Himalayan foreland Foreland basins

Huge potential for erosion in modifying stresses is nowhere better illustrated than Himalaya; however critical taper theory only approximates outer edge of system

Collisional mountain belt

Flexure of beams Infinite Semi-infinite Forebulge Accommodation space (Hole) Pinchout point

Flexure of the lithosphere M0M0 Amount of flexure Flexural parameter Flexural rigidity

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) Subsidence = Sea-level Topographic load (L topo ) f(L topo Subsurface load (L sub ) + L sub V plate + f(V plate ) V thrust = V thrust dx topo /dt f(dx topo /dt) + f(V plate ) V onlap V onlap = dx topo /dt + f(V plate ) V plate is key determinant of foreland basin metrics,Te)

Early analyses System simulated by a tapered wedge overthrusting an elastic beam with surface redistribution by diffusion (Flemings & Jordan 1989; Sinclair et al., 1991)

Pro-peripheral foreland basin Retro-peripheral foreland basin Geometry Tectonic subsidence Chronostratigraphy time distance Onset of orogenesis growth Steady-state Onset of orogenesis growth Steady-state Onset of orogenesis growth Steady-state depth Naylor & Sinclair, submitted to Basin Research

Taiwan

Chronostratigraphy time distance Onset of orogenesis growth Steady-state time

Seismicity (Jer-Ming Chiu)

Aquitaine Basin Ebro Basin Topography Topographic cross-section Geodynamic model S N The Pyrenees

Thrust propagation consumes foreland basin (D. Garcia-Castellanos et al, 1997)D. Garcia-Castellanos

Price 1973 Flexural Basin Concept Flexure Thrusting Foreland basin Pinchout point

Pro-peripheral basin (Over subducting slab lots of thrusting)

basement Upper Senonian Lower Cretaceous Oligocene Upper Eocene Lower Eocene (sandst.) Lower Eocene (carbonates) Palaeocene 0 50km Foreland basin succession Ebro Basin Aquitaine Basin - Ebro Basin (Pro-peripheral) from Verges et al., Aquitaine Basin (Retro- peripheral) from Desegaulx and Brunet orogenesis time distance time (Retro) (Pro)

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