Diagenetic aspects of tertiary carbonates west of the Northern Oman Mountains, United Arab Emirates

To the south of Al-Ain, United Arab Emirates (UAE), lies the large mountain of Jebel Hafit. It which consists of foredeep basin sediments, which face the obducted allochthonous formations of neo-Tethys oceanic crust and associated deep marine sediments (i.e., Semail Ophiolites and Hawasina sediments). The foredeep sediments formed during the Early Eocene–Miocene. They are considered to be the main Paleogene marine exposure in Eastern Arabia. They are made up of limestones and marls and constitute four main rock units, namely: Rus, Dammam, Asmari and Fars formations, respectively, from base to top. The Rus (Late Early Eocene) is made up of fossiliferous, dolomitized limestone. The Dammam Formation (Middle to Late Eocene) conformably overlies the Rus Formation and comprises shale, marl, and limestone. The Asmari Formation (Early to Middle Oligocene) conformably overlies the Dammam Formation and is made up of nodular limestone. This is the first in depth study of diagenesis within the Dammam Formation.The petrographic investigation of this work reveals that the original textural and compositional characteristics of the Dammam Formation were modified by cementation, micritization, neomorphism, dolomitization, and, to a lesser extent, dissolution, compaction, dedolomitization, and silicification. Cementation with calcite and, less commonly, dolomite and iron oxides, in addition to dissolution effects, are more evident in the upper part of the Dammam Formation. Silicification and dolomitization are also extensive in the upper part of the Dammam Formation.Shallow burial of the Dammam Formation sediments in a partially closed system resulted in their compaction and consequent cementation with calcite. These carbonates display a wide spectra of diagenetic features, reflecting different environments. Micritization and early phases of cementation with calcite (isopachous calcite) likely occurred in a marine phreatic environment. Dolomitization and silicification most likely took place in the marine-meteoric mixing environment. Early phases of dissolution, cementation neomorphism, and dedolomitization also occurred within the phreatic environment.