Geomorphology of the Ross Sea and adjacent oceanic provinces

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The shelf morphology of the Ross Sea is controlled by tectonism resulting from continental rifting and recurrent faulting accented by glacial erosion. Volcanism related to continental break-up or a hot spot is also a significant factor. The continental slope and rise are incised by numerous submarine canyons which, during times of lower sea level, must have been an important conduit transporting sediment from the shelf to the ocean basin. The ocean basin is dominated by the mid-ocean ridge system. The western part (Vincennes Plateau) is a simple elevated arch with no fracture zone. Its morphology is probably due to the proximity of a hot spot. The ridge from 161° E to 170° W is highly complex with numerous large fracture zones. East of 175° W, the ridge is a typical arch with occasional NW—SE fracture zones.Plate reconstruction models for the area become increasingly difficult with age. There is general agreement that eastern New Zealand separated from West Antarctica approximately 80 m.y.B.P. The Tasman Sea opened at about the same time, separating the Lord Howe Rise and western New Zealand from Australia; however, this movement ceased approximately 60 m.y.B.P., and coincides with the separation of Australia and East Antarctica. The faulted nature and poor fit of the Iselin Bank and perhaps South Tasman Rise suggests this area may have acted as an independent platelet during the separation of Australia and Antarctica. The complex Pacific—Antarctica fracture zones now represent shear motion between Indian—Antarctic spreading and Pacific—Antarctic spreading.