PhD defence: On pole position - new approaches to quantifying polar wander and relative paleomagnetic displacements

Paleomagnetism is the study of the direction of the past geomagnetic field recorded in rocks. Paleomagnetic data can be used to reconstruct the movement of tectonic plates through geological time. The reconstruction of the world’s geography in the past – called paleogeography – is essential input for many disciplines in the Earth Sciences, such as paleoclimatology, paleobiology and geodynamics. To track the position of continents relative to the Earth’s spin axis we typically use so-called apparent polar wander paths (APWPs), which are calculated from paleomagnetic data. However, traditional methods to calculate these do not consider some important uncertainties in the input data, limiting the accuracy and usefulness of paleogeographic reconstructions based on those APWPs.

This thesis investigates the sources of uncertainty in the data and develops a new approach that better takes these into account. In addition, we compiled a fully updated global paleomagnetic database and global model of relative plate tectonic motions. We present a new global APWP calculated using this method that has improved uncertainty quantification. This new path enables more accurate reconstruction of paleogeography and better determination of the motion of continents and plates through geological time. In addition, we present an open-source web application, APWP-online.org, that allows users to calculate APWPs and analyze paleomagnetic displacements using the new methodology. In the final chapter, we present new quantitative estimates of the rotation of the solid earth relative to the spin axis - called true polar wander. We discuss its implications for the workings of the Earth’s interior and future opportunities for understanding true polar wander on geological timescales.