Submarine canyons on the north of Chiwei Island:influenced by recent extension of the southern Okinawa Trough

摘要

Based on new multibeam bathymetric data and about 300 km long single seismic profiles,three topographic units were identified:the canyons,fractural valley and submarine terrace on the north of Chiwei Island where is a structural transition zone between the southern trough and the middle trough.The Chiwei Canyon and the North Chiwei Canyon are two of the largest canyons in the East China Sea (ECS) slope.Topographic features and architectures of them are described.The study shows that both of them are originated along faults.The evolution and spatial distribution of topographic units in the study area are controlled mainly by three groups of faults which were formed and reactive in the recent extensional phase of Okinawa Trough.The Chiwei Canyon was initia-ted during the middle Pleistocene and guided by F4 that is a N-S trending fault on the slope and F1,a large NW-SE trending fault on the trough.The pathway migration from the remnant channel to the present one of Chiwei Canyon is the result of uplift of tilted fault block that is coupled to the recent extension movements of the southern trough.The submarine terrace is detached from the ECS slope by the NEE-trending fault.The North Chiwei Canyon,developing during the late Pleistocene,is guided by F5,a N-S trending fault,diverted and blocked by the submarine terrace.