River-deposit dimensions versus stratigraphic elevation in Aeolis Dorsa: resolving the great drying of Mars
Edwin Kite, Antoine Lucas, John C. Armstrong, Oded Aharonson & Michael P. Lamb
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:1)Characterize river-forming episodes2)Constrain river discharge versus time.
wavelength
width
River deposits record constraintssorely 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
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.
Uzboi-Ladon
Isidis rim
Gale crater large valleys alluvial fansspace-timecorrelation?
E. Meridiani…
how many episodes of climate-driven river formation?
?
500 m
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
~ 30
m ra
nge
In e
leva
tion
PSP_
0074
74_1
745
/ ESP
_024
497_
1745
(DTM
)
Basin-scale mapping distinguishes 102 m-thick river-deposit-hosting units
F1
Kite et al., Nature Geoscience, in press
= HiRISE DTMs by Antoine Lucas
smoothly eroding,fine-scale channels,retains many craters
overlies
900 km E of Gale
yardangs, meander belts,retains fewcraters
Howard PNAS 2009
60 km
F2
B20_017548_1739_XI_06S206W
400m
Data reduction
inspired by Howard & Hemberger, Geomorphology 1991Similar approach for channel widths.
color:moderntopographicrange (4m)
102 wavelengths (52 channels)
189 widths(137 channels)
Dramatically different erosional expression, modest change in river-deposit dimensions
38% change in median channel wavelength 38% change in median channel width
no evidence for changing with stratigraphic elevation (n=42) modal is = 10-15
Channel wavelength (m) Channel width (m)
Foreman et al., Nature 2012See also: Ward et al., Science 2000
Amundson et al., GSA-B 2012
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
Fluvial signatures of climate events on Earth
find breakpoints
using nonparametricmethod
A tool to search for abrupt climate change on Mars
bootstrap
F1F2
repeat103 x
CDF of breakpointsfrom 103 trials:
also perturb bootstrapped
points
zstrat
no evidence for
abrupt change
abrupt change
zstrat
# breakpoints
0
nominal breakpoint
breakpoint in bootstrapped
data
Results presented today are similar using planar, quadratic, IDW, and universal kriging methods for structure contour interpolation.
1) Meander wavelengths tighten upwards2) Small meanders rare/absent below contact, common above contact
(4-2
0) M
yr fr
om e
mbe
dded
-cra
ter f
requ
ency
(K
ite e
t al.,
‘Pac
ing
Early
Mar
s flu
vial
…,’
Icar
us 2
013)
strat.errorstrat.error
1. Meander wavelengths
2. River widths
1) Channel widths narrow upwards2) Narrow channels rare/absent below contact, common above contact
(4-2
0) M
yr fr
om e
mbe
dded
-cra
ter f
requ
ency
(Kite
et a
l., ‘P
acin
g Ea
rly M
ars
fluv
ial…
,’ Ic
arus
201
3)
strat.error
• Catchment area is 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
Limitations and caveats
This talk
alluvial fans
meander belts
“rhythmite”
river depositsnot observed
snowpack temperature
- 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!
Phas
e of
orb
ital c
ycle
Kite et al., ‘Seasonal melting…,’ Icarus 2013
Variability in river discharge versus time isn’t enough to exclude orbital forcing
Threshold
Mean Nominalbankfull Q from mean
Mean Nominal bankfull Q from mean
interpolated elevation, geologic break-point:
F2 (275±26) m 42 m3 s-1 (21±2) m 20 m3 s-1
F1 (402±18) m 76 m3 s-1 (31±3) m 43 m3 s-1
Change 1.5 x 1.8 x 1.5 x 2.1 x
interpolated elevation, break-point from hydrology:
above (274±16)m TBD m3 s-1 18 m TBD m3 s-1
below (410±19)m TBD m3 s-1 30 m TBD m3 s-1
change 50% 67%
unit assigned from map (no interpolation)
F2 (320±26)m TBD m3 s-1 (23±1) m TBD m3 s-1
F1 (420±18)m TBD m3 s-1 (35±2) m TBD m3 s-1
change 1.31x 1.7x 1.67
Total interval (4-20) Myr from embedded-crater frequency (Kite et al., ‘Pacing fluvial…,’ Icarus 2013)
Results using other interpolation methods & other break-pointsare similar
Eaton, Treatise on Geomophology, 2013Burr et al., JGR-E, 2010
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
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.
More information: www.astro.princeton.edu/~kite
End of presentation
F2
MSL rover
This Talk
longitude
latit
ude
Thar
sis
Hellas
Early Mars water-availability model output (Kite et al., ‘Seasonal melting …’ Icarus 2013a)
Relevance to Gale Crater
Zimbelman & Scheidt, Science 2012
Correlated in modelsof liquid-water availabillity:
Correlated in lithology(?):