Structural style of buried Ediacaran basins in Saudi Arabia on seismic reflection data

Abstract

Several isolated Ediacaran basins subcrop Phanerozoic strata in Saudi Arabia. The structural styles of these subcropping basins are reviewed here based on interpretation of 2D and 3D seismic reflection data and comparison with Arabian Shield outcrops. The basins are distinguished by layered seismic reflectors that are interpreted as sedimentary and volcanic strata. Due to limited well penetrations these packages cannot be directly dated but a relative chronology is established, anchored by constraints from the Arabian Shield and regional studies. Most of the basins are bound by extensional faults and the basin fills show growth architectures and angular unconformities. The bounding faults trend broadly north–south and are interpreted to be late to post-orogenic reactivations of oceanic terrane margins. Based on their structural characteristics in comparison with sub-basins exposed on the shield, the basin fills are correlated with the Ediacaran Jibalah Group, an equivalent of the Omani Nafun Group. These sub-basins experienced inversion and exhumation prior to ongoing volcanism and unconformable deposition of late Ediacaran to earliest Cambrian Kurayshah Group sediments. The Kurayshah Group is disconformably overlain by the widespread Tayma Group siliciclastics. This disconformity correlates to the Angudan Unconformity in Oman. The Kurayshah Group includes a late Ediacaran stratovolcano over 40 km in diameter. In the eastern basins, evaporitic structural styles indicate the presence of Hormuz / Ara evaporites, with local igneous intrusions, that correlate at least in part to the Kurayshah Group. The Tayma Group infills significant accommodation space variations and was affected by ongoing but declining differential subsidence and reactivation of the underlying basin-bounding faults.