On Pole Position: Causes of Dispersion of the Paleomagnetic Poles Behind Apparent Polar Wander Paths.

Paleomagnetic poles used to compute apparent polar wander paths (APWPs) are strongly dispersed, which was recently shown to cause a large fraction (>50%) of these poles to be statistically distinct from the APWP to which they contributed, suggesting that current statistical approaches overestimate paleomagnetic resolution. Here, we analyze why coeval paleopoles are so dispersed, using the paleopoles behind the most recent global APWP and a compilation of paleomagnetic data obtained from <10 Ma volcanic rocks (PSV10). We find that paleopoles derived from sedimentary rocks, or from data sets underrepresenting paleosecular variation (PSV), are more dispersed and more frequently displaced. We show that paleopoles based on a smaller number of paleomagnetic sites are more dispersed than poles based on larger data sets, revealing that the degree to which PSV is averaged is an important contributor to the pole dispersion. We identify as a fundamental problem, however, that the number of sites used to calculate a paleopole, and thus the dispersion of coeval paleopoles, is essentially arbitrary. We therefore explore a different approach in which reference poles of APWPs are calculated from site‐level data instead of paleopoles, thereby assigning larger weight to larger data sets. We introduce a bootstrap‐based method for comparing a collection of paleomagnetic data with a reference data set on the same hierarchical level, whereby the uncertainty is weighted against the number of paleomagnetic sites. Finally, our study highlights that demonstrating smaller tectonic displacements requires larger paleomagnetic data sets, and that such data sets can strongly improve future APWPs. Plain Language Summary: Apparent polar wander paths (APWPs) are widely used to reconstruct the position of continents relative to the Earth's rotation axis. These paths are typically calculated by averaging paleomagnetic poles obtained from rocks of similar age. Although these poles are expected to be tightly grouped, they are strongly scattered. Notably, this causes >50% of the poles used in recent APWPs to be statistically different from the APWP itself. Here, we investigate to what extent errors in these poles may explain the observed scatter. We find that poles derived from sedimentary rocks are more scattered than those derived from igneous rocks. Also, poles based on smaller data sets are more dispersed than those based on larger data sets. Our analysis shows that the amount of paleomagnetic data used to determine a pole is often arbitrary. To overcome the subjectivity in pole calculation, we propose a new approach in which an APWP is calculated from individual data points instead of from paleopoles. This allows comparing paleomagnetic data on the same statistical level, and the development of APWPs in which larger data sets have larger weight. Our study thus emphasizes the value of collecting large paleomagnetic data sets, which may improve future APWPs. Key Points: Paleopoles do not average "out" paleosecular variation, which forms a first‐order contributor to the dispersion of coeval paleopolesThe number of sites used to compute a paleopole and the number of paleopoles calculated from a given data set is essentially arbitraryCalculating apparent polar wander paths from site‐level data instead of poles allows the weighting of uncertainties and the amount of data [ABSTRACT FROM AUTHOR]