Geological and geophysical survey in the Bellingshausen Basin, off Antarctica

• Main Authors: 木村 勝弘, Katsuhiro Kimura
• Format: Report
• Language: English
• Published: 石油公団石油開発技術センター 1982
• Subjects: 550.34:551.2; Antarctic; The Antarctic; West Antarctica; Bellingshausen Basin; Antarc*; Antarctica; Ice Sheet
• Online Access: https://nipr.repo.nii.ac.jp/?action=repository_uri&item_id=8303; http://id.nii.ac.jp/1291/00008303/; https://nipr.repo.nii.ac.jp/?action=repository_action_common_download&item_id=8303&item_no=1&attribute_id=18&file_no=1

海洋底磁気異常から推定できる古海溝の存在が, 3重合反射法地震探査記録断面で確認できた。また, 海洋基盤上の古海溝下部斜面堆積層, 大陸基盤上の古前弧堆積盆堆積層, 古島弧と古背弧堆積盆堆積層も確認できた。この古海溝-島弧システムは白亜紀以来存在していた。白亜紀∿古第三紀のアンデス火成岩類はこの古システムの背弧火成活動に当たる。海嶺の沈み込みはこの古海溝-島弧システム全体の隆起と加熱を引き起こした。海洋底磁気異常は, この海嶺の沈み込みが南極大陸にそって南西から北東へと順に起こっていったことを示す。この海嶺の沈み込み後, この古海溝-島弧システムは非活動縁辺域に転化した。古海溝と古島弧間では中期中新世になって沈降と堆積が始まった。この沈降は南極大陸氷の進出によるものであろう。全堆積層は古海溝下部斜面堆積層のところで最も厚く, その海側と陸側で薄くなる。 The continental margin in the Bellingshausen Basin off West Antarctica was geologically and geophysically surveyed. The paleo-trench, which has been inferred from the seafloor magnetic anomalies, is found out in the 3-fold seismic reflection profiles. In addition, the paleo-trench-lower-slope-sedimentary-complex on the oceanic basement, sediments of paleo-fore-arc-basin on the continental basement, paleo-island-arc and sediments of paleo-back-arc-basin are recognized. This paleo-trench-arc-system may have existed since Cretaceous time. The Cretaceous to Early Tertiary Andean igneous rocks correspond to this back-arc igneous activity. Ridge subduction caused the uplift and heating of the whole paleo-trench-arc-system. Seafloor magnetic anomalies show that the ridge subduction has progressively occurred in a northeasterly direction along the Antarctic margin. After the ridge subduction, this paleo-trench-arc-system has been transformed into a passive margin. Between the paleo-trench and the paleo-island-arc, subsidence and deposition began in the Middle Miocene. This may be due to advance of ice sheet. Total sediment thickness is the largest in the site of the paleo-trench-lower-slope-sedimentary complex, and decreases both seaward and landward.