HR: 17:45h
AN: DI14A-08 [Abstracts]
TI: Mantle Convection and the Recent Geological Evolution of the Southwestern United States
AU: * Moucha, R
EM: moucha@sca.uqam.ca
AF: GEOTOP - Université du Québec à Montréal, CP 8888, succursale Centre-Ville,
Montréal, QC H3C 3P8, Canada
AU: Forte, A M
EM: forte.alessandro@uqam.ca
AF: GEOTOP - Université du Québec à Montréal, CP 8888, succursale Centre-Ville,
Montréal, QC H3C 3P8, Canada
AU: Rowley, D B
EM: rowley@geosci.uchicago.edu
AF: The Department of the Geophysical Sciences, University of Chicago, 5734 S. Ellis Avenue,
Chicago, IL 60637, United States
AU: Mitrovica, J X
EM: jxm@physics.utoronto.ca
AF: The Department of Physics, University of Toronto, 60 St. George St., Toronto, ON M5S 1A7, Canada
AU: Grand, S P
EM: steveg@geo.utexas.edu
AF: Jackson School of Geological Sciences, University of Texas at Austin, PO Box B, University
Station, Austin, TX 78712, United States
AU: Simmons, N A
EM: nathan.simmons.utexas@gmail.com
AF: Jackson School of Geological Sciences, University of Texas at Austin, PO Box B, University
Station, Austin, TX 78712, United States
AB:
The present-day dynamic topography in the Southwestern US and its corresponding rate of
change are predicted with a high-resolution mantle convection simulation based on a new
global seismic tomography model (Simmons et al. 2007) which incorporates mineral, physical and surface
geodynamical constraints. The 2° horizontal resolution in the
global tomography model enables us to perform flow calculations with much greater spatial
resolution than previously possible. These convection simulations also incorporate a
viscosity profile derived from joint inversions (Mitrovica and Forte, 2004) of
convection-related surface observables (surface gravity anomalies, topography, divergence
of tectonic plate motions, excess ellipticity of the core-mantle boundary) and data
associated with the response of the Earth to ice-age surface mass loading (decay times
inferred from post-glacial sea-level histories in Hudson Bay and Fennoscandia, and the
Fennoscandian relaxation spectrum). A fundamentally important aspect of the mantle
convection model is the use of a 3-D mantle density distribution that explicitly accounts
for both thermal and compositional heterogeneity. The predicted near-surface convective
flow velocities and associated surface topography thereby include the stabilizing effect
of compositional buoyancy in the continental tectosphere and deep lower mantle. We will
present the implications of this new convection model for the time-dependent topography
of the Colorado Plateau where we find a focused dynamic topography high in the Western
US which overlies a regional mantle upwelling in the asthenosphere. Additionally, we will
consider the implications of our convection model on the late Cenozoic evolution of the
Colorado Plateau, the second stage of rifting in the Rio Grande valley and the associated
magmatic activity along the Jemez lineament.
DE: 8121 Dynamics: convection currents, and mantle plumes
DE: 8175 Tectonics and landscape evolution
DE: 8178 Tectonics and magmatism
DE: 8180 Tomography (6982, 7270)
SC: Study of the Earth's Deep Interior [DI]
MN: 2007 Fall Meeting