Role of tectonic burial and temperature on the inversion of inherited extensional basins during collision
Résumé
The style of inversion of inherited extensional basins in the Western Alps is investigated
through thermo-mechanical modelling. Two-dimensional models consist of a half-graben embedded
in a relatively strong crust (basement) and filled with weak syn-rift sediments (cover). We investigate
the relative influence of the internal friction (μ) of the basin-bounding normal fault, tectonic burial (h)
under an overlying nappe and the geothermal gradient. We use a viscoplastic model with symmetrical
shortening. The inherited normal fault is implemented as a curved thin body with a variable friction
coefficient (μ) ranging from 0.1 to 0.6. The style of basin inversion is controlled at shallow depth by
the internal friction coefficient, whose influence decreases with the increase of both burial depth and
geothermal gradient. With increasing burial and/or geothermal gradient, fault reactivation is inhibited
and distributed deformation in the basement induces the vertical extrusion of the cover. The basin
inversion is accompanied by distributed deformation in the cover and by the shearing of the basin and
basement interface. The results are consistent with the style of inversion of inherited half-grabens in
the external Western Alps, where no significant fault reactivation occurred owing to tectonic burial
underneath the Alpine internal units during the early Alpine collision.