How to make continental reconstructions: the importance of the knowledge of high strain along former plate boundaries

Continental reconstructions became a geological problem after the rise of continental drift. With plate tectonics, it became easy to make reconstructions once ocean-floor magnetic anomaly stripes became available. However, for times before the medial Jurassic, continental reconstructions must depend on palaeomagnetism, palaeoclimatology and palaeobiogeography. All three methods give rough latitudinal control, whereas obtaining longitudinal control has proved elusive. We here show that a detailed knowledge of strain history, i.e. careful mapping and integrating change of shape in rock bodies and the displacements implead by them in orogenic belts between formerly separate continental rafts may also provide longitudinal control of relative continental positions and thus enable the geologist to generate displacement paths during the drift histories of continents before the early Jurassic. We present below two examples of continental reconstructions, in which strain histories of rock packages between two cratons play a predominant role, namely the Altaids, mainly in the Phanerozoic, and the Saharides, mainly in the Neoproterozoic.