Postdoctoral position in Paleomagnetism

Universite de Montpellier; France; Sur place; EUR 20 000 - 40 000; Plein temps

Résumé du poste

A leading French research university is seeking a postdoctoral researcher in Paleomagnetism. This role involves obtaining paleointensity data and analyzing rock samples to enhance understanding of the Earth's magnetic field. The candidate must hold a PhD and possess strong communication skills in English and Portuguese. The position offers a monthly salary ranging from €2,200 to €2,380 and requires full-time dedication. The research will contribute to significant advancements in geophysical studies.

Qualifications

• Previous experience in paleointensity/paleomagnetism is highly appreciated.
• Candidates must be of any nationality.

Responsabilités

• Obtain new paleointensity data for Meso-Neoproterozoic geological units.
• Test bias between total rock and single crystal approach.
• Analyze rock samples for paleointensity data.

Connaissances

Paleomagnetism

Thermoremanent magnetization

English communication

Portuguese communication

Formation

PhD degree

Description du poste

Organisation/Company Universite de Montpellier Department Human Resources Research Field Geosciences » Geology Environmental science » Earth science Researcher Profile Recognised Researcher (R2) Positions Postdoc Positions Country France Application Deadline 12 Dec 2025 - 23:59 (Europe/Paris) Type of Contract Temporary Job Status Full-time Is the job funded through the EU Research Framework Programme? Horizon Europe Reference Number 2026-R0058 Is the Job related to staff position within a Research Infrastructure? No

Offer Description

Main Mission

The Earth's magnetic field (EMF) plays a key role in understanding the evolution of the planet, its climate, and its habitability over the past 4.5 billion years (Shahar et al. 2019). Paleomagnetism, which allows us to study past variations of the EMF, relies on the ability of rocks to acquire a thermoremanent magnetization that remains stable over time. Paleointensity, which measures the intensity of Earth's magnetic field recorded in ancient rocks, has deepened our knowledge of the variations in our planet’s magnetic shield and the evolution of Earth's core and geodynamo.

However, extracting paleointensity data from Precambrian rocks is extremely challenging. A rock typically contains a mixture of magnetic grains of different sizes and compositions, which may have undergone thermal or chemical transformations after their formation (e.g., metamorphism, hydrothermal alteration), potentially biasing measurements (Tauxe et al. 2021).

The single-crystal paleointensity technique, which involves analyzing individual millimeter-sized silicate crystals in rock samples, offers a promising approach for obtaining more precise and reliable data on past magnetic field intensity compared to conventional whole-rock methods (Cottrell and Tarduno 2000; Tarduno 2009). This method presents two main advantages: (i) silicate crystals act as protective capsules for millions of magnetic inclusions within the crystal, shielding them from alteration, and (ii) due to their size, these magnetite inclusions are generally in a single-domain to pseudo-single-domain state (<1 µm – 30 nm) and serve as excellent recorders of the EMF. Although this technique emerged in the early 2000s, the debate between "single-crystal" and "whole-rock" paleointensity measurements remains unresolved in 2025! This is partly because, until recently, very few laboratories worldwide had access to ultra-sensitive magnetometers capable of measuring the extremely weak magnetization of these small crystals, making it difficult to reproduce results. We are currently in a transition period marked by the rise of next-generation ultra-sensitive quantum magnetometers, with the only model in France recently installed at Géosciences Montpellier.

Activities

PhD. objectives and methodology

• The specific objectives of this postdoctoral fellowship are:
• 1. Obtain new paleointensity data for Meso-Neoproterozoic geological units (~1100 Ma - 535 Ma).
• 2. Test a potential bias between the "total rock" approach and the "single crystal" approach on these Meso-Neoproterozoic units. Evaluate the advances of the single-crystal technique and the problems associated with its use (anisotropy, etc.).

The research work will be based firstly on the already rock collection of samples available at Géosciences Montpellier. International paleomagnetic expeditions could be organized to extend such collections funded by the European UBEICH project.

Scientific Impact and Perspectives

The results of this postdoctoral fellowship could considerably improve our understanding of the dynamics of the Earth's magnetic field during the Neoproterozoic. By refining the resolution of paleointensity data, the single-crystal approach could offer new insights into the evolution of the Earth's core. Furthermore, this research could have implications beyond the strict confines of geophysics, notably in paleoclimatology, geodynamics and planetary magnetism.

References

1. Cottrell, R.D. and Tarduno, J.A. 2000. In search of high‑fidelity geomagnetic paleointensities: A comparison of single plagioclase crystal and whole rock Thellier‑Thellier analyses. Journal of Geophysical Research: Solid Earth, 105, 23579-23594.
2. Hawkins, L.M.A., Grappone, J.M. et al. 2021. Intensity of the Earth's magnetic field: Evidence for a Mid‑Paleozoic dipole low. Proceedings of the National Academy of Sciences, 118, e2017342118, https://doi.org/10.1073/pnas.2017342118.
3. Lloyd, S., Biggin, A.J., Paterson, G. and McCausland, P. 2022. Extremely weak early Cambrian dipole moment similar to Ediacaran: Evidence for long-term trends in geomagnetic field behaviour? Earth and Planetary Science Letters, 595, 117757, https://doi.org/10.1016/j.epsl.2022.117757.
4. Smirnov, A.V., Kulakov, E.V., Foucher, M.S. and Bristol, K.E. 2017. Intrinsic paleointensity bias and the long‑term history of the geodynamo. Science Advances, 3, e1602306.
5. Tauxe, L., Santos, C.N., Cych, B., Zhao, X., Roberts, A.P., Nagy, L. and Williams, W. 2021. Understanding Nonideal Paleointensity Recording in Igneous Rocks: Insights From Aging Experiments on Lava Samples and the Causes and Consequences of “Fragile” Curvature in Arai Plots. Geochemistry, Geophysics, Geosystems, 22, e2020GC009423, https://doi.org/10.1029/2020GC009423.

Salary and Candidate Requirements

The net monthly salary is between €2,200 and €2,380

The candidate will join a group of researchers active at Géosciences Montpellier in Paleomagnetism and Rock Magnetism. Previous experience in paleointensity/paleomagnetism will be highly appreciated. Candidates can be of any nationality. Candidates must hold a PhD degree. As this is an international project, the candidate's ability to communicate in English and Portuguese is an advantage.