SUBMARINE CANYONS IN THE BELLINGSHAUSEN AND RIISER-LARSEN SEAS AROUND ANTARCTICA

概要

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Submarine canyons in the Bellingshausen and Riiser-Larsen Seas are compared. It is pointed out that the canyons in the Bellingshausen Sea are so incorporated to build up a deep-sea fan or an apron slope, that they develop dominantly on an upper fan at the upper continental rise and disappear apparently on a lower fan at the lower continental rise. The deep-sea fan or the apron slope was formed by supply of the great amount of sediments from the shelf area due probably to grounded ice sheets on the continental margin. On the contrary, the canyons in the Riiser-Larsen Sea have a large-scale entrenching throughout their course and construct a canyon-deep sea channel complex. This is caused by thermal cooling effect of lithosphere to deepen the old ocean basin. Buried canyons observed on the seismic profiles indicate that activation of the canyon formation was triggered by advancement of the Antarctic ice sheet toward the outer edge of the continental shelf sometime between 4 and 7 Ma BP. The meltwater and eroded sediments by the extended grounded ice sheet provided a potential source for turbidity currents and debris flows into the canyons, thus causing rigorous development of the canyon.
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