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Philippe Vernant (http://www-gpsg.mit.edu/~vernant/)
(Bayasgalan et.al., 2005)
Interesting tectonics …
Extremely well-preserved geomorphology
On a thousand year scale …
850-950 year old earthquake ruptures (Walker et. al. 2006)
Jolivet et.al. 2007Ih Bogd
… and on a Million year scale!
Ritz et.al., 2006
Vassallo et.al. 2007
3650 m
2800 m
2000 m
1950 m
Fission track ages from Ih Bogd mountain, Gobi Altay, southern Mongolia
Vassallo et.al. 2007
•It is important in the India-Eurasia collison zone
•It is young
•It has very low rates of erosion …
It is a fantastic place to visit!
(Bayasgalan et.al., 2005)
2. What happens in the Hangay?
1. How does the Altay system evolve?
Age ~5 Ma (+/- 3 Ma)(e.g. Vassallo 2006)
Red lines = palaeoearthquakes
The Altay mountains
Age ~20-25 Ma(e.g. Yuan et.al. 2005)
(Nissen et.al. in review)
ASTER satellite image (15 m pixels)SPOT-5 image (2.5 m pixels)
(Nissen et.al. in review)
preferred ~130 m
How old?
minimum ~80 m
maximum ~240m(Nissen et.al. in review)
(Nissen et.al. in review)
Cosmogenic Isotope Exposure Dating
(with A.J. West and C. Schnabel)
0
20
40
60
80
100
120
140
160
180
200
0.00E+00 5.00E+05 1.00E+06 1.50E+06
Be-10 at/g
Dep
th c
m
?
10Be concentration
depth
Shape of curveErosion rate
Inherited 10Be
(Nissen et.al. in review)
(Nissen et.al. in review)
~130-150 m right-lateral displacement
Age of the alluvial fan …
Exposure dating
~70-80 ka
Slip-rate
~1.6-2.2 mm/yr
(Nissen et.al. in review)
130 m
95 m
125 m
130 m
125 m
(Nissen et.al. in review)
A
F1 surface is displaced by 15-20 m
F2 surface is displaced by ~130 m
Digital Elevation Model gridded from differential GPS measurements
(Nissen et.al. in review)
Luminescence age of S1 deposits 6.3 +/- 1.7 ka
Right-lateral displacement of S1 15-20 m
Estimate of average slip-rate 1.8-4.3 mm/yr
(Nissen et.al. in review)
Age of faulting …
15°
Slip-rate ~2 mm/yr
Shortening = 2sin15~0.5 mm/yr
map view
cross-section view
70°
Uplift = 0.5tan70~1.3 mm/yr
Topography ~ 2kmAge ~2 Ma
(Nissen et.al. in review)
Shortening ~0.5 mm/yr
Age ~5 Ma (+/- 3 Ma)(e.g. Vassallo 2006)~2 Ma (this study)
Age ~20-25 Ma(e.g. Yuan et.al. 2005)
(Nissen et.al. in review)
Conclusions:
The eastern Altayis younger than the west
(or has become more important!)
So what is now happening in the west?
Active faulting in central Mongolia
~4000 m, Otgon Tengger, central Mongolia
Tariat volcanic field
Petit et.al. 2008
Cunningham, 2001
Walker et.al. 2007
~2 km
Total geological displacements = ~20 km
Conclusion: This area IS an important part of the regional deformation!
But it is not measurable by GPS!
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