Magnetic tracing of lost time in Cenozoic sediments: investigating dynamic topography of the Yellowstone plume, USA

Gerritsen, Dieke (2025): Magnetic tracing of lost time in Cenozoic sediments: investigating dynamic topography of the Yellowstone plume, USA. Dissertation, LMU München: Fakultät für Geowissenschaften

Abstract

Dynamic topography—vertical surface deflection caused by density variations and convective flow in the mantle—can profoundly reshape Earth’s surface. It generates long-wavelength uplift that can reactivate faults, reorganize drainage networks, and influence regional climate and the evolution of flora and fauna. Yet, the spatial and temporal development of dynamic topography remains difficult to constrain, and its effects on surface processes are still poorly understood. This thesis investigates the imprint of dynamic topography on the geological record, using the Yellowstone mantle plume in North America as a case study. We targeted three key regions in Montana, Wyoming, and Washington, each at a different distance from the plume center and reflecting different stages and expressions of uplift. These regions were selected for their well-preserved sedimentary successions that span the period before and after the eruption of the Columbia River Basalt at ~17 Ma. We collected over 2,000 oriented samples, conducted extensive rock and paleomagnetic analyses, and integrated these with stratigraphic, geochronological, and provenance data to constrain the timing, extent, and surface effects of plume-related uplift. In Montana, we identified the clearest evidence for dynamic topography. We precisely dated a regional unconformity at ~20 Ma using magnetostratigraphy in combination with published U-Pb ages. Across eight sedimentary sections covering ~40,000 km², we observed a sharp increase in magnetite concentration at this unconformity. In parallel, our compilation of detrital zircon data revealed a marked shift in provenance from predominantly Cretaceous to Miocene sources. Together, these observations suggest a westward migration of the North American drainage divide, interpreted as a surface response to dynamic uplift from the Yellowstone plume. In Wyoming, we detected a more gradual response. Our rock magnetic data show a steady increase in magnetite concentration in the upper Eocene, coinciding with increased input of Archean zircons. We interpret this as post-Laramide uplift and unroofing of the nearby Wind River Range, potentially reactivated by dynamic topography linked to lithospheric rebound or the arrival of the Yellowstone plume. In Washington, the results are more ambiguous. We observed a stepwise increase in magnetic mineral content in a section draining the Olympic Mountains. However, given the region’s complex tectonic setting, we attribute this signal to erosion of magnetite-rich basalts from the Siletzia terrane, rather than to dynamic topography. More detailed rock magnetic and sedimentological analyses are needed to test this interpretation. Our work shows that unconformities and associated shifts in magnetic mineralogy can reveal the surface expression of deep mantle processes. By integrating paleomagnetic, stratigraphic, and geochronologic datasets, we provide constraints on the spatial and temporal evolution of dynamic topography associated with the Yellowstone plume. These results provide valuable input for geodynamic and surface process models. Ultimately, this thesis contributes to a deeper understanding of how mantle dynamics shape Earth’s surface and, indirectly, the ecosystems and climates that respond to it.

• Dokumententyp: Dissertationen (Dissertation, LMU München)
• Themengebiete: 500 Naturwissenschaften und Mathematik ; 500 Naturwissenschaften und Mathematik > 550 Geowissenschaften
• Fakultäten: Fakultät für Geowissenschaften
• Sprache der Hochschulschrift: Englisch
• Datum der mündlichen Prüfung: 5. Dezember 2025
• 1. Bericht­erstatter:in: Gilder, Stuart