The Geology of the Dibba Zone its Bounding Contacts and Related Hydrocarbon Prospectivity, United Arab Emirates

The Dibba Zone, extends from the town of Dibba in Oman towards the southwest into the United Arab Emirates. It dies out beyond the present day Hajar Mountain front in a thrust complex in the emirate of Ras Al Khaimah. The lithologies represented are mainly mixed clastics and carbonates belonging to the Middle Jurassic to late Cretaceous aged Sumeini (slope) and Hawasina (basinal) deposits. Tethyan deep ocean sediments derived from the east were accreted onto the Arabian continental margin. To the north, the boundary with the Musandam Peninsula's carbonates is sharp and is marked by the Dibba Fault Zone. To the south there is also a sharp contact with Semail Ophiolites that were obducted above these units as the highest thrust sheet. A more detailed understanding of the structural style and history of this complex area has been enabled by the interpretation of modern 3D seismic, the integration of exploration well data, associated biostratigraphical, sedimentological and structural studies and with detailed mapping of outcrops of the Dibba Zone, the Musandam Peninsula to the north, and with the Semail Ophiolites to the south. Recent exploration wells drilled which targeted structural traps along the frontal thrusts of the Oman Mountains in the UAE have a very complicated structural history. Unravelling their genesis and composition is only allowed by detailed seismic mapping and by integrating focused analytical studies with detailed field mapping of nearby geological outcrops and analogues of similar units. A floor thrust cuts through the Upper Cretaceous Muti Formation separating a mainly autochthonous Arabian Platform from an imbricated, duplexed and tectonically thickened unit that comprises Campanian aged Aruma Group sediments with sandwiched allochthonous slivers of mainly Hawasina basinal deposits. A roof thrust of early Maastrichtian age is onlapped by shallow water deposits of Latest Cretaceous age (the Simsima Formation). The Hawasina deposits are often represented by hard radiolarian rich cherts that are of high acoustic impedance. Occasionally the Arabian Platform carbonates including prospective formations such as the Shuaiba, Kharaib and Lekhwair (the Thamama Group) are incorporated into the frontal para-autochthonous fault slivers and then become hydrocarbon exploration targets. This paper shows a detailed study of geological outcrops of the Dibba Zone and nearby areas. This has allowed for both ground truthing and unravelling of the complex structural history of the Hajar Mountains with specific focus along frontal thrusts. This has aided the interpretation of the stratigraphy of recently drilled exploration wells as well as detailing the remaining prospectivity. The results of this study have helped in the determination of new exploration leads and areas of interest as well as providing a better applied model for geological risk assessment.