Audrey Margirier
RECENT PROJECTS
Luminescence dating of englacial transport time of rock debris
We used luminescence rock surface burial dating to constrain the englacial transport time of debris within an alpine debris-covered glacier. Our results, and the application of luminescence rock surface burial dating to englacially transported debris, will enhance understanding of the dynamics of debris-covered glaciers and inform the use of glacier models for debris covered glaciers.
Main collaborators: G. King, A. Rowan
Zion Canyon incision history
The processes controlling the formation of canyons accross the Colorado Plateau are not well understood, and the relative importance of tectonics, geological inheritance and climate remains debated. This project will provide a first insight on the timing and rate of landscape evolution in Zion with a focus on the late Cenozoic erosion history. Our study will provide new thermochronological data that will allow us to determine the timing of Zion Canyon incision and assess the influences of regional tectonics and climate in this region.
Main collaborator: P. Reiners
Time scale for orogenic growth and decay
The time it takes for a mountain belt to grow and reach its maximum topography is one of its fundamental characteristics. Based on measurements of the mountain height, estimates of current erosion rate and of the effective elastic thickness of the lithosphere we propose a method to estimate this response time.
PI: J. Braun
PAST PROJECTS
Exhumation of the Ecuadorian Andes
My research at the University of Arizona and the University of Potsdam addressed the processes contributing to topography building in the northern Andes with a focus on the role of strike slip faulting and subduction processes in Ecuadorian Andes. I tackled this issue with low-temperature thermochronology and numerical modelling.
Main collaborators: M. Strecker, P. Reiners, I. Casado, A.Alvarado
Incision of the Mekong River
The incision of the Mekong River in Southeast Tibet has been linked to both tectonics and climate. This project reports new apatite (U-Th-Sm)/He and fission-track data from the middle Mekong River valley and the adjacent Kawagebo Massif, which forms the edge of the high plateau. Combined with thermal modeling these thermochronological data allow constraining the exhumation history of this region and to discuss the potential tectonic and climatic controls on incision of the Mekong Valley.
PI: A. Replumaz
Climatic control on denudation in Namibia
Combining existing apatite fission track and new apatite (U-Th-Sm)/He data from the Brandberg Inselberg we documented two cooling phases since continental break-up in Namibia. We interpreted them respectively to be related to escarpment erosion following continental break-up and as a phase of enhanced denudation during the Early Eocene Climatic Optimum. We proposed that during this period weathering was important and contributed significantly to the denudation of the margin.
Main collaborators: J. Braun, C. Gautheron, J. Carcaillet, S. Schwartz
Erosion and isostasy in the Cordillera Blanca
The Cordillera Blanca (Peruvian Andes) morphology demonstrates important glacial erosion and thus a significant mass of rocks removal. We addressed the role of erosion and associated flexural rebound in the uplift and exhumation of the Cordillera Blanca with numerical modeling of landscape evolution. Our results evidenced the contribution of erosion and associated flexural rebound to the uplift of the Cordillera Blanca.
Stress field evolution above the Peruvian flat-slab
Flat-slab segments are supposed to increase coupling at the plate interface, resulting in an increase and eastward migration of the shortening in the overriding plate. However, above the Peruvian flat-slab, a 200 km-long active normal fault trend parallel to the Andean range. We performed a systematic inversion of striated fault planes in this region to better characterize the stress field above the Peruvian flat-slab and evidenced a succession of different tectonic regimes.
Cordillera Negra uplift
In northern Peru, regional exhumation in the Cordillera Occidental started at ~15 Ma, synchronous with the onset of subduction of the Nazca Ridge and eastward movement of regional magmatism. We proposed that the Nazca Ridge subduction at 15 Ma and onset of slab flattening drove regional surface uplift in the Cordillera Occidental.
Chuquibamba landslide
Several massive landslides disrupt the arid Western front of the Central Andes. New 10Be dating of the Chuquibamba landslide (southern Peru) provides evidence that the last major landslide event occurred at ~102 ka, during a wet climatic event (120 and 98 ka). Our study highlights the role of tectonics and climate on the localization of large Andean landslides in the Western Cordillera and on the long-term mass transfer to the trench along the arid Andean front.