Corinth Rift transient rivers characterize evolving crustal-scale elastic flexure

Crustal elastic flexure on the sides of rift-forming faults is a key feature to characterize continental rifting processes that has never been examined by means of transient river drainages on rift footwalls. The elastic flexure dynamics of the main shoulder of the fast-extending and asymmetric Corinth Rift (Greece) are recorded virtually in 3D in its fluvial geomorphology. We explore the evolution of the mechanical flexure of the lithosphere along rift full length by means of DEM-based river profile analysis of a series of footwall catchments orthogonal to rift master fault. We show that elastic footwall flexure prescribes the first-order geometry of longitudinal river profiles as a function of master fault onset time and/or slip rate. Flexure amplitude is maximum in the center of the rift, where drainage reversal of two catchments suggest very fast slip rates on the master fault, and decays (i) sharply to the east, where river profiles are near equilibrium with the modern displacement field, and (ii) gently to the west, where transient river profiles exhibit a morphology consistent with relatively lower rates of flexural uplift and abundant evidence for active drainage reorganization. Taken together, these observations are consistent with landscape respond to a time transgressive fault initiation and uplift history since a recent shift in tectonic boundary conditions, probably younger 620 ka. The singularity of drainage reversal by footwall flexure is an extreme setting that suggests a radical increase in master fault slip rate due to an abrupt tectonic change. Besides, the full-rift extent of flexure requires a steep fault growing in a strong lithosphere. This is at odds with Corinth Rift models based on fault migration basinward and shallow detachments and supports the hypothesis of rift evolution associated with the growth by propagation of the North Anatolian Fault.