The Hormuz Formation, Hormuz Series, Hormuz Evaporites or Hormuz Group is a sequence of

evaporite An evaporite () is a water- soluble sedimentary mineral deposit that results from concentration and crystallization by evaporation from an aqueous solution. There are two types of evaporite deposits: marine, which can also be described as ocean ...

s that were deposited during the Ediacaran (Late

Neoproterozoic The Neoproterozoic Era is the unit of geologic time from 1 billion to 538.8 million years ago. It is the last era of the Precambrian Supereon and the Proterozoic Eon; it is subdivided into the Tonian, Cryogenian, and Ediacaran periods. It is prec ...

) to

Early Cambrian The Cambrian Period ( ; sometimes symbolized Ꞓ) was the first geological period of the Paleozoic Era, and of the Phanerozoic Eon. The Cambrian lasted 53.4 million years from the end of the preceding Ediacaran Period 538.8 million years ago ...

, a period previously referred to as the Infra-Cambrian. Most exposures of this sequence are in the form of emergent

salt diapir A salt dome is a type of structural dome formed when salt (or other evaporite minerals) intrudes into overlying rocks in a process known as diapirism. Salt domes can have unique surface and subsurface structures, and they can be discovered using ...

s within

anticline In structural geology, an anticline is a type of fold that is an arch-like shape and has its oldest beds at its core, whereas a syncline is the inverse of an anticline. A typical anticline is convex up in which the hinge or crest is the ...

s of the

Zagros fold and thrust belt The Zagros fold and thrust belt (Zagros FTB) is an approximately long zone of deformed crustal rocks, formed in the foreland of the collision between the Arabian Plate and the Eurasian Plate. It is host to one of the world's largest petroleum p ...

. As a result of their involvement in post-depositional

salt tectonics upright=1.7 Salt tectonics, or halokinesis, or halotectonics, is concerned with the geometries and processes associated with the presence of significant thicknesses of evaporites containing rock salt within a stratigraphic sequence of rocks. This ...

, the internal stratigraphy of the sequence is relatively poorly understood. They are the lateral equivalent of the evaporite-bearing Ara Group in the

South Oman Basin South is one of the cardinal directions or compass points. The direction is the opposite of north and is perpendicular to both east and west. Etymology The word ''south'' comes from Old English ''sūþ'', from earlier Proto-Germanic ''*sunþaz ...

Distribution

The Hormuz Formation is known from a wide area of the

Zagros Mountains The Zagros Mountains ( ar, جبال زاغروس, translit=Jibal Zaghrus; fa, کوه‌های زاگرس, Kuh hā-ye Zāgros; ku, چیاکانی زاگرۆس, translit=Çiyakani Zagros; Turkish: ''Zagros Dağları''; Luri: ''Kuh hā-ye Zāgr ...

and around and beneath the

Persian Gulf The Persian Gulf ( fa, خلیج فارس, translit=xalij-e fârs, lit=Gulf of Fars, ), sometimes called the ( ar, اَلْخَلِيْجُ ٱلْعَرَبِيُّ, Al-Khalīj al-ˁArabī), is a mediterranean sea in Western Asia. The bod ...

. Two main depositional basins have been recognised, the North Gulf and South Gulf Basins, separated by the Qatar Arch. The basins were formed as a result of extensional tectonics towards the end of the

Pan-African Orogeny The Pan-African orogeny was a series of major Neoproterozoic orogenic events which related to the formation of the supercontinents Gondwana and Pannotia about 600 million years ago. This orogeny is also known as the Pan-Gondwanan or Saldanian Oro ...

. The main structure formed during this period were NW-SE trending dextral (right lateral) strike-slip faults and NE-SW trending

extensional fault An extensional fault is a fault caused by stretching of the Earth's crust. Stretching reduces the thickness and horizontally extends portions of the crust and/or lithosphere. In most cases such a fault is also a normal fault, but may create a ...

Stratigraphy

Most occurrences of the Hormuz Formation are highly disturbed tectonically. However, a broad stratigraphy has been recognised.

Effect on Zagros structure

Halite layers within the Hormuz sequence form the most important decollement level within the Zagros fold and thrust belt. The presence and thickness of the halites has had a major influence on the geometry of the thrust belt and such variations has been used to explain lateral changes in structural style along the belt.

References

{{Reflist Geology of Iran Geology of Iraq Geology of Saudi Arabia Geologic formations of Iran