Evolution of the Solar System and micro/nanopalaeomagnetism

Recent “micro- and nanopalaeomagnetic” approaches are a promising way to obtain useful data from the early solar system through microscopic magnetic imaging techniques on meteorites. Magnetic records of meteorites give insight into the presence or absence of dynamos in extra-terrestrial bodies including the protoplanetary disk, the sun, the moon, other planets, as well as asteroids, which allows to conclude how and when these bodies formed. 

Extraterrestrial materials are, however, unlike any one found on Earth and currently, there is no consensus about the magnetic recording mechanism of these complex materials. I use theoretical and computational tools to assess how magnetic minerals in extraterrestrial materials record and preserve magnetisations that may give insight into the evolution of the solar system.

Origins of the Earth's Magnetic Field

The magnetic field of the Earth gives important insight into the formation of the Earth such as the evolution of the core, the question of how the Earth solidified and how it became a hospitable planet. Ultimately, even the evolution of life on Earth and/or other planets is critically dependent on the existence of a geomagnetic field which protects microorganisms from potentially deadly cosmic rays and possibly even the atmosphere from being blown away by the solar wind – a fate that occurred to Mars billions of years ago.

Currently, little is known about these questions – the only information we have comes from highly advanced novel palaeomagnetic methods which are subject to a heated debate: The first billion years of the Earth, the time when life first appeared, could only be studied through “single-silicate-crystal” works, but these have been called into doubt by some researchers, however.  My previous work assessed how reliable the most ideal of such “single-silicate-crystals”, which contain microscopic magnetic inclusions, preserve ancient magnetic fields. Often, however, magnetic structures in these crystals are complex and my present work focusses on how we can obtain insights into the earliest geomagnetic field from ‘less-than-ideal’ silicate crystals from a theoretical perspective.

Magnetic Dating of Catastrophic Events

We live in times of increasing vulnerability to extreme natural hazards, and growing conscience exists that our society remains insufficiently prepared to confront high-impact, low-probability natural catastrophes due to insufficient understanding of such events and their impacts. The key to accurately estimate the probability of an extreme natural hazard to occur in the near future lies in our ability to accurately date deposits of events such as tsunamis, storm floods, landslides, and earthquakes that occurred in the past, to reconstruct recurrence patterns. A number of different dating methods have been developed and are in use (e.g. radiometric, surface exposure, optically stimulated luminescence, etc.), but all have their particular limitations (e.g. with respect to the datable age range, the deposit's material, or external environmental factors) and there is no single method that can date all natural hazard deposits; and some cannot by dated by any of the available methods.

I am developing and testing a novel but promising dating method for natural hazards, based on magnetic records in rocks that are acquired post-emplacement of the rock during a natural hazard event: Microscopic magnetic inclusions in rocks normally carry a magnetization that is aligned with the geomagnetic north at the time of their formation. After a rock/boulder is deposited by a natural disaster, the orientation of this magnetization is no longer aligned northward. Over time, some of these grains re-orient their magnetization vector northward through a slow viscous process: a viscous remanent magnetization (VRM). Determining the progress of this VRM allows to estimate the time passed after deposition.

Case studies of this method during my PhD gave promising results and showed that “VRM geochronology” can be a viable order-of-magnitude dating tool. My current research focusses on improvements of the method, in particular with respect to rocks with complex magnetic mineralogies, the application of the method on a larger variety of deposit types (e.g. conglomerates), as well as on carrying out a larger number of case studies to assess the performance of the method.

Numerical models of sedimentary magnetism

Biogenic magnetic minerals are abundant in sediments and are highly sensitive indicators of past environmental conditions and climates, as well as the behaviour of the geomagnetic field and the geodynamo. Since magnetic properties are easy and fast to measure, they have therefore been proposed as a palaeoenvironmental proxy. Key to using sedimentary magnetism as a palaeoenvironmental proxy is the correct identification and characterization of biogenic magnetic minerals, amongst them so-called magnetosomes produced by magnetotactic bacteria (MTB), purely from magnetic measurements.

My research aims to do this through numerical micromagnetic models that allow to simulate the magnetic response of different morphologies and mineralogies of MTB. To date, this includes forward modelling of various MTB, and correlation of magnetic signals of MTB to microscopic imaging. Current and future research focusses on the effect that mechanical compression (compaction) of sediments has on magnetosome and other magnetic mineral morphology, such as chain collapse of magnetosomes. Understanding the effect of e.g. magnetosome chain collapse will not only help to improve the use of MTB as a palaeoenvironmental proxy, but will also allow to better understand magnetic remanence signals in sedimentary records. The latter is essential for use in magnetostratigraphic dating of sediments, for reconstruction of relative magnetic palaeointensities giving insight into the geodynamo, as well as for discriminating between depositional and post-depositional remanences and other re-magnetizations.

Complex Magnetic Mineralogies

In nature, both sedimentary and igneous rocks commonly contain a multitude of different magnetic minerals – in sediments mixtures of magnetic minerals are of great interest since each of them can possibly be used to trace different environmental or geographical sources, while in igneous rocks they play an important role in understanding the origins of magnetic remanence components and the tectonics and geodynamic implications.

