[Fred Nerks]

A fascinating subject:

Morphology and structure of the Camarinal Sill from high-resolution bathymetry: evidence of fault zones in the Gibraltar Strait

The age of faulting is poorly constrained in both cases.LINK

Together with existing evidence of faults onland, the presence of these fault zones implies that they could be responsible for,

or have contributed to, the opening of the Gibraltar Strait.

[gleeaikin]

It might make sense that if the land bridge was between Africa and Spain had dried out a bit, then when the sea level rose and it go wet, quake faults could have been lubricated and slipped aiding the flooding process along with scouring.