A new high-resolution magnetic scanner for sedimentary sections

We developed a fully automated magnetic field scanner dedicated to uniaxial magnetic field measurements to determine remanent magnetization intensities and their variations in sedimentary U channels. A fluxgate magnetometer located as close as possible from the sedimentary section is used to perform uniaxial measurements of magnetic fields locally generated by isothermal remanent magnetization. This artificial magnetization, which is known to be a powerful proxy in environmental magnetism, is produced perpendicular to the U channel long axis, and parallel to the fluxgate axis, using a Halbach cylinder prior to the measurement. The magnetic scanner offers a maximal spatial resolution of 5.8 mm. The spatial resolution of 14 mm is obtained for U channel samples. The magnetic scanner covers a large range of magnetic field signals including those that saturates the Superconducting Rock Magnetometer in its classical configuration. The estimation of the remanent magnetization intensities along the U channel is based on a modeling approach that uses successive uniformly magnetized prisms. In lacustrine laminated sections, comparison between modeling results based on prisms of a constant thickness, on prisms determined from sedimentary facies and on prisms determined from XRF (X-Ray Fluorescence), data helps to understand the detrital vs. diagenetic history of the sedimentary succession.