Early to Mid-Triassic fault reactivation in eastern Saudi Arabia is shown using three-dimensional seismic reflection data. The geometry and timing of these fault systems are constrained by the interpretation of reflectors in the Khuff, Sudair and Jilh formations, tied to deep wells. The faults terminate upwards in the Sudair and Jilh formations, dating this event to 250–240 Ma. The fault systems generally trend north–south to NE–SW and in places consist of isolated systems several hundred kilometres long, whereas other areas show pervasive, evenly spaced faults 5–10 km apart. The north–south-trending structures control Triassic isopach variations, whereas the NE–SW-trending systems contain localized highs and lows in relay zones, indicating strike-slip kinematics with the maximum horizontal stress, restored for post-Triassic plate rotation, trending 030–210°. These fault systems link Lower Paleozoic source rocks with the Khuff Formation reservoirs, often retaining topseal integrity due to the presence of upper fault tips in the sealing units. The faults are interpreted to be reactivations of Precambrian basement lineaments. The fault timing correlates with a cusp in the African–Arabian plate motion path relative to Tethyan terranes. These local- and plate-scale observations can be explained by Early to Mid-Triassic dextral shear along the Arabian continental margin.

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