A Salt dome is a geological structure that grows and develops as sediments are being deposited around them.
It is formed by the intrusion of salt (low density, ductile mineral, is gravitationally mobilized by sediment loading, forming a variety of upwelling structures) into overlying sediments (higher density).
A pier-cement salt dome is one that has pushed up so that it penetrates the overlying sediments, leaving them truncated.
Formations above the salt plug are usually arched so that they dip in all directions away from the center of the dome and create excellent cap rocks-subsalt layers.
Salt tectonics is the main element responsible for the creation of the structure and for other prospects in Caspian basin (Pre-Caspian salt basin).