Caprock

Caprock is also found in salt domes and on the top of mesa formations.

In the petroleum industry, caprock is any nonpermeable formation that may trap oil, gas or water, preventing it from migrating to the surface.

This caprock can prevent hydrocarbons from migrating to the surface, allowing them to accumulate in a reservoir of oil, gas and water.

The tops of salt domes such as in the Gulf of Mexico dissolve in a characteristic manner, and can range between 0–1500 ft thick.

The anhydrite and gypsum react with organic material to form calcite.

Horseshoe Falls , part of the Niagara Escarpment . The dark thin layer in the foreground, where water is not yet running, is the caprock.