁰Be and relative paleointensity records of sediment cores from the Indian and Pacific Oceans. This work was made possible by Jean-Pierre’s ERC Grant EDIFICE.