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The Porcupine Seabight is a deep-water oceanic basin located on the continental margin in the northeastern portion of the Atlantic Ocean. It can be found in the southwestern offshore portion of Ireland and is part of a series of interconnected basins linked to a failed rift structure associated with the opening of the Northern Atlantic Ocean. The basin extends in a North-South direction and was formed during numerous subsidence and rifting periods between the Late Carboniferous and Late Cretaceous.〔 It is bordered by the * Goban Spur to the south * Slyne Ridge to the north * Porcupine Bank to the west * Porcupine Abyssal Plain to the southwest Due to subsidence, water depths range from 3000 m in the south near its mouth to 400 m in the north. The Porcupine Basin lies on the Caledonian metamorphic basement and preserves up to 12 km of sedimentary strata from Late Palaeozoic to Quaternary which includes significant hydrocarbon reservoirs.〔 Sediment was likely sourced from the uplifted Calendonian metamorphic rocks of the Porcupine Median Ridge. 〔 The basin lent its name to Operation Seabight, an Irish drug-bust of November 2008. ==Geologic History== The basin was formed during numerous subsidence and rifting periods between the Late Carboniferous and Late Cretaceous.〔 Multiple stages of uplift and subsidence were responsible for sediment input, the formation of accommodation space and the creation of steep basin margins:〔 # Initial rifting occurred in the Triassic, with a series of minor rifting episodes. # Main rifting developed in the Mid to Late Jurassic, and lasted around 20 to 30 million years. # Major thermal subsidence, or uplift. # Minor rifting in the Early Cretaceous. # Irregular subsidence in the Tertiary, from possible lithospheric stretching by rifting or mantle plume.〔 Extreme stretching of the lithosphere has been documented in the Porcupine Basin. This stretching is especially found in the southern part of the basin as a result of rotation of the Porcupine Ridge away from the Irish shelf. * Crustal thickness in this area was found to be 7.5 ± 2.5 km. * Lithospheric stretching of β>6. 〔 〔 There are a number of unconformities found within the basin. Folding, uplift and related erosion during the Jurassic to Cretaceous produced the regional Base Cretaceous Unconformity in the northern section. Accommodation for the Early Cretaceous succession was not only generated by thermal subsidence following the Late Jurassic crustal extension, but also by compressional deformation during the latest Jurassic–earliest Cretaceous. Inverted structures found in the basin formed may be related to the initial closure of the Alpine Tethys. The latest Jurassic to Cretaceous uplift, inversion and erosion observed in many basins in Western Europe may also be associated with this event. 〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Porcupine Seabight」の詳細全文を読む スポンサード リンク
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