Scanning SQUID microscopy of a ferromanganese crust from the northwestern Pacific: Submillimeter scale magnetostratigraphy as a new tool for age determination and mapping of environmental magnetic parameters

Ferromanganese crusts record long-term deep-sea environmental changes. Thus, providing their reliable high-resolution age models is important. We applied a magnetostratigraphic technique to estimate the growth rate of a ferromanganese crust using scanning SQUID (superconducting quantum interference device) microscope (SSM). SSM is designed to map the magnetic field across thins sections with sub-millimeter resolution. The crust sample was taken from the Takuyo–Daigo Seamount, northwestern Pacific, and recorded a limited supply of dust and sediment from continents. After drift correction and removal of spike noises, the magnetic field values were stacked within the areas of high signal-to-noise ratios. By correlating the obtained profiles with a standard geomagnetic polarity timescale, we obtained an average growth rate of 3.37 ± 0.06 mm/m.y., which is consistent with that obtained by 10Be/9Be geochronology (2.93 ± 0.15 mm/m.y.). S-ratio mapping shows low values after ~3 Ma, associated with voids between columnar structures.