Stratigraphic and tectonic setting of the Rus Formation at Jebel Hafeet, UAE.

The Rus Formation consists of a succession of carbonate rocks deposited in the Southeastern Arabian foreland system during the Paleocene-Ypresian. Throughout the UAE, the Rus Formation is commonly restricted to the subsurface of the Abu Dhabi Emirate territory, with the exception near the western front of the Hajar Mountains close to Al Ain city. At this location, the Rus Formation is exposed and forms the core of the Jebel Hafeet km-scale anticline fold. This large-scale exposure allowed us to study its stratigraphic and tectonic evolution from deposition to the present-day tectonic framework. Lithostratigraphic and facies analyses of the outcropping portion of the Rus Formation at Jebel Hafeet identified a succession of approximately 150 m of limestones and dolostones characterized by three main depositional facies:

• platform facies, characterized by thick to massive carbonate beds with abundant shallow-water bioclasts;
• ramp facies, showing evidence for syn-depositional instability, with mass flows and collapse structures;
• ramp-basin facies, characterized by thin beds with marked downlapping geometries.

Thus, the studied succession forms a complete platform-to-foreland basin transition that is well-exposed along the hinge of the fold structure. The base of the Rus Formation is concealed beneath the widespread quaternary cover, whereas the top of the Rus consists of unconformable stratigraphic contact with the Dammam Formation.

During the Early Cenozoic, the depositional environment of the Rus Formation was probably subjected to far-field stress due to the migration of the foreland depocenter in response to the obduction of the ophiolite slabs onto the Arabian continental margin successions. Structural analyses of deformation features such as faults and folds and geochronological/geochemical analysis of the correlated calcite veins (U-Pb on calcite) within the Rus Formation revealed that compressive tectonics generated the main folding event and drove subsequent exhumation from c. 20 to 2 Ma. Thus, these new data suggest that the deformation and uplift of Jebel Hafeet succession occurred in the context of post-Oligocene tectonics simultaneously with the Zagros collision but were likely developed along a strike-slip system accommodating the push of the Eastern Makran Belt.