Geology Reference
In-Depth Information
95°E
100°E
Small
Circle
Radius
Tibetan
Plateau
30°N 30°N
Him
Eastern
Syntaxis
25°N
Fig. 10.20 Three Rivers shear
zone in southeastern Tibet.
A. Map of the anomalous upper
reaches of the Salween, Mekong,
and Yangtze Rivers where they
flow in close proximity and
parallel to each other as they exit
the Tibetan Plateau. B. Map of the
Mekong catchment that highlights
the region of unusually narrow
catchment width. C. Comparison
of upstream changes in normalized
river width between the Mekong
and six “typical” rivers. Basin
widths were measured at 20
equally spaced points spanning the
length of each river, normalized to
unity, and plotted on a log scale.
Whereas significant narrowing at
basin outlets is common, the
mid-course narrowing of the
Mekong is clearly anomalous.
D. River length versus basin
width for the world's 50 longest
rivers compared to the Three
Rivers. The narrowness of the
three river basins attests to the
large-scale crustal shortening in
this region. E. Schematic tectonic
model of the impact of the corner
of a rigid indentor (India) with
Tibet and Eurasia. Convergence
north of the indentor drives
catchments closer together,
whereas dextral shear along the
right-hand margin of the indentor
causes both necking of the basins
and river alignment. Modified after
Hallet and Molnar (2001).
India
95°E
A
100°E
30
3
20
width
anomaly
25
15
20
15
2
10
Mekong
Yangtze
Typical
Rivers
10
5
Salween
5
Mekong
Basin
Mekong
0
0
1
0
5
10
15
0.01
0.1
1.0
10
2
3
4
Easting (km x 100)
Log River Length (km)
B
C
Normalized Width
D
Eurasia
Three
Rivers
Shear
Zone,
South-
East
Tibet
B
B
A
A
India
(Northeast
Indentor
Corner)
FIXED
E
 
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