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Inversion of half-graben basins
Comparison of analogue and numerical models
Extension followed by inversion
© Susanne Buiter
Basin inversion is the process of shortening an extensional sedimentary
basin whereby the basin fill
is uplifted and partially extruded, and pre-existing faults are re-used
[in the sense of Cooper et al., Geological Society Special Publication
44, 1989].
Mild to moderate basin inversion has been identified, for example,
on seismic profiles in the North Sea and the Alpine foreland.
It is characterised by uplift of the basin fill,
folding of syn- and post-rift sediments and
(partial) reactivation of normal faults.
Examples of strong or complete inversion can be found in
the Alps and Pyrenees. Folding, faulting, fault rotation, fault
reactivation and extrusion of the basin fill play a role in the generation
of sometimes complex deformational structures.
The pictures below give a snapshot of several basin inversion projects over
the years 2002-2009.
The two-dimensional visco-plastic numerical models use Sopale, a finite-element
code developed by the
Geodynamics Group
at Dalhousie University.
Susanne J.H. Buiter and O. Adrian Pfiffner, 2003,
Numerical models of the inversion of half-graben basins,
Tectonics 22 (5), 10.1029/2002TC001417
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We use both analogue and numerical experiments to study the inversion by
shortening of a symmetric sedimentary basin. The experiments start with a
pre-existing basin filled in part with weak layers simulating weak sediments.
Panien, M., S.J.H. Buiter, G. Schreurs and O.A. Pfiffner, 2006,
Inversion of a symmetric basin: insights from a comparison between
analogue and numerical experiments, in: Analogue and Numerical
Modelling of Crustal-Scale Processes, Buiter, S.J.H. and
Schreurs, G. (eds), Geological Society, London, Special Publication
253, 253-270
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The figure shows an (unpublished) example of the formation of a sedimentary basin by
extension and its inversion through contraction.
The model is 400 km wide by 35 km high, and the centre 200 km of the
modelling domain are shown.
Crust is pink, sediments are yellow.
a) 50 km of extension;
b) 60 km of extension,
the different shades of yellow indicate different times of
deposition of sediments;
c) post-rift sediments;
d) 10 km contraction, note the
syn-inversion sediments in red.
The frictional strength of all model materials softens with
increasing strain.
The grid in the figure
is used to track material properties and visualises deformation; it is
not the calculation grid (which is more dense).
The example below is from a model that features basin formation and basin
inversion in models that include the lithosphere and upper mantle.
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