An underwater "wind-gap" in the Ionian offshore of northern Calabria

Orographic reliefs are continuously created and modified in active continental tectonic settings, influencing the drainage pattern and interacting with it. It is not uncommon that stream capture occurs in these settings, causing major rearrangement of river courses. This process often produces a geomorphological feature known as wind gap, i.e. a gap through which a stream once flowed but that is now abandoned and dry as a result of the capture. Analizing a high resolution 3D seismic data set, kindly made available by ENI S.p.A., we discovered a similar feature in the Ionian offshore of the Crotone peninsula, northern Calabria. This underwater region is characterized by intense tectonic activity that is partly controlled by the occurrence of a mobile substrate, possibly overpressured shales. The relevant uplift affecting the nearby Calabria onshore can also contribute to promote gravitational instability. In this setting the "wind gap" is represented by a stretch of a downslope weakly incised channel that has soon been abandoned as a result of the growth of a tectonic structure. The course of the new submarine channel runs sub-parallel to the coast for a long strecth, before taking a downslope trajectory. The present-day submarine channel is deeply incised, showing at least two main phases: a deep valley incision containing an axial valley with a much lower relief, which likely represents the current route of turbidite flows. The main channel valley results from the major erosional episode that affected the continental slope offshore northern Calabria. The limited incision in the abandoned channel strecth suggests that drainage rearrangement occurred in the very early stage of channel incision. Therefore, the estimated age of the tectonic deformation that is responbile for originating the "wind gap" can offer a useful hint on the timing of onset of erosion in this area.