Periodic Reporting for period 1 - PLATOCHRON (A new understanding of the uplift and incision of the Colorado Plateau from classical and electron spin resonance thermochronology)
Periodo di rendicontazione: 2023-07-01 al 2025-06-30
Sintesi del contesto e degli obiettivi generali del progetto
Orogenic plateaus are key features of the Earth’s surface with average elevations of several kilometres, low relief surfaces and arid climate. They have a strong impact on atmospheric circulation and precipitation patterns, and thus on the erosive capacity of rivers. Continental plateaus show similarities in crustal thickness, heat flow, high elevation, and complex interactions between tectonics and climate at their margins. Although orogenic plateaus have been the subject of many geophysical and geological studies, the role of mantellic processes and magmatism on uplift and the contribution of surface processes on the relief evolution of plateau margins is actively debated. The Colorado Plateau is a typical continental orogenic plateau characterized by a low-relief surface at high elevation, the plateau is marginally incised by outstanding canyons including the Grand Canyon and Zion Canyon. Although canyons are key features of ecosystems and water resources across the Colorado Plateau and form some of the most dramatic features on earth, the chronology of plateau uplift, subsequent canyon incision and the controlling processes remain debated.
This project will focus on landscape evolution across the Colorado Plateau in relation to forcing mechanisms including regional uplift, mantle dynamics, magmatism, local tectonics and climate change during the Cenozoic. I will provide new quantitative constraints on the canyon incision history and potential spatial variability across the Colorado Plateau using an innovative thermochronometer. Ultimately this project will provide a new understanding of processes driving orogenic plateau uplift and canyon incision. PLATOCHRON addresses 3 objectives:
1) WP1: Determine the respective influence of surface erosion and Cenozoic magmatism on the thermal evolution of the upper crust along the western margin of the Colorado Plateau
2) WP2: Demonstrate the potential of ESR thermochronometry to document rock cooling related to canyon incision and decipher the incision timing and rate of Zion Canyon.
3) WP3: Provide a new insight on the timing of canyon incision (80-60 vs. 6-5 Ma incision) and pin-point processes controlling recent canyon incision using new incision constraints from ESR thermochronology and landscape evolution modelling.
This project will focus on landscape evolution across the Colorado Plateau in relation to forcing mechanisms including regional uplift, mantle dynamics, magmatism, local tectonics and climate change during the Cenozoic. I will provide new quantitative constraints on the canyon incision history and potential spatial variability across the Colorado Plateau using an innovative thermochronometer. Ultimately this project will provide a new understanding of processes driving orogenic plateau uplift and canyon incision. PLATOCHRON addresses 3 objectives:
1) WP1: Determine the respective influence of surface erosion and Cenozoic magmatism on the thermal evolution of the upper crust along the western margin of the Colorado Plateau
2) WP2: Demonstrate the potential of ESR thermochronometry to document rock cooling related to canyon incision and decipher the incision timing and rate of Zion Canyon.
3) WP3: Provide a new insight on the timing of canyon incision (80-60 vs. 6-5 Ma incision) and pin-point processes controlling recent canyon incision using new incision constraints from ESR thermochronology and landscape evolution modelling.
Lavoro eseguito dall’inizio del progetto fino alla fine del periodo coperto dalla relazione e principali risultati finora ottenuti
WP1: AFT and AHe dating combined with thermal modelling using stratigraphic data from Zion Canyon
WP1 focused on constraining the impact of mid-Cenozoic magmatic activity on the geothermal gradient and on quantifying late Cenozoic exhumation rates of Zion Canyon (Utah, USA), located along the western margin of the Colorado Plateau. To achieve this, we applied apatite fission-track (AFT) and apatite (U-Th-Sm)/He (AHe) thermochronology, combined with inverse thermal modelling, to rock samples collected within the canyon. Both thermochronometric systems point to a phase of reheating during the Miocene. During this event, the lower sample experienced a significant temperature increase, which may reflect a rise in the geothermal gradient—potentially linked to mantle upwelling. This interpretation aligns with the presence of relatively young basaltic volcanism in the area, suggesting that magmatic activity could have influenced the region’s thermal history. Despite the modest depth of the canyon, the elevated local geothermal gradient allows low-temperature thermochronometers to record the timing of incision by the Virgin River. Thermochronological data indicate a cooling beginning in the late Miocene, which likely reflects rock exhumation driven by uplift along the edge of the Colorado Plateau. When combined with existing geological cross-sections, geophysical evidence, and models of surface uplift, our findings point to the incision of Zion Canyon as a response to mantle-driven uplift during the Miocene. Later tectonic activity, particularly movement along the Hurricane fault, may have enhanced both uplift and incision in the region. This work will be integrated with data from the Grand Canyon and other regional landforms to provide a broader context for understanding canyon incision across the western United States.