Through numerical forward modelling, novel experimental protocols and theoretical work, I have developed new ways to detect, distinguish and separate signals from magnetic mineral mixtures. 

1. Berndt, T.A., Chang, L., Paterson, G. A.，& Cao, C. 2021."Experimental Test of the Cooling Rate Effect on Blocking Temperatures in Stepwise Thermal Demagnetisation." Geophysical Journal International 224 (2): 1116–1126. https://doi.org/10.1093/gji/ggaa514

2. Berndt, T. A., Chang, L. & Pei, Z.*(2020). Mind the gap: Towards a biogenic magnetite palaeoenvironmental proxy through an extensive finite-element micromagnetic simulation. Earth and Planetary Science Letters. https://doi.org/10.1016/j.epsl.2019.116010

3. Berndt, T. A., & Chang, L. (2019). Waiting for Forcot: Accelerating FORC Processing 100x using a Fast‐Fourier‐Transform Algorithm. Geochemistry, Geophysics, Geosystems. https://doi.org/10.1029/2019GC008380

4. Chang, L., Harrison, R. J., & Berndt, T. A. (2019). Micromagnetic simulation of magnetofossils with realistic size and shape distributions: Linking magnetic proxies with nanoscale observations and implications for magnetofossil identification. Earth and Planetary Science Letters. https://doi.org/10.1016/j.epsl.2019.115790

5. Chang, L., Harrison, R. J., Zeng, F., Berndt, T. A., Roberts, A. P., Heslop, D., & Zhao, X. (2018). Coupled microbial bloom and oxygenation decline recorded by magnetofossils during the Palaeocene-Eocene Thermal Maximum. Nature Communications, 9(4007), 1–9. https://doi.org/10.1038/s41467-018-06472-y

6. Berndt, T. A., Chang, L., Wang, S., & Badejo, S. (2018). Time-Asymmetric FORC Diagrams: A New Protocol for Visualizing Thermal Fluctuations and Distinguishing Magnetic Mineral Mixtures. Geochemistry, Geophysics, Geosystems, 19, 1–28. https://doi.org/10.1029/2018GC007669

7. Berndt, T. A., & Chang, L. (2018). Theory of stable multi-domain thermoviscous remanence based on repeated domain-wall jumps. Journal of Geophysical Research: Solid Earth, 123, 1–23. https://doi.org/10.1029/2018JB016816

8. Berndt, T. A., Paterson, G. A., Cao, C., & Muxworthy, A. R. (2017). Experimental test of the heating and cooling rate effect on blocking temperatures. Geophysical Journal International, 210(1), 255–269. https://doi.org/10.1093/gji/ggx153

9. Berndt, T. A., Ramalho, R. S., Valdez-Grijalva, M. A., & Muxworthy, A. R. (2017). Paleomagnetic field reconstruction from mixtures of titanomagnetites. Earth and Planetary Science Letters, 465, 70–81. https://doi.org/10.1016/j.epsl.2017.02.033

10. Berndt, T. A., & Muxworthy, A. R. (2017). Dating Icelandic glacial floods using a new viscous remanent magnetization protocol. Geology, 45(4), 339–342. https://doi.org/10.1130/G38600.1

11. Berndt, T. A., Muxworthy, A. R., & Fabian, K. (2016). Does size matter? Statistical limits of paleomagnetic field reconstruction from small rock specimens. Journal of Geophysical Research: Solid Earth, 121(1), 1–12. https://doi.org/10.1002/2015JB012441

12. Berndt, T. A., Muxworthy, A. R., & Paterson, G. A. (2015). Determining the magnetic attempt time τ0, its temperature dependence, and the grain size distribution from magnetic viscosity measurements. Journal of Geophysical Research: Solid Earth, 120. https://doi.org/10.1002/2015JB012283

13. Berndt, T. A., Ruiz-Martínez, V. C., & Chalouan, A. (2014). New constraints on the evolution of the Gibraltar Arc from palaeomagnetic data of the Ceuta and Beni Bousera peridotites (Rif, northern Africa). Journal of Geodynamics, 84, 19–39. https://doi.org/10.1016/j.jog.2014.09.014

*Students I (co)supervised.

Academic

Assistant Professor, Dept. Geophysics, Peking University (Since 2019)

Boya Post-doctoral Fellow, Dept. Earth and Space Science, Peking University (2017 – 2019)

Education

PhD Geophysics, Imperial College London (2016)

MSc Geophysics, Universidad Complutense de Madrid (2013)

BSc Physics, University of Southampton (2010)

Study abroad at Université Libre Brussels (2011)

Study abroad at University of Edinburgh (2009)

Study abroad at Jacobs University Bremen (2008)

Professional

Risk Management Consultant, d-fine Ltd, London (2016 – 2017)

Software Developer (part-time), Genese.de, Bremen (2007 – 2013)

Quality & Reliability Assurance Intern (SEM Lab), Texas Instruments, Munich (2008)

Software Developer (part-time), Rheinmetall, Bremen (2005 – 2006)

Freelance Software Developer, Reha-Haus Bremen (2003 – 2006)

