Tectonic landforms. Global distribution Extension. Compression. Strike-slip faults Outlook: Implications for geophysics

Transcription

1 Tectonic landforms Global distribution Extension Long and narrow graben ( simple grabens ) Complex graben systems ( rifts ) Compression Wrinkle ridges Lobate scarps Strike-slip faults Outlook: Implications for geophysics Review papers: Tanaka et al. (1991) Banerdt et al. (1992)

2 Blattverschiebung (strike-slip fault, wrench fault) linkslateral

3 western hemisphere eastern hemisphere compression extension Global distribution from Banerdt et al. (1992)

4 Extensional features (graben) Cross-cutting relationships

5 N 10 km Simple graben

6 HRSC 3D-view l o n g a n d n a r r o w g r a b e n

7 from Anderson et al. (2001)

8 Southwestern part of Tharsis (Daedalia Planum, Terra Sirenum) from Wilson and Head (2002)

9 Radiating, long and narrow simple graben from Wilson and Head (2002)

10 Surface expression for giant radial dike swarms? Terrestrial analog: Mackenzie Dike Swarm (Canada) from Wilson and Head (2002) Alternative view: local volcanism and smaller dike swarms [Mège et al., J. Geophys. Res., 2002)

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12 Canyonlands National Park often considered to be a terrestrial analog for long and narrow Martian grabens but: deformation due to (relatively shallow) ductile salt layers Description: Multiple 'grabens' in Canyonlands. The Grabens are a system of linear collapsed valleys caused by the movement of underlying salt layers toward Copyright Martin Miller, University of Oregon

13 a) Faulting at bimaterial interface (e.g., mega-regolith over basalt) b) Faulted upper layer separated by sills from detachment zone from undeformed substrate c) Graben wedge falling into spaceaccomodating tensile crack d) Graben faults nucleated be dike dilatation at depth from Schultz et al. (2000), after Tanaka et al., J. Geophys. Res. 96 (1991)

14 Simple grabens on Mars thin-skin vs. thick-skin tectonics from: Schultz, LPSC XXXI (2000) Schultz: Modelle langer und schmaler Gräben Previous view: symmetric, strain concentrated above the décollement Current view: asymmetric, faults continue to depth as network

15 "Hourglass" model for planetary grabens from Schultz et al. (2000) after Watterson et al., J. Struct. Geol. 20 (1998)

16 Collapse pits northeast flank of volcano, Ascraeus Mons no raised rims, no ejecta 1000 m 13.0 N, W

17 p i t c r a t e r c h a i n ( c a t e n a ) ~3 km diameters up to > 4 km volumes up to > 7 km 3 Wyrick et al., J. Geophys. Res. 109 (2004) Tantalus Fossae Pit craters associated with faulting 38.2 N, W

18 Ferrill et al., GSA Today 14 (2004): dilatational normal faulting and collapse Crosscutting relationships pristine morphology Lack of sediment accumulation on the bottom active formation today?

19 HRSC 3D-view Intensely fractured terrain Claritas Fossae

20 HRSC 3D-view

21 HRSC 3D-view

22 HRSC 3D-view

23 Complex graben systems ( rifts ) Tempe Fossae: Are they comparable to a terrestrial continental rift? from Hauber & Kronberg (2001)

24 Tempe Fossae tectonic sketch map from Hauber & Kronberg (2001)

25 Topographic (MOLA-)Profiles across the Tempe Rift from Hauber & Kronberg (2001)

26 re-activation of older structures from Hauber & Kronberg (2001)

27 from Hauber & Kronberg (2001)

28 western hemisphere eastern hemisphere compression extension Global distribution from Banerdt et al. (1992)

29 common landforms on Mars, the Moon (mare surfaces), and Venus wrinkle ridge Viking Terrestrial analogs: Regularly spaced anticlinal ridges as surface expression of folding and thrust faulting (Yakima Fold Belt, Columbia River Basalts) MOC Image examples from: Montesi and Zuber, J. Geophys. Res. 108 (2003)

30 Wrinkle ridge topography Different spacing reflecting different lithospheric properties? from: Watters, Icarus 171 (2004

31 Wrinkle ridge topography from: Watters, Icarus 171 (2004 wrinkle wrinkle ridge ridge

32 Structural models proposed for planetary wrinkle ridges a) Buckle folds with nucleations of thrust faults [Watters, 1988] b) Simple thrust fault c) Conjugate thrust fault [Allemand & Thomas, 1992; Mangold et al., 1998] d) Fault-bend fold [Suppe, 1983; Suppe & Connors, 1992] e) Fault-propagation fold [Mercier et al., 1997] from Schultz, J. Geophys. Res. 105 (2000)

33 Wrinkle ridges Blind thrust model [Schultz, 2000] overall direction of thrusting

34 Wrinkle ridges Questions Depth of faulting: Thin- or thick-skinned tectonics? Geometry and number of faults? Importance of folding? Mechanical model of Watters (2004): thin-skinned deformation of upper crustal material, single thrust fault with listric geometry Outlook: MARSIS radar on Mars Express will investigate shallow crustal structure

35 Lateral movements (strike-slip faults) Typical for plate tectonics on Earth (e.g., San Andreas fault, North Anatolian fault) Evidence on Mars is very rare (Schultz, Nature, 1989)

36 Tectonic faults Ius Chasma 200 m

37 faults Layers in western Arabia Terra 8 N, 7 W 500 m

38 Outlook (1) Improved understanding of potentially seismic regions on Mars Mapping of faults Assessment of fault ages DLR

39 Outlook (2) Previous work demonstrates that the magnitude of displacement accommodated along faults with slip surfaces scales with their horizontal (map) lengths HRSC will improve the knowledge of lengthdisplacement relationships crustal properties from Schultz et al., LPSC XXXII (2001)