WP2: Electron spin resonance (ESR) thermochronometry and thermo-kinematic modelling in Zion area
WP2 focused on constraining the rates of incision of Zion Canyon (Utah, USA) over the Quaternary. To achieve this, we applied ESR thermochronology to rock samples collected within Zion Canyon.
ESR dating is a trapped-charge dating method that directly measures the concentration of trapped electrons in the mineral lattice of quartz (Rink, 1997). Natural ESR signals of the Ti and Al centers were measured within a single spectrum. An ESR single aliquot regenerative (SAR) dose protocol using X-ray irradiation was used for the construction of the dose response curves (Tsukamoto et al., 2015). Samples collected from the canyon bottom retained non saturated ESR signals, indicative of recent cooling associated with canyon incision. Isothermal decay measurements allowed to determine the thermal sensitivity of each sample and the cooling rate experienced by the samples. These results provide new constraints on Quaternary incision rates in Zion and complement the thermochronological data obtained during WP1. ESR-derived cooling rates will be compared to Quaternary incision rates obtained through geomorphic analyses to evaluate their consistency and refine constraints on late-stage exhumation. These results will also be integrated with apatite 4He/3He thermochronology from the Grand Canyon to inform the timing and mechanisms of incision along the western margin of the Colorado Plateau. Ultimately, this will provide constraints on the timing of regional uplift and the timing of fluid flow reduction, and the associated bleaching of the upper Navajo Sandstone.
WP3: Thermochronological Constraints on Thermal History and Incision Rates in the Colorado Plateau Region
WP3 focused on (i) reconstructing the thermal histories and associated changes in geothermal gradient and exhumation of Oak Creek Canyon (Arizona, USA) and the Black Canyon of the Gunnison (Colorado, USA), and (ii) quantifying Quaternary incision rates in the Grand Canyon and the Black Canyon. To address these objectives, we combined classical low-temperature thermochronology (AFT and AHe) with emerging electron spin resonance (ESR) thermochronology, supported by inverse thermal modelling.
Sampling permits were successfully obtained for all relevant locations, and targeted field campaigns were conducted across key sites, including the Grand Canyon, Oak Creek Canyon, Black Canyon, and additional localities across the Colorado Plateau. New AFT and AHe data were acquired from previously undocumented sites in Oak Creek Canyon and the Black Canyon following the methods used in WP1, filling important spatial gaps in the regional thermochronological dataset.
Thermochronological data from Oak Creek Canyon predominantly record old cooling ages, with some partially reset AHe ages. In the Black Canyon, the thermochronological data reveal several cooling phases. These data offer a unique opportunity to isolate and assess the relative importance of these three exhumation events in the area.
ESR samples were collected from both the Grand Canyon and the Black Canyon and are currently undergoing preparation following the approach used in WP2. Measurement and analysis of these samples will be carried out in the next phase of the project.
WP1 focused on constraining the impact of mid-Cenozoic magmatic activity on the geothermal gradient and on quantifying late Cenozoic exhumation rates of Zion Canyon (Utah, USA), located along the western margin of the Colorado Plateau. To achieve this, we applied apatite fission-track (AFT) and apatite (U-Th-Sm)/He (AHe) thermochronology, combined with inverse thermal modelling, to rock samples collected within the canyon. Both thermochronometric systems point to a phase of reheating during the Miocene. During this event, the lower sample experienced a significant temperature increase, which may reflect a rise in the geothermal gradient—potentially linked to mantle upwelling. This interpretation aligns with the presence of relatively young basaltic volcanism in the area, suggesting that magmatic activity could have influenced the region’s thermal history. Despite the modest depth of the canyon, the elevated local geothermal gradient allows low-temperature thermochronometers to record the timing of incision by the Virgin River. Thermochronological data indicate a cooling beginning in the late Miocene, which likely reflects rock exhumation driven by uplift along the edge of the Colorado Plateau. When combined with existing geological cross-sections, geophysical evidence, and models of surface uplift, our findings point to the incision of Zion Canyon as a response to mantle-driven uplift during the Miocene. Later tectonic activity, particularly movement along the Hurricane fault, may have enhanced both uplift and incision in the region. This work will be integrated with data from the Grand Canyon and other regional landforms to provide a broader context for understanding canyon incision across the western United States.
