Stratigraphic Traps Generation in Abu Dhabi as a Consequence of Ensuing Late Cretaceous Plate Collision and Obduction at the Eastern Arabian Plate Margin

Abstract

Late Cretaceous plate collision and subsequent ophiolite emplacement at the eastern margin of the Arabian Plate led to compressional events, responsible for the formation of the structural traps of the giant fields onshore Abu Dhabi. In addition, the onset of this structuration during the Turonian caused the configuration of some hence-to-forth overlooked features (pinch-outs and siliciclastic sand deposits). The objective of the present work is to analyze the origin and distribution of these geometries and their potential to constitute stratigraphic traps. To understand the genesis and the distribution of these geometries which formed during the Late Cretaceous, we used a combination of large scale regional stratigraphic well correlations and seismic lines interpretation, together with age dating, core description, and well data information. The methodology consisted in using this data for detailed mapping of relevant time stratigraphic intervals, placing the mapped architecture in the context of the global eustatic sea levels and major geodynamic events of the Arabian Plate. The ensuing plate collision during the Turonian in eastern plate margin was felt hundreds of kilometers into the plate over Abu Dhabi area. Buckling and uplifting created paleo-relief which caused exposure and erosion of Wasia Group sediments in northern and eastern areas of Abu Dhabi Emirate. This led to the configuration of some overlooked stratigraphic features: eroded rims and lateral facies change against structural dip (Mishrif Formation); onlap pinch-outs onto flanks of major structures (Ruwaydhah Formations) and the deposition of siliciclastic sand deposits of the Tuwayil Formation. The features follow low relief areas along contemporaneous synclines in onshore Abu Dhabi and salt withdrawal synclines in offshore Abu Dhabi. With further advance of the obducting ophiolites, a foredeep developed leading to drowning of the previously exposed structures. Shales and interbedded limestones of the Laffan Formation were unconformably deposited over the eroded Wasia Group during the Coniacian transgression associated with the generation of this foredeep. They are now forming an extensive regional seal for these deposits forming potentially stratigraphic traps. We postulate that the rejuvenation of the Shilaif intrashelf basin during the Late Turonian and the deposition of the (Ruwaydhah Formation) was aborted at its early stages by periods of uplift, erosion and their successive erosional unconformities, features that are confirmed on the crest of several eastern area structures. This provided the context for the generation of pinch-out geometries that constitute potential stratigraphic traps downdip of major structures in Abu Dhabi. Very little has been published about the outline and architecture of these stratigraphic traps in Abu Dhabi and the detailed circumstances that led to their genesis, topics that are comprehensively analyzed in the present work.