南大洋の形成

• Main Authors: 佐藤, 暢, 野木, 義史, 藤井, 昌和, 佐藤, 太一
• Format: Article in Journal/Newspaper
• Language: Japanese
• Published: 低温科学第76巻編集委員会
• Subjects: プレートテクトニクス; ゴンドワナ; 大陸分裂; プルーム; plate tectonics; Gondwana; continental break-up; plume activity; 450; Drake Passage; Southern Ocean; Antarc*; Antarctica
• Online Access: http://hdl.handle.net/2115/70338; https://doi.org/10.14943/lowtemsci.76.243

南大洋の形成過程は，ゴンドワナの分裂過程と言い換えることができる．本稿の目的はゴンドワナの分裂過程をレビューすることで，南大洋の形成についての理解を深めることである．大陸分裂は，プルームの上昇によって始まる場合とプレート運動によってリフティングが生じて始まる場合がある．南大洋の形成と直接の関係がある東ゴンドワナの分裂の際には，大陸分裂初期過程のリフティングが先行し，プルームによる活動がそれに続いたようである．約3000 万年前に南極大陸が孤立することによって南大洋は現在と同じセッティングになった．タスマニアゲートウェイが約3400 万年前に形成され，ドレイク海峡は約2700 万年前に形成されたと推定されている． The Southern Ocean had been formed by the continental break-up of the Gondwana. In this paper, we review the break-up history of the Gondwana to understand the Southern Ocean formation in terms of geology, geophysics, and tectonics. Two cases of continental break-up are proposed: continental break-up followed by plume upwelling or ascending of deep hot materials due to thinning continental lithosphere during continental break-up. In the cases for break-up of the East Gondwana, with which the Southern Ocean was directly formed, it is likely that deep hot materials arose after rifting of the continental lithosphere. The distribution of continent and ocean in the Southern Ocean had completed at around 30 Ma when Antarctica had been isolated near the present location. Tasmanian gateway between Australia and Antarctica had formed at approximately 34 million years ago, and the Drake Passage between South America and Antarctica had formed at approximately 27 million years ago.