1. A Planetary Example of Tectonic Inversion: Folding and Thrusting in Valles Marineris, Mars Daniel MEGE Jean-Pierre PEULVAST Philippe MASSON Planetology and Geodynamics Lab, University of Nantes Geography Institute, University of Paris-Sorbonne IDES, University of Paris-Sud, Orsay INSU

2. Blasius, Cutts, Guest, and Masursky, 1977 Geology of the Valles Marineris: First Analysis of Imaging from the Viking 1 Orbiter Primary Mission, Journal of Geophysical Research 10 km N

3. Fractured anticline/syncline axes oblique to graben trend Interpretation Suggests transpression MEGE, Ph.D. thesis, 1994 PEULVAST et al., Geomorphology, 2001 10 km strain partitioning 11 11  Hmin

4. 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

5. 1 Themis IR image 2 Themis VIS images 2 MOC images Imagery Viking image

6. N GERYON MONTES S PLATEAUIUS CHASMA

7. 1 km South-dipping layer horizontal layer MOLA profile NS horizontal floor truncated layers truncated layers spurs thrust plane truncated layers spurs

8. top layer thick central layer inner layer Northern slope N NE

9. Fold layers W top layer inner layer thrust fault 1 km 11°

10. Southern slope moat floor deposits N S SW NE

11. unloading of water-saturated walls? Origin of shortening Sackung ridge top splitting gravitational unloading landsliding

12. Reconstruction: from stretching to shortening 1Rifting initiation GERYON MONTESIUS CHASMA SOLIS PLANUM SN

13. 2Rifting SN (1 - previous stage) SN

14. 3Spur and gully development Onset of detrital sedimentation (monocline layers?) (2 - previous stage) SN SN

15. 4Wall sapping Water level lowering Channel development on graben floor (3 - previous stage) SN SN MOC E1801111 upper fold layer oldest, exhumed deposits (monocline layers, innermost fold layer?)

16. 5Late-stage stretching (4 - previous stage) SN SN

17. 6Dry erosional processes (mass wasting, aeolian activity) Sabkha deposits (5 - previous stage) SN SN

18. 7Geomorphological processes dominated by sackung (6 - previous stage) SN SN

19. 8Sackung and associated debris slope Structural inversion Aeolian reworking (sand dunes, deflation patterns) SN

20. NASA/JPL/Arizona State University 20 km Perspectives Look for similar features in other places in Valles Marineris Other sackung features in Coprates Chasma ridge top splitting landslide

21. 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

23. Intepretation of geologic units 654321654321 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