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

Abstract

Tectonic plate motions are integral in shaping many aspects of Earth, including its thermal, geochemical, tectonic, biologic, climatic, and magnetic evolution. Understanding the history of plate motions is therefore directly relevant to a wide variety of research areas. Robust global plate reconstructions have been constructed back to the Jurassic on the basis of marine magnetic anomalies and hotspot tracks (e.g., Seton et al., 2012), but plate model development for earlier times is challenging due to the lack of preserved oceanic lithosphere. Paleomagnetic data offer a key constraint for plate motions, providing the only quantitative tool for plate modeling in pre-Jurassic times.Earth's magnetic field is dominated by a time-averaged dipole aligned with the planetary spin-axis (e.g., Creer et al., 1954), and when a tectonic plate moves with respect to that axis, the directions of the Earth's magnetic field observed locally on that plate change through time. When recorded in rocks, these temporal changes in magnetic direction provide a quantitative archive of a plate's kinematic history. For convenience, a plate can be treated as fixed, and the changing magnetic directions used to determine the apparent motion of the magnetic pole with respect to the plate can be expressed as an apparent polar wander path (APWP, Creer et al., 1954). Construction of an APWP requires a record of paleomagnetic data of various ages from the same rigid plate, which together can

Quantitative Analysis of Paleomagnetic Sampling Strategies

“…A recent approach to synthesize site data into apparent polar wander paths developed by Gallo et al. (2023) enabled the propagation of directional uncertainty using site level precision κ w estimated by multiple samples in a given site. This approach is not possible when applying a n 0 = 1 sampling strategy.…”