magnetite; magnetic fabric; paleomagnetism; NRM deflection; hematite; magnetic mineralogy; anisotropy corrections
Biedermann Andrea R, Jackson Mike, Bilardello Dario, Feinberg Joshua M (2019), Anisotropy of (partial) isothermal remanent magnetization: DC-field-dependence and additivity, in Geophysical Journal International
Biedermann Andrea R., Bilardello Dario, Jackson Mike, Tauxe Lisa, Feinberg Joshua M. (2019), Grain-size-dependent remanence anisotropy and its implications for paleodirections and paleointensities – Proposing a new approach to anisotropy corrections, in Earth and Planetary Science Letters
, 512, 111-123.
Biedermann A.R., Jackson M., Bilardello D., Feinberg J.M., Brown M.C., McEnroe S.A. (2017), Influence of static alternating field demagnetization on anisotropy of magnetic susceptibility: Experiments and implications, in Geochemistry, Geophysics, Geosystems
Biedermann A.R. (2017), Towards a holistic understanding of complex magnetic fabrics
, University of Minnesota Press, Minneapolis, USA.
Paleomagnetic studies define a rock’s magnetic history to make paleogeographic reconstructions. The magnetization in a rock can be used to estimate the intensity and direction of the geomagnetic field at the time it was acquired. However, rock deformation or compaction during lithification can lead to a statistical alignment of the ferromagnetic grains’ easy magnetization axes/planes, thus causing deflection of the natural remanent magnetization (NRM). In this case, neither the paleofield direction nor its intensity are recorded accurately. If not accounted for, NRM deflection can cause major problems for paleogeographic reconstructions or the construction of apparent polar wander paths from paleomagnetic studies. Several correction techniques have been developed, but all have weaknesses and no established procedure exists to date. We propose that it is necessary to (1) determine which mineral is responsible for the remanent magnetization in a rock and (2) isolate the component of anisotropy related to this mineral for a correction. We will conduct a combined rock, paleomagnetic and magnetic fabric study on samples containing both magnetite and hematite and develop a best-practice protocol for isolating the anisotropy due to the remanence carrier, which can then be used to correct for NRM deflection. This will benefit not only the paleomagnetism and archeomagnetism communities, but also exploration scientists who model magnetic anomalies, and also face the problem that magnetization can be tilted away from the magnetic field direction.