Grants

Science & Technology Foundation Portugal Fellowship, declined by T.A.B. (1'400'000 CNY, 2019)

National Science Foundation China (Co-I) on biogenic magnetite, 41974074 (850'000 CNY, 2019)

China Postdoctoral Science Fund Magnetic Dating of Tsunamis, 2018M640019 (80'000 CNY, 2019)

Institute of Rock Magnetism Visiting Research Fellowship (33'000 CNY, 2017)

Boya post-doctoral fellowship by Peking University (370'000 CNY, 2017)

British Research Council Travel/research grant to CAS Beijing (24'000 CNY, 2015)

Institute of Rock Magnetism Visiting Research Fellowship (33'000 CNY, 2015)

IC Trust Conference Travel Grant to IUGG (Prague) by Imperial College (3'300 CNY, 2015)

Institute of Rock Magnetism Visiting Research Fellowship (33'000 CNY, 2014)

Summer School and Research Placement Grant by Imperial College (2'500 CNY, 2014)

Janet Watson PhD Scholarship by Imperial College Dept. Earth Science (400'000 CNY, 2013)

Teaching and Supervision

Supervision at Peking University

·        One international graduate student (J. Devienne) on micromagnetic models of Iron meteorites (Since 2020)

·        One graduate student (C. Han) on micromagnetic models of silicate inclusions (Since 2020)

Co-Supervision at Peking University

·        One graduate student (F. Bai) on micromagnetic models of silicate inclusions (2017 – 2020)

·        One undergraduate (Z. Pei) on micromagnetic models of magnetosomes (2018 – 2020)

Lectures at Peking University

·        Big Data Applications in Earth Sciences (MSc, since 2020)

·        Introductory Machine Learning for Earth Scientists (BSc, since 2020)

·        Rock Magnetism (MSc, co-taught, 4 lectures/year, 2017 – 2020)

·        Geodynamic Modelling (BSc, co-taught, 1 lecture, 2017)

Course instructor at Deutsche SchülerAkademie (DSA). 

DSA is a 2-week summer-school pro  gramme for talented high-school students in Germany to work on advanced academic topics, accompanied by a diverse extra-curricular programme.

·        Blockchain, Bitcoin and the Smart Economy (50 hours, 2019)

·        Algorithms in Artworks (Programming in the context of Arts, 50 hours, 2015)

·        Introduction to Chinese (extracurricular, 2015 & 2019)

·        Introduction to Video Production (extracurricular, 2019)

Geophysics Bootcamp (2014)
·        2-week MSc Geophysical Exploration programme: Leading GPS surveying team

Teaching Assistant at Imperial College (2013 – 2015)

·        Seismic techniques (MSc)

·        Numerical Methods 2 (PDEs in C++)

·        Geophysical Modelling (Python)

·        Fire and Ice (Ice sheet models)

·        Programming for Geoscientists (Python)

·        Advanced Programming for Geoscientists (C++)

Outreach Activities

·        Volunteer at UK Space Design Competition (2014)

·        Geoscience presentations at Queen Mary’s Grammar School (2014)

Skills

Languages English (fluent), German (native), Spanish (fluent), Chinese (advanced), French (basic)

Programming Matlab, Python, C++, C#, VB, SQL, LaTeX, Java, TypeScript

Software Word, Excel, PowerPoint, SVN, Git, Adobe Premiere, Illustrator, InDesign

Instruments MPMS, Princeton VSM, JR5, VFTB, 3-axis high-temperature VSM, Kappabridge, 2G SQUID, scanning electron microscopy, energy-dispersive x-ray spectroscopy, focussed ion beam, atomic force microscopy, scanning capacitance microscopy, XRF

Reviewer for Geochemistry, Geophysics, Geosystems; Journal of Geophysical Research: Solid Earth; Earth and Planetary Science Letters; Geophysical Journal International;

Thomas A. Berndt (Asst. Prof.)

Jose Devienne (PhD student)

韩晨 (Han Chen, PhD student)

*** Postgraduate and undergraduate projects available ***

*** Looking for motivated postdoctoral researchers ***

Forcot

Waiting for Forcot: Accelerating FORC Processing 100x using a Fast-Fourier-Transform Algorithm

Forcot is a new First-Order Reversal-Curve (FORC) processing software that uses a Fast-Fourier-Transform algorithm to accelerate smoothing significantly. Its aim is to provide as easy and frictionless a user-experience as possible to create print-quality FORC diagrams with minimum effort.

When using the software to produce figures, or when using any of the code, theory, figures, data, please cite the corresponding paper Berndt, T. A. & Chang, L. (2019). Waiting for Forcot: Accelerating FORC Processing 100x using a Fast-Fourier-Transform Algorithm. Geochemistry, Geophysics, Geosystems.

Download latest version of Forcot

For the Mac version, you may have to use the command sudo xattr -d com.apple.quarantine Forcot_MacInstaller_v1.x.x.app (replace x by version number) to allow installing the app. Alternatively, you can download the Matlab version (this requires the curve fitting toolbox, the image toolbox, and the statistics toolbox).