PhD Public Defense - 12 June 2020

Public PhD Defense - Matthias Sinnesael

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12 June 2020, 16:00 Central European Summer Time (Paris, Brussels)

“Astronomical cycle identification

New methodological approaches and application to high-resolution Ordovician stratigraphy”

Please find the link and instructions below

Agenda:

Introduction by the Chair of the jury

Presentation for the public (~40 min)

Questions by the jury

Questions by the audience (to be asked via chat, read by the Chair of the jury)

The jury retreats for deliberation

Return and decision of the jury on Teams meeting

Hopefully a reception can be organised once COVID-19 restrictions are lifted.

Supervisors:

- Prof. dr. P. Claeys (VUB, Belgium)

- Prof. dr. T. Vandenbroucke, (UGent, Belgium)

Jury:

- Prof. dr. S. Goderis (Chair, VUB, Belgium)

- Prof. dr. M. De Batist (Secretary, UGent, Belgium)

- Prof. dr. B. Cramer (The University of Iowa, USA)

- Prof. dr. L. Hinnov (George Mason University, USA)

- Prof. dr. K. Kuiper (VU Amsterdam, The Netherlands)

ABSTRACT:

The state of the Earth’s climate has changed in the past. These changes in climate often occurred on long time scales – thousands to even many millions of years. This is in contrast with the current-day fast global warming which is caused by the human-induced increase of certain gases in the atmosphere (CO2 or methane) which reinforce the greenhouse effect. Therefore, documenting the climate of the past is crucial to understand future climate changes and to better calibrate climate models.

We chose to study the Ordovician period (~485-444 million years ago) as it is particularly intriguing and contains crucial information on the processes behind rapid and brutal climate variability. The Ordovician period was characterized by CO2 concentrations several times higher than today and the virtual lack of vegetation on the continents. The largest fraction of developed life was still living in the oceans. Most of the land masses were located south of the equator and a gigantic ocean occupied the Northern Hemisphere. Another fascinating feature of the Ordovician is the evolution of warm conditions towards an intense period of glaciations.

We focused on the role of astronomical cycles as a climate forcing during the Ordovician. The orbit and orientation of the Earth relative to the Sun vary continuously in a very regular way. This variation changes climate as it controls the distribution of solar energy on the Earth’s surface through space and time. We used, and developed, different techniques to identify such cycles in the rock record. Because we studied very old rocks, we had to pay special care to how we approached this challenge. As a result, large parts of this thesis focus on methodological questions. How can we measure these astronomical cycles and test if they were really there?

This thesis explores ways of measuring the geochemical composition of rocks, how we can analyze those measured signals and what the reproducibility of these approaches is. We demonstrate that astronomically driven variations in solar irradiation are indeed traceable in Ordovician rocks. These findings result in a better insight into the causes, timing and duration of the Ordovician climatic events. Moreover, because of the very regular nature of theses cycles, we can construct very precise geological time scales which are unique so far back in time.

INSTRUCTIONS:

Ideally this event would have happened on campus followed by a reception. Given the COVID-19 situation, the public PhD defense will be held online using Microsoft Teams. This means that we will all be connected remotely from our homes/offices and not from the usual university setting.

- We will start promptly at 16:00 CEST. Please join 10-15 min earlier to make sure everything works accordingly.

- To join the event, click on this link. More information on how to join a Microsoft Teams meeting and instructional video can be found here.

- Please turn off your camera and microphone. Only the jury and the candidate should be visible and able to speak.

- There will also be the opportunity for the audience to ask questions. Questions can be asked throughout the presentation using the chat function. These will be read by the chair of the jury after the questions of the jury in chronological order as long as time permits. You may leave your email address so your answer can still be emailed to you if time runs out.

- During the retreat of the jury for deliberation, impressions of past fieldwork will be shared.

- After return of the jury, the final decision and proclamation is usually followed by a possibility to express reflections and acknowledgements.

- End of the event is estimated around 18:00 CEST.

Anchor 1

Public PhD Defense - Matthias Sinnesael

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12 June 2020, 16:00 Central European Summer Time (Paris, Brussels)

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