Destabilization of Valles Marineris wallslopesby retreat of ancient glaciers

Daniel MEGEOlivier BOURGEOIS

Planetology and Geodynamics Laboratory

CNRS Research Unit #6112University of Nantes, France

Valles Marineris wallslopemorphogenesis

• Open air/fluvial?• Submarine/lacustrine?• Glacial/subglacial?

Peulvast and Masson, 1993

1

2

3

• Liquid flows?• Viscous flows?• Dry flows?

Doppelgraten (Penck, 1894; Paschinger, 1928)

I U S C H A S M AI U S C H A S M A

G E R Y O N M O N T E S

Ridge-top splitting

double crest lines

1. Observations at intra-chasma andinter-chasma ridges, and terrestrial analogs

Ius Chasmaridge width 20 km

Bodeneck, Austrian Alpsridge width 8 km

glacial valley

glacial valley

C A N D O R C H A S M A

M E L A S C H A S M A

1 km

antislope scarps

Hoher Trog

Oberes Törl

Austroalpine nappes, Austrian AlpsThanks to Jürgen Reitner (Geol. Survey Austria) for this photograph!

Hoher Trog

Thanks to Jürgen Reitner (Geol. Survey Austria)for this photograph!

antislope scarps

Austroalpine nappes, Austrian Alps

M E L A S C H A S M A

C A N D O RC H A S M A

Reitner and Linner, 2009

Jahn, Z. Geomorph., 1964

Historic study areas

Tatra MountainsTyrol

Western Tatras

Observation sites: Carpathians, Alps of Europe, Japan, and New Zealand; Cascades, U.S. and Canadian Rockies, Alaska, Andes, Scotland and England Caledonides, Himalaya

Tatra Mountains (Slovakia and Poland)Nemčok, 1972; Kellog, 1984

Oberes Törl, Austrian Alps

graben antislope scarps

Sackung (sagging)

Deep-seated GravitationalSlope Deformation (DGSD)

modern talented scientistjargon

old-fashioned wording

Deep-seated GravitationalSpreading (DSGS)

Zischinsky, 1966

base map: Peulvast et al., 2001

(more)

Valles Marineris ridge-top splitting and antislope scarp sites

(more)

inter-chasma ridge

chasma wall

intra-chasma ridge

IUS MELAS

Deep-seated gravitational slope deformation

• antislope scarps• basal bulging

Hippolyte et al., 2006, 2009

Belledonne RangeFrench Alps

post-glacialslope deformation

SAGGING SLOPE (Geryon Montes)

slope displacement

100 m

horizontaldipping 11°S

S A G G I N G S L O P E (Geryon Montes) no vertical exaggeration

F O L D E D F L O O R

vertical exaggeration x1.5

H O R I Z O N T A L F L O O R

(LPSC 2005)

Basal slope bulgingin Ius Chasma

Deep-seated gravitationalspreading in Ius Chasma

5 km

basal bulge

Mège et al., LPSC 2005

antislope scarps

G E R Y O NM O N T E S

MELAS CHASMA

More examples

CANDOR CHASMA

10 km

IUS CHASMA

MELAS CHASMA

CANDOR CHASMA

10 km

MELAS CHASMA

CANDOR CHASMA

OPHIR CHASMA

10 km

More examples

initial ridge top (split)

initial ridge top (split)

1

DSGS prior toILD deposition!

landslidelandslide2

ILDILD

3

COPRATES CHASMA

sturzstrom10 km

landslide

DGSD

initial ridge top

initial ridge top

steep landslide failure plane (56°) Lucas et al., LPSC 2009 + subm. JGR

Lucas et al., LPSC 2009 + subm. JGR

s t e e p e n i n g i n i t i a l f a u l t s c a r p d i p a n g l e

Steep initial failure dip angleaccounts for the shape of theCoprates sturzstrom deposits.

This is consistent with triggering fromdeep-seated gravitational slope deformation.

S1 S2 S3

COPRATES LANDSLIDE

Granular landslide modelling

Bovis and Jakob, 2000

July 29, 1998, debris flowMount Meager, British Columbia

antislope scarps

Sudden debris flow after decadesof slow deep-seated gravitationalslope deformation

Again a post-glacial event!

historical rock avalanches

1998 debris flow

500 m

Beinn Fhada(Long Mountain)

ScotlandCaledonides

• Post-glacial DSGS• Post-DSGS landsliding

antislope scarps

eroded landslide deposits?

micro-Candor Chasmalandslide analog?

