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Application to the Iberian Margin

IMEDL BENCHMARKING EXERCISE Integrated Structural, Thermal and Isostatic Modelling of Lithosphere Deformation:. Application to the Iberian Margin. Stuart Egan. Physical constants and variables (e.g. geothermal gradient) are assumed for the lithosphere. Modelling Approach.

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Application to the Iberian Margin

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  1. IMEDL BENCHMARKING EXERCISEIntegrated Structural, Thermal and Isostatic Modelling of Lithosphere Deformation: Application to the Iberian Margin Stuart Egan

  2. Physical constants and variables (e.g. geothermal gradient) are assumed for the lithosphere. Modelling Approach Deformational parameters (e.g. fault deformation) are obtained from data.

  3. Integrated Model - extension

  4. Iberia Seismic Experiment - 1

  5. Galicia Bank Galicia Interior Basin Deep Galicia Basin Peridotite Ridge ISE-1 Interpretation

  6. ISE-1 Fault Deformation Total extension = 104.5 km Overall Beta = 1.5

  7. Galicia Bank Galicia Interior Basin Deep Galicia Basin Peridotite Ridge Uniform Lithosphere Extension Crust Moho Detachment = 15 km Pure shear Beta = 1.36 Beta = 1 Thermal subsidence Syn-rift Time = 200Ma Te = 5 – 20 km

  8. “Cool” Lithosphere: “Warm” Lithosphere: Reconciliation of fault deformation and overall thinning of the crust – depth dependent stretching Adapted from Braun and Beaumont, 1989

  9. Galicia Bank Galicia Interior Basin Deep Galicia Basin Peridotite Ridge Crust Detachment = 15 – 4 km Moho Pure shear Beta = 8 Beta = 1 Water infill Sediment infill Time = 200Ma Te = 5 – 20 km

  10. Depth Data(Pinheiro et al, 1996)

  11. Water infill Sediment infill Time = 200Ma Te = 5 – 20 km

  12. Te = 3 km Galicia Interior Basin Galicia Bank Deep Galicia Basin Peridotite Ridge Te = 10 km Te = 25 km Changing Flexural Rigidity

  13. Summary • 24 crustal faults have been interpreted in section ISE-1, exhibiting a total horizontal extension of about 105 km (Beta = 1.5) • Kinematic modelling based upon uniform lithosphere extension constrained by fault deformation generates a realistic basement geometry across the Iberian margin, but fails to reproduce overall subsidence due to insufficient thinning of the crust. • The magnitude of fault controlled deformation has to be reconciled with the overall attenuation of the crust to generate a realistic magnitude of subsidence. Can this be explained by a gradually shallowing necking depth? • Kinematic modelling can be used to assess the values and importance of a number of deformational and physical parameters in margin evolution. For example, model results suggest that the flexural rigidity of the Iberian margin is relatively high.

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