Comparison of Non-Heating Paleointensity Methods Using Synthetic and Natural Magnetite-Bearing Samples

Abstract:

Data of the strength of Earth’s magnetic field (paleointensity) in the geological past are crucial for understanding the geodynamo. Conventional paleointensity determination methods (e.g., the Thellier-Thellier method) require heating a sample to a high temperature in one or more steps. Consequently, many rocks are unsuitable for these methods due to a heating-induced experimental alteration. Alternative non-heating paleointensity methods are investigated to assess their effectiveness and reliability using synthetic magnetite-bearing samples of multiple grain sizes. Paleointensity was measured from synthetic magnetite-bearing samples using the Pseudo-Thellier, ARM, REM, REMc, REM’, and FORC methods. Natural samples from Lemptégy Volcano, France were also analyzed. For the synthetic samples, the Pseudo-Thellier and ARM methods produced the most accurate results, while for the natural samples only the Pseudo-Thellier method was able to produce a reasonable paleointensity estimate consistent with previous paleointensity data. The Pseudo-Thellier method appears to be the best alternative to the heating-based paleointensity methods.