POSTPONED — [ESS] Pascal Audet (U Ottawa)

This event has been postponed until the fall.

“Deep Roots of a Mountain Belt: Lithospheric Structure and Mantle Dynamics Beneath the Canadian Cordillera”

The Canadian Cordillera, a vast Phanerozoic mountain belt from the US border to Alaska, is classically attributed to terrane accretion, subduction, and strike-slip tectonics, but its deep architecture and the geodynamics of the northern Canadian Cordillera (NCC) have been unclear, fueling controversial models of its amalgamation and current tectonic deformation. New seismic data from the EarthScope USArray and other recent networks across Alaska and Yukon provide new constraints on its architecture and tectonic processes: the orogen is characterized by a shallow, flat Moho, with temperatures of ~800–900°C, which can support high topography without a conventional crustal root. Rigid lithospheric elements—the buried Mackenzie craton and the Liard Transfer Zone—act as buttresses that localize deformation and shape the arcuate deformation front. The Tintina Fault, a large-scale transcurrent fault, cuts through the full lithospheric mantle, displacing cratonic fragments. Furthermore, depressions of the 410 and 660 km discontinuities beneath a slab window created by subduction of the Resurrection/Farallon spreading ridge suggest mantle transition-zone temperatures are 100–300 K higher than in the surrounding mantle. Overall, a fossil divergent plate boundary provides a long-lived conduit for deep-mantle heat, linking whole-mantle convection to a hot, weak lithosphere and promoting long-term uplift of the Cordillera.

Earth Science Seminar —

Lecture portion of the EAPS graduate-level class 12.571, covering current research in geophysics, geology, geochemistry, and geobiology. All members of the MIT community are welcome to join for presentations by guest speakers, held approximately every two weeks during the term.

Contact: earth-science-seminar-info@mit.edu