Characterization of Permian to Triassic Formation Within Ogaden Reservoir Ethiopia, Implication of Source Reservoir Interaction
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2023-06
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Abstract
The Ogaden region is located on the Somali Plateau, in southeast Ethiopia. Originally a clanbased term, the Ogaden is now commonly used for the entire region below about 1,500 m a.s. l., an area of some 350,000 km2 that encompasses most of the Somali Regional State and includes the southwest portion of Oromia. The Northern Ogaden Basin is underlain by Precambrian basement rocks and Phanerozoic rocks consist of Paleozoic – Mesozoic sedimentary rocks and Cenozoic volcanic and cover rocks. The Phanerozoic of northern Ogaden Basin is formed on an exhumed rift-related, NW-to WNW trending basin that formed as a result of the NE-SW extension that began in Paleozoic. The oldest rocks in the basin are represented by the deposition of Paleozoic-Early Jurassic succession, which is made of continental clastic sediments (Wayu Sandstone and Adigrat Sandstone). They are deposited within grabens bounded by NW-trending and northeast-and southwest-dipping normal faults, which are developed above a top-to-northeast detachment fault. They are un conformably overlain by Middle – Late Jurassic sediments comprised of mainly limestone with minor interbeds of shale and marls (Hamanlei, Urandab and Gabredarre Formation) that pass upward into the Garbeharre Formation, which consists of sandstone, mudstone, shale with minor interbeds of limestone at the base of the succession. The climate is hot, arid to semiarid, corresponding to the Ethiopian bereha and kolla climatic zones. Three basic physiographic provinces are recognized: the Genale and Shebele drainage basins and the Eastern Slope and Plains. The two drainage basins include spectacular upstream canyons that witness the vertical movements that have accompanied the succession of rifting events in the Ethiopian Rift, Afar, and the Gulf of Aden. In strong contrast, the Eastern Slopes and Plains is dipping less than 0.4° on average over hundreds of kilometers to the southeast and is mantled by red sands. Several remarkable Oagden landforms are described and analyzed, including volcanic, fluvial, and gravitational features, some having few equivalents in other areas on Earth.
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Source Reservoir Interaction, Triassic Formation, Ogaden Reservoir Ethiopia, Permian