The role of a sharp cratonic keel edge for lithospheric delamination and rapid orogenic plateau uplift, Canadian Cordillera

David W S Eaton, University of Calgary, Department of Earth, Energy, and Environment, Calgary, AB, Canada, Xuewei Bao, University of Calgary, Geoscience, Calgary, AB, Canada and Bernard Guest, University of Calgary, Calgary, AB, Canada

Contact First Author: David W S Eaton; eatond@ucalgary.ca

Previously Published Material: A large fraction of this work was recently published in Nature Geoscience.

Abstract ID#: 34493

 

English Abstract:
The interior of the Canadian Cordillera is part of an exhumed fossil plateau located in a back-arc tectonic setting. Using data compiled from western Canada and USArray, we integrate new analysis of teleseismic Rayleigh-wave tomography with thermochronology data to investigate lithospheric structure and exhumation history in this region. The edge of the North American craton is marked by a remarkably abrupt change in lithospheric thickness, from > 200 km to < 50 km, coincident with a significant step in surface heat flow. This sharp plate edge delineates the eastern limit of a fossil orogenic plateau that experienced rapid uplift and exhumation (10 to 15 km) during the mid to late Eocene. Our tomographic images show evidence for a high-velocity block in the sub-Cordilleran mantle, at depths greater than 165 km, which we interpret as foundering lithospheric mantle; we propose that delamination of this block was triggered by edge-driven convection and led to rapid uplift, voluminous magmatism and transition from compressional to extensional regime. Similar processes may have resulted in removal of the lithospheric keel beneath the North China craton and regional uplift of the Altiplano.
Back to: Seismic Structure and Dynamics of the North American Cordillera I