Basin migration caused by slow lithospheric extension

Sedimentary basin migration caused by low lithospheric extension rates is investigated using a two-dimensional dynamic numerical model of the lithosphere. We find that continental breakup will eventually occur when larger extension velocities are used. The duration of rifting prior to continental breakup is dependent on the extension velocity. Stretching the lithosphere with lower velocities does not lead to breakup. Instead, the locus of maximum extension migrates. Deformation localizes outside the first formed basin that is in turn uplifted. This basin then becomes a ‘cold spot’ in the area. In this case, syn-rift cooling predominates; the lithosphere regains its strength during stretching instead of becoming weaker, and the lithosphere necking zone becomes stronger than surrounding regions. The transition velocity is, for the cases studied, about 8 mm/yr, while the locus of maximum thinning migrates after about 50–60 Myr. A comparison with observations of the mid-Norwegian, Galicia and ancient South Alpine margins shows a close resemblance of important features.