vertical view

oblique view

400 m

Possible originfrom previous works

2. Is DSGSalways paraglacial?

Courtesy by J. ReitnerOberes Törl, Austrian Alps

spreading ridge cohesion loss

postglacial trigger(ridge debuttressing/glacial unloading): 29

32 DSGS trigger studies in international peer-reviewed publications

Kobayashi, K. Periglacial morphology of Japan. Biuletyn Periglacjalny 4, 15-36 (1956).Beck, A. C. Gravity faulting as a mechanism of topographic adjustment. New Zealand J. Geol. Geophys. 11, 191–199 (1968).Tabor, R. W. Origin of ridge-top depressions by large-scale creep in the Olumpic Mountains, Washington. Geol. Soc. Am. Bull. 82, 1811-1822 (1971).Radbrush-Hall, D. H., Varnes, D. J. & Savage, W. Z. Gravitational spreading of steep-sided ridges ("sackungen") in western United States. Int. Assoc. Eng. Geol. Bull. 14, 28-35 (1976).Bovis, M.J. Uphilll-facing (antislope) scarps in the Coast Mountains, southwest British Columbia. Geol. Soc. Am. Bull. 93, 804-812 (1982).Beget, J. E. Tephrochronology of antislope scarps on an alpine ridge near Glacier Peak, Washington, U.S.A. Arctic Alpine Res. 17, 143-152 (1985).Holmes, G. & Jarvis, J.J. Large-scale toppling with a sackung type deformation at Ben Attow, Scotland. Q. J. Eng. Geol. London 18, 287-289 (1985).Thorsen, G. W. Splitting and sagging mountains. Washington Geologic Newsletter 17, 3-1 (1992).Reitner, J., Lang, M. & van Husen, D. Deformation of high slopes in different rocks after würmian deglaciation in the Gailtal (Austria). Quaternary Int. 18, 43-51 (1993).Ego, F., Sébrier, M., Carey-Gailhardis, E. & Beate, B. Do the Billecocha normal faults (Ecuador) reveal extension due to lithospheric body forces in the northern Andes? Tectonophysics 265, 255-273 (1996).Bovis, M.J. & Jakob, M. The July 29, 1998, debris flow and landslide dam at Capricorn Creek, Mont Meager Volcanic Complex, southern Coast Mountains, British Columbia. Can. J. Earth Sci. 37, 1321-1334.Agliardi, F., Crosta, G., & Zanchi., A. Structural constraints on deep-seated slope deformation kinematics. Eng. Geol. 59, 83-102 (2001).Smith, L.N. Columbia Mountain landslide: late-glacial emplacement and indications of future failure, Northwestern Montana, U.S.A. Geomorphology 41, 309-322 (2001).Jarman, D. & Ballantyne, C. K. Beinn Fhada, Kintal: An example of large-scale paraglacial rock slope deformation. Scottish Geog. J. 118, 159-168 (2002).Hermann, S. W. & Becker, L. P. Gravitational spreading ridges on the crystalline basement of the Eastern Alps (Niedere Tauern mountain range, Austria). Mitt.Österr. Geol. Ges. 94, 123-138 (2003).Holm, K., Bovis, M. & Jakob, M. The landslide response of alpine basins to post-Little Ice Age glacial thinning and retreat in southwestern British Columbia. Geomorphology 57, 201-216 (2004).Brückl, E. & Paroditis, M. Prediction of slope instabilities due to deep-seated gravitational creep. Natural Hazards Earth System Sci. 5, 155-172 (2005).Hetzel, R. & Hampel, A. Slip rate variations on normal faults during glacial-interglacial changes in surface loads. Nature 435, 81-84 (2005).Kinakin, D. & Stead, D. Analysis of the distributions of stress in natural ridge forms: implications for the deformation mechanisms of rock slopes and the formation of sackung. Geomorphology 65, 85-100 (2005) doi:10.1016/j.geomorph.2004.08.002.Korup, O. Geomorphic imprint of landslides on alpine river systems, southwest New Zealand. Earth Surf. Process. Landforms 30, 783-800 (2005).Ambrosi, C., & Crosta, G. B. Large sackung along major tectonic features in the Central Italian Alps. Eng. Geol. 83, 183-200 (2006).Hippolyte, J.-C., Brocard, G., Tardy, M., Nicoud, G., Bourlès, D., Braucher, R., Ménard, G. & Souffaché, B. The recent fault scarps of the western Alps (France): tectonic surface ruptures or gravitational sackung scarps? A combined mapping, geomorphic, levelling, and 10Be dating approach. Tectonophysics 418, 255-276 (2006), doi:10.1016/j.tecto.2006.02.009.Hippolyte, J.-C., Tardy, M. & Nicould G. Les failles récentes des Grands-Moulins (Savoie) : un sackung (tassement gravitaire) majeur dans les Alpes françaises. C. R. Geosci. 338, 734-741 (2006).Hürlimann, M., Ledesma, A., Corominas, J. & Prat, P. C. The deep-seated slope deformation at Encampadana, Andorra: representation of morphologic features by numerical modelling. Eng. Geol. 83, 343-357 (2006).Jarman, D. Large rock slope failures in the Highlands of Scotland: Characterization, causes and spatial distribution. Engineering Geol. 83, 161-182 (2006).Turnbull, J.M. & Davies, T.R.H. A mass movement origin for cirques. Earth Surf. Process. Landforms 31, 1129-1148 (2006).Wilson, P., & Smith, A. Gomorphological characteristics and significance of Lat Quaternary paraglacial rock-slope failures on Skiddaw Group terrain, Lake District, northwest England. Geografiska Annaler 88, 237-252 (2006).Ustaszewski, M., Hampel, A. & Pfiffner, O. A. Composite faults in the Swiss Alps formed by the interplay of tectonics, gravitation and postglacial rebound: an integrated field and modelling study. Swiss. J. Geosci. (Eclogae Geologicae Helvetiae) 101, 223-235 (2008).Hippolyte, J.-C., Bourlès, D., Braucher, R., Carcaillet, J., Léanni, L., Arnold, M., & Aumaitre, G. Cosmogenic 10Be dating of a sackung and its faulted rock glaciers, in the Alps of Savoy (France). Geomorphology 108, 312-320 (2009).Reitner, J., & Linner, M. Formation and preservation of large scale toppling related to alpine tectonic structures – eastern Alps. Austrian J. Earth Sci. 102, 69-80 (2009).

