Response of remanent magnetization to deformation in geological processes using 3D-printed structures

Palaeogeographic reconstructions and construction of apparent polar wander paths are dependent on having reliable palaeomagnetic directions. The importance of inclination flattening in biasing the palaeomagnetic record has been debated for over 60 yrs. Correction for this effect often assumes that the palaeomagnetic vector deforms as a passive line. In a novel approach using 3D printed analogue rocks, we revisit the question of how a palaeomagnetic vector responds to deformation, specifically compaction. Maghaemite nanoparticles were mixed in the printing resin with a concentration of 0.15 wt. %, and five series of cylinders with 1 cm height and diameter were printed with porosities between 0% and 20%. Samples were given an anhysteretic remanent magnetization, and were subjected subsequently to incremental compaction. The magnetic fabric shows an initially weak compaction in the printing plane that becomes larger with increased compaction. The palaeomagnetic inclination changes according to the strain that the sample undergoes, and the amount of deflection is less than predicted by a passive line model of deformation. Our results demonstrate that using a single correction factor for inclination flattening is questionable, and show the need for a method that considers how the rock deforms. Further we demonstrate the usefulness of 3D printed analogue rock, which can inspire more realistic methods to correct for inclination flattening. (c) 2020 Elsevier B.V. All rights reserved.