River-deposit dimensions versus stratigraphic elevation in Aeolis Dorsa: resolving the great drying ...
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River-deposit dimensions versus stratigraphic elevation in Aeolis Dorsa: resolving the great drying of Mars. Rationale: River-deposit dimensions constrain hydrology and climate on Early Mars, but stratigraphy is essential to build a time series of constraints on climate change

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Edwin Kite , Antoine Lucas, John C. Armstrong, Oded Aharonson & Michael P. Lamb

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Edwin kite antoine lucas john c armstrong oded aharonson michael p lamb

River-deposit dimensions versus stratigraphic elevation in Aeolis Dorsa: resolving the great drying of Mars

  • Rationale: River-deposit dimensions constrain hydrology and climate on Early Mars, but stratigraphy is essential to build a time series of constraints on climate change

  • Today, use measurements of Early Mars river-deposit dimensions versus stratigraphic elevation to:

  • Characterize river-forming episodes

  • Constrain river discharge versus time.

width

wavelength

Edwin Kite, Antoine Lucas,

John C. Armstrong, Oded Aharonson & Michael P. Lamb


River deposits record constraints sorely needed for early mars climate models

  • Environmental scenarios for precipitation-fed runoff on Early Mars vary widely:

    e.g. Haberle et al. 2012, Kite et al. Icarus 2013, Mischna et al. 2013, Segura et al. 2012, Urata & Toon 2013, Wordsworth et al. 2013

    Andrews-Hanna & Lewis 2011 …

  • Early Mars rivers constrain magnitude, duration, intermittency, and number of wet

    events:

    e.g. Burr et al. 2010, Palucis et al. 2014, Irwin et al. 2005, Hoke et al. 2011, Williams et al. 2011, Morgan et al. 2014, Grant & Wilson 2012

    Need error bars on geologic constraints to avert climate model overfitting

River deposits record constraintssorely needed for Early Mars climate models

Uzboi-Ladon

Isidis rim

space-time

correlation?

large valleys

?

alluvial fans

Gale crater

how many episodes of climate-driven river formation?

E. Meridiani

Omitted: later-stage and non-climate driven: e.g. Fassett et al. 2010, Hobley et al. 2014, Hauber et al. 2013, Kleinhans et al. 2010,

Kraal et al.2008, Mangold et al. 2012, Harrison et al. 2011, Jones et al. 2011.


Edwin kite antoine lucas john c armstrong oded aharonson michael p lamb

Advantages of Aeolis Dorsa

(a 105 km2 sedimentary-rock basin, ~10°E of Gale)

e.g. Burr et al. 2009, Zimbelman & Scheidt 2012,

Kite et al. 2013, Kite et al. Nat. Geosci. in press

~ 30m range

In elevation

PSP_007474_1745 / ESP_024497_1745 (DTM)

500 m


Basin scale mapping distinguishes 10 2 m thick river deposit hosting units

Kite et al., Nature

Geoscience, in press

Basin-scale mapping distinguishes 102 m-thick river-deposit-hosting units

= HiRISE DTMs

by Antoine Lucas

60 km

900 km E of Gale

yardangs,

meander

belts,

retains

few

craters

smoothly

eroding,

fine-scale

channels,

retains

many

craters

overlies

F2

F1

400m

B20_017548_1739_XI_06S206W

Howard PNAS 2009


Data reduction

102 wavelengths

(52 channels)

189 widths

(137 channels)

Data reduction

inspired by Howard & Hemberger, Geomorphology 1991

Similar approach for channel widths.

color:

modern

topographic

range (4m)


Dramatically different erosional expression modest change in river deposit dimensions

Dramatically different erosional expression, modest change in river-deposit dimensions

38% change in median channel wavelength

38% change in median channel width

Channel width (m)

