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Tectonic Controls on the Stratigraphic Architecture of the Permo-Triassic Khuff Formation, Eastern Saudi Arabia

Abstract

The Permo-Triassic Khuff Formation was deposited on a broad, low-relief carbonate platform trending northwest-southeast on the passive margin of the Neo-Tethys Ocean. The stratigraphic architecture of Khuff carbonates and their distribution in eastern Saudi Arabia, utilized well data, seismic interpretations, and potential field geophysical data. The Permo-Triassic section in Eastern Saudi Arabia was bordered by the Arabian shield to the west, Hail Arch in the north, and Hadramawt-Sana'a Arch in the south. The region was situated in low to moderate southern latitudes in a regional carbonate platform, where shallow warm water conditions prevailed during the Permo-Triassic. The passive margin is underlain by multi-terrain basement, which experienced differential tectonic subsidence that resulted in the formation of numerous sub-basins. There were three global geological events of great significance during the Permian-Triassic: the largest mass extinction known at the Permo-Triassic boundary; long-term dominance of superanoxia; and the earliest breakup of Pangea. Mud-rich facies were deposited mostly in sub-basins (paleo-lows), whereas grain-rich facies (reservoir) were deposited on the intervening paleotopgraphic highs. Isopach maps and regional composite cross sections across the region, constructed from seismic and calibrated with well data, indicate thickness variations corresponding to irregular basin topography resulted from differential subsidence of basement blocks. Basal Khuff clastics are interpreted to have been deposited in rifted basins, composed of horsts, grabens, and tilted normal fault blocks, imaged on flattened seismic sections that utilized the top of the Khuff as a datum. The rift evolved rapidly into a passive margin. Exploration concepts are being generated as a result of this understanding of tectonic, depositional, and stratigraphic controls of the Khuff Formation.