Bio- and isotope stratigraphy of the Lower/Middle Eocene section at Gebel Hafit area, United Arab Emirates

The nodular limestone exposed at the basal part of the Gebel Hafit (United Arab Emirates) represents an intraformational truncation Surface covered by 6m of "lowstand" conglomeratic limestone with carbonatic nodules of various sizes. It represents the basal part of the middle Eocene Dammam Formation and is presented in this study as a new Member (Mibazara Member). The Mibazara Member overlies the Lower Eocene Rus Formation and demarcates the Rus/Dammarn boundary to the lower/middle Eocene contact. The microfacies investigations of the studied succession indicate a gently dipping carbonate platform in the area of the Gulf region during that time. Six microfacies units were distinguished from the study area. Two facies units from the basal part of the Rus Formation (Lower Member) and the basal part of the Dammam Formation (Mibazara Mb.) are composed of coarsening upward Nummulitic limestones. Three facies units from the upper part of the Rus Formation (Upper Member) are composed of fining upward Nummulitic limestones, with marl intercalations probably related to global sea level rises. The oxygen 18 and carbon 13 isotopes of the bulk samples are cyclic and match the previous six facies units. The global cooling event "B" of the early Middle Eocene (SHACKLETON 1986) or Early Eocene Climatic Optimum (EECO, BOHATY & ZACHOS 2003) is reflected by a positive shift in delta(18)O data and is represented by the first marl unit of the upper part of the studied section. The NP13/NP14 boundary is delineated in the upper part of the marl/carbonate succession of the Rus Formation. The evaluated time of the cooling event from the studied delta(18)O and nannoplankton is 0.5 Ma earlier than other correlated core sites of South Atlantic which could be related to the effects of increasing cooling by the uplift of the Himalayas.