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!