Embracing Uncertainty to Resolve Polar Wander: A Case Study of Cenozoic North America

Our understanding of Earth's paleogeography relies heavily on paleomagnetic apparent polar wander paths (APWPs), which represent the time-dependent position of Earth's spin axis relative to a given block of lithosphere. However, conventional approaches to APWP construction have significant limitations. First, the paleomagnetic record contains substantial noise that is not integrated into APWPs. Second, parametric assumptions are adopted to represent spatial and temporal uncertainties even where the underlying data do not conform to the assumed distributions. The consequences of these limitations remain largely unknown. Here, we address these challenges with a bottom-up Monte Carlo uncertainty propagation scheme that operates on site-level paleomagnetic data. To demonstrate our methodology, we present an extensive compilation of site-level Cenozoic paleomagnetic data from North America, which we use to generate a high-resolution APWP. Our results demonstrate that even in the presence of substantial noise, polar wandering can be assessed with unprecedented temporal and spatial resolution.Plain Language Summary Records of Earth's ancient magnetic field preserved in rocks provide valuable information for understanding past tectonic plate motions. These "paleomagnetic" records are collected from individual rock samples and subsequently grouped to develop global-scale paths called apparent polar wander (APW) paths. However, the standard methods for analyzing and grouping paleomagnetic data are limited in the way they propagate and quantify uncertainties, and the consequences of these limitations are not known. In this study, we address these limitations through the introduction of a new methodological approach, which we use to study a large data set of paleomagnetic data from North America for the past 60 million years. We demonstrate that through our new methodology it is possible to generate APW paths with unprecedented spatial and temporal resolution, which may offer new insights into Earth's deep time evolution.