Three-dimensional Modelling of Crustal Deformation Coupled to Surface Processes

   
                 
Principal Investigator

Jean Braun

Research School of Earth Sciences

Co-Investigators

David Burbidge

Jonathan Tomkin

Research School of Earth Sciences

Philippe Fullsack

Department of Oceanography

Dalhousie University, Halifax NS, Canada

 

Projects

m22 - VPP, PC

The crust is the outermost layer of the solid Earth
which is sandwiched between the underlying mantle
and the overlying hydrosphere. Deformation of the crust is driven by tectonic forces originating in the mantle and leads to the formation of all geological features observed today at the surface of the Earth. The crust is also subjected to erosion and sedimentation along its interface with the hydrosphere. This project aims at understanding the complex behaviour of the crust-mantle-hydrosphere system with a particular focus on orogenic belts that develop along convergent tectonic plate boundaries.
     
               

       
               
                 
What are the results to date and the future of the work?

We have demonstrated the important role that climate, through erosion and sedimentation, plays in determining the style of crustal deformation in orogenic belts. A typical example of this interaction is in the South Island (New Zealand) where the patterns of rock exhumation strongly reflect the patterns of asymmetric precipitation across the main divide. This behaviour was clearly demonstrated by combining the results of recent computations with a new geochronological dataset we collected in New Zealand.

We have also demonstrated the importance of the interplay between fluvial and glacial erosion in temperate mountain belts which have seen an alternance of climatic conditions during the last 2 million years.

We have also developed a new algorithm for the solution of the force balance equation that is based on the Discrete Element Method. The new method is not restricted by the approximation of small deformation and is now used to investigate (i) the structural development of accretionary wedges along oceanic subduction zones and (ii) the dynamical evolution of compressional belts driven by subduction of the underlying mantle.

                 
- Appendix A

 
                 

       

We are now developing new methods to permit greater flexibility in the coupling of crustal deformation with the underlying flowing mantle and overlying hydrosphere by extending our 2-D irregular parameterization methods to 3-D.

What computational techniques are used?

Finite Element Method with dynamic, self-adaptive, irregular discretization and Discrete Element Method to solve the equations of force balance in a visco-elasto-plastic solid. CASCADE algorithm to solve a set of linear geomorphic equations.

Publications

J. Braun, R.D.Shaw, Contrasting styles of lithospheric deformation along the northern margin of the Amadeus Basin, central Australia. In: Structure and Evolution of the Australian Continent, J. Braun, J. Dooley, B. Goleby, R. Vanderhilst and C. Klootwijk (eds), Geodynamics Series, v. 26, AGU, 139-155, 1998.

J.Braun, R.D Shaw, Extension in the Fitzroy Trough, Western Australia: an example of reactivation tectonics. In: Structure and Evolution of the Australian Continent, J. Braun, J. Dooley, B. Goleby, R. Vanderhilst and C. Klootwijk (eds), Geodynamics Series, v. 26, AGU, 157-173. 1998

P.A. van der Beek, J. Braun, Numerical modelling of landscape evolution on geological time scales: A parameter analysis and comparison with the south-eastern highlands of Australia, Basin Res. v.10, 49-68.1998.

G. E Batt, J.Braun, The tectonic evolution of the Southern Alps, New Zealand: Insights from fully thermally coupled dynamical modeling. Geophysical Journal International, v.136, 403-420, in press.

P.A. van der Beek, J. Braun, Controls on post-mid Cretaceous landscape evolution in the southeastern highlands of Australia : Inferences from numerical surface process models, J. Geophys. Res., in press.

P.A. van der Beek, J. Braun, K. Lambeck, The post-Palaeozoic uplift history of south-eastern Australia revisited: Results from a process-based model of landscape evolution , Austr. J. Earth Sci., in press.

J. Braun, D. Zwartz, J.H. Tomkin, A new surface processes model combining glacial and fluvial erosion, Annals of Glaciology, in press.

J.H.Tomkin, J. Braun, Simple models of drainage re-organisation on a tectonically active ridge system, New Zealand Journal of Geology and Geophysics, in press.

       
Appendix A -