Channel wavelength (m)

no evidence for changing with stratigraphic elevation (n=42)

modal is= 10-15


Edwin kite antoine lucas john c armstrong oded aharonson michael p lamb

Fluvial signatures of climate events on Earth

Example: During planet-scale hyperthermal: rapid increase in sediment flux and discharge

increased precipitation

thick, wide, multistorey channel deposits

Before planet-scale hyperthermal: thin, narrow single-story channel deposits

Foreman et al., Nature 2012

See also: Ward et al., Science 2000

Amundson et al., GSA-B 2012


A tool to search for abrupt climate change on mars

A tool to search for abrupt climate change on Mars

zstrat

F2

F1

repeat

103 x

CDF of breakpoints

from 103 trials:

zstrat

no evidence for

abrupt change

bootstrap

find breakpoints

using nonparametric

method

abrupt

change

nominal

breakpoint

also perturb bootstrapped

points

0

# breakpoints

breakpoint in

bootstrapped

data

Results presented today are similar using planar, quadratic, IDW, and universal kriging methods for structure contour interpolation.


1 meander wavelengths

strat.

error

strat.

error

1. Meander wavelengths

(4-20) Myr from embedded-crater frequency (Kite et al., ‘Pacing Early Mars fluvial…,’ Icarus 2013)

  • Meander wavelengths tighten upwards

  • Small meanders rare/absent below contact, common above contact


2 river widths

strat.

error

2. River widths

(4-20) Myr from embedded-crater frequency

(Kite et al., ‘Pacing Early Mars fluvial…,’ Icarus 2013)

  • Channel widths narrow upwards

  • Narrow channels rare/absent below contact, common above contact


Limitations and caveats

Limitations and caveats

  • Catchment areais unknown

  • Wider channel deposits at higher stratigraphic levels (F3)

  • Taphonomy of channels?

    • e.g. Williams et al. Icarus 2013

  • Role of aeolian deposition?

    • e.g. Milliken et al. GRL 2014, Kocurek & Ewing SEPM Sp. Pub. 2012, Kite et al. Geology 2013, Bridges & Muhs SEPM Sp. Pub. 2012

“rhythmite”

alluvial

fans

This talk

meander belts

river deposits

not observed


Variability in river discharge versus time isn t enough to exclude orbital forcing

Variability in river discharge versus time isn’t enough to exclude orbital forcing

Kite et al., ‘Seasonal melting…,’ Icarus 2013

Total interval (4-20) Myr from embedded-crater frequency (Kite et al., ‘Pacing fluvial…,’ Icarus 2013)

Phase of orbital cycle

Eaton, Treatise on Geomophology, 2013

Burr et al., JGR-E, 2010

snowpack temperature

Threshold

Results using other interpolation methods & other break-points

are similar

- Consistent with orbital forcing

Evidence for 3 m amplitude

cut-and-fill cycles during F2

(wet-dry cycle in Burns Fm? Metz et al. 2009)

- Also consistent with multiple transient events!


Conclusions

Conclusions

  • F2 records a distinct river-forming episode - after the big meander belts and before the alluvial fans.

  • ~40% reduction in river-deposit dimensions at or near the F1/F2 contact in Aeolis Dorsa

  • Consistent with ~2 x reduction in peak discharge across the contact.

    • 200m stratigraphy, (4-20) Myr total depositional interval

    • Goal: relate to quantitative models linking sed. & strat. to climate

      e.g. Kite et al., ‘Seasonal melting,’ Icarus 2013, Kite et al., ‘Growth and form …’, Geology 2013

  • More information: www.astro.princeton.edu/~kite

    With thanks to: Devon Burr, Alan Howard, Rebecca Williams, Robert Jacobsen, Lynn Carter, Bill Dietrich, Laura Kerber, Frederik Simons, Ross Irwin, Bill Dietrich, Alexandra Lefort, & Noah Finnegan for discussions, ideas, and inspiration.


    Edwin kite antoine lucas john c armstrong oded aharonson michael p lamb

    End of presentation


    Edwin kite antoine lucas john c armstrong oded aharonson michael p lamb

    Relevance to Gale Crater

    Correlated in models

    of liquid-water availabillity:

    This Talk

    Tharsis

    latitude

    MSL rover

    F2

    Hellas

    longitude

    Early Mars water-availability model output (Kite et al., ‘Seasonal melting …’ Icarus 2013a)

    Correlated in lithology(?):

    Zimbelman & Scheidt, Science 2012


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