• possible in theory• never documented

Rogers and Watkins, 2003

postglacial trigger(ridge debuttressing/glacial unloading): 29

32 DSGS trigger studies in international peer-reviewed publications

• possible in theory• never documented

Rogers and Watkins, 2003

2 reported (controversial) casesLoma Prieta, 1989 (Ponti and Wells, 1991)Northridge, 1994 (Harp and Gibson, 1996)

postglacial trigger(ridge debuttressing/glacial unloading): 29

32 DSGS trigger studies in international peer-reviewed publications

ridge edification by river incision and evaporite flowSomali plateau (Mège et al., submitted) Canyonlands grabens-type spreading

• possible in theory• never documented

Rogers and Watkins, 2003

2 reported (controversial) casesLoma Prieta, 1989 (Ponti and Wells, 1991)Northridge, 1994 (Harp and Gibson, 1996)

postglacial trigger(ridge debuttressing/glacial unloading): 29

+

32 DSGS trigger studies in international peer-reviewed publications

sandstonegypsum

Mège et al., submitted

summit graben

gypsum

sandstone

Gravitational spreading, Somali plateau

• possible in theory• never documented

Rogers and Watkins, 2003

2 reported (controversial) casesLoma Prieta, 1989 (Ponti and Wells, 1991)Northridge, 1994 (Harp and Gibson, 1996)

1 unelucidated case (seismic shaking dismissed)South Italy (Rizzo and Leggeri, 2004)

postglacial trigger(ridge debuttressing/glacial unloading): 29

+ridge edification by river incision and evaporite flowSomali plateau (Mège et al., submitted) Canyonlands grabens-type spreading

32 DSGS trigger studies in international peer-reviewed publications

--Deglaciation seems by farto be the most likely DSGStrigger in Valles Marineris

--

3. Are there other hints of ancient glaciersin Valles Marineris?

--Deglaciation seems by farto be the most likely DSGStrigger in Valles Marineris

--

Molnia, 2004

Tana glacier, Alaska

Ius Chasma

trimlines

formerly interpreted as normal fault scarps…Mège, 1994Peulvast et al., 2001

… but no clear length/displacement scaling law and poor segmentation!

trimline (highest extent of glacier)

600 m

G E RY O N

MO N

T E S

I U S

CH A S M A F L OO R

I U S landslidedeposits

Possibletrimlines

I U S C H A S M A

10 km

CandorChasmaSvalbard

Longyearbreen glacier

Evans, Quat. Sci. Rev., 2009

Thrilling Candor Chasma analog in Svalbard

5 km

Glacial receding since Little Ice Age

trimline

??

500 m

600 msubglacial polished rocks

trimline

chasma floor

Is a glacier still present in Candor Chasma?

ground moraine

-3000 m

-4000 m

-4500 m

TRIMLINE EXPOSED SUBGLACIAL ROCKS

-4200 m ILDs

ILDs

MASKED GLACIER?

2 km

+1200 m

Central Candor Chasma

northeastern Ius Chasma

1 km100 m

200 m

2 km

Receding glaciers

Valley glaciers in northern Nepal, Higher Himalaya

humocky topographydepending on local

melting conditions andrelative ice/rock ratio

ice melting

2 km

100 m

Ius Chasma

Glacial valleyin southern Tibet

GERYON MONTES (DSGS)MELAS CHASMA

From trimline height, preliminary measurements suggest that the thickness of some glaciers may have been ~ 0.5 - 2 km.

Conclusions

Wallrock has been very weak since deglaciation, providing a mechanical framework for widespread mass wasting processes during the Amazonian (Peulvast et al., 2001).

Morphology and structure of intra- and inter-chasma ridges in Valles Marineris point to the existence of ancient valley glaciers in all the major chasmata, hence equatorial glaciations (it can be shown that the glaciers producing DSGS were present before ILD deposition).