glacial valleys, with long narrow openings that rise upward near the outer shelf, thereby creating sills.[4]
Aquatic sills as barriers
Circulation barriers
Aquatic sills can influence water circulation by restricting the movement of bottom water masses, resulting in partial to total separation of two basins. The restricted water circulation affects temporal variations in salinity and can result in oxygen depletion in deeper water masses.[5]
Messinian Crisis, 5.96-5.33 million years ago, when the Mediterranean Sea experienced a near complete drought. During the Zanclean Flood that followed, two deep channels (Canal Norte and Sur) were scoured out. During the late Miocene and during the Early Pliocene, a north-south dominated tectonic stress field created pull-apart basins under a transtensional regime, thereby forming the gateway.[3]
