Determining Magnetic Field Intensity and Direction From the Anisotropy of Magnetic Remanence in Sediments

Ostermeier, Felix K.; Gilder, Stuart A.; Wack, Michael R.; Ježek, Josef; He, Kuang; Finn, David (2026): Determining Magnetic Field Intensity and Direction From the Anisotropy of Magnetic Remanence in Sediments. Geochemistry, Geophysics, Geosystems, 27 (4): e2025GC012. ISSN 1525-2027

Abstract

Anisotropy of magnetic remanence (AMR) holds promise for quantifying relative paleointensity values from sedimentary rocks. A proof of concept was established for applied fields that exceeded the intensity of the geomagnetic field. Under Earth-like fields, large uncertainties necessitate the development of a new approach to improve the estimation of the anisotropy tensor. To this aim, we designed a numeral method that demonstrated the applicability and resolution needed to optimize the experimental protocol. Following this, we implemented a 30-position procedure for AMR measurements and compared the numerical and experimental data with a typically used, 12-position procedure. Redeposition experiments with sediments rich in single domain magnetite were carried out in fields with intensities of 0, 10, 50 and 100 μT; 25 individual samples were redeposited and measured at each field condition. The 30-position protocol better facilitates the isolation and resolution of the field-aligned prolate fabric (<3% of the total) from the oblate sedimentary fabric, and more so when applying tensor subtraction of the fabric obtained in a null field. Together with the high-resolution protocol and tensor subtraction method, we demonstrate that an anisotropy-based paleointensity deviates <10% relative to classical remanence based relative paleointensity in Earth-like fields ranging from 10 to 100 μT. Using a synthetic subtraction method, we show that remanence-based anisotropy precisely tracks the paleofield direction in rocks hosting detrital remanences, which is important when viscous or isothermal overprinting dominates the paleomagnetic vector.

• Dokumententyp: Artikel (LMU)
• Organisationseinheit (Fakultäten): 20 Geowissenschaften > Department für Geo- und Umweltwissenschaften
• DFG-Fachsystematik der Wissenschaftsbereiche: Naturwissenschaften
• DFG: Gefördert durch die Deutsche Forschungsgemeinschaft (DFG) - 518204048
• DFG: Gefördert durch die Deutsche Forschungsgemeinschaft (DFG) - 259336036
• DFG: Gefördert durch die Deutsche Forschungsgemeinschaft (DFG) - 521319783
• DFG: Gefördert durch die Deutsche Forschungsgemeinschaft (DFG) - 491502892