Geological Constraints Lecture 6: Geodynamics Carolina Lithgow-Bertelloni.

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Presentation transcript:

Geological Constraints Lecture 6: Geodynamics Carolina Lithgow-Bertelloni

Constraints  Mass distribution and change  Geoid and free air gravity  TPW  Plate motions past and present  Magnetic anomalies  Topography  Flooding record  Stresses  Sources  Measure strain  Record of volcanism

Mass Distribution Density Contrast (Mg m -3 ) [Forte and Mitrovica, 2001]

Changes in Mass Distribution: True Polar Wander Density Contrast (Mg m -3 ) Inertial interchanges

Hotspots [Steinberger et al., 2004] Hotspot Tracks -Taking into account mantle wind -Letting hotspots move relative to each other -Taking into account plate deformation

Present-day plate motions [Forsyth and Uyeda,1975]

Magnetic Anomalies [Müller et al., 1994]

Plate Reconstructions:Cenozoic [10-25] [25-43] [43-48] [48-56] [56-64]

Plate Reconstructions: Mesozoic [Lithgow-Bertelloni and Richards, 1998] [64-74] [74-84] [84-94] [94-100] [ ]

Topography

Continental flooding Ocean-volume variations ice cap melting Changes in volume of ocean basins spreading rates Isostatic balance of crust Orogenesis (short uncompensated ) Epeirogeny long dynamic topography; tectonic uplift; post-glacial rebound

Sea-level Density Contrast (Mg m -3 )

Ages: 64 Ma [Xu and Lithgow-Bertelloni, 2004]

Bathymetry and sea-level [Conrad, Lithgow-Bertelloni and Xu, 2004] Following Pitman (1978) [Haq et al.] [Using G&J, 1986] [Using Hall (2000) for Philippine plate]

Contributions to Topography rr Mantle Flow Factors:  Isostatic balance of crust  Orogenesis  short uncompensated  Epeirogeny  Long  Tectonic uplift; post-glacial rebound; dynamic topography (Mitrovica et al., 1989; Gurnis, 1993)

Dynamic Topography 11 22 rr h   r /  g h Mantle Flow

Surface Topography Crustal Structure [ Laske et al., 2001] [Laske et al., 2002]

Residual Topography Continents-Crust 2.0; Oceans-Bathymetry from Isostasy No Depleted Mantle Continents-Crust 2.0; Oceans-Bathymetry from Age No Depleted Mantle Depleted Mantle [De Koker and Lithgow-Bertelloni, 2004]

Lithospheric Stress Field Contributions: Mantle Stresses; Crustal Heterogeneity [Reinecker, J., Heidbach, O. and Mueller, B., 2003] (available online at

g Inhomogeneity Topography Edge Tractions Basal Tractions Sources of Stress

Surface Topography Crustal Structure [ Laske et al., 2001] [Laske et al., 2002]

[Lithgow-Bertelloni & Guynn, 2004] Mantle Tractions

Modeling the stress field [Lithgow-Bertelloni and Guynn, 2004] Combined effect of crustal contribution and mantle flow LVC+TD0 Fit to observations (Variance Reduction) Azimuth-59% Regime-61%

Episodic Crustal Production? [Condie, 1998]

Plume Frequency 3 Different Experiments [Lithgow-Bertelloni et al., 2001]