Geology Reference
In-Depth Information
Compensation and Topography in Extension
A
isostatic balance
before extension
crust
mantle
half
graben
mantle compensation
(wider, lower deflection)
wavelength
B
lower crustal compensation
(narrower, higher deflection)
wavelength
deflection)
Fig. 10.49 Models for compensation and
topography in extensional regimes.
A. The “negative” load of a half-graben fill induces
regionally compensated footwall uplift. For the
same amount of extension, compensation in the
mantle yields a broader, but lower, footwall
uplift (B) than does lower-crustal compensation
(C). Modified after Masek et al . (1994a).
C
lower crust (low viscosity)
Tarim
Basin
Lower Crustal Flow in Tibet
40°N
?
?
?
?
?
?
35°N
?
?
?
Lower
?
Lower
Crustal
Flow
Tibetan
Tibetan
Plateau
Tibetan
Plateau
Lower
Crustal
Plateau
Crustal
Flow
Sichuan
Basin
Flow
30°N
a
a
Fig. 10.50 Proposed lower crustal flow
in eastern Tibet.
The topography of the Tibetan Plateau
reveals a broad, gentle ramp to the
southeast, steep topographic gradients
adjacent to the Sichuan Basin, and less
well-defined ramp on the north side of the
Sichuan Basin. Stiff, old crust underlying
the Sichuan Basin is interpreted to impede
outward flow of ductile lower crust from
beneath Tibet. Courtesy of Richard Lease.
minimal
minimal
Cenozoic
minimal
Cenozoic
shortening
Cenozoic
shortening
25°N
India
shortening
N
20°N
110°E
100°E
90°E
Search WWH ::




Custom Search