The sea floor in the New Zealand region is one of high relief made up of major ridges, basins, and troughs. The continental slope passes directly down to large abyssal basins only over a limited portion of its total extent. A morphological and structural unit, the New Zealand Plateau is recognised centring on New Zealand and limited by the mid-slope isobaths, in the north at 1,250 fm and elsewhere at 1,500 fm. Deposition of land-derived elastic sediments in abyssal areas is at present limited. Elsewhere than in Hikurangi Trench it is masked by sedimentation of abundantly produced foraminiferal tests. The trench is suggested as the only present site of accumulation of geosynclinal sediments in the region. The major depressions connecting the upper slope and shelf with the abyssal ocean floor are figured. Sediment-flow channels, that in the glacial stages of the Pleistocene could have transported large volumes of sediment, are located in the axes of Bounty Trough and Hikurangi Trench. |
