Crust and Mantle Structure Beneath the Colorado Plateau (Invited)
Abstract
The La Ristra experiment consisted of a northwest trending linear deployment of 72 broadband seismic stations from West Texas to western Utah with 15 to 20 km spacing. The resulting 1400 km seismic line provides unprecedented images of crust and mantle along a cross section that crosses the Colorado Plateau from near Mount Taylor in the east to the Marysvale volcanic field in the west. Surface wave analysis shows the Colorado Plateau to have a 120-150 km thick high seismic velocity lid that we identify with cold lithosphere. A sharp negative gradient below 120-150 km depth indicates a sharp boundary to the lithosphere at depth with hot asthenosphere in contact with the base of the lithosphere. Receiver function analysis shows central Plateau crust to be 42-50 km thick thinning to 30-35 km thick at the edges. Isostatic calculations show that only a fraction of the Plateau elevation can be explained by thickened crust thus the high topography of the Plateau has a largely mantle source. Bodywave tomography is consistent with the surface wave analysis but shows that at both edges of the Plateau there are narrow (50-100km) high velocity zones extending to at least 200 km depth. We interpret these seismic anomalies as mantle downwellings that are part of small edge convection cells initiated by lateral temperature gradients created by extension in the Great Basin and Rio Grande Rift. Numerical modeling indicates the convection is significantly eroding the lithosphere at the edges of the Plateau accounting for the high elevations observed there. Associated upwellings are responsible for the late Neogene-Quaternary magmatism surrounding the Plateau.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2010
- Bibcode:
- 2010AGUFM.T14C..03G
- Keywords:
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- 8120 TECTONOPHYSICS / Dynamics of lithosphere and mantle: general