19. Anticlines and Salt Domes, Gulf Coast, Iran
One of the most spectacular examples of anticlinal fold structures in the world, these folds lie on the shores of the Persian Gulf, on the north shore of the Strait of Hormuz, near the important city of Bandar Abbas. They form the foothills of the Zagros Mountains, which run north-northwesterly through Iran, and were formed when the Arabian shield butted up against the western Asian continental mass, the collision taking place only 5–10 million years ago.
Subduction still continues slightly further east, beneath Baluchistan, but is inactive in the Gulf itself. Although not obvious in the photograph, the shortening expressed by the folds is accompanied by extensive thrusting on easterly dipping planes. All the deformation is geologically young; the folded sediments are Paleogene and Neogene. Simple anticlinal structures are well known as classic traps for hydrocarbons, and some producing wells are located in the area.
The other features that are prominent in this photograph are the dark circular patches. These represent the surface expression of salt domes that have risen diapirically from the Cambrian Hormuz salt horizon through the younger sediments to reach the surface. Only in a hot arid environment such as that of the Gulf can the soluble salt escape rapid erosion. Salt domes also are frequently favorable sites for trapping hydrocarbons.
STS-41G, October 1984. Picture #17-37-105.