David Fernández-Blanco , Gino de Gelder , Robin Lacassin , Rolando Armijo

This review shows how collective analysis of morphotectonic elements on uplifting rift margins can constrain the mechanical behaviour of continents during early rifting. This is shown for the modern Corinth Rift, one of the fastest-extending and most seismically active continental regions worldwide. We reconstruct the growth of the normal fault system that accommodates most of the rift strain and the uplift of the rift margin it bounds, from onset to present and at rift scale. Our approach allows first-order inferences on the mechanics and evolution of the rift, and can be used in other areas of early continental rifting.

We review and re-assess known geologic evidence in the Corinth Rift, and compile morphotectonic elements into a new map. We analyse the rift topo-bathymetry, and the footwall relief, river catchments and tectonic knickpoints in its uplifting margin. We also review studies that constrain the growth of normal faults using morphotectonic elements in their footwall, and propose a novel theoretical framework to reconstruct fault time-evolution during early rifting. We couple known and new data to derive fault displacement profiles in time, and use the theoretical framework to infer the history of growth and linkage of rift border faults, in turn constraining rift growth mechanics and evolution.

Our rift-scale morphotectonic investigation shows that the current rift-bounding faults are kinematically coherent at depth and constitute a fault >80 km in length. This composite master fault grew along-strike from the rift centre, linking and integrating individual fault segments that developed co-linearly at earlier times. The observed fault elastic flexure, footwall relief wavelength and high uplift and slip rates throughout the rift margin suggest the border fault is steep and highly localized in strain, and transects the entire seismogenic layer growing in a long-term strong elastic lithosphere.

Integration of previous and our new findings suggest the Corinth Rift evolved in two distinct extensional phases. These extensional phases are delimited by the fast, overwriting growth of the new rift-forming fault, that switched rift mechanics in a ~300 kyr timespan, and controls rift evolution thereafter. The new rift-forming fault enlarges the modern rift as an asymmetric half-graben, along and across strike, superimposed onto the preceding ~4 My distributed extension.