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, Time-calibrated Milankovitch cycles for the late Permian, Nature Communications

5. Earth-Moon System Evolution

6. Earth-Moon System Evolution
da/dt = f a-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 f = 6.85±0.08 x 1037 m6.5 s-1 = (0.344±0.004) f0
Don Dixon

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!