Oil traps

© CNRS Photothèque/Jean-Jacques Cornée
© CNRS Photothèque/Jean-Jacques Cornée

The Realmonte salt mine in Sicily, Italy. The sodium chloride (rock salt) appears as white layers and the potassium salts as beige. These vertical layers were formed at the time of the Messinian Salinity Crisis – a geological event that occurred around five million years ago during the late Miocene Epoch, when the Strait of Gibraltar was temporarily closed, causing the Mediterranean Sea to dry up.

These layers give us an idea of the diapiric traps of the same age buried within the Earth’s mantle (domes or anticlinal folds in which the dense overlying rocks have been ruptured by the squeezing out of less dense, plastic salt rock). Salt diapirs are a type of geological formation that can trap large concentrations of hydrocarbons (oil or gas).