geological features, such as compositional layering, rock central Mongolia, and northeast in eastern Mongolia. The Late 4.
boundaries and fault zone form edges of spatial-frequency Paleozoic belt (Hercynian orogeny) lies roughly to the south of the
distribution of brightness, either through contrasts in optical Early Paleozoic belt. Each of these belts is probably associated
properties or because they form topographic features with with subduction of oceanic lithosphere and the collision of Wes
associated shadows. Their associated contrast gradients and the fragments to the ancient southern margin of the Siberian continent. ther
spatial resolution of the system therefore control how much this
information about geological structures can be extracted from The basement of westem Mongolia seems to have been earti
these data. The catalogue of earthquakes of Mongolia till 1989 consolidated by the end of the Paleozoic. Continental volcanism evid
were also consulted. and weak deformation revealed by open folding were widely crite
spread in the Mesozoic and Early Cenozoic. Even then, the disn
Mesozoic tectonic event was notably less intense in the pre- year
3. REGIONAL GEOLOGY AND ACTIVE TECTONICS Mesozoic and Late Cenozoic eras. Recent tectonic activity started nov
OF WESTERN MONGOLIA in the end of the Oligocene or beginning of the Miocene epoch as
a result of collision between India and Eurasia (Molnar & 4.11
The pre-Cenozoic history of Mongolia, according to Penttila Tapponnier, 1975).
(1994), is dominated by three major orogenic systems which from Map
older to younger include: 1) Late Precambrian in northern In general, the active tectonic scheme of western Mongolia are thou
Mongolia (Salair or Baikalian), 2) Early Paleozoic (Caledonian) dominated mainly by the NW-SE trending right-lateral strike-slip feat
across central Mongolia, and 3) Late Paleozoic (Hercynian) fault systems like Mongolian Altay Fault Zone, roughly E-W settit
orogenesis throughout southern Mongolia. trending left-lateral strike-slip fault systems like Bolnay and Bogd head
fault zones with considerable reverse component, and generally and
The rock units representing the Late Precambrian (Baikalian NNE-SSW to NE-SW trending graben systems like Hövsgöl rift mov
orogeny) is exposed in a belt parallel to Lake Baikal and trends E- systems in northern Mongolia (Fig.2). North-south trending in th
W across northernmost Mongolia. The rock units of the Early surface ruptures are mostly normal faults with minor right-lateral due!
Paleozoic (Caledonian orogeny) wraps around the Baikalides, strike-slip movement. These different kinds of ruptures tend to run
trending northwest obliquely across the Mongolian Altay in NW within the different neotectonic zones. The:
Mongolia, roughly E-W across the southern Hangay in west- expr
T90°E T93°E land:
NG 15.05.1970 % a) S
e» à x. Æ meni rupti
se NU 100088?” XE: a narrc
Sra LA 3 LUvs Nuur us. activ
front
rupti
Figs.
Mon
Trad
some
; displ
DSi 7088 a tec
[611 7508P Mon
2 D basir
E > S. My D Mos
WA on A 2 ua a Mon
LEGEND 1 Ua; perv
FAULTS à ANI rever
—— Ruptures GOBI TIEN SHAN mour
epicenters UN en and 1
- M80 a rid a trend
oO 7.0<M<8.0 mA Tory with
o pre-recorded s
e ue mas fer] iin
I nens : 200 km med ul long
cz lakes Mer ^ wt | 102°E |105^E the C
Figure 2. Major faults and surface ruptures of western Mongolia as depicted from Landsat TM,
SPOT and Russian KOSMOS data. Many of the surface ruptures with paleo- and recent earthquakes m
represent the seismic activity of this region. Around 26 earthquakes higher than 6.6 magnitude are Mon
plotted in this figure corresponding to: 1-Bugsein Gol, 2-Chihtein, 3-Myangain, 4-Chandmani, 5- maxi
Bulgan, 6-Bij, 7-Busin Gol, 8-Jara Gol, 9-Sharga Nur, 10-Hujirt Gol, 11-Malchin, 12-Zuun Nur, 13- pres:
Egiin Dava, 14-Sagsai, 15-Ar Hotol, 16-Uneget, 17-Tsetserleg, 18-Bulnai, 19-Fu-yun, 20-Mondinsk, narro
21-Gobi Altai, 22-Bayan Tsagan, 23-Buuryn Hyar, 24-Mogod, 25-Uureg Nuur and 26-Tahiin Shar.
b)Str
ruptu
mass
616 Intemational Archives of Photogrammetry and Remote Sensing. Vol. XXXII, Part 7, Budapest, 1998
