RITSCHER CANYON OFF BREID BAY, DRONNING MAUD LAND, EAST ANTARCTICA

• Main Authors: カガミ ヒデオ, Hideo KAGAMI
• Format: Report
• Language: English
• Published: Faculty of Science, Josai University 1994
• Subjects: Antarctic; East Antarctica; Dronning Maud Land; West Antarctica; Bellingshausen Sea; Weddell; Riiser-Larsen; Riiser-Larsen Sea; Breid Bay; Ritscher Canyon; Antarc*; Antarctica
• Online Access: https://nipr.repo.nii.ac.jp/?action=repository_uri&item_id=2761; http://id.nii.ac.jp/1291/00002761/; https://nipr.repo.nii.ac.jp/?action=repository_action_common_download&item_id=2761&item_no=1&attribute_id=18&file_no=1

Through newly compiled bathymetry, canyons in the Riiser-Larsen Sea show large-scale channel incision throughout their course. This is caused by decreased delivery of sediments during deposition of the R1 sequence, and by the thermal cooling effect of the lithosphere, which deepens the old ocean basin, producing baselevel change. In contrast, canyons in the Bellingshausen Sea develop predominantly on fan complexes on the upper continental rise and fade apparently on the lower continental rise. After compilation of a new bathymetric map, it is found that tributaries of Ritscher Canyon change their course sharply eastward at latitude 68°S, which indicates the presence of a strong eastward current at the mouths of tributaries during deposition of the R2 sequence. It is also found that the Ritscher deep-sea fan develops at the base of the upper continental rise. This margin shows a steeper gradient (>0.0075) on the upper continental rise, due to enormous delivery of sediments from the continent during deposition of the R2 sequence. The gradient of 0.0075 is found to be a critical value for the continental margin, at which a hydrodynamic jump takes place from turbulent flow to laminar flow, resulting in discharge of sediment load to form a deep-sea fan. The margin distributes from Dronning Maud Land to at least the Weddell Fan area of East Antarctica, and here is called the East Antarctic margin. This value corresponds roughly to the boundary between the continental slope and the upper continental rise in the Bellingshausen margin, West Antarctica, which is similar to that of the Atlantic margin; thus, it belongs to the Atlantic margin type.