HR: 1340h
AN: T13A-0437    [Abstracts]
TI: Impact of Deep Mantle Dynamics on the North American Continent
AU: * Forte, A M
EM: forte.alessandro@uqam.ca
AF: GEOTOP - Département des Sciences de la Terre et de l'Atmosphère, Université du Québec à Montréal, CP 8888, succursale Centre-ville, Montréal, QC H3C 3P8 Canada
AU: Simmons, N
EM: nathan@geo.utexas.edu
AF: Jackson School of Geosciences, University of Texas at Austin, 1 University Station, C1140, Austin, TX 78712 United States
AU: Grand, S P
EM: steveg@geo.utexas.edu
AF: Jackson School of Geosciences, University of Texas at Austin, 1 University Station, C1140, Austin, TX 78712 United States
AU: Mitrovica, J X
EM: jxm@physics.utoronto.ca
AF: Department of Physics, University of Toronto, 60 St George Street, Toronto, ON M5S 1A7 Canada
AB: Recent advances in mapping 3-D mantle structure by simultaneously inverting global seismic data and convection-related surface observables (Simmons et al., 2005) yield high resolution models of the mantle convective flow which successfully reconcile both the seismic and geodynamic data sets. We have developed a mantle flow model, based on the most recent joint seismic-geodynamic inference of 3-D mantle structure, which incorporates a depth-dependent viscosity profile derived from the simultaneous inversion of glacial isostatic adjustment (GIA) and convection data (Mitrovica & Forte, 2004). In addition, this mantle flow model explicitly resolves the distinct chemical buoyancy which characterizes the continental roots. Geophysical observations of surface gravity and topography over the North American landmass have been corrected for the effects of present-day post-glacial rebound and crustal heterogeneity, thereby revealing large-amplitude regional variations which are successfully explained by the tomography-based mantle flow model. We find that a large fraction of the corrected surface gravity and topography variations over North America originate from density anomalies below 400 km depth. Similarly, the mean amplitude of maximum horizontal stress, SHmax, exerted at base of the crust by the convective flow (~ 9 MPa) also has a large deep-mantle contribution (depth > 400 km) which explains 60% of SHmax. Finally, we also find that the horizontal traction field acting on the base of the crust shows a striking convergence (compression) in the central portion of the continental US which may be attributed to the dynamics of the subducting Farallon plate in the deep mantle.
DE: 8110 Continental tectonics: general (0905)
DE: 8121 Dynamics: convection currents, and mantle plumes
DE: 8122 Dynamics: gravity and tectonics
DE: 8180 Tomography (6982, 7270)
SC: Tectonophysics [T]
MN: Fall Meeting 2005