Sedimentary basin migration and microcontinent formation could be the result of deformation redistribution, in which the emplacement of an underplated mafic body (UPMB) may play an important role. In this study, a 2D finite-element model is used to examine the redistribution of the deformation that can be triggered by a UPMB. It is shown that three modes of deformation redistribution can exist: (1) a shift-completed mode where the deformation is completely redistributed into the newly weakened region; (2) a transition mode where the deformation is redistributed, but extension is accommodated by thinning in both regions; (3) a shift-failed mode where the deformation is not redistributed. Whether or not the deformation is redistributed depends on the configuration of the UPMB and on the initial rheological heterogeneity in the initially deformed region. However, it becomes difficult for any UPMB to initiate the redistribution of the deformation once the stretching factor in the first deformed region exceeds a critical value. The microcontinent formations observed in the Indian Ocean, in the Norwegian–Greenland Sea, in the Red Sea–Afar region and in the western Mediterranean are particularly discussed in relation to the transition mode, providing some important geodynamic implications.