Online Journal for E&P Geoscientists

Al Hossani, Khalil I.¹; Elsaid, Mohamed E.^*1; Al Suwaidi, Ahmed S.¹; Warrak, Mohamed ¹
(1) Development, ADMA-OPCO, Abu Dhabi, United Arab Emirates.

The offshore of the United Arab Emirates (U.A.E.) contains eight diapiric islands; Dalma, Zirku, Qarnain, Das, Sir Bani Yas, Arzana, Sir Abu Nuwair and Abu Musa. These islands owe their relief to the diapiric movement of salt which has pierced and deformed the overlying strata. These diapiric islands have similar shapes, stratigraphic sequences, aerial distribution of the identified stratigraphic units and general tectonic framework as following:

1. Infracambrian to Cambrian (Hormuz Group) composed of igneous and metamorphic rocks, salt, anhydrite, carbonate and clastics interbeds. 2. Miocene composed of sandstone, siltstone, shale, carbonate and evaporite interbeds. 3. Pliocene to Recent sediments composed of mixed facies of clastics, carbonates and evaporites.

One of the good examples is Zirku Island. The Island is a pear-shaped of approximately 5 km. long and 2.5 km. wide. A zone of very rugged hills with ridges is located in the centre and NNW with an elevated point of 163 meters.

Zirku Island was formed by the movement of Cambrian (Hormuz) salt that deposited and has moved progressively upward, puncturing through the younger overlying strata to create a dome structure. The surface expressions are composed of evaporites rocks, plus igneous rocks and quartzitic sandstone.

The salt piercement is probably related to the Zagros orogony in the Pliocene to early Pleistocene and has brought in materials to the surface from considerable depths. On the Zirku Island the ‘exotic’ materials are represented by a rugged central region of lower Palaeozoic contorted sandstones and siltstone of the Hormuz series. In the north east of the central core there is a sequence of steeply dipping lavas out-cropping the eastern flank of the ridge. Bordering the central zone is a gypsiferous breccia or mélange apparently formed around the margin of the Hormuz outcrop during emplacement from depth. The older Hormuz material has been eroded and partly incorporated into calcareous sediments formed along the shore of the ‘structural high’, probably in the late Tertiary period