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Geological Constraints

This lecture by Carolina Lithgow-Bertelloni delves into the complexities of geodynamics, focusing on mass distribution and its impact on the geoid, free air gravity, and plate motions throughout history. It discusses the influences of magnetic anomalies, topography, and flooding records while considering sources of stress and strain in the Earth's crust. The presentation includes findings from key studies on density contrasts, mantle flow, and the effects of hotspots and plate deformation. Key concepts include isostatic balance, tectonic uplift, and the implications of geological processes on sea level variations.

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Geological Constraints

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  1. Geological Constraints Lecture 6: Geodynamics Carolina Lithgow-Bertelloni

  2. 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

  3. Mass Distribution [Forte and Mitrovica, 2001] -0.18 -0.08 +0.02 +0.12 +0.22 Density Contrast (Mg m-3)

  4. Changes in Mass Distribution:True Polar Wander Inertial interchanges -0.18 -0.08 +0.02 +0.12 +0.22 Density Contrast (Mg m-3)

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

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

  7. Magnetic Anomalies [Müller et al., 1994]

  8. [10-25] [48-56] Plate Reconstructions:Cenozoic [56-64] [25-43] [43-48]

  9. [64-74] [94-100] Plate Reconstructions: Mesozoic [74-84] [100-119] [84-94] [Lithgow-Bertelloni and Richards, 1998]

  10. Topography

  11. 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

  12. Sea-level -0.18 -0.08 +0.02 +0.12 +0.22 Density Contrast (Mg m-3)

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

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

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

  16. h=- r/g h 1 r 2 Mantle Flow Dynamic Topography

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

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

  19. Lithospheric Stress Field Contributions: Mantle Stresses; Crustal Heterogeneity [Reinecker, J., Heidbach, O. and Mueller, B., 2003] (available online at www.world-stress-map.org)

  20. Sources of Stress g Inhomogeneity Topography Edge Tractions Basal Tractions

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

  22. Mantle Tractions [Lithgow-Bertelloni & Guynn, 2004]

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

  24. Episodic Crustal Production? [Condie, 1998]

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

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