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Milankovitch Cycle Evolution and Uncertainty

Milankovitch Cycle Evolution and Uncertainty. Dave Waltham. Outline. C roll-Milankovitch cycles Application to c yclostratigraphy Earth-Moon system evolution The time-varying drag problem Time-evolution of CM cycles and their (big) uncertainties Beware!. Croll-Milankovitch Cycles.

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Milankovitch Cycle Evolution and Uncertainty

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  1. Milankovitch Cycle Evolution and Uncertainty Dave Waltham

  2. Outline • Croll-Milankovitch cycles • Application to cyclostratigraphy • Earth-Moon system evolution • The time-varying drag problem • Time-evolution of CM cycles and their (big) uncertainties • Beware!

  3. Croll-Milankovitch Cycles

  4. Cyclostratigraphy Wu et al, 2013. Time-calibrated Milankovitch cycles for the late Permian, Nature Communications

  5. Earth-Moon System Evolution

  6. Earth-Moon System Evolution da/dt = fa-5.5

  7. Earth-Moon System Evolution

  8. Earth-Moon System Evolution

  9. Time Varying Drag f= 2.01±0.03 x 1038 m6.5 s-1

  10. Time-Varying Drag Don Dixon f= 6.85±0.08 x 1037 m6.5 s-1 = (0.344±0.004) f0

  11. Time-Varying Drag OR

  12. Time-Varying Drag • Stochastic Variation • Log-normal variation • f = exp( m + s 2/2 ) • Secular Increase • Resonance in oceans is predicted to peak when day length ~ 27 hours (Webb, 1982)

  13. Time-Varying Drag • Stochastic variation • Monte-Carlo Simulation • Secular increase • Exponential approximation

  14. Time-Varying Drag • Geological Constraints • Tidal Rhythmites • Only really good ones are from Elatina/Reynella(Williams, 1989, 2000; Deubner, 1990) • 620±20 Ma • f = (0.51±0.02) f0

  15. Time-Varying Drag

  16. Time-Varying Obliquity

  17. Time-Varying Obliquity

  18. Web-based Tool

  19. Beware!

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