HR: 13:45h
AN: G23C-02 INVITED     [Abstracts]
TI: Dripping of a Mantle Lithosphere Root and Tectonics in the Sierra Nevada Region: Reconciling Geodynamic Modeling with Geodetic/Geological Constraints
AU: * Gogus, O H
EM: gogus@geology.utoronto.ca
AF: Department of Geology, University of Toronto, 22 Russell St., Toronto, ON M5S 3B1 Canada
AU: Pysklywec, R N
EM: russ@geology.utoronto.ca
AF: Department of Geology, University of Toronto, 22 Russell St., Toronto, ON M5S 3B1 Canada
AU: Davis, J L
EM: jdavis@cfa.harvard.edu
AF: Harvard-Smithsonian Center for Astrophysics, 60 Garden St., Cambridge, MA 02138 United States
AU: Cruden, A R
EM: cruden@utm.utoronto.ca
AF: Department of Chemical and Physical Sciences, University of Toronto at Mississauga, Mississauga, ON L5L 1C6 Canada
AB: Recent geophysical and geochemical studies in the Sierra Nevada region indicate that mantle lithosphere may be actively descending as a Rayleigh-Taylor-type instability. It has been postulated that this "drip" instability influenced the structural evolution of the crust and may be responsible for anomalous present-day topography in the area. Here, we consider in more detail this type of geodynamic mechanism in controlling the active and recent tectonics in the southern Sierra Nevada and surrounding region. Specifically, we conduct a series of scaled 2D numerical and 3D physical analogue experiments to examine quantitatively the evolution of the crust in response to underlying mantle instability. In the experiments, an idealized crust-mantle lithosphere-mantle system is configured in an upper mantle-scale solution space and a density perturbation is introduced into the model mantle lithosphere to initiate the gravitational instability. Observables from the experiments include surface topography, accumulated crustal deformation, and instantaneous strain rate. We compare the latter to crustal strain accumulation inferred from GPS measurements. In particular, an attempt is made to isolate the regional velocity field from the larger-scale North America-Pacific relative plate boundary motion, and to determine the contribution of steady (vs. episodic) strain accumulation in the measurements. In conjunction with the geodetic constraints, we reconcile the predicted deformation in the experiments with geological/geophysical observations of crust and mantle lithosphere structure, and compare the pattern of surface topography. The results provide integrated insights into the role of a local tectonic forcing in driving active and recent tectonic activity in the Sierra Nevada region.
DE: 1208 Crustal movements--intraplate (8110)
DE: 1213 Earth's interior--dynamics (8115, 8120)
DE: 1243 Space geodetic surveys
DE: 8107 Continental neotectonics
DE: 8120 Dynamics of lithosphere and mantle--general
SC: Geodesy [G]
MN: 2005 Joint Assembly