Continuing Colorado plateau uplift by delamination-style convective lithospheric downwelling

Area of Science:

• Geophysics
• Tectonics
• Geodynamics

Background:

• The Colorado Plateau, a high-elevation region in North America, lacks significant deformation, making its uplift mechanism unclear.
• Surrounding provinces experienced compressional and extensional deformation, unlike the internally stable plateau.
• Previous theories suggested isostatic equilibrium, but failed to explain the plateau's sustained high elevation.

Purpose of the Study:

• To investigate the deep lithospheric structure beneath the Colorado Plateau.
• To understand the geodynamic processes responsible for the plateau's uplift and high elevation.
• To link surface geological features, like Grand Canyon incision, to deep Earth processes.

Main Methods:

• Seismic tomography and receiver function analysis to image subsurface structures.
• Integration of petrologic and geochemical data.
• Analysis of Pliocene basaltic volcanism and Grand Canyon incision rates.

Main Results:

• Identification of a deep, high-velocity anomaly beneath the west-central Colorado Plateau extending over 200 km depth.
• Seismic imaging reveals a dipping interface from the lower crust to 70-90 km depth, with an elevated Moho.
• Interpretation of these features as evidence for ongoing delamination of the lower crust and lithosphere.

Conclusions:

• The Colorado Plateau's uplift and associated magmatism are driven by deep lithospheric foundering.
• Past subduction events hydrated and weakened the Proterozoic tectospheric mantle.
• Magmatic infiltration in the Cenozoic triggered downwelling and lithospheric removal, progressively uplifting the plateau over millions of years.