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| Titel |
On the Morphology and Transition of Valles Marineris Landforms: Rock Glaciers/Protalus Lobes vs. Landslides |
| VerfasserIn |
S. van Gasselt, E. Hauber, A. Dumke, B. Schreiner, G. Neukum |
| Konferenz |
EGU General Assembly 2009
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250027633
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| Zusammenfassung |
| The Valles Marineris canyon system exhibits a variety of different landforms associated with
landslide mechanisms, ranging from several tens of meters to kilometers in length. They
usually cover a surface of 1000 km2 and have an average volume of up to 5000
km3 [1–2]. It is assumed that they have been emplaced under wet as well as dry
conditions from destabilized wall-rock and from surrounding sapping valleys [e.g.,
1–3]. Absolute age determinations have furthermore shown that landslides in Valles
Marineris span much of Martian history with ages as young as 50 Myr up to 3.5 Gyr
[1]. Notwithstanding their individual ages and timespan during which they have
been emplaced, landslides seem to have formed repetitively producing comparable
morphologies and do not show substantial modifications throughout the last 3.5 Gy
[1].
We here put our focus on a set of complex tongue-shaped landforms situated in the central
parts of Valles Marineris at 283-E, 8-S which were previously identified as a single feature
and for which a possible rock–glacier origin had been proposed [5]. This assumption implies
environmental conditions which are not met today at such latitudes near the equator and
which would contradict all observations related to the distribution of periglacial landforms on
Mars, such as thermal contraction polygons, thermokarst features, and -– especially — lobate
debris aprons [e.g., 6–11] which are considered to be Martian analogues for terrestrial rock
glaciers.
On the basis of our observations we come to the conclusion that the landforms discussed
herein form a complex set of landslides derived from wall-rock sliding and/or from
surrounding valleys. Consequently, different sources areas are reflected by the complexity of
the landslides with several overlapping lobes and individual tongue-shaped features.
Although the tongue-shaped morphology is characteristic of rock-glacier landforms,
the assembly of furrows and ridges strongly suggests an origin caused by several
short-termed events rather than slow creep mechansims. Overlapping lobes and faint
compressional ridges as seen at this location are not caused by creep of mountain
debris but by multiple events that took place at least as early as 300 Myr ago (with
several resurfacing events) as crater counts suggest. Morphometric characteristics fit
quite well to the trends proposed by others for landforms indicative of landsliding
[12–13].
[1] C. Quantin et al. Icarus, 172:555–572, 2004. [2] C. Quantin et al. Planet. Space Sci., 52:1011–1022, 2004. [3] B.
K. Lucchitta. J. Geophys. Res., 84(B14):8097–8113, 1979. [4] A. Lucas and A. Mangeney. Geophys. Res. Lett.,
34:L10201, 2007. [5] W. Brian Whalley and Fethi Azizi. J. Geophys. Res., 108:E048032, 2003. [6] S. W. Squyres. Icarus,
34:600–613, June 1978. [7] S. W. Squyres. J. Geophys. Res., 84:8087–8096, December 1979. [8] N. Mangold et
al. Planet. Space Sci., 50:385–401, 2002. [9] N. Mangold. Journal of Geophysical Research (Planets), 108:8021,
2003. [10] F. C. Chuang and D. A. Crown. Icarus, 179:24–42, December 2005. [11] H. Li et al. Icarus, 176: 382–394,
2005.[12] A. S. McEwen. Geology, 17:1111–1114, 1989. [13] K. P. Harrison and R. E. Grimm. Icarus, 163:247–362,
2003. |
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