WP2: Electron spin resonance (ESR) thermochronometry and thermo-kinematic modelling in Zion area
WP2 focused on constraining the rates of incision of Zion Canyon (Utah, USA) over the Quaternary. To achieve this, we applied ESR thermochronology to rock samples collected within Zion Canyon.
ESR dating is a trapped-charge dating method that directly measures the concentration of trapped electrons in the mineral lattice of quartz (Rink, 1997). Natural ESR signals of the Ti and Al centers were measured within a single spectrum. An ESR single aliquot regenerative (SAR) dose protocol using X-ray irradiation was used for the construction of the dose response curves (Tsukamoto et al., 2015). Samples collected from the canyon bottom retained non saturated ESR signals, indicative of recent cooling associated with canyon incision. Isothermal decay measurements allowed to determine the thermal sensitivity of each sample and the cooling rate experienced by the samples. These results provide new constraints on Quaternary incision rates in Zion and complement the thermochronological data obtained during WP1. ESR-derived cooling rates will be compared to Quaternary incision rates obtained through geomorphic analyses to evaluate their consistency and refine constraints on late-stage exhumation. These results will also be integrated with apatite 4He/3He thermochronology from the Grand Canyon to inform the timing and mechanisms of incision along the western margin of the Colorado Plateau. Ultimately, this will provide constraints on the timing of regional uplift and the timing of fluid flow reduction, and the associated bleaching of the upper Navajo Sandstone.
WP3: Thermochronological Constraints on Thermal History and Incision Rates in the Colorado Plateau Region
WP3 focused on (i) reconstructing the thermal histories and associated changes in geothermal gradient and exhumation of Oak Creek Canyon (Arizona, USA) and the Black Canyon of the Gunnison (Colorado, USA), and (ii) quantifying Quaternary incision rates in the Grand Canyon and the Black Canyon. To address these objectives, we combined classical low-temperature thermochronology (AFT and AHe) with emerging electron spin resonance (ESR) thermochronology, supported by inverse thermal modelling.
Sampling permits were successfully obtained for all relevant locations, and targeted field campaigns were conducted across key sites, including the Grand Canyon, Oak Creek Canyon, Black Canyon, and additional localities across the Colorado Plateau. New AFT and AHe data were acquired from previously undocumented sites in Oak Creek Canyon and the Black Canyon following the methods used in WP1, filling important spatial gaps in the regional thermochronological dataset.
Thermochronological data from Oak Creek Canyon predominantly record old cooling ages, with some partially reset AHe ages. In the Black Canyon, the thermochronological data reveal several cooling phases. These data offer a unique opportunity to isolate and assess the relative importance of these three exhumation events in the area.
ESR samples were collected from both the Grand Canyon and the Black Canyon and are currently undergoing preparation following the approach used in WP2. Measurement and analysis of these samples will be carried out in the next phase of the project.
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WP1 successfully applied AFT and AHe thermochronology combined with thermal modelling to constrain the thermal and exhumation history of Zion Canyon. The data reveal a Miocene reheating event likely linked to increased geothermal gradients from mantle upwelling, consistent with regional basaltic volcanism. Cooling beginning in the late Miocene is interpreted as evidence of rock exhumation associated with uplift along the Colorado Plateau margin. These findings provide compelling evidence for a mantle-driven component in canyon incision and regional uplift.
Impact: The results from this work provide valuable insights into how mantle-driven processes influence tectonic uplift and landscape evolution along plateau margins. By demonstrating the effectiveness of low-temperature thermochronometry in regions with elevated geothermal gradients, this study enhances our ability to resolve shallow crustal dynamics. Moreover, it establishes a robust thermochronological framework that enables direct regional comparisons with other major canyon systems, such as the Grand Canyon, offering a broader perspective on incision and uplift across the Colorado Plateau.
WP2 introduced ESR thermochronology to quantify Quaternary incision rates in Zion Canyon. Non-saturated ESR signals in quartz samples from the canyon floor indicate recent cooling associated with ongoing incision. The integration of isothermal decay measurements allows for direct estimation of cooling rates, offering an independent proxy for recent exhumation. These results complement the AFT/AHe data from WP1 and enable cross-validation with geomorphic estimates of erosion.
