A new understanding of the uplift and incision of the Colorado Plateau from classical and electron spin resonance thermochronology

Projektbeschreibung

Die Geschichte der Erosion des Colorado-Plateaus enträtseln

Orogene Hochebenen wie das Colorado-Plateau prägen regionale und globale Klimamuster auf besondere Weise. Ihre geologische Geschichte ist nach wie vor umstritten. Insbesondere das Colorado-Plateau mit seinen auffälligen Hochrelief-Canyons wirft Fragen nach den zeitlichen Abläufen und Prozessen auf, die für seine Hebung und Einschnitte verantwortlich sind. Das Team des Projekts PLATOCHRON wird mit Unterstützung der Marie-Skłodowska-Curie-Maßnahmen dazu beitragen, diese Ungewissheiten auszuräumen. Zu diesem Zweck werden fortgeschrittene thermochronologische Verfahren einschließlich Apatit-(U-Th-Sm)/He- und Spaltspurdaten sowie Elektronenspinresonanz eingesetzt, um die thermische Geschichte der Gesteine ausgewählter Canyons zu rekonstruieren sowie Zeiträume und Geschwindigkeiten des Canyoneinschnitts zu bestimmen. Dank dieser Ergebnisse wird es möglich sein, konkurrierende Theorien über die Hebung und Erosion des Plateaus zu überprüfen.

Ziel

High-standing orogenic plateaus are key features of most mountainous regions, and typically have profound regional, and in many cases global, impacts on atmospheric circulation and precipitation patterns. The Colorado Plateau is characterized by a low-relief surface at high elevation and deep canyon incision at the plateau margins. Although these canyons are key features of ecosystems and water resources, the chronology of the uplift and subsequent canyon incision remains debated. In addition, the relative importance of deep-seated processes, changes in paleogeography and climate, on the late geomorphologic evolution of the plateau remains controversial. Two endmember models of Grand Canyon incision have been proposed: a 80-60 Ma incision or a 6-5 Ma incision, the discrepancy between these models is partly related to limitations in conventional thermochronology techniques. This project will provide new constraints on the incision history of the canyons carved across the Colorado Plateau using an innovative set of thermochronometers. I will combine apatite (U-Th-Sm)/He and fission-track data to document the thermal history of rocks in Zion Canyon which has never been explored and infer the respective effects of erosion and regional magmatism on the thermal evolution of the lithosphere. Electron spin resonance (ESR) thermochronometry, a new thermochronometer sensitive to temperature ranging from 50 to 20˚C will be performed on the same samples and combined with thermo-kinematic modelling to decipher the timing and rate of canyon incision in Zion. Finally, I will apply ESR thermochronometry in selected canyons to decipher the timing of incision across the Colorado Plateau. Low-temperature thermochronology data, including ESR, will be integrated in a numerical model of the landscape evolution to test different processes (change in base level versus mantellic process) and associated scenarios for the Colorado Plateau uplift and incision.