a planetary example of tectonic inversion: folding and thrusting in valles marineris, mars daniel...
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A Planetary Example of Tectonic Inversion:Folding and Thrusting in Valles Marineris, Mars
Daniel MEGEJean-Pierre PEULVASTPhilippe MASSON
Planetology and Geodynamics Lab, University of NantesGeography Institute, University of Paris-SorbonneIDES, University of Paris-Sud, Orsay
INSU
Blasius, Cutts, Guest, and Masursky, 1977Geology of the Valles Marineris: First Analysis of Imaging from the Viking 1 Orbiter Primary Mission, Journal of Geophysical Research
10 km
N
• Fractured anticline/syncline axes oblique to graben trend
Interpretation
Suggests transpressionMEGE, Ph.D. thesis, 1994PEULVAST et al., Geomorphology, 2001
10 km
strain partitioning
1
1
Hmin
Hmin
Themis image mosaic of Valles Marineris
Study area
Data used
•Themis imagery
• MOC imagery
• MOLA DEM
200 km
NASA/JPL/Arizona State University
IUS CHASMA
GERYON MONTES
1 Themis IR image2 Themis VIS images2 MOC images
Imagery
Viking image
N
GERYON MONTES
S
PLATEAU IUS CHASMA
1 km
South-dipping layer
horizontal layer
MOLA profile
N S
horizontal floor
truncatedlayerstruncatedlayers spursspurs
thrust planethrust plane
truncated layersspurs
top layer
thick central layerinner layer
Northern slope
N
NE
Fold layers
W
top layer
inner layer thrust fault
1 km
1 km
11°
11°
Southern slope
moat
floor deposits
N S
SW
NE
unloading ofwater-saturated
walls?
Origin of shortening
Sackung
ridge top splitting
gravitational unloading
landsliding
Reconstruction: from stretching to shortening
1 Rifting initiation
GERYON MONTES IUS CHASMA SOLIS PLANUM
SN
2 Rifting
SN
(1 - previous stage)
SN
3Spur and gully developmentOnset of detrital sedimentation (monocline layers?)
(2 - previous stage)
SN
SN
4 Wall sappingWater level loweringChannel development on graben floor
(3 - previous stage)
SN
SN
MO
C E
18
01
11
1upper foldlayer
oldest, exhumeddeposits (monoclinelayers, innermostfold layer?)
5 Late-stage stretching
(4 - previous stage)
SN
SN
6Dry erosional processes (mass wasting, aeolian activity)Sabkha deposits
(5 - previous stage)
SN
SN
7Geomorphological processes dominated by sackung
(6 - previous stage)
SN
SN
8Sackung and associated debris slopeStructural inversionAeolian reworking (sand dunes, deflation patterns)
SN
NASA/JPL/Arizona State University
20 km
Perspectives
Look for similar features in other places in Valles Marineris
Other sackung featuresin Coprates Chasma
ridge topsplitting
landslide
Perspectives
• Constrain rheology at depth from this and from composition of rock units as from OMEGA
• Model slope stability and failure through sackung
• Try to quantify stretching in order to estimate shortening
• Use shortening quantification and observed fold structure to determine thrust plane geometry and displacement
Intepretation of geologicunits
6
5
4
3
2
1
Dune fields (reworking of Fms 3-5)
Sabkhas (on Fms 3 and 4)
Dark, resistant floor material
Weak, thinly layered deposits
Exhumed resistant layers
Wallrock material