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Analysis of Sequence Stratigraphic Models for the Jurassic Cretaceous Sedimentary Fill of the Intrashelf Basins of the Eastern Margin the Arabian Plate


Two critical conceptual sequence stratigraphic models for exploration and production were analyzed with sedimentary computer simulations of the Jurassic and Cretaceous sedimentary fill of the Intrashelf Basins (ISB) of the Eastern margin the Arabian Plate. One tracked the Hanifa Basin fill from Jurassic argillaceous carbonates to evaporites to the Cretaceous carbonates and the other the Aptian/Albian fill of the Bab ISB during a glacially induced sea level low. The Hanifa ISB simulation demonstrated Lower to Middle Jurassic sediments onlapped the uplifted eastern plate margin of the UAE and Oman as carbonates prograded and filled westward. Uplift ended Middle Jurassic accumulation with subaerial and progressive erosion of the Tuwaiq and Dhruma Formations on the eastern plate margin. Margin collapse caused a drowning unconformity. Westward of the platform margin the intra-shelf basin a base-level fall accompanied Arab and Hith evaporites accumulation. In Early Cretaceous times the platform extended to North Oman with deposition of argillaceous hemipelagic carbonates of the Habshan. The lack of evaporites supports a climatic change from the Jurassic arid climate to a Cretaceous humid one. The simulation of the Mid Cretaceous carbonates supports division into Early Aptian and Late Aptian carbonate platform second order supersequences that aggraded and prograded to fill the Bab ISB. An unconformity initiates the sequence with westward prograding lowstand clinoforms onlapping eastward onto the Lower to early Upper Aptian carbonate platform of the SW margin of the Bab ISB. The simulation captures an initial sharp sea-level drop of 35–40 m from the early Upper Aptian shelf break to the topset of the first lowstand clinoform, and the sea-level drop by another 10 m during the progradation of following eight clinoforms. Each progradational pulse of the clinoforms is modeled over 405 k.y. Simulation illustrates the initial sharp sea-level drop of some 40 m followed by continued slow sea-level fall producing lowstand clinoforms prograding towards the ISB. Sedpak, developed at the University of South Carolina assumes clastic transport based on slopes and carbonate production based on water depth. Output geometries display a sequence stratigraphic framework of erosional and depositional surfaces of the simulated section enabling the extension of interpretation of depositional setting and predictions of lithofacies geometries away from well data.