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Alluvial Fan Science Potential

Alluvial Fan Science Potential. Kelin X. Whipple and Kelli Wakefield School of Earth and Space Exploration Arizona State University. Holden Crater. Bajada: Apron of Coalescing Alluvial Fans. from Moore and Howard (2005). Common Elevation Alluvial Fan Margins (~2000m): Top LTLD.

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Alluvial Fan Science Potential

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  1. Alluvial Fan Science Potential Kelin X. Whipple and Kelli Wakefield School of Earth and Space Exploration Arizona State University

  2. Holden Crater Bajada: Apron of Coalescing Alluvial Fans from Moore and Howard (2005)

  3. Common Elevation Alluvial Fan Margins (~2000m):Top LTLD

  4. Bajada Traverse: Scientific BonusDiversity, Context, Clay Source?, Depositional Environment through Time, Duration Wet Conditions

  5. Science Value: Bajada Traverse • Source-Area (Crater Wall) Materials • Lithology, Mineralogy (clast/matrix), Weathering • Context for LTLD • Depositional Environment (relation to LTLD) • Paleoclimatic Conditions (hydraulics, weathering) • Plausible Water Source(s) • Duration of Active Sediment Transport • Depositional Process • Mudflow / Debris Flow – composition (water content) • Other Mass Flow? • Fluvial (gravel – boulder) – flow depth, grain size • Fluvial (sand – granule) • Intermittency?

  6. Relation to LTLDLayers exposed in every fresh crater Layers exposed in every channel ridgeContact/transition exposed in cliffs (see Full Res HiRise)?

  7. Fans Common in CratersLate Noachian, Widespread within Latitudinal BandExcellent Context: Understand LTLD in General

  8. Fluvial Fans Best Analog But Mixed Stream and Mudflow Fans Can be Less Steep

  9. Constraining Environmental Conditions (Fluvial Fans) Flow and Sediment Transport Relations

  10. Expanding Flow Sandy channels Gravel channels

  11. Expanding Flow Model (bedload) Parker et al. (1998) Reduce: n = 3/2 (bedload); Terrestrial Fans (Stock et al., 2008), Experimental Fans No Dependence on g, D, or Flow Width!

  12. Equilibrium Channel Model (bedload) Reduce: n = 3/2 (bedload); Critical Stress Dominant

  13. Equilibrium Channel Model (suspended load, n = 5/2)

  14. Required Water Volume (Fluvial) 15-250(50)Vf Required Water Volume (Mudflow) ~40x Less!

  15. Water Volume -> Formation Time Weakest link ~10’s – 1000 years minimum (200 – 20000) [5% intermittency]

  16. Relation to LTLDLayers exposed in every fresh crater Layers exposed in every channel ridgeContact/transition exposed in cliffs (see Full Res HiRise)?

  17. Calculation of Qw • Empirical method by Irwin et al. (2005) • Q 2= 1.9w1.22 • Correction for Mars: multiply by factor of 0.76 (1.25-1.22) to account for lower velocity on Mars for same discharge

  18. Bedload-Dominated Sand Suspension-Dominated Sand Straight to Concave Profiles Convexo-Concave Profiles Lines are Theoretical Prediction (no tuning of parameters)

  19. Bedload-Dominated Sand Experiments Vary Qw Lines are Theoretical Prediction (no tuning of parameters)

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