Overview of Current Research:

My current research involves physical and mathematical modelling of the structural evolution of foreland fold and thrust belts such as the Canadian Rocky Mountain Fold-Thrust Belt. Such belts form when flat-lying sedimentary strata are subjected to horizontal compression due to plate convergence and undergo horizontal shortening and vertical thickening by folding, thrust- faulting and pervasive strain (layer-parallel shortening).

The objectives of the research are to determine how such folds and faults nucleate and propagate in time and space, how the processes of folding and faulting are inter-related, and how they are influenced by stratigraphic and structural heterogeneities. This work aims to aid exploration for petroleum within fold-thrust belts by improving our understanding of structural geometry and sequence of trap formation, thus aiding assessment of reservoir potential.

In the program of physical modelling, scaled models are constructed of materials such as Plasticine modelling clay and silicone putty (mechanical analogs for rocks such as limestone and shale, respectively). To achieve dynamic scaling, the models are deformed within a 20,000-g centrifuge (centrifugal force simulating the force of gravity) (see Ramberg 1981; Dixon & Summers 1985) in the Experimental Tectonics Laboratory at Queen's University. The models contain bedding anisotropy and can include stratigraphic complexities such as facies boundaries, and pre-existing basin architecture such as early rift structures. They can simulate specific natural examples in addition to generic situations.

We have previously documented fold-fault relationships and patterns of nucleation and propagation in plane-layered sequences ( Dixon & Liu 1991; Dixon & Tirrul 1991; Liu 1990; and Liu & Dixon 1990, 1991, 1995). Current work has three foci: 1) detailed investigation of along- strike propagation of folds and related thrusts and displacement transfer mechanisms; 2) influence of stratigraphic heterogeneities such as facies boundaries on nucleation and propagation of folds and faults; and 3) influence of structural heterogeneities such as pre-existing normal (growth) faults on fold-thrust nucleation and propagation. (see examples)We are also attempting to simulate specific natural examples from the Rocky Mountains and other fold-thrust belts, and we are integrating geological and geophysical (seismic) field data with the model studies.

The mathematical modelling applies the finite-element modelling (FEM) technique using the program ANSYS (see Liu & Dixon (1995) for a preliminary report on this work). One aspect of this approach is to apply FEM to simple centrifuge models, in order to validate the FEM results against observed geometry and kinematic evolution of model structures. Once we have confidence in the ability of FEM to generate realistic high-amplitude structures as documented in the physical models, we will use it to derive information on the dynamics of the physical models and will also apply it to specific natural situations. One goal is to derive estimates of stress levels associated with nucleation and propagation of thrust ramps. This dual approach of combining centrifuge physical modelling and mathematical finite-element modelling has not to our knowledge previously been applied to fold-thrust structures.

The research team includes my M.Sc. students Evsen Aydemir (B.Sc., Geology and Geophysics, University of Calgary) and Domenica Mastromatteo (B.Sc., Mechanical Engineering, McGill University), and research assistant Julia Blackburn (a final-year B.Sc. Geological Engineering student at Queen's). The research is part of the Foothills Research Project, a Collaborative Research and Development Project of which I am a co-Principal Investigator together with Dr. Don C. Lawton and Dr. Deborah A. Spratt of the University of Calgary. The project is funded by NSERC and a consortium of petroleum industry companies.

You can email me at dixonj@post.queensu.ca

Literature References

Dixon, J.M. & Liu, S. 1991. Centrifuge modelling of the propagation of thrust faults.
In: Thrust Tectonics (edited by McClay, K.). London: Chapman & Hall, 53-70.

Dixon, J.M. & Summers, J.M. 1985. Recent developments in centrifuge modelling
of tectonic processes: equipment, model construction techniques and rheology
of model materials. Journal of Structural Geology 7, 83-102.

Dixon, J.M. & Tirrul, R. 1991. Centrifuge modelling of fold-thrust structures in a
tripartite stratigraphic succession. Journal of Structural Geology 13, 3-20.

Liu, S. & Dixon, J.M. 1990. Centrifuge modelling of thrust faulting: strain partitioning
and the sequence of thrusting in duplex structures. In Deformation Mechanisms, Rheology
and Tectonics (edited by Knipe, R.J.). Geological Society of London Special Publication 54, 431-444.

Liu, S. & Dixon, J.M. 1991. Centrifuge modelling of thrust faulting: structural variation
along strike in fold-thrust belts. Tectonophysics 188, 39-62.

Liu, S. & Dixon, J.M. 1995. Localization of duplex thrust-ramps by buckling:
analog and numerical modelling. Journal of Structural Geology 17, 875-886.

Ramberg, H. 1981. Gravity, Deformation and the Earth's Crust in Theory,
Experiments and Geological Applications, 2nd Ed. Academic Press, London.

Links to more information

The Experimental Tectonics Laboratory

Illustrations of Recent Fold-Thrust Models

Foothills Research Project

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last revision: 14 October 1999