Impact: This work demonstrates the potential of ESR thermochronology as a powerful tool for resolving Quaternary exhumation in steep and rapidly eroding landscapes. By bridging the gap between traditional thermochronometric techniques and surface-process modelling, it offers a novel approach to quantifying recent cooling and incision. The improved temporal resolution provided by ESR enhances our ability to constrain late-stage exhumation, contributing to more detailed and accurate models of landscape evolution.
WP3 broadened the geographic scope to include Oak Creek Canyon, the Black Canyon, and additional Grand Canyon sites. It successfully combined AFT, AHe, and ESR techniques to reconstruct thermal histories and assess spatial variability in exhumation and incision rates across the plateau. Early findings suggest multiple exhumation phases in the Black Canyon and largely unreset ages in Oak Creek Canyon, indicating regional heterogeneity in thermal and tectonic history. ESR samples are currently being processed to extend Quaternary constraints in these areas.
Impact: This research significantly expands thermochronological coverage across the Colorado Plateau, helping to close key spatial data gaps. By integrating new data from multiple canyon systems, it enables a more comprehensive, regional-scale understanding of differential uplift and incision histories. These insights contribute to broader geodynamic models, improving our understanding of lithospheric evolution, the interplay between climate and erosion, and the long-term development of continental topography.
Key Needs for Further Uptake and Success
To ensure further uptake and success, it is essential to systematically integrate ESR, AHe, and AFT data with geomorphic and geophysical datasets, allowing for robust validation of thermal histories across different timescales. Cross-comparisons with 4He/3He thermochronometry can further refine temporal constraints and improve resolution. Automating ESR measurements would significantly increase data throughput and enable broader application of the method across diverse settings.
Impact: The results from this work provide valuable insights into how mantle-driven processes influence tectonic uplift and landscape evolution along plateau margins. By demonstrating the effectiveness of low-temperature thermochronometry in regions with elevated geothermal gradients, this study enhances our ability to resolve shallow crustal dynamics. Moreover, it establishes a robust thermochronological framework that enables direct regional comparisons with other major canyon systems, such as the Grand Canyon, offering a broader perspective on incision and uplift across the Colorado Plateau.
WP2 introduced ESR thermochronology to quantify Quaternary incision rates in Zion Canyon. Non-saturated ESR signals in quartz samples from the canyon floor indicate recent cooling associated with ongoing incision. The integration of isothermal decay measurements allows for direct estimation of cooling rates, offering an independent proxy for recent exhumation. These results complement the AFT/AHe data from WP1 and enable cross-validation with geomorphic estimates of erosion.
Impact: This work demonstrates the potential of ESR thermochronology as a powerful tool for resolving Quaternary exhumation in steep and rapidly eroding landscapes. By bridging the gap between traditional thermochronometric techniques and surface-process modelling, it offers a novel approach to quantifying recent cooling and incision. The improved temporal resolution provided by ESR enhances our ability to constrain late-stage exhumation, contributing to more detailed and accurate models of landscape evolution.
WP3 broadened the geographic scope to include Oak Creek Canyon, the Black Canyon, and additional Grand Canyon sites. It successfully combined AFT, AHe, and ESR techniques to reconstruct thermal histories and assess spatial variability in exhumation and incision rates across the plateau. Early findings suggest multiple exhumation phases in the Black Canyon and largely unreset ages in Oak Creek Canyon, indicating regional heterogeneity in thermal and tectonic history. ESR samples are currently being processed to extend Quaternary constraints in these areas.
Impact: This research significantly expands thermochronological coverage across the Colorado Plateau, helping to close key spatial data gaps. By integrating new data from multiple canyon systems, it enables a more comprehensive, regional-scale understanding of differential uplift and incision histories. These insights contribute to broader geodynamic models, improving our understanding of lithospheric evolution, the interplay between climate and erosion, and the long-term development of continental topography.
Key Needs for Further Uptake and Success
To ensure further uptake and success, it is essential to systematically integrate ESR, AHe, and AFT data with geomorphic and geophysical datasets, allowing for robust validation of thermal histories across different timescales. Cross-comparisons with 4He/3He thermochronometry can further refine temporal constraints and improve resolution. Automating ESR measurements would significantly increase data throughput and enable broader application of the method across diverse settings.