Transcript Foreland basins

Himalayan
foreland
Foreland
basins
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Collisional mountain belt
Flexure of beams
Pinchout
point
Forebulge
Accommodation space
(Hole)
Infinite
Semi-infinite
Flexure of the lithosphere
Amount of flexure
w( x) 
 2ex / 
2D
x
  M 0 sin  V0  M 0  cos 



x
Flexural
rigidity
M0

4D
1/ 4

 Flexural parameter
  
 g  m   i  
Basin types – Ocean-arc boundary
Basin types – Orogenic belts
Taiwan
Mountain belt/foreland basin coupling
Initial recognition of dependence of foreland basin on thrust
geometry and growth (Beaumont, 1981; Jordan, 1981)
dxtopo/dt
Topographic load (Ltopo)
Vthrust
Sea-level
Vonlap
Subsurface load
(Lsub)
Vplate
Vplate is key determinant of foreland basin metrics
Subsidence = f(Ltopo + Lsub ,Te) + f(Vplate)
Vthrust = f(dxtopo/dt) + f(Vplate)
Vonlap = dxtopo/dt + f(Vplate)
Early analyses
System simulated by a tapered
wedge overthrusting an elastic
beam with surface redistribution
by diffusion
(Flemings & Jordan 1989;
Sinclair et al., 1991)
Retro-peripheral foreland basin
Pro-peripheral foreland basin
Geometry
Steady-state
time
time
Chronostratigraphy
growth
Tectonic
subsidence
depth
Onset of
orogenesis
growth Steady-state
Onset of
orogenesis
distance
Onset of
orogenesis
growth Steady-state
depth
distance
Naylor & Sinclair, submitted to Basin Research
Taiwan
Taiwan
time
time
Steady-state
growth
distance
Onset of
orogenesis
distance
Chronostratigraphy
The Pyrenees
Bay of Biscay
Topography
Barcelona
`A
N
Mediterranean
S ea
3000
Ebro Basin
0
S
Geodynamic
model
Aquitaine 2000
Basin
1000
50
100
150
200
0
Topographic
cross-section
N
Elevation (m)
50 km
Thrust
propagation
consumes
foreland basin
(D. Garcia-Castellanos et al, 1997)
Flexural Basin Concept
Flexure
Price 1973
Pinchout point
Foreland basin
Thrusting
Wedge-top
basins: Ager
Tremp
Pobla Senterada
Boixols
Sierra Marginales
Morreres
Montsec
2
)O
O
0
RR
-2
-4
100
80
60
40
20
X 2.5 vert. exag.
Pro-peripheral basin (Over subducting slab lots of thrusting)
0
Ebro Basin
Aquitaine Basin
(Pro)
(Retro)
Upper Senonian
Lower Cretaceous
basement
time
time
Oligocene
Upper Eocene
Lower Eocene (sandst.)
Lower Eocene (carbonates)
Palaeocene
distance
distance
0
Foreland basin
succession
50km
Foreland Basin Summary
• Foreland basins are elongate basins located
at ocean-continent and continent-continent
collision zones
• They form in flexural depressions
– The flexural depression can be modelled using an
elastic beam
– The growth of topography loads the beam
• The basin is bound by the thrust front and the
stable craton
• The advection of the basin fill towards the
mountain belt creates accommodation space
• The basin is consumed as the thrust front
propagates out
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