Deformation of a halite-anhydrite sequence under bulk constriction: Preliminary results from thermomechanical experiments

A new deformation apparatus has been used to model the internal kinematics of salt diapirs. We deformed layers of Gorleben anhydrite, embedded in Asse halite, under bulk constriction with the layers being oriented parallel to the major stretching axis, X, of the finite strain ellipsoid. Further deformation conditions were as follows: T = 345°C, σ_max = 4.59 MPa, dε/dt = 10⁻⁷ s⁻¹, e_{X (max)} = 122%. 3D-images, based on computer tomography, suggest a strong interaction between folds and boudins, both of which affecting the anhydrite layer. D₁-folds, with axes subparallel to X, are hardly developed. D₂-folds, with axes subperpendicular to the layer, affect the boudins resulting in oblique orientation of the latter. With increasing layer thickness the length of boudins increases. However, the geometric data are not in line with results of analytical solutions derived for power-law material and with geometric data of folds and boudins produced by analogue experiments.